Assessing the unique characteristics associated with surgical treatment of dystrophic lumbar scoliosis secondary to neurofibromatosis type 1: a single-center experience of more than 10 years

Song Li PhD, Saihu Mao MD, Changzhi Du MD, Zezhang Zhu MD, Benlong Shi MD, Zhen Liu MD, Jun Qiao MD, and Yong Qiu MD
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  • Spine Surgery, Drum Tower Hospital, Nanjing University Medical School, Nanjing, Jiangsu Province, China
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OBJECTIVE

Dystrophic lumbar scoliosis secondary to neurofibromatosis type 1 (DLS-NF1) may present an atypical, unique curve pattern associated with a high incidence of coronal imbalance and regional kyphosis. Early surgical intervention is complicated and risky but necessary. The present study aimed to assess the unique characteristics associated with the surgical treatment of DLS-NF1.

METHODS

Thirty-nine consecutive patients with DLS-NF1 treated surgically at a mean age of 14.4 ± 3.9 years were retrospectively reviewed. Patients were stratified into three types according to the coronal balance classification: type A (C7 translation < 30 mm), 22 patients; type B (concave C7 translation ≥ 30 mm), 0 patients; and type C (convex C7 translation ≥ 30 mm), 17 patients. Types B and C were considered to be coronal imbalance. The diversity of surgical strategies, the outcomes, and the related complications were analyzed.

RESULTS

The posterior-only approach accounted for 79.5% in total; the remaining 20.5% of patients received either additional anterior supplemental bone grafting (12.8%) to strengthen the fixation or convex growth arrest (7.7%) to reduce growth asymmetry. The lower instrumented vertebra (LIV) being L5 accounted for the largest share (41%), followed by L4 and above (35.9%), the sacrum (15.4%), and the pelvis (7.7%). Type C coronal imbalance was found in 23 patients (59%) postoperatively, and the incidence was significantly higher in the preoperative type C group (14/17 type C vs 9/22 type A, p = 0.020). All the patients with postoperative coronal imbalance showed ameliorative transition to type A at the last visit. The rate of screw malposition was 30.5%, including 9.9% breached medially and 20.6% breached laterally, although no serious neurological impairment occurred. The incidence of rod breakage was 16.1% (5/31) and 0% in patients with the posterior-only and combined approaches, respectively. Four revisions with satellite rods and 1 revision with removal of iliac screw for penetration into the hip joint were performed.

CONCLUSIONS

Surgical strategies for DLS-NF1 were diverse across a range of arthrodesis and surgical approaches, being crucially determined by the location and the severity of dystrophic changes. The LIV being L5 or lower involving the lumbosacral region and pelvis was not rare. Additional posterior satellite rods or supplementary anterior fusion is necessary in cases with insufficient apical screw density. Despite a high incidence of postoperative coronal imbalance, improvement of coronal balance was frequently confirmed during follow-up. Neurological impairment was scarce despite the higher rate of screw malposition.

ABBREVIATIONS AIS = adolescent idiopathic scoliosis; AVT = apical vertebral translation; CB = coronal balance; DLS-NF1 = dystrophic lumbar scoliosis secondary to NF1; LIV = lower instrumented vertebra; NF1 = neurofibromatosis type 1; PJK = proximal junctional kyphosis; PSO = pedicle subtraction osteotomy; SRS-22 = Scoliosis Research Society-22 questionnaire; SVA = sagittal vertical axis; VRS = vertebral rotatory subluxation.

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Contributor Notes

Correspondence Zezhang Zhu: Drum Tower Hospital, Nanjing University Medical School, Nanjing, China. zhuzezhang@126.com.

INCLUDE WHEN CITING Published online November 20, 2020; DOI: 10.3171/2020.6.SPINE20898.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

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