Browsing by Author "AlSharhan, Rashid"

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Determining anatomically-safe corridors for placement of lateral mass screws in the first cervical vertebra of the Emirati population – a CT study
(Springer Science and Business Media LLC, 2025-01-15) Suresh, Dineshwary; Naidoo, Nerissa; AlSharhan, Rashid; Lakshmanan, Jeyaseelan; Prithishkumar, Ivan James
The first cervical vertebra (C1) is atypical in shape and bears a complex relationship with important neurovascular structures such as the vertebral artery and cervical spinal cord which are at risk of injury during misplaced screw fixation of C1. Placement of screws into the lateral mass of C1 vertebra is performed for stabilization of the craniovertebral junction. The objective of this study was to describe ideal screw dimensions, precise entry points, safe bony corridors, and ideal trajectories for placement of lateral mass screws in the Emirati population. CT scans of 160 Emirati patients (> 18 years) were studied and variables relevant to lateral mass screw fixation were measured. Screw entry at the centre of lateral mass, below its junction with the posterior arch, allowed straight screws of lengths of 20 mm and 19.5 mm in Emirati males and females, respectively. A medial angulation of 20° in males and 15° in females allowed maximum bone purchase. Screw entry at the junction of medial margin of posterior arch and lateral mass allowed straight screws of length 18 mm in both males and females. We recommend safe cephalic angulations of 19° and 16°in males and females, respectively. The mean critical width was 7.6 mm in males and 6.8 mm in females which would safely permit screws of width 4.0 mm. Pre-operative knowledge of the above dimensions would help in greater precision, minimizing the risk of injury to neurovascular structures in the vicinity of C1 lateral mass.
Feasibility of transpedicular screw placement through the posterior arch of C1: A CT study in the Emirati population
(Elsevier BV, 2025-06) Prithishkumar, Ivan James; Suresh, Dineshwary; Naidoo, Nerissa; AlSharhan, Rashid; Lakshmanan, Jeyaseelan
Background: Instrumentation of the lateral mass of first cervical vertebra (C1) is required in atlantoaxial instability. C1 bears a complicated relationship with adjacent neurovascular structures such as the vertebral artery and cervical spinal cord, which are at risk of injury in a misplaced screw. The objective of this study was to look at the feasibility of transpedicular screw placement into the C1 lateral mass with entry through the posterior arch. Methods: Computed tomography images of the cervical spine in 160 adults (>18 years) who are natives of the United Arab Emirates (UAE) (M = 80; F = 80) were reviewed. Morphometric parameters relevant to pedicle screw fixation via the posterior arch were studied. Results: Mean intraosseous distance from screw entry point in the posterior arch to the anterior cortex of lateral mass following a straight course without any inclination was 28.0 mm in males and 29.0 mm in females, allowing a safe distance of 3.2 mm from the foramen transversarium laterally and 9.0 mm from the vertebral canal medially. A medial inclination of 18◦ in males and 14◦ in females allows for increased bone purchase. Mean height of the pedicle at its junction with lateral mass was 5.6 mm in both sexes. However, the mean height of the posterior arch at the vertebral artery groove was 3.3 ± 0.4 mm in males and 3.1 ± 0.4 mm in females. Conclusion: We recommend placement of 3.5/4.0 mm screws using the notching technique, of length 28–30 mm with a slight medial angulation of 15◦ for increased bone purchase and greater stability of fixation.