The relationship of the posterior iliac interval and the S1 screw trajectory. (May 2023)

• Record Type: Journal Article
• Authors: K.H. Ho, Benjamin; Jackson, Lachlan; Farsakh, Ameen; Kam, Jeremy; Ball, Jonathon
• Is Part Of: Journal of clinical neuroscience. Volume 111(2023)
• Page Start: 32
• Page End: 36
• Publication Date: 2023-05
• Subjects: Posterior iliac interval -- Pedicle screw trajectory -- S1 screw; Brain -- Surgery -- Periodicals; Neurosciences -- Periodicals; Nervous system -- Surgery -- Periodicals; Brain -- surgery -- Periodicals; Neurosurgical Procedures -- Periodicals; Neurosciences -- Periodicals; Electronic journals; 616.8
• DOI: 10.1016/j.jocn.2023.02.006
• Languages: English
• ISSNs: 0967-5868

Abstract

Highlights: Substantiation of the posterior iliac interval (PII) and the S1 screw trajectory with a real-life in-vivo observational study as previously theorised by Robertson et al. where pre-operative CT scans were used to simulate S1 screw angulation to describe a 'safe zone' of entry. PII was found to be greater in females than males. A wider PII was found to be associated with a more angulated S1 screw. This study reveals the need for further investigation into the bio-mechanical properties of S1 screw angulation and another parameter to be considered when performing lumbosacral fusion. Abstract: Introduction: Surgical fixation is widely practised in the management of spinal deformity. S1 screws are commonly incorporated in lumbosacral fusions and can be performed in both open and percutaneous techniques. However, their entry point is determined by the position of the pedicle as well as the posterior iliac interval (PII), as it creates an impedance for screw angulation. A wider angle screw has the potential to achieve a greater length and thus strength versus a narrow screw angle insertion due to risk of anterior breach. Methods: A retrospective analysis of 50 consecutive patients between July 2018 andDecember 2021 undergoing lumbo-sacral fusion with include S1 screw insertion from a single institution and surgeon. The age, screw angles, and the posterior iliac intervals were measured. Results: The patients ranged from age 27 to 83 years old (mean 64.7) with a posterior iliac interval (PII) ranging from 7.76 to 12.62 cm (mean 10.24) and the average S1 screw angle on the right was 76.01 degrees (range 59.37 to 88.48) and on the left 74.37 degrees (range 59.75 to 87.47 degrees). Applying the Pearson Correlation co-efficient, a wider PII correlated with a more angulated screw entry (P < 0.05). Conclusion: As expected, a wider PPI is significantly associated with a more angulated S1 screw trajectory and may have implication on patient biomechanics in lumbo-sacral fusion constructs.