Assessment for the stability of fracture thoracic lumber spine(T11~L3) fixed with crossbar equipped pedicle screws / 医用生物力学

ABSTRACT

Objective To determine the stability of fracture thoracic lumber spine (T11~L3) fixed with crossbar equipped pedicle screws. MethodThe thoracic lumber spine segments (T11~L3) were obtained from calves. A wedge cut was performed on L1 vertebral body to produce a model resembling severe vertebral compressive fracture. Some of the fracture spine segments were fixed with pedicle screws with and without crossbar. Thus, 4 types of spine segments were available (1) normal segments; (2) unfixed fracture; (3) fracture fixed with crossbar equipped pedicle screws and (4) fracture fixed with pedicle screws without crossbar. The segmental stability was determined by measuring the range of motion (ROM) at directions of flexion/extension, left/right axial rotation and left/right lateral bending using a three dimensional laser scanner. Each ROM was standardized into a stability potential index (SPI) for the comparison among 4 groups. ResultsCompared to unfixed fracture, both fixations significantly increase stability of injuried specimens at each motion direction. The stability of injured segment fix with crossbar equipped pedicle screws is higher than that fixed without crossbar, but the difference does not reach statistically significant. ConclusionsPedicle screw fixation can significantly increase the stability of fracture spine. However, crossbar may not play a further role in raising fixative stability.