OBJECTIVES: The halo ring can be applied in children, through skeletal traction or a halo vest device, to treat many cervical spine pathologies, including traumatic injuries and pathologies related to deformities. However, the procedure is associated with various complications, such as infection, pin loosening, and respiratory and neurological problems. Although widely studied in adults, the best pin insertion site in children and the correlations of pin insertion sites with outcomes and complications have not been completely elucidated. This study aimed to determine alternative pin placement sites based on a morphological analysis of the infant skull by computerized tomography (CT). METHODS: An analytical-descriptive study was performed using 50 CT scans from children. The Wilcoxon and Friedman tests were used. RESULTS: A linear and directly proportional relation was found between cranial thickness and patient age. The average thicknesses of the anterior points across all ages analyzed ranged from 4.16 mm to 4.98 mm. The thicknesses of the posterior points varied from 3.94 mm to 4.27 mm. Within each age range, points 1 cm above the standard insertion sites had thicknesses similar to those of the standard sites, and points 2 cm above the standard insertion sites had thicknesses greater than those of the standard sites. CONCLUSIONS: The cranial thickness at all points increases linearly with age. Points 1 and 2 cm above the standard insertion sites are viable alternatives for the placement of halo pins. Preoperative CT can aid in choosing the best positioning sites for pins in the skull.

RESUMO Objetivos: A fixação lombossacra apresenta problemas na sua artrodese, devido principalmente à pseudoartrose. Os parafusos de ilíaco minimizam esse problema, contudo mostram problemas na ferida operatória. Já o parafuso de S2-Alar-Ilíaco (S2AI) apresenta menor índice dessas complicações. As diferenças anatômicas entre as populações e os sexos analisados na literatura justificam o estudo da técnica de parafuso de S2AI em mulheres brasileiras. Métodos: Foram analisadas 14 tomografias de mulheres adultas por quatro avaliadores. Resultados: O comprimento ósseo médio foi de 131,8 mm, maior diâmetro ósseo foi de 22,6 mm, o menor diâmetro ósseo de 22,6 mm. Conclusões: Os dados apresentados são compatíveis com a literatura e podem ajudar os cirurgiões de coluna na escolha do melhor implante e na técnica cirúrgica. Nível de Evidência I; Investigação de um exame para diagnóstico (investigação anatômica).

ABSTRACT Objective: Lumbosacral fixation presents problems in its arthrodesis, mainly due to pseudoarthrosis. Iliac screws minimize this problem, however, they show problems in the operative wound. The S2-Alar-iliac (S2AI) screw presents a lower rate of these complications. The anatomical differences between the populations and the sexes analyzed in the literature justify the study of the S2AI screw technique in Brazilian women. Methods: A total of 14 adult female CT scans were analyzed by 4 evaluators. Results: The mean bone length was 131.8 mm, the largest bone diameter was 22.6 mm, and the smallest bone diameter was 22.6 mm. Conclusions: The data presented are compatible with the literature and may assist spine surgeons in choosing the best implant and surgical technique. Level of Evidence I; Diagnostic Studies — Investigating a Diagnostic Test (anatomical investigation).

RESUMEN Objetivos: La fijación lumbosacra presenta problemas en la artrodesis, principalmente a causa de la pseudoartrosis. Los tornillos del ilíaco minimizan este problema, pero causan problemas en la herida quirúrgica. El tornillo S2-Alar-ilíaco (S2AI) muestra un menor índice de estas complicaciones. Las diferencias anatómicas entre las poblaciones y los sexos analizados en la literatura justifican el estudio de la técnica del tornillo S2AI en mujeres brasileñas. Métodos: Cuatro evaluadores analizaron 14 tomografías de mujeres adultas. Resultados: La longitud ósea media fue de 131,8 mm, el mayor diámetro fue de 22,6 mm, el menor diámetro óseo fue 22,6 mm. Conclusiones: Los datos presentados son compatibles con la literatura y pueden ayudar a los cirujanos de columna en la elección del mejor implante y técnica quirúrgica. Nivel de Evidencia I; Estudios de diagnósticos - Investigación de un examen para diagnóstico (investigación anatómica).