Clinical Outcomes and Survivorship of Lateral Unicompartmental Knee Arthroplasty: Does Surgical Approach Matter?

Background: Lateral unicompartmental knee arthroplasty (UKA) has been shown to be an effective procedure to treat isolated lateral compartment osteoarthritis with excellent long-term survivorship. Whether a medial parapatellar approach or a lateral parapatellar approach is superior in lateral UKA is unknown. The purpose of this study was to determine if there is a difference in intermediate-term clinical outcomes in patients undergoing lateral UKA through a lateral vs medial parapatellar approach.

Methods: We retrospectively reviewed a consecutive series of 65 patients who underwent lateral UKA with a minimum of 2-year follow-up. Fifty-two patients (80%) had a lateral approach and 13 (20%) a medial parapatellar approach. Patient demographics, preoperative and postoperative radiographic findings, need for revision surgery, Knee Society Score, and range of motion were assessed.

Results: Overall survivorship was 94% at a mean of 82 months; with the sample size available for study, there was no difference in survivorship between the groups. There was no difference in Knee Society Score or revision to total knee arthroplasty (5% vs 7%, P = 1.000) between the medial and lateral approach groups. Comparatively, the lateral approach group did have significantly greater postoperative flexion (123.6° vs 116.5°, P = .006) and greater improvement in flexion from preoperative measurements (3.0 vs -8.0°, P = .010).

Conclusion: Although our sample size was small, we could not demonstrate a difference in revision rates or clinical outcome scores when comparing a lateral or a medial approach with lateral UKA at intermediate-term follow-up. A lateral approach did have greater postoperative flexion, but its clinical significance remains undetermined.