The Presence of Osteonecrosis in Patients Who Have Systemic Lupus Erythematosus Undergoing Total Knee Arthroplasty Is Not Associated With Worse Outcomes.

BACKGROUND

Systemic lupus erythematosus (SLE) patients seeking total knee arthroplasty (TKA) typically present with secondary osteonecrosis of the knee. Whether osteonecrosis negatively affects TKA outcomes in this high-risk population has not previously been studied. This study aimed to compare TKA survivorship, clinical outcomes, and postoperative complication rates between SLE patients who did and did not have osteonecrosis.

METHODS

A retrospective analysis of SLE patients undergoing TKA between 2015 and 2023 at a large academic institution was conducted. The cohort was stratified by the presence of osteonecrosis on preoperative X-ray and magnetic resonance imaging when available. Imaging diagnosis was validated by an experienced musculoskeletal radiologist. Patient characteristics, clinical outcomes, and patient-reported outcome measures were compared between groups using univariable and multivariable analyses. We identified 179 knees in 147 patients who had lupus undergoing TKA. There were twelve percent (n = 21 of 179) of the knees that had osteonecrosis. The mean follow-up was 4.8 years (range, 1.0 to 9.1).

RESULTS

Osteonecrosis was associated with younger age (P < 0.01) and lower body mass index (P = 0.04). Osteonecrosis was not a risk factor for postoperative readmission or revision, but younger age was associated with increased risk for both (P = 0.02 and P < 0.01, respectively). The 5-year TKA revision-free survivorship was 94.9% [95% confidence interval: 91.4 to 98.5] for all SLE patients and 95.2% [95% confidence interval: 86.6 to 100.0] for SLE with osteonecrosis. All patient-reported outcome measures improved from preoperative baseline (P < 0.01), irrespective of osteonecrosis. The magnetic resonance imaging patterns of osteonecrosis were categorized into three distinct types to guide surgical planning: (A) primarily meta-diaphyseal; (B) meta-diaphyseal with articular extension; and (C) severe deformity or bone loss.

CONCLUSIONS

Osteonecrosis in SLE patients was not associated with worse TKA outcomes at a mean follow-up of five years. Longer-term durability of TKA in these patients requires further study.