Microfracture surgery is performed to try to restore a full-thickness cartilage defect of the knee. Introduced over 20 years ago, this arthroscopic procedure uses the body’s own healing abilities to enrich tissue regeneration to the chondral surface.
What factors Should be Considered Before Microfracture Surgery?
• The patient’s age
• The patient’s activity level
• The patient’s knee alignment. Patients with “knock-kneed” or “bowlegged” are not good candidates for this procedure.
What is the Pathology of Articular Cartilage Damage?
In effect, a cartilage defect in the knee is like a “pothole” in the road. The opposing surface of cartilage can bump against it and either roll over it or become gouged out over time. The purpose of the microfracture surgery is to fill in the “pothole.” Just like a pothole being filled in in the street, if a microfracture is subjected to lower loads, like on a quite side road, there is a better chance that it will be more durable over time than one that is subjected to higher-impact loads, like on a motorway which frequently have to be resurfaced every year because of big trucks causing the potholes to reform. Thus, a patient will be more likely to have a better outcome after a microfracture if they participate in low impact activities instead of returning to higher impact activities like running.
How is Microfracture Surgery Performed?
Microfracture surgery is performed arthroscopically. The size of the defect that is being treated can make a big difference because smaller defects have more durable fibrocartilage scar tissue heal in the area of the microfracture.
When a microfracture surgery is performed, holes are made in the exposed bone, about 3 to 4mm apart, to try to release some of the stem cells which will ultimately form a clot in the area of the microfracture. This marrow rich clot is the base for new tissue formation. The microfracture technique produces a rough bone surface that the clot adheres to more easily. This clot eventually matures into firm repair tissue that become smooth and durable.
During the initial timeframe, the clot is at risk for being dislodged if the patient bears too much weight or performs too many activities. That is the reason that patients are kept nonweightbearing for 6 weeks after a microfracture. In addition, constant motion over the area of the microfracture can help it to form better to the contour on the end of the bone.
What is Microfracture Recovery Like?
For microfracture recovery, the rehabilitation program is crucial to optimise the success of the surgical technique. Weight-bearing is usually initiated at 6 weeks after the microfracture. During this time, it is important that a slow progression of weight-bearing is followed to allow the microfracture tissue to harden more over time. If activities are initiated too quickly after microfracture recovery, the microfracture may not heal or may heal with soft fibrocartilage. If the microfracture heals with a more softened state, even though it does cover the end of the bone, it often may not be functional and patients may have a recurrence of pain. Depending upon the location of the microfracture and the size of the defect, it can take anywhere from 4 to 7 months to be able to heal to the point where patients can increase their activities and potentially initiate occasional impact activities.
Microfracture Knee Surgery FAQ
Is microfracture a “cure” for osteoarthritis?
No, microfracture is a technique to help form a new surface to cover articular cartridge defects. If successful, it minimises pain and swelling and helps joint function.
Is the new tissue that forms after the microfracture identical to the original articular cartilage?
No, the new tissue is fibrocartilage. Experience shows that fibrocartilage is durable and functions similarly to articular cartilage, though it is not as good as articular cartilage.