Medial Unicompartmental Knee Arthroplasty for Osteonecrosis: A Cohort Study Comparing Cemented and Cementless Fixation.

BACKGROUND

Osteonecrosis (ON) of the knee commonly affects the medial femoral condyle, leading to secondary unicompartmental arthritis. While most studies on unicompartmental knee arthroplasty (UKA) in patients who have ON focus on cemented fixation, the outcomes of cementless UKA remain unknown. This study evaluated survival, functional and radiological outcomes, and assessed potential differences for cemented and cementless medial mobile-bearing UKA in patients who had ON.

METHODS

This retrospective, single-center study analyzed 119 patients who underwent medial UKA for ON between 2020 and 2022, with a minimum follow-up of two years. Patients were stratified into cemented (n = 63, women/men 71/29%, mean age 70 ± 9 years, BMI 29 ± 4) and cementless (n = 56, women/men 34/66%, mean age 72 ± 8 years, BMI 28 ± 4) groups. Demographics were similar between groups, except for sex, with more men in the cementless UKA group (P < 0.001). Kaplan-Meier survival analysis compared survival rates for aseptic loosening, implant revision (exchange of the femoral or tibial component), and any reoperation. Functional outcomes were assessed using the Oxford Knee Score (OKS) and the UCLA (University of California, Los Angeles) Activity Score.

RESULTS

At 50 months, cumulative survival rates showed no significant differences between cemented and cementless UKA for aseptic loosening (100 versus 97.7%; P = 0.35), implant revision (97.5 versus 93.3%; P = 0.36), or any reoperation (92.1 versus 87.0%; P = 0.35). There was one case of aseptic tibial subsidence that occurred in the cementless group in a patient who had femoral ON. Functional outcomes were excellent in both groups, with no significant differences in OKS (cemented/cementless: 42.6 ± 5.4 versus 43.5 ± 6.3; P = 0.12) or UCLA Activity Scores (6.1 ± 1.0 versus 6.1 ± 1.2; P = 0.57).

CONCLUSION

Cementless medial mobile-bearing UKA is a safe treatment option for ON in the medial compartment, offering stable primary fixation and implant survival comparable to cemented fixation. However, future research with sex-balanced cohorts and extended follow-up is needed to confirm these findings.