Clinical research on the accuracy of cervical pedicle screws

Abstract

Objective To evaluate the clinical effect of a self-developed technique of manual placement of pedicle screw in cervical spine based on anatomical research. Methods Data of 105 patients who had cervical pedicle screw placement within seven years (from April 2007 to April 2013, and April 2013 to April 2016) were retrospectively analyzed, including 60 male and 45 female, aged from 20 to 76 years (51.7±14.5 years). Five main types of spinal injury were included: traumatic spinal injury (61 cases), degenerative cervical injury (19 cases including 12 ossification of posterior longitudinal ligament and 7 cervical spondylosis), cervical cancer (16 cases including 9 schwannoma, 4 meningioma, and 3 cases of cervical vertebral tumor), cervical deformity (6 cases including 3 kyphosis and 3 congenital malformation), and intervertebral space infection (3 cases). All the patients had X-ray, CT scan and MRI imaging pre-operatively, and X-ray and CT scan were also performed post-operatively to assess the accuracy of the position of screws. The accuracy of pedicle screws placement and screw leaning degree were analyzed according to the Lee standard. Grade 0: no penetration; Grade I: pedicle penetration within 25% of the pedical screw diameter; Grade II: pedicle penetration between 25% to 50% of the pedical screw diameter; Grade III: pedicle penetration beyond 50% of the pedical screw diameter. Grade II and III were considered as misplacement. In patients of Grade II and/or III, complications of blood vessels and nerve injury, etc. were observed. American spinal injury association (ASIA) was used to classify spinal injury among patients with trauma, while Japanese Orthopaedic Association Scores (JOA) was used to evaluate neural function improvement within patients without trauma. Results A total of 510 screws were placed by manual placement in 105 patients. Among 99 valid patients (6 without post-operative CT scan were excluded) with 497 screws (including 201 in upper cervical spine, and 296 in lower cervical spine), the results were shown as following: (1) Screw placement accuracy: 486 screws of Grade 0, 8 screws of Grade I, 3 screws of grade II, and 0 screws of Grade III. (2) 11 screws were penetrated pedical cortex with 8 of Grade I and 3 of Grade II (2 penetrated into cortical paries medialis and 1 penetrated into paries lateralis, but no screw penetrated into upper or inferior border). The accuracy of screw placement was 97.79% (Grade 0), the total misplacement rate was 0.6% (Grade II and III). According to post-operative follow up in 12 to 30 months (average 20.6±5.2 months), no complication of spinal, nerve root, or vascular injury was found. No screw loosening or fracture occurred, and all bones were healed properly. Follow up in the 6 months after operation showed that patients with trauma had significantly improvement in ASIA grading, while patients without trauma had better JOA scores. Conclusion Based on the study, the technique of manual placement of pedicle screw in cervical spine is considered to be safe and reliable. Considering its wide indication, it’s a technique worthy of clinical application. Key words: Cervical vertebrae; Spinal fusion; Bone screws; Tomography, X-ray computed