Biomechanische Untersuchungen ventraler Osteosyntheseverfahren bei Densfrakturen Anderson und D’Alonzo Typ II

Biomechanical analysis of different methods for anterior screw osteosynthesis in odontoid fractures Anderson and D'Alonzo type II

by Elisa Salge
Doctoral thesis
Date of Examination:2025-02-05
Date of issue:2025-01-14
Advisor:PD Dr. Jonathan Roch
Referee:PD Dr. Jonathan Roch
Referee:PD Dr. Christian Dullin
Persistent Address: http://dx.doi.org/10.53846/goediss-10984

 

 

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Abstract

English

The data on the use of single- or double-screw techniques for anterior osteosynthesis of type II odontoid fractures is inconclusive and contradictory. Although the double-screw technique appears to offer more rotational stability, no biomechanical studies have shown clear advantages over the single-screw technique. The double-screw technique increases the duration of surgery and leads to greater stress on the cervical soft tissues. It appears however to lead to a higher fusion rate in some radiological studies. Previous biomechanical studies on single- and double-screw techniques have neglected physiological conditions and only examined osteosyntheses with direct loading tests on the odontoid. The aim of this study was to design a device that mimics the physiological conditions of the atlantoaxial joint in order to test the stability after single- and double-screw techniques, as well as using a larger-diameter screw for the osteosynthesis of artificially created type II odontoid fractures. A 3D-printed, motor-driven apparatus was developed for mounting on a Zwick testing machine, allowing a combination of all directions of movement. 18 intact C1-3 specimens were embedded to best simulate physiological conditions. They were stratified into three groups, receiving either one 4.0 mm screw (1S), two 4.0 mm screws (2S) or one 5.0 mm double-threaded headless compression screw (HCS) after artificially creating a type II fracture. Each specimen was tested in combined motion in all movement dimensions with an increasing preload from 1 to 40 N. Screw loosening was observed visually, by fatigue data, and by a camera tracking system. Analysis of the Zwick data and the camera data revealed a significantly higher stability after 2S osteosynthesis compared to 1S and HCS treatment (Zwick data: p = 0.021, camera data: p < 0.001), while visible screw loosening showed a superiority of the 2S only over HCS (p = 0.038). The developed apparatus allowed the dynamic study of the atlantoaxial joint with a high approximation to physiological conditions. The results suggest a superiority of the 2S over the 1S and HCS in biomechanical stability in the treatment of type II odontoid fractures.
Keywords: odontoid fractures; biomechanical study; osteosynthesis