Published online Jul 16, 2024. doi: 10.12998/wjcc.v12.i20.4108
Revised: April 24, 2024
Accepted: May 31, 2024
Published online: July 16, 2024
Processing time: 109 Days and 21.9 Hours
The pedicle screw technique is widely employed for vertebral body fixation in the treatment of spinal disorders. However, traditional screw placement methods require the dissection of paraspinal muscles and the insertion of pedicle screws at specific transverse section angles (TSA). Larger TSA angles require more force to pull the muscle tissue, which can increase the risk of surgical trauma and ischemic injury to the lumbar muscles.
To study the feasibility of zero-degree TSA vertical pedicle screw technique in the lumbosacral segment.
Finite element models of vertebral bodies and pedicle screw-rod systems were established for the L4-S1 spinal segments. A standard axial load of 500 N and a rotational torque of 10 N/m were applied. Simulated screw pull-out experiment was conducted to observe pedicle screw resistance to pull-out, maximum stress, load-displacement ratio, maximum stress in vertebral bodies, load-displacement ratio in vertebral bodies, and the stress distribution in pedicle screws and vertebral bodies. Differences between the 0-degree and 17-degree TSA were compared.
At 0-degree TSA, the screw pull-out force decreased by 11.35% compared to that at 17-degree TSA (P < 0.05). At 0-degree and 17-degree TSA, the stress range in the screw-rod system was 335.1-657.5 MPa and 242.8-648.5 MPa, separately, which were below the fracture threshold for the screw-rod system (924 MPa). At 0-degree and 17-degree TSA, the stress range in the vertebral bodies was 68.45-78.91 MPa and 39.08-72.73 MPa, separately, which were below the typical bone yield stress range for vertebral bodies (110-125 MPa). At 0-degree TSA, the load-displacement ratio for the vertebral bodies and pedicle screws was slightly lower compared to that at 17-degree TSA, indicating slightly lower stability (P < 0.05).
The safety and stability of 0-degree TSA are slightly lower, but the risks of screw-rod system fracture, vertebral body fracture, and rupture are within acceptable limits.
Core Tip: This study aimed to explore the feasibility of employing zero-degree transverse section angles (TSA) vertical pedicle screw technique in the lumbosacral segment to reduce surgical trauma and ischemic injury to the lumbar muscles during pedicle screw insertion. The safety and stability of the zero-degree TSA vertical pedicle screw technique in the lumbosacral segment were slightly lower than those of the 17-degree TSA screw placement technique. However, the risks of screw-rod system fractures, vertebral body fractures, and ruptures were within acceptable limits. The screws exhibited high resistance to pull-out. The use of this zero-degree TSA vertical pedicle screw technique offers good safety and reliability. It can reduce surgical dissection of the multifidus muscles and minimize surgical trauma to the lumbar muscles.