In patients younger than 60 years, high tibial osteotomy (HTO) is a satisfactory therapy for varus gonarthrosis. HTO may afford young patients substantial relief of pain and does not restrict activity. However, the indication for HTO is currently under discussion due to the fact that closing (CWO) and opening (OWO) wedge osteotomy produce opposite changes in patellar height and inclination of the proximal tibial articular surface. Consequently this can possibly affect outcome of knee surgery. The aim of this study was to compare the variations both in patellar height and inclination of the proximal tibial plateau produced by the two more common proximal tibial osteotomy techniques. We analysed 60 patients with unicompartmental osteoarthitis and angular deformity of the knee divided into two groups: group 1 (30 patients) treated with CWO using a plate VCO and group 2 (30 patients) treated with OWO using Puddus’s plate. Patients were comparable in age, gender and knee deformity. Patellar height was evaluated by Caton’s method. The inclination of the proximal tibial plateau was measured as the angle between the articular surface and the lateral longitudinal axis of the tibia. Patellar height before CWO surgery was 0.98 ± 0.128, after surgery 1.01± 0.195. Patellar height before OWO surgery was 0.99 ± 0.134, after surgery 0.91± 0.125. Posterior tibial inclination before CWO surgery of was 7.5° ± 4°, after surgery 3.5° ± 5°. Posterior tibial inclination before OWO surgery was 7.5° ± 4°, after surgery 8° ± 5°. Unexpectedly, CWO did not modify, wheras OWO significantly decreased the height of the patella. The inclination of the proximal tibial plateau increased after OWO, but decreased after CWO. Lack of variation in patellar height after CWO could be explained by fibrosis and patellar ligament contracture, whereas in OWO, the decreased distance between patella and tibio-femoral joint line was derived from joint line elevation. Following a tibial osteotomy both the height of the patella after OWO or the reduced inclination of the proximal tibial plateau may have deleterious consequences for patellofemoral biomechanics and complicate subsequent total knee arthroplasty.
