Unicompartmental knee replacement: Does the macroscopic status of the anterior cruciate ligament affect outcome?

Purpose: ACL damage is associated with progression of arthritis and whilst in the population undergoing joint replacement in the majority of cases the ACL is intact there is a wide spectrum of ACL disease. This study investigated whether the macroscopic status of the ACL affected functional outcome or survival following UKR.

Methods: The macroscopic status of the ACL was recorded in 820 cemented Oxford UKRs implanted by two surgeons for the recommended indications. The ACL was considered functionally normal in the setting of anteromedial tibial wear and macroscopically the ACL visually appeared normal or had synovial damage or longitudinal splits. The patients were followed up independently with a mean follow-up of 10.3years (range 5.3 to 16.6).

Results: More marked ACL macroscopic damage was significantly associated with increasing age, male gender and a more extensive anteromedial tibial defect. Patients with more ACL damage had a significantly lower pre-operative AKSS Objective Score, however no difference in AKSS-Functional or OKS was detected between groups. At 10years no difference in functional outcome or activity level was found between groups. Compared to those with a macroscopically normal ACL at 10years a significantly greater improvement from baseline OKS score was seen in patients with macroscopic ACL abnormalities. At 15years no difference in implant survival, or failure mechanism, was detected between groups.

Conclusion: The macroscopic status of the ACL does not affect long term functional outcomes or implant survival and in the setting of an intact ACL macroscopic status is not a contraindication to mobile bearing UKR.

Level of evidence: Level IV.