Yonsei Med J.  2005 Jun;46(3):372-378. 10.3349/ymj.2005.46.3.372.

Cortical Margining Capabilities of Fins Associated with Ventral Cervical Spine Instrumentation

• Jin BH
• Kwon HD
• Cho YE

• KMID: 1734072
• DOI: http://doi.org/10.3349/ymj.2005.46.3.372

Abstract

Fins incorporated into the design of a dynamic cervical spine implant have been employed to enhance axial load- bearing ability, yet their true biomechanical advantages, if any, have not been defined. Therefore, the goal of this study was to assess the biomechanical and axial load-bearing contributions of the fin components of the DOC ventral cervical stabilization system. Eighteen fresh cadaveric thoracic vertebrae (T1-T3) were obtained. Three test conditions were devised and studied: Condition A (DOC implants with fins were placed against the superior endplate and bone screws were not inserted) ; Condition B (DOC implant without fins was placed and bone screws were inserted) ; and Condition C (DOC implant with fins were placed against the superior endplate and bone screws were inserted). Specimens were tested by applying a pure axial compressive load to the superior platform of the DOC construct, and load-displacement data were collected. Condition C specimens had the greatest stiffness (459 +/- 80N/mm) and yield load (526 +/- 168N). Condition A specimens were the least stiff (266 +/- 53N/mm), and had the smallest yield loads (180 +/- 54N). The yield load of condition A plus condition B was approximately equal to that of condition C, with condition A contributing about one-third and condition B contributing two-thirds of the overall load-bearing capacity. Although the screws alone contributed to a substantial portion of axial load-bearing ability, the addition of the fins further increased load-bearing capabilities.

Keyword

Biomechanics; cervical plate; fins

MeSH Terms

*Bone Plates
Bone Screws
Humans
In Vitro
Spinal Fusion/*instrumentation
Thoracic Vertebrae/*physiology/*surgery
*Weight-Bearing

Figure

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  Fig. 1 A: Condition A instrumentation; platform was placed so that the fins were resting against the superior endplate, and no screws were inserted. B: Condition B instrumentation; platforms without fins were placed on the vertebral bodies, and two screws were inserted. C: Condition C instrumentation; platform was placed so that the fins were resting against the superior endplate, and two screws were inserted.

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  Fig. 2 Specimen setup on materials testing system; a probe was used to axially compress the superior DOC platform.

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  Fig. 3 Bar graph showing the stiffness values of the three instrumented conditions.

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  Fig. 4 Bar graph showing the yield loads of the three instrumented conditions.

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