The microfracture chondroplasty is a technique to treat full thickness cartilage defects that leads to the formation of new joint surface cartilage. The damaged area is debrided and then the underlying bone is punctured with a micro-instrument or pick to allow bleeding from the bone. The resulting blood clot that fills the cartilage defect has specialized cells which have the potential to transform into new cartilage.
This procedure is reserved for more significant areas of joint surface damage where the lesion is full thickness and down to the underlying bone. Microfracture can be performed on any size lesion, but better results have been obtained with lesions smaller than 400 mm.
The articular cartilage of the knee is 2 to 4 mm thick, avascular tissue devoid of nerves and lymphatics. Articular cartilage defects that extend for the full thickness to subchondral bone rarely heal without intervention. These injuries could be due to acute trauma or repetitive strain.
Initially developed for knee defects, microfracture chondroplasty is used now for hip, talus, elbow, and shoulder as well.
Indications for Microfracture Chondroplasty
Full thickness articular cartilage defects in the weight-bearing area between the tibia and femur.
Unstable cartilage flaps in these regions that extend to the subchondral bone are also lesions that are suitable for the microfracture chondroplasty technique.
Patients with acute injuries to the knee that result in full thickness cartilage loss are treated as soon as can be done. Patients with chronic lesions or degenerative lesions in the knee are treated conservatively initially for at least 12 weeks by activity modification, physical therapy, NSAIDs, and joint injections, as appropriate. Patients who have failed conservative treatment for chronic or degenerative lesions then become candidates for microfracture chondroplasty.
Microfracture should not be performed in patients who unreliable or are unable to complete the rehabilitation required are less likely to benefit from the procedure. Advanced age, generalized degenerative changes, inflammatory arthritis, and unstable knees are relative contraindications.
Surgical Technique of Microfracture Chondroplasty
Microfracture chondroplasty can be performed on patients with either regional or general anesthesia in supine position on a standard operating table.
Standard arthroscopic portals can be used for microfracture.
The lesion is identified for microfracture and probed thoroughly to make sure that all bordering cartilage is stable. A creation of stable full-thickness borders of cartilage surrounding a central lesion is optimal for microfracture chondroplasty as it provides some degree of protection to the regenerating tissue that is forming in the treated lesion.
Using a shaver, all loose flaps of cartilage are removed.The removal of the calcified cartilage layer is important and is usually performed carefully using a hand-held curette.
After the bed is prepared, arthroscopic awls are used to complete the microfracture chondroplasty. The awls are advanced through the subchondral bone to create multiple small holes or microfractures to a depth that allows the return of fat droplets or blood from the cancellous bone. The depth required is typically 2 to 4 mm. The holes in the bone are made as close together as possible without breaking one into the next.
The microfracture awl produces a roughened surface in the subchondral bone to which the marrow clot can adhere more easily. The integrity of the subchondral plate is also maintained during this process when done correctly.
Once the microfracture is complete, the equipments are removed from the joint. Intra-articular drains should not be used. All portal sites are closed with suture and wounds are dressed.
After the procedure, the patient is put on continuous passive motion, as tolerated. Stationary biking without resistance and a deep-water exercise programs are started at 1 to 2 weeks after microfracture.
Patients with weight-bearing lesions are also prescribed toe-touch weight bearing with crutches for 6 to 8 weeks.
Patients who have undergone microfracture chondroplasty in the patellofemoral joint are treated in a locking brace with flexion limited to 20 degrees to eliminate shear forces across the treated lesion during walking. Brace is removed/unlocked only for continous passive motion exercises. The brace is worn for at least 8 weeks. The brace is then discontinued after full range of motion is gradually achieved over approximately 1 week.
Anti-inflammatory medications and physical therapy modalities are also prescribed as appropriate.
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