Summary

This study explores the relationship between tibial anatomy and the wedge height required for different levels of posterior tibial slope (PTS) reducing osteotomies, highlighting that supratuberosity osteotomy requires a thinner wedge and produces a smaller cortical step-off than infratuberosity osteotomy, with patient-specific tibial morphology being crucial for surgical planning.

Abstract

Introduction

Posterior tibial slope (PTS) reducing osteotomies are gaining recognition as a response to the elevated risk of injury to the anterior cruciate ligament (ACL) graft following reconstruction. However, identifying the optimal surgical approach remains challenging, as both the ideal degree of correction and the precise level of osteotomy are not yet fully defined. This study aims to investigate the wedge height required for two different osteotomy levels aiming at the same amount of correction and examine its relationship with patient anatomical characteristics.

Methods

Revision ACL surgery search parameters identified 504 patients operated on by high-volume surgeons over the past 10 years, with 94 (19%) undergoing multiple revisions. Exclusion criteria included patients aged ≤14 and those lacking proper lateral knee radiographs (≥15 cm of proximal tibia visible, ≤5 mm condylar overlap). Medial PTS was measured using lateral knee radiographs, with the tibial axis identified by two circles below the tubercle. The postoperative PTS goal was set at 5˚. Osteotomy planning involved placing a 2-cm circle on the most posterior-proximal portion of the tibia on lateral knee radiographs to identify the hinge location, with the intended correction angle determining the osteotomy levels. Measurements included proximal tibial anterior-to-posterior width on lateral radiographs, projected osteotomy plane lengths, and the resulting anterior wedge height for both supra- and infratuberosity osteotomies, with correlations tested between lateral tibial width and wedge height. Anterior cortical step-off distance was measured as the difference in projected osteotomy lengths. All measurements were conducted using MATLAB_R2023b software.

Results

A total of 83 patients were identified after applying exclusion criteria, of whom fifty patients (60%) with a PTS≥12˚, indicated for PTS-reducing osteotomy per current guidelines, were included. The average tibial PTS was 14.6±2.5˚. The required wedge height for a one-degree PTS correction was 1±0.1 mm for supra- and 1.2±0.2 mm for infratuberosity osteotomy (p<.001). The average lateral proximal tibial width was 5.9±0.6 cm. A strong correlation was observed between proximal tibial anterior-to-posterior width and required wedge height per 1˚ correction for supratuberosity osteotomy (r=0.82, p<.001), while a moderate correlation was found for infratuberosity osteotomy (r=0.65, p<.001). The anterior step-off distance was 0.2±0.1 cm for supra- and 0.4±0.2 cm for infratuberosity osteotomy (p<.001).

Conclusion

Supratuberosity osteotomy requires a thinner wedge and results in a smaller anterior cortical step-off compared to infratuberosity osteotomy. The strong correlation between proximal tibial anterior-to-posterior width and required wedge height in supratuberosity osteotomies suggests that patient-specific tibial morphology should guide surgical planning. These findings can inform more precise surgical approaches, potentially improving outcomes for patients requiring PTS-reducing osteotomies.