What is a CPM?
Continuous Passive Motion (CPM) is a postoperative therapeutic modality that passively - without patient effort - moves a joint through a prescribed range of motion (ROM) for an extended period of time. There are CPM devices for the hand, wrist, forearm, elbow, shoulder, jaw, great toe, ankle and knee. CPM is best applied immediately post-operatively and continued, uninterrupted, for up to 6 weeks, or as prescribed by the physician. Basic Premises and Hypotheses of CPM
The basic premises that led Dr. Salter to the concept of continuous passive motion were that:
- Synovial joints were meant to move and actually deteriorate when not allowed to do so,
- Motion enhances nutrition to the articular cartilage surface of synovial joints by facilitating the movement of synovial fluid into and out of the cartilage matrix,
- The synovial membrane should glide over the articular surface and becomes adherent to the underlying cartilage if prevented from doing so, and
- Synovial joints were meant to last a lifetime. With these premises in mind, Dr. Salter hypothesized that continuous passive motion should have the following effects on synovial joints:
- Enhance metabolic activity and joint nutrition,
- Stimulate pluripotential cells to differentiate into hyaline cartilage rather than fibrocartilage or bone, thereby leading to healing and regeneration of hyaline cartilage, and
- Accelerate healing of articular cartilage and periarticular structures, such as tendons and ligaments.
Dr. Salter and a succession of Basic Research Fellows have conducted experimental investigations in both adult and adolescent rabbits on the effects of CPM on full and partial-thickness defects, intra-articular fracture, acute septic arthritis, intra-articular fluid pressures, clearance of hemarthrosis, wound healing, muscle atrophy, immobilization, tendon and ligament healing, autogenous and allogenic intra-articular periosteal grafts, and chondral shaving and subchondral abrasion.
In 1978, Dr. Salter began to apply CPM to humans following procedures such as ORIF of intra-articular, metaphyseal, and diaphyseal fractures, surgical release of extra-articular joint contractures, arthrotomy and incision with drainage for acute septic arthritis, synovectomy, biologic resurfacing, ligamentous repair and reconstruction, tendon repair, tibial osteotomy, and total joint replacement.
Results from these clinical applications include: CPM is well tolerated, maintenance of an increased ROM, normal wound healing, absence of complications, and shortened period of hospitalization and rehabilitation. Additional clinical studies have been done over the past 20+ years that continue to support these findings. In 2004 a review of Fourteen of these clinical trials was published with the overall results showing that adding CPM to the post-operative rehab protocol increased active knee flexion, decreased the length of stay in a hospital and decreased the need for post-operative manipulation.
Why Prescribe CPM?Simply, CPM allows patients to maximise their therapy benefits and get back to motion and ADLs faster! The number of authorized physical therapy visits patients receive has drastically reduced with cost control measures. CPM used at home during the early stages of rehabilitation helps make the most of these limited visits; if a patient achieves their range of motion goals at home, physical therapy visits can focus on strengthening and return to function. Capitated Reimbursement:
- Shorter lengths of stay in both the hospital and transitional care unit, i.e. skilled nursing facility (SNF) mean that patients receive less physical therapy during the immediate post-operative period. SNFs are now under a capitated reimbursement system which can mean fewer resources allocated to the care of a patient - including outpatient physical therapy.
- Physicians are left with the dilemma of being responsible for favorable post-operative outcomes, but with significantly reduced available resources. The use of home CPM can ensure good outcomes and reduced rehabilitation costs.
For a more in depth study, please contact your local representative and ask for a copy of the research by Robert Worland, MD, et al: "Home Continuous Passive Motion Machine Versus Professional Physical Therapy Following Total Knee Arthroplasty: A prospective, randomized study on 103 consecutive post-TKR patients. The authors found CPM an acceptable alternative to PT with no significant differences in results but markedly reduced cost.
