Maintaining Posterior Tibial Slope and Patellar Height During Medial Opening Wedge High Tibial Osteotomy: Letter to the Editor

Dear Editor:

We perused with profound interest the article penned by Mabrouk et al ² entitled “Maintaining Posterior Tibial Slope and Patellar Height During Medial Opening Wedge High Tibial Osteotomy.” There is still controversy as to whether medial opening wedge high tibial osteotomy (MOWHTO) affects posterior tibial slope (PTS) and patellofemoral height. After retrospectively analyzing 62 patients treated with MOWHTO, the authors concluded that MOWHTO did not result in significant changes in PTS or patellofemoral height. After reading the authors’ excellent and valuable article, we would like to offer some of our own observations. We have some suggestions and questions we would like to share with the authors.

First, the Caton-Deschamps, Insall-Salvati, and Schröter indices were used in this study to assess changes in patellar height; however, MOWHTO alters the anatomy of the proximal tibia, and measurements of the parameters for the Caton-Deschamps and Insall-Salvati indices involve reference points on the tibia, a situation that may affect the accuracy of the measurement for these indices. It is likely to be more accurate to assess patellar height using a measure such as the Miura-Kawamura index, which uses the anatomical landmarks of the femur as a reference point. ³

Second, the authors used specific lower-limb alignment parameters as test variables for PTS, such as hip-knee-ankle angle, medial proximal tibial angle, mechanical lateral distal femur angle, joint line convergence angle and joint line obliquity, and proximal posterior tibial angle. However, in a similar study by Ji et al, ¹ mechanical axis deviation was introduced as one of the measures of PTS change in addition to the above parameters and was statistically significant. Therefore, will the authors consider the inclusion of mechanical axis deviation as a parameter in a subsequent study to more comprehensively assess the change in PTS after MOWHTO?

Furthermore, both Shin et al ⁵ and Nejima et al ⁴ found that in MOWHTO, different preoperative radiographic positions could affect the measured values of the weightbearing line ratio and the angle of convergence of joint lines, where preoperative supine radiographs were more accurate than standing radiographs in predicting postoperative limb alignment in MOWHTO. Therefore, we would like to ask the authors about the radiographic measurement positions of the patients in their study. Was the effect of the difference in measurement positions on the test parameters taken into account?

In general, we would like to thank Mabrouk et al ² once again for their efforts on what is a significant study. It is our fervent hope that this addition will enhance the value of their study and help future researchers interested in this particular area.

Xinjie Wang, MSc Hui Ma, MSc Xiaowei Zhao, PhDJining, China