Accuracy of Correction and Postoperative Complications Associated with a PEEK Opening Wedge High Tibial Osteotomy Implant

OBJECTIVES: To evaluate the accuracy of correction angle of an all-PEEK medial opening wedge high tibial osteotomy (HTO) system, as well as determine the effect of correction angle on postoperative complications. METHODS: Retrospective review was performed on patients who underwent an HTO by the senior author using an all-PEEK HTO system between 2014-2018 with a >6-month follow-up were included. Measurements were performed and classifications formulated by three senior residents and the senior author. Lateral hinge fractures (LHF) were classified according to Takeuchi classification system. Bivariate statistics were performed. RESULTS: Thirty HTOs in 27 patients were included (50% female; age, 37.8±10.8 years). Average follow-up was 16.2±10.1 months. Average post-operative radiographic valgus correction (Δ, 5.8±2.4°) was significantly less than that of the average implant correction angle (8.1±2.3°; p<0.001), indicating an overall average under-correction of 2.3±2.1°. There were 5 failures (16.7%; defined as approximately >5° loss of planned correction) that shared a common mechanism of medial cortical failure inferior to the implant. When selecting out the construct failures, the average correction accuracy of the 25 (83.3%) non-failures (1.5±1.2°) was significantly better than the 5 (16.7%) failures (6.3±1.8°; p=0.002). Four fractures (13.3%) were identified: 3 (10%) Takeuchi type I and 1 (3.3%) type III. All type I fractures were associated with >5° planned correction loss with medial cortex buckling. Overall, 9 knees (30%) experienced minor complications: neuropathy (n=1; 3.3%), deep vein thrombosis (n=2; 6.7%), and superficial infection (n=3; 10%). CONCLUSION: The use of an all-PEEK medial opening wedge HTO implant is a safe and effective system, with an acceptable average under-correction of 1.5° in patients not sustaining medial cortex failure. Loss of correction was associated with medial cortex failure and Takeuchi type I LHF. This is the first description of this failure mechanism (medial cortex buckling) that is specific to this implant and technique.