Article
Biomechanical comparison of the stability between one- and two-screw fixation method for type II dens fractures on the basis of repetitive dynamic stiffness tests
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Authors
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Lambert Schless
- Klinik für Neurochirurgie, Universitätsklinikum Schleswig-Holstein, Campus Lübeck
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Insa Schneegans
- Klinik für Neurochirurgie, Unfallkrankenhaus Berlin
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Volker M. Tronnier
- Klinik für Neurochirurgie, Universitätsklinikum Schleswig-Holstein, Campus Lübeck
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Jan Gliemroth
- Klinik für Neurochirurgie, Universitätsklinikum Schleswig-Holstein, Campus Lübeck
| Published: | May 13, 2014 |
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Outline
Text
Objective: The type II odontoid fracture by Anderson and D’Alonzo is the most common type of ondontoid fracture. Fractures of Dens axis represent 1-2% of all spine fractures and 60% of all axis fractures. It is inherently unstable because the odontoid is the keystone as well as the pivot of the craniovertebral junction. The anterior odontoid fixation of type II dens fractures provides the best treatment for fracture stabilisation with preservation of cervical rotation. However, until now a definite advantage of the one or two screw technique could have not been proven in clinical studies. Biomechanical tests under static condition identified no significant difference between both treatments. Thus, the purpose of this biomechanical study is to prove the advantage of the two screw fixation by repetitive dynamic stiffness tests.
Method: For the study 12 fresh C-2 bone samples were randomly divided into two groups. After creating an osteotomy at the junction of the dens and vertebra, each sample was provided with either one or two screws. In our self-designed dynamic-testing-machine it ought to be looked at the primary torsional stiffness, the torsional stiffness after continuous loading and the remaining deformations after continuous loading as well as the influence of independent criteria such as bone mineral density, age, sex and dens calibre.
Results: The statistical analysis revealed that the two-screw-osteosynthesis was superior with regard to the primary torsional stiffness (p = 0.041) and the torsional stiffness after continuous loading (p = 0.041). The torsional stiffness after continuous loading even increased (by 28.3%) in the group of the two screwed bone samples. Whereas in the group of the one screwed bone samples the torsional stiffness declined (to 97.1%). Furthermore, a correlation between sex and the torsional stiffness after continuous loading was proven (R = -0.520; p = 0.042). However, age (p = 0.89), bone mineral density (p = 0.075) and dens calibre (p = 0.73) had no influence on the osteosynthesis.
Conclusions: If the geometrical bone feature allows an implantation of two screws, then this particular treatment ought to be preferred from a biomechanical view.
