Anatomy
The stifle joint is a complicated, diarthroidial joint consisting of a femoropatellar and a femorotibial articulation. The stifle joint has six degrees of freedom (flexion, extension, varus and valgus angulation, internal and external rotation) that are constrained by various ligaments and tendons as well as the joint capsule and muscles. The dog's stifle has a normal range of motion of 110 degrees, ranging from 150 degrees in full extension to 40 degrees in full flexion. The stifle is extended by the quadriceps muscle group; the patella is a sesamoid bone within the quadriceps tendon that serves to improve the mechanical advantage of the muscle-tendon unit. The quadriceps group consists of the rectus fomoris, vastus medialis, vastus intermedius, and vastus lateralis. These muscles originate from the proximal femur and pelvis, and insert via the patellar ligament on the tibial tuberosity. The long digital extensor muscle also serves as a minor stifle extensor. The stifle is flexed by the semimembranosus/semitendinosus muscles. The popliteal muscle is a stifle rotator.
The cranial and caudal cruciate ligaments are primary stabilizers of the stifle joint. The cranial cruciate originates from the medial side of the lateral femoral condyle and inserts on the cranial medial tibial plateau. It is composed of two parts: the craniomedial and caudolateral bands. The craniomedial band is tight in flexion and extension, whereas, the larger caudolateral band is tight in extension and loose in flexion. The caudal cruciate originates from the lateral side of the medial femoral condyle and inserts in the popliteal fossa of the tibia. It is composed of a cranial and caudal band. The cranial band is tight in flexion and the caudal band is tight in extension. The cruciate ligaments serve as primary constraint of the stifle and limit cranial-caudal motion, internal rotation, and hyperextension.
The medial and lateral collateral ligaments are also important stabilizers of the stifle. The medial collateral ligament originates from the distal medial femoral condyle and inserts on the proximal medial tibia. The lateral collateral ligament originates from the distal lateral femoral condyle and inserts on the head of the fibula. These ligaments serve to limit varus (lateral collateral) and valgus (medial collateral) instability. The lateral collateral ligament becomes loose when the stifle is flexed and allows the tibia to rotate internally. As the stifle is extended, the lateral collateral ligament tightens and externally rotates the tibia to its normal weight bearing position. This is known as the “screw home mechanism.”
The medial and lateral menisci are “C” shaped wedges of fibrocartilage that serve as primary stabilizers of the stifle. The lateral meniscus is secured to the tibia by the cranio- and caudolateral meniscotibial ligaments, to the femur with the meniscofemoral ligament, and to the medial meniscus by the intermeniscal ligament. The medial meniscus is secured to the tibia by the cranio- and caudomedial meniscotibial ligaments and to the lateral meniscus by the intermeniscal ligament. The medial meniscus is also attached to the medial collateral ligament and to the caudomedial joint capsule.
Cranial Cruciate Rupture
The first report of a cranial cruciate ligament rupture in the dog was in 1926, but it was not until the 1950s that the first report of surgical correction was described. Since then, numerous surgical techniques for repair of the cranial cruciate-deficient knee have been reported in the literature.(1) Selection of a technique for repair of the cranial cruciate- deficient knee should be based upon numerous criteria including size, age, and function of the dog, chronicity of the injury and surgeon preference. Repair techniques are classified as extra-articular and intra-articular. Extra-articular repairs are those that stabilize the joint from outside of the joint capsule and include fascia lata imbrication, lateral retinacular imbrication (DeAngelis suture), and fibular head transposition. Intra-articular techniques use some sort of graft material to anatomically replace the cranial cruciate ligament
All surgical procedures for CCL instability begin with a thorough exploration of the stifle joint through a lateral parapatellar approach. All intra-articular structures are examined. The most common injury coexisting with a CCL rupture is a tear in the caudal horn of the medial meniscus (discussed later). The caudal cruciate ligament (CaCL) and collateral ligaments are also examined, as well as the tendons of the long digital extensor and popliteus. The remaining stumps of the ruptured CCL and any remaining intact CCL are removed. It is assumed that the remaining intact CCL either is damaged or will become completely ruptured if left. If the caudal horn of the medial meniscus is damaged, only the damaged portion is removed.
Extra-articular Repair Techniques
Fascia Lata Imbrication
Imbrication refers to the overlapping of two layers like tiles or shingles. The affect of imbrication of the fascia lata is to take any slack out of the fascia lata thus tightening the tissue. The tightening of the fascia lata thus stabilizes the joint by minimizing the cranial translation and internal rotation of the tibia. This technique, as the sole means of stabilization, was first reported in 1966 and later modified in 1969 by adding a second layer of Lembert sutures.(2,3) Fascia lata imbrication is most appropriately used as an adjunct to other methods of stifle stabilization and should not be used as the sole method of stabilization.
The Lembert and Mayo-Mattress suture patterns are the main type of suture patterns used to imbricate the fascia lata. An absorbable suture, such as Vicryl or PDS, is the preferred suture material type. Suture placement starts distal and proceeds in a proximal direction. Tension is judged, before placing the first suture, by how much the edges of the fascia lata will overlap. Care must be taken to not place so much tension on the tissue that a lateral patellar luxation is produced.
Lateral Retinacular Imbrication
Lateral retinacular imbrication for stabilization of the cranial cruciate deficient stifle was first reported in 1970 by DeAngelis and Lau. This technique is commonly referred to as the DeAngelis technique.(4) This technique originally consisted of placing a heavy nonabsorbable suture material around the lateral fabella to the distal one-third of the patella ligament. The suture material corresponds to the orientation of the normal cranial cruciate ligament as it travels through the joint except that the suture is outside of the joint capsule. Numerous modifications of this technique have been made including placing the suture through a hole drilled in the tibial tuberosity and adding a similar directed suture from the medial side of the joint.(5) Placement of two sutures from the lateral collateral ligament to the patella and one suture from the fabella to the patella ligament has also been described for stifle stabilization.(5)
Lateral retinacular imbrication has been used for stabilization of the stifle of all sizes of dogs. Typically, lateral retinacular imbrication works best for dogs 40–45 pounds or less in weight. Variable results are encountered as the size of the dog increases. Fascia lata imbrication generally is performed in addition to this technique to further stabilize the joint.
Heavy nonabsorbable suture material (nylon, braided polyester) is used for lateral retinacular imbrication. Stainless steel wire has also been used.(7) Typically, the suture is tightened with the stifle extended and the tibia externally rotated. Multiple knots are needed to secure the suture. Passing the suture through a hole in the tibial tuberosity probably allows better anchoring for the suture. Over time, all of these sutures break or loosen. Hopefully the sutures maintain joint stability until periarticular fibrosis stabilizes the joint. The most common postoperative complications with this technique are swelling and drainage from the suture. These two complications are reported to occur in 18% and 21% of cases.(3,9)
Fibular Head Transposition
Fibular head transposition is an extra-articular repair technique that uses the lateral collateral ligament to stabilize the stifle joint.(10) The lateral collateral ligament runs from the lateral epicondyle of the femur to the fibular head. After cranial transposition of the fibular head, the orientation of the lateral collateral ligament is redirected to approximate that of the cranial cruciate ligament. Cranial drawer motion and excessive internal rotation of the joint are prevented by this orientation of the lateral collateral ligament. This procedure can be used for any size of dog with either acute or chronic ruptures of the cranial cruciate ligament. Fibular head transposition is particularly suited for dogs with osteoarthritis of the stifle where an intra-articular technique is not desirable. Chronicity of cranial cruciate rupture prior to repair has been reported not to affect clinical results after repair with this technique.(10) Another benefit of fibular head transposition is the shorter recovery time compared to intra-articular techniques.(10)
The surgical procedure involves cutting the ligamentous attachments of the fibular head to the tibia so that the fibular head can be transposed cranially. The fibular head is moved forward to a point that the drawer sign has been eliminated. The fibular head is then secured to the tibia with K-wires and a tension band wire.(10)
Postoperatively, the leg is placed in a soft-padded bandage for 10–14 days. The dog's activity is limited for the first month and then slowly increased over the second month. Long-term clinical evaluation of this procedure indicated that 90% of the dogs had an excellent or good result.(11) Research evaluation of fibular head transposition showed that the technique did not control cranial drawer motion or rotational instability, was not successful in restoring limb function, and did not prevent joint degeneration.(12) Significant elongation of the lateral collateral ligament occurred over the first 3 weeks after surgery.(13) Stiffness of the collateral ligament increased over time, however.(13) Clearly there is a difference in the clinical and research evaluation as to how effective fibular head transposition is. The most common complications associated with fibular head transposition was iatrogenic fracture of the fibular head intraoperatively (12.5%) and seroma formation (10.7%) over the fibular head postoperatively. Other complications that have been reported include wire breakage and tearing of the lateral collateral ligament.(10) Pin loosening and migration, damage to the peroneal nerve, and laceration of the caudal geniculate artery are other possible complications.
Intra-articular Repair Techniques
There are numerous procedures in which a fascial, patellar ligament, or non-biologic graft is pulled through the stifle joint in such a way that the natural function of the CCL is closely mimicked. The majority of these procedures are performed through a lateral parapatellar approach and the joint is explored and debrided as in the extraarticular procedures. The “under-and-over” procedure is generally the representative of these procedures and is the most commonly used. This procedure utilizes an autogenous graft including the lateral 1/3 of the patellar ligament as well as the fascia lata from the lateral thigh. This graft is prepared by incising its lateral, medial, and proximal attachments, leaving it attached distally. The graft is then pulled under the intermeniscal ligament and through the joint “over the top” of the lateral femoral condyle where it is anchored by sutures or a bone screw and spiked washer. The joint is closed routinely. This graft will weaken during the first two weeks after surgery and will gain strength thereafter. It reaches preoperative strength six weeks after surgery. A support bandage is necessary for six weeks after surgery. Other intraarticular procedures utilize carbon fibers, allografts from patellar ligament, or other autogenous grafts; however, the basic procedure is the same.
References
1. Knecht CD. Evolution of surgical techniques for cruciate ligament rupture in animals. J Am Anim Hosp Assoc 1976;12:717-726.
2. Childers HE. New Method for cruciate ligament repair II. Repair by suture technique. M.V.P. 1966;47:59-60.
3. Pearson PT, McCurrin DM, Carter JD, Hoskins JD. Lembert suture technique to surgically correct ruptured cruciate ligaments. J Am Anim Hosp Assoc 1971;7:1-13.
4. DeAngelis M, Lau RE. A lateral retinacular imbrication technique for the surgical correction of anterior cruciate ligament rupture in the dog. J Am Anim Hosp Assoc 1970;157:79-84.
5. Flo GL. Modification of the lateral retinacular imbrication technique for stabilizing cruciate ligament injuries. J Am Anim Hosp Assoc 1975; 11:570-576.
6. Gambaradella PC, Wallace LJ, Cassidy F. Lateral suture technique for management of anterior cruciate ligament rupture in dogs: a retrospective study. J Am Anim Hosp Assoc 1981;17:33-38.
7. Hulse DA. The stifle joint, in Olmstead ML (ed):Small Animal Orthopedics. St. Louis, Mo, Mosby, 1995, pp 395-416.
8. Dulish ML. Suture reaction following extra-articular stifle stabilization in the dog—part I. a retrospective study of 66 stifles. J Am Anim Hosp Assoc 1981;17:572-574.
9. Dulish ML. Suture reaction following extra-capsular stifle stabilization in the dog—part I. a retrospective study of 161 stifles. J Am Anim Hosp Assoc 1981;17:569-571.
10. 10. Smith GK, Torg JE. Fibular head transposition for repair of cruciate-deficient stifle in the dog. J Am Anim Hosp Assoc 1985;187(4):375-383.
11. Mullen HS, Matthiesen DT. Complications of transposition of the fibular head for stabilization of the cranial cruciate-deficient stifle in the dog: 80 cases (1982-1986). J Am Anim Hosp Assoc 1989; 195(9):1267-1271.
12. Dupuis J, Harari J, Papageorges M, Gallina AM, Ratzlaff M. Evaluation of fibular head transposition for repair of experimental cranial cruciate ligament injury in dogs. Vet Surg 1994;23:1-12.
13. Dupuis J, Harari J, Blackketter DM, Gallina AM. Evaluation of the lateral collateral ligament after fibular head transposition in dogs. Vet Surg 1994;23:456-465.