Indications for OATS

The ideal chondral defect would be relatively small, full thickness defect in the range of 10-20mm. Unfortunately, very large, deep defects are not suitable to OATS due to technical limitations including the inability to reconstruct subchondral bone and limited availability of donor graft.  Articular cartilage, with underlying bone, measuring from 6-10 mm in diameter, is transferred from a less important area to the area of the defect.  This is done all arthroscopically.

MICROFRACTURE 

Microfracture is a surgical technique that has been developed to treat chondral defects, which are damaged areas of articular cartilage of the knee. It is a common procedure used to treat patients with full thickness damage to the articular cartilage that goes all the way down to the bone.

This arthroscopic procedure was first introduced about 20 years ago as a treatment method that uses the body's own healing abilities and provides an enriched environment for tissue regeneration on the chondral surface.

Since its development, the microfracture procedure has been used by its originator to treat more than 2000 patients. Of these patients, 75 to 80% experienced significant pain relief and improvement in the ability to perform daily activities and participate in sports. Fifteen percent noticed no change, and five percent continued to have joint deterioration.

What are the signs and symptoms of an articular cartilage injury that may be treated with the microfracture technique?

• Intermittent swelling - Loose fragments floating in the knee can cause swelling to occur.
• Pain - Pain with prolonged walking or climbing stairs can occur.
• Giving way - The knee may occasionally buckle or give way when weight is placed upon it.
• Locking or catching - Loose, floating pieces of cartilage may catch in the joint as it bends, causing the knee to lock or have limited motion.
• Noise - The knee may make noise (called crepitus) during motion, especially if the cartilage on the back of the kneecap is damaged. This noise is often described as "snap, crackle, and pop".

After articular cartilage damage has been diagnosed, what factors are indications for microfracture?

The general indications for microfracture are:

• The patient has a full-thickness defect (loss of articular cartilage down to the bone) in either a weightbearing area between the femur and tibia or in an area of contact between the back of the patella and the groove it slides in.
• The patient has unstable cartilage covering the underlying bone.
• The patient has degenerative changes in a knee that is normally aligned.

Important factors to consider for use of the microfracture procedure are:

• The patient's age (as a relative indication)
• The patient's activity level
• Whether or not the patient has acceptable alignment of the knee. "Knock-kneed" or "bowlegged" patients may not be good cadidates for this procedure.

When is microfracture not recommended for a patient?

Microfracture is not recommended when:

• the patient's knee is poorly aligned.

• the patient's chondral defect is not all the way through the full thickness of the cartilage.
• the patient is not willing to follow a strict and rigorous rehabilitation protocol.
• the patient is older (generally over 65) and might have difficulty with crutch use and the rehabilitation process.
• the patient has disease-induced arthritis, cartilage disease, or any disease affecting the immune system (e.g. rheumatoid arthritis).

Most patients progress through the postoperative period with little or no difficulty. Some patients may develop mild transient pain, most frequently after microfracture has been performed on the patella (kneecap) and trochlear groove (the groove on the femur in which the patella glides during motion). Small changes in the articular surface of this patellofemoral joint may produce a grating or "gritty" sensation, particularly when a patient discontinues use of the knee brace and begins normal weightbearing through a full range of motion. Patients rarely have pain at this time, and this grating sensation typically resolves on its own in a few days or weeks.

Similarly, if a steep perpendicular rim was made in the trochlear groove, patients may notice "catching" or "locking" as the ridge of the patella rides over this area during joint motion. Some patients may even notice these symptoms while using the continuous passive motion machine (CPM), a device that gently moves the joint while the patient is lying down. If this locking sensation is painful, the patient is advised to limit weightbearing and avoid the bothersome joint angle for an additional period. These symptoms usually dissipate within 3 months.

Typically, swelling and joint effusion (fluid in the joint) disappear within 8 weeks after a microfracture procedure. Occasionally, a recurrent effusion develops between 6 and 8 weeks after surgery for a defect on the femur; usually when a patient begins to put weight on the injured leg. This effusion may mimic the preoperative or immediate postoperative effusion, although it is usually painless. It usually resolves within several weeks. Rarely is a second arthroscopy required for recurring effusions.

The specific rehabilitation program for each patient following a microfracture will vary depending upon the following factors:

• The location of the defect
• The size of the defect
• Whether any other surgical procedure, such as an anterior cruciate ligament reconstruction, was done at the same time as microfracture.

Following are examples of some rehabilitation programs.

Rehabilitation Protocol for Patients with Chondral Defects on the Femur or Tibia

• The patient is started on a continuous passive motion (CPM) machine immediately in the recovery room. Ideally, the patient should use the machine for 6 to 8 hours every 24 hours. Range of motion is increased as tolerated until full range of motion is achieved with the machine.
• If a CPM machine is not used, the patient begins passive flexion/extension (straightening and bending) of the knee with 500 repetitions three times a day.
• The use of crutches, with only light touch-down weight allowed on the involved leg, is prescribed for 6 to 8 weeks. Patients with small defect areas (less than 1cm in diameter) may be allowed to put weight on the leg a few weeks sooner.
• Brace use is rarely recommended for patients with chondral defects on the femur or tibia.

Limited strength training also begins immediately after microfracture surgery.

• Standing one-third knee bends with a great deal of the weight on the uninjured leg begin the day after surgery.
• Stationary biking without resistance and a deep-water exercise program begin 1 to 2 weeks after surgery.
• After 8 weeks the patient progresses to full weight bearing and begins a more vigorous program of active knee motion.
• Elastic resistance cord exercises can begin about 8 weeks following surgery.
• Free weights or machine weights can be started when the early goals of the rehabilitation program have been met, but no sooner than 16 weeks after surgery.
• Patients must not resume sports that involve pivoting, cutting, and jumping for 4 to 6 months after a microfracture procedure. Full activity may be resumed once the physician has examined the knee and given approval for the patient to return to sports activity.

Rehabilitation Protocol for Patients with Patellofemoral Chondral Defects

• All patients treated with microfracture for patellofemoral defects must use a brace set for 0° to 20° of flexion for at least 8 weeks. It is essential to limit compression of the new surfaces in the early postoperative period, so that the maturing marrow clot will not be disturbed. The brace should be worn at all times except when passive motion is allowed.
• Patients are placed into a CPM machine immediately following surgery. The goal is to obtain a pain-free and full passive range of motion soon after surgery during those periods when the brace is removed.
• When the patient wears a brace, strength training is allowed, but only in the 0° to 20° range immediately after surgery in order to limit compression of the affected chondral surfaces. The joint angles of these patients are observed carefully at the time of surgery to determine where the defect makes contact with the opposing surface, either on the patella or on the trochlear groove of the femur. These areas are avoided during strength training for approximately 4 months.
• Patients are allowed to put weight on the involved leg as tolerated, but it must be limited to the angles of flexion that do not compress the treated surfaces. For this reason the patient must wear a brace locked in limited flexion.
• After 8 weeks, the knee brace is gradually opened to allow increased flexion of the knee, a process that takes about a month. Brace use is generally discontinued at about 12 weeks. Some patients, however, like to continue to wear the brace for strenuous exercise for a few more months up to about 6 months.
• After brace use is discontinued, strength training advances progressively.
• The doctor must examine the knee before the patient is released to full activity.