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Stifle Joint Anatomy and Surgical Approaches in the Dog
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STIFLE SURGERY
STIFLE JOINT ANATOMY AND SURGICAL APPROACHES IN THE DOG John T. Payne, DVM, MS and Gheorghe M. Constantinescu, DVM, PhD, Drhc
Surgical diseases involving the stifle joint are among the most common causes of canine pelvic limb lameness. Developmental diseases such as patellar luxation and osteochondrosis of the femoral condyles, and traumatic and degenerative diseases such as rupture of the cranial cruciate ligament or primary degenerative joint disease are seen frequently in small animal practices. Thorough knowledge of stifle anatomy and surgical approaches is imperative for effective diagnosis and treatment of diseases of this joint. ANATOMY
The stifle is a complex diarthrodial joint that allows flexion and extension as well as axial and lateral movements. 1• 7• 8 The stifle joint consists of three components that freely interconnect: the femorotibial joint (between the femoral and tibial condyles), the femoropatellar joint (between the articular surface of the patella and femoral trochlea), and the proximal tibiofibular joint. 1• 2• 4• 7• 8 The femorotibial joint is partially occupied by the lateral and medial menisci. The menisci are C-shaped wedges of fibrocartilage that function to improve joint congruency and absorb compressive forces across the joint. The fibrous joint capsule of the stifle is visibly present only on the caudal aspect; no fibrous joint capsule is present cranial to the collateral ligaments of the femorotibial joint except for the femoropatellar ligaments. The synovial joint capsule is the largest joint capsule in the body and consists of three sacs that all intercommunicate.• Two of these sacs are between the lateral and From the Department of Veterinary Medicine and Surgery (JTP), and the Department of Veterinary Biomedical Sciences (GMC), University of Missouri College of Veterinary Medicine, Columbia, Missouri VETERINARY CLINICS OF NORTH AMERICA: SMALL ANIMAL PRACTICE VOLUME 23 • NUMBER 4 • JULY 1993
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medial femoral and tibial condyles. The third sac is the patellar pouch, which extends laterally from the parapatellar fibrocartilages to attach to the femur approximately 2 em from the trochlear ridges.• Proximally, the femoropatellar synovial capsule extends 1.5 em from the patella under the tendon of the quadriceps femoris muscle.• There is no distinct separation between the patellar and condylar sacs of the synovial capsule. Distal to the patella, the fibrous (patellar retinacula) and synovial portions of the joint capsule are separated by the infrapatellar fat pad that occupies the triangular space distal to the femur, proximal to the tibia, and caudal to the patellar ligament. 4 The femorotibial joint space is further divided into the femoromeniscal and tibiomeniscal portions by the menisci. The stifle is surrounded by four ligaments that provide excellent stability and allow for flexion, extension, limited varus and valgus angulation, limited craniocaudal movement, and axial rotation. Each ligament has specific functions and neutralizes specific forces acting on the stifle. The cranial cruciate ligament (CrCL) is located intra-articularly; it originates on the caudomedial part of the lateral femoral condyle and inserts on the cranial intercondyloid area of the tibial plateau.• The CrCL serves mainly to prevent abnormal cranial-caudal movement, but also provides rotational stability preventing excessive internal rotation of the stifle. A final function of the CrCL is to prevent hyperextension of the joint.' The canine CrCL is composed of two main portions: the craniomedial band and the caudolateral bond. The craniomedial band is taut throughout flexion and extension, whereas the caudolateral band is taut only during extension. 7 The caudal cruciate ligament (CaCL) is located intra-articularly originating on the lateral surface of the medial femoral condyle and inserting on the lateral edge of the popliteal notch of the tibia.• The CaCL is longer and heavier than the cranial cruciate ligament. Like the CrCL, it serves mainly to stabilize cranialcaudal movement. As the name implies, the two cruciate ligaments cross each other in the joint and provide rotational stability by wrapping around each other. The CaCL is also a secondary restraint against hyperextension of the stifle joint. The CaCL is also composed of two parts: a cranial and a small caudal band. The cranial band is taut in flexion and loose in extension, whereas the caudal band is taut in extension and loose in flexion.' The medial collateral ligament (MCL) originates on the medial femoral epicondyle and inserts on the medial border of the tibia just distal to the medial tibial condyle. This ligament fuses with both the joint capsule and the medial meniscus, and is responsible primarily for maintaining valgus stability. The MCL also serves as a secondary restraint against rotational instability. The lateral collateral ligament (LCL) originates from the lateral femoral epicondyle and inserts into the head of the fibula (Fig. 1). The lateral collateral ligament does not fuse with the lateral meniscus. The LCL courses distally and crosses laterally to the tendon of the popliteal muscle. The LCL is primarily responsible for maintaining varus stability, and serves as a secondary constraint against rotation instability. The LCL is also responsible for the "screw home" mechanism of the stifle joint. As the stifle joint flexes, the LCL becomes lax allowing internal rotation of the tibia relative to the femur. Following the swing phase of the step, the stifle will again begin to extend, the LCL will become taut, and the tibia will externally rotate or screw home. 7 The lateral and medial menisci are composed of fibrocartilage and occupy the space between the adjacent lateral and medial femoral and tibial condyles respectively. Positioned in the joint with the concave side facing axially, the menisci are thicker in their periphery than they are axially. The menisci are
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Figure 1. Anatomic dissection of the lateral aspect of the stifle demonstrating important structures and surgical landmarks. A = Vastus lateralis; B = lateral collateral femorotibial ligament; C = patella; D = long digital extensor tendon; E = lateral meniscus; F = biceps femoris (reflected); G = common peroneal nerve; H = lateral sesamoid of the gastrocnemius; I = popliteus tendon; J = gastrocnemius; K == flexor hallucis longus; L = fibularis (peroneus) longus; M = tibialis cranialis.
firmly held in place by six ligaments; namely, the craniolateral and craniornedial rneniscotibial ligaments, the caudolateral and caudornedial rneniscotibial ligaments, the interrneniscal ligament, and the rneniscofernoral ligament (lateral meniscus). Both menisci are firmly attached to the joint capsule. The medial meniscus is attached to the MCL. The menisci receive nutrients largely through the synovial fluid; however, there is blood supply to the peripheral10% to 15% supplied through the synovial membrane. 2 The menisci are important in the normal function of the stifle joint. They transmit approximately 65% of the weight across the stifle joint, and are important in maintaining craniocaudal and rotational stability. 7 The menisci are also important in increasing the efficiency of stifle joint lubrication, and in preventing synovial entrapment.' The two tendons located within the stifle joint are the tendons of the long digital extensor and of the popliteal muscles (Fig. 1). The tendon of the long digital_ extensor originates on the extensor fossa, between the lateral femoral condyle and the lateral ridge of the femoral trochlea, and is ensheathed by the synovial membrane for a distance of 3 to 4 ern. The tendon of the popliteal muscle originates on the popliteal fossa of the distal lateral condyle of the femur just caudal to the origin of the long digital extensor tendon, and passes caudally deep to the lateral collateralligarnent. The main blood supply to the stifle is the descending genicular artery that arises from the femoral artery distal to the origin of the saphenous artery. 5 This artery supplies the medial femorotibial and fernoropatellar joint capsule. The medial joint capsule also receives blood from the genicular articular branch of the saphenous artery. 3 The caudal genicular arteries arise from the popliteal artery and supply the joint capsule caudal to the collateral and cruciate ligaments. The blood supply to the lateral joint capsule is through the lateral proximal genicular artery that arises from the distal caudal femoral artery. The
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genicular articular rete supplies the distal lateral and medial aspect of the femorotibial and femoropatellar joint. 3 Innervation to the stifle is through the branches of the tibial and common peroneal nerves. The peroneal nerve receives sensory information from both the lateral joint capsule and the lateral collateral ligament. 6 LATERAL APPROACH
The lateral approach to the stifle joint is the most commonly used surgical approach to this joint in the dog and cat. It is used most frequently to reconstruct injuries to the cranial and caudal cruciate or to lateral collateral ligaments and to replace luxating patellae. It is also used to repair some intra-articular fractures and other less common injuries such as long digital extensor or popliteal tendon injuries. The lateral approach to the femur is performed with the patient positioned in lateral recumbency on the contralateral side of the approach, and the leg is hung for standard surgical preparation. After appropriate draping, a curvilinear incision is made on the lateral aspect of the femur extending from the distal one third to one half of the femur to a point 1 to 2 em distal to the tibial tuberosity (Fig. 2). This incision approximately follows the cranial border of the biceps femoris muscle proximally and a line 1 to 2 em lateral to the patella and patellar ligament distally. Small bleeding vessels in the dermis are controlled with electrocoagulation, and the fascia of the biceps femoris (the superficial layer of the fascia lata) and the lateral retinaculum are incised along a similar line (Fig. 3). If performing r~pairs using the lateral sesamoid bone of the gastrocnemius muscle (formerly fabella), the biceps fascia can be undermined and reflected caudally at this time. At the proximal end of the incision,
Figure 2. Lateral aspect of left stifle demonstrating location of skin incision (line). A = Patella; B = tibial tuberosity; Cr = cranial; Ca = caudal.
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Figure 3. Lateral aspect of left stifle after reflection of fascia lata. A = Fascia lata; B = lateral proximal genicular artery; C = lateral femoropatellar ligament; D = patella; E = stifle joint capsule; F = patellar ligament; G = vastus lateralis; H = biceps femoris (surrounded by superficial and deep fascia lata); I = gastrocnemius; J = lateral collateral ligament; K = aponeurosis of biceps femoris.
the vastus lateralis can be undermined from its caudal edge, and retracted cranially to expose the femoropatellar joint capsule (Fig. 4). It is preferable to reflect the vastus lateralis rather than to incise the muscle fibers. The joint CClpsule is exposed and incised along the lateral aspect of the trochlear margin. The joint capsule incision is then extended to its proximal extent using Mayo
Figure 4. Lateral aspect of left stifle demonstrating elevation and retraction of vastus lateralis to expose proximal joint capsule. A = Vastus lateralis; B = femoropatellar joint capsule; C = lateral femoropatellar ligament; D = biceps femoris (covered by superficial fascia lata); E = lateral proximal genicular artery; F = gastrocnemius; G lateral collateral ligament.
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Figure 5. Lateral aspect of left stifle demonstrating incision of the joint capsule. A = Vastus lateralis; B = aponeurosis of vastus lateralis; C = femoral trochlea; D = patella; E = tendon of long digital extensor; F = femoropatellar joint capsule; G = gastrocnemius; H = lateral femoropatellar ligament; I = lateral collateral ligament; J = popliteus tendon; K = aponeurosis of the biceps femoris.
dissection scissors. The femoropatellar joint capsule incision is extended distally, including the lateral femoropatellar ligament and the lateral patellar retinaculum, to expose the intra-articular femorotibial structures. One must be cautious not to inadvertently incise the long digital extensor tendon over the distal aspect of the femur. (Fig. 5). Once the joint is opened, the patella is luxated medially, and the infrapatellar fat pad is retracted distally using a sharp-pointed Senn retractor. The intra-articular structures are then examined. Additional exposure to examine the caudal horn of the medial meniscus in
Figure 6. Lateral aspect of left stifle demonstrating the intraarticular exposure. A = Hohmann retractor; B = medial meniscus; C = joint capsule (cut); D = lateral femoropatellar ligament (cut); E = long digital extensor tendon; F = cranial cruciate ligament; G = infrapatellar fat pad.
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Figure 7. Medial aspect of right stifle demonstrating location of the skin incision (line). A = Patella; B = tibial tuberosity; Cr = cranial; Ca = caudal.
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patients with CrCl ruptures can be obtained by placing a Hohmann retractor through the intercondylar space of the femur, and hooking the caudal aspect of the tibial plateau (Fig. 6). The Hohmann retractor used in this fashion causes cranial displacement of the tibia with respect to the femur, increasing the exposure of the caudal horns of the menisci. After the intra-articular sequence of the procedure is completed, the joint capsule is closed with an absorbable suture material in a simple interrupted pattern. The biceps femoris fascia is then brought cranially and closed using a simple interrupted or Mayo imbri-
Figure 8. Medial aspect of right stifle demonstrating the deeper dissection and joint capsule incision. A = Sartorius cranialis protected by lamina femoralis; B = attachment of vastus medialis; C = medial femoropatellar ligament; D = medial femoral condyle; E = patellar ligament; F = tibial tuberosity; G = vastus medialis; H = medial meniscus; I = medial collateral ligament; J = medial tibial condyle.
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Figure 9. Medial aspect of right stifle demonstrating exposure of intraarticular structures. A = Tendon of long digital extensor; B = lateral femoral condyle; C = patellar ligament; 0 = Senn retractor; E = cranial sartorius; F = caudal sartorius; G = vastus medialis; H = cranial cruciate ligament; I = caudal cruciate ligament; J = medial meniscus; K = infrapatellar fat pad.
eating suture pattern depending on the objectives of the closure. The subcutaneous · tissues are closed using a simple continuous pattern, and the skin is closed using a simple interrupted pattern. Occasionally access is needed to the caudolateral compartment of the stifle joint to repair ruptures of the popliteal tendon, to retrieve osteochondral
B
Figure 10. Cranial aspect of right stifle demonstrating bilateral arthrotomy incisions. A = Patella; B = lateral femoropatellar ligament (cut); C = patellar ligament; 0 = tibial tuberosity; E = cranial sartorius; F = vastus medialis; G = medial femoropatellar ligament (cut); H = medial ridge of femoral trochlea; I = caudal sartorius.
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fragments in stifle osteochondrosis, or to repair some fractures . Access is provided through a variation of the lateral approach to the stifle joint as described above. The skin incision is extended 3 to 5 em distally to the tibial tuberosity, and the biceps femoris is reflected caudally as in the lateral approach. One must note the position of the peroneal nerve and protect it from injury (see Fig. 1). To visualize the caudolateral compartment of the joint, the lateral head of the gastrocnemius muscle is elevated and retracted caudally. The popliteus muscle is partially elevated and retracted distally exposing the caudal joint capsule. The joint capsule is opened with a transverse incision exposing the caudal structures of the joint. Closure is performed as described above. MEDIAL APPROACH
The medial approach to the stifle joint is used less commonly than the lateral approach; generally, the two approaches are used to treat similar problems. The medial approach makes exposure of the lateral sesamoid bone of the gastrocnemius (fabella) more difficult during extra-articular stifle stabilization procedures; however, it is occasionally used in dogs when the owners are particularly apprehensive about a visible scar on the leg. The medial approach is preferred when repairing fractures involving the medial femoral condyle or ruptures of the medial collateral ligament of the femorotibial joint. The patient is positioned in dorsal recumbency with the leg hung. The patient's skin is prepared and draped in an appropriate manner. The skin incision for the medial approach to the stifle extends from the distal one third to one half of the femur to a point 1 to 2 em distal to the tibial tuberosity (Fig.
Figure 11. Craniolateral aspect of right stifle following osteotomy of tibial tuberosity and proximal reflection of quadriceps muscles. A = Tibial tuberosity (cut surface) B = patella (articular surface); C = parapatellar fibrocartilages; D = vastus intermedius; E = vastus lateralis; F = tendon of long digital extensor; G = tibialis cranialis (partially elevated); H = cranial sartorius; I = rectus femoris; J = vastus medialis; K = femoral trochlea; L = cranial cruciate ligament; M = caudal cruciate ligament; N = medial femoral condyle; 0 = infrapatellar fat pad.
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7). The subcutaneous tissue is incised along a similar line, and electrocoagulation is used to control hemorrhage. The deep fascia is then incised along the same line, and the cranial belly of the sartorius is elevated and retracted cranially. A parapatellar incision is continued through the medial femoropatellar ligament and the medial patellar retinaculum 1 to 2 em medial to the patella and patellar ligament and continued deep to the synovial membrane. This incision splits the fibers of the vastus medialis, which is closely associated with the medial retinaculum (Fig. 8). The cranial belly of the sartorius muscle may also be split in the direction of its fibers for a distance of 1 to 2 em at the proximal end of the incision, although this is unnecessary in most cases. 9 The articular cavity is then opened, and the patella is luxated laterally. Exposure of intra-articular structures is gained in a similar fashion as for the lateral approach (Fig. 9). Closure is accomplished in layers as in the lateral approach. TIBIAL TUBEROSITY OSTEOTOMY APPROACH
The tibial tuberosity osteotomy approach to the stifle is used to repair multiple intra-articular fractures of the femoral condyles or to perform stifle arthrodesis. 9 The patient is positioned in dorsal recumbency, and the leg is hung and prepared for aseptic surgery. After proper draping, a curvilinear incision is made over the cranial aspect of the stifle joint. The incision begins on the lateral aspect of the distal one third of the femur, and crosses the midline at the center of the patellar ligament. The incision continues distally on the craniomedial aspect of the tibia. 9 A medial and lateral arthrotomy are performed by incision of the fasciae, patellar retinacula, and synovial capsules bilaterally. The arthrotomies are extended distally to the tibial tuberosity so that the patellar ligament is isolated (Fig. 10). An osteotome and mallet are then used to remove the tibial tuberosity with its attached patellar ligament. Care must be taken to include a large enough piece of bone in the osteotomy for adequate stabilization during closure. Following osteotomy, the quadriceps muscles are reflected proximally until adequate exposure is achieved to perform the procedure (Fig. 11). After completion of the procedure, the tibial tuberosity is reattached using two Kirschner wires and a tension band wire. The lateral and medial patellar retinacula, synovial capsules, and fasciae are closed identically to the lateral and medial approach described previously, and the rest of the tissues are closed routinely in layers. SUMMARY
This article reviewed the pertinent anatomy and surgical approaches of the canine stifle joint. Anatomically correct approaches to this joint provide for relatively atraumatic entry into the joint, while providing adequate exposure to complete the intra-articular parts of the surgical procedure. Atraumatic surgical exposures provide for less postoperative pain and a better outcome to any surgical procedure. References 1. Barone R: Articulations de Ia ceinture et du membre pelviens. I!J Anatomie Comparee
des Mammiferes Domestiques. Lyon, Laboratoire D' Anatomie Ecole Nationale Veterinaire, 1968, p 301
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2. Constantinescu GM, Cosoroaba I: Arthro-myology. In Textbook of Comparative Anatomy, Tome 2, Timisoara, Romania, Institutul Agronomic, 1973 3. De Vos NR, Simoens PJ: Angiologia. In Schaller 0 (ed): illustrated Veterinary Anatomical Nomenclature. Stuttgart, Ferdinand Enke Verlag, 1992, pp 324-325 4. Evans HE, Christensen GC: Joints and ligaments. In Miller's Anatomy of the Dog, ed 2. Philadelphia, W6 Saunders, 1979, pp 225-268 5. Evans HE,Christensen GC: The heart and arteries. In Miller's Anatomy of the Dog, ed 2. Philadelphia, WB Saunders, 1979,pp 632-756 6. Evans HE, Christensen GC: The spinal nerves. In Miller's Anatomy of the Dog, ed 2. Philadelphia, WB Saunders, 1979, pp 972-1029 7. Hulse DA, Shires PK: The stifle joint. In Slatter DH (ed): Textbook of Small Animal Surgery. Philadelphia, WB Saunders, 1985, pp 2193-2233 8. Pastea E, Muresianu E, Constantinescu GM, et al: Arthro-inyology. In The Comparative and Topographic AnatOII1Y of Domestic Animals. Bucharest, Romania, Ed. Didactica si Pedagogica, 1978, pp 135-i37 · 9. Piermattei DL, Greeley RG: The hindlimb. In An Atlas of Surgical Approaches to the Bones of the Dog and Cat, ed 2. Plriladelphia, WB Saunders, 1979, pp 160-195
Address reprint requests to John T. Payne, DVM, MS Department of Veterinary Medicine and Surgery University of Missouri College of Veterinary Medicine 1600 Rollins Road C::olumbia, MO 65211
STIFLE SURGERY
STIFLE JOINT ANATOMY AND SURGICAL APPROACHES IN THE DOG John T. Payne, DVM, MS and Gheorghe M. Constantinescu, DVM, PhD, Drhc
Surgical diseases involving the stifle joint are among the most common causes of canine pelvic limb lameness. Developmental diseases such as patellar luxation and osteochondrosis of the femoral condyles, and traumatic and degenerative diseases such as rupture of the cranial cruciate ligament or primary degenerative joint disease are seen frequently in small animal practices. Thorough knowledge of stifle anatomy and surgical approaches is imperative for effective diagnosis and treatment of diseases of this joint. ANATOMY
The stifle is a complex diarthrodial joint that allows flexion and extension as well as axial and lateral movements. 1• 7• 8 The stifle joint consists of three components that freely interconnect: the femorotibial joint (between the femoral and tibial condyles), the femoropatellar joint (between the articular surface of the patella and femoral trochlea), and the proximal tibiofibular joint. 1• 2• 4• 7• 8 The femorotibial joint is partially occupied by the lateral and medial menisci. The menisci are C-shaped wedges of fibrocartilage that function to improve joint congruency and absorb compressive forces across the joint. The fibrous joint capsule of the stifle is visibly present only on the caudal aspect; no fibrous joint capsule is present cranial to the collateral ligaments of the femorotibial joint except for the femoropatellar ligaments. The synovial joint capsule is the largest joint capsule in the body and consists of three sacs that all intercommunicate.• Two of these sacs are between the lateral and From the Department of Veterinary Medicine and Surgery (JTP), and the Department of Veterinary Biomedical Sciences (GMC), University of Missouri College of Veterinary Medicine, Columbia, Missouri VETERINARY CLINICS OF NORTH AMERICA: SMALL ANIMAL PRACTICE VOLUME 23 • NUMBER 4 • JULY 1993
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medial femoral and tibial condyles. The third sac is the patellar pouch, which extends laterally from the parapatellar fibrocartilages to attach to the femur approximately 2 em from the trochlear ridges.• Proximally, the femoropatellar synovial capsule extends 1.5 em from the patella under the tendon of the quadriceps femoris muscle.• There is no distinct separation between the patellar and condylar sacs of the synovial capsule. Distal to the patella, the fibrous (patellar retinacula) and synovial portions of the joint capsule are separated by the infrapatellar fat pad that occupies the triangular space distal to the femur, proximal to the tibia, and caudal to the patellar ligament. 4 The femorotibial joint space is further divided into the femoromeniscal and tibiomeniscal portions by the menisci. The stifle is surrounded by four ligaments that provide excellent stability and allow for flexion, extension, limited varus and valgus angulation, limited craniocaudal movement, and axial rotation. Each ligament has specific functions and neutralizes specific forces acting on the stifle. The cranial cruciate ligament (CrCL) is located intra-articularly; it originates on the caudomedial part of the lateral femoral condyle and inserts on the cranial intercondyloid area of the tibial plateau.• The CrCL serves mainly to prevent abnormal cranial-caudal movement, but also provides rotational stability preventing excessive internal rotation of the stifle. A final function of the CrCL is to prevent hyperextension of the joint.' The canine CrCL is composed of two main portions: the craniomedial band and the caudolateral bond. The craniomedial band is taut throughout flexion and extension, whereas the caudolateral band is taut only during extension. 7 The caudal cruciate ligament (CaCL) is located intra-articularly originating on the lateral surface of the medial femoral condyle and inserting on the lateral edge of the popliteal notch of the tibia.• The CaCL is longer and heavier than the cranial cruciate ligament. Like the CrCL, it serves mainly to stabilize cranialcaudal movement. As the name implies, the two cruciate ligaments cross each other in the joint and provide rotational stability by wrapping around each other. The CaCL is also a secondary restraint against hyperextension of the stifle joint. The CaCL is also composed of two parts: a cranial and a small caudal band. The cranial band is taut in flexion and loose in extension, whereas the caudal band is taut in extension and loose in flexion.' The medial collateral ligament (MCL) originates on the medial femoral epicondyle and inserts on the medial border of the tibia just distal to the medial tibial condyle. This ligament fuses with both the joint capsule and the medial meniscus, and is responsible primarily for maintaining valgus stability. The MCL also serves as a secondary restraint against rotational instability. The lateral collateral ligament (LCL) originates from the lateral femoral epicondyle and inserts into the head of the fibula (Fig. 1). The lateral collateral ligament does not fuse with the lateral meniscus. The LCL courses distally and crosses laterally to the tendon of the popliteal muscle. The LCL is primarily responsible for maintaining varus stability, and serves as a secondary constraint against rotation instability. The LCL is also responsible for the "screw home" mechanism of the stifle joint. As the stifle joint flexes, the LCL becomes lax allowing internal rotation of the tibia relative to the femur. Following the swing phase of the step, the stifle will again begin to extend, the LCL will become taut, and the tibia will externally rotate or screw home. 7 The lateral and medial menisci are composed of fibrocartilage and occupy the space between the adjacent lateral and medial femoral and tibial condyles respectively. Positioned in the joint with the concave side facing axially, the menisci are thicker in their periphery than they are axially. The menisci are
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Figure 1. Anatomic dissection of the lateral aspect of the stifle demonstrating important structures and surgical landmarks. A = Vastus lateralis; B = lateral collateral femorotibial ligament; C = patella; D = long digital extensor tendon; E = lateral meniscus; F = biceps femoris (reflected); G = common peroneal nerve; H = lateral sesamoid of the gastrocnemius; I = popliteus tendon; J = gastrocnemius; K == flexor hallucis longus; L = fibularis (peroneus) longus; M = tibialis cranialis.
firmly held in place by six ligaments; namely, the craniolateral and craniornedial rneniscotibial ligaments, the caudolateral and caudornedial rneniscotibial ligaments, the interrneniscal ligament, and the rneniscofernoral ligament (lateral meniscus). Both menisci are firmly attached to the joint capsule. The medial meniscus is attached to the MCL. The menisci receive nutrients largely through the synovial fluid; however, there is blood supply to the peripheral10% to 15% supplied through the synovial membrane. 2 The menisci are important in the normal function of the stifle joint. They transmit approximately 65% of the weight across the stifle joint, and are important in maintaining craniocaudal and rotational stability. 7 The menisci are also important in increasing the efficiency of stifle joint lubrication, and in preventing synovial entrapment.' The two tendons located within the stifle joint are the tendons of the long digital extensor and of the popliteal muscles (Fig. 1). The tendon of the long digital_ extensor originates on the extensor fossa, between the lateral femoral condyle and the lateral ridge of the femoral trochlea, and is ensheathed by the synovial membrane for a distance of 3 to 4 ern. The tendon of the popliteal muscle originates on the popliteal fossa of the distal lateral condyle of the femur just caudal to the origin of the long digital extensor tendon, and passes caudally deep to the lateral collateralligarnent. The main blood supply to the stifle is the descending genicular artery that arises from the femoral artery distal to the origin of the saphenous artery. 5 This artery supplies the medial femorotibial and fernoropatellar joint capsule. The medial joint capsule also receives blood from the genicular articular branch of the saphenous artery. 3 The caudal genicular arteries arise from the popliteal artery and supply the joint capsule caudal to the collateral and cruciate ligaments. The blood supply to the lateral joint capsule is through the lateral proximal genicular artery that arises from the distal caudal femoral artery. The
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genicular articular rete supplies the distal lateral and medial aspect of the femorotibial and femoropatellar joint. 3 Innervation to the stifle is through the branches of the tibial and common peroneal nerves. The peroneal nerve receives sensory information from both the lateral joint capsule and the lateral collateral ligament. 6 LATERAL APPROACH
The lateral approach to the stifle joint is the most commonly used surgical approach to this joint in the dog and cat. It is used most frequently to reconstruct injuries to the cranial and caudal cruciate or to lateral collateral ligaments and to replace luxating patellae. It is also used to repair some intra-articular fractures and other less common injuries such as long digital extensor or popliteal tendon injuries. The lateral approach to the femur is performed with the patient positioned in lateral recumbency on the contralateral side of the approach, and the leg is hung for standard surgical preparation. After appropriate draping, a curvilinear incision is made on the lateral aspect of the femur extending from the distal one third to one half of the femur to a point 1 to 2 em distal to the tibial tuberosity (Fig. 2). This incision approximately follows the cranial border of the biceps femoris muscle proximally and a line 1 to 2 em lateral to the patella and patellar ligament distally. Small bleeding vessels in the dermis are controlled with electrocoagulation, and the fascia of the biceps femoris (the superficial layer of the fascia lata) and the lateral retinaculum are incised along a similar line (Fig. 3). If performing r~pairs using the lateral sesamoid bone of the gastrocnemius muscle (formerly fabella), the biceps fascia can be undermined and reflected caudally at this time. At the proximal end of the incision,
Figure 2. Lateral aspect of left stifle demonstrating location of skin incision (line). A = Patella; B = tibial tuberosity; Cr = cranial; Ca = caudal.
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Figure 3. Lateral aspect of left stifle after reflection of fascia lata. A = Fascia lata; B = lateral proximal genicular artery; C = lateral femoropatellar ligament; D = patella; E = stifle joint capsule; F = patellar ligament; G = vastus lateralis; H = biceps femoris (surrounded by superficial and deep fascia lata); I = gastrocnemius; J = lateral collateral ligament; K = aponeurosis of biceps femoris.
the vastus lateralis can be undermined from its caudal edge, and retracted cranially to expose the femoropatellar joint capsule (Fig. 4). It is preferable to reflect the vastus lateralis rather than to incise the muscle fibers. The joint CClpsule is exposed and incised along the lateral aspect of the trochlear margin. The joint capsule incision is then extended to its proximal extent using Mayo
Figure 4. Lateral aspect of left stifle demonstrating elevation and retraction of vastus lateralis to expose proximal joint capsule. A = Vastus lateralis; B = femoropatellar joint capsule; C = lateral femoropatellar ligament; D = biceps femoris (covered by superficial fascia lata); E = lateral proximal genicular artery; F = gastrocnemius; G lateral collateral ligament.
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Figure 5. Lateral aspect of left stifle demonstrating incision of the joint capsule. A = Vastus lateralis; B = aponeurosis of vastus lateralis; C = femoral trochlea; D = patella; E = tendon of long digital extensor; F = femoropatellar joint capsule; G = gastrocnemius; H = lateral femoropatellar ligament; I = lateral collateral ligament; J = popliteus tendon; K = aponeurosis of the biceps femoris.
dissection scissors. The femoropatellar joint capsule incision is extended distally, including the lateral femoropatellar ligament and the lateral patellar retinaculum, to expose the intra-articular femorotibial structures. One must be cautious not to inadvertently incise the long digital extensor tendon over the distal aspect of the femur. (Fig. 5). Once the joint is opened, the patella is luxated medially, and the infrapatellar fat pad is retracted distally using a sharp-pointed Senn retractor. The intra-articular structures are then examined. Additional exposure to examine the caudal horn of the medial meniscus in
Figure 6. Lateral aspect of left stifle demonstrating the intraarticular exposure. A = Hohmann retractor; B = medial meniscus; C = joint capsule (cut); D = lateral femoropatellar ligament (cut); E = long digital extensor tendon; F = cranial cruciate ligament; G = infrapatellar fat pad.
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Figure 7. Medial aspect of right stifle demonstrating location of the skin incision (line). A = Patella; B = tibial tuberosity; Cr = cranial; Ca = caudal.
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patients with CrCl ruptures can be obtained by placing a Hohmann retractor through the intercondylar space of the femur, and hooking the caudal aspect of the tibial plateau (Fig. 6). The Hohmann retractor used in this fashion causes cranial displacement of the tibia with respect to the femur, increasing the exposure of the caudal horns of the menisci. After the intra-articular sequence of the procedure is completed, the joint capsule is closed with an absorbable suture material in a simple interrupted pattern. The biceps femoris fascia is then brought cranially and closed using a simple interrupted or Mayo imbri-
Figure 8. Medial aspect of right stifle demonstrating the deeper dissection and joint capsule incision. A = Sartorius cranialis protected by lamina femoralis; B = attachment of vastus medialis; C = medial femoropatellar ligament; D = medial femoral condyle; E = patellar ligament; F = tibial tuberosity; G = vastus medialis; H = medial meniscus; I = medial collateral ligament; J = medial tibial condyle.
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Figure 9. Medial aspect of right stifle demonstrating exposure of intraarticular structures. A = Tendon of long digital extensor; B = lateral femoral condyle; C = patellar ligament; 0 = Senn retractor; E = cranial sartorius; F = caudal sartorius; G = vastus medialis; H = cranial cruciate ligament; I = caudal cruciate ligament; J = medial meniscus; K = infrapatellar fat pad.
eating suture pattern depending on the objectives of the closure. The subcutaneous · tissues are closed using a simple continuous pattern, and the skin is closed using a simple interrupted pattern. Occasionally access is needed to the caudolateral compartment of the stifle joint to repair ruptures of the popliteal tendon, to retrieve osteochondral
B
Figure 10. Cranial aspect of right stifle demonstrating bilateral arthrotomy incisions. A = Patella; B = lateral femoropatellar ligament (cut); C = patellar ligament; 0 = tibial tuberosity; E = cranial sartorius; F = vastus medialis; G = medial femoropatellar ligament (cut); H = medial ridge of femoral trochlea; I = caudal sartorius.
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fragments in stifle osteochondrosis, or to repair some fractures . Access is provided through a variation of the lateral approach to the stifle joint as described above. The skin incision is extended 3 to 5 em distally to the tibial tuberosity, and the biceps femoris is reflected caudally as in the lateral approach. One must note the position of the peroneal nerve and protect it from injury (see Fig. 1). To visualize the caudolateral compartment of the joint, the lateral head of the gastrocnemius muscle is elevated and retracted caudally. The popliteus muscle is partially elevated and retracted distally exposing the caudal joint capsule. The joint capsule is opened with a transverse incision exposing the caudal structures of the joint. Closure is performed as described above. MEDIAL APPROACH
The medial approach to the stifle joint is used less commonly than the lateral approach; generally, the two approaches are used to treat similar problems. The medial approach makes exposure of the lateral sesamoid bone of the gastrocnemius (fabella) more difficult during extra-articular stifle stabilization procedures; however, it is occasionally used in dogs when the owners are particularly apprehensive about a visible scar on the leg. The medial approach is preferred when repairing fractures involving the medial femoral condyle or ruptures of the medial collateral ligament of the femorotibial joint. The patient is positioned in dorsal recumbency with the leg hung. The patient's skin is prepared and draped in an appropriate manner. The skin incision for the medial approach to the stifle extends from the distal one third to one half of the femur to a point 1 to 2 em distal to the tibial tuberosity (Fig.
Figure 11. Craniolateral aspect of right stifle following osteotomy of tibial tuberosity and proximal reflection of quadriceps muscles. A = Tibial tuberosity (cut surface) B = patella (articular surface); C = parapatellar fibrocartilages; D = vastus intermedius; E = vastus lateralis; F = tendon of long digital extensor; G = tibialis cranialis (partially elevated); H = cranial sartorius; I = rectus femoris; J = vastus medialis; K = femoral trochlea; L = cranial cruciate ligament; M = caudal cruciate ligament; N = medial femoral condyle; 0 = infrapatellar fat pad.
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7). The subcutaneous tissue is incised along a similar line, and electrocoagulation is used to control hemorrhage. The deep fascia is then incised along the same line, and the cranial belly of the sartorius is elevated and retracted cranially. A parapatellar incision is continued through the medial femoropatellar ligament and the medial patellar retinaculum 1 to 2 em medial to the patella and patellar ligament and continued deep to the synovial membrane. This incision splits the fibers of the vastus medialis, which is closely associated with the medial retinaculum (Fig. 8). The cranial belly of the sartorius muscle may also be split in the direction of its fibers for a distance of 1 to 2 em at the proximal end of the incision, although this is unnecessary in most cases. 9 The articular cavity is then opened, and the patella is luxated laterally. Exposure of intra-articular structures is gained in a similar fashion as for the lateral approach (Fig. 9). Closure is accomplished in layers as in the lateral approach. TIBIAL TUBEROSITY OSTEOTOMY APPROACH
The tibial tuberosity osteotomy approach to the stifle is used to repair multiple intra-articular fractures of the femoral condyles or to perform stifle arthrodesis. 9 The patient is positioned in dorsal recumbency, and the leg is hung and prepared for aseptic surgery. After proper draping, a curvilinear incision is made over the cranial aspect of the stifle joint. The incision begins on the lateral aspect of the distal one third of the femur, and crosses the midline at the center of the patellar ligament. The incision continues distally on the craniomedial aspect of the tibia. 9 A medial and lateral arthrotomy are performed by incision of the fasciae, patellar retinacula, and synovial capsules bilaterally. The arthrotomies are extended distally to the tibial tuberosity so that the patellar ligament is isolated (Fig. 10). An osteotome and mallet are then used to remove the tibial tuberosity with its attached patellar ligament. Care must be taken to include a large enough piece of bone in the osteotomy for adequate stabilization during closure. Following osteotomy, the quadriceps muscles are reflected proximally until adequate exposure is achieved to perform the procedure (Fig. 11). After completion of the procedure, the tibial tuberosity is reattached using two Kirschner wires and a tension band wire. The lateral and medial patellar retinacula, synovial capsules, and fasciae are closed identically to the lateral and medial approach described previously, and the rest of the tissues are closed routinely in layers. SUMMARY
This article reviewed the pertinent anatomy and surgical approaches of the canine stifle joint. Anatomically correct approaches to this joint provide for relatively atraumatic entry into the joint, while providing adequate exposure to complete the intra-articular parts of the surgical procedure. Atraumatic surgical exposures provide for less postoperative pain and a better outcome to any surgical procedure. References 1. Barone R: Articulations de Ia ceinture et du membre pelviens. I!J Anatomie Comparee
des Mammiferes Domestiques. Lyon, Laboratoire D' Anatomie Ecole Nationale Veterinaire, 1968, p 301
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2. Constantinescu GM, Cosoroaba I: Arthro-myology. In Textbook of Comparative Anatomy, Tome 2, Timisoara, Romania, Institutul Agronomic, 1973 3. De Vos NR, Simoens PJ: Angiologia. In Schaller 0 (ed): illustrated Veterinary Anatomical Nomenclature. Stuttgart, Ferdinand Enke Verlag, 1992, pp 324-325 4. Evans HE, Christensen GC: Joints and ligaments. In Miller's Anatomy of the Dog, ed 2. Philadelphia, W6 Saunders, 1979, pp 225-268 5. Evans HE,Christensen GC: The heart and arteries. In Miller's Anatomy of the Dog, ed 2. Philadelphia, WB Saunders, 1979,pp 632-756 6. Evans HE, Christensen GC: The spinal nerves. In Miller's Anatomy of the Dog, ed 2. Philadelphia, WB Saunders, 1979, pp 972-1029 7. Hulse DA, Shires PK: The stifle joint. In Slatter DH (ed): Textbook of Small Animal Surgery. Philadelphia, WB Saunders, 1985, pp 2193-2233 8. Pastea E, Muresianu E, Constantinescu GM, et al: Arthro-inyology. In The Comparative and Topographic AnatOII1Y of Domestic Animals. Bucharest, Romania, Ed. Didactica si Pedagogica, 1978, pp 135-i37 · 9. Piermattei DL, Greeley RG: The hindlimb. In An Atlas of Surgical Approaches to the Bones of the Dog and Cat, ed 2. Plriladelphia, WB Saunders, 1979, pp 160-195
Address reprint requests to John T. Payne, DVM, MS Department of Veterinary Medicine and Surgery University of Missouri College of Veterinary Medicine 1600 Rollins Road C::olumbia, MO 65211