Two cell covers associated with similar short-term ACT results

Researchers reported few complications with either technique, but detected graft hypertrophy in 48% of grafts using periosteum.

BIRMINGHAM, England - The first prospective randomized study to compare autologous chondrocyte transplantation done using periosteum to cover the cultured cells with the same technique using a porcine collagen membrane to cover the cells showed comparable results at two years postop.

This suggests that patients with knee cartilage defects might eventually safely forego a separate surgical step to harvest the periosteum needed for autologous chondrocyte transplantation (ACT). Instead, a substitute off-the-shelf product might achieve similar clinical outcomes.

The investigators, from the Royal National Orthopaedic Hospital in Stanmore, England, said such a conclusion depended, however, on long-term outcomes from this particular application of the type I/III collagen membrane they studied [Matricel Collagen Matrix by Verigen; Leverkusen, Germany].

According to Chris R. Gooding, FRCS, who recently presented the results at the British Orthopaedic Association Annual Congress here, “Collagen-covered ACT compared favorably with periosteum-covered ACT after two years, based on both the clinical and arthroscopic data. Certainly more is known about the long-term follow-up of the periosteum-covered technique, and time will tell if the collagen-covered ACT technique can offer such a durable repair.”

George Bentley, ChM, FRCS, one of the senior surgeons with patients in the study, is a member of the Orthopaedics Today International Editorial Board.

Treating full-thickness grade 4 lesions

Most of the 68 lesions treated in the prospective study (33 in ACT cohort, 35 in collagen-covered ACC cohort) were on the medial femoral condyle, but there were also a couple of trochlear lesions as well. Most were full-thickness grade 4 lesions, Gooding said. The average size was about 5 cm² in the ACT group and a little smaller - about 4 cm² - in the ACC group.

In all cases surgeons first sutured the covering to the rim of the debrided defect and then injected the cultured chondrocytes beneath it. The patients in the ACT cohort received slightly longer incisions made to harvest the periosteum from either their proximal tibia or distal femur.

All patients received the same postoperative rehabilitation, which consisted of full weightbearing aided by crutches for the first 10 days, followed by a graduated rehab program.

Postoperative improvements

Clinical results were based on the modified Cincinnati Knee Rating System (80-100 excellent, 55-79 good, 30-54 fair, <30 poor). Those scores take into account factors like knee function, pain and effusion. At two years postop, the mean modified Cincinnati scores improved from preoperative levels of 38% in the ACT group and 49% in the ACC group.

“Surprisingly, there are no excellent outcomes [in the ACT] group,” Gooding said. Thirty-nine percent of ACT patients, however, had good scores, compared to 34% of ACC patients. “All of these patients complained of pain, since that is the main indication for chondrocyte transplantation.”

Investigators took arthroscopic biopsies at one-year postop and assessed them using the International Cartilage Repair Society system. “Based on this, 10% of patients for each of the techniques achieved excellent results; 17% had good results. There was one patient in each group who had a poor results,” he said. About half the patients underwent one-year arthroscopies.

Investigators noticed some defects in each group filled with hyaline-only, mixed hyaline-fibrocartilage, or fibrocartilage-only cartilage.

Sixteen patients in the ACT group experienced graft hypertrophy (48%), compared to four patients in the ACC group (11.4%). Shaving down the grafts was the best remedy for the pain and catching associated with the hypertrophy, according to Gooding, who added that there is some concern about the rate of graft hypertrophy with the periosteum technique requiring further surgery.

For more information:
Gooding CR, Bartlett W, Bentley G, et al. A prospective, randomized study comparing two techniques of autologous chondrocyte implantation for osteochondral defects in the knee: periosteum covered versus type I/III collagen covered. Presented at the British Orthopaedic Association Annual Congress. Sept. 20-23, 2005. Birmingham, England.