The Journal of arthroplastyApr 16, 2016

Hospital outcomes and resource use after joint replacement in underweight versus very obese patients

GLP-1 Therapies Weekly Brief ↗PubMed ↗DOI ↗

Updated Apr 3, 2026

Abstract

Underweight patients undergoing total joint arthroplasty may incur significantly higher hospital costs and complications compared to morbidly obese patients.

Underweight patients showed a higher risk for developing postoperative anemia, with an odds ratio of 3.1 for total knee arthroplasty (TKA) and 1.8 for total hip arthroplasty (THA).
Underweight THA candidates had a greater risk for deep venous thrombosis, with 75.36% of cases observed in this group compared to 24.64% in morbidly obese patients.
Total hospital charges for underweight TKA patients were higher at USD 51,368.90 compared to USD 40,128.80 for morbidly obese patients, with a statistically significant difference.
Total hospital charges for underweight THA patients were also higher at USD 57,451.8 compared to USD 42,776.9 for morbidly obese patients, with a significant P value.
Length of stay was longer for underweight THA patients, averaging 4.6 days versus 3.5 days for morbidly obese patients.

Simplified

BACKGROUND: As orthopedic surgeons search for objective measures that predict total joint arthroplasty (TJA) outcomes, body mass index may aid in risk stratification. The purpose of this study was to compare in-hospital TJA outcomes and resource consumption amongst underweight (body mass index ≤19 kg/m(2)) and morbidly obese patients (≥40 kg/m(2)).

METHODS: Discharge data from 2006 to 2012 National Inpatient Sample were used for this study. A total of 1503 total hip arthroplasty (THA) and 956 total knee arthroplasty (TKA) patients were divided into 2 cohorts, underweight (≤19 kg/m(2)) and morbidly obese (≥40 kg/m(2)). Patients were matched by gender and 27 comorbidities by use of Elixhauser Comorbidity Index. Patients were compared for 13 in-hospital postoperative complications, length of stay, total hospital charge, and disposition. Multivariate analyses were generated by SAS software. Significance was assigned at P value <.05.

RESULTS: Underweight patients undergoing primary TJA had higher risk for developing postoperative anemia compared with morbidly obese patients (TKA: odds ratio [OR], 3.1; 95% CI, 2.3-4.1; THA: OR, 1.8; 95% CI, 1.5-2.3). Underweight THA candidates displayed greater risk for deep venous thrombosis (75.36% vs 24.64%; OR, 3.1; 95% CI, 1.1-8.4). Underweight TJA patients were charged more (TKA: USD 51,368.90 vs USD 40,128.80, P = .001, THA: USD 57,451.8 vs USD 42,776.9, P < .001) compared to the morbidly obese patients. Length of stay was significantly longer for underweight THA patients (4.6 days vs 3.5 days, P = .008) compared to morbidly obese counterparts.

CONCLUSION: Our results indicate underweight, compared to morbidly obese, TJA patients are at a greater risk for postoperative anemia and consume more resources.

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Hospital outcomes and resource use after joint replacement in underweight versus very obese patients

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