1. health and fitness
2. disease
3. arthritis

54
C H A P T E R
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Patella Fractures and
Extensor Mechanism Injuries
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Michael T. Archdeacon, M.D.
Roy W. Sanders, M.D.
HISTORICAL BACKGROUND
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Before the beginning of the 20th century, treatment of
patella fractures was extremely controversial. Nonoperative
methods, usually extension splinting and rest, were most
commonly used. Results were poor, bony union was rare,
and permanent disability was expected.31 As improvements in surgical asepsis occurred, two operative solutions
to the problem emerged: arthrotomy with open wiring and
patellectomy. Heineck reviewed 1100 patella fractures and
advised operative treatment over extension splinting for
the following reasons: improved fracture reduction, maintenance of reduction until union, reestablishment of soft
tissue continuity, and restoration of the functional integrity
of the knee joint.48 Open reduction and wire fixation
subsequently became the treatment of choice for patella
fractures.
Although reduction of simple transverse fractures was
made possible by an open procedure, stable fixation
remained difficult. Various materials were tried, including silver, aluminum, and copper wire; chromic suture;
kangaroo tendon; cancellous bone pegs; Achilles tendon;
and fascial strips.50 In 1936, Blodgett and Fairchild
reported 35 patella fractures treated with open reduction and wire suture; less than 50% had good results.10 They then reported on the use of partial or, in
certain cases, total excision of the patella for fractures
and described excellent clinical results.10 A year earlier,
Thompson also recommended partial excision of the
patella.100 In the same year as Blodgett and Fairchild’s
study, Brooke published a revolutionary paper on the
treatment of patella fractures by total excision.16 Quoting embryologic data to support the vestigial nature of
the patella, his functional studies showed that postpatellectomy limbs were stronger than their normal counterparts.
Based on these studies, patellectomy gained significant
popularity.31, 40, 44, 45, 50
This initial enthusiasm was tempered by many experimental and long-term clinical studies that disproved
the benefits of patellectomy as routine treatment of fractures of this bone.* Cohn27 and Bruce and Walmsley18
studied patellectomized rabbits and found degenerative
changes on the femoral condyles. They suggested that
this complication could occur in humans as well. Haxton
and others presented biomechanical evidence that the
patella served a necessary purpose in the extensor mechanism.30, 47, 58, 67, 105, 109 In long-term clinical studies evaluating patients after total patellectomy, variable results
were also found.30, 35, 56, 70, 76, 99, 110, 112 These studies
revealed poor patient satisfaction, decreased quadriceps
power, prolonged recovery time, and significant changes in
activities of daily living.35, 89, 99, 112
Treatment of patella fractures with the anterior tension
band principle was first reported in the 1950s.79 This
technique was subsequently advocated by the Arbeitsgemeinschaft fu¨r Osteosynthesefragen/Association for the
Study of Internal Fixation (AO/ASIF) group as the treatment of choice for transverse patellar fractures.79 Weber
and colleagues compared the tension band principle with
cerclage and interosseous wire suture in cadavers and
found that modified anterior tension band wiring with
retinacular repair gave the most stable fixation of a transversely fractured patella.108 Additionally, this construct was
the only one that allowed early active range of motion of
the knee.108 Other authors subsequently confirmed this
fact clinically.11, 12, 54, 64
At present, three forms of operative treatment survive:
various types of fixation, usually with tension band wiring;
partial patellectomy; and total patellectomy. Definitive
indications for each procedure are related to the type of
*See references 18, 27, 30, 35, 47, 56, 58, 67, 70, 76, 89, 99, 105,
109, 110, 112.
2013
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2014
SECTION V • Lower Extremity
fracture encountered, and good results can be expected
with proper treatment.
ANATOMY
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Skeletal Anatomy
The patella lies deep to the fascia lata and the tendinous
fibers of the rectus femoris (Fig. 54–1A). It is flat and
roughly ovoid and comes to a rounded point, known as
the apex, on its anteroinferior margin. Its proximal part is
called the basis (see Fig. 54–1B).
Wiberg classified patellas into three types based on the
size of the medial and lateral facets.111 In type I, the medial
and lateral facets are approximately equal, whereas in types
II and III, the medial facets are progressively smaller than
the lateral. Baumgartl described a fourth type, the ‘‘Ja¨ gerhut
patella,’’ in which the medial facet is lacking altogether.5
These facets have importance with respect to the functional
anatomy of the patellofemoral joint (see the section Extensor Apparatus Biomechanics).
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Presentation
Soft Tissue Anatomy
QUADRICEPS MECHANISM
The quadriceps muscle complex is composed of four
separate muscles: the rectus femoris, vastus medialis,
vastus lateralis, and vastus intermedius (Fig. 54–2). Classically, the quadriceps tendon is described as trilaminar in
structure; it inserts onto the patella with the rectus femoris
superficial, the vastus medialis and lateralis in the middle,
and the vastus intermedius deep.67 The actual arrangement
is more complex because of blending of the tendons as they
insert on the patella.86
The rectus femoris is a long fusiform muscle that
assumes the central and superficial position in the quadriceps structure.86 The fibers angle 7° to 10° medially in the
frontal plane relative to the shaft of the femur.67
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Presentation
A
B
FIGURE 54–1. A, Superficial aspect of the patella, with extensive soft
tissue attachments indicated by roughened surface. B, Articular surface of
the patella (see text). Note the extra-articular distal pole occupying a
significant portion of the bone’s length. The articular surface is divided
into seven facets by several ridges (see Fig. 54–1A). A major vertical ridge
separates the medial from the lateral facets, and a second vertical ridge
near the medial border isolates a narrow strip known as the odd facet. In
addition, two transverse ridges create superior, intermediate, and inferior
facets (Bostro¨ m, 1972; Reider et al., 1981).
FIGURE 54–2. Soft tissue attachments of the patella. Major components of
the extensor mechanism include the quadriceps tendon proximally and
the patellar ligament (tendon) distally. The medial and lateral retinacula
help position the patella and can provide active knee extension if they
remain intact after a patella fracture without significant displacement.
The vastus medialis divides into two parts. The more
proximal fibers are known as the vastus medialis longus
and enter the patella at an angle of 15° to 18°. The more
distal fibers, the vastus medialis obliquus, enter the patella
at an angle of 50° to 55°.67 The fibers of each group are
divided by fascia into separate fascicles. Innervation of the
vastus medialis obliquus is by a separate branch of the
femoral nerve.67, 86
The fibers of the vastus lateralis approach the patella at
an angle of approximately 30° and terminate more proximally than do the fibers of the vastus medialis. The most
medial fibers insert into the supralateral edge of the patella,
with the more lateral fibers traveling laterally past the
patella. These fibers contribute to the lateral retinaculum
and, at their lateral extreme, fuse with the iliotibial tract.
The vastus intermedius lies in a plane deep to the other
three elements of the quadriceps. Most of the fibers insert
directly into the superior aspect of the patella. Deep to the
major components of the quadriceps lies the articularis
genus. This muscle is highly variable in occurrence and
arises from the anterior aspect of the supracondylar por-
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CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
tion of the femur. It inserts on the joint capsule at the
suprapatellar pouch.
PATELLAR RETINACULUM
The deep investing fascial layer of the thigh is known as the
fascia lata. As it spreads over the anterior surface of the
knee, its medial and lateral extensions combine with
aponeurotic fibers from both the vastus medialis and the
vastus lateralis to form the patellar retinaculum, which
inserts directly into the proximal part of the tibia (see Fig.
52–2). The patellofemoral ligaments—deep transverse fibers that are palpable thickenings of the joint capsule
connecting the patella with the femoral epicondyles—
complete the retinaculum.13, 86 In addition, the lateral
aspect of the vastus lateralis and the iliotibial tract both
contribute to the thicker lateral patellar retinaculum.
Together, the patellar retinaculum and the iliotibial band
serve as ‘‘the auxiliary extensors of the knee.’’13
PATELLAR TENDON
2015
ARTERIAL BLOOD SUPPLY
The anterior surface of the patella is covered with an
extraosseous arterial ring derived mainly from branches of
the geniculate arteries28 (Fig. 54–3). The intraosseous
blood supply of the patella is supplied by two systems of
vessels, both derived from this extraosseous vascular ring:
the midpatellar vessels, which penetrate the middle third of
the anterior surface of the patella, and the polar vessels,
which enter the patella at its apex.3, 87
The patellar tendon receives its blood supply from two
sources. The infrapatellar fat pad supplies the deep surface
of the patellar tendon with contributions from the inferior
medial and inferior lateral geniculate arteries. The anterior
or superficial surface of the tendon is supplied by the
retinaculum, which receives its supply from the inferior
medial geniculate artery and the recurrent tibial artery.3
EXTENSOR APPARATUS
BIOMECHANICS
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Derived primarily from fibers of the rectus femoris, the
patellar tendon is flat and strong and inserts onto the tibial
tubercle. Its average length is slightly less than 5 cm. The
fascial expansions of the iliotibial tract and the patellar
retinaculum blend into the patellar tendon as it inserts onto
the anterior surface of the tibia.
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Presentation
FIGURE 54–3. Blood supply of the patella. Note the extraosseous arterial
anastomotic ring, which receives inflow from branches of each of the
genicular arteries. (From Scapinelli, R. J Bone Joint Surg Br 49:563–570,
1967.)
The principal function of the extensor mechanism of the
knee in humans is to maintain the erect position. Ambulation, rising from a chair, and ascending or descending
stairs are examples of this ability to overcome gravity.
The biomechanical principles necessary for these actions
should be understood to treat extensor mechanism injuries
rationally.
A moment is a force that produces rotation about an
axis. It is equal to the product of a force and the
perpendicular distance from the line of action of that force
to the axis of rotation. This perpendicular distance is the
moment arm.91 The force necessary for knee extension
(torque) is directly dependent on the perpendicular distance between the patellar tendon and the knee flexion axis
(moment arm)58 (Fig. 54–4A).
Twice as much torque is needed to extend the knee the
final 15° as to bring it from a fully flexed position to 15°.67
To do so, the knee requires a moment arm that increases
during extension so that it can maintain a constant level of
torque. The patella provides this mechanical advantage by
two separate mechanisms: linking and displacement.58
As the knee begins extension from the fully flexed
position, the patella functions primarily as a link between
the quadriceps and the patellar tendon. This linking
function allows for generation of torque from the quadriceps muscle to the tibia.58 Maximal forces across the
quadriceps tendon have been recorded at 3200 N, whereas
those across the patellar tendon are 2800 N.52 These values
are between four and five times the standard body weight
of 700 N. For young, physically trained men, these forces
can reach up to 6000 N.52
Typically, the linking function occurs in the more flexed
positions. At 135° of flexion, the patella slips into the
intercondylar notch. The patellar facets of the femur have
an extensive contact area with both the patella and the
broad posterior surface of the quadriceps tendon. Load
bearing shifts to a combination of the patellofemoral and
the tendofemoral areas, with the latter being the greater of
the two after 90° of flexion.41 Without patellofemoral
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2016
SECTION V • Lower Extremity
A
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Presentation
B
FIGURE 54–4. Mechanical role of the patella. A, The patella increases the
moment arm of the extensor mechanism (i.e., the distance between the
vector of applied force and the knee’s instant center of rotation). B, After
patellectomy, this moment is decreased, and thus extensor force is
effectively diminished. (A, B, Redrawn from Kaufer, H. J Bone Joint Surg
Am 53:1551–1560, 1971.)
contact, the moment arm is small41 (see Fig. 54–4B). From
135° to 45° of flexion, the odd facet engages the femur. It is
the only part of the patella that fails to meet the true
patellar facets of the femur and the only part to articulate
with the true tibial surface of the medial femoral condyle of
the femur.41
From 45° of flexion to full extension, the patella is the
only component of the extensor mechanism that contacts
the femur. It acts to displace the quadriceps tendon–patellar tendon linkage away from the axis of knee rotation. This
action increases the effective moment arm of the quadriceps mechanism and contributes the additional 60% of
torque that is needed to gain the last 15° of knee extension.67 This second action therefore creates a mechanical
advantage analogous to that of a pulley.58, 109
By displacing the tendon away from the axis of rotation, greater excursion of the quadriceps is needed for
a given range of motion.109 Theoretically, when performing a patellectomy, a quadriceps-shortening or tubercleelevating procedure may be performed to take this requirement into account.
of the wound, if any, and the presence of any associated
injuries.
The history usually describes a fall from a height, a near
fall, a direct blow to the patella, or a combination of these
mechanisms. Correlation with the mechanism of injury
allows the physician to anticipate the fracture pattern. If
the patient has an open wound, the history should include
questions regarding the location of the accident (e.g., at
home, in the water, on a farm).
The physical examination should include an evaluation of the skin to look for contusions, abrasions, blisters
(if treatment has been delayed), and the presence of an
open fracture or an open-joint injury. In patients with
a displaced patella fracture, physical examination will
reveal a visible or palpable defect between the fragments. Significant hemarthrosis usually develops secondary to the fracture. If a palpable bony defect is present
with little or no effusion, a large retinacular tear should be
expected.
Knee extension is then evaluated. A tense hemarthrosis will make this part of the examination extremely
painful for the patient. Arthrocentesis with injection of
lidocaine or bupivacaine into the joint is often helpful. The
patient’s ability to extend the knee does not rule out a
patella fracture and may simply mean that the patellar
retinaculum is intact. An inability to extend the knee,
however, suggests a discontinuity in the extensor mechanism. With a patellar fracture, such inability implies a tear
of both the medial and the lateral quadriceps expansion.13, 73, 92
Occasionally, a laceration may be noted in proximity to
a patella fracture. It may represent an open fracture or
an open-joint injury. Because both are surgical emergencies, it is imperative to diagnose these injuries early.
A simple means of evaluation is the saline load test.
A large-bore needle (18 gauge or higher) and a 50-mL
syringe are used to perform joint aspiration. A significant amount of bloody fluid may be removed, usually
resulting in relief of pain. The needle is left in place while
the syringe is removed and filled with saline solution,
which is then injected into the knee joint. Any communication between the fracture or joint and the outside
environment will become obvious if the saline solution
exits the wound.
After the history and physical examination, radiographic evaluation is performed. Once a diagnosis is made,
the knee is splinted in a position of comfort (usually slight
flexion), iced, and elevated. If the patient requires immediate transfer to the operating room or intensive care unit,
portable radiographs will suffice.
DIAGNOSIS
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History and Physical Examination
Radiographic Evaluation
Fractures of the patella are diagnosed by obtaining a
history of the injury, performing a thorough physical
examination, and acquiring the appropriate radiographic
studies. Completion of these investigations should result
in a final diagnosis that includes the fracture type, the
presence or absence of retinacular disruption, a description
Radiographic evaluation of the patella includes standard and specialized radiographic techniques, tomography,
computed tomography (CT), bone scanning, and magnetic
resonance imaging (MRI). When time permits, standard
radiographic evaluation of the uninvolved knee should be
obtained. Such imaging affords the physician a comparison
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
view for evaluation and assists in any preoperative planning that might be necessary.
STANDARD VIEWS
Anteroposterior
The normal anteroposterior (AP) radiograph is taken with
the patient standing, but this position is impossible for a
patient with an acute fracture. Instead, the film must be
taken with the cassette underneath the knee of a supine
patient. The extremity should be aligned so that the patella
points straight up. Such alignment is especially important
in a patient with an ipsilateral femoral shaft fracture. If the
patient has a large hemarthrosis creating moderate knee
flexion, the x-ray beam must be angled accordingly. Because of the possibility of concomitant occult ipsilateral leg
2017
injuries, the largest cassette possible (14 × 17 inches)
should be used.
Evaluation of the AP radiograph requires analysis of
several factors. Patella position should be assessed; the
patella should lie in the midline of the femoral sulcus. In
addition, patellar height should be examined; the inferior
pole of the patella is normally located just above a line
drawn across the distal profile of the femoral condyles (Fig.
54–5A).
At times mistaken for a patellar fracture, a bipartite or
tripartite patella is a developmental residuum from a
variation in which the patella arises from two or more
ossification centers that fail to fuse (Fig. 54–6). It is usually
a bilateral finding. The most common type is a bipartite
patella, in which a bony mass is located in the upper outer
quadrant of the patella. It is separated from the main
patellar mass by opposing smooth bony surfaces. The
A
FIGURE 54–5. Radiographic indicators of an abnormal patellotibial relationship. An excessive distance between the distal
pole of the patella and the tibial tubercle may represent
disruption of the patellar ligament or chronic patella alta.
A, On the anteroposterior view, the distal pole of the patella
lies no more than 20 mm above the plane of the femoral
condyles. B, When the knee is flexed 90°, a lateral radiograph
should show that the proximal pole of the patella lies posterior
to the anterior surface of the femoral shaft. C, On a lateral
radiograph, the length of the patellar ligament (from the distal
pole of the patella to the tibial tubercle) approximates that of
the patella. If the patella-to-patellar ligament ratio is less than
0.8, the patella is excessively high. D, Blumensaat’s line, the
plane of the residual distal femoral physeal scar, normally
projects near the distal pole of the patella (see Fig. 54–7).
(A–D, Redrawn from Resnick, D.; Niwayama, G. Diagnosis
of Bone and Joint Disorders, 2nd ed. Philadelphia, W.B.
Saunders, 1988.)
B
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D
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Presentation
2018
SECTION V • Lower Extremity
Tangential
Tangential or axial (sunrise, sunset, or skyline) views of the
patella are primarily used in the analysis of patellofemoral
disorders (Fig. 54–8). In fractures of the patella, these
studies aid the surgeon in diagnosis of longitudinal (i.e.,
marginal or vertical) fractures and osteochondral defects.
The three most common views are those of Hughston,
Laurin, and Merchant.21, 74 Although all give approximately the same information with respect to patellofemoral
congruence, the views of Hughston and Laurin are impractical in a trauma setting. The former requires that the
patient be prone, whereas the latter requires patient participation.
Merchant and associates in 1974 described a method of
obtaining an axial view of the patella74 (see Fig. 54–8A).
The patient is placed supine on the x-ray table with the
knees flexed 45° over the end. The knees are elevated
slightly to keep the femurs horizontal and parallel with the
table surface. An x-ray beam is angled 30° from the
horizontal. The cassette is then placed about 1 ft below
the knees and perpendicular to the x-ray beam. This
method is simple, easily reproducible by x-ray technicians,
and able to obtain accurate radiographs in a patient with a
painful, partially flexed knee secondary to hemarthrosis
(see Fig. 54–8B).
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Presentation
FIGURE 54–6. Radiograph of a bipartite patella demonstrating the
characteristic proximal lateral ossification center with a curved, welldemarcated lucent zone of separation.
condition is generally asymptomatic and requires no treatment, but it can cause confusion when treating patients
with a history of injury to the knee area.73 In such cases, a
radiograph of the opposite patella should be obtained.
Invariably, a similar pattern will be found, thus making the
diagnosis. A true unilateral bipartite patella is very rare and
may represent an old marginal patella fracture.32
Lateral
Although a lateral radiograph is easy to obtain, attention to
detail is necessary because rotation of the limb will negate
the benefits of this view. The proximal end of the tibia must
be seen so that rupture or avulsion of the patellar ligament
can be excluded (Fig. 54–7). This view of the knee will
portray a transverse or comminuted patellar fracture rather
dramatically. Unfortunately, however, it may prevent discovery of more subtle findings.
With the knee flexed 90°, the proximal patellar pole
normally lies posterior to the anterior surface of the femur;
with a ruptured patellar tendon, the proximal part of the
patella rests anterior to the anterior surface of the femoral
shaft (see Fig. 54–5B). The most reliable means of assessing
patellar height is the method of Insall and co-workers,21, 55
which involves determination of the ratio of the greatest
diagonal patella length to patellar tendon length. In a
normal subject, this ratio is 1.0. A ratio less than 1.0
suggests a high-riding patella (patella alta) or rupture of the
patellar tendon. Up to 20% variance is normal (see Fig.
54–5C). Blumensaat’s line, the plane of the residual distal
femoral physeal scar, normally projects near the distal pole
of the patella (see Fig. 54–5D).
TOMOGRAPHY
The principal use of tomography in the evaluation of bony
injuries about the knee is in the detection of occult
fractures. Apple and associates recommended tomography
over bone scanning in these cases, especially for stress
fractures and in elderly patients with osteopenia and
hemarthrosis.2 In their series, routine radiographs were
negative in all cases; 71% of the fractures were identified
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Presentation
FIGURE 54–7. Lateral radiograph of a normal patella. (From Resnick, D.;
Niwayama, G. Diagnosis of Bone and Joint Disorders, 2nd ed.
Philadelphia, W.B. Saunders, 1988.)
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
2019
Camera
Nose
X-ray plate
FIGURE 54–8. A, A Merchant tangential view of the patella
is made with the knee flexed 45° and the radiograph
exposed as shown (see text). B, A skyline radiograph
exposed in this fashion demonstrates the patellofemoral
relationship, which may be made incongruent by quadriceps contraction. The image on the left is normal; that on
the right shows lateral subluxation. (B, From Resnick, D.;
Niwayama, G. Diagnosis of Bone and Joint Disorders, 2nd
ed. Philadelphia, W.B. Saunders, 1988.)
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A
with tomography versus only 30% with bone scans.2
Tomography may also be of benefit in the evaluation of
patellar nonunion or malunion.107
Although theoretically of benefit to the diagnostician,
CT scanning is rarely used for evaluation of an isolated
patella fracture. It is generally performed as an incidental
study during the evaluation of distal femoral or proximal
tibial fractures. The information presented rarely adds to
that obtained with more conventional techniques. CT may
aid the surgeon in evaluation of articular incongruity in
cases of nonunion, malunion, and patellofemoral alignment disorders (Fig. 54–9).
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Presentation
FIGURE 54–9. Computed tomographic scan of a fractured patella. Note
the extent of comminution, as well as the secondary sagittal fracture and
the resulting articular incongruity.
Presentation
BONE SCANNING
Scintigraphic examinations with technetium-labeled phosphate compounds are helpful in the diagnosis of stress
fractures, although our preference would be to obtain plain
tomograms. A bone scan may also be useful with indiumlabeled leukocytes or gallium scanning for the assessment
of patellar osteomyelitis.
MAGNETIC RESONANCE IMAGING
MRI has become increasingly useful in the early diagnosis
of extensor mechanism injuries. A normal quadriceps
tendon has a laminated appearance on MRI studies,
whereas the patellar tendon has a homogeneous low signal
intensity. The normal patella has the signal intensity of
cancellous and cortical bone.115
Injuries of all types can produce hemorrhage and
edema, which cause increased signal intensity on T2weighted images. Patella fractures and avulsions of the
tibial tubercle do not generally require MRI evaluation but
will result in changes in marrow signal intensity.115
Complete rupture of the quadriceps tendon is well
demonstrated by MRI, and transection of all layers of the
tendon is diagnostic of a complete rupture. In the more
unusual patellar tendon ruptures, MRI evaluation shows
absence of distinct margins and increased signal intensity
within the patellar tendon.115
Dislocation of the patella produces a characteristic
pattern of change on MRI that allows diagnosis of this
Copyright © 2003 Elsevier Science (USA). All rights reserved.
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SECTION V • Lower Extremity
injury even if the patient is initially seen after relocation of
the patella.104 These findings include contusion of the
lateral femoral condyle (manifested as low signal intensity
on T1-weighted images), tear of the medial retinaculum,
and joint effusion.
FRACTURE CLASSIFICATION
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The three major categories of patella fractures are transverse, stellate, and vertical. Transverse fractures that are
proximal (basal) or distal (apical) are termed polar. Because
TABLE 54–1
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Fracture Classification
A. Nondisplaced fractures
1. Stellate
2. Transverse
3. Vertical
B. Displaced fractures
1. Noncomminuted
a. Transverse (central)
b. Polar
1. Apical
2. Basal
2. Comminuted
a. Stellate
b. Transverse
c. Polar
d. Highly comminuted, highly displaced
C. Fractures associated with bone–patellar tendon–bone autograft
1. Longitudinal
2. Transverse
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these usually extra-articular disruptions of the quadriceps
pose different therapeutic challenges, they are classified
separately13, 68 (Fig. 54–10). Wide variations within each
fracture pattern have prevented the creation of a useful
classification scheme.11, 13, 92 Because of this difficulty,
most authors have reviewed long-term results according to
treatment rather than fracture type.11, 13, 14, 25, 68, 82, 92, 100
For the purposes of this chapter, existing classification schemes were combined for better understanding11, 13, 68, 100 (Table 54–1). Although the terms stellate
and comminuted are interchangeable in much of the
published literature, we recommend distinguishing comminuted transverse fractures, which often have retinacular
disruption, from stellate patellar fractures, which are associated with an intact retinaculum.
A
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Nondisplaced Fractures
Presentation
C
B
STELLATE
Stellate fractures of the patella are the result of a direct
compressive blow that forces the bone against the femoral
condyles. Damage to the articular cartilage of the femoral
condyles and the creation of osteochondral fragments may
occur and must be ruled out.19 Typically, well over half
(65%) of these fractures are nondisplaced. In these fractures, the blow is insufficient to tear the patellar retinaculum, and active extension of the knee is therefore possible.
Displacement between fragments is, by definition, less than
3 mm, and displacement between the articular surfaces,
less than 2 mm. Unless an osteochondral fragment is
present and requires arthrotomy or arthroscopy, nonoperative therapy is indicated (Fig. 54–11).
D
FIGURE 54–10. Examples of patellar fractures. A, Undisplaced fractures
may have any degree of comminution, but fragments are displaced no
more than 3 mm. The articular surface as seen on the lateral view should
have a step-off of no more than 2 mm. B, Displaced transverse fracture
with comminution of the apical pole. C, Displaced transverse fracture
with comminution of both the apical and basilar poles. D, Highly
comminuted, highly displaced fracture.
TRANSVERSE
Transverse fractures of the patella are the result of a tensile
stress applied to the extensor mechanism. Typically, 35%
or more of all transverse patellar fractures are nondisplaced.1, 13 Damage to both the femoral and the patellar
articular surface is minimal,89 and the force is usually
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
insufficient to tear the medial and lateral patellar retinaculum.13, 42, 73, 89, 92 As a result, the patient retains the ability
to extend the knee. In addition, the intact soft tissue
envelope maintains patellar alignment; typically, less than
3 mm of fragment diastasis and 2 mm of articular incongruity exist. If these conditions are met, nonoperative
treatment is suggested (see Fig. 54–10).
VERTICAL
Vertical fractures (marginal or longitudinal fractures), contrary to earlier reports, are a common type of patellar
fracture, with a combined incidence of 22% (384/1707) in
several large series.9, 14, 32 The fracture may be caused by
different mechanisms. Dowd stated that direct compression of the patella in a slightly hyperflexed knee creates this
fracture.32 In Bostro¨ m’s series, lateral avulsions accounted
for more than 75% of all vertical fractures.14 Bony separation is most commonly found at the junction of the middle
and lateral thirds of the patella; less commonly, a medial
pole avulsion may occur.
Clinically, the patient has a somewhat painful knee and
a mild effusion. Full extension of the joint is possible
because the patellar retinaculum is intact.9, 14, 32 A diastasis
of greater than 3 mm is most unusual.13, 14 The fracture
may be missed on standard radiographs, and therefore
axial views are usually necessary to make the diagnosis.9, 14
If the defect is seen on the AP radiograph, it may easily be
mistaken for a bipartite patella, so radiographs of the
opposite limb should be obtained. Because the fracture
fragments are minimally displaced and the patellar retinaculum remains intact, these fractures are best treated nonoperatively.
2021
patella. The diagnosis is made in a patient with loss of
active extension of the knee (after aspiration), more than
3-mm separation between fracture fragments, or an articular step greater than 2 mm.8–10, 73, 92 These findings
suggest retinacular disruption and joint incongruity. Either
finding warrants operative repair (Fig. 54–12).
Some patients may have a gap of 4 to 5 mm between
fracture fragments but can extend their leg actively. McMaster warned of nonunion in these patients when treated
conservatively.73 Bostro¨ m, in reviewing the results of his
and other large published series, however, concluded that
active extension implied retinacular continuity and that
these patients could heal satisfactorily without surgery.13
We concur with his advice.
Polar
Polar fractures of the patella are transverse fractures occurring either proximal or distal to the patella equator and
taking varying amounts of bone. Proximal, or basal pole,
fractures imply avulsion of the quadriceps mechanism
from the patella. The amount of accompanying retinacular
rupture determines the patient’s ability to extend the leg.
Displacement is extremely rare and was seen in less than
4% of patients in several large series.13, 92
Distal, or apical, fractures are bony avulsions of the
proximal patellar tendon (Fig. 54–13). These fractures,
which occur toward the distal margin of the retinaculum, are almost invariably associated with loss of knee
extension. As a result, displacement in apical fractures
is almost three times as common (11.5%) as in basal
injuries.
COMMINUTED
Displaced Fractures
NONCOMMINUTED
Transverse/Midpatellar
Displaced fractures account for slightly more than half
(52%) of all noncomminuted transverse fractures of the
Stellate
A result of direct compression, comminuted stellate fractures usually exhibit displacement with varying degrees of
comminution.19 Although the patellar retinaculum is intact, operative intervention is indicated because of existing
articular incongruity (Fig. 54–14).
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Presentation
FIGURE 54–11. Nondisplaced stellate fracture of the patella. Radiographic projections are anteroposterior (A), oblique (B), and lateral (C).
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2022
Print Graphic
SECTION V • Lower Extremity
FIGURE 54–12. Displaced transverse
fracture of the patella. A, Anteroposterior
radiograph. B, Lateral radiograph.
Presentation
Print Graphic
FIGURE 54–13. Displaced distal polar fracture of the patella. A, Anteroposterior
radiograph. B, Lateral radiograph.
Presentation
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Presentation
FIGURE 54–14. Displaced stellate fracture of the patella. A, Anteroposterior view. The fracture is difficult to see. B, Lateral view. The fracture is apparent,
but displacement appears to be only moderate. C, A skyline radiograph clearly indicates displacement and incongruity of the articular surfaces.
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
2023
FIGURE 54–15. Comminuted transverse
fracture of the patella. A, Anteroposterior view. The details of the fracture’s
configuration are hard to see. The main
displaced transverse component and
secondary vertical fracture lines are
evident. B, Lateral view. Displacement is
more obvious, but comminution is less
apparent.
Print Graphic
Presentation
Transverse/Polar
These comminuted fractures exhibit varying degrees of
comminution of one major patellar fragment. Upper fragment comminution is usually accompanied by one or two
additional fracture lines that are minimally displaced.
Lower fragment comminution is generally more severe and
may be accompanied by upper pole comminution.11, 13
Comminution is much more prevalent in the lower pole
than the upper pole.
osteotome at the time of graft harvest.7, 75 These fractures
are treated by neutralization with screws directed in the
coronal plane. The screws are not placed in a lag fashion
because of the potential to create a distracting force at the
articular surface secondary to the defect from harvesting of
a graft.6 The rehabilitation protocol need not be modified if
the fractures are rigidly fixed, and rehabilitation should be
aggressively pursued.
Highly Comminuted, Highly Displaced
Highly comminuted and displaced fractures consist of
either transverse fractures with massive comminution secondary to compression or stellate fractures with massive
diastasis secondary to a violent quadriceps contraction
(Fig. 54–15). All major fragments are separated by more
than 6 mm, and sagittal splits are often present as well.
These fractures frequently occur as open injuries and can
be accompanied by supracondylar femur fractures.
TREATMENT
Fractures Associated with Bone–Patellar
Tendon–Bone Autograft
A subset of patella fractures has been reported in patients
who have had a bone–patellar tendon–bone autograft for
reconstruction of the anterior cruciate ligament.6, 17, 75, 103
An incidence of approximately 0.2% has been reported
in one study involving 1320 anterior cruciate reconstructions.103 The etiology of these fractures is most often
related to a traumatic fall or injury, but it has been
hypothesized that an ‘‘accelerated’’ rehabilitation protocol
may put patients at higher risk than the traditional rehabilitation protocol.17 These fractures occur in two patterns. A
transverse fracture is the most common and is generally
treated with traditional tension band wiring or screw
fixation techniques.6 Vertical, or ‘‘fissure,’’ fractures have
been noted as well. These injuries are thought to occur
from a stress riser created by a rectangular bone plug in the
patella or as a nondisplaced fracture created by the
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
Management of patella fractures is based on the morphology of the injury. Options include nonoperative treatment,
tension band wiring, lag screw fixation, partial patellectomy, partial patellectomy combined with tension band
wiring, and total patellectomy. These techniques are performed with careful reconstruction of the extensor mechanism and the patellar joint surface whenever possible.
Figure 54–16 outlines this chapter’s proposed algorithm for
the management of patella fractures. Specific details of
fixation may need to be modified to accommodate a given
fracture pattern.
Biomechanics of Patellar
Fracture Fixation
Carpenter and colleagues compared three internal fixation
constructs for transverse patella fractures in a cadaver
model.20 The three constructs included a modified tension
band (AO technique), two parallel 4.5-mm interfragmentary lag screws, and a 4.0-mm cannulated lag screw
technique with a tension band through the cannulated
screws20 (Fig. 54–17). A significant difference in displacement was noted between the modified tension band
construct and the lag screw techniques. The highest load to
failure occurred with the cannulated lag screw and tension
band construct. They concluded that the cannulated lag
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2024
SECTION V • Lower Extremity
DISPLACED
NONDISPLACED
Transverse
Stellate
Vertical
Noncomminuted
Comminuted
LAB/C
Wiring
Stellate
Transverse
Modified
anterior
tension
band wire
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Polar
Modified
anterior
tension
band plus
screws
Presentation
Transverse
Partial
excision
Polar
Highly comminuted
Highly displaced
Total
excision
Cylinder cast/cast brace
FIGURE 54–16. Displacement and the fracture pattern both guide the choice of treatment with which to obtain the two
primary goals of quadriceps mechanism continuity and stable anatomic reduction of the patellar articular surface.
Nondisplaced fractures are managed nonoperatively. Displaced articular fractures are repaired, if possible, by using tension
band wiring techniques with or without screws or interosseous wiring. Polar avulsion fractures may be excised, but secure
reattachment of the quadriceps or patellar tendon is required. If comminution prevents satisfactory repair, total patellectomy
may be the only option to restore the quadriceps. Abbreviation: LAB/C, longitudinal anterior band plus cerclage.
screw and tension band technique provided improved
stability in the fixation of transverse fractures of the patella.
Scilaris and associates compared tension band techniques with a monofilament wire versus a braided cable in
a transverse patella fracture cadaver model.88 The braided
cable construct allowed significantly less fracture displacement in cyclic loading than did the monofilament construct. They concluded that the braided cable plus tension
band construct was superior to the monofilament technique and was more predictable in cyclic loading.
Open Fractures
Open patellar fractures are surgical emergencies, and
surgeons must be aware of the possibility of osteomyelitis
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
and septic arthritis. Irrigation, de´ bridement, and stable
fixation remain the principles of treatment. Devitalized
fragments should not be saved, and heroic efforts at salvage
are not indicated. Fixation should be performed with a
minimum of soft tissue stripping and must be stable.
Subsequent repeat de´ bridement will be necessary, and
closure may require skin grafts, muscle flaps, or free tissue
transfer.
Catalano and co-workers retrospectively reported on a
series of 79 open patella fractures with an average of 21
months of follow-up.22 Open fractures were classified as
grade I (15%), grade II (53%), and grade III (32%) injuries.
Additionally, most open patella fractures were displaced,
with 22% being transverse fractures and 39% being comminuted fractures. Approximately 80% of the patients
sustained multiple injuries. Treatment consisted of operative de´ bridement and irrigation with appropriate antibiotics, followed by open reduction and internal fixation in
57% and partial patellectomy in 32%. Eleven percent were
treated with de´ bridement only, and no patients had a
primary total patellectomy. They reported no deep infections, and only one patient required repeat open reduction
and internal fixation. Seventy-six percent of the patients
were available for follow-up, and they had an average of
112° of knee motion.22
2025
fractures. Treatment consists of extension splinting for 4 to
6 weeks.13, 42, 73, 89, 92 If plaster is used, care should be
taken to extend the cast from a few centimeters above the
malleoli to the groin (not the middle of the thigh). If the
patient is elderly or has varicose veins, an Unna boot is
applied to the foot and ankle before casting to minimize
swelling.92
Immediate weight bearing as tolerated is permitted.
Isometric quadriceps exercises and straight leg raises are
encouraged within several days.13, 42, 73 After radiographic
evidence of consolidation, usually at 4 weeks, the plaster
may be removed, and progressive active (not passive)
flexion and strengthening exercises are begun.
In reliable patients, we prefer the use of an off-the-shelf
hinged knee brace. These braces are lightweight and easily
adjustable and permit controlled motion of the knee joint.
The knee hinge is locked in extension during ambulation
but may be opened to permit controlled motion during the
convalescent period. This type of brace may be advantageous for elderly patients. A simple knee immobilizer of
adequate length is a similar alternative.
Operative Treatment
PREOPERATIVE PLANNING
Nonoperative Treatment
Indications for nonoperative management include transverse, stellate, and vertical nondisplaced closed patellar
Before embarking on surgical repair of the patella, an
operative plan should be firmly established. Formulation of
the plan requires radiographic evaluation of the normal
opposite patella. On tracing paper or clear x-ray film, the
normal patella is outlined. The fracture fragments are then
A
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Presentation
B
C
FIGURE 54–17. Comparison of constructs for internal fixation of patella fractures. A, AO modified tension band construct. B, AO compression screws, 4.5
mm. C, Cannulated 4.0-mm screws combined with a tension band. (From Carpenter, J.E.; et al. J Orthop Trauma 11:351–356, 1997.)
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2026
SECTION V • Lower Extremity
superimposed onto this outline in both the AP and the
lateral planes. In effect, such superimposition ‘‘reduces’’ the
fracture. Attention is then turned to fixation, be it wires,
screws, partial excision, or a combination of methods.
These elements should be drawn onto the plan and
numbered in sequence. Finally, contingency plans, as well
as the necessary equipment, should be listed. The surgeon
should be aware that superimposition of the patella on the
femur makes this exercise difficult at times. It therefore
requires optimal radiographic technique and an awareness
that unanticipated comminution may be encountered.
Preoperative planning allows the surgeon to think
through the operative procedure and become acquainted
with the personality of the fracture. In addition, equipment
requirements will be known beforehand, thus promoting a
smoother operation without unnecessary delays. When
this plan is followed, the postoperative film will appear
remarkably similar to the preoperative plan.
large-fragment set should always be available. Large osteochondral fragments will require minifragment screws
or Herbert screws, and for small fragments, absorbable
polyglactin 910 (Vicryl) pins (Ethipins) should be on hand.
SETUP
The patient is placed in the supine position, and a
tourniquet is applied high on the thigh, if desired. Trapping
of the quadriceps may cause difficulty in repositioning the
patella when the tourniquet is inflated. This complication
may be prevented by flexing the knee carefully beyond 90°
to bring the quadriceps and proximal patella fragment
down before inflating the tourniquet. In patients with
complete retinacular disruption and a high-riding proximal
patellar fragment, a sterile tourniquet can be inflated, if
necessary, after the patella has been brought down with an
Esmarch bandage wrapped in a proximal-to-distal direction.23
EQUIPMENT
A wire set incorporating Kirschner wires (K-wires),
1.2-mm (18-gauge) and 1-mm (19-gauge) wire on spools,
wire holders, wire tighteners, wire pliers, and a wire passer
is necessary, along with a power drill and a wire driver
(Fig. 54–18). A small-fragment instrument and implant
set and Weber (large, pointed) bone reduction forceps
are also useful. A special patella clamp is an invaluable
device because the Weber clamps may rotate. Angiocatheters (14 or 16 gauge) are helpful for passing wire. A
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Presentation
INCISIONS
Although any anterior knee incision can be used, a
transverse, midline longitudinal, or lateral parapatellar
incision is preferred (Fig. 54–19). In patients with severe
retinacular disruption, a transverse incision should parallel
this disruption to minimize the development of flaps.68, 79
In more comminuted fractures, a midline longitudinal or
lateral parapatellar incision is necessary, especially if concomitant injuries suggest the possibility of joint replace-
FIGURE 54–18. Instruments and implants helpful for fixation of patella
fractures include pointed reduction
forceps for large bones (A), patella
forceps (B), wire tightener (C), wirebending pliers (D), wire cutter (E) for
Kirschner wires, wire bender/impactor (F), Kirschner wire (G), and malleable wire at least 1 mm in diameter (H).
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
2027
Tension Band Wiring
Modified Anterior Tension Band Wiring. For
displaced noncomminuted two-part transverse patellar
fractures, open reduction and internal fixation using the
modified anterior tension band technique is the treatment
of choice (Fig. 54–20).
A midline longitudinal incision is made through the
skin and overlying bursa. The fracture edges are exposed
and completely cleaned of debris and clot, with care taken
to not devitalize the fragments. The knee joint is then
irrigated to remove any loose fragments.
A preliminary reduction is performed to evaluate the
proper position of the fragments. The reduction is then
taken down, and the proximal fragment is flexed 90°. A
hole is drilled through the proximal fragment in a retrograde manner with a 2-mm drill bit. This hole should start
within the fracture line, approximately 5 mm from the
anterior surface of the patella and at the junction of a line
separating the patella into thirds. The drill bit is then
exchanged for a 1.6-mm K-wire that is pushed proximally
until it is flush with the fracture edge. A second hole
(parallel to the first and at the junction of a line separating
the patella into thirds) is drilled. The drill bit is exchanged
with a K-wire in a similar manner. The fracture is then
reduced and held with Weber or patellar reduction forceps.
The wires are sequentially removed and the holes drilled
distally with a 2.0-mm drill bit up to, but not through, the
distal cortex. A prebent 1.6-mm K-wire is inserted into the
drill hole and hammered through the far cortex. Next, a
1.2-mm (18-gauge) wire is placed underneath the upper
hooks and the lower protruding pin tips. The wire is
loosely tightened with a wire tightener. The reduction is
Print Graphic
Presentation
FIGURE 54–19. Incisions for exposure and treatment of patellar fractures.
Either a longitudinal or a transverse approach may be used. Sufficient
exposure to see and effectively repair medial and lateral retinacular tears
is important. Superficial dissection should be avoided to preserve
thickness and viability of the skin flaps.
ment in the future. These latter incisions also avoid damage
to the saphenous branch of the femoral nerve medially. A
percutaneous fixation technique for patella fractures has
been described. This method might be considered with
severely compromised skin.69 Berg has described an extensile exposure for comminuted fractures of the patella that
involves osteotomy of a tibial tubercle for retropatellar
exposure and fracture fixation.7 This technique facilitates
exposure and reconstruction of the patella and maintenance of bone stock without any morbidity associated with
the tibial tubercle osteotomy. Additionally, ablative salvage
procedures can be avoided and thus further improve joint
reconstruction options in the future.
OPERATIVE TECHNIQUES
All displaced fractures of the patella require operative
intervention. As previously mentioned, the techniques
used are based on the fracture pattern and concomitant
injuries (Table 54–2).
TABLE 54–2
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Treatment of Patella Fractures
Patella Fracture Type
Treatment
A. Nondisplaced
fractures
1. Transverse
2. Stellate
3. Vertical
B. Displaced fractures
1. Noncomminuted
a. Transverse
b. Polar
1. Apical
2. Basal
2. Comminuted
a. Stellate
Cylinder cast
b. Transverse
c. Polar
d. Highly
comminuted,
highly
displaced
Modified anterior tension band wiring
Partial patellectomy
Modified anterior tension band wiring
Modified anterior tension band wiring
Longitudinal anterior tension band plus
cerclage
Independent lag screws plus modified
anterior tension band wiring
Longitudinal anterior tension band
wiring
Partial patellectomy
Partial patellectomy
Modified anterior tension band wiring
Longitudinal anterior tension band
wiring
Partial patellectomy
Total patellectomy
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2028
SECTION V • Lower Extremity
Print Graphic
A
Presentation
D
B
C
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Presentation
FIGURE 54–20. Modified AO tension band technique for patella fracture fixation (see text). A, Retrograde drilling of the proximal fragment. Kirschner
wires mark the proximal ends of the holes during reduction. B, Reduction, clamping, and antegrade partial drilling of the distal fragment. K-wires
with prebent proximal ends are then hammered through the remaining bone of the distal pole. C, With a large-bore needle, the 1.2-mm tension band
wire is placed deep to the proximal and distal ends of the K-wires immediately adjacent to the patella through the stout soft tissue attachments of
the quadriceps tendon and patellar ligament. Medially and laterally, the tension band wire lies anterior to the patella and is not usually crossed. It
is tightened and twisted securely, and the ‘‘pigtail’’ end is bent flush with the bone surface. A twist or a square knot is reliable. The AO bent-wire
fastening technique is not secure enough for definitive fixation. D, The prebent proximal ends of the K-wires are driven into the proximal
pole, and the distal ends are trimmed if necessary. E, F, Anteroposterior (AP) and lateral radiographs show a displaced comminuted patellar fracture.
G, AP radiograph after fixation. Note the modifications in technique for fixation of comminuted fragments: supplementary K-wires,
distal-to-proximal K-wire insertion, and a distally crossed tension band wire, which was tightened with medial and lateral twists to equalize tension.
H, I, Lateral and skyline views show anatomic reduction and anterior placement of the tension band wire.
checked by extending the knee and palpating the undersurface of the patella with a finger. If a finger cannot be
easily inserted through the retinacular tear (or if none
exists), the retinaculum should be longitudinally incised to
permit insertion. If articular congruity is satisfactory, the
wire should be twisted tightly with a wire tightener and
buried. The K-wires are twisted so that the bend is facing
backward and then buried in the patella. The excess distal
ends of the K-wires are cut off distally.
Although certain authors recommend crossing the tension band wire, in our experience, crossing reduces the
area of patella that can be compressed and often leads to an
unstable osteosynthesis. A prefabricated cerclage loop (AO
type) is also not recommended for use as a tension band
wire because it can come undone with early motion.
Finally, the retinaculum is sutured closed with figure-ofeight 0 Vicryl interrupted sutures, and the wound is closed
in layers over a drain.
Modified Anterior Tension Band Wiring through
Cannulated Compression Screws. When failure of the
standard tension band technique is a concern in an elderly
patient with osteopenic bone, an alternative is a modified
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
2029
Print Graphic
Presentation
FIGURE 54–21. Tension band technique through cannulated compression screws. A, Transverse patella fracture. B, Anteroposterior view of 4.5-mm
cannulated compression screw fixation with a tension band wire. C, Lateral view demonstrating the tension band construct through cannulated
compression screws.
anterior tension band through cannulated compression
screws.8 Berg described this technique in which two
parallel cannulated cancellous screws are placed longitudinally over guide wires with lagged interfragmentary
compression. An 18-gauge AO wire is then passed in a
figure-of-eight fashion through the cannulated screws and
tightened with a Kirschner traction bow. The remainder of
the fixation technique remains the same as for the standard
anterior tension band construct (Fig. 54–21).
Longitudinal Anterior Band plus Cerclage Wiring.
Minimally displaced stellate fractures requiring operative
intervention may not have a single fragment large enough
to permit a modified anterior tension band technique. In
these cases, either the K-wire should be angled appropriately or the longitudinal anterior band plus cerclage
(LAB/C) wiring technique of Lotke and Ecker may be
used68 (Fig. 54–22).
The patella is approached, and the fragments are
cleaned as described in the section Modified Anterior
Tension Band Wiring. Two parallel Beath-Steinmann pins
(with holes in the distal tip) are drilled 1 cm from the
patellar edges through the aligned patella fragments in an
antegrade manner. A 22-gauge wire is then inserted into
both drill holes, and both pins are removed proximally. The
distal loop is brought anteriorly, and one free proximal end
is passed through this anterior loop. It is then tied to the
other proximal end and tightened. This technique results
in a strong and secure combination of anterior band and
interosseous wiring techniques. Heavier-gauge wire may be
safer for fixation—for example, 18-gauge wire passed with
the aid of a large angiocatheter placed over the K-wire and
held in place when it is withdrawn.
If marked comminution is present, a cerclage wire
should first be placed around the circumference of the
patella, which can easily be done with a wire passer or a
16- or 14-gauge angiocatheter inserted immediately next
to the patella. The LAB/C wiring is then performed. The
retinaculum is sutured closed with figure-of-eight 0 Vicryl
Print Graphic
Presentation
A
B
C
FIGURE 54–22. Longitudinal anterior band plus cerclage technique for interfragmentary wire loop fixation of patella fractures. A, For transverse fractures,
the two ends of a wire loop are passed through longitudinal drill holes in the patella. One of these wire ends is then passed through the loop made by
the middle of the wire distally. Next, the ends are pulled tight and twisted to provide a taut anterior tension band. B, Lateral view. C, In fractures with
significant comminution, fixation is aided by first placing a cerclage wire around the patella to trap the comminuted fragments and then drilling and
applying the longitudinal anterior band wire as in A. (A–C, Redrawn from Lotke, P.A.; Ecker, M.L. Clin Orthop 158:180–184, 1981.)
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2030
SECTION V • Lower Extremity
interrupted sutures, and the wound is closed in layers over
a drain.
Independent Lag Screws plus Modified Anterior
Tension Band Wiring. Transverse fractures may have one
or two additional fracture lines in the main fragments that
separate the main fragments into halves or thirds. These
secondary fracture lines are not usually displaced, but they
may become so after operative intervention is attempted.
The general principles of internal fixation of fractures
should be followed (i.e., to make many fragments into two
main fragments and then unite these two into one). Such
fixation can usually be accomplished with independent lag
screws placed in a horizontal direction, followed by a
modified anterior tension band wiring technique. The size
of the screw should fit the size of the bone (e.g., 3.5-mm
cortical screws will usually suffice, except in large adult
men, in whom 4.5-mm screws should be used) (Fig.
54–23). If the fragment is comminuted at the point of
screw entry, a washer is used. Frequently, a fragment has or
acquires a sagittal split during insertion of the lag screw;
the split separates the anterior cortex from the main
chondral surface of that fragment. If this fragment cannot
be salvaged by repositioning the screw, LAB/C wiring or
excision of the fragment should be considered.
Partial Patellectomy
Not infrequently, patellar fractures exhibit significant comminution of one pole, and the fragments may involve a
smaller or larger portion of the patella. At times, indirect
reduction with a modified anterior tension band or LAB/C
wiring technique will be effective. If these techniques are
not possible, the time-honored method of partial patellectomy should be performed1, 25, 79, 101 (Fig. 54–24).
The patella is approached and the fracture exposed as
previously described. All large, stable, distal fragments
should be retained, and all small, comminuted fragments
should be excised. All loose strands of the torn quadriceps
expansion are removed. If one large distal fragment is
present, it may be lagged into position with screws after
reduction has been secured. Care must be taken to not
angle this fragment or patellofemoral arthritis will develop
(see Fig. 54–24C). This procedure can be simplified by
placing a bolster underneath the ankle to extend the knee.
Print Graphic
Presentation
A
B
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Presentation
FIGURE 54–23. AO lag screw plus tension band technique. A, Small-fragment screws can be used alone to fix vertical components or comminuted portions
of the patella. B, These screws should be supplemented with a tension band wire for fixation of displaced transverse fractures because screws alone may
not withstand the significant forces developed by the quadriceps mechanism. Anteroposterior (AP) (C), lateral (D), and skyline (E) radiographs show a
displaced oblique (functionally transverse) patellar fracture. Postoperative AP (F) and lateral (G) radiographs show the use of 4.0-mm cancellous lag screws
supplemented by an anterior tension band wire. The wire is crossed in this case to maintain its position anterior to the fracture.
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
2031
A
Print Graphic
Presentation
C
B
FIGURE 54–24. Techniques of partial patellectomy. A, Extensive comminution of the central portion may be excised, with fixation of the proximal-to-distal
poles with screws or K-wires and a tension band. The results of this technique are not well documented. B, A small (usually extra-articular) bony fragment
may aid in reattachment of the patellar ligament distally. Screws, K-wires, or sutures may be used, but they should always be protected with a tension
band, either limited to the patella if the distal pole fragment is sufficient or from the patella to the tibial tubercle if it is not sufficient. C, When suturing
the patellar ligament into a defect in the distal pole of the patella, it is essential to not attach it too anteriorly because such positioning will result in
malalignment of the patella (left), the distal articular surface being forced too far posteriorly. The example on the right shows proper reattachment of the
patellar ligament. A tension band from the patella to the tibia should protect this repair.
Because of the powerful tension developed in the
quadriceps mechanism, significant stress is placed on its
repairs, which must be protected. This goal can be accomplished by using a crossed tension band through
either the quadriceps insertion or the proximal part of
the patella and through the proximal end of the tibia
by a variety of means (Fig. 54–25). We prefer wire
passed directly through the bone because it is less bulky
and easier to remove. Mersilene tape or fascia may also
be used.
If only small fragments remain distally, the following
technique is used. The anterior periosteum is reflected on
the proximal fragment approximately 5 mm, and with a
rongeur, a transverse groove is made in the proximal
fragment within the fracture line itself. Three holes are
drilled so that they are equally spaced from the fracture line
and exit the superior aspect of the patella. Next, with a
heavy, braided, nonabsorbable suture and an atraumatic
needle, the suture is passed distally in a running, locking
stitch along one edge of the tendon and then returned in
the midline of the tendon. A second suture is passed in a
similar manner along the opposite side of the tendon and
back along the midline. The suture ends are passed
through the appropriate drill holes in the patella, with two
sutures through the central hole. A straight, free needle can
be used to pass the sutures. Each suture is tied to its
opposite end. This step should be done while the knee is
hyperextended and should bring the tendon end into close
approximation with the trough in the distal aspect of the
proximal part of the patella. A tension band should be
added to neutralize stress on the repair. The retinaculum is
then sutured closed with figure-of-eight 0 Vicryl interrupted sutures, and the wound is closed in layers, over a
drain if desired.
Total Patellectomy
For highly displaced, highly comminuted fractures, an
attempt at reconstruction should be made before total
patellectomy is performed. Several authors have stressed
the retention of even one fragment to maintain a lever
arm.33, 92, 100, 101 A combination of partial patellectomy
and modified anterior tension band or LAB/C wiring is
usually tried before total excision is performed. Although many techniques exist, those presented in the
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2032
Print Graphic
SECTION V • Lower Extremity
A
B
C
Presentation
FIGURE 54–25. A tension band wire technique
should be used to protect the patellar ligament
reattachment after distal pole fracture fixation,
partial patellectomy, or repair of a ruptured
patellar ligament (A). B, C, The 1.0- or 1.2-mm
wire can be attached to a screw through the tibial
tubercle. D, It can be placed through the
quadriceps tendon just proximal to the patella or
through a drill hole in the patella and through a
drill hole distally. Anteroposterior (E) and lateral
(F) radiographs show the tension band wire
protecting the reattached patellar ligament after
distal partial patellectomy.
D
Print Graphic
Presentation
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2033
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
following paragraphs are the most favorably reviewed in
the literature.
Because total patellectomy is often a salvage procedure,
the surgeon may find various skin incisions and retinacular
remnants. Once a decision for total extirpation has been
made, all fragments of bone and shredded tendon are
removed sharply, but as much tendinous expansion as
possible is left. The critical feature of a total patellectomy is
the tendinous repair. Because the quadriceps tendon is
effectively lengthened by the removal of bone, this slack
should be taken up by imbrication (i.e., in a pursestring
repair), or an extensor lag will result.
If insufficient tendon exists for primary repair, several
options are available. These options can be separated into
two categories: quadriceps turndown procedures and fascial or tendinous weaving. The former technique is used
when prepatellar soft tissue is absent, whereas the latter
is reserved for injuries with destroyed quadriceps tendon
as well.
The most common quadriceps turndown technique is
the inverted V-plasty of Shorbe and Dobson.93 After the
patella has been excised, the quadriceps tendon is exposed
for approximately 3 inches (Fig. 54–26). A full-thickness
incision is made into the quadriceps tendon in the shape of
a V, with the apex located 2.5 inches proximal to the
former proximal patellar edge. The limbs of the incisions
extend distally for 2 inches such that ] to 1⁄2 inch of
tendon is continuous with the retinaculum. The corners
may be reinforced with suture if necessary. The apex is
subsequently folded down, inserted through the proximal
portion of the patellar tendon, and sutured down. The
quadriceps tendon should then be closed and all edges
repaired. This repair is simple to perform, yet has the
advantage of being strong enough to allow early motion.
Should a large defect involving the quadriceps tendon
be present, a free fascial or tendinous strip is woven into
the tendinous remnants after the method of Gallie and
Lemesurier.39 First, all excess tendinous shreds are removed from the wound. The knee is extended with
padding under the ankle and the defect measured. This
length should be doubled and 2 inches added to obtain the
ideal length of a fascial graft. A separate lateral incision is
made or the wound is extended, and a strip of fascia lata or
an iliotibial band of the appropriate length and 1 to 1.5 cm
in width is obtained. The strip of fascia is rolled into a
cylinder along its long axis and sutured to itself. It is then
woven through the remaining quadriceps tendon or muscle, sewn to itself, passed through the patellar tendon, and
tacked down after the slack is taken out. The graft should
be of sufficient length to sew one end down to the other.
Finally, all edges are firmly sutured down. If the defect
requires an exceptionally long strip, plantaris tendon can
be used.
POSTOPERATIVE MANAGEMENT
With a stable osteosynthesis, the patient may begin using a
continuous passive motion machine to tolerance immediately postoperatively. In our experience, use of this device
decreases pain and stiffness. On the first postoperative
day, the patient can be out of bed with the leg elevated,
and quadriceps isometric exercises are begun. Drains, if
used, are generally removed after 48 hours. The patient is
then placed in a removable knee brace and permitted to
ambulate with weight bearing as tolerated and the knee
locked in extension. The hinges may be loosened for active
range-of-motion exercises. These exercises should not be
performed until the wound is well healed, usually at
3 weeks. Active extension and straight leg raising exer-
FIGURE 54–26. Inverted V-plasty technique of Shorbe and Dobson for repair
of a patellectomy defect. A, The patella
is resected, with a transverse defect left
in the quadriceps mechanism. The
retinacular rents are repaired first. B, If
a defect remains centrally, an inverted,
distally based, V-shaped flap of quadriceps tendon is turned distally as
shown. C, The flap is sutured in place
to cover and reinforce the defect.
Print Graphic
Presentation
A
B
Copyright © 2003 Elsevier Science (USA). All rights reserved.
C
2034
SECTION V • Lower Extremity
cises may be initiated as early as 1 week postoperatively.
Progressive resistance exercises are performed after radiographic evidence of healing, usually at 6 weeks. The patient
is then weaned from the brace and, by 3 months postoperatively, usually has a healed fracture and strong quadriceps.
Sports and vigorous work may be resumed after rehabilitation is complete, usually in 4 to 6 months.
For an unstable osteosynthesis, the repair must be
protected. Ideally, a knee brace with locking hinges will
permit controlled motion. The hinges are set to allow full
extension. Flexion to the degree possible during intraoperative assessment of the repair is permitted, primarily for
cartilage nutrition. The brace should be worn at all times,
and active flexion exercises should not begin until the
fracture has healed. Isometric quadriceps extension exercises should be initiated at 2 weeks. Weight bearing in full
extension can usually be allowed once comfort permits.
Weight bearing on the flexed knee should be avoided until
fracture healing is secure. The patient should be made
aware of possible knee stiffness. When the fracture has
healed radiographically and is clinically stable, attempts at
rehabilitation are begun to improve flexion range and
strength of all muscle groups.
Implant removal should be delayed until fracture union
is mature, which usually requires a minimum of 6 months.
K-wires may be extracted if they are painful and protruding, but loss of fixation with fracture displacement generally requires revision surgery. Asymptomatic implants may
be retained indefinitely. Wires used to protect tendon
repairs should be left in place for a minimum of 3 to
6 months.
TABLE 54–3
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Clinical Grading Scale
Clinical Grading Scale/Variable
Score
Range of motion (ROM)
Full extension, ROM >120°
Full extension, ROM 90°–120°
Loss of full extension, ROM <90°
Pain
None or minimal on exertion
Moderate on exertion
In daily activities
Work
Original job
Different job
Cannot work
Atrophy (10 cm, proximal part of patella)
<12 mm
12–25 mm
>25 mm
Aids
None
Cane part-time
Cane full-time
Effusion
None
Reported to be present
Present
Giving way
No
Sometimes
All the time
Stair climbing
Normal
Difficult
Disabling
6
3
0
6
3
0
4
2
0
4
2
0
4
2
0
2
1
0
2
1
0
2
1
0
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Excellent, 30 to 28 points; good, 20 to 27 points; failure, <20 points.
Source: Modified from Bo¨stman, O.; et al. Injury 13:196–202, 1981.
Results
No generally accepted outcome assessment system is
available for patellar fractures. Most authors base outcome
on subjective complaints of pain, limitation in activities of
daily living, change in job status, and ambulation.14, 35, 92
Bo¨ stman and colleagues developed the most complete
evaluation of clinical results to date11 (Table 54–3). However, this table, like most reports in the literature, does
not evaluate radiographic findings. Radiographic criteria
would include osteoarthritis, fibrous union or nonunion,
the presence of osteochondral fragments, and the degree of
articular step-off on the radiograph.11, 19, 92 The lack of a
uniform assessment scale allows only broad generalizations
to be made about the results of treatment of these injuries
(Table 54–4).
NONOPERATIVE TREATMENT
Nonoperative treatment of nondisplaced fractures nearly
always has a uniformly good outcome,13, 73, 89, 96 which
implies full range of motion and no arthrosis, weakness, or
pain (see Table 54–3). In Bostro¨ m’s series of 422 patellar
fractures, 219 were treated nonoperatively and were available for follow-up.13 All cases initially had less than 4 mm
of articular incongruity; 54% (118/219) had excellent
results, and 44% (97/219) had good results. Only two
failures occurred. His results agree with the findings of
other large series in that the failure rate from nonoperatively treated, nondisplaced patellar fractures was 5%.
OPERATIVE TREATMENT
Results of operative repair are based on the type of
fracture and the technique used (Table 54–5). Modified
anterior tension band wiring has given the best results
in the literature to date, with 57% excellent and 29%
good results11, 12, 54, 64, 108 (Table 54–6). Unfortunately,
many studies are vague in reporting results, and studies
TABLE 54–4
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Combined Results of Various Forms of Operative
Treatment in the Literature
Results
Treatment
Excellent
Good
Fair
Total
No.
ORIF
Partial excision
Total excision
Totals
135 (37%)
32 (23%)
62 (28%)
229
129 (36%)
67 (49%)
96 (44%)
292
97 (27%)
39 (28%)
61 (28%)
197
361
138
219
718
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Abbreviation: ORIF, open reduction and internal fixation.
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
TABLE 54–5
Partial Patellectomy
Partial patellectomy may give functional results comparable to those of open reduction and internal fixation,
but comparison is difficult because the fracture patterns
treated by these techniques are different.12, 13, 64, 68, 101
Sutton and co-workers showed that the only deficit with
partial excision of at least one third of the patella is an
18° loss of motion.99 In studies by Bo¨ stman and associates, Bostro¨ m, Mishra, Nummi, and Seligo, a nearly
normal outcome occurred when large fragments of patella were retained and articular congruity was maintained.12, 13, 76, 82, 92 Small fragments without soft tissue,
sagittally split fragments, and those missing cartilage were
excised. These authors found that saving these fragments
did not improve function and even compromised it.
Retention of one or two large fragments, however, improved quadriceps function.12, 13, 41, 58, 64, 101, 109 Hung
and colleagues reported the results of a 25-month
follow-up in a retrospective series of patients in which
radiographic changes consistent with post-traumatic arthritis developed in 55% after partial patellectomy and
tension band repair.53 However, most of these patients
were asymptomatic within that time frame.
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Results of Operative Repair in Patellar Fractures
Results
No.
Patients
Author, Year
OPEN REDUCTION, INTERNAL FIXATION
Seligo,92 1971
35
Nummi,82 1971
66
75
Bostro¨m,13 1972
Bo¨stman et al.,12 1983
48
Ma et al.,69 1984
107
30
Levack et al.,64 1985
Totals
361
Excellent
Good
Fair
10
3
19
17
77
9
135
(37%)
18
18
42
21
20
10
129
(36%)
7
45
14
10
10
11
97
(27%)
PARTIAL EXCISION
Seligo,92 1971
Nummi,82 1971
Bostro¨m,13 1972
Mishra,76 1972
Bo¨stman et al.,12 1983
Totals
3
68
28
4
35
138
0
14
8
2
8
32
(23%)
1
28
15
1
22
67
(49%)
2
26
5
1
5
39
(28%)
TOTAL EXCISION
Seligo,92 1971
Nummi,82 1971
Bostro¨m,13 1972
Mishra,76 1972
Einola et al.,35 1976
Wilkinson,112 1977
Bo¨stman et al.,12 1983
Levack et al.,64 1985
Jakobsen et al.,56 1985
Totals
44
13
5
26
28
31
10
34
28
219
14
0
0
3
6
7
0
20
12
62
(28%)
25
5
1
15
18
12
3
7
10
96
(44%)
5
8
4
8
4
12
7
7
6
61
(28%)
Total Patellectomy
Total patellectomy has yielded varying degrees of success.
Before the 1970s, poor reconstructive results justified total
patellectomy.16, 31, 40, 44, 45, 50 Investigators compared operative repair with a single cerclage wire and total excision.
Although many stated that good clinical results were
expected, more recent studies have questioned this conclusion11, 13, 64, 89 (see Table 54–5).
Sutton and co-workers evaluated quadriceps strength,
activities of daily living, and functional ability in patients
who had undergone either partial or total patellectomy.99
The opposite normal knee was the control. Both groups
had an average loss of 18° range of motion. A 49%
reduction in strength of the extensor mechanism was
present in the total-excision group. This reduction in
strength was the result of loss of the lever arm produced by
loss of the patella. Instability was greater in this group, with
the patellectomized knee losing almost 50% of excursion in
stance-phase flexion. This loss was a result of the patellar
tendon sinking into the intercondylar notch. Clinically, this
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reporting this technique are few. Analysis of combined data
shows tension band wiring to be superior to simple
cerclage wiring clinically. In addition, Weber and colleagues showed the superiority of tension band wiring
biomechanically108 (see Table 52–6). Modified wiring
techniques can also be effective. In Lotke and Ecker’s report
on LAB/C wiring, 16 cases were presented; 13 (81%) had
excellent results.68
TABLE 54–6
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Comparison of Anterior Tension Band vs. Cerclage Wiring
Results of Anterior Tension Band
Author
Bo¨stman et al.12
Bostro¨m13
Levack et al.64
Seligo92
Ma et al.69
Nummi82
Totals
Results of Cerclage Wiring
No. Patients
Excellent
Good
Poor
Excellent
Good
Poor
29
75
30
31
81
66
312
9
—
7
—
—
—
16
(57%)
3
—
5
—
—
—
8
(29%)
2
—
2
—
—
—
4
(14%)
6
19
2
10
59
3
99
(35%)
6
42
5
14
15
18
100
(35%)
3
14
9
7
7
45
85
(30%)
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Copyright © 2003 Elsevier Science (USA). All rights reserved.
2036
SECTION V • Lower Extremity
instability was manifested as insufficiency and inability to
support the loaded knee in stair climbing. Biomechanical
studies on cadaver knees performed by Watkins and
associates, Wendt and Johnson, and others all showed that
total patellectomy resulted in loss of tibial torque and,
therefore, strength.42, 58, 105, 109
Srensen noted that the quadriceps did not improve in
strength after patellectomy.96 All patients complained of
frequent giving way and difficulty running and walking
down stairs. He concluded that none of his operative
reconstructions would have fared better with total excision of the patella and thus justified attempts at salvage.
Wilkinson evaluated 31 patients 4.5 to 13 years after total
excision.112 In this study, less than a fourth of the patients had an excellent result. He also noted that maximal recovery took up to 3 years. Einola and colleagues
were able to monitor 28 patients for an average of 7.5 years
after total excision.35 Good results were seen in only six
patients. The predominant complaint was weakness and
pain on movement and exertion. The most common
finding was quadriceps atrophy. Quadriceps power was
within 75% of the normal knee in only seven cases. He
concluded that saving as much patella as possible was
advisable. Scott reported that only 6% (4/71) of patients
were happy with their long-term outcome after patellectomy.89 Ninety percent had aching in the joint, and 60%
complained of weakness. Quadriceps wasting was a constant finding.
The present recommendations are to therefore retain as
much patella as possible.11–13, 33, 54, 64, 79, 100, 101 Total
patellectomy is reserved for fractures that are so comminuted that repair is futile. This plan will offer the patient
the best possible knee function for the longest period. How
much patella should be saved? No definitive answer exists.
It is our opinion that as little as 25% of the patella (i.e., one
quadrant) may be retained with a subsequently good
outcome. We have never found a patella so comminuted
that one fragment could not be salvaged with repair. If no
articular congruity exists, however, excision is the only
option.
Breakage of Wires, Loss of Fixation,
and Refracture
After osteosynthesis, especially with early motion, the
tension band may break, but it is unusual for such breakage
to occur before healing of the patella. If the fracture is
healed, the wire, pins, or screws may be removed if they
cause symptoms.
Loss of fixation during the healing phase will require revision if the fragments separate more than 3 to
4 mm or if the articular surface has an incongruity greater
than 3 mm. Before returning to the operating room, a
radiograph should be obtained in full extension. If
reduction has improved, the patient may benefit from
6 weeks of extension splinting. Usually, however, isometric exercises will continue to separate the fragments, and
unless the patient refuses, revision should be undertaken.
Refracture should be treated as a fresh fracture according to the principles previously described (i.e., nondisplaced fractures are treated nonoperatively and displaced
fractures are treated operatively).
Delayed Union and Malunion
Delayed union, once a routine result, is extremely uncommon. If identified, a period of decreased motion is begun
because the fracture will often spontaneously unite. Weber
and Cech could find only three cases of patellar pseudarthrosis in their large series of nonunions.107 All healed after
revision surgery performed with established fracture fixation methods. If it is an old nonunion with 4 to 5 inches of
separation, reconstruction should be attempted. Quadriceps shortening will make this repair difficult, and formal
quadricepsplasty may be required. Care must be taken to
obtain the correct length or disability will continue. If
chondromalacia exists, consideration should be given to
performing a total patellectomy and fascial reconstruction
according to the method of Gallie and Lemesurier.39
Loss of Knee Motion
COMPLICATIONS
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Infection
Superficial wound infections should be treated by standard
protocol based on the degree of soft tissue involvement.
Osteomyelitis is aggressively treated with resection of all
sequestra and dead tissue. Irrigation and de´ bridement of
the knee must be repeated every 48 to 72 hours until the
joint is free of necrotic tissue to prevent septic arthritis.
Daily bedside aspiration is not indicated. The patient
should receive 6 weeks of culture-specific intravenous
antibiotics. Once the deep bone infection is under control, an attempt should be made to salvage any remaining patella by individualized and modified wiring techniques. If salvage is not possible, total patellectomy may be
required.
The advent of tension band wiring has permitted early
range of motion, and functional range of motion can be
expected in most cases. If flexion is still decreased several
months postoperatively, intensive physiotherapy is begun.
If such physiotherapy does not suffice, manipulation under
anesthesia should be contemplated. Care must be exercised
in patients requiring manipulation who have had patellectomies because rupture of the repair may occur. A report
has been published of a ‘‘boutonnie`re deformity’’ after
manipulation of a longitudinally repaired extensor retinaculum.81 If gentle manipulation is unsuccessful, consideration is given to arthroscopic lysis of intra-articular adhesions. Quadricepsplasty is performed only in exceptional
cases, usually when no improvement is seen after 9 to 12
months. This situation is most often the case after concomitant injury to the distal end of the femur has resulted in
binding down of the quadriceps mechanism.
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
Occasionally after total patellectomy, the extensor
mechanism is too long, which may result in loss of full
extension. The patient has a sensation of instability and
giving way.96 In this rare situation, consideration is given to
a Maquet procedure to bring the patellar tendon forward
and increase its mechanical advantage. This technique has
been described by Kaufer in excellent biomechanical studies.58 Reports of clinical results of the Maquet procedure
for this purpose are nonexistent. We would caution against
using too large a bone block because of subsequent skin
breakdown and pain. Other authors suggest reefing the
extensor mechanism, but this maneuver runs the risk of
rerupture.93
Osteoarthritis and Patellar Enlargement
Although Bruce and Walmsley18 and Cohn27 showed
that osteoarthritis occurred in rabbits after patellectomy, this complication has never been borne out
in long-term studies of postpatellectomy human
knees.1, 13, 19, 35, 56, 76, 99, 112 In addition, articular incongruity causing osteoarthritis has not been reported in
long-term studies.13, 96
Two situations have been demonstrated to increase the
incidence of osteoarthritis. Patellar enlargement, a result of
exuberant bone formation during the healing of comminuted fractures, has been unequivocally shown to cause
patellofemoral arthritis. Total patellectomy should be entertained if such enlargement has developed.
The second situation that will cause osteoarthritis is
posterior rotation of the distal pole of the patella after
reattachment of the patellar ligament in too anterior a
position in distal pole patellectomy.33, 92 Care must be
taken during repair to avoid such reattachment (see the
section Partial Patellectomy and Fig. 52–24C).
Tendon Rupture after Total Patellectomy
Rarely, the extensor mechanism will rupture after total
patellectomy, usually at the proximal edge of the patellar
tendon.36 This rupture should be repaired by the variety of
techniques suggested in the following section.
EXTENSOR MECHANISM INJURIES
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A patient with post-traumatic loss of knee extension and
negative results on radiographs should be suspected of
having a quadriceps or a patellar tendon rupture. Rupture
of the extensor mechanism appears to be age specific. Most
quadriceps ruptures occur in patients older than 40 years,
and most patellar tendon ruptures occur in patients younger than 40.94 The tendon may rupture from a tension tear,
direct sharp or blunt trauma, metabolic abnormalities,
collagen disease, repeated microtrauma, or repeated adrenocorticoid injections.77 In elderly patients, fatty degeneration and tendon scarring are the predisposing causes.90
2037
Quadriceps Rupture
Rupture of the quadriceps occurs primarily in the rectus
tendon, usually 0 to 2 cm from the superior pole of the
patella.90, 95 The diagnosis is often missed if the patient has
little pain or effusion.84 Physical examination will reveal
a palpable defect proximal to the superior pole of the
patella.84 In addition, extension against gravity must be
assessed. If the quadriceps tendon has a palpable defect but
active, full extension is maintained, the tear is incomplete.
Such a partial tear does not require operative repair.90
If the ability to extend the knee is completely lost, both
the tendon and the retinaculum are torn. The patient will
have difficulty climbing stairs, and the knee will buckle
with ambulation.84 Operative repair is required.95 Furthermore, if a complete quadriceps rupture is not treated
acutely, the quadriceps may ride as far as 5 cm proximally
on the femur and then bind down.90 For this reason, repair
should be done as quickly as possible.
ACUTE RUPTURES
Most authors agree that an end-to-end repair produces excellent results in acute quadriceps tendon ruptures.62, 77, 94, 95, 102 In Miskew and co-workers’ series,
90% of their patients had an excellent outcome.77 Similarly, Larsen and Lund considered their results in 15 of 18
cases (83%) to be excellent,62 and Vainionpa¨ a¨ and associates had only 1 failure in 12 cases.102 The largest series in
the literature is that of Siwek and Rao, who reported 36
cases of rupture. They found that all 30 patients with an
immediate end-to-end repair had excellent or good results
with knee range of motion of 0° to 120°.94 Complicating
primary end-to-end repairs is the difficulty in neutralizing
forces across the repair. A review of the literature revealed
only five cases in which a stress-relieving wire was used to
protect this repair.62, 94, 97, 102 Several authors reported on
the use of a 5-mm Dacron graft to protect the primary
repair.66, 77 Levy and colleagues used this technique and
permitted early motion without the use of a cast postoperatively, but weight bearing was delayed for 6 weeks.66 Most
published series used a local reinforcement flap as suggested by Scuderi, followed by 6 weeks in an extension
cast.62, 84, 90, 94, 95, 102
Scuderi Repair
In the Scuderi repair (Fig. 54–27), the edges of the torn
quadriceps are freshened and then pulled together so that a
slightly overlapping repair is performed. A distally based,
partial-thickness triangular flap of quadriceps tendon is
then turned down over the suture line to protect the repair.
This flap is an isosceles triangle, 3 inches along each side
and 2 inches at the base. Alternatively, a variation involving
the middle third of the patellar tendon may be used.24 In
this case, the tendon is freed distally, folded proximally, and
sewn down. After such repairs, immobilization in a cylinder cast for 6 weeks is advised.
Haas and Callaway described a technique for repair of a
ruptured quadriceps tendon.43 A midline incision is made,
with dissection carried down to the level of the patella and
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2038
SECTION V • Lower Extremity
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Presentation
A
B
C
D
FIGURE 54–27. Scuderi repair of a ruptured quadriceps tendon. A, The defect is exposed through a midline longitudinal incision. B, Fasciocutaneous flaps
are developed to reveal the defect. C, Interrupted nonabsorbable stout mattress sutures repair the tendon. These sutures may be directed to the patella
centrally. D, An inverted, partial-thickness, distally based, V-shaped flap is used to reinforce the repair. (A–D, Redrawn from Scuderi, C. Am J Surg
95:626–635, 1958.)
tendon. Hematoma and fibrous debris are excised without
removing an excessive amount of tendon. Three heavy
nonabsorbable sutures are passed through the proximal
tendon remnant in a Kessler-type stitch. A transverse
trough is created in the proximal pole of the patella with a
bur. Care must be taken to prevent placing the trough too
Print Graphic
Presentation
anterior to avoid subsequent tilting of the patella. Three
longitudinal holes are drilled in the patella, and the sutures
are passed through these tunnels and tied distally at the
inferior pole of the patella. The retinaculum is repaired
primarily with absorbable suture, and the leg is immobilized in full extension for 6 weeks (Fig. 54–28).43
FIGURE 54–28. Three heavy nonabsorbable sutures
are passed through the proximal tendon remnant in a
Kessler-type stitch. Three longitudinal drill holes are
created in the patella, and the sutures are passed
through these tunnels and tied distally at the inferior
pole of the patella. (From Haas, S.B.; Callaway, H.
Orthop Clin North Am 23:687–695, 1992.)
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
CHRONIC RUPTURES
In patients with quadriceps ruptures older than 2 weeks,
muscle retraction of as much as 5 cm with adherence of the
quadriceps muscle to the femur is common.90, 94 The delay
in treatment may require quadriceps lengthening, tendon
or muscle transfers, or a combination of these methods as
discussed in the sections that follow.24, 49, 83, 90, 94
Codivilla V-Y Lengthening
For a Codivilla V-Y lengthening procedure (Fig. 54–29),
a standard midline or lateral incision is made, and all
soft tissue adhesions are freed from the quadriceps tendon and muscle. The quadriceps muscle is then freed
from the femur, with elevators used if necessary to break
all scars. The knee should be in extension with a roll
under the heel. The old tear is located, and the ends are
freshened. The gap is then measured. A full-thickness,
distally based, V-shaped incision is made in the quadriceps tendon. Partial-thickness incisions in the vasti may be
necessary to aid in stretching. The original quadriceps
defect is then repaired. The V may be turned distally to
reinforce the repair as in the method of Scuderi. The
proximal defect in the quadriceps tendon is then repaired
in a side-to-side manner. A cylinder cast is worn for
6 weeks.
Myoplasties and Tendon Transfers
When quadriceps retraction and adhesions make standard
techniques impossible (as in neglected tears), neither the
Scuderi technique nor Codivilla V-Y lengthening may be
sufficient. In these complex, long-standing cases, an aponeurotic vastus lateralis strip 2 to 5 cm thick may be used.
This strip is left proximally based and swung medially.
The remaining vastus lateralis and medialis are then
closed around it. The patient is kept in a cylinder cast for
6 weeks.83
In cases in which large defects occur, as in major
wounds of the anterior aspect of the knee, no quadriceps,
patella, or patellar ligament may exist. The sartorius can be
used as a rotational flap to cover the area.49 The tendon is
freed distally and inserted into the tibial tubercle region.
2039
The advantage of this transfer over a semitendinosus
transfer is muscle bulk. Postoperatively, the patient is
placed in a cylinder cast for 6 weeks.
POSTOPERATIVE REHABILITATION
In all cases, the patient is able to walk in a cylinder cast
during the first several weeks postoperatively. Isometric
quadriceps-setting exercises are not begun until after the
cast is removed (6 weeks). Controlled motion to 45°,
isometric exercises, and straight leg raises are then begun.
One month later, range of motion may be increased to
115°, and strengthening exercises are begun. The third
month should be spent returning the limb to its preinjury
status. The patient should expect that recovery will require
at least 6 months.
Patellar Tendon Ruptures
ACUTE RUPTURES
Patellar tendon rupture occurs most frequently in athletic
patients younger than 40 years; however, it can be observed in patients with systemic illness in which the
collagen structure is weakened.71 This condition is commonly seen in patients with systemic lupus erythematosus,
rheumatoid arthritis, chronic renal failure, diabetes mellitus, and long-term corticosteroid therapy.106 In a younger,
athletic patient, the injury is thought to result from
cumulative microtrauma because the patella more often
fractures when a healthy tendon undergoes acute overload.60 This theory is supported pathologically. Kannus
and Jozsa reported that 97% of 53 patellar tendon ruptures
demonstrated degenerative changes, including hypoxic
tendinopathy, mucoid degeneration, tendolipomatosis, and
calcifying tendinopathy.57
The patellar tendon ruptures most frequently at its
proximal insertion site rather than midsubstance. This
tendency has been hypothesized to result from a relative
decrease in collagen fiber stiffness observed at the insertion
sites of the tendon and from the greater tensile strain
FIGURE 54–29. The Codivilla V-Y–
plasty repair for neglected ruptures
of the quadriceps tendon. A, A distally based V of quadriceps tendon
is developed proximal to the defect.
B, As much of the defect as possible
is closed with nonabsorbable stout
mattress sutures medially and laterally in the retinacula. C, The flap is
turned distally and sutured in place
over the defect in the quadriceps
tendon to restore central continuity. As
much as possible of the defect left by
the V is closed in a proximal-to-distal
direction.
Print Graphic
Presentation
A
B
Copyright © 2003 Elsevier Science (USA). All rights reserved.
C
2040
SECTION V • Lower Extremity
occurring in the insertion fibers than in the midsubstance
fibers.114
The history of the injury almost always consists of an
eccentric quadriceps contraction against the full body
weight. Physical examination of an acute rupture reveals a
hemarthrosis with an inability to extend the knee actively
or maintain a passively extended knee against gravity. A
palpable defect in the tendon itself may be appreciated. In
the case of an isolated tendon rupture with an intact
retinaculum, active extension may be possible, but an
extension lag will be present.71 Over time, a neglected tear
will permit knee extension with subsequent contracture of
the quadriceps tendon and patella.
Radiographically, patella alta will be apparent on a plain
radiograph. Ultrasonography and MRI have been successful in identifying acute and chronic rupture of the patellar
tendon.29, 115
Immediate repair, combined with a wire to relieve stress
from the suture line, is standard treatment of these injuries.62, 72, 79, 94, 106 Although many authors place their
patients in a cylinder cast for 6 weeks postoperatively, the
original purpose of the pull-out wire as described by
McLaughlin and Francis72 was to allow early knee motion.79, 106
Repair
For repair of acute ruptures, a toe-to-groin Esmarch
bandage is applied and then the proximal end is pulled
down. This technique will help bring the patella down. The
tourniquet is inflated and the bandage is removed to
prevent the quadriceps from getting stuck under the
tourniquet.23 A standard midline longitudinal incision is
made. The tendon ends are freshened, and if bony avulsion
has occurred, several holes should be drilled in bone to
allow for strong fixation. Care should be taken when
determining the length of the repair because studies have
shown patellofemoral incongruence to occur when the
length is incorrect.62
An 18-gauge wire should be placed closely along the
medial, superior, and lateral borders of the patella. It
may be attached to the tibia (posterior and slightly distal to the tubercle) through a drill hole or with a bolt
or a screw (see Fig. 54–25). In the latter two cases, a
pull-out wire may be added for removal of the 18-gauge
wire in the office. After the wire has been tightened, an
end-to-end repair with heavy suture is performed. The
tendon may be repaired through three bony tunnels in
the patella with a modified Bunnell-type suture in the
tendinous portion. This construct should be reinforced
by transosseous cerclage as well.71 The torn retinaculum should also be repaired. The repair is then tested in
flexion in the operating room, and any loose sutures are
tightened. Standard closure over a suction drain is then
performed.
Several authors have used fabric material (e.g., Dacron
graft or Mersilene tape) for repair, reinforcement, or
both.38, 62, 65, 66, 77 Levin presented a case with a 5-cm
gap.65 Holes were drilled in the patella and tibia, and
Dacron vascular graft was used to reconstruct the tendon,
with the graft pulled tight for tension. At 15 months, the
repair was still good. Levy and colleagues used Dacron in
place of wire with good results, thus obviating the need for
subsequent wire removal.66 Miskew and co-workers used
5-mm Mersilene tape as suture to augment the primary
repair.77 If the tendon was avulsed from the proximal part
of the patella, holes were drilled into the distal aspect. If
the tendon was avulsed distally, holes were drilled into the
tibia. They reported 10 cases with good results.
Postoperatively, isometric hamstring and quadriceps
exercises are begun immediately, as is toe-touch weight
bearing. At 2 to 3 weeks, active flexion and passive
extension are initiated, with active extension started at
3 to 4 weeks. At 6 weeks, the patient should be at full
weight bearing. Resistance exercises are introduced at 6 to
8 weeks. Competitive sports should be delayed for 4 to
6 months until 90% of isokinetic strength has been
regained.71
CHRONIC RUPTURES
Reconstructions months and years later prove unsatisfactory because of difficulty overcoming contracture and
adhesions. Similar to repair of the quadriceps mechanism,
reconstruction of tendon ruptures can be separated into
quadriceps lengthening, tendon transfers, the use of fascial
or synthetic grafts, or a combination of these techniques.
Tendon Transfers
For late repairs with large patellar tendon defects, the
quadriceps may need to be released from the femur to
translate the patella distally (Fig. 54–30). For severe
long-standing patella alta, extensor mechanism traction is
applied with a Steinmann pin or K-wire placed transversely
through the patella and 5 lb of skeletal traction for several
days to several weeks. Passive range-of-motion exercises
are done during the traction phase to improve postoperative knee motion.94 When lateral radiographs demonstrate
the patella to be correctly positioned, the reconstruction
can be accomplished surgically. Two holes are drilled into
the patella and one oblique hole in the tibia. The semitendinosus and gracilis tendons are released proximally. The
tendons are routed through the tibial hole; then each
tendon is passed into the patella from opposite sides. A
pull-out wire is cerclaged around the proximal part of the
patella or through a transverse bony tunnel and passed
through the tibial tubercle region, the primary repair is
completed, and the wire is tightened. A cylinder cast is
worn for 6 weeks. Isometric exercises are initiated immediately and active range-of-motion and resistance exercises
6 weeks after cast removal.34, 59
A second newly described method for reconstruction of
the extensor mechanism involves the use of a rotational
medial or lateral gastrocnemius flap.63 The muscle belly
can be used for soft tissue coverage, and the tendon can be
used to replace the patellar tendon or even larger portions
of the extensor mechanism that may have been lost. The
proximal portion of the Achilles tendon is sutured to the
patellar or quadriceps tendon remnant, and the distal
portion is sutured to the patellar tendon remnant. A bony
block can even be harvested from the Achilles insertion for
patients with massive loss of the extensor mechanism. A
split-thickness skin graft is used to cover the muscle flap.
Copyright © 2003 Elsevier Science (USA). All rights reserved.
CHAPTER 54 • Patella Fractures and Extensor Mechanism Injuries
2041
Divide
Print Graphic
Gracilis
Semitendinosus
Gracilis
Semitendinosus
Presentation
Twisted
fixation
wire
Fixation
wire
A
B
C
FIGURE 54–30. Late reconstruction of the patellar ligament with the semitendinosus and gracilis tendons (after the method of Ecker). A, The patella is
brought down with traction, and the semitendinosus and gracilis tendons are cut as far proximally as possible. B, These tendons are routed as shown
through drill holes in the patella. Also note the use of a tension band wire through both the patella and tibia. C, The tendons are sutured distally, and
the wire is secured with appropriate tension. (A–C, Modified from Ecker, M.L.; et al. J Bone Joint Surg Am 61:884–886, 1979.)
Synthetic Grafts
Mersilene tape, Dacron graft, and carbon fiber materials
have been advocated in the severe situation in which
local tissues are not available or are of inadequate quality
for substantial repair. More commonly, these materials
have been used to augment primary repair or tendon
transfers.36, 47, 94
Acute Patellar Dislocations
OUTCOMES
LATERAL DISLOCATIONS
Clinical outcome appears to correlate with the interval
between injury and repair. Siwek and Rao reported 80%
excellent and 16% good outcomes in patients treated with
primary repair within 7 days of injury. The results declined
in patients treated 2 weeks or more after injury. This group
had only 33% excellent and 50% good results.94 Larsen
and Lund reported 70% excellent and good results in 10
patients treated acutely for patellar tendon rupture.62
The results of Hsu and colleagues were encouraging as
well.51 Fifty-seven percent and 29% of their 35 patients
treated acutely were rated as excellent and good,
respectively.51 Overall, the literature supports acute
primary repair supplemented with a stress-relieving wire
or nonabsorbable suture as the treatment of choice for
rupture of the patellar tendon.
The mechanism of lateral patellar dislocation is forced
internal rotation of the femur on an externally rotated and
planted tibia with the knee flexed. Tension in the quadriceps pulls the patella laterally. If the medial retinaculum
tears, the patella dislocates over the edge of the lateral
Although recurrent patellar subluxations are a common
cause of knee injury, an acute traumatic patellar dislocation
is a relatively rare event. These injuries are most commonly
manifested as lateral dislocations, but intra-articular and
superior dislocations may occasionally occur.
Print Graphic
Tibial Tubercle Avulsions
Repair of tibial tubercle avulsions, a variant of patellar
tendon avulsions, should incorporate bony reconstruction
with 3.5- or 4.5-mm lag screws and a stress-relieving
wire, if possible, to guarantee accurate tendon length
and patellar tracking. Anchorage may be improved with a
small plate (Fig. 54–31). If the tubercle is comminuted
and the fragments are too small for screw fixation, holes
should be drilled distal and posterior to the avulsion site in
the tibia. Fixation should then proceed as with tendon
avulsions.
Presentation
FIGURE 54–31. Repair of an avulsion fracture of the tibial tubercle can be
made more secure with a small plate. The plate acts as a tension band to
stabilize the head of a lag screw through the avulsed fragment.
Copyright © 2003 Elsevier Science (USA). All rights reserved.
2042
SECTION V • Lower Extremity
femoral condyle. Such dislocation results in shearing
between the medial inferior edge of the patella and the
lateral femoral condyle.78 Osteochondral fractures in these
areas strongly suggest a lateral patellar dislocation, with the
former having an incidence of 5%.78, 85
comfort permits, usually over another 3 weeks. If an
osteochondral fragment is suspected, diagnostic arthroscopy is recommended, and if a fragment is present,
operative repair or excision is warranted.
Diagnosis
A patient with an unreduced lateral patellar dislocation will
have a large lateral mass, hemarthrosis, medial retinacular
pain, and an inability to flex the knee. An attempt should
be made to reduce the patella on evaluation to decrease the
patient’s discomfort. Standard radiographs are then taken,
including a tangential view to rule out osteochondral
fractures.78 If the bony portion of the osteochondral
fragment is small, the lesion may be missed on radiographs. For this reason, as well as for comfort, arthrocentesis is performed. If blood from the hemarthrosis contains
fat globules on aspiration, an osteochondral fracture
should be considered.4, 78, 85
If the patella is already reduced, diagnosis of an acute
traumatic dislocation will be made more difficult inasmuch
as medial joint pain and an effusion may be the only
findings. This diagnosis is important to make because
osteochondral fractures must be ruled out. Common
symptoms associated with osteochondral fragments include blocking, locking, giving way, and tenderness to
palpation on the medial side of the knee that is not
meniscal or ligamentous in origin.78
INTRA-ARTICULAR DISLOCATIONS
Treatment
Treatment of an acute lateral patellar dislocation consists of
reduction and extension casting for 3 to 6 weeks. Cofield
and Bryan evaluated 50 patients treated conservatively in
extension casts with a follow-up period of 5 years or until
operative reconstruction was needed. Patient age, sex, the
mechanism of injury, and the length of time spent in a cast
had no effect on outcome.26 Although a third of their
patients were considered treatment failures, they concluded that initial surgery for acute patellar dislocations
was not warranted except in cases with displaced intraarticular fractures exclusive of the medial border.26 We
agree with these recommendations.
Larsen and Lauridsen studied the incidence of redislocation after conservative treatment of 79 acute patellar
dislocations.61 Treatment included a cylinder cast in 22
patients and an elastic wrap in 57 patients. The clinical
results and the tendency to redislocate were independent
of the treatment method. The risk of redislocation was
statistically significantly less in patients older than 20 years
at the time of the first episode of dislocation. The authors
stressed initial conservative treatment and quadricepsstrengthening exercises, with realignment procedures considered only if the dislocation recurred.
In Morscher’s series of 34 osteochondral fractures of the
knee, the fracture was caused by an acute lateral dislocation
of the patella in 21 of the 34 fractures (62%).78 Sixteen
were found on the medial edge of the patella, 1 on the
lateral femoral condyle, and 4 on both surfaces. Operative
treatment was chosen in all cases.
Currently, we recommend conservative treatment with a
cast or brace in extension for ambulation for 3 weeks.
Flexion can then be progressively increased as the patient’s
Though rare, intra-articular or horizontal dislocations of
the patella usually occur in adolescent boys.80 In these
dislocations, the patella is violently ripped off the quadriceps tendon and rotated around its horizontal axis such
that the proximal part of the patella becomes stuck within
the intercondylar notch. The knee is slightly flexed, and the
quadriceps tendon is intact.15, 37, 80, 98 Treatment consists
of closed manipulation under anesthesia and extension
casting for 6 weeks with quadriceps exercises. Healing is
usually uneventful.15, 37, 80, 98, 113
SUPERIOR DISLOCATIONS
Four cases of superior patella dislocation exist in the
literature.46, 113 The injury occurs in an older population
and results from hyperextension of the knee with the
patella locked on a femoral osteophyte. Gentle manipulation in the emergency room is all that is usually required.46, 113
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