Cervical Pedicle Screw Insertion with Medial Pedicle Pivot Point: A Novel Technique

Seoul, Korea:The study by Ji-Won Kwon et al describes a new and safe freehand cervical pedicle screw insertion technique using preoperative computed tomography (CT) morphometric measurements as a guide and a medial pedicle pivot point (MPPP) during the procedure.

A pedicle diameter (PD) ≥ 3.5 mm was the cut-off for pedicle screw fixation.

Each patient underwent preoperative plain cervical CT using a multisided scanner. To identify the correct starting point and direction of screw insertion for each pedicle, linear and angular parameters were measured on both the sagittal and axial CT images; this was performed for each patient at every cervical level on both the right and left sides.

On sagittal images, the distance (in mm) was measured from the tip of the inferior articular process of the cephalad cervical vertebra to a point in the lateral mass transected by a line drawn through the center of the pedicle; this was defined as the facet-pedicle distance(FPD). The sagittal images were cross-referenced with axial cuts to ensure that the measurements were obtained at the starting point between the medial third and center of the lateral mass on each side.

The lateral mass depth (LMD;) was measured from the starting point at the dorsal border to the MPPP of the corresponding lateral mass on each side (usually corresponding with the point where a line from the dorsal border of the lateral mass intersected the pedicle total length (PTL) line). The pedicle insertion angle (PIA)—formed by a line from the center of the spinous process to the center of the vertebral body and along the center of the pedicle (the PTL line)—was measured on both sides. The PTL was measured from the posterolateral border of the lateral mass to the anterior border of the vertebral body. The point at which the LMD and PTL lines intersected at the center of the lateral mass corresponded with the MPPP, representing the point at which the direction or angle of the pedicle probe was positioned to match the desired PIA and horizontal direction, as guided by intraoperative radiographs.

The linear and angular radiologic parameters measured via the preoperative CT scan were captured at all cervical levels scheduled for surgical treatment; this was presented on a PowerPoint slide in the form of a screenshot, allowing the images to be viewed on a computer monitor in the operating room.

The presence and grade of perforation were detected using postoperative CT scans, where perforations were graded as follows: 0, no perforation; 1, perforation < 0.875 mm; 2, perforation 0.875–1.75 mm; and 3, perforation > 1.75 mm.

The study included 271 pedicles at 216 cervical spine levels (mean: 4.75 pedicles per patient).

The overall success rate was 96.3% (261/271, Grade 0 or 1 perforations). In total, 54 perforations occurred, among which 44 (81.5%) were Grade 1 and 10 (18.5%) were Grade 2. The most common perforation direction was medial (39/54, 72.2%).

The authors concluded that – this freehand technique for cervical pedicle screw fixation using the MPPP may be safe and accurate in patients with a PD ≥ 3.5 mm. Linear and angular measurements on preoperative CT images for each cervical pedicle can be used as a simple and accurate guide when the PD is ≥3.5 mm.

Further reading:

Medial Pedicle Pivot Point Using Preoperative Computed Tomography Morphometric Measurements for Cervical Pedicle Screw Insertion: A Novel Technique and Case Series

Ji-Won Kwon, Edward O. Arreza, Anthony A. Suguitan, Soo-Bin Lee, Sahyun Sung, Yung Park, Joong-Won Ha, Tae Hyung Kim, Seong-Hwan Moon and Byung Ho Lee .

J. Clin. Med. 2022, 11, 396.

https://doi.org/10.3390/jcm11020396