Left knee-joint from behind, showing interior ligaments. (Lateral meniscus and medial meniscus are cartilage.)

Microfracture surgery is one of the articular cartilage repair surgical techniques that works by creating tiny fractures in the underlying bone. This causes new cartilage to develop from a so-called super-clot. Microfracture surgery has gained a profile in the sports world in recent years; numerous professional athletes including members of the NBA (most notably Anfernee Hardaway, Greg Oden, Allan Houston, Kenyon Martin, Tracy McGrady and Amar'e Stoudemire), NFL and NHL have undergone the procedure.

The surgery is quick (taking as short as 30 minutes but it is not unusual to take as long as 90 minutes), is minimally invasive, and can have a significantly shorter recovery time than an arthroplasty (knee replacement). Combined with a high rate of success, these factors have caused orthopedic surgeons to use the procedure with increasing frequency.

[edit] Background

Chronic articular cartilage defects do not heal spontaneously^[1]. However, acute traumatic osteochondral lesions or surgically created lesions extending into subchondral bone, e.g. by Pridie drilling^[2], spongialization^[3] abrasion^[4] or microfracture causing the release of pluripotent mesenchymal stem cells from the bone marrow, may heal with repair tissue consisting of fibrous tissue, fibrocartilage or hyaline-like cartilage^[5]. 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^[6].

[edit] Development

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)^[7]. After Steadman experienced success with the surgery, professional athletes started taking notice. The surgery was soon 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.^[8] However, Steadman and other researchers have proven that compared to other treatments, the procedure is safe and effective, even in the long term.^[9] Dr. Steadman has also adapted the surgery into a treatment to help reattach torn ligaments (a technique he calls the "healing response") that he successfully used on alpine skiier Bode Miller.^[10] Possible applications in the hip and ankle joints have also been speculated on.^[11]

[edit] Procedure

The surgery is performed by arthroscopy. After cleaning the calcified cartilage, the surgeon creates tiny fractures in the adjacent bones (through the use of an awl). 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.^[12] The procedure is less effective in treating older patients, overweight patients, or a cartilage lesion larger than 2.5 cm.^[12] 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. This is not always the case and microfracture surgery is therefore considered to be an intermediate step.^[13]

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 physicians are promoting an alternative treatment implanting autologous mesenchymal stem cells directly into the cartilage defect, without having to penetrate the subchondral bone^{[14] [15]}

[edit] Microfracture Reports

Studies have shown that microfracture techniques don't fill in the chondral defect fully and the repair material they form is fibrocartilage. Fibrocartilage is not as good mechanically as the original hyaline cartilage; it is much denser and isn't able to withstand the demands of everyday activities as well as hyaline cartilage and is therefore at higher risk of breaking down.^[16] The blood clot is very delicate after surgery and needs to be protected. In terms of time, the clot takes about 8 weeks to 15 weeks convert to fibrous tissue and is usually fibrocartilage by about four months post surgery (this has implications for the rehabilitation).^[17]

In February 2008, Saris & al published a large scaled study that showed that Characterized Chrondocyte Implantation (CCI) results in better structural repair for symptomatic cartilage defects of the knee than microfracture surgery. One year after treatment, the tissue regenerate associated to CCI is of better quality than that of microfracture.^[18] Chrondrocyte Implantation procedures are cell based articular cartilage repair procedures that aim to provide complete hyaline repair tissues for articular cartilage repair.

[edit] Use in professional sports

There have been many notable professional athletes who have undergone the procedure. Partially because of the high level of stress placed on the knees by these athletes, the surgery is not a panacea and results have been mixed. Many players' careers effectively end despite the surgery. However, some players such as Jason Kidd, Steve Yzerman, John Stockton, Kenyon Martin, Antonio McDyess and Zach Randolph [2] have been able to return at or near their pre-surgery form while players Brian Grant, Chris Webber, Allan Houston and Penny Hardaway never regained their old form. Others such as Jamal Mashburn and Terrell Brandon never recovered and retired. Portland Trail Blazers rookie Greg Oden underwent the procedure in early September 2007 and missed the entire 2007-2008 NBA season. At only 19 at the time of the surgery, doctors are confident that he will return to at or near full strength by the 2008-2009 season. Rockets Superstar Tracy McGrady also under went microfracture surgery, doctors are confident that the 2 time scoring champion will return to full strength.^[19]

In October 2005, young star Amare Stoudemire of the NBA's Phoenix Suns underwent one of the highest-profile microfracture surgeries to date. He returned to the court in March 2006 and initially appeared to have made a full recovery, but subsequently started feeling stiffness in both knees (his right knee had been overcompensating for the injured left knee). He and the team doctor decided he needed more time to rehab and he did not return until the 2006-2007 NBA season.^[20] During the 2006-2007 season, Stoudemire returned to form, averaging 20.4 points and 9.6 rebounds per game while playing in all 82 regular-season games and the 2007 NBA All-Star Game. His recent success has brought positive publicity to the procedure, further distancing it from a previous reputation as a possible "career death sentence" in the sports world, though he was one of the youngest of the aforementioned players to undergo the surgery. ^[21]

[edit] Recovery

Current studies have shown a success rate of 75 to 80 percent among patients 45 years of age or younger, even among professional athletes.^[9][11] With the help of physical therapy, patients can often return to sports (or other intense activities) in about four months. However, this is a best-case scenario and depends on the severity of the cartilage damage (and any other conditions existing in the knee). Normal patients and professional athletes who play at the highest level however are quite different, as Chris Webber, who underwent the surgery, has stated that a full recovery in four months is nearly impossible. Webber returned to the NBA eight months after his surgery but was never the same.^[22] Microfracture surgery itself is relatively minor. It is an outpatient procedure and causes only small discomfort. The harder part is the restrictions that are placed on the patient during the post-operative recovery period. This can be a major challenge for many patients. For optimal re-growth of joint surface, the patients need to be very patient and also extremely cooperative. They usually need to be on crutches for four to six weeks (sometimes longer). Sometimes a brace is needed. This all depends on the size and/or location of the joint surface defect that is being repaired or regenerated. The patients are encouraged to spend approximately 6-8 hours a day on a CPM (Continuous Passive Motion) machine that helps with optimal re-growth of joint surface. Patients usually feel pretty good and think they can avoid these critically important steps, and even start running and jumping (or playing sports) before the internal aspects of the knee, and the joint surface, are ready.

[edit] References

[edit] External links

• Articular Cartilage Repair of the Knee
• MedlinePlus Medical Encyclopedia
• Cartilage Health - Information on Articular Cartilage Injury Prevention, Repair and Rehabilitation