• Albrecht Waschke, Nikolaus Berger-Roscher, Heike Kielstein, Christian Ewald, Rolf Kalff, and Hans-Joachim Wilke.
• *Department of Neurosurgery, Jena University Hospital, Friedrich Schiller University Jena, Jena †Institute of Orthopaedic Research and Biomechanics, Ulm University, Ulm ‡Institute of Anatomy and Cell Biology, Martin Luther University Halle, Halle, Germany.
• J Spinal Disord Tech. 2015 Apr 1;28(3):E126-32.

Study DesignA biomechanical human cadaveric study.ObjectiveThe authors tested a cannulated and perforated lag screw and compared in situ polymethylmethacrylate (PMMA) augmentation against nonaugmentation for fixation of osteoporotic type II odontoid fractures.Summary Of Background DataOsteoporosis has been identified as a strong predictor for pseudarthrosis after screw fixation of type II odontoid fractures with cut-out through the anterior wall of C2 as the most frequent mode of implant failure. The concept of PMMA augmentation of the proximal screw shank could serve as a useful supplement in this context.MethodsA total of 18 fresh-frozen human cadaveric C2 vertebrae were harvested (median 86.5 y; range, 69-98 y). Reduced bone quality was verified by quantitative computed tomography. Type II odontoid fractures were created and repaired with a cannulated lag screw, which has perforations in the proximal screw shank. Additional PMMA augmentation was carried out for 9 specimens. The position of the screw and cement distribution were evaluated by computed tomography. Values for maximum force to failure, energy to failure, and stiffness were statistically compared between cement augmented and nonaugmented screws.ResultsCement distribution in the C2 vertebral body was circumferential around the screw shank without leakage into the spinal canal or into the fracture gap in all 9 specimens. The cement augmented screws showed a 2.4 times higher maximum force to failure (363±94 N, P<0.001), a 2.7 times higher energy to failure (1300±698 mJ, P<0.001), and a 1.76 times higher stiffness (90±35 N/mm, P=0.031) in comparison with the nonaugmented screws.ConclusionsCement augmentation for fixation of osteoporotic type II odontoid fractures showed biomechanical advantages. It was also shown that cement augmentation of the newly developed screw is technically easy and safe under in vitro conditions. The technique might be useful with regard to the surgical treatment of elderly patients with osteoporotic odontoid fractures.

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