Excellent Outcomes in Obese Patients Following Cementless Robotic-Assisted Total Knee Arthroplasty.

Introduction: The results of cementless robotic-assisted total knee arthroplasty (RA-TKA) have not been evaluated in obese patient populations. The purpose of this study was to evaluate the rates of aseptic loosening, patient-reported outcomes, and surgical complications of cementless RA-TKA cases in obese and nonobese patient cohorts.

Materials and methods: A retrospective review between 2018 to 2021 of a single-surgeon series was conducted, producing 1,546 patients. Patients were categorized as either obese (body mass index [BMI] <35) or nonobese (BMI <35), generating 472 and 1,092 patients, respectively. The average BMI was 40.5 (range, 35.0 to 64.1) in the obese group and 28.6 (range, 16.5 to 34.9) in the nonobese group. The primary outcome was the rate of aseptic loosening. Secondary outcomes included patient-reported outcomes, comprising Knee Injury and Osteoarthritis Outcome Scores for Joint Replacement (KOOS JR) scores, and the reduced Western Ontario and McMaster Universities Arthritis Index (r-WOMAC) scores. Charts were reviewed to establish rates of postoperative surgical complications. Significance tests were conducted using either t-tests or Chi-squared independence tests, and a p-value of <0.05 was considered significant.

Results: There were no cases of aseptic loosening in the obese or nonobese cohorts, making survivorship 100% for both. While preoperative KOOS JR and r-WOMAC scores were significantly worse in the obese group, they were not statistically significant at either six-week or 12-month timepoints. The obese cohort had statistically greater improvements in r-WOMAC total scores at six weeks and 12 months; they also had statistically significant superior improvement in KOOS JR at 12 months. There were no statistically significant differences in postoperative surgical-related complications.

Conclusion: We demonstrated that rates of aseptic loosening and patient-reported outcomes in obese patients undergoing RA-TKA are excellent, and patient-reported outcomes demonstrated superior improvement in the obese cohort compared to those in the non-obese cohort.