A three-dimensional hyaluronan-based scaffold seeded with cultured autologous chondrocytes is shown here. A piece of foil from suture materials, which is removed prior to implantation, is attached for measurement purposes.
Courtesy of Christoph Becher, MD

AAOS Now

Published 5/1/2008
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Jennie McKee

MACT shows promise in repairing osteochondral defects of the talus

Study finds good-to-excellent clinical results after failed primary surgical treatment

If traditional surgical treatments fail to repair articular cartilage lesions of the talus, what other surgical procedures might be effective? According to Christoph Becher, MD, a presenter at the American Orthopaedic Foot and Ankle Society’s 2008 Specialty Day, matrix-associated autologous chondrocyte transplantation (MACT) is a valid option.

Dr. Becher, of the department of orthopaedic surgery at Hannover Medical School in Hannover, Germany, supported this assertion by discussing a prospective study that evaluated the early clinical and magnetic resonance imaging (MRI) results of patients treated with MACT.

Using MACT to heal cartilage
The study was conducted by Dr. Becher, lead researcher Hajo Thermann, MD, PhD, and Klaus-Peter Kammerer, MD at the Center for Knee and Foot Surgery, ATOS Clinic, in Heidelberg, Germany. Nine patients (five women and four men), whose average age at surgery was 28 years (range: 17 to 43 years old), were treated with laboratory-expanded autologous chondrocytes grown on a three-dimensional hyaluronan-based scaffold. These patients had previously undergone surgical procedures that included débridement (2); anterograde (3) or retrograde (1) drilling; microfracture (1); and cancellous bone grafting (2).

“The main advantages of using a seeded scaffold, as opposed to first-generation ACT with a periosteal flap, include easy fixation, less implantation-related morbidity, and improved proliferative activity of cultured chondrocytes,” explained Dr. Becher.

The defect was located on the medial side in all patients. For eight of the patients, the physicians performed medial malleolar osteotomies to approach the defect; a mini-arthrotomy was used in one patient.

Measuring the results
Researchers evaluated the results using the Hannover Scoring System and the Visual Analog Score (VAS: 0 = very poor, 10 = excellent). Patients completed one preoperative evaluation and at least two postoperative evaluations. Mean follow-up was 3.7 years.

Guided by previously established parameters for monitoring articular cartilage repair following MACT, the researchers used MRI to evaluate the degree of defect repair and filling of the defect, integration to border zone, surface of the repair tissue, structure of the repair tissue, and subchondral bone alterations. In seven patients, researchers were able to perform a second-look arthroscopy when they removed the osteotomy screws.

The grafted area was assigned an International Cartilage Repair Society Cartilage Repair Assessment Score (ICRS-CRAS). In addition, statistical analysis was performed using the Wilcoxon sign rank sum test with a level of significance of p<0.05.>

Reliable, but not always homogeneous
Following the MACT treatment, patients showed a marked improvement in several areas. Results on the Hannover Scoring System were excellent for two patients and good for the remaining seven patients. VAS pain scores improved from 2.97 preoperatively to 8.15 postoperatively (p<0.001), function scores went from 3.44 to 7.20 (p><0.001), and satisfaction scores increased from 1.85 to 7.53 (p><0.001).>

According to the ICRS-CRAS, all of the transplanted areas were rated nearly normal (Grade II). In MRI follow-up examinations, researchers found that the defect was completely filled in six patients; they also noted graft hypertrophy in one patient, and incomplete filling (>50 percent of adjacent cartilage) in two patients. Integration to the border zone was complete in six patients; a demarcation border (split-like) was seen in three patients.

A damaged surface that had fibrillations, fissures, or ulcerations and an irregular internal structure were found in six patients; three patients had intact surfaces and structures. Four patients had intact subchondral bones; in three patients, researchers found subchondral edema-like signal alterations. Two patients had a cyst or granulation tissue.

“From these results,” said Dr. Becher, “we can conclude that MACT is a reliable method for treating articular cartilage defects of the talus. Even though homogeneous coverage of the defect with normal articular cartilage was not achieved, the study had consistent findings at follow-up with no poor results. We know from other studies that imaging results have no or little correlation with the clinical results after cartilage repair.

“The question of whether MACT should be used in primary cases remains unanswered,” continued Dr. Becher. Potential advantages of using MACT might include improved clinical results and the restoration of repair tissue that has superior biomechanical and histologic qualities. In addition, MACT may help to impede the potential development of osteoarthritis.

“To really know what’s best for the patient,” he concluded, “prospective, randomized trials must be performed.”

For more information about monitoring articular cartilage repair after matrix-associated autologous chondrocyte implantation, see the study by Trattnig S, Ba-Ssalamah A, Pinker K, Plank C, Vecsei V, Marlovits S: Matrix-based autologous chondrocyte implantation for cartilage repair: Noninvasive monitoring by high-resolution magnetic resonance imaging. Magn Reson Imaging 2005;23:779-787.

Disclosure information for the authors can be found at www.aaos.org/disclosure

Jennie McKee is a staff writer for AAOS Now. She can be reached at mckee@aaos.org