Long-Term Outcomes of Combined Medial Unicompartmental Knee Replacement and Anterior Cruciate Ligament Reconstruction in Middle-Aged Patients with ACL-Deficient Knees

<b>Background</b>: Successful unicompartmental knee arthroplasty (UKA) requires complete ligamentous competence, including the anterior cruciate ligament (ACL). The present study evaluated the long-term outcomes, complications, survival, and osteoarthritis (OA) progression in patients with medial femorotibial OA and ACL lesions undergoing simultaneous combined UKA and ACL reconstruction (ACLR). <b>Methods</b>: Patients who underwent simultaneous medial UKA and ACLR or revision ACLR from January 2004 to December 2021 were retrospectively reviewed. Inclusion criteria were a minimum follow-up period of 2 years and implantation of a cemented, fixed-bearing UKA. Outcomes were measured using the Knee Society Score (KSS), Tegner Activity Scale (TAS), University of California, Los Angeles (UCLA) Activity Score, and range of motion (ROM). <b>Results</b>: Thirty-four patients met the inclusion criteria. Mean follow-up was 11.7 years. Mean age was 52 years. Patients demonstrated significant improvements in KSS-C (from 52.8 ± 6.8 to 94.9 ± 7.9), KSS-F (from 58.3 ± 10.0 to 98.1 ± 4.2), TAS (from 0.7 ± 0.5 to 4.9 ± 1.1), UCLA (from 1.4 ± 0.6 to 6.6 ± 1.4), and ROM (from 109.1 ± 8.9 to 126.3 ± 6.1) (<i>p</i> < 0.01). Survival rate was 97.1% at 11.7 years. Lachman test results improved significantly (from 16 patients with grade II and 16 grade III to 13 grade 0 and 19 grade I, <i>p</i> < 0.01). No significant difference in functional outcomes was found between primary and revision ACLR groups; however, patients undergoing revision ACLR exhibited higher OA progression in the lateral compartment (<i>p</i> = 0.03). <b>Conclusions</b>: Simultaneous medial UKA and ACLR or revision ACLR led to excellent long-term outcomes, high survival rates, significant functional improvements, and minimal OA progression in the lateral compartment.