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

Abstract

OBJECTIVEDystrophic 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.METHODSThirty-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.RESULTSThe 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.CONCLUSIONSSurgical 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.

Management and surgical outcomes of dystrophic scoliosis in neurofibromatosis type 1: a systematic review

“…Screw malposition in dystrophic scoliosis cases is relatively high, at 20% to 30%. 25,28 Potential poor fixation and screw malpositioning should be considered during opera- tive planning, as this may affect the surgeon's ability to perform high-grade osteotomies and ultimately correct the deformity. 29 Nonetheless, high implant density should be the goal with hybrid constructs, as this will optimize chances of greater deformity correction and decreased loss of correction.…”

“…44 As expected, pedicle dysplasia results in high rates of malpositioned screws, with one study reporting an incidence of 30.5% (9.9% medial and 20.6% lateral) with the freehand insertion technique. 28 Navigation allows surgeons to circumvent some of the challenges, but the true problem is the lack of osseous volume to simply place a screw. Jin et al showed that navigation can decrease the misplaced screw rates, but even with navigation guidance, more than 20% of screws were still malpositioned.…”

“…Thoracic kyphosis measurements were reported preoperatively in 66.7% of articles and postoperatively in 50%. 14,16,[18][19][20][21][22][23][25][26][27][28][29][30][31][32][33][34][35][36][38][39][40] The sagittal curve angles at the time of surgery ranged from 16.6° to 97.4°, with a mean of 55.3°. Postoperative scoliosis and thoracic kyphosis ranged from 17° to 56.5° and 4.5° to 56.4°, respectively.…”

“…Very few studies (17%) reported PROMs, and not all of those studies reported incremental changes before and after surgery. 13,23,[26][27][28]40 23,40 Another report by Betz et al asked patients whether they were satisfied or not, with 8 of 10 patients reporting satisfaction with surgery. 13 Studies comparing scores before and after surgery revealed significant improvement in the mental health, self-image, and activity domains.…”

“…13 Studies comparing scores before and after surgery revealed significant improvement in the mental health, self-image, and activity domains. 27,28 Koptan and ElMiligui showed that patients with kyphosis greater than 45° preoperatively have lower SRS-30 scores postoperatively than those with kyphosis less than 45°. 26 This finding highlights the importance of sagittal plane deformity in scoliosis.…”