Patellar height is not modified after isolated open-wedge high tibial osteotomy without change in posterior tibial slope.

INTRODUCTION Open-wedge high tibial osteotomy (OWHTO) corrects coronal deformity and can impact sagittal parameters such as posterior tibial slope and patellar height. The aim of the present study was to analyze change in patellar height after medial OWHTO with respect to tibial and femoral-referenced indices. MATERIAL AND METHOD This single-center retrospective study included 129 patients undergoing isolated posteromedial OWHTO, without change in tibial slope, using patient-specific cutting-guides. Patellar height was assessed on Caton-Deschamps (CD), Insall-Salvati (IS) and Schroter indices. Posterior tibial slope and coronal femoral and tibial angles were also measured. X-rays were taken preoperatively and at 12 months, and analyzed by 2 independent observers. RESULTS OWHTO modified the global lower-limb alignment (Δ=6.3±0.95, p<0.0001) and the proximal tibial deformity (Δ=7±0.88, p<0.0001). Posterior tibial slope and tibial (CD and IS) and femoral (Schroter) patellar height indices were unchanged. Intra- and inter-observer reproducibility was excellent (ICC 0.79-0.91). There were no correlations between HKA or MPTA angles and change in patellar height. CONCLUSION The present clinical series showed that patellar height was unchanged by isolated posteromedial OWHTO without change in tibial slope, using patient-specific cutting-guides, with whichever femoral or tibial reference index. The Schroter patellar femoral height index was highly reliable and is independent of proximal tibial changes in assessing patellar height, and can thus be recommended in the follow-up of OWHTO. LEVEL OF EVIDENCE III; retrospective cohort study.