Anterior cruciate ligament reconstruction in association with medial unicompartmental knee replacement: a retrospective study comparing clinical and radiological outcomes of two different implant design

Purpose Unicompartmental knee arthroplasty (UKA) combined with anterior cruciate ligament (ACL) reconstruction has recently been suggested as a feasible treatment option for young and active patients with medial compartment osteoarthritis (OA) and ACL deficiency. The aim of this study is to evaluate retrospectively the outcomes of two different implant designs in patients with medial OA secondary to traumatic ACL rupture, who underwent combined ACL reconstruction and unicompartmental knee replacement. Methods From January 2007, to December 2013, 24 patients with medial OA secondary to ACL rupture underwent medial unicompartmental knee arthroplasty (UKA) and ACL reconstruction. Nine patients received a mobile bearing UKA (Group 1) and fifteen a fixed-bearing one (Group 2). The mean follow-up was 53 ± 8.3 months for Group 1 and 42 ± 6.7 months for Group 2. Knee Society Score (KSS), Western Ontario and McMaster Index of Osteoarthritis (WOMAC) index and radiological evaluation used to assess the implant loosening alignment of the knee joint and tibial slope were recorded pre-operatively and at the last follow-up. Results At the final follow-up, all patients showed statistically significant clinical improvements with respect to the pre-operative values ( p < 0.05). No significant difference was observed in WOMAC index and KSS both objective and functional between groups at the last follow-up (KSS obj. 73.4 ± 9.3 vs 77.3 ± 10.5; KSS funct. 86.2 ± 6.2 vs 84.7 ± 5.9; WOMAC 79.3 ± 7.3 vs 81.3 ± 7.6 for Group 1 and 2, respectively). No differences in radiolucent lines were found between the groups. Conclusion The use of different prosthesis design (fixed- or mobile-bearing) during a combined procedure of ACL reconstruction and medial unicompartmental arthroplasty does not affect the middle-term clinical and radiological outcomes.