Continuous Passive Motion Device

Definition

Continuous passive motion (CPM) is a modality of postoperative treatment intended to assist recovery following joint surgery or injuries of upper or lower extremities. It is most commonly used in the treatment of knee or shoulder injuries, although some CPM devices have been designed to treat jaw disorders involving the temporomandibular joint. CPM equipment covers a range of mechanical devices designed to move the patient's joint or extremity without the use of the patient's muscles through a prescribed range of motion over extended periods of time. These devices were first introduced in the 1980s by Dr. Robert Salter, an orthopaedic surgeon.

Purpose

CPM is used to reduce the adverse effects of trauma or immobilization following surgery. In physiological terms, synovial fluid is diffused without hindering tissue repair; the joint receives nutrition, the flow of venous blood is increased, and the cartilage is prevented from deteriorating. From a clinical perspective, joint swelling (edema ) is decreased, range of motion (ROM) is maintained, tissue repair is accelerated, and the patient experiences less pain, which in turn allows for lower doses of pain medication.

CPM devices are used as alternatives and adjuncts to conventional physical therapy following surgery, injury, or stroke. CPM devices may also be used in bedridden surgical patients to reduce the incidence of deep vein thrombosis, to treat abnormal muscle shortening that occurs due to prolonged immobilization, and in patients with burns or joint sepsis.

Description

CPM devices are used in both inpatient and outpatient settings; many are designed to allow home use as well. Typical CPM devices consist of a limb support resembling a splint or brace, a motor drive, and a control unit. CPM devices for the lower limb are used primarily after total knee replacement, joint arthroscopy, cartilage transplantation, and ligament repair to provide flexion and extension of the joint. Configurations for exercising the hip, ankle, or toes are also available. Larger lower-limb CPM devices are typically designed to rest directly on the patient's bed; some are designed with the limb support suspended from an overhead traction frame. Upper-limb CPM devices are available mounted on stands that can be wheeled to the patient's bedside, in tabletop configurations, and as portable battery-powered units. They are frequently used in the treatment of rotator cuff injuries.

The newest CPM devices are compact and light in weight, making them not only portable but wearable. In 2005 a team of researchers at Northeastern University reported on a CPM device for the elbow that is easily transportable and can be used almost anywhere.

The motor drive of a CPM device is connected by a shaft to the limb support. The control unit contains adjustments for speed, motor reversal, and such range of motion parameters as degree of rotation, flexion, or extension. Some units are computerized and have remote control capabilities. Other units pause the continuous motion to allow for some active contraction by the patient or for the application of neuromuscular electrical stimulation.

Operation

The limb requiring CPM is strapped into the device's support. The range of motion parameters, speed, cycling time, and duration are then set. Most CPM devices have mechanical safety releases, resistance sensors, and/or automatic shut-offs for safety purposes. The most advanced CPM devices use microprocessors and load cells to measure resistance and automatically adjust parameters. Hospital patients may have 24-hour CPM operation. Patients using CPM at home may use the devices from four to six hours daily in hour-long sessions. CPM treatment is usually given for five or six weeks after surgery.

Patients on CPM devices should be monitored for problems with limb positioning and interference with device operation. For instance, bedsheets may become tangled in the device, or the patient's limb may become trapped, resulting in injury. Patients with urinary incontinence should be monitored carefully during CPM, because body fluids are an electrical hazard. All patients on CPM devices should be monitored for unnecessary discomfort, pain, and chafing. Most manufacturers offer accessories or configurations to adjust for variations in patient limb size.

Newer models of CPM devices are equipped with buttons that the patient can push when the pain threshold is reached. The machine then continues to move the affected limb, but at a lower angle of flexion. Other CPM devices have controls with a lockout feature to prevent the settings from being altered.

Maintenance

CPM devices are low-maintenance equipment since they are designed for continuous use. They do, however, require frequent checks for wear of moving parts and malfunctioning. These devices are not inexpensive; prices in the early 2000s range from $3,000 for a knee CPM to $7,000 for a device to treat shoulder injuries. Most insurance companies, however, will pay for the cost of renting a CPM device.

Health care team roles

The use of a CPM device is most often prescribed by a physician, orthopaedic surgeon, or specialist in sports medicine, and overseen by nursing, physical therapy, or rehabilitation staff. The physician prescribes the speed, duration of movement, range of motion, and rate of increase of motion for the patient's use of the CPM.

Training

Manufacturers of CPM devices provide training for clinical staff. In addition, detailed user manuals are provided for reference during operation and maintenance. Patients using CPM devices at home should be given instructions regarding proper use of the device.

KEY TERMS

Edema— An abnormal buildup of fluid in the tissues or joint capsules of the body, causing swelling of the involved area. Edema is a common cause of stiffness in the joints following injury or surgery.

Range of motion (ROM)— The extent to which a joint can be moved.

Sepsis— A local or generalized invasion of the body by disease microorganisms or their toxins.

Synovial fluid— A clear, viscous fluid secreted by membranes surrounding the joints. Synovial fluid helps to lubricate the joints.

Thrombosis— Coagulation or clotting of the blood inside a vein.

Resources

BOOKS

Pierson, F. Principles and Techniques of Patient Care, 2nd ed. Philadelphia: W. B. Saunders Co., 1999.

"Rehabilitation Treatment." The Merck Manual of Diagnosis and Therapy, Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2005.

PERIODICALS

Ferretti, M., A. Srinivasan, J. Deschner, et al. "Anti-Inflammatory Effects of Continuous Passive Motion on Meniscal Fibrocartilage." Journal of Orthopaedic Research 23 (September 2005): 1165-1171.

Fuchs, S., T. Heyse, G. Rudofsky, et al. "Continuous Passive Motion in the Prevention of Deep-Vein Thrombosis: A Randomised Comparison in Trauma Patients." Journal of Bone and Joint Surgery, British volume, 87 (August 2005): 1117-1122.

Lynch, D., M. Ferraro, J. Krol, et al. "Continuous Passive Motion Improves Shoulder Joint Integrity Following Stroke." Clinical Rehabilitation 19 (September 2005): 594-599.

Mavroidis, C., J. Nikitczuk, B. Weinberg, et al. "Smart Portable Rehabilitation Devices." Journal of Neuroengineering and Rehabilitation 12 (July 2005): 2-18.

Salter, R. B. "Continuous Passive Motion: From Origination to Research to Clinical Applications." Journal of Rheumatology 31 (November 2004): 2251-2264.

ORGANIZATIONS

American Academy of Orthopaedic Surgeons. 6300 North River Road, Rosemont, IL 60018-4262. (847) 823-7186. 〈http://www.aaos.org〉.

American Academy of Physical Medicine and Rehabilitation. One IBM Plaza, Suite 2500, Chicago, IL 60611-3604. (313) 464-9700. 〈http://www.aapmr.org〉.

American College of Sports Medicine (ACSM). 401 West Michigan Street, Indianapolis, IN 46202-3233. (317) 637-9200. Fax: (317) 634-7817. 〈http://www.acsm.org〉.

American Physical Therapy Association. 1111 North Fairfax Street, Alexandria, VA 22314-1488. (703) 684-2782. 〈http://www.apta.org〉.