Obesity has no effect on outcomes following unicompartmental knee arthroplasty
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Although obesity has historically been described as a contraindication to UKA, improved outcomes with modern UKA implant designs have challenged this perception. The purpose of this study was to assess the influence of obesity on the outcomes of UKA with a robotic-assisted system at a minimum follow-up of 24 months with the hypothesis that obesity has no effect on robotic-assisted UKA outcomes.
There were 746 medial robotic-assisted UKAs (672 patients) with a mean age of 64 years (SD 11) and a mean follow-up time of 34.6 months (SD 7.8). Mean overall body mass index (BMI) was 32.1 kg/m2 (SD 6.5), and patients were stratified into seven weight categories according to the World Health Organization classification.
Patient BMI did not influence the rate of revision surgery to TKA (5.8 %) or conversion from InLay to OnLay design (1.7 %, n.s.). Mean postoperative Oxford knee score was 37 (SD 11) without correlation with BMI (n.s.). The type of prosthesis (InLay/OnLay) regardless of BMI had no influence on revision rate (n.s.). BMI did not influence 90-day readmissions (4.4 %, n.s.), but showed significant correlation with higher opioid medication requirements and a higher number of physical therapy session needed to reach discharge goals (p = 0.031).
These findings suggest that BMI does not influence clinical outcomes and readmission rates of robotic-assisted UKA at mid-term. The classic contraindication of BMI >30 kg/m2 may not be justified with the use of modern UKA designs or techniques.
Level of evidence
KeywordsKnee replacement Robotic assisted Navigation Medial UKA
Conflict of interest
The authors JFP, MAA, TMS, DNB, AH and MA report no conflict of interest. The authors RHJ and GGP have received financial support from MAKO Surgical Corp., Ft Lauderdale, FL. RHJ and GGP have received payment as consultants. All authors certify that this investigation was performed in conformity with ethical principles of research. Institutional review board approval was obtained prior to the study.
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