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No Significant Differences Noted Between Autologous Chondrocyte Implantation with Microfracture

Patients who have a cartilage defect in the knee often undergo correction with either autologous chondrocyte transplantation (ACI) or microfracture. With ACI, cells from the patient's own cartilage are collected to produce a culture of cartilage cells, which are collected and regenerated for implantation into the cartilage surface. With microfracture, tiny holes are made in the patient's bone, next to the cartilage defect. Bone marrow seeps out of the holes and creates a blood clot. Cartilage-building cells are then created.

The authors of this study investigated which procedure would produce better results 5 years after surgery. These findings follow 80 patients, 40 treated with microfracture, 40 with ACI. The patients' cartilage defects were due to trauma (65 percent), osteochondritis dissecans (28 percent), unknown for the rest. The average time since injury had been 36 months and 93 percent of the patients had already had knee surgery before participating in the study.

All patients were available for the 5-year follow up, although some could only participate by questionnaire through the mail or by telephone. The researchers found that 9 patients' procedures were failures in either group, occurring on average around 26 months after ATC and 39 months after microfracture. One patient in each group in the failure group had a knee replacement. The rest of the patients underwent new cartilage-resurfacing.

The remainder of the patients were assessed with the visual analog pain scale. The majority of patients (72 percent) had less pain compared with before surgery. The majority also reported improvement in range of motion and activity, in both groups. This differs from the 2-year follow up when the microfracture group showed significantly more improvement in some areas than did the ACI group.

At the 2-year follow up, the researchers obtained biopsies from 67 participants. The results showed no significant differences between the two groups in terms of the make-up of the healing tissues.

The authors point out some limitations of the study. These include the inability of the researchers to verify patient compliance with rehabilitation and the lack of a control group.

The failure rate of both procedures appears to be in line with that found in previous studies. While both procedures seem to have the same results, the ACI procedure does involve two steps, the removal of the cells and the re-implantation. The authors conclude that long-term follow up is still needed to determine if one method is superior than the other.

References: Gunnar Knutsen, MD, et al. A Randomized Trial Comparing Autologous Chondrocyte Implantation with Microfracture. In The Journal of Bone and Joint Surgery. October 2007. Vol. 89A. No. 10. Pp. 2105-2112.

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