Objectives To assess the impact of a biplanar ascending opening-wedge high tibial osteotomy (OWHTO) on the alignment of the knee extensor mechanism and patellar height using preoperative and postoperative MRI.
Methods Medical records of all patients submitted to ascending biplanar OWHTO between July 2008 and March 2017 were retrospectively assessed. Five parameters of the patellofemoral joint—tibial tubercle–trochlear groove distance (TT-TG), patellofemoral (PF) axial engagement index, lateral patellar tilt, Blackburne-Peel index (BPI) and Caton-Deschamps index (CDI)—were measured by two blinded independent observers on both preoperative and postoperative MRIs. Interobserver reliability was assessed with the intraclass correlation coefficient (ICC). Paired t-test was performed to compare preoperative and postoperative measurements. The association of the amount of HTO opening and the assessed PF joint parameters was also investigated with Pearson correlation coefficient.
Results 26 patients who underwent ascending biplanar OWHTO were enrolled in this imaging analysis (63.4%) with a mean follow-up of 16.3 months (SD, 16.9). ICC for all measurements ranged between 73.3% and 89.3%. Postoperatively, TT-TG distance significantly increased by 2.0 mm±2.3 mm (p<0.001). Patellar height significantly decreased when evaluated by the BPI (p<0.001) and CDI (p=0.001). The amount of osteotomy opening significantly correlates with the postoperative BPI (p=0.023) and CDI (p=0.013).
Conclusion This study comprehensively reports significant increase on TT-TG distance after an ascending biplanar OWHTO using MRI. Small but significant decreases in patellar height were also observed and are correlated to the amount of axis correction.
Level of evidence Level IV, retrospective case study.
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