Cortical and Standard Trajectory Pedicle Screw Fixation Techniques in Stabilizing Multisegment Lumbar Spine with Low Grade Spondylolisthesis.
BACKGROUND
Cortical screw (CS) fixation has been recently proposed as an alternative to the standard pedicle screw (PS) fixation technique. Biomechanical studies involving individual screw pullout and single level motion segment stabilization showed comparable performance of both techniques. However, whether this new fixation technique can be applied to the stabilization of multilevel lumbar segments with significant destabilization has been unclear.


OBJECTIVE
To compare stability of CS fixation to the traditional PS fixation in an unstable 3 level spondylolisthesis model.


METHODS
This is a biomechanical study comparing cortical trajectory pedicle screw fixation to traditional trajectory pedicle screw fixation in an unstable cadaveric model using nondestructive flexibility test.


METHODS
Eight fresh frozen cadaveric lumbar spines (T12- S1) were obtained. After intact baseline testing, a 3-level lowgrade spondylolisthesis was simulated at the L1-4. Each specimen was instrumented with the PS and CS fixation systems. Standard nondestructive flexibility test was performed. Range of motion at each level was compared between the constructs during flexion-extension, lateral bending, and axial rotation.


RESULTS
The destabilization model significantly increased the ROM in all planes (P<0.05). Both fixation techniques provided significant reduction in the ROM (P<0.05). There was no significant difference in ROM between the PS and CS groups in any of planes (P>0.05).


CONCLUSIONS
Cortical trajectory pedicle screw fixation provided stabilization to multilevel lumbar segment with low-grade spondylolisthesis comparable to the standard trajectory pedicle screw construct.
Department of Orthopaedic Surgery, Loma Linda University School of Medicine, Loma Linda, CA, USA.
Wayne K
WK
Cheng
Department of Orthopaedic Surgery, Loma Linda University School of Medicine, Loma Linda, CA, USA.
Serkan
S
İnceoğlu
Cortical bone trajectory; Pedicle screw; biomechanics; cortical screw; low grade spondylolisthesis model; lumbar spine