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  • By Author: Sonntag, Volker K. H. x
  • By Author: Ames, Christopher P. x
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Christopher P. Ames, Neil R. Crawford, Robert H. Chamberlain, Vivek Deshmukh, Belma Sadikovic and Volker K. H. Sonntag

Object. The authors tested the ability of a resorbable cannulated lag screw composed of a polylactide copolymer to repair Type II odontoid fractures. The resorbable screw was evaluated for its ability to restore strength and stiffness to the fractured odontoid process compared with traditional titanium screws.

Methods. Type II odontoid fractures were created in 14 human cadaveric C-2 vertebrae by applying a posterolaterally directed load and piston displacement was measured. Seven of these specimens were repaired using metal screws and seven were repaired using resorbable screws. Specimens were reinjured using the same mechanism as the initial fracture. Values of ultimate strength and stiffness during failure were statistically compared between metal and resorbable screws and between initial fracture and reinjury.

Conclusions. The stiffness and ultimate strength during initial fracture were significantly greater than those during reinjury in specimens repaired using resorbable screws or titanium screws (p < 0.001). The resorbable and titanium screws both restored 31% of the initial ultimate strength of the intact specimen (p = 0.95). The stiffness of the fractured odontoid process was restored to 15 and 23% of its initial value by repair with resorbable and metal screws, respectively (p = 0.07). The mode of failure in resorbable screws was usually breakage or bending, whereas that in metal screws was consistently cutout of the proximal shaft of the screw through the anterior C-2 vertebral body.

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Christopher P. Ames, G. Bryan Cornwall, Neil R. Crawford, Eric Nottmeier, Robert H. Chamberlain and Volker K. H. Sonntag

✓ In this article the authors review the history of anterior cervical plating for one- and two-level discectomy for degenerative disease and provide background justification for the design and testing of a cervical plate composed of a resorbable material. The design of the plate is discussed with special reference to modifications of its design and tools compared with metallic plates that are necessary because of the different mechanical properties of the less rigid material. The cadaveric and animal in vivo testing methodologies are described, and a novel testing method for reliably quantifying graft containment is also described. Data from a representative sample are presented. Advantages and disadvantages of resorbable plating are discussed.