Preoperative Medial Meniscus Extrusion Predicts Varus Correction Loss After 5 Years Despite Stable Bony Alignment After Medial Opening-Wedge High Tibial Osteotomy.

PURPOSE: To determine if medial meniscus extrusion (MME) impacts postoperative alignment and varus correction loss after medial opening-wedge high tibial osteotomy.

METHODS

We retrospectively reviewed patients who underwent medial opening-wedge high tibial osteotomy for medial compartment osteoarthritis with ≥5 years of follow-up. Patients were categorized using a 3-mm cutoff for preoperative MME on magnetic resonance imaging (≥3 mm defined pathological). Serial standing radiographs were obtained preoperatively and at 3 months, 1 year, and ≥5 years postoperatively, and the weight-bearing line (WBL) ratio, hip-knee-ankle angle, mechanical lateral distal femoral angle, medial proximal tibial angle, and joint line convergence angle were evaluated by an independent blinded observer. Alignment changes were analyzed using repeated-measures analysis of variance. Varus correction loss was defined as a final WBL ratio <50%, and predictors were identified using multivariate logistic regression including demographic and radiographic variables. Knee Injury and Osteoarthritis Outcome Score values (mean ± standard deviation) were evaluated preoperatively and at the final follow-up. Minimal clinically important difference achievement rates (defined as one-half of the standard deviation of the pre-to-post change) were compared between groups using Fisher's exact tests.

RESULTS

Fifty-five knees (44 patients; mean age, 59.3 years; mean follow-up, 6.9 [5.0-10.4] years) were included. Forty knees (72.7%) showed pathological MME. The pathological group had a significantly lower final WBL ratio (55.8% vs 65.7%, P = .008) and hip-knee-ankle (1.9° vs 3.9°, P = .025), whereas mechanical lateral distal femoral angle and medial proximal tibial angle did not differ. MME ≥3 mm (P = .004), lower 3-month WBL ratio (P < .001), and greater preoperative mechanical lateral distal femoral angle (P = .005) independently predicted varus correction loss. Knee Injury and Osteoarthritis Outcome Score significantly improved from preoperative to final follow-up in both groups (all P < .001). At final follow-up, there were no significant differences between the groups (MME ≥3 mm vs <3 mm): pain, 70.3 ± 24.3 vs 73.7 ± 25.4 (P = .667); symptoms, 70.9 ± 22.3 vs 80.7 ± 12.3 (P = .139); activities of daily living, 76.8 ± 22.8 vs 76.7 ± 20.4 (P = .992); sports, 45.3 ± 27.4 vs 53.8 ± 21.4 (P = .313); and quality of life, 53.2 ± 25.8 vs 55.8 ± 22.2 (P = .751). Minimal clinically important difference achievement rates were lower in the pathological group (57.5%-65.0% vs 80.0%-86.7%), although not statistically significant.

CONCLUSIONS

Pathological MME was associated with greater varus correction loss despite stable bony alignment and tended to show lower minimal clinically important difference achievement rates.

LEVEL OF EVIDENCE: Level III, retrospective comparative case series.