[Treatment of deep cartilage defects of the knee with autologous chondrocyte transplantation on a hyaluronic Acid ester scaffolds (Hyalograft C)].

PURPOSE OF THE STUDY: The treatment of chondral defects by transplantation of autologous chondrocytes has recently shown further development. Various biomaterials are used as carriers facilitating attachment and even distribution of chondrocytes in the defect. Since 2003 Hyalograft C, hyaluronan-based scaffolds, has been used, in a clinical study, for implantation of autologous chondrocytes in the treatment of deep chondral lesions of the knee at our department.

MATERIAL: Eight patients (7 men and 1 woman; average age, 31 years) followed up for at least 9 months were evaluated. The lesions with an average size of 3.9 cm2 were localized on femoral condyles.

METHODS: The outcome of surgery was evaluated on the basis of the IKDC Subjective Knee Evaluation Form, Knee Injury and Osteoarthritis Outcome Score (KOOS) and Lysholm knee score. The patients underwent MR examination preoperatively and at 3, 6 and 12 months after surgery. The newly-formed cartilage was assessed by International Cartilage Repair Society (ICRS) visual scores at second-look arthroscopy carried out at 9 to 12 months following transplantation. Consistency of the new cartilage developing in the defect and that of healthy cartilage around the defect was compared by means of a special indentation probe in three patients. A biopsy sample was collected from the grafted site for histological, histochemical and immunohistochemical examination.

RESULTS: All patients reported improvement in knee function on average at 10 months after surgery. The average IKDC subjective score increased from 46 points preoperatively to 74 points postoperatively. The KOOS evaluation showed pain relief and improved function. In quality of life evaluation the average score of 35 points before surgery increased to 70 points after it. The average Lysholm knee score was 61 points before and 83 points after surgery. MR findings correlated well with arthroscopic findings. Second-look arthroscopy showed a normal appearance of the newly-formed cartilage in six, and an abnormal appearance in two patients. The average ICRS visual score was 9.4 points. No graft failure was recorded. The newly-produced tissue had the histological characteristics of a mixed hyaline and fibrous cartilage in seven patients, and of hyaline-like cartilage in one patient.

DISCUSSION: The ICRS visual repair assessment of the newly-formed tissue showed that our results were better than the one-year outcomes reported by Bartlett et al. (11 patients after transplantation of a collagen bilayer seeded with chondrocytes), but worse than the results of an Italian multi-center study (55 patients with Hyalograft C-based grafts followed up on average for 14 months). At almost one year, implantation of on a Hyalograft C resulted in the production of mixed cartilage incorporated well in the subchondral bone. Only one patient had mature hyaline cartilage. One year is too short to allow for complete remodeling of the newly formed cartilage into a mature hyaline cartilage. This is in agreement with other studies suggesting that the new cartilage continues to mature and remodel for a time longer than one year.

CONCLUSIONS: Based on our results we suggest that the use of Hyalograft C is a safe and effective option for treatment of deep chondral defects of the knee; it is particularly useful in patients in whom the primary defect treatment has failed. The application of Haylograft C is relatively quick and easy; this is convenient when surgery involves more than one procedure (ligament reconstruction, osteotomy). However, a definite evaluation of this method will be possible only after long-term results are available. Key words: deep cartilage defects, chondral defects, cartilage repair, autologous chondrocyte transplantation, hyaluronan- based scaffold, Hyalograft C, cartilage repair assessment, ICRS.