Rehab After Autologous Chondrocyte Implantation

Autologous chondrocyte implantation (ACI) is a way to surgically treat full-thickness tears of the knee joint cartilage. Knee function can be restored or improved with this procedure, especially for athletes who might otherwise be out of the game. Normal cartilage cells are taken from the patient and grown in a laboratory setting. When the cells have multiplied by 20 to 30 times, then they can be reimplanted into the damaged area. Healing and remodeling of the articular cartilage occur over a period of weeks to months. In this article, physical therapists at the University of Colorado Health Sciences Center (UCHSC) present their rehab protocol for this procedure. They provide a review of the technique and results from other studies. There's no proof that this technique works better than other methods such as microfracture. Overall, the results have been good to excellent. Proper rehabilitation is important to promote healing and prevent damage to the implantation. Overload and shear forces can damage the new tissue if they occur too soon in the postoperative period. The UCHSC protocol is similar to programs used at other institutions. One difference may be that the patient is not allowed to put any weight on the knee for the first six weeks. This is especially important for patients whose lesion comes in contact with the other side of the joint at the point of near knee extension. Goals and steps in the rehab process are outlined through four phases including:

Early protection phase (weeks 0-6 weeks)

Transition phase (weeks 6-12)

Remodeling phase (weeks 12-26)

Maturation phase (weeks 26-52) The authors provide a complete table listing the specific timeline for each phase. Weight bearing, use of a brace, range of motion, strengthening, and functional activities are outlined. Specific changes for each of these areas are listed as the patient progresses from phase to phase. Some variations can occur in the steps and timeframe of the phases. Patients with other damage to the knee such as multiple cartilage lesions or an anterior cruciate ligament tear (ACL) may require a slower progression of weight bearing activities. Under these circumstances, some motions may have to be avoided for much longer. There are other factors that must be considered. How quickly a patient can progress through the rehab protocol may depend on their overall health, body mass index (BMI), and age. Activity level before injury, specific goals after injury, and level of motivation and compliance are equally important. The full and complete healing process can take up to two years or more. Fully healed tissue is never quite as stiff as normal, uninjured cartilage but it comes close.

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