gms | German Medical Science

Objectives: In recent years the subchondral bone and its importance for a successful regenerative therapy of osteochondral lesions and the articular surface unit in the knee came into focus, as severe symptomatic and unstable osteochondral defects of large size and depth are difficult to treat. A new technique described by Angele et al uses an autologous bicortical bone graft from the iliac crest for bone augmentation of large osteochondral lesion showing good clinical and radiological results. Although the reconstruction of the subchondral plate seems to be mandatory for a successful treatment of deep osteochondral defects there is still a lack of biomechanical and histological understanding of this new technique and if this technique restores the original subchondral zone efficiently.

Aim: The aim of this study was to analyse the ability to restore the physiological subchondral zone with the bone block technique taken from the iliac crest.

Material and Methods: The experiments were performed using 6 lateral femur condyles and 6 iliac crest bone grafts from the same cadaver preserved with the method of Thiel. Six matched pairs of human cadaver femur condyles and iliac crest grafts were used to get an intra-individual comparison. CT-scans were made to evaluate any bony crack or pathology. For each pair of specimen three kinds of tests were conducted. In a first test series, the iliac crest was tested in medial lateral direction so that the medial cortical layer (inner zone of the iliac crest) was penetrated. After that, the femur condyles were tested with their intact cartilage layer following the same testing procedure. Finally, the cartilage layer was removed by one experienced surgeon with a scalpel. In a static compression test using an electro dynamic testing machine (Instron, E3000, High Wycombe, UK) the maximal strength in Newtons (N) and the failure behavior were analysed.

Results and Conclusion: Concerning failure load, no statistical significant difference could be found for samples of the iliac crest and femur condyles having their cartilage removed (p=0,312). The femur condyle that still had an intact cartilage layer shows statistical higher loads compared to the iliac crest samples (p<0,001).The failure load of the iliac crest samples ranges from 53.3N to 180.5N. Specimen from the femur condyle that still had an intact cartilage layer showed failure loads between 118.3N to 260.4N. Removing the cartilage layer of the femur condyles leads to a reduction of the failure load of about 20% to 80% (38,5N to 175,1 N).

Conclusion: This study shows that under biomechanical aspect the bone block technique from the iliac crest for bone augmentation of large osteochondral lesion in allows efficiently restoration of the subchondral zone for bone augmentation of large osteochondral lesions.