The effect of biplane medial opening wedge high tibial osteotomy on patellofemoral joint indices

Purpose: This study was designed to examine the effect of biplane medial opening wedge high tibial osteotomy (MOWHTO) on patellofemoral indices and posterior tibial slope.Materials and methods: Sixty-two knees (61 patients) underwent biplane MOWHTO for unicompartmental osteoarthritis of the knee. Patellar indices were measured by radiographic assessment postoperatively. The Merchant's views were used for patellar tilt and shift while standing lateral view radiographs were used for the patellar height analysis using the modified Blackburne-peel ratio (mBP). The patients were divided into two groups according to the change between the pre- and postoperative mechanical axis. Group A constituted the correction angle of equal more than 10 degrees, and group B of less than 10 degrees.Results: Group A demonstrated a significant change of mechanical axis and the tibial slope. Patellar indices including the patellar tilt, shift, and mBP did not show significant difference. Group B demonstrated the statistical significant difference in only the mechanical axis deviation. Patellar indices including the patellar tilt, shift, and mBP as well as the tibia slope did not show significant difference. When evaluated as a whole group, the mean shift in weight bearing line, patellar height (mBP), and tibial slope from preoperative to postoperative value was statistically significant. However, the patellar tilt and shift were not changed significantly.Conclusions: After biplane MOWHTO, patellar tilt and shift do not significantly change when measured on static mode supine X-ray. However, patella was lowered and tibia slope increased after MOWHTO.Level of evidence: II. (C) 2012 Elsevier B.V. All rights reserved