Introduction: Homogenous cell distribution and suffi-cient initial scaffold stability remain key issues for successful tissue engineered osteochondral constructs. The purpose of this study was to investigate the application of initial compression forces during the first 24 hours of cell culture followed by different stress patterns.

Methods: Bone marrow stromal cells were harvested from the iliac crest during routine trauma surgery. The cells were expanded in a 2-dimensional culture and then seeded into the biologic hybrid scaffold with a concentration of 1x10E6 cells per ml. Pressure and vacuum forces were applied in a specially developed glass kit. The constructs were exposed to two different protocols of compression combined as oteochondral matrices of CaReS (collagen I) and Tutobone (Ars Arthro, Esslingen, Germany and Tutogen Medical GmbH, Neunkirchen a. Br., Germany). Controls were resected osteochondral fragments from patients with articular fractures and uncompressed constructs. These effects were evaluated using light microscopy after standard staining to identify matrix penetration. Biomechanical tests were conducted, too using a modified biomechanical testing machine. The ‘constrained compression’, maximum load to failure, modulus, and strain energy density were determined.

Results: Histology: Penetration and cell distribution was demonstrated homogenous and vital, respectively. Mechanical tests showed a significant enhancement of primary matrix stability. The following stress patterns did not enhance significantly stability over seven days.

Discussion: The aim of this project was to investigate the response and cell distrubution of human bone marrow stromal cells seeded on a 3-dimensional biologic hybrid scaffold using compression and vacuum forces.

The integration of mechanical stimulation in the tissue engineering process may lead to a progress in the structural and biomechanical properties of these tissues and offers new possibilities in the management of bone injuries and degenerative diseases.

We assessed proprioception in the knee using the angle reproduction test in 20 healthy volunteers, ten patients with acute anterior instability and 20 patients with chronic anterior instability after reconstruction of the anterior cruciate ligament (ACL). In addition, the Lysholm-knee score, ligament laxity and patient satisfaction were determined.

Acute trauma causes extensive damage to proprioception which is not restored by rehabilitation alone. Three months after operation, there remained a slight decrease in proprioception compared with the preoperative recordings, but six months after reconstruction, restoration of proprioception was seen near full extension and full flexion. In the mid-range position, proprioception was not restored. At follow-up, 3.7 ± 0.3 years after reconstruction, there was further improvement of proprioception in the mid-range position. There was no difference between open and arthroscopic techniques. The highest correlation was found between proprioception and patient satisfaction. After reconstruction of the ACL reduced proprioception may explain the poor functional outcome in some patients, despite restoration of mechanical stability.