ACI performed with type I/III collagen membrane shows good 3-year results

At final follow-up, only two patients showed minimal graft hypertrophy, although neither had associated clinical symptoms.

Using a type I/III collagen membrane during autologous chondrocyte implantation can effectively treat isolated knee cartilage defects and may help prevent the development of graft hypertrophy, according to a prospective study by German researchers.

Matthias Steinwachs, PhD, and colleague Peter C. Kreuz, MD, of the University Medical Center Freiburg, evaluated their results performing the procedure in 63 patients treated for traumatic chondral lesions at a mean age of 34 years. All patients had isolated grade 3 or grade 4 chondral defects at least 2 cm² and averaging 5.85 cm², according to the study, published in Arthroscopy.

In all cases, the surgeon performed autologous chondrocyte implantation (ACI) using a bilayer porcine collagen type I/III membrane [Chondro-Gide; Geistlich Biomaterials] to cover the chondrocyte suspension [ARTROcell; Metreon Bioproduct GmbH] instead of a periosteal graft, the authors noted.

"The membrane is degraded by enzymatic digestion and has two different surfaces: The external has good mechanical strength and serves as a barrier, whereas the inner surface is porous and stimulates the cells to produce cartilage-specific matrix molecules," they wrote.

After surgery, knees were elevated for 12 hours to ensure cell adhesion and then began 6 to 8 hours of continuous passive motion daily, according to the study.

Preoperatively, all patients had either a poor or fair modified Cincinnati score, and either an abnormal or severely abnormal International Cartilage Repair Society (ICRS) score. At 36 months follow-up, all patients had significant improvements in these scores, with 87% having either good or excellent results, and 85% rated as either normal or nearly normal, the authors reported.

Final outcomes were independent of the location of the defect, they noted.

Over the course of follow-up, MRIs showed significant improvements in defect filling, subchondral edema, cartilage signal and effusion. After 36 months, only two patients with patellar defects showed minimal graft hypertrophy. "However, the hypertrophic changes were not associated with clinical symptoms," the authors wrote.

Three patients required revision surgery due to incomplete filling of their defects and clinical symptoms, two of whom had suffered a fall between 3 and 6 weeks postop. Surgeons treated these two patients with a repeat ACI procedure. The third patient received a periosteal patch to cover the chondrocyte suspension.

"All patients recovered after revision surgery and could perform their activities of daily life including sports," the authors wrote.

For more information:
Steinwachs M, Kreuz PC. Autologous chondrocyte implantation in chondral defects of the knee with a type I/III collagen membrane: A prospective study with a 3-year follow-up. Arthroscopy. 2007;23:381-387.