The microfracture technique introduced by Dr. Richard Steadman is considered to be the first-line surgical option for full-thickness articular cartilage defects because of its minimally invasive nature as well as its technical ease, limited surgical morbidity and low cost. The damaged cartilage section is débrided to stable, squared-off edges. This provides a pool for the clot to form.  The underlying bone is scraped, and then penetrated using an awl, causing medullary bleeding and clot formation. Marrow stem cells in the clot mature to yield a fibrocartilage repair tissue that is of inferior stiffness and that has poorer wear characteristics than does normal hyaline cartilage. Limited weight bearing and continuous passive motion are key elements in postoperative success. Dr. Steadman has reported that up to 80% of young patients with isolated posttraumatic, full thickness chondral defects that were treated with microfracture were improved at an average follow-up of 7 years.  He also noted that worse outcomes were associated with patients aged >30 years and with microfracture treatment of lesions sized >2 cm2 and located in the central portion of the medial femoral condyle.  Advanced arthritis and lack of compliance with rehab protocols, especially the lack of use of a continuous passive motion (CPM) device were also related to poorer outcomes.

For those of you interested, I have included Dr. Steadman’s rehab protocol from his original surgical technique article.

Lesions on the weightbearing surfaces of the femoral condyles are treated immediately postoperatively (commencing in the recovery room) with a continuous passive motion (CPM) machine. We start the machine with a range of motion of 30 ° to 70 °, and then increase it as tolerated by 10 ° to 20° every 2 hours. The rate of the machine is usually 1 cycle per minute, but rate can be varied to the preference of the patient. Many patients tolerate the use of the machine at night. For those who do not, however, our experience indicates that intermittent use during the day is equally beneficial. If the patient is unable to use the CPM, then instructions are given to passively flex and extend the knee with 500 repetitions 3 times per day. The primary goal is to regain full passive range of motion of the injured knee as soon as possible after surgery.

 

These patients are treated with a period of crutchassisted touchdown weight-bearing ambulation for 6 to 8 weeks, depending on the size of the lesion. For most lesions, our experience indicates that 6 to 8 weeks is the appropriate time to limit weight-bearing. However, for lesions that are small (<1 cm in diameter), we may shorten this time period by a few weeks. Rarely do we use a brace for lesions on the femoral condyles.

 

Limited strength training also begins immediately. Patients perform double leg one-third knee bends the day after surgery. 5 Since they are touchdown weight-bearing, patients place most (75% to 80%) of their body weight on their uninjured leg to perform the exercise. Spinning on a stationary bike and a deep water program are begun at 2 weeks after microfracture surgery. The deep water exercises include use of a kick board as well as a flotation vest for deep water running. After 8 weeks, patients progress to full weight bearing and begin a more vigorous program of active motion of the knee. Elastic resistance cord exercises are begun at approximately 8 weeks after microfracture surgery. A detailed description of use of the cord and the exercises have been published previously. The maximal levels for sets and repetitions using elastic resistance cord exercises are an excellent indicator for progressing to weight training. Free or machine weights are permitted when the patient has achieved the early goals of the rehabilitation program, but not before 16 weeks after microfracture surgery. We strongly emphasize the importance of proper technique when beginning a weight program. Depending on the clinical examination, we may recommend a return to sports that involve pivoting, cutting, and jumping after approximately 4 to 6 months.

 

Op Tech Orthop 1997;7:300-304