Abstract
Introduction
Published literature that examined pre-operative Body Mass Index (BMI) with Total Knee Arthroplasty (TKA) outcomes have shown conflicting data. Some show that higher BMI and is associated with poorer post-TKA function and HRQoL outcomes, but not others.
The aim of our analyses is to identify the relationship of pre-operative obesity with the outcomes of TKA, including physical and mental functional limitations.
Methods
We performed a prospective analysis of a consecutive series of 191 patients, who had underwent TKA from March 2006 to February 2011, performed by a single surgeon, at Singapore General Hospital, Singapore. Patients were eligible if they had met the following criteria: primary, unilateral TKA, using fixed bearing, posterior stabilized prostheses, under computer assisted surgery system. Patients were reviewed clinically at 6 months and 2 years post-operatively.
Patients were stratified into non-obese (BMI <30 kg/m2), mildly obese (BMI 30 to 35) and highly obese (BMI ≥35) groups. Outcome measures evaluated include: SF-36, Oxford knee score and Knee Society Score.
Results
44 patients (23%) were obese, further stratified into 35 (18%) mildly obese patients, and 9 (5%) highly obese patients. Obese and mildly obese patients had poorer knee flexion degrees when compared to non-obese patients, although knee extension degrees were similar. Knee ranges of motion were poorer in obese and mildly obese patients than in non-obese patients.
Knee Society Scores
KSS function and knee outcome scores were significantly better in all patient groups, at 2 years post TKA compared to pre-operatively. At 6 months, all KSS function and knee scores were also better in all subgroups than pre-operative scores, with the exception of the highly obese group which did not show a significant difference.
Obese and mildly obese patients had worse knee scores compared to non-obese patients pre-operatively, but similar scores post-operatively at 6 months and 2 years. Function scores for highly obese compared to non obese patients were significantly worse at the 6 month assessment, although not at the pre-operative and 2 years post-operative assessments.
Oxford knee scores
OKS scores were significantly better in all patient groups, at 6 months and 2 years post TKA compared to pre-operative scores. Pre-operative OKS scores are worse in obese compared to non-obese patients, but similar at 6 months and 2 years. Highly obese patients had worse OKS scores pre-operatively, and at 6 months, but not at 2 years.
SF-36 scores
SF-36 physical and mental scores were better in obese and mildly obese patients compared to non-obese patients, at 6 months and 2 years post-operatively. Highly obese patients had worse physical and mental scores at 2 years. Obese patients had poorer physical scores pre-operatively and at 6 months, but not at 2 years. Highly obese patients had poorer physical scores only at 6 months post-operatively. Highly obese patients had poorer mental scores pre-operatively compared to non-obese patients.
Conclusion
Obese patients in our study who had poorer functional scores pre-operatively also had generally poorer functional scores 6 months post TKA. However, this difference was not observed at 2 years post TKA.
