Retrospective Cohort Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Oct 18, 2016; 7(10): 664-669
Published online Oct 18, 2016. doi: 10.5312/wjo.v7.i10.664
Effect of body mass index on functional outcome in primary total knee arthroplasty - a single institution analysis of 2180 primary total knee replacements
Shane C O’Neill, Joseph S Butler, Adam Daly, Darren F Lui, Patrick Kenny
Shane C O’Neill, Joseph S Butler, Adam Daly, Darren F Lui, Patrick Kenny, Department of Orthopaedics, Cappagh National Orthopaedic Hospital, Dublin 11, Ireland
Author contributions: All the authors contributed to the paper.
Institutional review board statement: The study was reviewed and approved for publication by our Institutional Reviewer.
Informed consent statement: All study participants provided informed written consent about personal and medical data collection prior to enrolment.
Conflict-of-interest statement: All the authors have no conflict of interest related to the manuscript.
Data sharing statement: The original anonymous dataset is available on request from the corresponding author at shaneconeill@rcsi.ie.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Shane C O’Neill, MRCS, MCh, Department of Orthopaedics, Cappagh National Orthopaedic Hospital, Finglas, Dublin 11, Ireland. shaneconeill@rcsi.ie
Telephone: +353-1-8140400
Received: February 15, 2016
Peer-review started: February 16, 2016
First decision: March 24, 2016
Revised: June 20, 2016
Accepted: August 11, 2016
Article in press: August 15, 2016
Published online: October 18, 2016
Processing time: 240 Days and 8 Hours
Abstract
AIM

To evaluate the effect of body mass index (BMI) on short-term functional outcome and complications in primary total knee arthroplasty.

METHODS

All patients undergoing primary total knee arthroplasty at a single institution between 2007 and 2013 were identified from a prospective arthroplasty database. 2180 patients were included in the study. Age, gender, BMI, pre- and post-operative functional scores [Western Ontario and McMaster University Arthritis Index (WOMAC) and SF-36], complications and revision rate were recorded. Patients were grouped according to the WHO BMI classification. The functional outcome of the normal weight cohort (BMI < 25) was compared to the overweight and obese (BMI ≥ 25) cohort. A separate sub-group analysis was performed comparing all five WHO BMI groups; Normal weight, overweight, class 1 obese, class 2 obese and class 3 obese.

RESULTS

With a mean age of 67.89 (28-92), 2180 primary total knee replacements were included. 64.36% (1403) were female. The mean BMI was 31.86 (18-52). Ninty-three percent of patients were either overweight or obese. Mean follow-up 19.33 mo (6-60 mo). There was no significant difference in pre or post-operative WOMAC score in the normal weight (BMI < 25) cohort compared to patients with a BMI ≥ 25 (P > 0.05). Sub-group analysis revealed significantly worse WOMAC scores in class 2 obese 30.80 compared to overweight 25.80 (P < 0.01) and class 1 obese 25.50 (P < 0.01). Similarly, there were significantly worse SF-36 scores in class 2 obese 58.16 compared to overweight 63.93 (P < 0.01) and class 1 obese 63.65 (P < 0.01) There were 32 (1.47%) superficial infections, 9 (0.41%) deep infections and 19 (0.87%) revisions overall with no complications or revisions in the normal weight cohort (BMI < 25).

CONCLUSION

Post-operative functional outcome was not influenced by BMI comparing normal weight individuals with BMI > 25. Patients should not be denied total knee arthroplasty based solely on weight alone.

Keywords: Total knee replacement; Body mass index; Total knee arthroplasty

Core tip: We assessed the effect of body mass index (BMI) on short-term functional outcome of 2180 patients that underwent primary total knee arthroplasty at a single institution. Functional outcome was assessed using the Western Ontario and McMaster University Arthritis Index and SF-36 outcome tools. Patients were stratified according to BMI using the WHO classification and results compared. We found no statistical difference in our primary outcome measure, functional outcome of normal weight individuals compared to those with a BMI greater than 25.