Published in:
01-10-2016 | Original Article • SPINE - CERVICAL
Applied anatomy of screw placement via the posterior arch of the atlas and anatomy-based refinements of the technique
Published in: European Journal of Orthopaedic Surgery & Traumatology | Issue 7/2016
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Purpose
To present a method of posterior arch and lateral mass screw (PALMS) insertion and to prove its feasibility.
Methods
Four formalin-fixed specimens and 40 macerated atlas vertebras were used to describe the relevant anatomy. The height of the posterior arch was measured on 42 consecutive patients using standard CT of the cervical spine. The operative technique and the special CT reconstructions used for preoperative planning are described. Eight patients underwent posterior fixation using this technique.
Results
We described the relevant anatomy and important anatomical landmarks of the posterior arch of the atlas. PALMS placement was modified according to these anatomical findings. Fifteen PALMSs were placed in eight patients using this technique without vascular or neural injury.
Conclusion
It is feasible to place PALMS using the described technique. CT angiography is of crucial importance for preoperative planning using the described special reconstructions. The arch posterior to the lateral mass (APLM) is defined as the bone stock situated posterior to the lateral mass, respecting its convergence. The ideal entry point for a PALMS is on the APLM above the center of the converging lateral mass. A complete or incomplete ponticulus posticus and a retrotransverse foramen or groove can be used as an accessory landmark to refine the entry point.