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Thursday, October 27, 2005

Microfractures and Objective Questions (MCQs)

Microfracture is a surgical procedure aimed at cartilage regeneration.

The arthroscopic technique involves clearing damaged tissue from the knee joint and creating tiny holes ("microfractures") in the bone area where the cartilage is defective.

The underlying bone marrow seeps out through the holes and becomes part of a blood clot that forms over the area.

The marrow contains stem cells, which have the ability to form replacement cartilage between the bare-bone surfaces of the knee. Appropriate rehabilitation of the knee after surgery is critical to the success of the operation.

Continuous Passive Motion (CPM), where the knee is moved gently by a machine for 5-8 hours a day for several weeks, keeping weight off of the joint for a period of 6-8 weeks, and strict adherence to an aggressive physical therapy program following surgery all appear to enhance the success of the procedure.

AIIMS NOV 2003 question
microfracture is done for?
1) delayed union femur
2) non union of tibia
3) loose bodies of ankle joint
4) osteochondral defect of femur

Answer is 4) Osteochondral defect of femur

Isolated articular cartilage lesions in the knee are common and are difficult to treat. A number of treatment modalities have been utilized in an effort to promote the regeneration of articular cartilage, including microfracture (MFX) and autologous chondrocyte Implantation (ACI).
Management of focal chondral defects
Isolated superficial cartilage injuries that do not penetrate the vascular subchondral bone do not heal and may enlarge for several years following the initial injury, potentially leading to overt degenerative arthritis. Full-thickness cartilage injuries that penetrate the more vascular subchondral bone permit local access to an undifferentiated cell pool (primitive mesenchymal stem cells) capable of forming fibrocartilage or "scar cartilage." Fibrocartilage is composed predominantly of type I collagen and is biochemically and mechanically inferior to normal hyaline articular cartilage, which is composed predominantly of type II collagen. Fibrocartilage formation is the biological basis for the MSTs commonly used to treat symptomatic full-thickness cartilage defects.

Abnormal shear and blunt forces are manifested at the junction of the uncalcified and calcified cartilage layers, potentially creating isolated cartilage injury extending to the subchondral bone. This is otherwise known as a focal or full-thickness cartilage defect. Typically, femoral lesions result from shear stress due to a twisting injury; patellofemoral joint lesions result from direct trauma to the front of the knee. The natural history of an asymptomatic full-thickness cartilage defect and its relationship to the development of secondary degenerative changes typically seen in osteoarthritis is poorly understood. However, lesions that become symptomatic inexorably progress, leading to reciprocal degenerative changes at the opposing articular surface.

The goals of any surgical option used to treat articular cartilage defects are to restore the joint surface, leading to full, painless range of motion; and halting cartilage degeneration. Surgical options can be palliative (ie, arthroscopic debridement and lavage), reparative (ie, MSTs), or restorative (ie, ACI and osteochonral grafts). Osteochondral grafts can be obtained from the patient (ie, autografts) or from cadaveric donors (ie, allografts). Arthroscopic debridement and lavage was discussed previously. Most studies reflect outcomes following the treatment of established osteoarthritis, not of isolated focal chondral defects.

Determining the appropriate surgical option is a complex process.24 Decision-making is affected by the following variables: the size of the defect (ie, smaller or larger than 2 cm2), the number and type of previous surgeries (ie, primary or secondary), location of the defect (ie, femoral condyle, trochlea, or patella), patient demands and expectations, and coexisting pathologic lesions (ie, ligament tears, malalignment)

Source: Steadman J, Rodkey W, Singleton S, et al. Microfracture technique for full-thickness chondral defects. Op Tech Ortho 1997;7(4):300-4

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