Combined unicompartmental knee arthroplasty and ACL reconstruction for medial knee osteoarthritis complicated by ACL insufficiency: superior early functional recovery with LARS artificial ligament and comparable mid-term results versus autologous tendon.

BACKGROUND: To evaluate the outcomes of fixed-bearing medial unicompartmental knee arthro plasty (UKA) combined with anterior cruciate ligament (ACL) reconstruction using either a LARS artificial ligament or autologous tendon graft, compared with isolated UKA in ACL-intact knees. METHODS: Patients who underwent UKA combined with ACL reconstruction from January 2019 to December 2021 were retrospectively reviewed. They were divided into the LARS group (L-UKA, n = 20) and the autologous tendon group (A-UKA, n = 20). A contemporaneous cohort of patients who underwent isolated UKA with an intact ACL was matched at a 1:1:1 ratio (UKA, n = 20). Range of motion (ROM), Knee Society Score (KSS), Oxford Knee Score (OKS), and Forgotten Joint Score (FJS) were compared. Radiographic parameters included the hip-knee-ankle angle (HKA), posterior tibial slope (PTS), and anterior tibial translation (ATT). RESULTS: The mean follow-up was 61.07 ± 3.90 months. Baseline characteristics were comparable among the three groups. At final follow-up, ROM, KSS and OKS improved significantly in all groups compared with preoperative values (P < 0.01), with no significant intergroup differences (P > 0.05). Final HKA, PTS, and ATT were also comparable among groups. Preoperative ATT was significantly greater in the L-UKA and A-UKA groups than in the isolated UKA group (P < 0.01), but normalized postoperatively. At 1 month, ROM and KSS were significantly better in the L-UKA group than in the A-UKA group (P < 0.05). Two patients in the A-UKA group had donor-site pain. No implant loosening or lateral compartment OA progression occurred, and implant survivorship was 100%. CONCLUSION: UKA combined with ACL reconstruction using either LARS artificial ligament or autologous tendon graft effectively corrected ATT and achieved mid-term outcomes comparable to isolated UKA. LARS avoided donor-site morbidity and provided better early functional recovery, although its long-term safety requires further validation.