Discharge to inpatient rehabilitation following arthroplasty is a strong predictor of persistent opioid use 90 days after surgery: a prospective, observational study.

Background: Total knee and hip arthroplasty are considered a clinically and cost-effective intervention, however, persistent pain post-surgery can occur, and some continue to take opioid medications long-term. One factor which has infrequently been included in prediction modelling is rehabilitation pathway, in particular, one which includes inpatient rehabilitation. As discharge to inpatient rehabilitation post-arthroplasty is common practice, we aimed to identify whether rehabilitation pathway (discharge to in-patient rehabilitation or not) predicts continued use of opioids at 3 months (90 days) post- total knee arthroplasty (TKA) and total hip arthroplasty (THA) whilst controlling for other covariates.

Methods: The study was nested within a prospective observational study capturing pre-operative, acute care and longer-term data from 1900 osteoarthritis (OA) patients who underwent primary TKA or THA. The larger study involved a part-random, part-convenience sample of 19 high-volume hospitals across Australia. Records with complete pre-and post-operative analgesic (35 days and 90 days) use were identified [1771 records (93% of sample)] and included in logistic regression analyses.

Results: Three hundred and thirteen people (17.8%) reported ongoing opioid use at 90 days post-operatively. In the adjusted model, admission to inpatient rehabilitation after surgery was identified as an independent and significant predictor of opioid use at 90-days. Inpatient rehabilitation was associated with almost twice the odds of persistent opioid use at 90-days compared to discharge directly home (OR = 1.9 (1.4, 2.5), p < .001).

Conclusion: The inpatient rehabilitation pathway is a strong predictor of longer-term opioid use (90 days) post-arthroplasty, accounting for many known and possible confounders of use including sex, age, insurance status, major complications, smoking status and baseline body pain levels.

Trial Registration: The study was nested within a prospective cohort observational study capturing pre-operative, acute-care and longer-term data from patients undergoing primary TKA or THA for osteoarthritis (ClinicalTrials.gov NCT01899443).