Effectiveness of prolonged use of continuous passive motion (CPM) as an adjunct to physiotherapy following total knee arthroplasty: design of a randomised controlled trial [ISRCTN85759656].

Background: Adequate and intensive rehabilitation is an important requirement for successful Total Knee Arthroplasty. The primary focus of early rehabilitation is ambulation of patients and regaining range of motion in the knee. Although research suggests that Continuous Passive Motion should be implemented in the first rehabilitation phase following surgery, there is substantial debate about the duration of each session and the total period of CPM application and. A Cochrane review on this topic concluded that short-term use of CPM leads to greater short-term range of motion. It also suggested, however, that future research should concentrate on the treatment period during which CPM should be administered.

Methods: In a randomised controlled trial we intend to investigate the efficacy of prolonged use of a continuous passive motion (CPM) device in the home situation as an adjunct to standardised physical therapy. The experimental treatment is compared to standardised physical therapy, in patients with osteoarthritis of the knee undergoing Total Knee Arthroplasty (TKA). Efficacy will be assessed in terms of faster improvements in range of motion and functional recovery. Seventy patients with knee osteoarthritis undergoing TKA and experiencing early postoperative flexion impairment (less than 80 degrees of knee flexion at the time of discharge) will be randomised over two treatment groups, a usual care group and an experimental group. The experimental group will receive CPM + physiotherapy for 17 consecutive days after surgery, whereas the usual care group will receive the same treatment during the in-hospital phase (i.e. about four days), followed by physical therapy alone (usual care) in the first two weeks after hospital discharge. From 18 days to three months after discharge, both groups will receive standardised PT. The primary focus of rehabilitation will be functional recovery (e.g. ambulation) and regaining range of motion (ROM) in the knee.

Discussion: Because restricted knee ROM affects functional activities, knee ROM and knee function are regarded as the primary indicators of successful TKA. Potential effects of the intervention under study include rapid return of knee flexion accompanied by earlier return to functional activities of daily life. If patients benefit significantly from prolonged CPM use, this treatment should be added to the standard PT treatment at home. We expect the additional home CPM programme to be more effective than the usual physiotherapy programme, resulting in a difference in ROM of at least 5 degrees , 17 days after surgery. This clinically important difference, with a possible flexion ROM of about 100 degrees , is expected to lead to better functioning in activities of daily life, like walking, and earlier ability to cycle. These advantages should result in earlier and increasing independence.