Coronal tibiofemoral subluxation is correlated to correction angle in medial opening wedge high tibial osteotomy.

PURPOSE: This study aimed to analyse the change in coronal tibiofemoral (CTF) subluxation after high tibial osteotomy and to determine demographic variables associated with CTF subluxation. The change in CTF subluxation was hypothesised to be associated with the magnitude of correction of lower limb alignment and medial proximal tibial angle (MPTA).

METHODS: A total of 103 consecutive knees in 86 patients who underwent medial opening wedge high tibial osteotomy for symptomatic medial compartment knee osteoarthritis were retrospectively analysed. The normal %CTF subluxation value, which was defined as a subluxation of the proximal tibia relative to the distal femur on the lateral edge of the femorotibial joint, was determined from 60 normal knees. The association between CTF subluxation and the Knee Society Score (KSS) and radiographic parameters was examined.

RESULTS: The normal range for %CTF subluxation was defined as - 1.8 to 5.6%. Following osteotomy, Δ%CTF subluxation reduced from a mean of 4.5% (- 12.1 to - 4.6%) to 0.7% (- 6.8 to 8.2%), resulting in a decrease in lateral tibiofemoral subluxations concomitant with an increase in medial subluxations. The reduction in CTF subluxation correlated moderately with MPTA change (r = - 0.454, p < 0.001) and weakly with preoperative lower limb alignment as represented by hip-knee-ankle angle and %weight-bearing line. Multivariate regression analysis showed that ΔMPTA was a significant contributor of Δ%CTF subluxation.

CONCLUSION: Osteotomy reduced CTF subluxation, which was correlated with MPTA change. Postoperative MPTA should be considered during surgical planning, and a postoperative MPTA of approximately 93.5° may be an appropriate target to reduce CTF subluxation by obtaining normal CTF congruency.

LEVEL OF EVIDENCE: Level IV therapeutic, retrospective, cohort study.