The Free-Hand Technique for S2-Alar-Iliac Screw Placement

Shillingford, Jamal N.; Laratta, Joseph L.; Tan, Lee A.; Sarpong, Nana O.; Lin, James; Fischer, Charla R.; Lehman, Ronald A.; Kim, Yongjung J.; Lenke, Lawrence G.

doi:10.2106/jbjs.17.00052

Cited by 68 publications

(45 citation statements)

References 22 publications

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“…This result is consistent with a previous study from Zhu et al, a radiographic study assessing optimal S2AI screw placement and presented that CA in females have 4 to 5 degrees more caudal trajectory compared with males [15]. But a study from Shillingford showed there is no signi cant differences in the CA or MA between females and males [2]. This study showed there is no difference in MA between males and females with an average 40° (39.75°±2.40° vs 40.38 ± 3.58°).…”

Section: Discussionsupporting

confidence: 92%

“…Spinopelvic xation plays an integral role in achieving solid osseous fusion across the lumbosacral junction, especially in deformity procedures requiring substantial correction or long-segment constructs. [1,2]There are several techniques for spinopelvic xation that include Galveston technique [3], iliac screws (iliac bolts), iliosacral screws, and S2 alar iliac screws (S2AI) technique [1,4] Compared with other pelvic…”

Section: Introductionmentioning

confidence: 99%

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The three-dimensional printed template guided technique for S2AI screw placement and a comparison with freehand technique

Zhou

Zeng

et al. 2020

Preprint

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Background Sacropelvic fixation continues to present challenges when involved in the adult spinal deformity correction. The S2 alar iliac (S2AI) fixation is commonly used in sacropelvic fixation. Several techniques, including intraoperative navigation and freehand technique, were used for S2AI screws placement. The aim of this study is to analyze the anatomic parameters for S2AI screw trajectory in Asian population and introduce a novel technique described as three-dimensional printed template guided technique (TGT). Meanwhile, the accuracy and safety of this technique were compared with conventional freehand technique. Methods The S2AI trajectory parameters were measured in100 Asian adult volunteers. Parameters were compared between different genders. Forty-eight adult patients who underwent S2AI screw placement were reviewed, 28 patients received freehand technique and 20 patients received TGT technique. Postoperative CT was used to assess the accuracy of screw trajectory and cortex violation related complications were recorded. Results The cephalocaudal angles (CA), maximal length of screw pathway (ML), narrowest width of pathway within the iliar teardrop (NW), distance from the center of teardrop to sciatic notch(SD) and distance of the start point distal to S1 dorsal foramen(DD) showed significant gender-related difference (p<0.05). All 48 patients were placed S2AI screws bilaterally (40 screws in TGT vs 56 screws in freehand). One screw penetrated iliac cortex in TGT group but 10 screws penetrated iliac cortex in freehand group (3% vs 17.9%) (p<0.05). Conclusion Approximately 30-35° of cephalocaudal angle and 39°mediolateral angle are appropriate for S2AI screw placement in Asian patients. Either freehand or TGT technique is safe for S2AI screw placement. TGT technique is more accurate compared with conventional freehand technique. Trial registration This is a retrospective study. Key words Sacropelvic fixation, Second sacral alar iliac (S2AI) screw, three-dimensional printed template, freehand technique

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

The three-dimensional printed template guided technique for S2AI screw placement and a comparison with freehand technique

Zhou

Zeng

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…The screw head is low profile and connects directly with the spinal rod[ 2 ]. While initial reports documented safety and placement in both pediatric and adult spinal deformity patients, much of the recent literature regarding safety of placement using the S2AI technique has been published in adults[ 3 - 6 ]. Shillingford et al[ 3 ] report a free hand technique without intra-operative imaging that has a cortical breech rate of 7% posteriorly and 1% anteriorly.…”

Section: Introductionmentioning

confidence: 99%

“…While initial reports documented safety and placement in both pediatric and adult spinal deformity patients, much of the recent literature regarding safety of placement using the S2AI technique has been published in adults[ 3 - 6 ]. Shillingford et al[ 3 ] report a free hand technique without intra-operative imaging that has a cortical breech rate of 7% posteriorly and 1% anteriorly. Anterior perforation into the pelvis or inferior perforation into the sciatic notch can have catastrophic result given the neurovascular and visceral structures found in such locations[ 3 ].…”

Section: Introductionmentioning

confidence: 99%

“…Shillingford et al[ 3 ] report a free hand technique without intra-operative imaging that has a cortical breech rate of 7% posteriorly and 1% anteriorly. Anterior perforation into the pelvis or inferior perforation into the sciatic notch can have catastrophic result given the neurovascular and visceral structures found in such locations[ 3 ]. There may also be variations in anatomy, for example the relationship between the iliac wings and the pelvis.…”

Section: Introductionmentioning

confidence: 99%

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Intra-operative computed tomography guided navigation for pediatric pelvic instrumentation: A technique guide

Anari¹,

Cahill²,

Flynn³

et al. 2018

WJO

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Pelvic instrumentation for neuromuscular scoliosis has been part of neuromuscular scoliosis surgery since the era of the Luque Galveston construct. Unit Rod (Medtronic Sofamor-Danek, Nashville, TN) instrumentation brought with it the concept of cantilever correction by placing the implants in the pelvis and then gradually bringing the rod to the spine by sequentially tightening the sublaminar wires, with the goal of creating a level pelvis over a straight spine. More recently surgeons have utilized pedicle screw constructs in which the corrective strategies have varied. Challenges with pelvic fixation using iliac screws linked to the spinal rod have led to the development of the S2-alar-iliac technique (S2AI) in which the spinal rod connects to the pelvic screw. The screw is placed in the S2 ala, crosses the sacro-iliac joint and into the ilium through a large column of supra-acetabular bone. This column is the same area used for anterior inferior iliac spine external fixation frames used in trauma surgery. S2AI screw placement can be technically difficult and can require experienced radiology technologists to provide the appropriate views. Additionally, although the technique was originally described being placed via freehand technique with intra-operative flouroscopy, the freehand technique suffers from the anatomic anomalies present in the pelvis in neuromuscular scoliosis. As such, we prefer to place them using intra-operative navigation for all pediatric spinal deformity cases. Below in detail we report our intra-operative technique and an illustrative case example.

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Biomechanical investigation of S2 alar‐iliac screw and S1 pedicle screw fixation in the treatment of Denis type II sacral fractures

Zheng

Liu

Xiang

et al. 2022

Journal Orthopaedic Research

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Although S2 alar-iliac screw technique has been widely used in spinal surgery, its applicability to pelvic fractures is largely unknown. This study aimed to evaluate the biomechanical stability of S2 alar-iliac screw and S1 pedicle screw fixation in the treatment of Denis II sacral fractures. Twenty-eight artificial pelvic fracture models were treated with unilateral lumbopelvic fixation, sacroiliac screw fixation, S2 alar-iliac screw and S1 pedicle screw fixation, and S2 alar-iliac screw and contralateral S1 pedicle screw fixation (Groups 1-4, respectively; N = 7 per group). Each model was cyclically tested under increasing axial compression. Optical motion-tracking was used to assess relative displacement and gap angle, and the number of failure cycles. Relative displacement was significantly smaller in Group 3 than in Groups 1 (p = 0.004) and 4 (p < 0.001) but not significantly different between Groups 3 and 2 (p = 0.290). The gap angle in Group 3 was significantly smaller than that in Group 1 (p = 0.009) on the sagittal plane but significantly larger than that in Group 4 (p = 0.006) on the horizontal plane. A number of failure cycles was significantly higher in Group 3 than in Groups 1 (p = 0.002) and 4 (p = 0.004) but not significantly different between Groups 3 and 2 (p = 0.910). From a biomechanical perspective, S2 alar-iliac screw and S1 pedicle screw fixation can provide good stability in the treatment of Denis II sacral fractures.

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The Free-Hand Technique for S2-Alar-Iliac Screw Placement

Abstract: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Cited by 68 publications

References 22 publications

The three-dimensional printed template guided technique for S2AI screw placement and a comparison with freehand technique

The three-dimensional printed template guided technique for S2AI screw placement and a comparison with freehand technique

Intra-operative computed tomography guided navigation for pediatric pelvic instrumentation: A technique guide

Biomechanical investigation of S2 alar‐iliac screw and S1 pedicle screw fixation in the treatment of Denis type II sacral fractures

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