Does body mass index affect the outcome of unicompartmental knee replacement?

D. W. Murray, H. Pandit, J. S. Weston-Simons, C. Jenkins, H. S. Gill, A. V. Lombardi, C. A. F. Dodd, K. R. Berend

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Background: Obesity is considered to be a contraindication for unicompartmental knee replacement (UKR). The aim was to study the impact of BMI on failure rate and clinical outcome of the Oxford mobile bearing UKR.

Method: Two thousand four hundred and thirty-eight medial Oxford UKRs were studied prospectively and divided into groups: BMI < 25 (n = 378), BMI 25 to < 30 (n = 856), BMI 30 to < 35 (n = 712), BMI 35 to < 40 (n = 286), and BMI 40 to < 45 (n = 126) and BMI ≥ 45 (n = 80).

Results: There was no significant difference in survival rate between groups. At a mean follow-up of 5 years (range 1–12 years) there was no significant difference in the Objective American Knee Society Score between groups. There was a significant (p < 0.01) trend with the Oxford Knee Score (OKS) and Functional American Knee Society Scores decreasing with increasing BMI. As there was an opposite trend (p < 0.01) in pre-operative OKS, the change in OKS increased with increasing BMI (p = 0.048). The mean age at surgery was significantly (p < 0.01) lower in patients with higher BMI.

Conclusions: Increasing BMI was not associated with an increasing failure rate. It was also not associated with a decreasing benefit from the operation. Therefore, a high BMI should not be considered a contra-indication to mobile bearing UKR.

Level of evidence :IV
Original languageEnglish
Pages (from-to)461-465
JournalThe Knee
Issue number6
Early online date26 Oct 2012
Publication statusPublished - Dec 2012


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