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61st Annual Meeting of the German Society of Neurosurgery (DGNC) as part of the Neurowoche 2010
Joint Meeting with the Brazilian Society of Neurosurgery on the 20 September 2010

German Society of Neurosurgery (DGNC)

21 - 25 September 2010, Mannheim

Biomechanical comparison of anterior screw fixation in type II odontoid fracture – one- versus two-screw fixation

Meeting Abstract

  • Sebastian Spuck - Klinik für Neurochirurgie, UK-SH Campus Lübeck, Deutschland
  • Gang Feng - Orthopaedic Department of 2nd Affilliated Hospital, Medical School of Zhejiang University, China
  • Volker Tronnier - Klinik für Neurochirurgie, UK-SH Campus Lübeck, Deutschland
  • Lüder C. Busch - Institut für Anatomie, Universität zu Lübeck, Deutschland
  • Arndt Peter Schulz - Klinik für Chirurgie des Stütz- und Bewegungsapparates, UK-SH Campus Lübeck, Deutschland
  • Robert Wendlandt - Klinik für Chirurgie des Stütz- und Bewegungsapparates, UK-SH Campus Lübeck, Deutschland

Deutsche Gesellschaft für Neurochirurgie. 61. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC) im Rahmen der Neurowoche 2010. Mannheim, 21.-25.09.2010. Düsseldorf: German Medical Science GMS Publishing House; 2010. DocP1788

doi: 10.3205/10dgnc259, urn:nbn:de:0183-10dgnc2592

Published: September 16, 2010

© 2010 Spuck et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Objective: The ventral odontoid fixation in type II fractures (Anderson and D'Alonzo) by one- or two-screw- technique is a matter of debate. Two screws affords better stability for bending and rotation. Morphological studies suggested the diametrical dimensions in many patients would be insufficient to accommodate the passage of two screws. Clinical studies showed that there were no clinical advantage using a two screws and no significant difference in overall fusion rates. In this study the biomechanical stability of one- and two-screw osteosynthesis was compared in an in-vitro biomechanical cadaver trial.

Methods: 14 fresh C2 (8 male, 6 female, mean age of 77.9 years, range 60 to 98 years) with simulated type II fracture by osteotomy were randomly divided into two groups and fixed with one- or two-screw technique. The stiffness of intact specimens and after fixation in six directions was tested on a mechanical testing machine. The influence of bone mineral density (BMD) on shear stiffness (SS) and rotational stiffness (RS) was analyzed. Torque load of 1.5Nm was transmitted to the odontoid. Independent samples t-test was used for statistical analysis. Paired samples t test was used for statistical analysis of the differences between intact specimens and fractured specimens in a same group. Bivariate correlations analysis (Pearson correlation coefficients) was used for the statistical analysis between the BMD and the stiffness. Statistical significance was defined at p<0.05.

Results: Group A (one screw): mean age was 75,14±13,17y (range: 60–98 y). Group B (two screws): 80,71±6,47y (69–88 y). BMD in group A was 477,27±255,63mg/cm² vs. 343,74±239,02mg/cm² (group B). Neither in age or BMD a significant difference could be observed. In native unfractured probes SS had a significant correlation to BMD, contrary to the rotational stiffness RS. Fixation technique by one or two screws had no significant influence in SS. The RS is in group B higher, but the difference is not significant (torsion left p=0.169, left p=0.115). Compared to the native probe the SS and TS is significantly reduced both groups.

Conclusions: BMD has a significant influence on SS in unfractured probes, which could be seen only in one direction after fixation of the fracture (group B). Though the RS in two-screw fixation is higher (without significance), the stability of osteosynthesis is achievable by one-screw technique. Neither the one-screw, nor the two-screw technique is able to restore the SS and RS of the native probe.