Techniques and Tips for Freehand Placement of C7 Pedicle Screws With Respect to Cervicothoracic Constructs: 2-Dimensional Operative Video

Abstract

We present a surgical video highlighting the technical pearls for C7 pedicle screw placement with respect to cervicothoracic constructs. Pedicle screw placement into C7 has been shown to enhance the biomechanical stability of both cervical and cervicothoracic constructs and is safe for patient related outcomes.1,2 Rod placement across the cervicothoracic junction is known to be difficult because of the variable starting point of the C7 pedicle screw, which may cause misalignment of the polyaxial heads with respect to the C7 and C6 screw heads. Using our step-wise method of anatomic screw placement, this potential pitfall is minimized. The T1 pedicle screw is placed first. The C6 lateral mass screw starting point is displaced slightly superiorly from the midpoint of the lateral mass in order to make room for the polyaxial head of the C7 pedicle screw. A small laminotomy is performed in order to find the medial border of the C7 pedicle. Palpation of the medial border allows for an approximation of the pedicle limits. The cranial-caudal angle of drilling is perpendicular to the C7 superior facet, and the medial-lateral trajectory typically falls between 15 and 20 degrees medial. Once the pedicle is cannulated, a ball-tipped probe is used to confirm intraosseous position. A rod is cut and contoured to the appropriate length of the construct. The C7 pedicle screw should capture the rod easily with slight displacement of the polyaxial head. Postinstrumentation anteroposterior and lateral fluoroscopy are performed to confirm good position of the lateral mass and pedicle screws. Patient consent was not required for this cadaveric surgical video.

Utility of intraoperative electromyography in placing C7 pedicle screws

“…tion level is controversial when considering the cervicothoracic junction, with some surgeons choosing to extend the fusion to the proximal thoracic spine instead of ending at C7, in part due to the unique morphometric properties of the C7 vertebral body and the challenges that its fixation presents. 1,2,5,6 The C7 vertebral body represents the transition point from the subaxial cervical spine to the upper thoracic spine. It has the largest vertebral body, longest spinous processes, and a relatively small lateral mass compared to other subaxial cervical levels.…”

“…It has the largest vertebral body, longest spinous processes, and a relatively small lateral mass compared to other subaxial cervical levels. 1,5,7,10 The C7 pedicle is often highly cortical and the dorsal landmarks for freehand placement can have significant variability. 1,5,10,11,14 As compared to lateral mass and translaminar screws, studies have demonstrated the biomechanical superiority of pedicle screws, especially at the distal end of a construct.…”

“…1,5,7,10 The C7 pedicle is often highly cortical and the dorsal landmarks for freehand placement can have significant variability. 1,5,10,11,14 As compared to lateral mass and translaminar screws, studies have demonstrated the biomechanical superiority of pedicle screws, especially at the distal end of a construct. 1,18,21,26 However, intraoperative evaluation of cervical pedicle screw placement can be difficult to assess using fluoroscopy alone.…”

“…1,18,21,26 However, intraoperative evaluation of cervical pedicle screw placement can be difficult to assess using fluoroscopy alone. 2,[5][6][7][8]13 There are often numerous technical challenges in obtaining a satisfactory view of the pedicles, including a patient's body habitus, shoulders, and positioning. 5,7,11,14 As a result, surgeons have to rely on other techniques to allow for safe pedicle screw placement.…”

“…2,[5][6][7][8]13 There are often numerous technical challenges in obtaining a satisfactory view of the pedicles, including a patient's body habitus, shoulders, and positioning. 5,7,11,14 As a result, surgeons have to rely on other techniques to allow for safe pedicle screw placement. [14][15][16][17]20 Some surgeons avoid fixation at C7 and favor extending the instrumented construct to the upper thoracic spine.…”