Lateral unicompartmental knee arthroplasty through a medial parapatellar approach: surgical technique and mid-term results in 108 patients

Lateral unicompartmental knee arthroplasty (L-UKA) is typically performed through a lateral parapatellar approach. Few studies of L-UKA performed through a medial approach are published. We aimed to present surgical tips, and mid-term clinical results and survivorships of L-UKA performed through a medial approach. We retrospectively reviewed single-centre single-surgeon data from L-UKA using medial parapatellar approach between 2016 and 2023. Patients with follow-up < 12 months were excluded. Primary endpoint was implant survivorship (time from index surgery to revision or last follow-up). Secondary endpoints included the rates of patients achieving Patient Acceptable Symptom State (PASS) thresholds: ≥ 67.5 for Knee Society Score-Knee (KSS-K) and ≥ 70.5 for Knee Society Score-Function (KSS-F). Survival analysis was used for implant survivorship. Logistic regression was performed for factors potentially associated with failure to achieve the PASS thresholds. Significance was set at P < 0.05. Among 110 patients initially identified, two died before 12-month follow-up and were excluded from clinical outcome analysis, leaving 108 patients for functional assessment at a mean 47.6 months ± 24.5 of follow-up (range 12–96.7 months). No complications were reported during hospitalization. There were four failures (3.7%) overall: two cases (1.8%) of OA progression, one (0.9%) of aseptic loosening, and one case (0.9%) of periprosthetic fracture of the medial condyle requiring revision surgery. All 110 patients were included in survival analysis, with the 2 patients who died before 12 months included as censored data at time of death. The overall 7-year survivorship was 97.2% (95% CI 94.2–100%), declining to 92.1% at 84 months when the last revision occurred. PASS thresholds were achieved by 99.0% patients for KSS-Knee and by 86.1% for the KSS-F. Patient age was a significant predictor of failure to achieve functional PASS thresholds (OR = 1.3 per year, 95% CI 1.0–1.6, p = 0.036). L-UKA performed through a medial parapatellar approach yielded excellent clinical outcomes and survivorship at mid-term follow-up. IV (retrospective case series).