Experimental evaluation of the development mechanism of the compression fractures at adjacent segment disease

Fusion has been the standard method in the treatment of spinal disorders in past few decades. Although the fusion has demonstrated good clinical results in early period, it has been thought to cause adjacent segment disease in long term period. Degeneration occurred at adjacent mobile segments above or below fusion is called as adjacent segment disease. Despite that exact mechanism of adjacent segment disease is not known, it is thought that changed biomechanical forces play key role. Adjacent segment disease generally necessitates a second operation. Compression fracture occurs through severe compressive loads acting on spine. It generally occurs in incidence of trauma or traffic accidents. Within the scope of this thesis, the compression fracture at adjacent segment after trauma was experimentally evaluated on ovine vertebrae fixed with rigid, dynamic, and semi-rigid fixations. A free fall drop system was designed and manufactured. Specific weights were dropped to test samples, and compression fractures at adjacent segments were evaluated. Radiography of test samples were taken before and after drop test, and occurrence of compression fractures was observed with comparison of the radiographies. Additionally, rigidity of each fixation systems in compression bending, lateral bending, and torsion tests was determined. Static tests showed that rigid fixation has significantly higher stiffness values than dynamic and semi-rigid fixations. Drop tests showed that epiphysis fractures occurred at fixed and adjacent mobile segments of vertebrae which were fixed with semi-rigid fixation after drop. Additionally, dynamic fixation well preserved the fixed and adjacent mobile segments of vertebrae during drop.