Dr Svetoslav Hristov
Dr Svetoslav Hristov
United Veterinary Clinic in Varna, Bulgaria
Multiple ligament knee injury is rare in dogs but more common in cats. Cranial cruciate ligament rupture in dogs is considered to be mainly degenerative in origin rather than primary traumatic which is opposite compared to humans. In the followed two cases there were no signs of preexisting degenerative changes in the stifle joint and they were considered as primary traumatic. In dogs statistically injury to the medial collateral ligament is more common than an injury to the lateral one. Only third degree and some second degree collateral ligament injury leads to stifle joint instability and requires surgery.
Anatomical notes
The main ligamentous support in the stifle joint is provided by four femorotibial ligaments – two cruciate ligaments and two collateral ligaments.
fig 1
fig 2
The lateral collateral ligament in the stifle joint has an insertion points on the lateral.
The cranial cruciate ligament mainly prevents from cranial tibial translation with respect to the femur , hyperextension and excessive internal rotation in the stifle joint
epicondyle of the femur and the proximal part of the fibula with some fibbers also attaching on the lateral tibial condyle (fig.1) . The medial collateral ligament has proximal insertion point on the medial epicondyle of the femur and broad distal insertion point on the caudomedial aspect of the proximal tibia (fig.2) . Some part of the ligament also blends with the joint capsule and has an attachment to the periphery of the medial meniscus. To summarise, the lateral collateral ligament is more loosed, superficially positioned and is taut only in the knee in extension. With the stifle joint in flexion the lateral collateral ligament relaxes which allows axial internal rotation inside the joint which is known as “screw home mechanism”. With the knee in extension, both collateral ligaments are taut preventing from excessive internal or external rotation.
The cranial cruciate ligament mainly prevents from cranial tibial translation with respect to the femur , hyperextension and excessive internal rotation in the stifle joint.
18 months male Drahthaar, weighting 32 kg with unknown trauma during hunting. Dog was presented a few hours after the trauma fully non weight bearing with the left hind limb. During physical examination an obvious cranial to caudal instability (positive drawer test) and lateral collateral instability (positive varus test) were detected. Medial to lateral and posterior to anterior radiographs were taken. There were no signs of preexisting degenerative joint disease. The dog was scheduled next day for a surgical stabilisation of the lateral collateral ligament, exploratory arthrotomy and tibial tuberosity advancement for the failed cranial cruciate ligament. After lateral parapatellar approach, the cranial cruciate ligament rupture was confirmed and the remnants were removed. No other intraarticular structures were visibly injured. By retracting the biceps muscle caudally, a mid substance tear of the lateral collateral ligament was discovered. Both parts of the ligament were sutured using a locking-loop suture pattern (Kesler type). For additional stability, the suture was protected by figure-eight 80# leader nylon positioned at the collate.
Tibial tuberosity advancement we performed as a second stage of the surgery after medial approach to the proximal tibia. Based on the preoperative measurements using the common tangent method a 12 mm cage was used for the tibial crest advancement
ral ligament attachments. The prosthetic ligament were fixed to the femoral condyle using a bone anchor and passed through a bone tunnel in the fibular head. Both ends of the new ligament were tightened using a dedicated spreadand crimped by with the joint in extension.
Dog #2
A female mixed breed dog, 4 years old, 12 kg was presented not able to walk after car accident. Fracture of the left humerus was suspected and confirmed by a radiography. Rupture of the urinary bladder was suspected during an abdominal ultrasound and confirmed by a contrast bladder radiographic study. On physical examination a cranial drawer and positive valgus test were noticed on the right knee. Rupture of the medial collateral ligament was confirmed also by stress anterior posterior radiography. On the medial lateral radiograph there were no signs of previous degenerative changes in the stifle joint.
Tie-in external skeletal fixator was used for stabilisation of the midshaft humerus fracture during the first surgery performed together with a laparotomy for suturing of the ruptured urinary bladder. A second surgery was performed for the stifle joint consisting of medial collateral ligament repair and tibial tuberosity transposition. After medial approach to the stifle joint and the proximal tibia, medial arthrotomy confirmed cranial cruciate ligament rupture. No other intraarticular structures were visibly injured. Retracting the caudal part of the sartorius muscle revealed a rupture of the medial collateral ligament close to its insertion on the medial tibial condyle. Because the tear was so severe, a primary reposition of the ligaments was not possible. 40# leader nylon in figure of eight suture was anchored at the medial collateral ligament attachments around two 2.7mm cortical screws and metal washers to prevent suture slippag Tibial tuberosity advancement was performed as a second stage during the surgery. Based on the preoperative measurements using the common tangent method a 7.5 mm cage was used for the tibial crest advancement.
Early postoperative period in both dogs passed without complications. About 10 days after surgery dog #2 was diagnosed also with grade II medial patella luxation in the operated knee and another surgery was performed next. Only this dog was followed for a few mon
ths after surgery when the external fixator from the humerus was removed. The dog recovered to a fully weight bearing with his right hind limb.
Comments
Failure of both the cranial cruciate and the collateral ligament support will result in pain, rapid osteoarthritis progression and impaired limb function.
The complexity of multiple ligament injury makes the palpation of the joint a bit confusing and could leads to mistakes in diagnosis of cranial vs caudal cruciate ligament rupture. Also because of the possibility of another damaged intra articular structures, an arthrotomy always has to be performed. Collateral ligament injury was first addressed in both cases followed by tibial tuberosity advancement for the failed cranial cruciate ligament. Tibial tuberosity advancement is one of the so called geometry modified procedures in cranial cruciate ligament rupture treatment and seems to be a better choice in cases when also a medial collateral ligament is ruptured. In such a cases positioning of implants (like TPLO plate) on the proximomedial aspect of the tibia will be challenging.
Acknowledgements
- Veterinary surgery: small animal, Tobias K, Johnston. S, 2012, Vol.1
- Atlas of orthopaedic surgical procedures of the dog and cat, Johnson, A., Dunning, D., 2005
- Stifle luxation in the dog and cat: The use of temporary intraoperative transarticular pinning to facilitate joint reconstruction, B.Keeley, M.Glyde,S. Guerin, R.Doyle, VCOT, 2007, Vol3
- Current techniques in small animal surgery, J. Bojrab, D.Waldron, J.Toombs, 2014, 5th edition
- An atlas of surgical approaches to the bones and joints of the dog and cat, D.Piermattei, K. Johnson, 4th edition, 2004
