Skip to main content
SpringerLink
Log in

The lateral entry point S2 alar-iliac (L-S2AI) screw: a preoperative computed tomography analysis of adult spinal deformity patients

  • Case Series
  • Published:
Spine Deformity Aims and scope Submit manuscript

Abstract

Purpose

To radiographically compare lateral entry point S2-alar-iliac (L-S2AI) screw with conventional S2AI (C-S2AI) and conventional iliac screw (CIS) lengths and trajectories.

Methods

Twenty-five preoperative CT scans of consecutive patients undergoing adult spinal deformity realignment surgery over a random 2-year period were analysed. Maximum in-bone length, caudal and lateral trajectories of CIS, C-S2AI, and L-S2AI screws were measured and compared using One-way ANOVA with Tukey’s post hoc tests. Multivariate logistic regression was performed to identify predictors of high screw length discrepancy between C-S2AI and L-S2AI.

Results

Potential screw length was longest for CIS, followed by L-S2AI, then C-S2AI (114.5 ± 8.3 mm vs 101.4 ± 9.6 mm vs 80.6 ± 5.9 mm, respectively) in all patients (p < 0.001). Actual screw lengths found both CIS and L-S2AI to be longer than C-S2AI (95.3 ± 8.5 mm and 93.4 ± 7.5 mm vs 82.1 ± 7.3 mm; p = 0.008 and 0.003). Potential lateral angulation was smallest for CIS, followed by L-S2AI, then C-S2AI (21.9 ± 7.0° vs 31.9 ± 7.1° vs 40.9 ± 6.7°, respectively) in all patients (p < 0.001). L-S2AI and C-S2AI had the same caudal angulation (24.9 ± 6.8°), which was smaller than CIS (30.8 ± 5.8°) in all patients (p < 0.001). Univariate, but not multivariate analysis, revealed that lumbar lordosis > 40° (OR 7.2, p = 0.041), diagnosis of degenerative spondylolisthesis (OR 10.5, p = 0.017), and > 7 instrumented levels (OR 2.6, p = 0.049) were significantly associated with high screw discrepancies.

Conclusion

The L-S2AI screw combines advantages of CIS and C-S2AI screws, which includes increased screw length, reduced lateral angulation, a low-profile screw head, ease of connection to proximal hardware, and the biomechanical advantage of a quadcortical purchase.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3

Similar content being viewed by others

Availability of data and material

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

Code availability

Not applicable.

References

  1. Transfeldt EE, Topp R, Mehbod AA et al (2010) Surgical outcomes of decompression, decompression with limited fusion, and decompression with full curve fusion for degenerative scoliosis with radiculopathy. Spine (Phila Pa 1976) 35:1872–1875. https://doi.org/10.1097/BRS.0b013e3181ce63a2

    Article  Google Scholar 

  2. Lee CH, Chung CK, Sohn MJ et al (2017) Short limited fusion versus long fusion with deformity correction for spinal stenosis with balanced de novo degenerative lumbar scoliosis: a meta-analysis of direct comparative studies. Spine (Phila Pa 1976) 42:E1126-e1132. https://doi.org/10.1097/brs.0000000000002306

    Article  Google Scholar 

  3. Guha D, Heary RF, Shamji MF (2015) Iatrogenic spondylolisthesis following laminectomy for degenerative lumbar stenosis: systematic review and current concepts. Neurosurg Focus 39:E9. https://doi.org/10.3171/2015.7.Focus15259

    Article  PubMed  Google Scholar 

  4. Lubelski D, Choma TJ, Steinmetz MP et al (2015) Perioperative medical management of spine surgery patients with osteoporosis. Neurosurgery 77(Suppl 4):S92-97. https://doi.org/10.1227/neu.0000000000000939

    Article  PubMed  Google Scholar 

  5. Yasuda T, Hasegawa T, Yamato Y et al (2016) Lumbosacral junctional failures after long spinal fusion for adult spinal deformity-which vertebra is the preferred distal instrumented vertebra? Spine Deform 4:378–384. https://doi.org/10.1016/j.jspd.2016.03.001

    Article  PubMed  Google Scholar 

  6. Nottmeier EW, Pirris SM, Balseiro S et al (2010) Three-dimensional image-guided placement of S2 alar screws to adjunct or salvage lumbosacral fixation. Spine J 10:595–601. https://doi.org/10.1016/j.spinee.2010.03.023

    Article  PubMed  Google Scholar 

  7. Hasan MY, Liu G, Wong HK et al (2020) Postoperative complications of S2AI versus iliac screw in spinopelvic fixation: a meta-analysis and recent trends review. Spine J 20:964–972. https://doi.org/10.1016/j.spinee.2019.11.014

    Article  PubMed  Google Scholar 

  8. O’Brien JR, Yu W, Kaufman BE et al (2013) Biomechanical evaluation of S2 alar-iliac screws: effect of length and quad-cortical purchase as compared with iliac fixation. Spine (Phila Pa 1976) 38:E1250-1255. https://doi.org/10.1097/BRS.0b013e31829e17ff

    Article  Google Scholar 

  9. Chang TL, Sponseller PD, Kebaish KM et al (2009) Low profile pelvic fixation: anatomic parameters for sacral alar-iliac fixation versus traditional iliac fixation. Spine (Phila Pa 1976) 34:436–440. https://doi.org/10.1097/BRS.0b013e318194128c

    Article  Google Scholar 

  10. Hoernschemeyer DG, Pashuck TD, Pfeiffer FM (2017) Analysis of the s2 alar-iliac screw as compared with the traditional iliac screw: does it increase stability with sacroiliac fixation of the spine? Spine J 17:875–879. https://doi.org/10.1016/j.spinee.2017.02.001

    Article  PubMed  Google Scholar 

  11. Schwab F, Ungar B, Blondel B et al (2012) Scoliosis Research Society-Schwab adult spinal deformity classification: a validation study. Spine (Phila Pa 1976) 37:1077–1082. https://doi.org/10.1097/BRS.0b013e31823e15e2

    Article  Google Scholar 

  12. Hey HWD, Tan KA, Chin BZ et al (2019) Comparison of whole body sagittal alignment during directed vs natural, relaxed standing postures in young, healthy adults. Spine J 19:1832–1839. https://doi.org/10.1016/j.spinee.2019.06.017

    Article  PubMed  Google Scholar 

  13. Shen FH, Mason JR, Shimer AL et al (2013) Pelvic fixation for adult scoliosis. Eur Spine J 22(Suppl 2):S265-275. https://doi.org/10.1007/s00586-012-2525-3

    Article  PubMed  Google Scholar 

  14. Tsuchiya K, Bridwell KH, Kuklo TR et al (2006) Minimum 5-year analysis of L5–S1 fusion using sacropelvic fixation (bilateral S1 and iliac screws) for spinal deformity. Spine (Phila Pa 1976) 31:303–308. https://doi.org/10.1097/01.brs.0000197193.81296.f1

    Article  Google Scholar 

  15. Enercan M, Kahraman S, Gokcen B et al (2014) Radiological outcomes and complications of S2 alar iliac fixation in adult patients with osteoporotic spine. Poster presented at Euro Spine

  16. Tavares Junior MCM, de Souza JPV, Araujo TPF et al (2019) Comparative tomographic study of the S2-alar-iliac screw versus the iliac screw. Eur Spine J 28:855–862. https://doi.org/10.1007/s00586-018-5806-7

    Article  PubMed  Google Scholar 

  17. Weisenthal BM, Doss DJ, Henry AL et al (2019) Optimal trajectory and length of S2 alar iliac screws: a 3-dimensional computed-aided design study. Clin Spine Surg 32:E335-e339. https://doi.org/10.1097/bsd.0000000000000837

    Article  PubMed  Google Scholar 

  18. Lee SH, Jin W, Kim KT et al (2011) Trajectory of transsacral iliac screw for lumbopelvic fixation: a 3-dimensional computed tomography study. J Spinal Disord Tech 24:151–156. https://doi.org/10.1097/BSD.0b013e3181e7c120

    Article  PubMed  Google Scholar 

  19. Kwan MK, Jeffry A, Chan CY et al (2012) A radiological evaluation of the morphometry and safety of S1, S2 and S2-ilium screws in the Asian population using three dimensional computed tomography scan: an analysis of 180 pelvis. Surg Radiol Anat 34:217–227. https://doi.org/10.1007/s00276-011-0919-2

    Article  PubMed  Google Scholar 

  20. Lin JD, Tan LA, Wei C et al (2018) The posterior superior iliac spine and sacral laminar slope: key anatomical landmarks for freehand S2-alar-iliac screw placement. J NeuroSurg 29:429. https://doi.org/10.3171/2018.3.Spine171374

    Article  Google Scholar 

  21. Liu G, Hasan MY, Wong HK (2018) Subcrestal iliac-screw: a technical note describing a free hand, in-line, low profile iliac screw insertion technique to avoid side-connector use and reduce implant complications. Spine (Phila Pa 1976) 43:E68-e74. https://doi.org/10.1097/brs.0000000000002239

    Article  Google Scholar 

  22. Ha KY, Lee JS, Kim KW (2008) Degeneration of sacroiliac joint after instrumented lumbar or lumbosacral fusion: a prospective cohort study over five-year follow-up. Spine (Phila Pa 1976) 33:1192–1198. https://doi.org/10.1097/BRS.0b013e318170fd35

    Article  Google Scholar 

  23. Unoki E, Miyakoshi N, Abe E et al (2017) Sacroiliac joint pain after multiple-segment lumbar fusion: a long-term observational study-Non-fused sacrum vs. fused sacrum. Spine Surg Relat Res 1:90–95. https://doi.org/10.22603/ssrr.1.2016-0010

    Article  PubMed  PubMed Central  Google Scholar 

  24. Unoki E, Miyakoshi N, Abe E et al (2019) Sacropelvic fixation with S2 alar iliac screws may prevent sacroiliac joint pain after multisegment spinal fusion. Spine (Phila Pa 1976) 44:E1024-e1030. https://doi.org/10.1097/brs.0000000000003041

    Article  Google Scholar 

  25. Mardam-Bey SW, Beebe MJ, Black JC et al (2016) The effect of transiliac-transsacral screw fixation for pelvic ring injuries on the uninjured sacroiliac joint. J Orthop Trauma 30:463–468. https://doi.org/10.1097/bot.0000000000000622

    Article  PubMed  Google Scholar 

Download references

Acknowledgements

Both H.W.D. Hey and M.R.D. Ramos made equal contributions to the manuscript and can be regarded as first authors

Funding

No funding was received for conducting this study.

Author information

Author notes

  1. Hwee Weng Dennis Hey and Miguel Rafael David Ramos are shared first authorship.

Authors and Affiliations

  1. Department of Orthopaedic Sugery, National University Hospital, National University Health System, 1E Kent Ridge Road, NUHS Tower Block Level 11, Singapore, 119228, Singapore

    Hwee Weng Dennis Hey, Miguel Rafael David Ramos, Hui Wen Tay, Shuxun Lin, Ka-Po Gabriel Liu & Hee-Kit Wong

Authors
  1. Hwee Weng Dennis Hey
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Miguel Rafael David Ramos
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Hui Wen Tay
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Shuxun Lin
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Ka-Po Gabriel Liu
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Hee-Kit Wong
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

Conception or design: HWDH, MRDR, KPGL, HKW. Acquisition of data: HWDH, MRDR. Analysis and interpretation of data: HWDH, MRDR, HWT, SXL. Drafting of manuscript: HWDH, MRDR, HWT, SXL. Critical revision of manuscript for important intellectual content: HWDH, MRDR, KPGL, HKW. Supervision: HWDH. Made substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data; or the creation of new software used in the work: HWDH, MRDR, HWT, SXL, KPGL, HKW. Drafted the work or revised it critically for important intellectual content: HWDH, MRDR, HWT, SXL, KPGL, HKW. Approved the version to be published: HWDH, MRDR, HWT, SXL, KPGL, HKW. Agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved: HWDH, MRDR, HWT, SXL, KPGL, HKW.

Corresponding author

Correspondence to Hwee Weng Dennis Hey.

Ethics declarations

Conflict of interest

The authors have no relevant financial or non-financial interests to disclose.

Ethics approval

Approval was obtained from the local ethics board.

Informed consent

No consent was required for this radiographic study.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Hey, H.W.D., Ramos, M.R.D., Tay, H.W. et al. The lateral entry point S2 alar-iliac (L-S2AI) screw: a preoperative computed tomography analysis of adult spinal deformity patients. Spine Deform 10, 669–678 (2022). https://doi.org/10.1007/s43390-021-00462-9

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s43390-021-00462-9

Keywords

Search

Navigation