Supracondylar Osteotomy for Epiphysiolysis of the Medial Trochlear Ridge in Two Dogs
A. Schmaedecke; A.J. Casagrande; F.R. Silva; R.B. Moraes
Faculty of Veterinary Medicine, Federal University of Paraná, Curitiba, Paraná, Brazil
A beagle and a crossbreed dog were both presented with non-weight bearing on the hindlimb and a semi-flexed stifle. Clinical examination and radiographic investigation showed a grade 4 medial patellar luxation, characterized by epiphysiolysis of the medial trochlear ridge. No other significant skeletal abnormalities were detected. Varus supracondylar osteotomy of the femur is the surgical procedure indicated in young patients with symptomatic unicompartmental epiphysiolysis (Salter-Harris type VI fractures) associated with a valgus knee deformity. Osteotomy line were performed with the aim of a giggle saw, in the distal third of the femoral diaphysis, 2 cm above the metaphyseal area. The angle of rotation was calculated based on the anatomical and mechanical axis of the femur. The mechanical axis of the leg is defined by a line running through the centre of the hip joint to the centre of the ankle joint. This line should pass essentially through the centre of the knee joint or just to the medial side of the centre of the knee joint. The distance of this line tangentially from the centre of the knee joint is referred to as the mechanical axis deviation. In a valgus knee the mechanical axis passes lateral to the middle of the knee. The osteotomy fragments were stabilized with a 3.5mm reconstruction plate. In addition to that, a transposition of tibial crest was performed in both cases. The aim being to redirect femoral trochlear groove thereby prevent patellar reluxation. This technique was able to restore correct conformation of the femoral trochlea and preserve the integrity of the trochlear groove cartilage, thus potentially retarding the progression of degenerative joint disease. Both dogs recovered fully and postoperative radiographic examinations showed healing of the rotated trochlea with only mild signs of degenerative joint disease. These results and results reported in the literature demonstrate that distal femoral osteotomy for disabling genu valgum is an effective treatment for medial patellar luxation associated with femoral valgum deformity if the correction is complete and osteosynthesis effective, providing long lasting results when femoral deformation is involved and osteoarthritis limited. The reconstruction plate provides a convenient method by which to stabilize the ostectomy.