Distal femoral osteotomy versus lateral unicompartmental arthroplasty for isolated lateral tibiofemoral osteoarthritis with intra-articular and extra-articular deformity: a propensity score-matched analysis

Purpose Lateral unicompartmental arthroplasty (UKA) and distal femoral osteotomy (DFO) represent surgical solutions in cases of valgus malalignment and isolated lateral osteoarthritis (OA) of the knee. The aim of the present study was to assess the clinical results, complications, and the overall postoperative alignment of a series of DFO and lateral UKA with a minimum 2-year follow-up in active middle-aged patients. Methods Patients with valgus knee and isolated lateral OA who underwent opening-wedge DFO or UKA from 2017 to 2019 were reviewed. Each patient was characterized by a joint line convergence angle (JLCA) > 3 degrees and mechanical lateral distal femoral angle (mLDFA) < 87 degrees. We excluded patients who underwent meniscus or osteochondral allograft during DFO. The Oxford Knee Score (OKS), Knee Injury and Osteoarthritis Outcome Score (KOOS), complications, and postoperative alignment were assessed. Propensity score matching was used to identify comparable patients. Results The DFO and lateral UKA groups consisted of 29 patients each. No statistically significant differences in gender, age, body mass index (BMI), length of follow-up, or limb deformity were reported between the two groups. In the DFO group, OKS was reported to improve from 27.51 to 38.59 (p < 0.05) and KOOS from 51.14 to 67.2 (p < 0.05). Similarly, in the UKA group, OKS improved from 26.23 to 35.43 (p < 0.05) and KOOS from 50.12 to 65.91 (p < 0.05). However, the improvement in OKS and KOOS (delta) did not differ between groups (p = 0.35 and p = 0.95). The DFO and UKA groups were characterized by similar postoperative hip-knee-ankle (HKA) angle measurements of -3.26 and -3.00, respectively (p = 0.65). No patients in the UKA group underwent revision or other knee surgeries during follow-up. No infections were detected in either group. In the DFO group, no cases of nonunion or delayed union were reported. However, 40% of DFO patients underwent plate removal. One patient in each group was characterized by progression of medial OA with Kellgren-Lawrence (KL) grade > 3. Conclusion UKA and DFO represent an effective treatment in lateral knee OA with intra-articular and extra-articular deformity. Both surgeries were able to provide a significant and comparable clinical improvement. Level of evidence: III, comparative retrospective cohort study.