The impact of anterior cruciate ligament deficiency severity on the outcomes of fixed-bearing unicompartmental knee arthroplasty: a retrospective study

Anterior cruciate ligament deficiency (ACLD) has traditionally been regarded as a contraindication for unicompartmental knee arthroplasty (UKA). However, advancements in surgical techniques and improvements in prosthetic manufacturing have challenged this notion. Controversy persists regarding whether the anterior cruciate ligament (ACL) influences the postoperative outcomes of fixed-bearing (FB) UKA. This study aimed to evaluate the impact of varying severities of ACLD on the clinical outcomes of FB-UKA. This retrospective analysis included 81 patients (87 knees) who underwent FB-UKA for anteromedial osteoarthritis (AMOA). Patients were categorised into three groups on the basis of preoperative MRI and intraoperative findings: the intact ACL group (31 knees), the partial ACLD group (39 knees), and the complete ACLD group (17 knees). Patient demographics (age, body mass index [BMI]), preoperative hip-knee-ankle angle (HKA), follow-up duration, and preoperative and last follow-up data, collected more than one year postoperatively, were recorded, including the Hospital for Special Surgery knee score (HSS), Lysholm score, visual analogue scale (VAS) for pain, range of motion (ROM), postoperative X-ray assessment of the position of the femoral component relative to the tibial component, as well as evaluation of radiolucent lines on the postoperative X-rays. Statistical analyses were conducted to determine differences in clinical outcomes, including pre-and postoperative changes, among the three groups. Postoperative complications, such as infection, aseptic loosening, prosthetic dislocation, or periprosthetic fractures requiring revision surgery, were recorded. There were no significant differences among the three groups in terms of age, BMI, follow-up duration, preoperative HKA, baseline Lysholm score, HSS knee score, VAS score, or ROM (P > 0.05). Postoperatively, all three groups showed significant improvements in the Lysholm score, HSS knee score, VAS score, and ROM (P < 0.001), with no significant differences in the extent of improvement among the groups (P > 0.05). The position of the femoral component relative to the tibial component did not differ significantly among the groups (P > 0.05), and no radiolucent lines were observed in any of the patients. No patients experienced complications such as infection, aseptic loosening, periprosthetic fractures, or prosthetic dislocations that required revision surgery at the latest follow-up. FB-UKA is a viable surgical option for the treatment of AMOA. For patients with AMOA and stable anteroposterior knee alignment, ACLD does not adversely affect short- to midterm outcomes following FB-UKA. Even in cases of partial or complete ACLD, careful patient selection and optimised surgical techniques can yield outcomes comparable to those in patients with intact ACLs.