Effects of perioperative analgesic technique on the surgical outcome and duration of rehabilitation after major knee surgery

Background: Continuous passive motion after major knee surgery optimizes th e functional prognosis but causes severe pain. The authors tested the hypot hesis that postoperative analgesic techniques influence surgical outcome an d the duration of convalescence. Methods: Before standardized general anesthesia, 56 adult scheduled for maj or knee surgery were randomly assigned to one of three groups, each to rece ive a different postoperative analgesic technique for 72 h: continuous epid ural infusion, continuous femoral block, or intravenous patient-controlled morphine (dose, 1 mg; lockout interval, 7 min; maximum dose, 30 mg/4 h). Th e first two techniques were performed using a solution of 1% lidocaine, 0.0 3 mg/ml morphine, and 2 mu g/ml clonidine administered at 0.1 mi kg-l h-l. Pain was assessed at rest and during continuous passive motion using a visu al analog scale. The early postoperative maximal amplitude of knee flexion was measured during continuous passive motion at 24 h and 48 h and compared with the target levels prescribed by the surgeon. To evaluate functional o utcome, the maximal amplitudes were measured again on postoperative day 5, at hospital discharge (day 7), and at 1- and 3-month follow-up examinations . When the patients left the surgical ward, they were admitted to a rehabil itation center, where their length of stay depended on prospectively determ ined discharge criteria. Results: The continuous epidural infusion and continuous femoral block grou ps showed significantly lower visual analog scale scores at rest and during continuous passive motion compared with the patient-controlled morphine gr oup. The early postoperative knee mobilization levels in both continuous ep idural infusion and continuous femoral block groups were significantly clos er to the target levels prescribed by the surgeon than in the patient-contr olled morphine group. On postoperative day 7, these values were 90 degrees (60-100 degrees) (median and 25th-75th percentiles) in the continuous epidu ral infusion group, 90 degrees (60-100 degrees) in the continuous femoral b lock group, and 80 degrees (60-100 degrees) in the patient-controlled morph ine group (P < 0.05). The durations of stay in the rehabilitation center we re significantly shorter: 37 days (range, 30-45 days) in the continuous epi dural infusion group, 40 days (range, 31-60 days) in the continuous femoral block group, and 50 days (range, 30-80 days) in the patient-controlled mor phine group (P < 0.05). Side effects were encountered more frequently in th e continuous epidural infusion group. Conclusion: Regional analgesic techniques improve early rehabilitation afte r major knee surgery by effectively controlling pain during continuous pass ive motion, thereby hastening convalescence.