Underweight patients experience higher inpatient complication and mortality rates following acetabular fracture.

Purpose: Underweight patients experience poor outcomes after elective orthopaedic procedures. The effect of underweight body mass index (BMI) on complications after acetabular fracture is not well-described. We evaluate if underweight status is associated with inpatient complications after acetabular fractures.

Methods: Adult patients (≥ 18 years) presenting with acetabular fracture between 2015 and 2019 were identified from Trauma Quality Program data. Adjusted odds (aOR) of any inpatient complication or mortality were compared between patients with underweight BMI (< 18.5 kg/m) and normal BMI (18.5-25 kg/m) using multivariable logistic regression and stratifying by age ≥ 65 years.

Results: The 1299 underweight patients aged ≥ 65 years compared to 11,629 normal weight patients experienced a 1.2-times and 2.7-times greater aOR of any complication (38.6% vs. 36.6%, p = 0.010) and inpatient mortality (7.9% vs. 4.2%, p < 0.001), respectively. The 1688 underweight patients aged 18-64 years compared to 24,762 normal weight patients experienced a 1.2-times and 1.5-times greater aOR of any inpatient complication (38.9% vs. 34.8%, aOR p = 0.006) and inpatient mortality (4.1% vs. 2.5%, p < 0.001), respectively.

Conclusion: Underweight adult patients with acetabular fracture are at increased risk for inpatient complications and mortality, particularly those ≥ 65 years old.

Level Of Evidence: Prognostic Level III.