Extremes of body mass index have significant impact on complications, readmissions, and utilization of post-acute services after primary total hip arthroplasty.

AIMS: High body mass index (BMI) is associated with increased rates of complications in primary total hip arthroplasty (THA), but less is known about its impact on cost. The effects of low BMI on outcomes and cost are less understood. This study evaluated the relationship between BMI, inpatient costs, complications, readmissions, and utilization of post-acute services.

METHODS: A retrospective database analysis of 40,913 primary THAs performed between January 2013 and December 2017 in 29 hospitals was conducted. Operating time, length of stay (LOS), complication rate, 30-day readmission rate, inpatient cost, and utilization of post-acute services were measured and compared in relation to patient BMI.

RESULTS: Mean operating time increased with BMI and for BMI > 50 kg/m2 was approximately twice that of BMI 10 kg/m2 to 15 kg/m2 . Mean inpatient cost did not vary significantly with BMI. Mean total reimbursement was lowest for the lowest BMI cohort and increased with BMI. Mean LOS was greatest at the extremes of BMI (4.0 days for BMI 10 kg/m2 to 15 kg/m2 ; 3.75 days for BMI > 50 kg/m2 ) and twice that of normal BMI. Mean complication rates were greatest in the lowest BMI cohort (16% for BMI 10 kg/m2 to 15 kg/m2 ) and five times the mean rate of complications in the normal BMI cohorts. Furthermore, 30-day readmissions were greatest in the highest BMI cohort (10% for BMI > 50 kg/m2 ) and five times the rate for normal BMI patients.

CONCLUSION: LOS, complications, and 30-day readmissions all increase at the extremes of BMI and appear to be greater than those of patients with normal BMI. The lowest BMI patients had the lowest payment for inpatient stay yet were at considerable risk for complications and readmission. Patients with extreme BMI should be counselled about their increased risk of complications for THA and nutritional status/obesity optimized preoperatively if possible. Cite this article: Bone Joint J 2020;102-B(7 Supple B):62-70.