Every cat knee arthrodesis is an orthopedic challenge. Cats have relatively long bones, crista tibia is narrow and even sharp most cranially, and they are very active animals with common post-op serious vertical efforts, for example jumping to and from furnitures and even refrigerators. The arthrodesis of their knees requires maximal stability of the fixation, freedom for intraoperatively estimation for usage of different screws on one and the same plate – from 2.0 mm to 2.7 mm thick, a serious attention to the fixation of the plate to crista tibiae and the underlying tibia. And, of course, maximal level of aseptic and antiseptic procedures and algorithms: by every orthopedic surgery the possibility for post-op infection is proportional to the implants surface in sq mm and during arthrodesis we use wide and thick plate with serious surface and many screws sometimes even wires with serious surface too.
During the last 16 years we passed through different variations of the arthrodesis technique with different implants systems – at the beginning non-locking, later locking. Fortunately finally we found not only the best for us technique variant but also the most reliable for us implanst system and achieved constantly excellent results in 9 cats.
All 9 surgeries were very smilar with approximately equal percentage of covering of femurs as well of tibias. By all of them we used one and the same system – Mikromed locking 2.4 with one and the same plate – symmetrical limited contact straigth locking plate with “bridging” area in the middle (without hole for screw). In all 9 cases this bridging segment was positioned in the area of the femuro-tibial connection. In all cases we used on one and the same plate different screws – locking Mikromed 2.4 mm (in the tibia) and 2.7 mm (in the femur and in the bigger cats in the tibia as well) and non-locking (2.0 mm, 2.4 mm and 2.7 mm). In all cases before the tibial plating we took away with Rounger curette the most cranial 1-3 mm wide part of crista tibiae which procedure should be made very carefully and doesn’t compromise the fixation because in cats crista tibiae is build by bone compacta more caudally in comparison to dogs (that why we recommend in case of transposition of crista tibiae to cut the osteotomy into the tibia as caudal as possible – of course not damaging the menisci – in order not to compromise the healing process; but this is another story for another technique).
The patients and their individual stories before the surgery were not similar, however the results were equal: constatnly 100 % excellent. Here we present two different cases: Cat Gosho, under 4 kg, allowing manipulations without problems, with trauma not more than 2 weeks before the surgery, without muscle atrophy; and Cat Aksel, over 6 kg, very difficult to be manipulated and with “specific” temperament, which trauma happened before approx 2 years and as result the patients leg had severe muscle atrophy and weakness of the ahilea tendon.
The only difference in the approaches to both patients was the fact that because of the weight and the temperament of Aksel we left both situational wires in comparison to the surgery of Gosho where we removed them after finishing the plating process.
As in all orthopedic surgeries in cats we do not loose intra-operatively time for plate bending – more time means bigger risk of anesthetic problems and infection. We have a big collection of cat bones (cat bones are very similar, the dog bones aren’t) from cats of different weight including “arthrodesed” femur+tibia combinations. We use these models before autoclaving the implants for perfect contouring the plate to the bones and bnes combinations and for preparation of the perfect screws combination.
We recommend the dynamic compressive screw to be not in the femur but in the tibia this means to fix the plate with locking screws first to the femur and after that to start fixing it to the tibia. We recommend two non-locking 2.0 mm cross-screws in both holes nearest to the plate middle. We strongly recommend to take off the most cranial 1-3 mm slice of the tibial (crista tibiae) silhouette with Rounger for better contact between plate and bone and respectively best stability. And, of course, do not forget to take off all the cartilages, menisci, cruciate ligaments and the patella and to compress tibia to femur as strong as possible.
The nine cases prove that there is not any need of longer plates covering bigger percent of the femural and tibial length. We monitored all the 9 cats for period between 2y4m to 1 m after the procedure and there aren’t any signs of problems including fissures or fractures of bones at the plate edges.
Video of Gosho 10 m post-op:
As usually the goal is the patient to start using the leg very soon. In the first 2-5 weeks some hyperextensy of the hook and abduction of the leg are normal.
Cat Aksel 96h post-op:
Conclusion: the presented at the X-ray pictures below variant of cat knee arthrodesis with lockig system Mikromed 2.4 guarantees constantly excellent result.
Gosho X-Ray pictures:
Aksel X-Ray pictures: