ANATOMIC CONSIDERATION OF TRANSPEDICULAR SCREW PLACEMENT IN THE CERVICAL-SPINE - AN ANALYSIS OF 2 APPROACHES

Study Design. This study compared the effectiveness of two transpedicu lar screw placement techniques: blind screw placement versus screw pla cement after direct determination of the superior, medial, and inferio r borders of the pedicle through the opening of a ''window'' by the pa rtial laminectomy and tapping technique. Objectives. To determine if t he incidence and severity of pedicle violations resulting from transpe dicular screw placement could be reduced by direct determination of th e superior, medial, and inferior borders of the pedicle through the op ening of a ''window'' by partial laminectomy. Summary of Background Da ta, Several studies regarding transpedicular screw fixation for unstab le cervical spine injuries have been reported, but none has addressed the effectiveness in lowering the incidence of pedicle violation by op ening a ''window'' by partial laminectomy for direct determination of the superior, medial, and inferior borders of the pedicle and using th e tapping technique before and in planning for screw placement. Method s. Eight adult cadaveric cervical spines (40 vertebrae from C3 to C7) were used for this study. Two groups were formed according to screw pl acement techniques. The first group was composed of 38 blinded transpe dicular screw placements. The second group was composed of 40 screw pl acements using the partial laminectomy and tapping technique; After tr anspedicular screw placement, all specimens were evaluated radiographi cally and visually for violation of the pedicle. Results. A decrease i n the incidence and severity of pedicle violation was seen in the seco nd group with opening of the lamina and tapping technique compared wit h the blind screw placement group. However, the percentage of screws f ound to violate the pedicle with the opening of the lamina and tapping technique still was relatively high. Conclusions. Transpedicular scre w placement in the cervical spine is difficult, and a high percentage of violations of the pedicle wall occur. This technique should not be used routinely.