Introduction

Obesity is a major risk factor for knee osteoarthritis, seen seven times more frequently when compared to people with a body mass index (BMI) less than 25. Complications in total knee arthroplasty (TKA) are also significantly higher with a 3.7 times greater risk of periprosthetic joint infection in all TKA in those with a BMI over 40. This study aimed to evaluate the peri-operative outcomes of patients within different BMI ranges undergoing TKA in a single centre.

Methods

All patients undergoing TKA between January 2019 and March 2020 were included in a retrospective review using UK National Joint Registry data and hospital records recording demographics, lengths of stay (LOS), complication rates (clavien-dindo definition), and readmissions within 60 days.

Results

The full cohort included 528 TKA. Comparison of the group of 87 (17%) with a BMI >40 (mean 43 ± 3.2 [40 – 52.5]) to those with BMI <40 showed they were both significantly younger (mean age 64.6 versus 70.2, p < 0.001), and with a higher mean ASA (2.7 versus 2.4, p < 0.001). In the BMI >40 group a significantly higher LOS was seen (mean 5.49 vs 4.42 days, p = 0.004), and they were more likely to stay >7 days (11% vs 5% p = 0.04). Significantly higher rates of reoperation (8% vs 2%, p = 0.012), including four re-operations for infection in the high BMI group and two in the lower BMI group were seen. Readmissions within 60 days were not significantly different between groups (9.8% vs 10.3% p=0.85).

Discussion

There is a large proportion of patients suitable for TKA with high BMI, and this was seen in younger patients with more co-morbidities. The risk of a prolonged LOS and higher reoperation rate is seen in this group. The results suggest an urgent need for further research in the management and optimisation of patients with obesity and knee osteoarthritis.