Retro-Tubercle Biplanar Opening Wedge High Tibial Osteotomy Is Favorable for the Patellofemoral Joint But Not for the Osteotomized Tubercle Itself Compared With Supra-Tubercle Osteotomy

Purpose: To identify whether retro-tubercle opening-wedge high tibial osteotomy (RT-OWHTO) produces more favorable radiographic outcomes on patellofemoral joint alignment and clinical outcomes than supra-tubercle opening-wedge high tibial osteotomy (ST-OWHTO). Methods: From January 2017 to July 2018, patients who underwent biplanar OWHTO were allocated to 1 of 2 groups (ST-OWHTO and RT-OWHTO). Plain radiographs and computed tomography were used to analyze patellofemoral alignment and other radiologic parameters representing osteotomy configurations. Clinical outcomes were assessed using American Knee Society Score and Western Ontario and McMaster Universities Osteoarthritis Index. Results: In total, 50 knees that underwent ST-OWHTO and 44 knees that underwent RT-OWHTO were enrolled. Patellar height was significantly decreased only after ST-OWHTO (Caton-Deschamps ratio: P = .007; Blackburne-Peel ratio: P = .012). Patellar tilt angle was decreased in both groups (P = .009 and .004, respectively). Postoperative posterior tibial slope (PTS) (P = .013), PTS (D) (P < .001), retro-tuberosity gap distance (P = .001), and retro-tuberosity tip distance (P = .001) were significantly larger in RT-OWHTO. Retro-tuberosity tip distance was significantly correlated with retro-tuberosity gap distance (P = .002), thickness of second plane osteotomy fragment (P = .027), and anterior osteotomy ratio (P = .031) in ST-OWHTO. In RT-OWHTO, it was significantly correlated with PTS (O) (P < .001), retro-tuberosity gap distance (P < .001), and sagittal angle of bi-planar osteotomy (P = .005). There were 2 cases of tibial tuberosity fracture, 9 cases of delayed union on second plane osteotomy and 5 cases of tuberosity protrusion in RT-OWHTO. Conclusions: Although the RT-OWHTO technique maintains patellofemoral joint alignment, no difference in clinical outcome was detected. The RT-OWHTO has increased risk of tuberosity fracture, delayed union, and prominent tibial tuberosity. The surgeon should consider these negative aspects of the technique and consider adjusting additional stabilization. Level of Evidence: Level III, retrospective cohort study.