Constant Motion

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July 2005

By Danielle Cohen

CPM is an effective way to speed up the rehab process

When the concept of continuous passive motion (CPM) first entered the medical lexicon in 1970, it was considered a radical about-face in a community that long considered immobility the only appropriate treatment for musculoskeletal disorders and injuries. Decades later, CPM is not only an accepted mode of treatment, but many physical therapists view it as a valuable tool after surgeries or injuries.

Its benefits rest in the same original concept: passive motion without resistance on the part of the patient. “That’s the key issue for CPM to be effective. You don’t want the patients to fight it; they just need to relax and let the machine do the work itself,” says Jeff Ehlenberger, MPT, staff physical therapist at Simi Valley Hospital, Simi Valley, Calif, where about 99% of its CPM treatments involve patients who have undergone knee arthroplasty. The balance of Simi Valley’s CPM treatments are for tibial plateau fractures and on shoulders.

On average, CPM is used on one or two patients per week—a number that has held fairly steady over the years, says Ehlenberger. The physical therapists initiate treatment on patients the first day after surgery, with the CPM machine typically set at 0° extension to 40° flexion for that first session. Surgeons’ orders are typically to increase by 5° to 10° per day. “With the surgeons that we’re working with, we’re shooting for 5 to 6 hours of use a day. Currently, the thinking in the field is that it does not have to be a continuous 6 hours. It’s OK to try to break it up over periods of time,” he says. “It’s done on a case-by-case basis. Some patients are more than capable and willing to go through it continuously, and others definitely need that little break in between.”

CPM machines are used on an inpatient basis at Simi Valley. In addition, all total knee patients go home with a machine after being discharged. The total length of treatment is typically about 3 weeks. Simi Valley owns one CPM machine for use in the hospital, and rents others from a vendor as needed.

Across the country, at Spaulding Rehabilitation Hospital, Boston, the physical therapists use only lower limb CPM machines for patients, including those with total knee replacements, tibial fractures, and some mid-shaft femur fractures. “The dynamics of the knee are easier to replicate on a CPM machine versus one for the shoulder or different areas like that because the shoulder joint can move in multiple directions, so it’s hard to truly replicate that process. With the knee, you either flex or extend, whereas, with a shoulder, you could abduct, adduct, externally rotate, internally rotate, extend, or flex,” says Chris Diehl, PT, MHP, program director for Spaulding’s musculoskeletal unit.

Jeff Ehlenberger, MPT

Spaulding owns about 10 CPM machines. The physical therapists use CPM on an inpatient basis on approximately two to four patients each week, including those who have undergone elective joint surgeries, as well as trauma patients. Diehl also says the use of CPM machines has held fairly steady over the years. “In today’s health care environment, as you’re moving quicker and the patients are moving quicker through the door, it’s just another weapon in our arsenal that we can use to help achieve our goals of helping the range of motion. And the range really carries over to their functional status—they’re able to do stairs, and get in and out of a car or a tub, walking, sitting in a chair,” he says.

Like Simi Valley’s, most of Spaulding’s patients are using the CPM machine the day after surgery, usually for 4 to 6 hours each day. “We try to do CPM treatments in the evening so that during the day, the patients are sitting up, walking around, and getting their therapy,” says Cara Brickley, PT, DPT, physical therapy practice leader for the musculoskeletal unit. “Sometimes it’s broken up. Sometimes, depending on how stiff the patient is, we’ll have them go in the CPM for an hour or two before we see them for therapy, and then they’ll go into it for another 2 to 3 hours again in the evening.”

Unlike at Simi Valley, patients at Spaulding are not usually sent home with a CPM machine. The number of days a patient spends using the CPM varies, depending on how quickly they are actively able to bend their knee to about 90°. “As soon as they’re able to do that, then we usually discharge the machine,” Brickley says. “Occasionally, we have people who are very resistant and pain is a huge issue for them, and then we contact their surgeon and they ask us to make sure they go home with the CPM.”

At St Charles Hospital (SCH), Port Jefferson, NY, four or five new patients requiring CPM are admitted each day. “On any given day, we usually have 20 to 30 patients who are using a CPM for their knee following total knee replacement,” says Michael Scicchitano, PT, chief physical therapist. “The majority of patients we use the CPM for have had total knee replacements. Other patients who require a knee CPM have undergone ACL reconstruction or joint manipulations. We do occasionally use CPMs for the elbow, the shoulder, and even the hand and fingers.”

On average, patients use CPM for a minimum of 4 hours per day, usually two 2-hour sessions. The entire length of treatment varies, depending on the patient’s needs; some continue its use after discharge. “The use of CPM at St Charles has held steady in that none of the physicians or groups of surgeons have really changed their practice in ordering the modality. However, our use on a daily basis has gone up considerably over the last few years simply because SCH is continually increasing the volume of patients who require CPM,” Scicchitano says.

The use of CPM at SCH following total knee replacement has changed somewhat over the years, he says, in that almost all of the surgeons who use CPM in the acute postoperative recovery phase of rehabilitation at the hospital order it to be initiated in the recovery room within an hour or two of the surgery.

ANATOMY OF A TECHNOLOGY
What makes CPM an effective treatment is the evolutionary improvements that the technology has undergone during the last 35 years. Early versions of CPM devices were bulky and required manual adjustment. Newer versions help control the range of motion and force applied, as well as detect resistance on the part of patients. The advancements have come through the use of microprocessors, which control the parameters for the machines’ settings.

Chris Diehl, PT, MHP

While CPM does not replace the benefits of more active or hands-on therapies, the therapists say the machines can accomplish what the human touch simply cannot.

“It gives you a more controlled, directed approach to gradually increasing the range of motion,” Ehlenberger says. “As physical therapists, we’re skilled and trained in providing increasing ranges of motion, but there’s something lacking in the human touch that you get in the machine, which is that precise ability to monitor your progress. A lot of the doctors don’t want you to increase the range of motion much more than 5° to 10° a day.”

Among CPM’s benefits are the alleviation of stiffness and pain, a decrease in the potential for the development of scar tissue and deep venous thrombosis, and an increase in flexion—all of which can contribute to an overall shorter rehabilitation and faster recovery time. “The machine helps to really loosen up the knee, get [the patient] moving, and get everything nice and loose so that when we take them down to therapy, we’re not fighting the stiffness,” Brickley says.

Another benefit of CPM is that patients seem to improve faster, according to SCH’s Scicchitano. “[This includes] a quicker increase in range of motion; improved compliance with active therapeutic protocols following surgery; the quicker range of motion achievement does carry over to quicker functional gains after total knee replacement surgery; and possibly a psychological benefit in that patients are more comfortable in attempting to bend their ‘new’ knee on their own after seeing it bend on the CPM,” he says.

Though the machine is doing most of the work, there are still pain issues that have to be addressed by therapists. “On the pain management side, [the benefits] are kind of split,” Ehlenberger says. “Some of my patients love the machine. They say, ‘My knee feels better. I can move it better. I have less pain.’ And others frankly deride the whole process because it’s just always painful.”

Part of the problem, admits Ehlenberger, has to do with the fact that since patients are being treated almost immediately after surgery, they are in a great deal of pain. But, he says, therapists have to work on getting patients past their initial pain. “Patients are very fearful in the very beginning. They just had surgery and all they know is that they hurt, they can’t move their knee, and now you want to put them in this strange-looking robotic machine. A lot of that is just countered with ongoing patient education,” he says.

TIP-TOP SHAPE

Cara Brickley, PT, DPT

While the therapists laud the benefits of CPM, the machines themselves do pose some challenges and limitations. Some of these limitations are due to the fact that the machine has to be used for a long period of time to be effective. “The limitations are really when you get a poorly working machine. CPM machines have a very high cycle rate; they get used a lot, so one of the challenges is keeping them in good condition,” Ehlenberger says. “The other challenge is patient compliance. Some patients just don’t want to be in the machine.”

Even with the limitations, Ehlenberger does not discount CPM as a therapeutic modality. “I don’t see any real negative points to actually using the machine. I think even the patients who complain about the machine actually end up doing better and heal quicker,” he says.

Another challenge is the one-size-fits-all aspect of the machine. “We are constantly looking at the machine, trying to readjust it to make sure that it is lined up correctly,” Brickley says. “It’s not like there’s a small, medium, and large. You get one machine. You can adjust it, but its adjustment is limited. If you don’t get it lined up appropriately, then patients will try to cheat. They’ll position themselves in the bed so that their knee isn’t really bending as much as the machine says that it does.”

Compliance may be the greatest challenge facing clinicians, Scicchitano says, adding that physical therapists can help patients become actively involved in this passive modality by providing “proper instruction and encouraging them to increase their range of motion on the machine within prescribed parameters more independently as they can tolerate it.”

While studies have shown that, at 1 year out, range of motion and function are the same among patients who have had CPM and those who have not, the physical therapists say their firsthand observations are enough to convince them of its usefulness. “In the early stages, in the acute process, we do see a statistically significant increase in flexion much sooner [with the use of CPM]. It’s typically only about 4° to 5° of change, but when you have a patient who needs to go up and down a set of stairs—there’s the magic number of 90° of knee flexion, where we all feel that we can at least get by functionally—they can do it,” Ehlenberger says. “The difference in those 4° to 5° is significant once the patient actually tries to functionally use the limb in the home or out in the community.”

Danielle Cohen is a staff writer for Rehab Management.

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