A biomechanical comparison of three spondylolysis repair techniques in a calf spine model - 27/12/12

Doi : 10.1016/j.otsr.2012.10.011

R. Roberto ^a, B. Dezfuli ^b,^⁎ , C. Deuel ^a, S. Curtiss ^a, S. Hazelwood ^a
^a Department of Orthopaedic Surgery, University of California at Davis School of Medicine, Sacramento, California, United States
^b Department of Orthopaedic Surgery, University of Arizona College of Medicine, 1609N. Warren Avenue, Suite 110, PO Box 245064, Tucson, Arizona, United States

Corresponding author. Tel.: +520 626 9245; fax: +520 626 2668.

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Summary

Summary of background data

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 miniplating has not previously been described.

Methods

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, miniplate, or cable plate (CP) constructs. (n=9). A 5-Nm load was applied in flexion-extension, lateral bending and axial rotation. Fracture displacement was measured under flexion-extension and lateral bending modes.

Results

Osteotomy of the pars interarticularis increased intervertebral rotation from 4.6° to 9.2° (P<.05). The three techniques of repair reduced intervertebral rotation without statistical superiority of one method. In lateral bending the miniplate was most effective in reducing pars defect displacement (0.6mm, P<0.05). Although, the miniplate provided lower defect displacement in flexion-extension and axial rotation, these differences were not statistically significant.

Conclusions

Bilateral miniplate 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.