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346-360-Adult Reconstruction Knee IV
Thursday, Mar 21, 2013, 10:54 AM -11:00 AM
McCormick Place, Room S105
The Effect of Obesity on Direct Medical Costs in Total Knee Arthroplasty
+Primary TKA (Knee)
, MD, MSc, Rochester, Minnesota
Sue L. Visscher
, PhD, Rochester, Minnesota
Walter K. Kremers
, PhD, Rochester, Minnesota
, MPH, Rochester, Minnesota
David G. Lewallen
, MD, Rochester, Minnesota
BACKGROUND: Obesity rates continue to rise in the United States. Total knee arthroplasty (TKA) procedures are increasingly performed in younger and obese patients. We sought to examine the effect of obesity on surgical complications, length of stay and direct medical costs in a large group of TKA patients.
METHODS: The study included 8,129 patients who had undergone 6,475 primary and 1,654 revision TKA procedures at a large U.S. medical center between 1/1/2000 and 9/31/2008. Patients with bilateral procedures during the 90-day window up to 90 days following index admission were excluded. Data on clinical, surgical characteristics and complications (infections, thrombovascular events, instability, fractures) were obtained from the original medical records and the institutional joint registry. Direct medical costs were calculated by using standardized, inflation-adjusted costs for services and procedures billed during hospitalization and the 90-day window. Patients were classified into eight groups based on body mass index (BMI). Study endpoints included hospital length of stay, occurrence of any complication during the 90-day time window and direct medical costs during hospitalization and the 90-day window. Endpoints were compared across the eight BMI categories in both unadjusted and multivariable risk-adjusted analyses. Logistic and linear regression models were used to determine the cost impact associated with increasing BMI and obesity.
RESULTS: BMI data were available for 99.5% of patients and ranged from 15 to 73. Among the eight BMI categories, mean length of stay and the direct medical costs were lowest for patients with a BMI of 25-30 and 30-35 kg/m
. Increasing BMI was not associated with a higher risk of complications (p=0.48) but it was associated with significantly longer hospital stays, after adjusting for age, sex, type of surgery and comorbidities. Adjusting for age, sex and type of surgery, every 10 unit increase in BMI beyond 25 kg/m
was associated with $648 and $724 higher hospitalization and 90-day costs, respectively. This association remained significant upon further adjustment for comorbidities where every 10 unit increase in BMI beyond 25 kg/m
was associated with $541 and $504 higher hospitalization and 90-day costs, respectively (p=0.0001 and 0.003). These associations remained significant when restricting analyses to primary TKA patients with degenerative arthritis. In these patients, every 10 unit increase in BMI beyond 25 kg/m
was associated with $575 and $510 higher hospitalization and 90-day costs, respectively (p=0.0001 and 0.005). In analyses restricted to patients with no comorbidities, the association with BMI was not significant, suggesting that the impact of obesity on costs was mediated largely through increased prevalence of comorbidities.
DISCUSSION AND CONCLUSIONS: In TKA, obesity does not seem to increase the overall risk of 90-day complications, but it is associated with longer hospital stays and costs. The effect of obesity is in part mediated through obesity-related comorbid conditions. Increasing prevalence of obesity in the TKA population likely contributes to the financial burden of TKA.
1 - Osteotech Zimmer; 4 - Pipeline Biomedical Holdings
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