A randomized trial of controlled-release oxycodone during inpatient rehabilitation following unilateral total knee arthroplasty

Background: Reliance on "as-needed" analgesia following total knee arthroplasty may lead to inadequate control of pain and delayed recovery of function. Preemptive use of controlled-release opioids may improve pain control, accelerate recovery, and reduce the need for inpatient rehabilitative services. This study was designed to determine whether controlled-release opioids enhance post-arthroplasty pain control and facilitate functional recovery during rehabilitation. Methods: Fifty-nine patients admitted for inpatient rehabilitation following unilateral total knee arthroplasty were randomized to receive OxyContin (controlled-release oxycodone) (twenty-nine patients) or a placebo (thirty patients) every twelve hours. Both groups could receive on-request, immediate-release oxycodone (5 mg every four hours). The dose of study medication was increased on the basis of the frequency of requests for immediate-release oxycodone. Measures of interest included pain ratings as determined with a visual-analog scale, changes in the range of motion of the knee and quadriceps strength, and improvements in selected Functional Independence Measure scores during the first eight physical therapy sessions. The duration of the hospital stay for rehabilitation also was compared between the two groups. Results: Baseline demographic, clinical, and functional characteristics were similar between the OxyContin and placebo groups. Compared with the placebo group, the patients who received OxyContin reported significantly less pain as well as significantly greater range of motion of the knee (passive motion, p = 0.036; active motion, p < 0.001) and quadriceps strength (p = 0.001) by the eighth physical therapy session. The patients who received OxyContin also were discharged from the rehabilitation hospital at an average of 2.3 days earlier than the patients in the placebo group (p = 0.013). Conclusions: Preemptive use of controlled-release oxycodone during rehabilitation following total knee arthroplasty leads to improved pain control, more rapid functional recovery, and a reduced need for inpatient rehabilitative services.