Is C1 lateral mass screw placement safe for the Chinese, Indians, and Malays? An analysis of 180 computed tomography scans

• Published in: Journal of orthopaedic surgery (Hong Kong) Vol. 25; no. 1; p. 2309499017692683
• Main Authors: Lee, CK, Tan, TS, Chan, CYW, Kwan, MK
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.01.2017; Sage Publications Ltd; SAGE Publishing
• Subjects: Adult; Aged; Authorship; Bone Screws; Carotid arteries; Cervical Atlas - diagnostic imaging; Cervical Atlas - surgery; China - ethnology; Feasibility Studies; Female; Humans; Imaging, Three-Dimensional; India - ethnology; Malaysia - epidemiology; Male; Measurement techniques; Medical imaging; Middle Aged; Population; Retrospective Studies; Spinal Diseases - diagnosis; Spinal Diseases - ethnology; Spinal Diseases - surgery; Spinal Fusion - methods; Tomography, X-Ray Computed - methods; Veins & arteries; Young Adult; C1 morphometry; C1 lateral mass screw safety; ponticulus posticus; Chinese; Indian; internal carotid artery; Malay
• ISSN: 1022-5536; 2309-4990; 2309-4990
• DOI: 10.1177/2309499017692683

Introduction: C1 lateral mass (C1LM) screw is a common procedure in spine surgery. However, related studies are lacking in Asia. We aim to determine the safety of C1LM screw for the Chinese, Indians, and Malays. Methods: Three-dimensional computed tomographies of 180 subjects (60 from each ethnic) were analyzed. The length and angulations of C1LM screw and the location of internal carotid artery (ICA) in relation to C1LM were assessed and classified according to the classification by Murakami et al. The incidence of ponticulus posticus (PP) was determined and the differences among the population of these three ethnics were recorded. Results: The average base length was 8.5 ± 1.4 mm. The lengths within the lateral mass were between 14.7 ± 1.6 mm and 21.7 ± 2.3 mm. The prevalence of PP was 8.3%. 55.3% (199) of ICA were located in zone 0, 38.3% (138) in zone 1-1, 6.4% (23) in zone 1-2, and none in zone 1-3 and zone 2. The average angulation from the entry point to the ICA was 8.5° ± 6.4° laterally. The mean distance of ICA from C1 anterior cortex was 3.7 ± 1.7 mm (range: 0.6∼11.3). There was no difference in distribution of ICA in zone 1 among the three population (Chinese–47%, Indians–61%, and Malays–53%; p > 0.05). Conclusions: No ICA is located medial to the entry point of C1LM screw. If bicortical purchase of C1LM screw is needed, screw protrusion of less than 3 mm or medially angulated is safe for ICA. The incidence of PP is 8.3% with higher prevalence among the Indian population.