Lamina-guided lateral mass screw placement in the sub-axial cervical spine |
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Authors: | Edward Bayley Zergham Zia Robert Kerslake Zdenek Klezl Bronek M Boszczyk |
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Institution: | (1) Centre for Spinal Studies and Surgery, Queen’s Medical Centre, Nottingham, NG7 2UH, UK;(2) Department of Radiology, Queen’s Medical Centre, Nottingham, NG7 2UH, UK;(3) Department of Trauma and Orthopaedics, Royal Derby Hospital, Derby, DE22 3NE, UK; |
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Abstract: | Lateral mass (LM) screws are commonly used in posterior instrumentation of the cervical spine because of their perceived safety
over pedicle screws. A possible complication of cervical LM screw placement is vertebral artery injury or impingement. Several
screw trajectories have been described to overcome the risks of neurovascular injury; however, each of these techniques relies
on the surgeon’s visual estimation of the trajectory angle. As the reliability hereof is poorly investigated, alignment with
a constant anatomical reference plane, such as the cervical lamina, may be advantageous. The aim of this investigation was
to determine whether alignment of the LM screw trajectory parallel to the ipsilateral cervical lamina reliably avoids vertebral
artery violation in the sub-axial cervical spine. 80 digital cervical spine CT were analysed (40 female, 40 male). Exclusion
criteria were severe degeneration, malformations, tumour, vertebral body fractures and an age of less than 18 or greater than
80 years. Mean age of all subjects was 39.5 years (range 18–78); 399 subaxial cervical vertebrae (C3–C7) were included in
the study. Measurements were performed on the axial CT view of C3–C7. A virtual screw trajectory with parallel alignment to
the ipsilateral lamina was placed through the LM. Potential violation of the transverse foramen was assessed and the LM width
available for screw purchase measured. There was no virtual violation of the vertebral artery of C3–C7 with lamina-guided
LM screw placement. LM width available for screw purchase using this technique ranged from 5.2 to 7.4 mm. The sub-axial cervical
lamina is a safe reference plane for LM screw placement. LM screws placed parallel to the ipsilateral lamina find sufficient
LM width and are highly unlikely to injure the vertebral artery, even in bi-cortical placement. Placing LM screws parallel
to the lamina appears favourable over conventional techniques. |
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Keywords: | Lateral mass screw trajectory Surgical technique Subaxial cervical spine Vertebral artery injury Cervical spine anatomy |
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