Evaluation of Posteriorization Following Pure Distalization Tibial Tubercle Osteotomy

Abstract

Background:

There are theoretical concerns that tibial tubercle osteotomy with pure distalization (TTO-d) may posteriorize the tibial tubercle (and thus increase patellofemoral contact pressure); however, whether TTO-d actually results in posteriorization of the tibial tubercle has never been empirically investigated.

Purpose:

To assess the relative amount of anteriorization or posteriorization of the tibial tubercle that occurs after TTO-d.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Consecutive patients, with preoperative and postoperative lateral knee radiographs, who underwent TTO-d between 2015 and 2023 by 2 surgeons were identified. Measurements of posteriorization were performed by 2 physician raters using a magnetic resonance imaging–validated technique. Comparisons were made with the Student t test, and agreement was assessed with the intraclass correlation coefficient.

Results:

A total of 38 patients (86.8% women) were included, with a mean age of 29.3 ± 9.7 years. The mean Caton-Deschamps index significantly decreased from 1.32 ± 0.13 preoperatively to 1.02 ± 0.10 postoperatively (P < .001). There was no significant change in sagittal alignment (ie, anteriorization/posteriorization) from preoperatively (21.6 mm) to postoperatively (22.4 mm) (P = .14). The mean amount of anteriorization/posteriorization was 0.82 ± 1.40 mm anterior (range, 1 mm posterior to 4 mm anterior). There were 31 patients (81.6%) who experienced no change or slight anteriorization; no patient experienced >1 mm of posteriorization. Interrater reliability was excellent (intraclass correlation coefficient = 0.93).

Conclusion:

Contemporary TTO-d resulted in the successful correction of patella alta without appreciable posteriorization of the tibial tubercle. These results support the positive clinical outcomes seen with TTO-d, including for chondral lesions, and may reduce concerns about inadvertent posteriorization when performing this procedure. While overdistalization with the formation of patella baja can increase patellofemoral contact pressure beyond native ranges, the current results suggest that restoration of a normal patellar height is unlikely to do so.