Biomechanical Evaluation of the Pullout Strength of the Dynamic Osteosynthesis Construct(DOC) Anterior Cervical Plating System: A Comparison between the Screw Angulations to Consider the Concept of Triangulation

Eun, Jong Pil

Abstract

OBJECTIVE
The aim of this study is to biomechanically assess the pullout strength of the dynamic osteosynthesis construct(DOC) cervical plating system to consider the effects of screw triagulation in the cervical spine. METHODS: Twelve fresh cadaveric cervical spines(C4-C7) were randomly instumented with DOC cervical system with 20 degree(six specimens) or 30 degree platforms(six specimens). All specimens were tested on an MTS Alliance RT/10 testing machine. Load-displacement data was sampled at a rate of 50Hz. After the biomechanical testing, specimens were cut on sagittal plane and the penetrating depths of screw were measured.
RESULTS
Mean insertion torque of 20 degree was 1.025 newton-meters and that of 30 degree was 1.031 newton-meters(p>0.05). Mean penetration depth of 20 degree was 11.82mm(C4), 12.20mm(C7) and that of 30 degree platforms were 12.22mm(C4), 13.04mm(C7). Mean pullout strength with 20 degree platforms was 642.2 N ; with 30 degree platforms was 537.7N(p>0.05).
CONCLUSION
There is no statistical differences in pullout strength between 20 degree platform and 30 degree platform that were plated in cervical vertebral bodies, even though a literature shows that more increased screw angulation of 30 degree than that of 20 degree would decrease pullout resistance due to less amount of bone purchase against the pullout force in parallelogram shaped cervical vertebral body.