Association between muscle atrophy/weakness and health care costs and utilization among patients receiving total knee replacement surgery: a retrospective cohort study

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Open Access Full Text Article Association between muscle atrophy/weakness and health care costs and utilization among patients receiving total knee replacement surgery: a retrospective cohort study This article was published in the following Dove Press journal: Journal of Pain Research 31 July 2013 Number of times this article has been viewed Shih-Yin Chen 1 Ning Wu 1 Yuan-Chi Lee 1 Yang Zhao 2 Health Economics and Epidemiology, Evidera, Lexington, Massachusetts, USA; 2Health Economics and Outcomes Research, Novartis Pharmaceuticals Corporation, East Hanover, New Jersey, USA 1 Purpose: The aim of the study reported here was to examine health care resource utilization, costs, and risk of rehospitalization for total knee replacement (TKR) patients with and without muscle atrophy/weakness (MAW). Patients and methods: Individuals aged 50–64 years with commercial insurance or 65+ years with Medicare Supplemental Insurance (Medicare) who had a hospitalization for TKR between January 1, 2006 and September 30, 2009 were identified from a large US claims database. First hospitalization for TKR was defined as the index stay. All patients were classified into three cohorts according to when MAW was diagnosed relative to TKR: pre-MAW, post-MAW, and no MAW. The association between MAW and health care costs over the 12-month post-index period and the probability of rehospitalization were assessed via multivariate regressions. Results: The study sample included 53,696 Medicare and 46,058 commercial insurance TKR patients. Controlling for cross-cohort differences, both the pre- and post-MAW cohorts had significantly higher total health care costs (Medicare US$4,201 and US$9,404 higher, commercial insurance US$2,737 and US$6,640 higher, respectively) than the no MAW cohort (all P , 0.05). The post-MAW cohort in both populations was also more likely to have any all-cause or replacement-related rehospitalization compared with the no MAW cohort. Conclusion: Among US patients undergoing TKR, those with MAW had higher health care utilization and costs than patients without MAW. Keywords: rehospitalization, resource utilization, Medicare, health insurance, USA Introduction Correspondence: Yang Zhao 1 Health Plaza, East Hanover, NJ 07936, USA Tel +1 862 778 3662 Fax +1 973 781 2390 Email submit your manuscript | www.dovepress.com Dovepress http://dx.doi.org/10.2147/JPR.S48235 Powered by TCPDF (www.tcpdf.org) Total knee replacement (TKR) is one of the most common orthopedic surgeries performed in the USA.1 Most commonly, TKRs are performed as a result of the pain and decreased quality of life associated with osteoarthritis.2 As the US population ages and becomes more obese,3 it is expected that osteoarthritis rates, hence TKR rates, will continue to rise. TKRs have increased from 31.2 per 100,000 person-years in 1971–1975 to 220.9 in 2005–2008.4 The demand for primary TKR is projected to grow by sixfold to 3.48 million in 2030.5 The high and rising incidence and prevalence of the TKR procedure in the USA indicates a large societal burden, especially for the Medicare program, since it has been estimated that 75% of all TKR cases in the USA are performed on Medicare beneficiaries.6 Knee replacements represented the most rapidly increasing hospital inpatient costs for all payers from 2002 to 2004, with a mean cost of US$13,200 per admission and an aggregate cost of US$6.3 billion during 2004.7 Journal of Pain Research 2013:6 595–603 © 2013 Chen et al, publisher and licensee Dove Medical Press Ltd. This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited. 595 Dovepress Journal of Pain Research downloaded from https://www.dovepress.com/ by 5.196.129.157 on 12-Jul-2018 For personal use only. Chen et al While improvement of functioning is a goal of TKR,2 quadriceps muscle atrophy/weakness (MAW) is a common problem for TKR patients.8–13 MAW among these patients is typically the result of either muscle atrophy or the failure of voluntary muscle activation due to neurological impairment,8,9,11,13 and it has been shown to be associated with poorer functioning up to 2 years after the TKR.14 Previous studies have indicated that MAW exists among some TKR patients even before the TKR surgery8,9 and that patients are likely to have profound quadriceps MAW from 1 month8 to 12 months10 after the TKR procedure. However, as far as we are aware, no previous research has attempted to quantify the differences in health care resource use, costs, or other medical outcomes between TKR patients with and without MAW. The retrospective, naturalistic study described here was designed to begin to quantify the burden of MAW among TKR patients. To this end, the main study objective was to examine differences of direct health care related costs and utilization in TKR patients between those with and without a diagnosis of MAW. The timing of the first MAW diagnosis recorded before or after the TKR surgery was also explored to assess its association with patient demographic, clinical, and economic characteristics. Methods This study utilized data between January 1, 2005 through September 30, 2010 from the Thomson Reuters MarketScan® Commercial Claims and Encounters (hereafter referred to as “Commercial”) Database and the Medicare Supplemental Insurance (Medicare) Database. The databases include eligibility records and administrative claims from 33 million enrollees, 3 million of which are Medicare eligible, covered by approximately 100 self-insured payers. The databases contain information on enrollment status, health plan type, and demographic characteristics such as age, sex, and region of residence. Information captured on pharmacy claims includes National Drug Code, dispense date, quantity, days supplied, and plan- and patient-paid amounts. On the medical service claims, details of health service encounters such as date and place of service, provider type, plan- and patientpaid amounts, and International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) diagnosis and procedure codes were recorded across all settings. These administrative claims databases are fully compliant with the Health Insurance Portability and Accountability Act of 1996 privacy requirements and can be used to track health care utilization and costs longitudinally using encrypted identifiers. 596 Powered by TCPDF (www.tcpdf.org) submit your manuscript | www.dovepress.com Dovepress To be included in the study, a patient was required to have an inpatient stay with an associated procedure code of TKR (ICD-9-CM procedure code of 81.54 or Current Procedural Terminology code 27447) between January 1, 2006 and September 30 (...truncated)