The effects of open wedge high tibial osteotomy for knee osteoarthritis on the patellofemoral joint. A systematic review

Background (including aims of the study): To investigate the impact medial opening wedge high tibial osteotomy (MOWHTO) has on the progression of patellofemoral (PF) OA, patella height, contact pressure within the PF joint and clinical outcomes. Methods: A systematic review was conducted in January 2022 according to PRISMA guidelines. The ICRS cartilage grade of the PF joint at the initial MOWHTO surgery and at second look surgery was compared and relative risk of progression of PF OA was calculated. Evaluation of patella height was assessed by Caton-Deschamps index, Blackburne-Peel index or Insall-Salvati index pre and post MOWHTO. Cadaveric studies assessing contact pressures in the PF after MOWHTO were included. Results: Forty-two studies comparing 2419 patients were included. The mean age was 53.1 years (16–84), 61.3% female. The risk of progression of PF OA was highest in the uniplanar and biplanar MOWHTO with proximal tubercle osteotomy groups (RR = 1.28–1.51) compared to biplanar MOHWTO with distal tubercle osteotomy (RR = 0.96–1.04). Patella height was not affected after biplanar MOWHTO with distal tubercle osteotomy (p < 0.001). Cadaveric studies demonstrate that PF contact pressures increase with more severe corrections (15°) but suggest biplanar MWOHTO and distal tubercle osteotomy induces lower contact pressures within the PF joint than other MOWHTO techniques. Significant over correction is associated with worse clinical outcomes and anterior knee pain. Conclusion: Biplanar MOWHTO and distal tubercle osteotomy has minimal effect on the contact pressures in the PF joint resulting in less severe progression of PF OA and has minimal impact on patella height.