The study of anterior cervical pedicle screw channel in the lower cervical spine

Abstract

Objective To investigate application of the anterior cervical pedicle screw in the lower cervical spine.Methods Twenty disarticulated human vertebrae (C3-C7) were evaluated with computed tomography for pedicle morphometry Parameters included vertebral body height,vertebral body depth,vertebral body width,outer pedicle width,outer pedicle height,pedicle axis length,transverse section angle,sagittal section angle,transverse intersection point distance and sagittal intersection point distance.On the basis of these data,the screw channel was determined and the screws were inserted in the specimen.Five patients underwent surgical reconstruction using anterior pedicle screw fixation.After surgery,physical examination and roentgenograms and CT scans were performed in all patients.Results The transverse section angle increased from C3(45.7°±4.0°) to C5(52.1°±5.9° ),but decreased from C6(47.8°±6.7°) to C7(44.4°± 8.3°).The sagittal section angle gradually increased from C3 (93.4°±7.2°) to C6( 112.1°±6.2°) but decreased a little to C7(102.7°±8.5°).The distances in transverse section was about 1.97-3.98 mm and in sagittal section was 3.4-7.5 mm.Anterior pedicle screws were inserted successfully in all specimens without critical pedicle wall perforations.Patients were permitted to ambulate the next day after surgery with a cervical collar.Postoperative neurological improvement was observed in all cases.Postoperative radiographic evaluation confirmed proper insertion of anterior pedicle screws without pedicle perforaton.The average follow-up time was 10.6 months.No anterior pedicle screw breakage and loosening was observed.Conclusion The entry point in anterior pedicle screw should located in 5mm to upper endplate and near anterior median line.The transverse section angle should be 45.7°-52.1°and the sagittal section angle should be 93.4°-112.1°.The lengths of the screw should be about 32 mm. Key words: Cervical vertebrae; Spinal fusion; Internal fixators; Anatomy