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A controlled evaluation of continuous passive motion in patients undergoing total knee arthroplasty.

OBJECTIVE
To evaluate the efficacy of continuous passive motion (CPM) in the postoperative management of patients undergoing total knee arthroplasty.


DESIGN
A randomized controlled single-blind trial of CPM plus standardized rehabilitation vs standard rehabilitation alone.


SETTING
A referral hospital for arthritis and musculoskeletal care.


PATIENTS
Consecutive patients with end-stage osteoarthritis or rheumatoid arthritis undergoing primary total knee arthroplasty who had at least 90 degrees of passive knee flexion. One hundred fifty-four patients were eligible and 102 patients agreed to participate and were randomized. Ninety-three patients completed the study protocol.


INTERVENTION
Continuous passive motion machines programmed for rate and specified arc of motion within 24 hours of surgery with range increased daily as tolerated with standardized rehabilitation program compared with standardized rehabilitation program alone.


MAIN OUTCOME MEASURES
Primary outcomes were pain, active and passive knee range of motion, swelling (or circumference), quadriceps strength at postoperative day 7, as well as complications, length of stay, and active and passive range of motion and function at 6 weeks.


RESULTS
Use of CPM increased active flexion and decreased swelling and the need for manipulations but did not significantly affect pain, active and passive extension, quadriceps strength, or length of hospital stay. At 6 weeks there were no differences between the two groups in either range of motion or function. In this series, use of CPM resulted in a net savings of $6764 over conventional rehabilitation in achieving these results.


CONCLUSION
For the average patient undergoing total knee arthroplasty, CPM is more effective in improving range of motion, decreasing swelling, and reducing the need for manipulation than is conventional therapy and lowers cost.