Continuous Passive Motion Device
Continuous passive motion (CPM) is a modality of postoperative treatment intended to assist recovery following joint surgery or injuries of upper or lower extremities. 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 orthopedic surgeon.
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.
CPM devices are used as alternatives and adjuncts to conventional physical therapy following surgery or injury. 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.
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 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.
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.
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.
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.
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.
Health care team roles
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.
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 microoganisms 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.
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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 Physical Therapy Association. 1111 North Fairfax
Street, Alexandria, VA 22314-1488. (703) 684-2782. <http://www.apta.org>.
Jennifer E. Sisk, M.A.