The incremental cost effectiveness of in-patient versus out-patient rehabilitation after total hip arthroplasty - results of a pilot investigation.

PURPOSE Total hip arthroplasty (THA) is an established and cost effective procedure in the treatment of severe arthritis of the hip. However, bearing recent demographic changes in mind, the increasing demand for total hip arthroplasty during the next decades catalyzes health economic re-consideration of the overall health care process of initial surgery and subsequent rehabilitation. One point for discussion is due to postoperative rehabilitation, since direct costs of the latter crucially depend on whether in-patient (indoor) or out-patient (outdoor) rehabilitation is recommended. Whereas out-patient rehabilitation is obviously more cost efficient from a health insurer's perspective than its indoor alternative, it is open for discussion, whether the alternatives' clinical benefit profiles from a patient's perspective are of comparable order. Therefore this pilot investigation was implemented to assess the clinical benefit and cost effectiveness of in-patient versus out-patient rehabilitation after THA. METHODS A total of 28 patients (16 females) were enrolled in this retrospective matched pairs cohort study. All patients underwent THA in 2006 and were then assigned to either in-patient (n = 14) or out-patient (n = 14) postoperative rehabilitation at cooperating departments. The in-patient and out-patient samples were recruited from an epidemiological register trial on THA outcome, and matched 1:1 according to gender, age at surgery, working and family state. Preoperative assessment of (algo-) function as well as clinical outcome six months after surgery were based on the WOMAC questionnaire. Primary clinical endpoint of this investigation was the intraindividual increase in the WOMAC score (%), which was transformed into a utility scale ranging from 0 - 100% (optimum self-rating) and then into the number of gained quality adjusted life years (QALY). Primary economic endpoint were the total direct costs (Euro) for the overall treatment including surgery and rehabilitation from the health care insurer's perspective; costs for surgery and stationary care were calculated by means of German DRG rates, costs for postoperative rehabilitation by means of daily rates for indoor and outdoor care and the individual duration of rehabilitation. Based on these primary endpoints, the marginal cost effectiveness ratio (Euro/QALY) was estimated for the indoor and the outdoor based health care process, respectively. RESULTS The matched pairs' median age difference was 2 years, their median difference in body mass index 0.8 kg/m superset2. Outdoor patients reported a median WOMAC score of 38% before and 87% after surgery, indoor patients of 41% and 88%. Matched pair evaluation revealed a median difference of 5% (interquartile range -18% - 26%) between the matched pair partners' respective WOMAC increases indicating gradual superiority of in-patient rehabilitation (sign test p = 0.719). This WOMAC difference corresponded to a median clinical benefit difference of 0.77 QALYs (interquartile range -2.13 - 3.18 QALYs) between indoor and outdoor patients. The total direct costs for surgery, postoperative care and rehabilitation were calculated 8706 Euro in median for out-patient and 9126 Euro in median for in-patient rehabilitation, their respective median matched pair difference was 420 Euro (198 - 475 Euro, p = 0.013). In summary, the marginal cost effectiveness ratios showed a matched pair difference of -841 Euro / QALY (sign test p = 0.791). The latter demonstrated - not significantly - smaller marginal costs of indoor rehabilitation. CONCLUSION In this matched pilot investigation the overall health care process involving in-patient rehabilitation after total hip arthroplasty did not demonstrate a significantly superior cost effectiveness when compared to its out-patient alternative from a health care insurer's perspective. This observation is complemented by a rather small difference in clinical benefit. However, prospective investigations, which should randomize the rehabilitation alternatives onto appropriate patients, are necessary to confirm the above pilot results.