Microfracture
Microfracture is a technique that began in the 1980s but gained popularity in the early 2000s with the goal of treating articular cartilage defects in the knee by accessing bone marrow cells deep to the subchondral surface to heal full-thickness cartilage defects.[15] These marrow elements contain growth factors that promote filling of the chondral defect with fibrocartilage. Microfracture is an option for small full-thickness cartilage lesions <2 cm2 in size that are contained with a healthy rim of surrounding cartilage. Contraindications include global cartilage degeneration, inability to comply with weight bearing restrictions after the procedure, and a noncontained defect that a clot from the marrow contents will not form in.[15,16]
The procedure is performed using awls, picks, or drills to produce microfractures in the subchondral bone perpendicular to the surface and at least 3 to 4 mm apart from one another. It is important to have a stable rim of healthy intact cartilage around the chondral defect so that a clot can form in this area. In preparation of the site, studies have shown benefit to debriding the calcified cartilage layer so that only subchondral bone remains in the defect.[15,16] Blood and fat emanating from the site without a tourniquet inflated should be verified to assure that the subchondral surface was penetrated deep enough (Figure 3). This should be performed at the end of the procedure so that bleeding does not obstruct your view during arthroscopy and to allow clot formation at the cartilage defect site.
Figure 3.
Photographs showing the microfracture technique: (A) the cartilage lesion was débrided using a shaver and curets to a stable rim of healthy cartilage and removal of all calcified cartilage. Microfracture holes are seen approximately 3 to 4 mm apart from one another throughout the lesion. B, The tourniquet was let down, and blood is seen coming from all microfracture sites.
Historically, microfracture was most often used as an initial inexpensive and simple treatment. It was thought that there was no harm and that other cartilage restoration options would still be available to treat the cartilage lesion if microfracture failed. Some studies have shown satisfactory short-term results[17,18] but others demonstrate deterioration of function after 2 years, especially when compared with other treatment options for small cartilage defects.[19–21] Bone overgrowth occurs in more than 60% of patients, contributing to increased failure rates.[22] Animal studies also show altered subchondral architecture after microfracture with decreased bone mineral density.[23]
J Am Acad Orthop Surg. 2020;28(22):914-922. © 2020 American Academy of Orthopaedic Surgeons
