Microfracture Surgery

Microfracture is a surgical option used in the treatment of areas of damaged cartilage. When a patient has a small area of damaged cartilage (not widespread arthritis), microfracture may be performed in an attempt to stimulate new cartilage growth.  Microfracture is most often performed inside the knee joint, although it has also been used for treatment in other joints including the hip, ankle, and shoulder.

A microfracture procedure creates small holes in the bone. The surface layer of bone, called the subchondral bone, is hard and lacks good blood flow. By penetrating this hard layer, a microfracture allows the deeper, more vascular bone to access the surface of the joint. This deeper bone has a more rich blood supply, and the cells can then get to the surface layer to stimulate cartilage growth.

Who is a good candidate for microfracture?

• Patients with limited areas of cartilage damage
• Patients who are active and cannot participate in their sport or activity because of symptoms
• Patients with pain or swelling caused by the damaged area of cartilage

Who is not a good candidate for microfracture?

• Patients with widespread arthritis of the joint
• Patients with instability or malalignment of their joint
• Patients who are inactive
• Patients with inflammatory arthritis (such as rheumatoid arthritis)
• Patients unwilling to participate in rehabilitation following microfracture

Does It Work?

Microfracture can be an excellent procedure, providing substantial pain relief when done in the right patient.  One of the concerns with microfracture is that it does not stimulate the growth of normal joint cartilage. There are many types of cartilage, and one of these types (hyaline cartilage) is normally found on the joint surface.

Microfracture stimulates the growth of a type of cartilage commonly found in scar tissue (fibrocartilage). Unlike hyaline cartilage, fibrocartilage does not have the same strength and resiliency of cartilage normally found in a joint. Therefore, there is a chance that the cartilage stimulated by a microfracture procedure will not stand up over time.

How Microfracture Surgery Is Performed

A microfracture is performed as part of an arthroscopic knee surgery.  Other joints can be treated similarly, also by arthroscopic surgery. Microfracture has been performed in the ankle, shoulder, hip, elbow and other joints. While it is by far most commonly performed for knee joint problems, it can also be used effectively for problems in other joints in the body.

First, the area undergoing microfracture is prepared by removing any loose or damaged cartilage. Ideally, the area undergoing microfracture will be less than about 2 centimeters in diameter and have good, healthy surrounding cartilage. Then, a small, sharp pick (awl) is used to create the small microfracture holes in the bone. The number of microfracture holes created depends on the size of the are being treated. Most patients with a 1 to 2-centimeter area of damage require 5 to 15 small holes in the bone.

The penetration of the outer layers of bone allows blood and stem cells to form a clot in the area of the cartilage defect. These cells have the ability to form a cartilage layer within the defect. Essentially the body is able to repair the damaged area of cartilage by stimulating blood flow to the defect.

One of the keys to successful treatment is appropriate rehabilitation following the microfracture surgery. Rehabilitation must protect the area treated by microfracture as well as maintain the strength and motion of the knee joint.  As a result, most patients need to use crutches after surgery, often a knee brace will be recommended, and in some situations a motion machine to bend the knee may be used.

Microfracture surgery of the knee joint is a safe procedure with minimal risks.  In fact, the primary risk is having persistent pain despite this attempt to heal the area of cartilage damage.  Other risks of arthroscopic surgery include infection, blood clot, stiffness, and swelling of the knee joint.  These more severe risks are uncommon after microfracture surgery.

Results of Microfracture

Microfracture surgery is popular because it is safe, relatively easy to perform, and comparatively inexpensive to other cartilage stimulation surgical procedures. But does it work? The results of microfracture surgery have been investigated many times. In general, people who undergo microfracture surgerydo reasonably well in the short to mid term. There are questions, however, about the durability of microfracture repair, and most surgeons agree that the cartilage that heals within a microfracture defect is not nearly as durable as normal cartilage. For that reason, the longer term results are less satisfactory, and people who undergo this surgical procedure may end up having problems with the progression of arthritis over time.

Alternatives to Microfracture

Patients who are good candidates for microfracture could also be good candidates for other treatments for cartilage defects of the knee. These alternatives include cartilage transfer and cartilage implantation.  However, the results of all of the surgical options to address cartilage damage has been shown to be similar, while the risks and costs of microfracture are dramatically less.  Therefore, microfracture surgery is generally considered the first-line treatment for cartilage damage in the knee joint. Some of these other surgical options are generally done for athletes who have failed to improve after microfracture surgery.

_Sources:

Tuan RS, Chen AF, Klatt BA. "Cartilage regeneration" J Am Acad Orthop Surg. 2013 May;21(5):303-11.

Safran MR, Seiber K. "The evidence for surgical repair of articular cartilage in the knee" J Am Acad Orthop Surg. 2010 May;18(5):259-66.