Lateral and Medial Unicompartmental Knee Arthroplasty Have Similar Reoperation Rates, Patient-Reported Outcomes, and Functional Performance in a Two-Year Follow-Up Period.

BACKGROUND

The primary objective was to compare 2-year postoperative outcomes of lateral unicompartmental knee arthroplasty (LUKA) to medial unicompartmental knee arthroplasty (MUKA).

METHODS

In this retrospective cohort study, adult patients diagnosed with isolated medial or lateral compartmental knee osteoarthritis who underwent unicompartmental knee arthroplasty between 2018 and 2022 at one of two academic medical centers were investigated. Cohorts were generated using propensity score matching based on age, sex, body mass index, and year of surgery. Preoperative and postoperative range of motion, Knee Injury and Osteoarthritis Outcome Score (KOOS), and Patient-Reported Outcomes Measurement Information System (PROMIS) physical function were compared in addition to reoperation rates and postoperative complications. From a cohort of 788 patients who had unicompartmental knee arthroplasty, 698 patients met study criteria. The two cohorts of 124 cases of MUKA and LUKA were generated after propensity score matching balanced on age, sex, body mass index, and year of surgery.

RESULTS

The KOOS and PROMIS showed an upward trend in both cohorts that were not significantly different at any time point (KOOS: P = 0.45, 0.16, 0.73, and 0.15 and PROMIS: P = 0.40, 0.74, 0.11, and 0.97 at three months, six months, one year, and two years, respectively). Reoperations were not statistically different between cohorts at two years, with LUKAs having two conversions to total arthroplasty and MUKAs having one. All-cause returns to the emergency department and infections requiring irrigation and debridement were similar between cohorts (P > 0.05).

CONCLUSIONS

Lateral and medial unicompartmental knee arthroplasty led to an equivalent functional improvement in range of motion and patient-reported outcomes with similar rates of reoperation and infection within two years of operation. These findings can guide patient expectations within a 2-year follow-up period after unicompartmental arthroplasty and guide surgeons' decisions to pursue lateral unicompartmental knee arthroplasty as opposed to other surgical options.