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

Written By : Dr Supreeth D R |Medically Reviewed By : Dr. Kamal Kant Kohli Published On 2022-04-25T09:00:35+05:30 | Updated On 25 April 2022 9:00 AM IST

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.

MBBS, Dip. Ortho, DNB ortho, MNAMS

Dr Supreeth D R (MBBS, Dip. Ortho, DNB ortho, MNAMS) is a practicing orthopedician with interest in medical research and publishing articles. He completed MBBS from mysore medical college, dip ortho from Trivandrum medical college and sec. DNB from Manipal Hospital, Bengaluru. He has expirence of 7years in the field of orthopedics. He has presented scientific papers & posters in various state, national and international conferences. His interest in writing articles lead the way to join medical dialogues. He can be contacted at editorial@medicaldialogues.in.

Dr. Kamal Kant Kohli

Dr Kamal Kant Kohli-MBBS, DTCD- a chest specialist with more than 30 years of practice and a flair for writing clinical articles, Dr Kamal Kant Kohli joined Medical Dialogues as a Chief Editor of Medical News. Besides writing articles, as an editor, he proofreads and verifies all the medical content published on Medical Dialogues including those coming from journals, studies,medical conferences,guidelines etc. Email: drkohli@medicaldialogues.in. Contact no. 011-43720751