Cranial Cruciate Injuries - What Are the Options?
James Tomlinson, DVM, Diplomate American College of Veterinary Surgeons
The first report of a cranial cruciate ligament rupture in the dog was in 1926 but it was not until the 1950's 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. 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 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. The remaining stumps of the ruptured CCL and any remaining intact CCL (in most cases) are removed. It is assumed that the remaining intact CCL is either 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. 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, are 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. 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. 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. Crimping of the suture with a stainless steel tube instead of tying a knot is a recent modification of the imbrication technique. Also, a sling suture pattern has been described.
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 and 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. 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.
Fibular Head Transposition
Fibular head transposition is an extra-articular repair technique that uses the lateral collateral ligament to stabilize the stifle joint. 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. Another benefit of fibular head transposition is the shorter recovery time compared to intra-articular techniques.
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.
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. 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. Significant elongation of the lateral collateral ligament occurred over the first 3 weeks after surgery. Stiffness of the collateral ligament increased over time, however. 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. 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 4-6 weeks after surgery and will gain strength after that. A support bandage is necessary for 6 weeks after surgery. Other intraarticular procedures utilize carbon fibers, allografts from patellar ligament, or other autogenous grafts; however, the basic procedure is the same.
Tibial Plateau Leveling Osteotomy
Traditionally, the stifle has been described utilizing a two dimensional model focusing on the biomechanics of the cranial and caudal cruciate ligaments. This model ignores the active forces of weight bearing on the joint and the musculotendonous contributions to stifle stability. In 1983, a model of the stifle was proposed which hypothesized that analysis of the canine stifle must include active forces generated by weight bearing and muscle/tendon action as well as passive forces produced by ligamentous structures.
In this model the role of the muscles of the caudal thigh which limit cranial translation of the tibia as well as other contributors to stifle function are accounted for such that the algebraic sum of the active and passive forces acting on the normal stifle is zero. Compression between the tibia and the femur produces a force defined as cranial tibial thrust which in the event such compression exceeds the restraining forces of the stifle abnormal cranial translation of the tibia will occur.
This is the case in the cranial cruciate deficient stifle. This unchecked cranial tibial thrust is proposed to be the underlying source of patient discomfort, meniscal damage, lameness and ultimately, degenerative joint disease. Accordingly, a surgical technique was developed to neutralize this force even in the event of a cranial cruciate ligament deficiency. This technique originally known as tibial closing wedge osteotomy and subsequently modified to tibial plateau leveling osteotomy (“TPLO”) ignores the traditional focus on surgically stabilizing cranial drawer sign and instead attempts to neutralize the forces which produce abnormal or uncontrolled cranial tibial thrust. This technique changes the angle of the tibial plateau which provides the stifle flexors with a mechanical advantage and permits stifle stabilization by active forces, thus returning the algebraic sum of the moments to neutral. In addition, the change in tibial plateau slope produces a flatter surface on which the tibial forces of weight bearing may be transferred to the femur.
The tibial plateau leveling osteotomy is a patented technique for treatment of cranial cruciate rupture with licenses available through Slocum Enterprises, Eugene, OR. The technique does not address the reconstruction of the passive constraints of cranial tibial thrust but rather seeks to enhance the active forces and provide a flatter surface for transfer of weight bearing forces from the tibia to the femur by leveling the tibial plateau.
The patient is anesthetized and prepared for surgery and positioned in dorsal recumbency. A medial approach to the proximal tibia and stifle is performed. The CrCL is debrided and the medial meniscus is examined and any tears are excised. A medial release of the meniscus is performed if no meniscal tears are present. A jig (Slocum Enterprises) is applied in the sagittal plane to the medial tibia the maintain alignment during and after the osteotomy. Additionally, this jig can be used to guide corrective manipulation of the osteotomy to address varus/valgus or rotational abnormalities of the tibia. A patented saw blade is used to create a radial osteotomy in the proximal tibia through the tibial plateau. The fragments are rotated based on radiographic measurement a predetermined distance to level the tibial plateau. A specific TPLO bone plate is used to stabilize the osteotomy.
Once radiographic healing of the osteotomy is demonstrated, usually 8 weeks, the patient’s activities are gradually increased to improve range of motion and increase muscle mass. The amount of activity should not create patient discomfort. Explosive activities such as running, jumping and rough play are avoided. If at any time during the rehabilitation process the patient becomes uncomfortable activity is reduced to the previously comfortable level. Generally the recommended regime involves progressively longer leash controlled walks during the first three weeks. Multiple walks to gain aggregate distance are superior to a single long outing. During the fourth through sixth week the walks are continued on a long lead allowing the dog the freedom to trot short distances. Beginning at week seven, controlled off lead activity is initiated. Small enclosures without distractions are ideal for this phase of the program. Following a final re-evaluation at approximately 10 weeks the patient is normally able to return to full function.
In 1993, the investigator who developed cranial tibial thrust model, cranial closing wedge technique and tibial plateau leveling osteotomy reported results of 394 cases treated by TPLO. A return to normal activity and function with excellent results was reported in 73% of the cases, good results in 21% and fair results in 3% of the cases. Two percent were reported as failures. The author reported many performance animals returned to competition with no evidence of disability related to their cruciate injury. Post-surgically, the tibial compression test was negative in 51% of patients, was slight in 36% and positive in 13%. The sit test was normal in 59 % of cases, slightly positive in 19 % and positive in 22 % of cases.
The most common complications reported were fixation associated. Four percent of case returned with meniscal problems. Rotary instability was seen post-operatively in 2.3 % of cases and internal rotation was identified in 2%. Surgery was repeated in approximately 8 % of cases.