HOW-TO SESSION How to Perform a Standardized Ultrasonographic Examination of the Equine Stifle Michel Hoegaerts, DVM; and Jimmy H. Saunders, DVM, PhD, CertVR, DipECVDI Authors’ address: Department of Medical Imaging, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium. © 2004 AAEP. 1. Introduction Injuries of the equine stifle are frequent causes of hind limb lameness.1–9 Diagnostic intra-articular anesthesia and scintigraphy can be used to localize the lameness, but these techniques do not give a definitive diagnosis. Radiography may provide a definitive diagnosis, but it offers little information on soft tissue structures. Ultrasonography (US) has a high resolution for the evaluation of soft-tissue structures. It has been proven to be useful for the diagnosis of stifle injuries.10 –18 However, performing a US examination of the equine stifle requires a systematic approach and an adequate knowledge of the cross-sectional anatomy of this joint. The aim of this study was to establish a protocol for the standardized and systematic US examination of the equine stifle and to evaluate its usefulness in horses suspected of stifle joint disease. 2. Materials and Methods Nine hind limbs of horses euthanized for gastrointestinal disease were used. The animals had no history of orthopedic problems. Body weight ranged from 350 to 400 kg. The limbs were properly prepared by clipping the hair, washing the skin with hot water, and applying acoustic gel. The ex- NOTES 212 2004 Ⲑ Vol. 50 Ⲑ AAEP PROCEEDINGS aminations were performed with a linear 6- to 9-MHz transducer, a convex 4- to 6-Mhz transducer,a and a linear 7- to 12-MHz matrix transducer.b A protocol was established in five steps (a “five-step-tour”) for a complete standardized US examination of the equine stifle based on a systematic approach. First, the medial femorotibial joint (MFT; step I), the femoropatellar joint (FP; step II), and the lateral femorotibial joint (LFT; step III) were evaluated while the leg was bearing weight. Second, the joint was flexed 90° for the evaluation of the femoral condyles, the cranial meniscotibial ligaments (MTL), the tibial attachment of the cranial cruciate ligament (CrXL), and the femoral attachment of the caudal cruciate ligament (CdXL; step IV). Third, the evaluation of the caudal parts of the MFT, LFT, and the tibial attachment of the CdXL (step V) was done while the leg was bearing weight. Through every step, the movement of the transducer is described using anatomical landmarks. ● 1. Step I: MFT while the leg was bearing weight (Fig. 1) Palpate the medial collateral ligament (MCL), HOW-TO SESSION Fig. 3. Reference US picture of the MFT, craniomedial approach. Left, proximal; right, distal; 1, MFC; 2, medial tibial condyle; 3, fat; MFT REC, medial recess of the MFT. Fig. 1. Step I: US examination of the MFT. 1, 2, and 3: evaluation of the intermediate, craniomedial, and caudomedial part of the MM, respectively. Fig. 2. Reference US picture of the MFT, medial approach. Left, proximal; right, distal; 1, MFC; 2, medial tibial condyle; 3, medial collateral ligament. place the transducer on the ligament in a vertical plane, and scan the MCL and the medial meniscus (MM) with the US beam perpendicular to the fibers. Move proximally and distally to scan the femoral and tibial attachments of the MCL and its connection to the MM. Evaluate the articular margins of the femoral condyle and the tibial plateau (Fig. 2). 2. Move cranially to visualize the craniomedial part of the MM and tilt the transducer in a craniomedial-caudolateral direction to have the US beam perpendicular to the fibers of Fig. 4. Step II: US examination of the FP. 1, evaluation of lateral (LR) and medial trochlear ridge (MR) of the femur; 2a, 2b, and 2c, evaluation of the middle, lateral, and medial patellar ligament, respectively. the MM. The medial recess of the MFT is proximal to the MM between the MCL and the medial patellar ligament (MPL). This recess contains fluid in clinically normal horses (Fig. 3). 3. Scan again the craniomedial part of the MM, pass the MCL, and scan the caudomedial of the MM. Tilt the transducer in a caudomedial-craniolateral direction to have the US beam perpendicular to the fibers of the MM. AAEP PROCEEDINGS Ⲑ Vol. 50 Ⲑ 2004 213 HOW-TO SESSION Fig. 5. Reference US picture of the FP, cranial approach. Left, lateral; right, medial; lr, lateral trochlear ridge; mr, medial trochlear ridge; s, sulcus; midpl, middle patellar ligament; cart, cartilage of the lr. Fig. 7. Reference US picture of the LFT, lateral approach. Left, proximal; right, distal; 1, lateral femoral condyle; 2, lateral tibial condyle; LCL, lateral collateral ligament; LM, lateral meniscus; POP, popliteal tendon. lear groove (Fig. 5). The lateral patellar ligament (LPL) is cranial to the lateral trochlear ridge, and the MPL is medial to the medial trochlear ridge. Scan each ligament from proximal to distal. Evaluate its fiber structure and its patellar and tibial attachments. The patellar attachment of the MPL bends 90° and attaches to the medial parapatellar fibrocartilage. Close to the distal part of the MIDPL, the cranial recess of the LFT can be visualized if distension of the joint is present. Fig. 6. Step III: US examination of the LFT. LM, lateral meniscus; 1, 2, and 3, evaluation of the intermediate, craniolateral, and caudolateral part of the LM, respectively. ● Step II: FP with the leg bearing weight (Fig. 4) 1. With a horizontal approach, locate the medial and lateral ridges of the femoral trochlea. Scan each ridge from proximal to distal. Evaluate the subchondral bone, the articular cartilage, and the synovial membrane. The lateral and medial recesses of the FP are lateral and medial to the lateral and medial trochlear ridge, respectively. 2. With a horizontal approach, locate the middle patellar ligament (MIDPL) in the troch214 2004 Ⲑ Vol. 50 Ⲑ AAEP PROCEEDINGS ● Step III: LFT with the leg bearing weight (Fig. 6) 1. Palpate the lateral collateral ligament (LCL), place the transducer on this ligament in a vertical plane, and scan the LCL and the HOW-TO SESSION Fig. 8. Reference US picture of the LFT, craniolateral approach. Left, proximal; right, distal; fossa ext, extensor fossa of the femur; sulcus ext, extensor sulcus of the tibia; js, joint space; m. ext long, extensor digitorum longus muscle; per tert, peroneus tertius muscle. lateral meniscus (LM) with the US beam perpendicular to the fibers. Move proximally and distally and scan the femoral and fibular attachment of the LCL. The popliteal tendon is between the LM and LCL (Fig. 7). Evaluate the articular margins of the femoral condyle and the tibial plateau. 2. Move cranially to visualize the craniolateral of the LM and tilt the transducer in a craniolateral-caudomedial direction to have the US beam perpendicular to the fibers of the LM. Evaluate the tendon of the peroneus tertius and extensor digitorum longus muscle and the subextensor recess of the LFT between the LCL and LPL at the level of the sulcus extensoris of the tibia (Fig. 8). This recess does not contain fluid in clinically normal horses. 3. Scan again the craniolateral part of the LM, pass the LCL, and scan the caudolateral of the LM. Tilt the transducer in a caudolateral-craniomedial direction to have the US beam perpendicular to the fibers of the meniscus. ● 1. Step IV: cranial approach with the flexed leg (90°) (Fig. 9) Palpate the medial femoral condyle (MFC) between the MPL and MIDPL and place the transducer on the condyle in a vertical plane. Examine the cartilage and subchondral bone of the MFC (Fig. 10). Go distally and visualize the cranial part of the MM (Fig. 11). Move laterally, turn the transducer 70° counterclockwise (left limb), and visualize the MTL and its tibial attachment (Fig. 12). With the convex transducer in a verti- Fig. 9. Step IV: US examination of the cranial part of the medial (MM) and lateral meniscus (LM) and its related structures with the leg in flexion. 1 and 2, the cranial meniscotibial ligaments are visualized by sliding the transducer axially. cal plane at the level of the MIDPL, visualize the tibial attachment of the CrXL, tuning the transducer 20° clockwise (left limb), lateral to the MTL and the medial intercondylar eminence of the tibia. With the transducer in the same position, visualize the femoral attachment of the CdXL in the intercondylar fossa of the femur (Fig. 13). 2. With the convex transducer in a vertical plane and lateral to the LPL, examine the AAEP PROCEEDINGS Ⲑ Vol. 50 Ⲑ 2004 215 HOW-TO SESSION Fig. 10. Reference US picture of the MFC with the leg in flexion, cranial approach. Left, proximal; right, distal; 1, subchondral bone of the MFC; 2, cartilage of the MFC. Fig. 12. Reference US picture of the cranial MTL of the medial meniscus (MM) with the leg in flexion, cranial approach. Left, lateral; right, medial; 1, MTL of the MM; 2, tibia; 3, medial patellar ligament. Fig. 11. Reference US picture of the cranial part of the medial meniscus (MM) with the leg in flexion, cranial approach. Left, proximal; right, distal; 1, MFC; 2, medial tibial condyle; 3, cranial part of the MM. cartilage and subchondral bone of the lateral femoral condyle (LFC) through the tendon of the extensor digitorum longus muscle. Go distally and visualize the cranial part of the LM. Move the transducer medially and turn it 70° clockwise to visualize the MTL of the LM and its tibial attachment. ● Step V: caudal approach with the leg bearing weight (Fig. 14). With the US beam in a vertical plane and a caudo-cranial direction, visualize the caudal part of the MFC, the caudal part of the MM, the synovial membrane, and the caudal recess of the MFT through the caudal muscles of the stifle. Visualize the tibial attachment of the CdXL lateral to the MFC. 2. With the US beam in a vertical plane and a caudo-cranial direction, visualize the caudal Fig. 13. Reference US picture of the cranial cruciate ligament (CrXL) with the leg in flexion, cranial approach. Left, proximal; right, distal; 1, intercondylar fossa of the femur; 2, tibia; 3, CrXL; 4, caudal cruciate ligament. part of the LFC, the caudal part of the LM, the synovial membrane, and the popliteal recess of the LFT through the caudal muscles of the stifle. Visualize the meniscofemoral ligament medially to the LFC in an oblique plane (30° clockwise for the left leg). 1. 216 2004 Ⲑ Vol. 50 Ⲑ AAEP PROCEEDINGS This “five-step-tour” was applied to 20 horses suspected of stifle pathology. The limbs were properly prepared by clipping the hair, washing the skin with hot water, and applying acoustic gel. The examination was performed in all horses with a linear 6- to 9-MHz transducer and a convex 4- to 6-MHz transducer.a Five horses had a meniscal tear, collapse, or mineralization of the MM; 1 horse had a caudal HOW-TO SESSION medial MTL, and the CdXL were visualized. The visualization of the cranial part of the LM and the lateral MTL were less obvious because these structures are covered by the tendon of the extensor digitorum longus muscle. The tibial attachment of the CrXL was always anechoic because the fibers could not be orientated perpendicular to the US beam because of their oblique orientation. On step V, the visualization of the femoral condyles and the caudal parts of both menisci depended on the thickness of the thigh. Because of the complex topographical anatomic orientation, the tibial attachment of the CdXL was difficult to visualize, and the MFL was impossible to see. 4. Fig. 14. Step V: 1 and 2, US examination of the caudal parts of the medial (MM) and lateral meniscus (LM), respectively. prolapse of the MM; 1 horse had an avulsion fracture of the tibial attachment of the CdXL; 4 horses had a desmitis of the MCL or LCL; 5 horses had osteochondrosis of the lateral and/or medial trochlear ridge; 13 horses had a synovitis of the MFT, LFT, and/or FP; and 4 horses had patellar ligament desmitis. 3. Results A protocol was established, allowing visualization of the main soft tissue structures of the stifle joint. The protocol divided the examination of the stifle in five steps based on the anatomy of the stifle joint (three compartments, large muscular mass caudally) and the position of the leg (weight-bearing or flexed). The more consistent features were an easier and better visualization of the MM compared with the LM and a lesser organized proximal attachment of the MCL compared with the proximal attachment of the LCL. The visualization of the LM and the caudomedial part of the MM was consistently better with the convex transducer. On the 20 living horses, steps I–III allowed an appropriate visualization of all the anticipated structures in all horses. The approach with the leg in flexion (step IV) was difficult because the flexion was only well tolerated for 3–5 min. Moreover, the topographical anatomy is complicated. If the horse permitted us to evaluate the stifle joint in flexion, the femoral condyles, the cranial part of the MM, the Discussion Most US images of the equine stifle joint may be obtained using a linear transducer with a frequency ranging from 7 to 12 MHz, although for the deeper structures, a 4- to 6-MHz convex transducer must be used. Initially, the evaluation of all the structures of the stifle joint may be overwhelming for a moderately trained practitioner. Initially, practitioners may choose to perform routinely steps I (MFT), II (FP), and III (LFT) of the protocol. When comfortable with these, steps IV and V of the protocol can be added to the examination. However, even with appropriate training, some structures, such as the CdXL, can not always be correctly visualized. US of the equine stifle still represents a technical challenge. However, with an appropriate knowledge of the cross-sectional anatomy, a standardized protocol, and sufficient training, the practitioner will be able to investigate the equine stifle US at an appropriate level. References and Footnotes 1. Butler JA, Colles CM, Dyson SJ, et al. The stifle and tibia. In: Clinical radiology of the horse. Oxford: Blackwell Science, 2000;285–326. 2. Dyson SJ. Stifle trauma in the event horse. Equine Vet Educ 1994;6:234 –240. 3. Jeffcott LB, Kold SE. Radiographic examination of the equine stifle. Equine Vet J 1982;14:25–30. 4. Jeffcott LB, Kold SE. Stifle lameness in the horse: a survey of 86 referred cases. Equine Vet J 1982;14:31–39. 5. Jeffcott LB. Interpreting radiographs 3: radiology of the stifle joint of the horse. Equine Vet J 1984;16:81– 88. 6. McIlwraith CW. Osteochondral fragmentation of the distal aspect of the patella in horses. Equine Vet J 1990;22:157– 163. 7. Sanders-Shamis M, Bukowiecki CF, Biller DS. Cruciate and collateral ligament failure in the equine stifle: seven cases (1975–1985). J Am Vet Med Assoc 1988;193:573–576. 8. Tietje S. Die Computertomographie im Kniebereich des Pferdes: ein Vergeleich met der ro¨ntgenologischen, sonographischen und arthroskopischen Untersuchung. Pferdeheilkunde 1997;13:647– 658. 9. Walmsley JR, Phillips TJ, Townsend HG. Meniscal tears in horses: an evaluation of clinical signs and arthroscopic treatment of 80 cases. Equine Vet J 2003;35:402– 406. 10. Busoni V. Ultrasonographic assessment of cranial meniscal ligaments in the horse, in Proceedings. European Association of Vet Diagnostic Imaging 2003:39. 11. Cauvin ER, Munroe GA, Boyd JS, et al. Ultrasonographic examination of the femorotibial articulation in horses: imAAEP PROCEEDINGS Ⲑ Vol. 50 Ⲑ 2004 217 HOW-TO SESSION 12. 13. 14. 15. 218 aging of the cranial and caudal aspects. Equine Vet J 1996; 28:285–296. Denoix JM. Ultrasonographic examination of the stifle in horses, in Proceedings. Annual Meeting of the ACVS 2003: 122. Denoix JM, Lacombe V. Ultrasound diagnosis of meniscal injuries in horses. Pferdeheilkunde 1996;12:629 – 631. Dik K. Ultrasonography of the equine stifle. Equine Vet Educ 1995;7:154 –160. Dyson SJ. Normal ultrasonographic anatomy and injury of the patellar ligaments in the horse. Equine Vet J 2002;34: 258 –264. 2004 Ⲑ Vol. 50 Ⲑ AAEP PROCEEDINGS 16. McIlwraith CW, Trotter GW. Joint disease in the horse. Philadelphia: Saunders, 1996. 17. Penninck DG, Nyland TG, O’Brien TR, et al. Ultrasonography of the equine stifle. Vet Radiol Ultrasound 1990;31: 293–298. 18. Reef VB. Equine diagnostic ultrasound. Philadelphia: Saunders, 1998. a Logiq 200 pro, General Electric Medical Systems, Milwaukee, WI 53207. b Logiq 7, General Electric Medical Systems, Milwaukee, WI 53207.
© Copyright 2024