# The Magnitude of Varus Correction and Its Influence on Postoperative Patellar Height and Posterior Tibial Slope in Medial Open-Wedge High Tibial Osteotomy

## TL;DR

This study examines how the degree of correction in a knee surgery affects patellar height and tibial slope, finding that larger corrections lead to more significant changes.

## Contribution

The study identifies the modified Miura–Kawamura index as more sensitive for detecting patellar height changes after surgery.

## Key findings

- Larger correction angles in surgery are associated with greater decreases in patellar height and increases in posterior tibial slope.
- The modified Miura–Kawamura index detected patella infera more frequently than other methods.
- Significant associations between correction magnitude and outcomes were observed in patients with corrections of 10° or more.

## Abstract

Objectives: Medial open-wedge high tibial osteotomy (MOWHTO) is a surgical procedure used to treat medial compartment osteoarthritis of the knee with varus deformity. The aim of this study was to examine whether a larger correction angle in medial open wedge high tibial osteotomy (MOWHTO) leads to greater changes in postoperative patellar height (PH) and posterior tibial slope (PTS). Methods: Data from 83 patients who underwent MOWHTO were retrospectively analyzed. Lower limb alignment was evaluated using the hip–knee–ankle angle (HKAA). The PH was assessed using the Insall–Salvati index (ISI), the Blackburne–Peel index (BPI), the Caton–Deschamps index (CDI), the modified Miura–Kawamura index (MKI), and the plateau–patella angle (PPA). The PTS was determined using the Moore–Harvey method. Results: The median correction of HKAA was 8°. A decrease in PH was observed in the majority of cases across all methods, with the highest frequency of postoperative patella infera detected using the MKI. PTS most frequently increased, with a median increase of 3°. A significant association between the magnitude of HKAA correction and patellar height in the overall cohort was observed only for the MKI, whereas in patients with an HKAA correction ≥ 10°, significant associations were found for both the MKI and CDI. No significant association was found between the magnitude of HKAA correction and changes in posterior tibial slope in the overall cohort, while a significant negative correlation was observed in patients with an HKAA correction ≥ 10°. Conclusions: Assessment using the MKI demonstrated greater sensitivity in detecting postoperative PH decrease, particularly in identifying patella infera. The magnitude of HKAA correction was significantly associated with greater changes in PTS and PH in patients with a coronal plane correction of ≥10°.