RESUMEN
BACKGROUND: Spinal lamina reimplantation assisted hollow screw laminoplasty has achieved good clinical efficacy. The search literature found that there is no research at home and abroad on the biomechanical properties of unilateral and bilateral hollow screw fixation. OBJECTIVE: To evaluate the biomechanical property of different fixation with hollow screws in artificial and goat vertebrate laminoplasty. METHODS: A laminoplasty was conducted by using hollow screws. Based on the artificial vertebrate laminoplasty model, new models were generated by simulating unilateral screws fixation with a depth of screw insertion 5 mm (A group), unilateral screw fixation with a depth of screw insertion 8 mm (B group) and bilateral screw fixation with a depth of screw insertion 5 mm (C group). Based on the goat vertebrate laminoplasty model, new models were generated by simulating unilateral screws fixation (A group) and bilateral screw fixation (B group). The pull-out strength and static pressure were tested in the biomechanical testing machine with a sensor. RESULTS AND CONCLUSION: (1) In the artificial vertebrate model, the average pull-out strength of the group B was stronger than that of the groups A and C (P < 0.01); the average pull-out strength of the group A was stronger than that of group C (P < 0.01), the difference was statistically significant (P < 0.05). However, the average static compression of the group A and group B was similar; the average static compression of the group C was lower than that of the groups A and B, and the difference was statistically significant (P < 0.01). (2) In the goat vertebrate model, the average pull-out strength and static compression of the group A were stronger than that of the group B, and the difference was statistically significant (P < 0.05). (3) Results suggest that unilateral screw fixation in the artificial and goat vertebrate laminoplasty can provide sufficient pull-out strength and static compression, and the biomechanical strength is positively related to the depth of the screw.
RESUMEN
<p><b>OBJECTIVE</b>To evaluate clinical effects of pedicle fixation without bone fusion in treating thoracolumbar fractures through paraspinal approach.</p><p><b>METHODS</b>From January 2006 to January 2009, 25 patients (15 males and 10 females) with thoracolumbar fractures were treated. The average age was 39.3 years,ranged from 17 to 49 years. According to classification, flexion fracture in 7 cases, brust fracture in 18 cases. There were no nervous injury, and radiology information showed the angle of sagittal vertebral body >20 degrees or collapse of vertebral body >40%,without vertebral injury. The operation were performed at 3 to 7 days after injury (mean 5 day). Internal fixation implants were removed at 8 to 12 months after operation. The height, kyphosis angle were measured before operation, 1 week and 24 months after operation,and Oswestry disability index (ODI) were compared before and after operation.</p><p><b>RESULTS</b>All patients were followed up for 24 months. Among them, 1 case was followed up at 30 months after operation. The operation time ranged from 70 to 110 (mean 90) minutes, the blood loss was 120 to 280 (mean 200) ml. The height of vertebral body and kyphosis angle were obviously corrected, and had significant differences between postoperation immediately and at the final follow-up (P<0.05). There were no differences after remove of internal fixation (P>0.05). The final ODI was (5.36 +/- 1.21)%, had statistical differences compared with preoperation (P<0.05).</p><p><b>CONCLUSION</b>For flexion and burst thoracolumbar fractures without nervous injury, pedicle fixation without bone fusion is a good method,which has advantages of minimally invasive, rapid recovery, and maintain spinal motion segment.</p>