Joint distraction is a non-fusion, joint-preserving surgical technique for treating degenerative joint conditions. The procedure involves temporarily separating the two surfaces of an affected joint to create a small gap. This separation relieves the mechanical stress and bone-on-bone contact that causes pain and degeneration in conditions like osteoarthritis.
Biological Principles of Joint Distraction
The primary mechanism involves the temporary mechanical unloading of the joint surfaces. This immediate relief from damaging load creates a permissive biological environment for healing by reducing the excessive compressive forces that accelerate cartilage wear.
The distraction space also dramatically improves the circulation and molecular composition of the synovial fluid. Movement, even with the external fixator in place, causes hydrostatic pressure fluctuation within the joint capsule. This pressure oscillation acts like a pump, driving nutrient-rich synovial fluid into the cartilage and helping to remove metabolic waste products.
This altered biomechanical and biochemical environment promotes chondrogenesis, the formation of new cartilage. Studies show an increase in type-II collagen synthesis, suggesting the regenerated tissue is durable, hyaline-like cartilage, which is superior to the fibrocartilage often formed after other repair procedures. Furthermore, the prolonged separation mobilizes mesenchymal stem cells, which are recruited to the site of damage and differentiate into new cartilage cells.
Common Joints Treated and Indications
Joint distraction is most commonly applied to large, weight-bearing joints, with the knee and ankle being the most frequently studied locations. The technique is primarily indicated for patients with early to mid-stage osteoarthritis who are considered too young for a total joint replacement. Joint distraction serves as a joint-sparing alternative for these active individuals.
The procedure has also been successfully applied to the hip joint, particularly for treating avascular necrosis (AVN) of the femoral head in adolescents. AVN involves the death of bone tissue due to a lack of blood supply, and distraction allows the femoral head to regenerate without the compressive forces that cause it to collapse. The technique is sometimes used for the temporomandibular joint (TMJ) and in cases of chondrolysis, a rapid destruction of cartilage.
The Patient Experience: Procedure and Rehabilitation
The treatment begins with a minimally invasive surgical procedure performed under general or spinal anesthesia. The surgeon inserts specialized pins into the bone on either side of the joint. These pins are then connected to an external fixation device, which acts as a rigid frame outside the body.
Following surgery, the patient enters the distraction phase where the joint surfaces are gradually separated. The joint is typically distracted by a small, controlled amount, such as 0.5 millimeters, multiple times per day over several days. This gradual process achieves the target separation, commonly around five millimeters, which is then maintained for several weeks to months.
During the distraction period, which typically lasts between six weeks and three months, patients are often encouraged to walk and bear weight. The internal springs within the fixator allow for slight, controlled axial movement that enhances the hydrostatic pressure effect, further stimulating the cartilage. Pin tract infections are the most common complication during this phase but are usually managed effectively with oral antibiotics.
Once the consolidation phase is complete, the external fixator is removed in a minor, usually outpatient procedure. Rehabilitation focuses on intensive physical therapy to overcome muscle atrophy and joint stiffness. Patients work to restore full range of motion and strength, with functional recovery often taking several months.