Chapter 32 Microfracture Procedure of the Knee
Surgical Overview
• Articular cartilage plays a crucial role in the function of the musculoskeletal system by permitting nearly frictionless motion to occur between the articular surfaces of synovial joints.
1 Its unique structure allows a joint to withstand high compressive and shear loads throughout a lifetime.
• Several studies have demonstrated the medial femoral condyle to be the most common location for full-thickness focal chondral defects. These lesions are commonly found in the area that contacts the tibia between 30 and 70 degrees of flexion.
• The microfracture procedure begins with an arthroscopic assessment of the articular cartilage defect.
1 A debridement of the base of the defect is then performed to fully expose the subchondral bone with a standard arthroscopic shaver or curved curette.
3 The walls of the perimeter of the defect should be perpendicular to the subchondral plate so that the marrow elements to follow will be optimally contained within the defect.
4 Arthroscopic angled awls are then used to make multiple perforations, or microfractures, in the exposed subchondral plate. These awls produce essentially no thermal necrosis of the bone compared with hand-driven or motorized drills.
5 The microfracture holes are approximately 3 to 4 mm apart and are typically made to a depth of 3 to 4 mm. These perforations serve as an access channel for blood and mesenchymal stem cells from cancellous bone and the marrow cavity to migrate into the prepared defect.
Rehabilitation Overview
• Rehabilitation of the patient following any articular cartilage procedure of the knee presents a challenging task for the rehabilitation specialist.
• The rehabilitation specialist should instill the importance of compliance to the patient early in the rehabilitation period because adherence to weight-bearing restrictions and home therapeutic exercise assignments will have a direct influence on functional outcomes.
• The clinician should appreciate the healing response throughout the rehabilitative course by continually providing an optimal environment where the articular cartilage lesion can heal.
• Using a working knowledge of the structure and function of articular cartilage, combined with an appreciation of the forces induced upon the articular surfaces of the knee during specific exercises and activities, will permit the clinician to protect and progress the patient toward an optimal outcome.
• Communication with the surgeon throughout the rehabilitative process is important because the size and location of the lesion will have a direct effect on the rehabilitation program.
• A therapeutic exercise program addressing a medial femoral condyle lesion on a weight-bearing surface will differ from a non-weight-bearing femoral surface or a patellofemoral defect.
• Postoperative “guidelines” should be individualized for each patient. The rehabilitative course should be advanced via a criteria-based approach.
• The ultimate goal of rehabilitation is to restore the range of motion (ROM), flexibility, strength, and proprioception needed for the functional demands of daily living and/or sports activity while protecting the healing cartilage and applying appropriate stresses.
