A Look Back at Long-Term Success For Knee Cartilage RepairBack in 1995 when surgeons first started using a technique called autologous chondrocyte implantation (ACI), a group of surgeons from around the United States set up a special study to track results of this treatment. They called the collection of data from patients at various clinics and surgical centers the Cartilage Repair Registry or Registry for short. The goal was to follow patients long enough to see how well this treatment worked over time.
Autologous chondrocyte implantation (ACI) refers to the filling in of cracks and holes in the knee joint cartilage with the patient's own chondrocytes (cartilage cells). These lesions or defects occur as a result of trauma, injury, or repetitive damage to the joint. Autologous means that normal, healthy cartilage cells are taken from a place in the patient's own knee joint. The cells come from an area that isn't damaged and doesn't bear a huge load when the person is upright and weight-bearing. The harvested chondrocytes have the advantage of being accepted (not rejected) by the patient's body.
Five years ago, results from the registry were reported. An area of key interest was the durability of the implantation. At that time, results were good-to-excellent for the majority (80 per cent) of patients. There was even evidence that as time went by in the early years, patients continued to improve. Now the researchers present results after 10 years. They used the outcomes after five years and compared it with the results after 10 years to assess durability.
They didn't just look at how well the implant held up. They also evaluated knee alignment, stability of the ligaments, and patellar tracking (knee cap moving up and down over the knee). They collected data on patients' ages, sex (male or female), height and weight, size and location of the defect or lesion, and history of any previous knee surgeries. The data was analyzed in a number of ways trying to see if any one of these factors or variables could be linked with success or failure.
Success was defined as a confirmed defect filling, patient satisfaction with results, and no need for further treatment for the problem. Failure was determined as the need to remove the graft for any reason, the need for partial or complete joint replacement, and failure of the defect to fill in (seen on imaging studies). Most of the failures (17 per cent) occurred early on (in the first two and a half years)
Looking at patient characteristics, it turns out that most of the patients had normal knee (including knee cap) alignment before surgery. Three-fourths of the patients who ended up with autologous chondrocyte implantation (ACI) had at least one previous knee surgery (e.g., arthroscopy, debridement, meniscal repair or removal). One-fifth of the group didn't just have an ACI procedure but also had some other procedure to improve knee alignment or repair a torn or ruptured ligament.
As far as the cartilage lesion goes, two-thirds of the patients had a sudden or acute onset of the injury. Most of the defects were located on the medial (inner aspect) on the round end of the femur (thigh bone) where it meets the tibia (lower leg bone) to form the knee joint. This is an area that takes a lot of use and abuse during weight-bearing and knee motion.
Those who improved in the first five years stayed that way -- they didn't get better or worse. The authors take this to mean that early improvement after autologous chondrocyte implantation is maintained years later. There was no indication that age, gender, lesion size, patient size (height and weight), or other knee surgeries had any effect on the final results. That's good but what did cause those patients who had a poor outcome to fail the treatment?
Problems with knee alignment that was never corrected heads the list as possible factors linked with failure. Larger-sized defects (more than four centimeters in width and length) seemed more likely to fail. Since this is a new procedure, a lack of experience on the part of the surgeon might be a variable. Over time, statistical analysis will be able to factor for that more directly.
The authors conclude that autologous chondrocyte implantation (ACI) is a successful procedure for full-thickness (clear to the bone) holes in the articular cartilage of the knee. Pain, swelling, and knee function can be resolved in most patients who are carefully selected for this procedure. The results occur early and last up to 10 years, which is considered long-term. There are only two published studies with long-term data of this kind -- this is one of them! So you can see there's room for more results to be reported from other studies.
J. Bruce Moseley, Jr., et al. Long-Term Durability of Autologous Chondrocyte Implantation. In The American Journal of Sports Medicine. February 2010. Vol. 38. No. 2. Pp. 238-246.
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