Arthroscopic fixation of matrix-associated autologous chondrocyte implantation: importance of fixation pin angle on joint compression forces.

PURPOSE: The aim of the study was to investigate the effect of pin fixation perpendicular and 30° tilted to the matrix surface on the joint compression forces. METHODS: In a porcine knee model, joint compression forces were recorded with a digital pressure sensor above the medial meniscus and with axial compression of 100 N by use of a material testing machine. The forces were recorded for an intact femoral condyle, as well as a standardized cartilage defect of 25 × 20 mm, after matrix-associated autologous chondrocyte implantation (m-ACI) (BioSeed C; Biotissue Technologies, Freiburg, Germany), fixed by use of a conventional suture technique and pin fixation with a biodegradable pin perpendicular and 30° tilted to the matrix surface. RESULTS: In knees with cartilage defects, the peak compression forces (mean, 824 kPa) were significantly increased compared with the intact knee joint (564 kPa). After m-ACI implantation with a chondral suture (581.3 kPa) and perpendicular pin fixation, the joint compression forces of the cartilage defect were significantly decreased (630.7 kPa). There were no significant differences compared with the intact knee. After 30° tilted pin insertion, mean joint compression forces were significantly increased (1,740 kPa). CONCLUSIONS: This study shows that after chondral suture and perpendicular pin fixation, there are no increased compression forces in the knee joint in comparison to an intact knee. Thirty degree tilted pin insertion contributes to increased joint compression forces. CLINICAL RELEVANCE: A tilted insertion during pin fixation in m-ACI should be avoided because it may lead to increased joint compression forces, especially after cartilage defect lesions on the tibial side.

Arthroscopic implantation of a three dimensional scaffold for autologous chondrocyte transplantation.

The arthroscopic M-ACT technique is applicable for defects at the femoral condyle up to 5 cm(2). The size of the defect has to be assessed with a specific scaled, percutaneously inserted needle. Then an 8 mm water-stop-cannula is positioned in a suprameniscal portal. The chondrocyte seeded matrix is trimmed to size the defect. The scaffold is introduced in the joint through the cannula and placed into the defect with a blunt arthroscopic grasp instrument to prevent damage of the scaffold. Then a specific drill guide is inserted through an additional anteromedial portal to place it on the scaffold in a perpendicular angle. The position of the drill guide should not be changed during the next two steps. It may be helpful to hold the matrix in place with a probe inserted through the cannula. A 1.5 mm K-wire is drilled at least 16 mm into the subchondral bone. Then the biodegradable pin (length 16 mm) is placed in the drill guide and carefully hammered into the subchondral bone. The joint is flexed so that the drill guide can be placed on the posterior end of the scaffold. Another hole is drilled with the K-wire and a second pin is inserted. Finally the stability of the matrix is tested with a probe and the joint is mobilized.

Arthroscopic techniques for the fixation of a three-dimensional scaffold for autologous chondrocyte transplantation: structural properties in an in vitro model.

PURPOSE: The aim of the present study was to evaluate the structural properties of matrix-associated autologous chondrocyte implantation with multiple fixation techniques implanted in fresh porcine knees after they had undergone load to failure. METHODS: We evaluated the ultimate failure load, yield load, and stiffness of 3 different techniques for the fixation of a 2-mm thick polymer fleece: (1) fixation with biodegradable polylevolactide pins, (2) a transosseous anchoring technique, and (3) conventional suture fixation. Techniques 1 (pin) and 2 (transosseous anchoring) can be used arthroscopically. RESULTS: Maximum load and yield load were significantly higher in the group 1 (pin fixation) and group 2 (transosseous anchoring) compared to group 3 (conventional suture). Stiffness was significantly higher in group 1 than in groups 2 or 3. CONCLUSIONS: Our biomechanical data show that two fixation techniques (pin fixation and transosseous anchoring) have a higher ultimate load, yield load, and stiffness than the conventional suture technique at time point zero. However, these data can be interpreted only with the Bioceed-C matrix (BioTissue Technologies GmbH, Freiburg, Germany). CLINICAL RELEVANCE: Our biomechanical data show outstanding fixation strength with arthroscopic techniques that use Bioceed-C matrix scaffolds during autologous chondrocyte transplantation. Thus, arthroscopic fixation done with this biomaterial should benefit patients, which, in turn, should lead to further research on these arthroscopic techniques and this biomaterial.