ACI effective in 80% of chondral defects at two years

Study provides external confirmation of previous outcomes reported by the technique’s originators.

Autologous chondrocyte implantation produced good to excellent results in most patients with chondral defects, according to a study by British researchers.

Abhijit M. Bhosale, MS (Orth), MRCS, an orthopedist in training at the Robert Jones and Agnes Hunt Orthopaedic Hospital in Shropshire, England, conducted the study with James Richardson, FRCS(Orth), and colleagues at the center. The researchers found that at two years’ follow-up, 80% of patients achieved good to excellent results, and continued to show improvement.

The surgical team has treated over 250 patients with autologous chondrocyte implantation (ACI) since 1997 using cells grown in the hospital’s own OsCell GMP cell culture facility. In the study, researchers analyzed the results for their first 118 consecutive patients treated for a total of 149 symptomatic chondral defects. Bhosale presented the results at the 6th Symposium of the International Cartilage Repair Society.

The researchers found that the mean Lysholm score improved from 50 at preop to 70 at one-year follow-up. Histology results also demonstrated good quality mixed fibro-hyaline or fibrocartilage of reasonable functional thickness.

“The increase in the Lysholm score at one year was identical [regardless of] whether the defect was isolated in the femoral condyle or [whether] the patients had multiple defects,” Bhosale said.

MRI scans showed some regions of low-signal intensity within treated areas, although the researchers found no correlation between MRI findings and histological features, Bhosale told Orthopedics Today.

Two-stage procedure

Patients included in the study had a mean age of 35 years; 80% were men and 60% had defects in their right knee. Of the 149 total defects, 45% were located on the medial femoral condyle, 22% on the lateral femoral condyle and 21% were classified as multi-defects. The remaining 12% involved isolated defects in the femoral trochlea.

The ACI procedures involved two surgical phases. First, surgeons arthroscopically harvested cartilage. After three weeks, surgeons then performed an open arthrotomy and covered the defect using either periosteum (94% of cases) or a porcine membrane (Chondro-Gide, Geistlich Biomaterials; 6% of cases).

The chondrocyte suspensions were injected under the patches, Bhosale said.

Following surgery, patients were splinted for six hours postoperatively before initiating continuous passive motion treatment. The rehabilitation program involved use of an AVI (Novamedix) foot pump for six weeks to avoid deep vein thrombosis.

Depending on defect location, surgeons allowed patients to return to either partial or full weight-bearing. “The patient goes on to gradually increased activity for six months and usually resumed contact sports at 12 months,” Bhosale said.

Peak scores at two years

Using a cubic model with random intercept, researchers found statistically significant improvements at one year. Patients achieved peak improvement at two years’ follow-up, with scores remaining stable thereafter.

At two years, 80% of patients achieved good to excellent results. The remaining 20% had poor knee scores at two years, which they subsequently maintained throughout continued follow-up, according to Bhosale.

“Though there was another small increase in scores between one and two years, which was statistically significant, the scores then evened out after two years, indicating that the two-year score is the most important,” Bhosale said.

The results suggest that histological studies and MRI scans performed at two years may capture the best repair results and be more predictive of long-term outcome, Bhosale added.

Randomized trial needed

The researchers based their study on a study from 2000 by Petersen et al — originators of the technique — that presented results at two- to nine-year follow-up. “[That study] gave a new dimension to the treatment options for chondral defects, with 85% good to excellent results and a long-term clinical outcome of up to 11 years,” Bhosale said.

The current study, which found 80% of patients having good to excellent results, provides external confirmation of the outcomes reported by the technique’s originators. Some differences in outcomes may reflect variations in patient selection and subsequent activity levels, Bhosale noted.

“The ‘missing link’ in ACI studies is a large, multicenter, randomized trial comparing ACI to other treatments for chondral defects,” Bhosale told Orthopedics Today. He noted that a new trial has commenced with support of the British MRC. The study, called ACTIVE, involves 12 centers in the U.K. and Norway and will follow patients over 10 years.

For more information:
Bhosale A, Harrison P, Ashton BA, et al. Autologous chondrocyte implantation: 2-to-9-year Oscell experience. #10c-1. Presented at the 6th Symposium of the International Cartilage Repair Society. Jan. 8-11, 2006. San Diego.
Peterson L, Minas T, Brittberg M, et al. Two- to 9-year outcome after autologous chondrocyte transplantation of the knee. Clin Orthop. 2000;374:212-234.