The originator of the biologic concept of Continuous Passive Motion (CPM) is Dr Robert B. Salter, CC, MD, MS, FRCSC, a pioneer in the field of orthopaedic surgery who served as Chief of Orthopaedic Surgery at Toronto’s Hospital for Sick Children for over ten years followed by surgeon in chief for 10 years and University professor for 20 years.

Dr. Salter has published more than 150 articles as well as a major textbook, Diseases of the Musculoskeletal System. His honours include the 1969 Gairdner International Award for Medical Science for his contributions to the understanding of cartilage degeneration and growth disturbance of the epiphyseal plate, induction into the Canadian Medical Hall of Fame, and the 1997 F.N.G. Starr Award, which is the highest award the CMA can bestow upon a member.

Recognized as a world-renowned surgeon, teacher, and scientist, Dr. Salter now serves as the surgeon-in-chief emeritus and senior orthopaedic surgeon emeritus at the Hospital for Sick Children. In 2006 he was named a Giant of basic research by the University of Toronto.

In 1994, Dr. Salter published The Physiologic Basis of Continuous Passive Motion for Articular Cartilage Healing and Regeneration, in which he presented an overview of the first 23 years of basic research on the biologic concept of CPM and the first 15 years of his experience with the clinical application of CPM to a variety of disorders and injuries.

1. Synovial joints were meant to move and actually deteriorate when not allowed to do so,
2. 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,
3. The synovial membrane should glide over the articular surface and becomes adherent to the underlying cartilage if prevented from such gliding by motion, and
4. 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:

1. Enhance metabolic activity and joint nutrition,
2. Stimulate pluripotential cells to differentiate into hyaline cartilage rather than fibrocartilage or bone, thereby leading to healing and regeneration of hyaline cartilage, and
3. Accelerate healing of articular cartilage and periarticular structures, such as tendons and ligaments.

Overview, Results, and Conclusions of Basic Research
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.

This basic research led Dr. Salter to the conclusions that CPM:

1. Is well tolerated,
2. Has significant stimulating effects on articular cartilage and peri-articular tissues,
3. Prevents adhesion formation and joint stiffness,
4. Does not interfere with, and actually enhances, healing of incisions over a moving joint, and
5. Regeneration of articular cartilage through neochondrogenesis is possible under the influence of CPM.

Clinical Applications and Results
In 1978, Dr. Salter began to apply CPM to patients 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.

Prescribing CPM

• The number of authorized physical therapy visits patients receive has drastically reduced over the last several years. 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.
• 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.
• 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:
  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
  • No differences in ROM, knee score, flexion contracture, or extensor lag between the two groups at 6 months post-op
  • Authors found CPM an acceptable alternative to PT with no significant differences in results but markedly reduced cost