Reliability of Preoperative Planning Method That Considers Latent Medial Joint Laxity in Medial Open-Wedge Proximal Tibial Osteotomy.

BACKGROUND

Soft tissue laxity around the knee joint has been recognized as a crucial factor affecting correction error during medial open-wedge proximal tibial osteotomy (MOWPTO). Medial laxity in particular, which represents the changes in joint-line convergence angle (JLCA), affects soft tissue correction.

PURPOSE

The purpose of this study was to quantify medial laxity and develop a preoperative planning method that considers medial laxity.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

This study retrospectively reviewed 139 knees in 117 patients who underwent navigation-assisted MOWPTO from January 2014 to July 2019 for symptomatic medial compartment osteoarthritis with varus alignment >5°. We compared the results of 2 preoperative planning methods: conventional Miniaci (n = 47) and latent medial laxity reduction (LMLR) (n = 92). We evaluated the incidence of undercorrection, acceptable correction, and overcorrection. The radiologic parameters were analyzed using multiple linear regression with a stepwise selection model to establish an equation for the optimal preoperative planning method. The intraclass correlation coefficients (ICCs) of intraobserver, interobserver, and intermethod reliability were calculated.

RESULTS

The Miniaci method showed a higher incidence of overcorrection (55.3%) than the LMLR method (22.8%) at postoperative 6 months ( = .0006). Multiple linear regression with a stepwise selection model revealed a high correlation coefficient ( = 0.888) for the following equation: = 0.596 + 0.891 ×  - 0.255 × Δ . Upon simplification, the following equation showed the highest intermethod ICC value (0.991):  - ⅓Δ , while the Miniaci method showed a relatively low ICC value of 0.875.

CONCLUSION

There was a risk of overcorrection after MOWPTO using the conventional Miniaci method. An equation that considers medial laxity may help during preoperative planning for optimal correction during MOWPTO.