Microfracture surgery is an articular cartilage repair surgical technique that works by creating tiny fractures in the underlying bone. This causes new cartilage to develop from a so-called super-clot.
The surgery is quick (typically lasting between 30 and 90 minutes), minimally invasive, and can have a significantly shorter recovery time than an arthroplasty (knee replacement).
Chronic articular cartilage defects do not heal spontaneously. However, acute traumatic osteochondral lesions or surgically created lesions extending into subchondral bone, e.g. by Pridie drilling, spongialization abrasion or microfracture causing the release of multipotent mesenchymal stem cells from the bone marrow, may heal with repair tissue consisting of fibrous tissue, fibrocartilage or hyaline-like cartilage. The quality of the repair tissue after these "bone marrow stimulating techniques" depends on various factors including the species and age of the individual, the size and localization of the articular cartilage defect, the surgical technique, e.g., how the subchondral bone plate is treated, and the postoperative rehabilitation protocol.
History
The surgery was developed in the late 1980s and early 1990s by Dr. Richard Steadman of the Steadman-Hawkins clinic in Vail, Colorado. Steadman slowly refined the procedure through research (including tests on horses). The surgery was called "controversial" by many sportswriters, due to a lack of studies on the long-term effects and the fact that an unsuccessful surgery could end an athlete's career. Steadman has also adapted the surgery into a treatment to help reattach torn ligaments (a technique he calls the "healing response").
Procedure
The surgery is performed by arthroscopy, after the joint is cleaned of calcified cartilage. Through use of an awl, the surgeon creates tiny fractures in the subchondral bone plate. Blood and bone marrow (which contains stem cells) seep out of the fractures, creating a blood clot that releases cartilage-building cells. The microfractures are treated as an injury by the body, which is why the surgery results in new, replacement cartilage. The procedure is less effective in treating older patients, overweight patients, or a cartilage lesion larger than 2.5 cm. Further on, chances are high that after only 1 or 2 years of the surgery symptoms start to return as the fibrocartilage wears away, forcing the patient to reengage in articular cartilage repair.
The effectiveness of cartilage growth after microfracture surgery is thought to be dependent on the patient's bone marrow stem cell population and some think increasing the number of stem cells increases the chances of success. A couple of physicians are promoting an alternative treatment implanting autologous mesenchymal stem cells directly into the cartilage defect, without having to penetrate the subchondral bone.
Microfracture reports
Studies have shown that microfracture techniques do not fill in the chondral defect fully, forming fibrocartilage rather than hyaline cartilage. Fibrocartilage is not as mechanically sound as hyaline cartilage; it is much denser and unable to withstand the demands of everyday activities as well as the original cartilage and is thus at higher risk of breaking down. The blood clot is very delicate after surgery and needs to be protected. In terms of time, the clot takes about 8 to 15 weeks for conversion to fibrous tissue and is usually fibrocartilage by about four months post surgery, holding implications for the rehabilitation.
Chondrocyte implantation procedures (CCI), a cell-based articular cartilage repair procedure that aims to provide complete hyaline repair tissues for articular cartilage repair, have been posed by some as an alternative to microfracture surgery. In February 2008, Saris et al. published a large-scale study claiming that CCI results in better structural repair for symptomatic cartilage defects of the knee than microfracture surgery. According to the study, one year after treatment, the regenerated tissue associated with CCI is of better quality than that of microfracture surgery.