Hyper-Selective Posterior Fusion is Recommended When the Modified S-Line is Positive in Lenke 5C Adolescent Idiopathic Scoliosis

Abstract

Objective: Postoperative coronal decompensation and less fusion level are dilemmas and the proper selective posterior fusion (SPF) strategy should be investigated. We proposed a parameter, modified S-line, and aimed to investigate if the modified S-line could predict postoperative coronal decompensation in patients with Lenke 5C adolescent idiopathic scoliosis (AIS).

Methods: This is a retrospective radiographic study and Lenke 5C AIS patients undergoing SPF during the period from September 2017 to June 2021 were included. The modified S-line was defined as the line linking the centers of the concave-side pedicles of the upper end vertebra (UEV) and lower end vertebra (LEV) at baseline. A modified S-line tilt to the right is established as modified S-line+ (UEV being to the right of the LEV). The patients were further categorized into two groups: the Cobb to Cobb fusion group and the Cobb-1 to Cobb fusion group. Outcomes including thoracic Cobb angle, TL/L Cobb angle, coronal balance, upper instrumented vertebra (UIV) translation, lower instrumented vertebra (LIV) translation, UIV tilt, LIV tilt, LIV disc angle, thoracic apical vertebral translation, lumbar apical vertebral translation (L-AVT), L-T AVT ratio, L-T Cobb were measured at baseline, immediately after surgery, and the last follow-up. Radiographic parameters and the incidence of both proximal and distal decompensation between the two groups were compared by chi-square test.

Results: Among 92 patients, 48 were modified S-line+ and 44 were modified S-line-. Modified S-line+ status was identified as a risk factor for postoperative proximal decompensation (p = 0.005) during follow-up. In Cobb to Cobb group, a higher occurrence of proximal decompensation in individuals with modified S-line+ status (p = 0.001) was confirmed. Also, in the Cobb to Cobb group with baseline modified S-line+ status, patients presenting decompensation showed a significantly larger baseline of the UIV tilt and postoperative disc angle below the lower instrumented vertebra. However, In Cobb-1 group, the incidence of decompensation after surgery showed no association with baseline modified S-line tilt status (p = 0.815 and 0.540, respectively).

Conclusion: The modified S-line could serve as an important parameter in surgical decision-making for Lenke 5C AIS patients. Cobb to Cobb SPF is not recommended with a modified S-line+ status, and the Cobb-1 to Cobb fusion may serve as a potential alternative.

Keywords

Adolescent Idiopathic Scoliosis / Decompensation / Lower Instrumented Vertebra / Spinal Deformity / Upper End Vertebra

References

[1] GeckMJ, Rinella A, HawthorneD, MacagnoA, Koester L, SidesB, et al. Comparison of surgical treatment in Lenke 5C adolescent idiopathic scoliosis: anterior dual rod versus posterior pedicle fixation surgery: a comparison of two practices. Spine (Phila Pa 1976). 2009;34(18):1942–1951.

[2] WangY, Bünger CE, ZhangY, WuC, LiH, DahlB, et al. Lowest instrumented vertebra selection for Lenke 5C scoliosis. Spine (Phila Pa 1976). 2013;38:E894–E900.

[3] HiraseT, LingJF, HaghshenasV, Thirumavalavan J, DongD, HansonDS, et al. Anterior versus posterior spinal fusion for Lenke type 5 adolescent idiopathic scoliosis: a systematic review and meta-analysis of comparative studies. Spine Deform. 2022;10(2):267–281.

[4] O'DonnellC, Michael N, PanX, EmansJ, GargS, EricksonM. Anterior spinal fusion and posterior spinal fusion both effectively treat Lenke type 5 curves in adolescent idiopathic scoliosis: a multicenter study. Spine Deform. 2018;6:231–240.

[5] LiJ, ZhaoZ, TsengC, Zhu Z, QiuY, LiuZ. Selective fusion in Lenke 5 adolescent idiopathic scoliosis. World Neurosurg. 2018;118:e784–e791.

[6] LiJ, HwangSW, ShiZ, YanN, YangC, Wang C, et al. Analysis of radiographic parameters relevant to the lowest instrumented vertebrae and postoperative coronal balance in lenke 5C patients. Spine (Phila Pa 1976). 2011;36:1673–1678.

[7] QinX, HeZ, YinR, QiuY, ZhuZ. Where to stop distally in Lenke modifier C AIS with lumbar curve more than 60°: L3 or L4? Clin Neurol Neurosurg. 2019;178:77–81.

[8] WangZW, ShenYQ, WuY, LiJ, LiuZ, XuJK, et al. Anterior selective lumbar fusion saving more distal fusion segments compared with posterior approach in the treatment of adolescent idiopathic scoliosis with Lenke type 5: a cohort study with more than 8-year follow-up. Orthop Surg. 2021;13(8):2327–2334.

[9] BaghdadiS, Baldwin K. Selection of fusion levels in adolescent idiopathic scoliosis. Curr Rev Musculoskelet Med. 2024;17(1):23–36.

[10] IlharrebordeB, Ferrero E, AngelliaumeA, LefèvreY, Accadbled F, SimonAL, et al. Selective versus hyperselective posterior fusions in Lenke 5 adolescent idiopathic scoliosis: comparison of radiological and clinical outcomes. Eur Spine J. 2017;26:1739–1747.

[11] BernsteinRM, HallJE. Solid rod short segment anterior fusion in thoracolumbar scoliosis. J Pediatr Orthop Part B. 1998;7:124–131.

[12] DuboryA, MiladiL, IlharrebordeB, GennariJM, Rouissi J, GlorionC, et al. Cobb-1 versus cobb-to-cobb anterior fusion for adolescent idiopathic scoliosis Lenke 5C curves: a radiological comparative study. Eur Spine J. 2017;26:1711–1720.

[13] ObaH, Takahashi J, KobayashiS, OhbaT, Ikegami S, KuraishiS, et al. Upper instrumented vertebra to the right of the lowest instrumented vertebra as a predictor of an increase in the main thoracic curve after selective posterior fusion for the thoracolumbar/lumbar curve in Lenke type 5C adolescent idiopathic scoliosis: mul. J Neurosurg Spine. 2019;31:857–864.

[14] SudoH, KanedaK, ShonoY, Iwasaki N. Selection of the upper vertebra to be instrumented in the treatment of thoracolumbar and lumbar adolescent idiopathic scoliosis by anterior correction and fusion surgery using dual-rod instrumentation: a minimum 12-year follow-up study. Spine J. 2016;16:281–287.

[15] ZhangT, ShuS, JingW, et al. Optimizing the fusion level for Lenke 5C adolescent idiopathic scoliosis: is the S-line a validated and reproducible tool to predict coronal decompensation? Eur Spine J. 2021;30(7):1935–1942.

[16] KimDH, HyunSJ, KimKJ. Selection of fusion level for adolescent idiopathic scoliosis surgery: selective fusion versus postoperative decompensation. J Korean Neurosurg Soc. 2021;64(4):473–485.

[17] QinX, SunW, XuL, LiuZ, QiuY, ZhuZ. Selecting the last “substantially” touching vertebra as lowest instrumented vertebra in Lenke type 1A curve: radiographic outcomes with a minimum of 2-year follow-up. Spine (Phila Pa 1976). 2016;41:E742–E750.

[18] LeeCS, HaJK, HwangCJ, Lee DH, KimTH, ChoJH. Is it enough to stop distal fusion at L3 in adolescent idiopathic scoliosis with major thoracolumbar/lumbar curves? Eur Spine J. 2016;25:3256–3264.

[19] MatsumotoM, Watanabe K, HosoganeN, KawakamiN, TsujiT, UnoK, et al. Postoperative distal adding-on and related factors in Lenke type 1A curve. Spine (Phila Pa 1976). 2013;38:737–744.

[20] BannoT, YamatoY, ObaH, OhbaT, HasegawaT, Yoshida G, et al. Should the upper end vertebra be selected as the upper instrumented vertebra in patients with Lenke type 5C adolescent idiopathic scoliosis? Spine Deform. 2022;10(5):1139–1148.

[21] HuB, YangX, YangH, et al. Coronal imbalance in Lenke 5C adolescent idiopathic scoliosis regarding selecting the lowest instrumented vertebra: lower end vertebra versus lower end vertebra +1 in posterior fusion. World Neurosurg. 2018;117:e522–e529.

[22] OkadaE, Watanabe K, PangL, OguraY, Takahashi Y, HosoganeN, et al. Posterior correction and fusion surgery using pedicle-screw constructs for Lenke type 5c adolescent idiopathic scoliosis: a preliminary report. Spine (Phila Pa 1976). 2015;40:25–30.

[23] HopfCG, EyselP, DuboussetJ. Operative treatment of scoliosis with Cotrel-Dubousset-Hopf instrumentation new anterior spinal device. Spine (Phila Pa 1976). 1997;22:627–628.

[24] LiZ, DuY, ZhaoY, et al. Lowest instrumented vertebra at L3 versus L4 in posterior fusion for moderate Lenke 5C type adolescent idiopathic scoliosis: a case-match radiological study. Neurospine. 2023;20(4):1380–1388.

[25] SunZ, QiuG, ZhaoY, Wang Y, ZhangJ, ShenJ. Lowest instrumented vertebrae selection for selective posterior fusion of moderate thoracolumbar/lumbar idiopathic scoliosis: lower-end vertebra or lower-end vertebra+1? Eur Spine J. 2014;23:1251–1257.

[26] YanikHS, Ketenci IE, ErdemS. Lowest instrumented vertebrae selection in posterior fusion of Lenke 3C/6C adolescent idiopathic scoliosis: L3 versus L4, when LEV is L4. Arch Orthop Trauma Surg. 2023;143(9):5583–5588.

[27] ChangDG, YangJH, IlSS, et al. Importance of distal fusion level in major thoracolumbar and lumbar adolescent idiopathic scoliosis treated by rod derotation and direct vertebral rotation following pedicle screw instrumentation. Spine (Phila Pa 1976). 2017;42:E890–E898.

[28] YamauchiI, Nakashima H, MachinoM, ItoS, SegiN, TauchiR, et al. Relationship between lumbosacral transitional vertebra and postoperative outcomes of patients with Lenke 5C adolescent idiopathic scoliosis: a minimum 5-year follow-up study. Eur Spine J. 2023;32(6):2221–2227.

RIGHTS & PERMISSIONS

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