Percutaneous transvertebral fixation of thoracolumbar fractures with monoaxial and polyaxial pedicle screws

Objective To evaluate effect of percutaneous transvertebral fixation of thoracolumbar fractures using both monoaxial and polyaxial pedicle screws.Methods The study involved single-level thoracolumbar fracture patients without neurological deficits undergone minimally invasive percutaneous fixation with CD-Horizon Longitude system from January 2010 to December 2011.Three level vertebras were immobilized by six pedicle screws.They were randomized into two groups:control group fixed with polyaxial screws for the fractured vertebra as well as the upper and lower adjacent vertebras and study group fixed with monoaxial screws for the superior adjacent vertebra and polyaxial screws for the injured vertebra and inferior adjacent vertebra.General information,height of fracture vertebral body,Gardner segmental kyphotic deformity,GSKD) and local kyphosis angle were assessed and compared between groups after operation so as to estimate correction ability of kyphosis deformity.Visual analogue scale (VAS) and Oswestry disability index (ODI) were used to evaluate alteration of back pain and lower limb function.Incidence of screw breakage was also compared between groups.Results Totally,30 patients were enrolled in the trial and received an average follow-up of 10.5 months (range,6-18 months).Two groups were similar in general information (sex,age,fracture levels,and fracture types) and perioperative information (operation time,intraoperative blood loss,proportion of antalgic supplement and hospital stay).GSKD and local kyphosis angle were significantly higher in study group than in control group after operation [(15.0 ± 5.4) °vs (8.8 ± 5.4) °,(16.0-6.5) ° vs (9.0 ± 5.5) ° respectively,P ＜ 0.01].While,correction loss of GSKD and local kyphosis was similar between study and control groups [(2.6 ±1.3)°vs (1.9 ± 1.5)°,(3.7 ±2.1)° vs (2.7 ±2.2)° respectively,P ＞0.05].Correction of anterior vertebral body height and correction loss of posterior vertebral body height were superior in study group to control group [(33.0 ± 11.4) ％ vs (22.7 ± 11.4) ％,(1.2 ± 1.2) ％ vs (2.5 ± 2.1) ％ respectively,P ＜ 0.05].Correction loss of anterior vertebral body height and correction of posterior vertebral body height were similar between study and control groups [(2.8 ± 2.7) ％ vs (5.4 ± 4.7) ％,(5.0 ±4.8) ％ vs (3.1 ± 2.9) ％ respectively,P ＞ 0.05].Besides,there were no significant differences of VAS and ODI between the two groups in the same period after operation.Conclusion Combined use of monoaxial and polyaxial pedicle screws in minimally invasive percutaneous fixation improves kyphosis deformity and correction ability of anterior height and decreases correction loss of posterior height of the fractured vertebral body. Key words: Spinal fractures; Thoracic vertebrae; Lumbar vertebrae; Fracture fixation,internal; Surgical procedures,minimally invasive