Assessment of mid-term clinical outcomes and radiographic analysis of simultaneous bilateral proximal fibular osteotomy for bilateral medial compartment Knee osteoarthritis: a single-arm retrospective cohort study with 7-year follow-up

This study aimed to evaluate the midterm clinical and radiographic outcomes of simultaneous bilateral proximal fibular osteotomy (SBPFO) for bilateral medial compartment knee osteoarthritis (MKOA), including changes in lower-limb alignment, the adjacent hip, patellofemoral, and ankle joints, and the lateral tibial plateau. This single-centre, single-arm retrospective cohort study identified 59 patients with bilateral MKOA who underwent SBPFO between 2018 and 2020. All 59 treated patients were included in the safety and survivorship analyses, whereas the final clinical and radiographic analyses included 55 patients who completed follow-up with both native knees. Among these 55 patients, the mean follow-up was 7.03 ± 0.57 years. Radiographic parameters were measured preoperatively and at final follow-up. Lower-limb alignment was assessed using the hip–knee–ankle angle (HKA), weight-bearing line ratio (WBLR), joint line convergence angle (JLCA), femorotibial angle (FTA), and settlement value. Adjacent-joint parameters included the hip abduction angle (HAA), acetabular index (AI), Sharp angle, knee–ankle joint angle (KAJA), talar tilt angle (TT), and tibial plafond inclination (TPI). Patellofemoral parameters included the posterior tibial slope (PTS), tibial tubercle prominence (TTP), Blackburne–Peel index (BPI), and Caton–Deschamps index (CDI); lateral tibial plateau changes were assessed using lateral plateau widening (LPW) and fibular height (FH). Clinical outcomes were assessed using the Visual Analogue Scale (VAS), Hospital for Special Surgery (HSS) knee score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and range of motion (ROM). Primary analyses were performed at the patient level using the mean of both knees ( n = 55), paired t tests, and Bonferroni correction; mixed-effects models were fitted as sensitivity analyses. Among the 55 patients included in the final clinical and radiographic analysis, the mean follow-up was 7.03 ± 0.57 years (range, 6.0–8.5 years). In the safety and survivorship cohort of 59 treated patients, primary wound healing was achieved in all patients, and one patient experienced transient toe numbness that resolved spontaneously within 3 months. One patient underwent unilateral conversion to TKA at 58 months after surgery and was considered a treatment failure. Patient-level Kaplan–Meier survivorship free from any conversion to knee arthroplasty was 98.3% (95% CI, 88.6%–99.8%) at 7 years. Lower-limb alignment improved: HKA increased from (175.97 ± 0.80)° to (177.20 ± 1.26)°, FTA decreased from (177.68 ± 1.61)° to (175.98 ± 2.02)°, JLCA decreased from (5.31 ± 0.81)° to (4.10 ± 1.07)°, and settlement value decreased from (5.27 ± 1.19) mm to (4.41 ± 1.35) mm (all P < 0.001), whereas WBLR did not change significantly after Bonferroni correction. Small radiographic changes in ankle-related parameters were observed, with TT decreasing from (5.55 ± 1.06)° to (4.72 ± 1.49)° and TPI decreasing from (6.17 ± 0.80)° to (5.54 ± 1.16)° (both P < 0.001). FH increased from (19.02 ± 1.37) mm to (23.72 ± 2.27) mm, and LPW decreased from (5.13 ± 0.44) mm to (3.93 ± 0.85) mm (both P < 0.001). No significant changes were observed in patellofemoral or hip-joint parameters. VAS improved from 6.36 ± 0.60 to 3.88 ± 0.92, WOMAC from 63.55 ± 4.40 to 37.89 ± 7.88, and HSS from 43.40 ± 7.41 to 65.06 ± 7.91 (all P < 0.001), with no significant change in ROM. In this single-arm cohort study with a mean follow-up of approximately 7 years, SBPFO was associated with symptom relief and functional improvement in carefully selected patients with bilateral MKOA who retained their native knees through final follow-up, although residual symptoms persisted. Radiographic analysis showed modest improvements in lower-limb alignment, small changes in ankle-related parameters, distal migration of the fibular head, and reduced LPW. Controlled studies are needed to confirm these findings.