Presentation Abstract

Session: ARK Posters-Adult Reconstruction Knee Posters
Date/Time: Tuesday, Feb 07, 2012, 8:00 AM - 6:00 PM
Poster Hall/ Multimedia/ Scientific Exhibits: Tuesday, Feb 7 - Saturday, Feb 11, 2012, 8:00 AM - 6:00 PM
Presentation Number: P149
Posterboard Number: P149
Title: Cost and Disease Outcomes of Total Knee Arthroplasty Patients in the Medicare Population
Classification: Adult Reconstruction Knee
Keywords: Total Knee Arthroplasty General Outcome; Total Knee Arthroplasty Results; Economic / Cost Analysis; Outcomes
Author(s): Scott T. Lovald, PhD, MBA, Philadelphia, Pennsylvania, United States
Edmund Lau, MS, Menlo Park, California, United States
Kevin Ong, PhD, PE, Philadelphia, Pennsylvania, United States
Steven M. Kurtz, PhD, Philadelphia, Pennsylvania, United States
Jordana K. Schmier, MA, Alexandria, Virginia, United States
Javad Parvizi, MD, Philadelphia, Pennsylvania, United States
Kevin J. Bozic, MD, MBA, San Francisco, California, United States
Abstract: INTRODUCTIONDespite the prevalence and projected increase in osteoarthritis (OA) in the elderly, there are little data that quantify the risks and benefits of cost and quality of life for knee arthroplasty treatments. The purpose of this study is to compare differences in cost and health outcomes between osteoarthritic patients who undergo joint replacement therapy and those who do not.
METHODSThe Medicare 5% sample was used to identify patients with OA using the ICD-9 codes within the 715.X6 family during 1997-2009. All OA patients were separated into non-arthroplasty and arthroplasty (indicated by ICD-9 code 81.54) groups. Outcomes of interest included average annual payments adjusted to Jan-2011$, mortality, and new diagnoses of congestive heart failure, diabetes, and depression. Differences in costs and risk ratios for each outcome were adjusted using logistic regression for age, sex, race, buy-in status, region, and Charlson score. The results were compared at fixed periods of one year, three years, five years, and seven years after surgery.
RESULTSThere were 80,629 non-TKA patients and 53,829 TKA patients with one-year follow-up data. These numbers dropped to 39,183 non-TKA and 25,904 TKA patients at seven years. The seven-year cumulative average Medicare payments for all treatments for all medical care were $63,940 for the non-TKA group and $83,783 for the TKA group, an incremental seven-year cost of $19,843. The mortality hazard ratio of the TKA group ranged from 0.48 to 0.54 through seven years (all p<0.001) (Table 1). The risk of congestive heart failure of the TKA group was 21.1% at three years (HR=0.89, p<0.001) and 40.9% at seven years (HR=0.93, p<0.001). The risk of depression was higher for the TKA group at one year (rate=9.37%, HR=1.28, p<0.0001) and three years (rate=17.1%, HR=1.05, p<0.0093), but there were no long-term significant differences. There was a slightly higher risk for diabetes in the TKA group at one year (rate=24.8%, HR=1.05, p=0.0153) and seven years (rate=45.5%, HR=1.05, p=0.0117), but not at three and five years.
DISCUSSION AND CONCLUSIONWe estimated the costs, mortality and diagnoses of new diseases for OA patients who either did or did not receive a TKA in the U.S. Medicare population. The incremental seven-year cost of TKA was $19,843. This cost does not consider the cost of prescription drugs, which have been reported to be much higher in OA patients who do not undergo TKA. The mortality risk for the TKA patient cohort was approximately half that of the non-TKA group. TKA patients were more likely to be depressed in the first three years after surgery, a finding that suggests the mental health of these patients should be monitored and treated if necessary. This study demonstrates the potential benefit of TKA in reducing mortality, at a relatively minimal long-term incremental cost.
Table 1: Hazard ratios for mortality and new disease diagnoses after TKA. * indicates significance to p<0.05.
Years After Surgery
1 Year5 Years
Rate (%)Hazard RatioRate (%)Hazard RatioRate (%)Hazard RatioRate (%)Hazard Ratio
Congestive Heart Failure10.61.0021.10.89*31.00.91*40.90.93*
Diabetes24.81.05*33.50.9840.11.0045.51.05*
Depression9.371.28*17.11.05*23.41.0029.51.03
Mortality0.990.49*4.430.48*9.620.50*17.10.54*





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