Previous work has demonstrated the efficacy of lumbar pedicle screw hook rod (PSHR) techniques and the Buck screw in the stabilization of spondylolysis. The mechanical behavior of lower profile cervical implants used to create PSHR, hybrid cable plate constructs, and titanium mini-plating has not previously been described.

Calf lumbar spines (L2-L6) were utilized for testing (n=27). Intervertebral rotation was measured in the intact spines across the L4-5 segment before and after creation of bilateral pars interarticularis defects. Defects were then stabilized with one of three repair techniques, PSHR, mini-plate, or cable plate (CP) constructs (n=9). A 5Nm load was applied in flexion extension, lateral bending and axial rotation. Fracture displacement was measured under flexion extension and lateral bending modes.

Osteotomy of the pars interarticularis increased intervertebral rotation from 4.6° to 9.2° (P<0.05). The three techniques of repair reduced intervertebral rotation without statistical superiority of one method. In lateral bending, the mini-plate was most effective in reducing pars defect displacement (0.6mm, P<0.05). Although the mini-plate provided lower defect displacement in flexion extension and axial rotation, these differences were not statistically significant.

Bilateral mini-plate fixation demonstrates superiority in restoring stability in lateral bending as compared to pedicle screw hook rod techniques and cable plate constructs. In flexion extension and axial rotation, it was as effective as a PSHR method. Consideration of anatomic plate designs warrants consideration.

IV.