Distal High Tibial Osteotomy Allows Improved Patellofemoral Joint Preservation but Results in Increased Posterior Tibial Slope Compared to Proximal High Tibial Osteotomy.

Abstract

To compare the postoperative trajectory of posterior tibial slope (p-TS) after distal (DTO) versus proximal (PTO) biplanar open-wedge high tibial osteotomy performed with an identical, early weightbearing protocol. All consecutive open-wedge high tibial osteotomies performed from May 2015 to December 2020 were reviewed. Eligible knees had complete lateral radiographs (preoperative, 1 week, 1 month, 3 months, 6 months, 12 months) and a ≥24-month follow-up. p-TS and Caton-Deschamps index were measured. International Cartilage Repair Society cartilage grade at routine plate removal was recorded. Thirty consecutive DTOs and 30 consecutive PTOs were retrospectively compared. The mean p-TS in the DTO group initially decreased after osteotomy but subsequently increased compared to the PTO group (P = .016). From 1 week to 12 months postoperatively, 9 of 30 knees (30%) that underwent DTO had a >2° increase in p-TS, compared with 2 of 30 knees (7%) that underwent PTO (P = .045). Of the 9 DTO knees with a >2° p-TS increase, 4 exhibited widening of the descending gap (the descending cut in the tibial tuberosity) and nonunion in the retrotubercle. The p-TS correction loss primarily occurred between 1 and 3 months postoperatively (P < .001). Arthroscopic assessment revealed patellofemoral cartilage deterioration in 8 of 28 knees (29%) in the PTO group, compared to only 1 of 28 knees (4%) in the DTO group (P = .024). A greater change in the Caton-Deschamps index was associated with patellofemoral cartilage deterioration at 12 months (P = .021). The p-TS changes during the postoperative course occurred more frequently in DTO compared to PTO. In DTO, p-TS increased for up to 12 months postoperatively, with the most substantial changes occurring between 1 and 3 months. While DTO has the advantage of preserving the patellofemoral joint, the increase in p-TS may require careful attention, as it could adversely impact bone union in the retrotubercle. Level III, retrospective comparative case series.