Patient-specific vs. Oxford microplasty instrumentation in unicompartmental knee arthroplasty: a randomized...

The success of unicompartmental knee arthroplasty (UKA) in treating end-stage knee osteoarthritis is mainly based on the surgical instruments and surgeon's experience. The purpose of this randomized controlled trial was to compare the efficacy of patient-specific instrumentation (PSI) assisted UKA by inexperienced surgeon on the learning curve with conventional Oxford microplasty instrumentation (MPI) assisted UKA.

We performed a prospective study at a single high-volume orthopaedic hospital. Patients with end-stage medial tibiofemoral osteoarthritis were assessed for eligibility and randomly assigned to undergo either PSI-assisted UKA performed by inexperienced surgeons (PSI group) or MPI-assisted UKA performed by experienced surgeons (MPI group) at a 1:1 ratio. The primary outcome was the femoral varus/valgus angle using the mean score on the first day after surgery. The secondary outcomes included the femoral prosthesis flexion/extension angle, tibial varus/valgus angle, tibial posterior slope angle, and the hip-knee-ankle angle (HKAA). The Knee Society Score (KSS) and Hospital for Special Surgery (HSS) score were assessed at one, three, six, and 12 months. Mixed-effects modelling was used to analyze repeated measurements.

A total of 73 participants (37 in the PSI group and 36 in the MPI group) were enrolled from June 2021 to July 2023. No patients were lost to follow-up. No significant between-group differences were found in the femoral component varus and valgus angle, flexion and extension angle, tibial component varus and valgus angle, tibial posterior slope angle, or hip-knee-ankle angle (all P > 0.05). At the 12-month follow-up, the PSI group and MPI group achieved mean KSSs of 93.4 points (95% CI, 88.6-97.8) and 93.6 points (95% CI, 89.1-98.4), respectively. There were no significant between-group differences in the KSS and HSS score improvements from baseline to each follow-up point.

The PSI-assisted UKA performed by inexperienced surgeon on a learning curve can yield excellent radiographic and functional outcomes in short-term follow-up, despite not demonstrating superior clinical outcomes to MPI-assisted UKA performed by an experienced surgeon. The PSI could potentially serve as an alternative instrumentation for UKA beginners with low-volume surgical caseload.