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July 2004


Joint Work

By Paul F. Lachiewicz, MD

Continuous passive motion (CPM) machines were introduced for the postoperative care of total knee arthroplasty (TKA) patients in the early 1980s. Coutts et al reported a study comparing 12 patients who used a CPM machine for 20 hours per day after TKA to 12 patients who were immobilized for 3 to 4 days after TKA.1 The range of motion on postoperative day 10 was significantly better and the use of pain medication was less in the CPM group.

Following this initial report, the use of CPM after TKA became widespread. CPM machines were later introduced for the shoulder, elbow, and finger joints as an adjunct after surgical procedures or manipulation for stiffness. The author has no experience with these devices, and the remainder of this article will discuss the use of CPM after total knee arthroplasty.

CPM CONTROVERSY

•

Decreased rate of manipulation

•

Greater range of motion

•

Less pain and analgesic use

•

Less thromboembolism

•

Shorter hospital stay

•

Decreased costs

Table 1. Possible benefits of CPM.
The utility of CPM after primary TKA remains controversial. There are surgeons who require it for most patients2 and others who never use it.3 The reported benefits of CPM are listed in Table 1. The most important benefit is a decrease in or elimination of the need for later manipulation of the knee joint under anesthesia for poor range of motion. The reported complications of CPM are listed in Table 2. The opponents of the use of CPM have reported there is no benefit in terms of ultimate range of motion of the knee, rate of thromboembolism, or reduction in the length of hospital stay. There are many problems and confounding variables in the published reports of CPM after primary TKA.2 These include the amount of time the CPM machine was used, the surgeon’s indication for manipulation, and hospital accounting procedures.

•

Quadriceps weakness

•

Wound complication

•

Increased joint bleeding

•

Increased costs

Table 2. Possible complications of CPM.
The author has previously reviewed the literature to analyze objectively the benefits of CPM after primary TKA.2 The strongest data to support its continued use are a lower rate of manipulation for poor range of motion after TKA when CPM is used. In one prospective randomized study, the rate of manipulation was 18% without CPM and 0% with CPM.4 However, another study reported that the rate of manipulation was related to the length of hospital stay.5 This was a retrospective review of three cohorts of primary TKA patients, in which CPM and physical therapy began within the first 24 hours postoperatively. In the first group, the mean length of hospital stay was 6.4 days and the rate of manipulation was 6%. In the second group, the mean hospital stay was 5.4 days and the rate of manipulation increased to 11.3%. The third group had a hospital stay of only 4.4 days and the rate of manipulation was 12%. It is unclear how many of these patients were discharged to a rehabilitation center or how much outpatient therapy was performed.

STANDARD PRACTICE
At the present time, the author’s hospital has a standardized 4-day, inpatient clinical pathway for TKA patients. CPM machine use is started on postoperative day one, for 60 minutes three times per day. The nursing staff places the patient knee in the CPM machine with the pneumatic compression device remaining on the patient’s calf (Figure 1). A physical therapist sees the patient twice a day for exercises. After routine venous duplex ultrasonography on day four, the patients are discharged to home with three times per week physical therapy visits or transferred to a rehabilitation facility (usually at the same institution).


Figure 1. Typical patient in CPM with mechanical calf compression device.

Because of current Medicare and insurance regulations, the patients who are transferred to a rehabilitation facility are usually older (75 years and greater), have had bilateral TKA, or have other comorbidities, such as a neurologic disorder or polyarticular rheumatoid arthritis. If the patient is transferred to our on-site rehabilitation faculty, the CPM machine and pneumatic compression device travel with the patient. No patient is discharged home with a CPM machine.

The author does not start the CPM machine in the recovery room because of the risk of increased bleeding into the joint. Wound complications are not increased with the use of the CPM machine provided the surgeon has performed a good wound closure. The author begins range of motion from 0 to 35 degrees, and the nursing staff increases the flexion by 10 degrees once or twice per day during the next 2 to 3 postoperative days, or until 90 degrees flexion is achieved. The same protocol is continued at our rehabilitation facility (1 hour CPM, three times per day) to permit other activities (eg, occupational, physical, and recreational therapy). The skin staples are removed between 14 and 21 days postoperatively. If the patient has poor flexion (less than 70 degrees) or the physical therapist reports little improvement in flexion over several days, a manipulation under anesthesia is scheduled. It is important to remember that manipulation cannot be performed to reduce a flexion contracture as this will likely cause a supracondylar fracture. In addition, the postoperative range of motion achieved after TKA is strongly influenced by the amount of preoperative motion. The author will accept 80 degrees to 90 degrees of flexion if the patient had less than 90 degrees of flexion preoperatively.

The data are unclear whether the prevalence of thromboembolism and the use of narcotic analgesics are decreased with the use of CPM. The author recommends that pneumatic calf compression and aspirin continue at the rehabilitation facility for thromboembolism prophylaxis. However, other surgeons and many physiatrists use pharmacologic prophylaxis with warfarin or low molecular weight heparin while TKA patients remain at the rehabilitation facility. In patients who are anticoagulated, the nursing staff and therapists should be aware of the risk of bleeding into the TKA with vigorous therapy. Concerning analgesic use, one study showed a significant decrease with CPM,6 but another study reported that the mean analgesic requirement was lower in patients without CPM.7

The author’s CPM protocol and results after primary TKA have been previously reported.2 With one brand of posterior stabilized prosthesis, the manipulation rate was 4.8%. The threshold for manipulation was less than 70 degrees flexion at the time of staple removal 2 to 3 weeks postoperatively. From mid 1998 to December 2003, the author used another brand of posterior stabilized knee prosthesis in 260 consecutive patients, and only five patients have required a manipulation (1.9%). The surgical technique and use of CPM have been consistent.

In summary, the use of CPM after primary TKA remains controversial. The author continues to recommend it during the hospital and rehabilitation facility stay to prevent a need for later manipulation.

Paul F. Lachiewicz, MD, is professor of orthopaedics at the University of North Carolina at Chapel Hill School of Medicine and attending orthopaedic surgeon at UNC Hospitals.

REFERENCES
  1. Coutts RD, Kaita J, Barr R, et al. The role of continuous passive motion in the postoperative rehabilitation of the total knee patient. Orthop Trans. 1982;6:277-278.
  2. Lachiewicz PF. The role of continuous passive motion after total knee arthroplasty. Clin Orthop. 2000;380:144-150.
  3. Kumar PJ, McPherson EJ, Dorr LD, et al. Rehabilitation after total knee arthroplasty. Clin Orthop. 1996;331:93-101.
  4. McInnes J, Larson MG, Daltroy LH, et al. A controlled evaluation of continuous passive motion in patients undergoing total knee arthroplasty. JAMA. 1992;268: 1423-1428.
  5. Mauerhan DR, Mokris JG, Ly A, Kiebzak GM. Relationship between length of stay and manipulation rate after total knee arthroplasty. J Arthroplasty. 1998;13:896-90.
  6. Colwell CW, Morris BA. The influence of continuous passive motion on the results of total knee arthroplasty. Clin Orthop. 1992;276:225-228.
  7. Pope RO, Corcoran S, McCaul K, Howie DW. Continuous passive motion after primary total knee arthroplasty. Does it offer any benefits? J Bone Joint Surg. 1997;79B:914-917.

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