The medial cortical pedicle screw—a new technique for cervical pedicle screw placement with partial drilling of medial cortex

Abstract Background context Studies on cadavers have shown that the appropriate insertion of cervical pedicle screw (C3–C7) should be done from a more lateral point and at a steeper angle in the axial plane, than that described by Abumi et al., to decrease the chances of lateral perforation. Purpose We describe a new technique for cervical pedicle screw (CPS) placement (C3–C7) using high-speed pneumatic drill with partial drilling of medial cortex for decreasing the chances of lateral perforation. Study design Description of new surgical technique with retrospective data analysis. Patient sample Twenty-five patients undergoing cervical spine surgery with CPS instrumentation in the lower cervical spine (C3–C7) from April 2011 to October 2012 at our institute were included in the study. Outcome measures All patients were evaluated with computed tomography scans postoperatively for the assessment of pedicle screw placement. Pedicle screw perforations were graded with the following criteria: Grade I perforations having ≤50% of the screw outside the pedicle and Grade II perforations having >50% of the screw outside the pedicle. Clinical complications directly related to CPS placement were also recorded. Methods Twenty-five patients undergoing surgery with CPS instrumentation (C3–C7) at our institute between April 2011 and October 2012 were included in the study. Thirteen patients had cervical trauma, 10 had cervical spondylotic myelopathy, 1 had congenital cervico-dorsal scoliosis, and 1 was a patient with ankylosing spondylitis. Pedicle screw insertion was made according to the technique by Abumi et al., with the use of blunt pedicle probes in eight of these cases (Group I). In the other 17 cases (Group II), the pilot hole was made with the use of 2-mm diamond tipped burr, partially drilling the medial cortex and entering the vertebral body with the burr itself. Results A total of 131 CPSs (C3–C7) were inserted in 25 patients. In Group I, 43 pedicle screws were placed and 88 screws were placed in Group II, with partial drilling of medial cortex. Lateral perforations: in Group-I, more of lateral perforations were observed with 18.6% Grade I and 9.3% Grade II lateral perforations. In Group II, the lateral perforations were lower with 7.95% Grade I and 1.1% of Grade II lateral perforations. I Group-I, medial perforations were lower with 11.62% Grade I and 2.3% Grade II perforations. In Group II, the Grade I and Grade II medial perforations were 30.7% and 4.5%, re