The Influence of Radiographic Parameter on the S2 Alar-Iliac Screw Virtual Trajectory in Degenerative Lumbar Scoliosis Patients: A Computed Tomography Study

Abstract

Objective: S2 alar-iliac (S2AI) screw had been widely used in the pelvic fusion for degenerative lumbar scoliosis (DLS) patients. However, whether S2AI screw trajectory was influenced by sagittal profile in DLS patients had not been comprehensively investigated. The objective of this study was to evaluate the associations between the optimal S2 alar-iliac (S2AI) screw trajectory and sagittal spinopelvic parameters in DLS patients.

Methods: Computed tomography (CT) scans of pelvis were performed in 47 DLS patients for three-dimensional reconstruction of S2AI screw trajectory from September 2019 to November 2021. Five S2AI screw trajectory parameters were measured in CT reconstruction images, including: 1) angle in the transverse plane (Tsv angle); 2) angle in the sagittal plane (Sag angle); 3) maximal screw length; 4) screw width; and 5) skin distance. The lumbar Cobb angle, lumbar apical vertebral translation (AVT); global kyphosis (GK); thoracic kyphosis (TK); lumbar lordosis (LL); sagittal vertical axis (SVA); sacral slope (SS); pelvic tilt (PT); and pelvic incidence (PI) were measured in standing X-ray films of the whole spine and pelvis.

Results: Both Tsv angle and Sag angle had significant positive associations with SS (p < 0.05) but negative associations with both PT (p < 0.05) and LL (p < 0.05) in all cases. Patients with SS less than 15° had both smaller Tsv angle and Sag angle than those with SS equal to or more than 15° (p < 0.05). The decreased LL would lead to the backward rotation of the pelvis, resulting in a more cephalic and less divergent trajectory of S2AI screw in DLS patients.

Conclusions: For DLS patients with lumbar kyphosis, spine surgeons should avoid both excessive Tsv and Sag angles for S2AI screw insertion, especially when using free-hand technique.

Keywords

S2 Alar-Iliac Screw / Sagittal / Scoliosis / Spino-Pelvic

References

[1] GulerUO, CetinE, YamanO, Pellise F, CasademutAV, SabatMD, et al. Sacropelvic fixation in adult spinal deformity (ASD); a very high rate of mechanical failure. Eur Spine J. 2015;24(5):1085–1091.

[2] O'BrienJR, YuW, KaufmanBE, Bucklen B, SalloumK, KhalilS, et al. Biomechanical evaluation of S2 alar-iliac screws: effect of length and quad-cortical purchase as compared with iliac fixation. Spine (Phila Pa 1976). 2013;38:E1250–E1255.

[3] PerraJH. Techniques of instrumentation in long fusions to the sacrum. Orthop Clin North Am. 1994;25(2):287–299.

[4] PhillipsJH, Gutheil JP, KnappRD. Iliac screw fixation in neuromuscular scoliosis. Spine (Phila Pa 1976). 2007;32:1566–1570.

[5] ShillingfordJN, Laratta JL, TanLA. The free-hand technique for S2-alar-iliac screw placement: a safe and effective method for sacropelvic fixation in adult spinal deformity. J Bone Joint Surg Am. 2018;21(100):334–342.

[6] ZhuF, BaoHD, YuanS, Wang B, QiaoJ, ZhuZZ, et al. Posterior second sacral alar iliac screw insertion: anatomic study in a Chinese population. Eur Spine J. 2013;22(7):1683–1689.

[7] ChangTL, Sponseller PD, KebaishKM, FishmanEK. Low-profile pelvic fixation: anatomic parameters for sacral alar-iliac fixation versus traditional iliac fixation. Spine (Phila Pa 1976). 2009;34:436–440.

[8] O'BrienJR, YuW, BhatnagarR, Sponseller P, KebaishKM. An anatomic study of the S2 iliac technique for lumbopelvic screw placement. Spine (Phila Pa 1976). 2009;34:439–442.

[9] Tavares JuniorMCM, de Souza JPV, AraujoTPF, MarconRM, Cristante AF, de Barros FilhoTEP, et al. Comparative tomographic study of the S2-alar-iliac screw versus the iliac screw. Eur Spine J. 2019;28:855–862.

[10] LanzieriCF, HilalSK. Computed tomography of the sacral plexus and sciatic nerve in the greater sciatic foramen. AJR Am J Roentgenol. 1984;143:165–168.

[11] WeisenthalBM, DossDJ, HenryAL, Stephens BF. Optimal trajectory and length of S2 alar iliac screws: a 3-dimensional computed-aided design study. Clin Spine Surg. 2019;32:E335–E339.

[12] PhanK, LiJ, GiangG, Teng I, PhanS, ChangN, et al. A novel technique for placement of sacro-alar-iliac (S2AI) screws by K-wire insertion using intraoperative navigation. J Clin Neurosci. 2017;45:324–327.

[13] YilmazE, Abdul-Jabbar A, TawfikT, IwanagaJ, Schmidt CK, ChapmanJ, et al. S2 alar-iliac screw insertion: technical note with pictorial guide. World Neurosurg. 2018;113:e296–e301.

[14] HasanMY, LiuG, WongH-K, Tan J-H. Postoperative complications of S2AI versus iliac screw in spinopelvic fixation: a meta-analysis and recent trends review. Spine J. 2020;20:964–972.

[15] ShillingfordJN, Laratta JL, ParkPJ, LombardiJM, Tuchman A, SaifiC, et al. Human versus robot: a propensity-matched analysis of the accuracy of free hand versus robotic guidance for placement of S2 alar-iliac (S2AI) screws. Spine (Phila Pa 1976). 2018;43:E1297–E1304.

[16] FangT, RussoGS, SchroederGD, Kepler CK. The accurate free-hand placement of S2 alar iliac (S2AI) screw. Clin Spine Surg. 2020;33:102–103.

[17] ParkJH, HyunSJ, KimKJ, Jahng TA. Free hand insertion technique of S2 sacral alar-iliac screws for spino-pelvic fixation: technical note, acadaveric study. J Korean Neurosurg Soc. 2015;58:578–581.

[18] VivaceBJ, Laratta JL, GumJL, ShillingfordJN, DimarJR II, GlassmanSD, et al. Pelvic parameters directly influence ideal S2 alar-iliac (S2AI) screw trajectory. N Am Spine Soc J. 2020;2:100014.

[19] de Sousa PontesMD, Ismael LK, FranciscoLA, HerreroCFPDS. Description of the sacropelvic parameters measurement method for S2-alar iliac screw insertion. Rev Bras Ortop (Sao Paulo). 2020;55:702–707.

[20] GottfriedON, DaubsMD, PatelAA, Dailey AT, BrodkeDS. Spinopelvic parameters in postfusion flatback deformity patients. Spine J. 2009;9:639–647.

[21] RoussoulyP, Pinheiro-Franco JL. Biomechanical analysis of the spino-pelvic organization and adaptation in pathology. Eur Spine J. 2011;20:609–618.

[22] LafageV, SchwabF, PatelA, Hawkinson N, FarcyJP. Pelvic tilt and truncal inclination: two key radiographic parameters in the setting of adults with spinal deformity. Spine (Phila Pa 1976). 2009;34:E599–E606.

[23] BarreyC, Roussouly P, PerrinG, le HuecJC. Sagittal balance disorders in severe degenerative spine. Can we identify the compensatory mechanisms? Eur Spine J. 2011;20:626–633.

[24] KukloTR, PotterBK, SchroederTM, O'Brien MF. Comparison of manual and digital measurements in adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2006;31:1240–1246.

RIGHTS & PERMISSIONS

2024 2024 The Authors. Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.