Recommendations for iliosacral screw placement in dysmorphic sacrum based on modified in‐out‐in corridors

Abstract

(1) Can iliosacral osseous corridor diameters in sacral dysmorphism be enlarged by in‐out‐in screw placement at the posterior iliosacral recessus? (2) Are lumbosacral transitional vertebra (LSTV) the anatomical cause for sacral dysmorphism? (3) Are there sex‐specific differences in sacral dysmorphism? 594 multislice CT scans were screened for sacral dysmorphism and 55 data‐sets selected. Each pelvis was segmented manually and cylindrical iliosacral corridors (on the level of S1 and S2 vertebra) were semi‐automatically determined. Corridor trajectories, −diameters and −lengths were measured. LSTV (Castellvi‐type IIIb and IV) were found in 3 of 55 pelves and these lumbosacral variations are therefore not the anatomical basis for sacral dysmorphism. The prevalence of transsacral osseous corridors with diameters of <7.5 mm in axial CT images correlates with qualitative and quantitative criteria of sacral dysmorphism. Enlarging the osseous corridor diameters by penetration of the posterior iliosacral recessus increase the safe corridor diameters (females versus males) by 26% versus 15% at the level of S1‐ and 50% versus 48% at the level of S2‐vertebra. Sex‐specific differences for both corridors (osseous and in‐out‐in) were only found for the osseous corridor diameters at the level of S1 vertebra, being smaller in females (females versus males: 13.3 ± 3.6 mm versus 15.5 ± 3.8 mm, p = 0.04). Dysmorphic sacra can be reliably detected on standard axial CT slice images. Modified in‐out‐in corridors on the level of S1‐vertebra allow screw placement in all patients, but is still demanding compared to non‐dysmorphic sacra, due to the oblique corridor axis. Recommendations for intraoperative orientation for oblique screw placement are defined. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res

Safety and efficacy of 2D-fluoroscopy-based iliosacral screw osteosynthesis: results of a retrospective monocentric study

“…Preoperative analysis and planning are indispensable for safe screw placement. On conventional X-rays and axial, coronal and oblique CT-pictures, the individual anatomy of the upper sacrum and ideal pathway of the screws must be determined, for which planning tools and recommendations exist [15,[25][26][27].…”

Percutaneous iliosacral screw and trans-iliac trans-sacral screw with single C-arm fluoroscope intensifier is a safe treatment for pelvic ring injuries

“…Sacral dysmorphism is defined as upper sacral segment dysplasia and have a higher risk in mal-positioned implant during percutaneously placing ISS and TITS 43 . In dysmorphic sacrum, narrow but adequate corridor for ISS at S1 segment can be found; however, it carries a considerable rate of malalignment 43 , 44 . Currently, it is believed that the use of a 3D navigation system during operation confers a lower rate of mal-positioned screw 44 , 45 .…”

Percutaneous posterior transiliac plate versus iliosacral screw fixation for posterior fixation of Tile C-type pelvic fractures

“…IS screw xation was implemented in patients who required posterior xation for Tile C-type pelvic ring injury. It is a simple and minimally invasive procedure, but it has limitations as it is di cult to perform in patients with sacral dysmorphism 15 . In addition, this approach has been associated with xation failure in patients with vertical sacral fractures 16 .…”

“…Although several techniques have been used to insert IS screws within a narrow safe zone, it is technically demanding, and there is potential for screw misplacement. Modi ed in-out-in corridors can enlarge safe zones, but shortening the length is inevitable, which results in weakening of the xation power 15 . As another option, the S3 segment of a dysmorphic sacra can serve as an additional site for screw insertion 20 .…”