Medicare HMO disenrollment and selective use of medical care: Osteoarthritis-related joint replacement

Objective: Recent Medicare health maintenance organization (HMO) disenrolle es use a high level of medical services. This study examined admissions for total hip arthroplasty (THA) and osteoarthritis-related knee replacements (OKR) among Medicare HMO disenrollees and continuously enrolled fee-for-ser vice (FFS) beneficiaries to determine whether Medicare beneficiaries are re turning to the FFS system to receive quality-of-life enhancing elective car e. Study Design: Retrospective analysis of Medicare inpatient claims for elder ly Medicare beneficiaries residing in South Florida between 1990 and 1993. Methods: Inpatient admission rates for THA, OKR, and for 2 acute conditions -total hip replacements related to fracture of the hip (HRF) and acute myoc ardial infarction (AMI)-were estimated for Medicare HMO disenrollees over t he 3-month period immediately following their disenrollment, These rates we re compared with standardized rates for Medicare FFS enrollees. Results: The annualized adjusted rates of both THA and OKR were 3.5 to 4 ti mes higher among Medicare HMO disenrollees than among FFS beneficiaries (P less than or equal to .0001 for both procedures); substantially smaller dif ferences were noted for HRF (P less than or equal to .05), and no differenc e was present for AMI. HMO disenrollees and FFS enrollees did not differ in their levels of comorbidity at the time of admission. Conclusions: These data provide indirect evidence that Medicare HMOs in Sou th Florida are rationing THA and OKR and that beneficiaries respond by retu rning to the FFS system to seek care. This apparent rationing has important implications regarding for the management of serious, but nonemergent, med ical conditions within the evolving Medicare system.