Five-year data show no difference between ACI and microfracture

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A long-term evaluation of autologous chondrocyte implantation and the microfracture technique has revealed no significant differences between the two cartilage repair modalities.

The report, presented at the 6th Symposium of the International Cartilage Repair Society (ICRS) continued the follow-up of data of the randomized controlled trial originally published in the Journal of Bone and Joint Surgery in 2004.

Lead author and presenter, Gunnar Knutsen, MD, of the department of orthopedic surgery at University Hospital Tromsø, Norway, said, “At five years there was no significant difference [between the two groups]. Nine failures occurred in both groups.”

He said that there were no significant differences between microscopic or histological results of the two techniques, and no correlation between histology and clinical outcomes. “We believe that we have to report the results at 10 years,” he said.

Head-to-head comparison

Knutsen believes the study is the only randomized, controlled, head-to-head comparison of the two articular cartilage-growing methods.

The evaluation follows 80 patients who received either ACI with harvested autologous chondrocytes that had been expanded in the laboratory and microfracture, which involves the disruption of the subchondral bone to produce a fibrin clot laden with pluripotential cells and eventual fibrocartilaginous repair tissue.

Significant improvement

Knutsen reported that at both the two- and five-year follow-ups, both groups displayed significant clinical improvement. Researchers collected data through ICRS, Tenger, Lysholm and SF-36 scores. Second look arthroscopy and biopsies were performed prior to the publication of the two-year data.

At the two-year follow-up, two ACI patients and one microfracture patient had failures. By the five-year evaluation, nine patients in each group had failures.

“There was a tendency to see failures a little bit earlier in the ACI group, but that is not significant,” Knutsen said. “One ACI patient and one microfracture patient went on to need a total knee replacement. The survival curve at 60 months was 78%.”

The microfracture group posted higher scores in the SF-36 physical component at two years, but that did not hold up over time. “Looking at the SF-36, there were no differences between the ACI and microfracture groups,” Knutsen said. “Though it is not significant, there seemed to be slightly better results for the microfracture at two years and we had a significantly better result, for the microfracture group, but at five years, that is not the case.”

Knutsen said that the younger patients in both groups had significantly better results. More active patients in both groups also had significantly better scores.

At the two-year point, they took biopsy evaluations on 84% of the study population. Although no significant differences were seen between the groups, Knutsen noted a tendency to see better hyaline repair from ACI; however, it was not significant in the number of subjects available.

For more information:
Knutsen G. Drogset JO. Engebretsen L. et al. Autologous chondrocyte implantation compared with microfracture in the knee (five-year follow-up). #1-3. Presented at the 6th Symposium of the International Cartilage Repair Society. Jan. 8-11, 2006. San Diego.