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

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  • 1 Department of Neurological Surgery, New York University, New York, New York;
  • | 2 Department of Neurology and Comprehensive Neurofibromatosis Center, New York University, New York, New York; and
  • | 3 Shriners Hospital for Children, Philadelphia, Pennsylvania
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OBJECTIVE

Neurofibromatosis type 1 (NF1) dystrophic scoliosis is an early-onset, rapidly progressive multiplanar deformity. There are few studies on the surgical management of this patient population. Specifically, perioperative morbidity, instrument-related complications, and quality-of-life outcomes associated with surgical management have not been systematically evaluated. In this study, the authors aimed to perform a systematic review on the natural history, management options, and surgical outcomes in patients who underwent NF1 dystrophic scoliosis surgery.

METHODS

A PubMed search for articles with “neurofibromatosis” and either “dystrophic” or “scoliosis” in the title or abstract was performed. Articles with 10 or more patients undergoing surgery for NF1 dystrophic scoliosis were included. Data regarding indications, treatment details, morbidity, and outcomes were summarized and analyzed with descriptive statistics.

RESULTS

A total of 310 articles were identified, 48 of which were selected for full-text review; 30 studies describing 761 patients met the inclusion criteria. The mean age ranged from 7 to 22 years, and 99.7% of patients were younger than 18 years. The mean preoperative coronal Cobb angle was 75.2°, and the average correction achieved was 40.3°. The mean clinical follow-up in each study was at least 2 years (range 2.2–19 years). All patients underwent surgery with the intent of deformity correction. The scoliosis regions addressed were thoracic curves (69.6%) and thoracolumbar (11.1%) and lumbar (14.3%) regions. The authors reported on a variety of approaches: posterior-only, combined anterior-posterior, and growth-friendly surgery. For fixation techniques, 42.5% of patients were treated with hybrid constructs, 51.5% with pedicle screw–only constructs, and 6.0% with hook-based constructs. Only 0.9% of patients underwent a vertebral column resection. The nonneurological complication rate was 14.0%, primarily dural tears and wound infections. The immediate postoperative neurological deficit rate was 2.1%, and the permanent neurological deficit rate was 1.2%. Ultimately, 21.5% required revision surgery, most commonly for implant-related complications. Loss of correction in both the sagittal and coronal planes commonly occurred at follow-up. Five papers supplied validated patient-reported outcome measures, showing improvement in the mental health, self-image, and activity domains.

CONCLUSIONS

Data on the surgical outcomes of dystrophic scoliosis correction are heterogeneous and sparse. The perioperative complication rate appears to be high, although reported rates of neurological deficits appear to be lower than clinically observed and may be underreported. The incidence of implant-related failures requiring revision surgery is high. There is a great need for multicenter prospective studies of this complex type of deformity.

ABBREVIATIONS

AIS = adolescent idiopathic scoliosis; NF1 = neurofibromatosis type 1; PROM = patient-reported outcome measure; SRS = Scoliosis Research Society; VCR = vertebral column resection.

OBJECTIVE

Neurofibromatosis type 1 (NF1) dystrophic scoliosis is an early-onset, rapidly progressive multiplanar deformity. There are few studies on the surgical management of this patient population. Specifically, perioperative morbidity, instrument-related complications, and quality-of-life outcomes associated with surgical management have not been systematically evaluated. In this study, the authors aimed to perform a systematic review on the natural history, management options, and surgical outcomes in patients who underwent NF1 dystrophic scoliosis surgery.

METHODS

A PubMed search for articles with “neurofibromatosis” and either “dystrophic” or “scoliosis” in the title or abstract was performed. Articles with 10 or more patients undergoing surgery for NF1 dystrophic scoliosis were included. Data regarding indications, treatment details, morbidity, and outcomes were summarized and analyzed with descriptive statistics.

RESULTS

A total of 310 articles were identified, 48 of which were selected for full-text review; 30 studies describing 761 patients met the inclusion criteria. The mean age ranged from 7 to 22 years, and 99.7% of patients were younger than 18 years. The mean preoperative coronal Cobb angle was 75.2°, and the average correction achieved was 40.3°. The mean clinical follow-up in each study was at least 2 years (range 2.2–19 years). All patients underwent surgery with the intent of deformity correction. The scoliosis regions addressed were thoracic curves (69.6%) and thoracolumbar (11.1%) and lumbar (14.3%) regions. The authors reported on a variety of approaches: posterior-only, combined anterior-posterior, and growth-friendly surgery. For fixation techniques, 42.5% of patients were treated with hybrid constructs, 51.5% with pedicle screw–only constructs, and 6.0% with hook-based constructs. Only 0.9% of patients underwent a vertebral column resection. The nonneurological complication rate was 14.0%, primarily dural tears and wound infections. The immediate postoperative neurological deficit rate was 2.1%, and the permanent neurological deficit rate was 1.2%. Ultimately, 21.5% required revision surgery, most commonly for implant-related complications. Loss of correction in both the sagittal and coronal planes commonly occurred at follow-up. Five papers supplied validated patient-reported outcome measures, showing improvement in the mental health, self-image, and activity domains.

CONCLUSIONS

Data on the surgical outcomes of dystrophic scoliosis correction are heterogeneous and sparse. The perioperative complication rate appears to be high, although reported rates of neurological deficits appear to be lower than clinically observed and may be underreported. The incidence of implant-related failures requiring revision surgery is high. There is a great need for multicenter prospective studies of this complex type of deformity.

Neurofibromatosis type 1 (NF1) is caused by mutations in the tumor suppressor NF1 gene, and skeletal anomalies, including scoliosis, are strongly associated with the disorder.1 Scoliosis is the most common bony abnormality in NF1 and occurs in dystrophic and nondystrophic subtypes.2,3 The defining features of dystrophic scoliosis are the presence of bony dysplasia (rib penciling, vertebral rotation, vertebral body scalloping, vertebral wedging, widened interpedicular distance, and enlargement of the intervertebral foramina),2 while nondystrophic scoliosis resembles idiopathic scoliosis.4 NF1 dystrophic scoliosis classically has an early onset and is difficult to manage because of its aggressive behavior.5,6 While the pathophysiology of dystrophic scoliosis is not fully elucidated, bony remodeling due to multiple factors (dural ectasias, tumor, and abnormal bony metabolism) contributes to the pathogenesis.7 Such dysmorphic changes result in rapid curve progression, multiplanar deformity, and high incidence of neurological deficits.3,5 Unfortunately, the conservative and surgical management of the ensuing spinal deformities is not well defined; surgeons rely mainly on clinical experience. Corrective bracing is typically ineffective in dystrophic scoliosis, and curve progression is expected.8 Surgical intervention is often challenging, and surgeons must account for tumor burden, dural ectasia, poor bone quality, dysplastic pedicles, and severity of the deformity.911 There is a lack of high-quality studies within the literature on the surgical outcomes of patients undergoing surgery for dystrophic scoliosis. In this study, we aimed to perform a systematic review describing the natural history, management strategies, and surgical outcomes of patients who undergo correction of NF1 dystrophic scoliosis.

Methods

A formal systematic review was performed in line with the 2020 version of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.12 First, an electronic literature search was performed via PubMed. To capture a comprehensive list of published reports, the search term used was “neurofibromatosis” coupled with either “scoliosis” or “dystrophic” in the title or abstract. The specific search term and specifications for review can be found in the Appendix. Publications of interest were from inception to September 2021. Specific exclusion criteria were reports that studied fewer than 10 patients, lacked data regarding surgical outcomes, and reported exclusively on nondystrophic scoliosis subtypes. From each of the studies, demographics, clinical characteristics, indications, surgical details, and outcomes (perioperative and follow-up) were collected and summarized (Table 1).

TABLE 1.

Systematic literature review of surgical outcomes of patients with dystrophic scoliosis surgery

Authors & YearNo. of PtsMean Age & Sex DistributionNo. of Pediatric PtsAverage FUInclusion & Exclusion CriteriaBracingCoronal DeformityKyphosisOp ApproachSpinal RegionType of FixationVCR Rate
Betz et al., 19891323 (19 dystrophic, 10 w/ FU)NR for only dystrophic ptsNRNR for only dystrophic ptsInclusion: pts w/ NF & scoliosis who received pst fusion (19 dystrophic, 4 nondystrophic); exclusion: noneNANR for only dystrophic ptsNR for only dystrophic ptsPst fusion w/ Harrington inst: 7/19; in situ pst fusion: 12/19NRHarrington rod: 7/19; in situ pst fusion: 12/190/19
Bouthors et al., 202014188 yrs, 6 M (33%)185 yrsInclusion: consecutive series of pts w/ 2-yr FU; exclusion: nonePreop bracing: 15/18 (all pts who did not meet op criteria); failed: 15/1557° (range 31–90°)37° (range 11–79°)Growing rods: 18/18 (14 single, 4 dual); preop halo traction: 5/18; preop turnbuckle cast: 8/18Thoracic: 17/18; lumbar: 1/18Hybrid: 18/180/18
Cai et al., 20201516Pst fusion: 7.7 yrs, 3 M (38%); GRs: 7.4 yrs, 2 M (25%)1651 mosInclusion: early-onset dystrophic scoliosis w/ NF1, age ≤10 yrs, main curve in thoracic region, 2-yr FU; exclusion: combined ant-pst op, lost to FUNAPst fusion: 67°; GRs: 75°NRGrowing rods: 8/16; pst fusion: 8/16Thoracic: 16/16Hybrid: 3/16; pedicle screw: 13/160/16
Cai et al., 202016107.8 yrs (range 4.2–9.6yrs) 1054 mos (range 24–88 mos)Inclusion: pst-only fusion for dystrophic scoliosis, age ≤10 yrs, 2-yr FU; exclusion: noneNA66° (range 43–90°)42.9 ± 22.0°Pst fusion: 10/10Thoracic: 9/10; lumbar: 1/10Hybrid: 3/10; pedicle screw: 7/100/10
Calvert et al., 19891166 (34 op)Pst fusion w/o inst: 11.8 yrs; pst fusion w/ Harrington inst: 12.2 yrs (range 8.5–19.8 yrs); ant fusion: 12.8 yrs; combined ant-pst: 12.5 yrsNRPst fusion w/o inst: 19 yrs; pst fusion w/ Harrington inst: 18.1 yrsInclusion: NF pts, scoliosis; exclusion: nondystrophic curvesNAPst fusion w/o inst: NR; pst fusion w/ Harrington inst: 85°; ant fusion: 91°; combined ant-pst: 96°NRPst fusion w/o inst: 11/34; pst fusion w/ Harrington inst: 15/34; ant fusion: 4/34; combined ant-pst: 4/34NRHarrington rod: 15/34; noninstrumented fusion: 11/34; ant spinal fusion: 4/34; combined ant-pst fusion 4/340/34
Chaglassian et al., 19761737 (15 op)NR for op cohort159 (range 0.25–14) yrsInclusion: NF, scoliosisPreop bracing: 2/37; failed: 0/2NRNRPst fusion w/ buckle-cast correction: 6; pst fusion w/ Harrington inst: 7; combined ant-pst w/ Harrington: 1; ant only: 1Cervicothoracic: 2; thoracic: 23; double thoracic: 2; thoracolumbar: 7; thoracic-thoracolumbar double: 3Pst fusion w/ buckle-cast correction: 6; pst fusion w/ Harrington inst: 7; combined ant-pst w/ Harrington: 1; ant only: 10/15
Cinnella et al., 2020181013.5 yrs (range 11–23 yrs), 6 M (60%)NR4 yrs (range 2–5 yrs)Inclusion: age 8–25 yrs, thoracic curve >45°, implant density >70%, 1-yr FU; exclusion: noneNA93° (range 60°–111°)60° (range 51°–83°)Pst-only approach: 10/10Thoracic: 10/10Hybrid: 10/10 0/10
Deng et al., 2017193113.5 yrs (range 10–22 yrs), 24 M (77%)NR53 mos (range 12–96 mos)Inclusion: CA >20°, consideration of magnitude & progression of spinal deformity, age >10 yrs; exclusion: intraspinal tumor, incomplete FUPreop bracing: 7/31; failed: 7/769.1° (range 48.9–91.4°)58.3° (range 34.1–79.6°)Multiple anchor point pst op correctionThoracic: 25/31; thoracolumbar: 4/31; lumbar: 2/31NR0/31
Greggi & Martikos, 201220239.1 yrs (range 4–11 yrs), 14 M (61%)235 yrs (range 1.5–15 yrs)Inclusion: progressive scoliosis >35°, prepubertal age, 18-mo FU; exclusion: noneNA48° (range 38–82°)<50° in 16 pts; >50° in 7 ptsCombined ant-pst approach: 7/23; pst-only fusion: 16/23NRHooks: 6/23; hybrid: 12/23; pedicle screw: 5/23NA
Halmai et al., 2002211117.5 yrs (range 11–23 yrs), 6 M (55%)NR4.4 yrsInclusion: NF1 pts w/ scoliosis (11 dystrophic, 1 nondystrophic), op treatment; exclusion: noneBracing: 11/11; indication: 20–35°; failed: 11/11Thoracic kyphoscoliosis: 125 ± 10.2°; thoracolumbar/lumbar: 68 ± 6.8°Thoracic kyphoscoliosis: 97.4 ± 25.5°; thoracolumbar/lumbar: 42 ± 5.5°Preop halo traction, followed by pst fusion w/ ant release: 11/11Thoracic: 5/11; thoracolumbar: 3/11; thoracolumbar-lumbar double curve: 1/11; lumbar: 2/11Hybrid: 11/11 0/11
Hsu et al., 1984221313 yrs (range 6–19 yrs), 8 M (62%)NR7 yrs (range 5–11 yrs)Inclusion: dystrophic scoliosis, combined op approach; exclusion: noneNAScoliosis alone: 69.9°; round kyphoscoliosis: 59.6°Scoliosis alone: NR; round kyphoscoliosis: 63.2°Combined ant-pst: 13/13Thoracic: 12/13; thoracolumbar: 1/13Ant fusion w/ pst Harrington rods: 7/13; ant fusion w/ unclear rates of pst fusion: 6/130/13
Iwai et al., 2013231021.6 yrs (range 6–46 yrs), 4 M (40%)NR9.8 yrs (range 1–30 yrs)Inclusion: consecutive series; exclusion: noneNA63.9° (range 11–98°)70.6° (range 50–99°)Combined ant-pst fusion using a fibular strut autograft & pst instThoracic: 9/10; thoracolumbar: 1/10NR0/10
Jain et al., 201724146.8 yrs (range 2.7–9.7 yrs), 4 M (29%)1454 mos (range 22–95 mos)Inclusion: dystrophic scoliosis, traditional GR inst, age <10 yrs, 18 mos of FU; exclusion: noneNA73.6° (range 40–125°) NRGrowing rods: 14/14NRHooks: 7/14; hybrid: 4/14; pedicle screw: 3/140/14
Jin et al., 20162532O-arm: 14.8 yrs (range 11–22 yrs); freehand: 15.3 yrs (range 12–27 yrs)NRNot applicableInclusion: >3 dystrophic changes on imaging, single thoracic or double thoracic curve patterns, pedicle screw–based pst inst, curve severity >60°; exclusion: prior op, hybrid constructsNAO-arm group: 70.3 ± 6.7°; freehand group: 62.2 ± 8.7°O-arm group: 18.4 ± 9.3°; freehand group: 16.6 ± 9.0°Pst fusion: 32/32Thoracic: 32/32Pedicle screw: 32/32 0/32
Koptan & ElMiligui, 2010263214 yrs (range 11–19 yrs), 18 M (56%)NR6.5 yrs (range 3–9 yrs)Inclusion: consecutive series w/ 3-yr FU; exclusion: nonePreop bracing: 20/32; failed: 20/20102° (range 71–114°)49° (range 2–91°)Ant release/fusion followed by pst instrumented fusion w/ sublaminar wires: 32/32Thoracic: 13/32; thoracolumbar: 14/32; lumbar: 5/32Hybrid: 32/32 0/32
Li et al., 2009271614 yrs (range 11–18 yrs), 7 M (44%)154.8 yrs (range 2–8 yrs)Inclusion: consecutive pts w/ NF1, scoliosis (dystrophic & nondystrophic), treated w/ pst approach, CA 40°–90°; exclusion: noneBracing: 2/16; failed: 2/268°35°Pst fusion: 16/16Thoracic: 11/16; thoracolumbar: 3/16; lumbar: 2/16Hybrid: 16/160/16
Li et al., 2017294113 yrs (range 8–18 yrs), 25 M (61%)NR28.8 mos (range 24–39 mos)Inclusion: thoracic curve btwn 50 & 100°, 1-stage pst spinal fusion w/ ≥80% pedicle screws, 2-yr FU; exclusion: prior spine op, 3-column osteotomyNAHigh implant density: 69.5 ± 13.3°; low implant density: 72.1 ± 12.5°High implant density: 47.6 ± 19.7°; low implant density: 50.4 ± 25.2°1-stage pst fusion: 41/41Thoracic: 41/41Hybrid: 7/41; pedicle screw: 34/41Excluded
Li et al., 2021283914.4 yrs, 26 M (67%)NR37 mos (range 24–115 mos)Inclusion: lumbar scoliosis, 2-yr FU; exclusion: cervical or thoracic scoliosis, neuro deficits precluding erect spinal alignment measurement, prior op, GR placementNA64° (range 34–100°)35.3° (range 10–92.2°)Pst fusion: 31/39 (79.5%); pst fusion w/ convex growth arrest: 3/39 (7.7%); pst fusion w/ ant bone graft: 5/39 (12.8%); Smith-Petersen osteotomy: 7/39; pedicle subtraction osteotomy: 1/39Lumbar: 39/39Pedicle screw or hybrid, no breakdown given1/39
Mladenov et al., 202030339.8 yrs (range 4.3–16.6 yrs), sex NR33NRInclusion: dystrophic spinal deformity from NF1; exclusion: noneNA70° (range 51–96°)97° (range 70–125°)Pst fusion: 7; ant fusion: 1; combined ant-pst fusion: 3; GR ops: 22Cervical: 3/33; thoracic/lumbar: 30/33NR0/33
Parisini et al., 1999315614 yrs (range 4–39 yrs), 30 M (54%)NRAge at final FU: 28.7 yrs (range 13–39 yrs)Inclusion: dystrophic scoliosis, pst or combined op approach; exclusion: <5-yr FUPreop bracing: 7/56; failed: 7/7Kyphosis <50°, pst only: 71.4°; kyphosis <50°, combined: 75°; kyphosis >50°, pst only: 100°; kyphosis >50°, combined: 78.8°Kyphosis <50°, pst only: 33°; kyphosis <50°, combined: 34°; kyphosis >50°, pst only: 90°; kyphosis >50°, combined: 73.6°Kyphosis <50°, preplanned pst only: 19/56; kyphosis <50°, preplanned combined: 6/56; kyphosis >50°, preplanned pst only: 11/56; kyphosis >50°, preplanned combined: 20/56Thoracic: 42/56; thoracolumbar: 7/56; lumbar: 7/56Harrington rod: 38/56; Harrington-Luque technique: 15/56; Cotrel-Dubousset inst: 2/56; Colorado technique: 1/560/56
Shen et al., 2005323914.2 yrs (range 5–33 yrs), sex NRNR6.8 yrsInclusion: NF1 pts w/ scoliosis (39 dystrophic, 6 nondystrophic), op; exclusion: noneNAThoracic curve initial CA: 96.5°; thoracolumbar curve initial CA: 75°; lumbar curve initial CA: 55.3°Thoracic curve initial kyphosis: 79.8°; thoracolumbar curve initial kyphosis: 47.5°Pst only: 25 pts; combined: 14 ptsThoracic: 26/39; thoracolumbar: 6/39; lumbar: 7/39NR0/39
Sirois & Drennan, 1990516NR for op cohortNR for op cohort9.8 yrs (range 1.5–23 yrs)Inclusion: NF, spinal deformity; exclusion: noneNAPst only: 52°; combined ant-pst: NRNRPst only: 13/16; combined ant-pst: 3/16NRHarrington rod: 9/16; Luque inst: 1/16; noninstrumented fusion: 3/16; combined ant-pst fusion: 3/160/16
Tauchi et al., 202033118.3 yrs (range 5.8–9.9 yrs), 7 M (64%)1114 yrs (range 5.8–25 yrs)Inclusion: early-onset dystrophic scoliosis due to NF1; exclusion: nonfusion procedureNA71.2° (range 30–93°)39.9° (range 46–62°)Preop halo traction, followed by combined ant-pst fusion w/ bone graft: 11/11Thoracic: 10/11; thoracolumbar: 1/11Pedicle screw or hybrid, no breakdown given0/11
Tauchi et al., 20203426Early fusion: 7.3 yrs (range 2–9 yrs), 8 M (50%); GRs: 5.8 yrs (range 2–8 yrs), 7 M (70%)26Early fusion: 12.8 yrs (range 6.5–25 yrs); GRs: 10.5 yrs (range 6.8–14.5 yrs)Inclusion: dystrophic thoracic scoliosis, age <10 yrs at initial op; exclusion: pelvic dystrophic changes, lumbar scoliosisNAEarly fusion: 75°; GRs: 83°Early fusion: 45.4 ± 19.9°; GRs: 33.0 ± 16.2°Early fusion: 16 pts (13 combined fusion, 3 pst only); GRs: 10 ptsThoracic: 26/26NR0/26
Wang et al., 20153516Age NR, 8 M (50%)NR40.9 mos (range 24–74 mos)Inclusion: consecutive series of pst-only pedicle screw–based fusion; exclusion: noneNA83.2° (range 45–142°)58.5° (range 13–160°)Pst fusion: 16/16NRPedicle screw: 16/164/16
Wilde et al., 1994362511.8 yrs (range 4–22 yrs), 15 M (60%)NR9.7 yrs (range 2–24 yrs)Inclusion: dystrophic scoliosis; exclusion: lost to FUNAScoliosis group: 68° (range 37–94°); kyphoscoliosis group: 65° (range 39–107°); hyperkyphosis group: 65° (range 58–72°); overall: 67° (range 39–107°)Kyphosis <50°: 15 pts (60%); kyphosis >50°: 10 pts (40%)1-stage ant-pst: 1/25; ant only: 1/25; ant then pst: 9/25; pst then ant: 6/25; pst only: 8/25NRHarrington rod: 18/25; Luque rods & sublaminar wiring: 1/25; noninstrumented fusion w/ postop immobilization: 6/250/25
Xu et al., 201937117.2 yrs (range 5–9 yrs), 7 M (64%)112.2 yrs (range 2–2.8 yrs)Inclusion: age <10 yrs at onset, major curve >60°, spinal flexibility <30%, 2-yr FU; exclusion: noneNA72.0° (range 60–100°) NRPreop halo traction followed by dual GRs: 11/11NRHooks: 1/11; pedicle screw: 10/110/11
Yao et al., 20193859Pst fusion: 10.3 yrs (range 5–16 yrs), 19 M (59%); GRs: 5.8 yrs (range 2.5–9 yrs), 14 M (52%)595.4 yrs (range 3–12 yrs)Inclusion: dystrophic scoliosis, pst or combined op approach, 3-yr FU; exclusion: cervical deformity alone, nondystrophic scoliosis, <2 distractions after GR placementPreop bracing: 59/59; failed: 59/59Initial fusion: 64.0 ± 22.0°; GRs: 63.7 ± 18.1°Initial fusion: 49.0 ± 25.7°; GRs: 52.8 ± 24.2°Initial fusion: 32 pts; GRs: 27 ptsNRNR0/59
Yao et al., 201839598.2 yrs (range 2.5–16 yrs), 32 M (54%)595.4 yrs (range 3–12 yrs)Inclusion: dystrophic scoliosis, pst or combined op approach, 3-yr FU; exclusion: cervical deformity, <3 distractions after GR placementPreop bracing: 59/59; failed: 59/59Hardware complication: 68.5 ± 20.8°; no hardware complication: 63.4 ± 21.9°Hardware complication: 63.5 ± 16.4°; no hardware complication: 57.7 ± 36.5°Growing rods: 32 pts; definitive fusion: 27 ptsSingle thoracic: 30/59; double thoracic: 16/59; thoracolumbar: 6/59; lumbar: 7/59NRNA
Zhao et al., 201640269 yrs (range 6–15 yrs), 16 M (62%)26NRInclusion: consecutive series; exclusion: nonePreop bracing: 10/26; failed: 10/1047° (range 35–96°)43° (range 15–86°)Pst fusionThoracic: 14/26; thoracolumbar: 9/26; lumbar: 3/26NRUnclear

ant = anterior; CA = Cobb angle; FU = follow-up; GR = growing rod; inst = instrumentation; NA = not available; neuro = neurological; NR = not reported; pst = posterior; Pt = patient.

Results

A total of 310 articles were identified (Fig. 1), 48 of which were selected for full-text review;30 were included in the final analysis, describing 761 total patients (Tables 1 and 2).5,11,1340 The mean patient age was 11.5 years; 99.7% were younger than 18 years of age. Of the 30 articles, 25 (83.3%) had follow-up data, and the mean follow-up was 6.4 years. The scoliosis regions were thoracic curves (69.6%) and thoracolumbar (11.1%) and lumbar (14.3%) regions. When specified, 42.5% of the patients underwent placement of hybrid constructs, 51.5% pedicle screw–only constructs, and 6.0% hook-based constructs. High-grade osteotomies were performed in 0.9% of patients (vertebral column resection [VCR]). The perioperative complication rate was 14.0%. Neurological deficits were not frequently reported; the immediate postoperative neurological deficit rate was 2.1%, while the rate of residual permanent neurological deficits was 1.2%. The revision surgery rate was 21.5%, mostly for implant and mechanical complications: rod fracture, pseudarthrosis, and junctional failures. Only 5 studies presented patient-reported outcome measures (PROMs), all using the Scoliosis Research Society (SRS)–22 or SRS-30 questionnaire, with unanimous conclusions that patients benefited from surgery.

FIG. 1.
FIG. 1.

PRISMA diagram for systematic review.

TABLE 2.

Additional information from a systematic literature review of surgical outcomes of patients with dystrophic scoliosis surgery

Authors & YearMean Blood LossPeriop Complications Complications (n)Postop Neuro Deficit Perm Neuro DeficitsType of Neuro DeficitsHardware Failure/Pseudarthrosis RateReop RateCorrection of DeformityReported PROMs?Reported Improvement on PROMs?
Betz et al., 198913NANRNA0/19 (0%)0/19 (0%)NANR for only dystrophic ptsNRNR for only dystrophic ptsYes, binary satisfaction questionYes, 8/10 satisfied
Bouthors et al., 202014NA13/18 (72%)Dural tear (2)0/18 (0%)0/18 (0%)NAHardware failure: 17 total events in unclear no. of pts; pseudarthrosis: NR1/18: hardware failurePostop coronal CA: 36 ± 14° (range 9–68°); postop thoracic kyphosis: 31° ± 12° (range 8–54°); final coronal CA: 37 ± 13° (range 18–67°); final thoracic kyphosis: 34 ± 11° (range 17–54°)NoNA
Cai et al., 202015498.8 mL (range 200–3000 mL)5/16 (31%)UTI (1), ileus (2), superficial wound infection (1), delayed wound healing (1)0/16 (0%)0/16 (0%)NARod breakage: 1/16; overall: 5/164/16: hardware complicationsPostop pst fusion coronal correction: 52.1 ± 15.3%; postop GR coronal correction: 56.5 ± 11.9%NoNA
Cai et al., 202016580 mL (range 200–2000 mL)3/10 (30%)Wound infection (1), ileus (1), UTI (1)0/10 (0%)0/10 (0%)NAHardware failure: 3/10; pseudarthrosis: NR2/10Postop coronal CA: 31.1 ± 14.6° (range 13.4–51.2°); postop thoracic kyphosis: 28.1 ± 11.6°; final coronal CA: 41.0 ± 16.0° (range 17.0–70.3°); final thoracic kyphosis: 34.6 ± 14.7°NoNA
Calvert et al., 198911NANRNANRNRNAPseudarthrosis: 3/15; hardware failure: 3/15*4/15*Harrington inst postop CA: 52°; Harrington inst postop kyphosis: 29°; Harrington inst final CA: 56°; Harrington inst final kyphosis: 34°NoNA
Chaglassian et al., 197617NA2/15 (13%)Infection (1), hemothorax (1)1/15 (7%)1/15 (7%)Nerve root (1)Pseudarthrosis: 1/15; hardware failure: 2/152/15NRNoNA
Cinnella et al., 2020181650 mL1/10 (10%)Pressure injury0/10 (0%)0/10 (0%)NA0/100/10Postop coronal CA: median 45° (range 25–55°); postop kyphosis: median 41° (range 31–51°); final FU coronal CA: median 43° (range 27–56°); final FU kyphosis: median 47° (range 35–57°)NoNA
Deng et al., 201719NA0/31 (0%)NA0/31 (0%)0/31 (0%)NA1/311/31: hook dislodgment, pseudarthrosisPostop CA: 27.4° (range 16.3– 46.7°); postop kyphosis: 22.4° (range 4.2–36.3°); final CA: 30.2° (range 18.9–51.8°); final kyphosis: 24.1° (range 6.8–39.1°)NoNA
Greggi & Martikos, 201220NANRNANRNRNAPseudarthrosis: 4/23; screw loosening: 1/235/23: pseudarthrosis (4), hardware failure (5)Percent corrected (hyperkyphotic pts): mean 42% (range 20–55%); % corrected (hypokyphotic pts): mean 60%NoNA
Halmai et al., 200221NA (estimates include nondystrophic scoliosis pts)NRNANRNRNANA (unclear if dystrophic)NA (unclear if dystrophic)NRNoNA
Hsu et al., 198422NA3/13 (23%)Sinus tachycardia (1), hematoma (1), cord compression (1)2/13 (15%)2/13 (15%)Cord (2)Pseudarthrosis: 1/13; hardware failure: 2/131/13: pseudarthrosisCA in scoliosis alone: 49°; CA in round kyphoscoliosis: 39.8°; kyphosis in round kyphoscoliosis: 43.2°NoNA
Iwai et al., 2013232/10 pts w/ EBL >4 L4/10 (40%)CSF leak (2), EBL >4 L (2)0/10 (0%)0/10 (0%)NAPseudarthrosis: 1/101/10: nonunionPostop CA: 44.5° (range 7–68°); postop kyphosis: 56.4° (range 33–79°); final CA: 41.8° (range 10–75°); final kyphosis: 60.6° (range 35–87°)Yes, SRS-22No comparison made pre- & postop; postop SRS-22 domain scores as follows: function, 4.3 (range 3.4–5.0); pain, 4.2 (range 3.5–5.0); self-image, 3.4 (range 1.8–5.0); mental health, 3.9 (range 2.4–5.0); & satisfaction, 4.1 (range 3.0–5.0)
Jain et al., 201724NA2/14 (14%)Deep infection (2)0/14 (0%)0/14 (0%)NARod breakage: 2/14; prominent implants: 1/14; PJK: 5/14; overall: 8/146/14: deep infection (2), definitive fusion (4), unclear if overlapPostop CA: 30.2° (range 10–53°); final CA: 36.2° (range 17–63°)NoNA
Jin et al., 201625NA1/32 (3%)Dural tear (1)0/32 (0%)0/32 (0%)NANANAO-arm CA: 17.0°; freehand CA: 21.4°NoNA
Koptan & ElMiligui, 201026960 mL (range 650–1500 mL)3/32 (9%)Superficial infection (2), deep infection (1)1/32 (3%)0/32 (0%)Nerve root (1)Pseudarthrosis: 2/32; hardware failure: 0/322/32: pseudarthrosisPostop CA: 39° (range 16–49°); postop kyphosis correction: mean 61%Yes, SRS-30Pts w/ preop kyphosis >45° had worse postop SRS-30 scores than pts w/ kyphosis <45° (mean 112 vs 124, p < 0.001)
Li et al., 200927807 mL (range 510–1550 mL)3/16 (19%)Dural tear (3)0/16 (0%)0/16 (0%)NAPseudarthrosis: 1/16; hardware failure: 1/161/16: pseudarthrosis w/ hardware failurePostop CA: 27°; postop kyphosis: 26°; final CA: 33°; final kyphosis: 28°NoNA
Li et al., 201729High implant density: 1228 ± 965 mL; low implant density: 1026 ± 706 mL0/41 (0%)NA0/41 (0%)0/41 (0%)NA0/410/41Postop CA: 35.6 ± 14.2° (range 10–65°); postop kyphosis: 29.1 ± 12.1° (range 12–66°)Yes, SRS-22SRS-22 scores improved in appearance, activity, & mental health domains in both groups
Li et al., 202128NA1/39 (3%)CSF leak0/39 (0%)0/39 (0%)NAPJK: 7/39; rod breakage: 5/39; pseudarthrosis: 1/39; overall: 13/395/39: rod breakagePostop coronal CA: 23.9 ± 15.8° (range 2–61.4°); postop kyphosis: 4.5 ± 10.7° (range −10 to 22.6°)Yes, SRS-22SRS-22 mental health & self-image scores significantly improved for pst-only fusion (3.0 ± 0.6 to 4.0 ± 0.9 [p = 0.009] & 2.9 ± 0.5 to 4.3 ± 0.7 [p = 0.002], respectively) & combined fusion (3.1 ± 0.7 to 4.0 ± 0.8 [p < 0.001] & 2.9 ± 0.5 to 4.2 ± 0.8 [p < 0.001], respectively) groups
Mladenov et al., 202030NANRNR0/33 (0%)1/33 (3%)Cord (1)Rib anchor loosening: 12/33; mechanical complications: 5/3317/33CA: 28.6° (range 1–55°); cervical kyphosis: 25° (range 10–52°)NoNA
Parisini et al., 199931NANRNA1/56 (2%)2/56 (4%)Cord (2)NR22/56: curve progression (16), complete relapse (6)Postop & final coronal & sagittal angles reported across 9 subgroups; refer to paper for valuesNoNA
Shen et al., 200532600 mL (range 150–2400 mL)Unclear which pts had dystrophic vs nondystrophicNAUnclear which pts had dystrophic vs nondystrophicUnclear which pts had dystrophic vs nondystrophicNANA (unclear)NA (unclear)Thoracic curve postop CA: 49.3°; thoracic curve final CA: 54.1°; thoracic curve postop kyphosis: 41.7°; thoracic curve final kyphosis: 45.3°; thoracolumbar curve postop CA: 31.2°; thoracolumbar curve final CA: 37.5°; thoracolumbar curve postop kyphosis: 22.8°; thoracolumbar curve final kyphosis: 27.8°; lumbar curve postop CA: 19.3°; lumbar curve final CA: 32.1°NoNA
Sirois & Drennan, 19905NANRNA1/16 (6%)0/16 (0%)Unclear (1)Pseudarthrosis: 5/16; hardware failure: 2/169/16: augmentation (4), inst dislocation (2), curve extension (2), increasing deformity (1)Pst fusion postop CA: 29° (range 12–58°); pst fusion final CA: 42° (range 18–68°)NoNA
Tauchi et al., 202033NA7/11 (64%)Atelectasis (5), reintubation (2), dural tear (1), lung injury (1)0/11 (0%)0/11 (0%)NAHardware failure: NR; pseudarthrosis: 1/119/11: augmentation (8), pseudarthrosis (1)Postop coronal CA: 24.1° (range 10–40°); postop thoracic kyphosis: 25.2° (range 14–36°); final coronal CA: 23.5° (range 14–57°); final thoracic kyphosis: 27.3° (range 11–44°)NoNA
Tauchi et al., 202034NA15/26 (58%)9/16 early-fusion pts: atelectasis (5), lung injury (1), dural tear (1), crankshaft phenomenon (1), vertebral dislocation (1), pneumonia (1), infection (8); 6/10 GR pts: hook dislodgment (8), rod breakage (1), infection (1), screw loosening (1)1/26 (4%)1/26 (4%)UnclearHardware failure: 2/26; pseudarthrosis: NR16/16: early fusion; 10/10: GRsEarly-fusion CA: 31.8 ± 14.8°; GR CA: 49.1 ± 16.8°; early-fusion thoracic kyphosis: 38.6 ± 25.7°; GR thoracic kyphosis: 49.5 ± 22.8°NoNA
Wang et al., 2015351393.8 mL (range 300–4400 mL)0/16 (0%)Postop hematoma (1)2/16 (13%)1/16 (6%)Nerve root (1), cord (1)0/160/16Postop CA: 27.6° (range 4–58°); postop kyphosis: 26.8° (range 15–55°); final CA: 30.4° (range 4–62°); final kyphosis: 27.4° (range 5–58°)NoNA
Wilde et al., 199436NA6/25 (24%)Superficial infections (2), halo pin infections (2), deep infections (2)3/25 (12%)0/25 (0%)Nerve root (1), unclear (2)NR5/25: hardware complication (1), infection (4)NRNoNA
Xu et al., 201937NA0/11 (0%)NA0/11 (0%)0/11 (0%)NAHardware failure: 1/11; pseudarthrosis: NA1/11CA after traction: 42.0° (range 35–75°); postop CA: 37.2° (range 29–63°); final CA: 33.6° (range 27–40°)NoNA
Yao et al., 201938NANRNANRNRNAHardware failure: 5/59; PJK: 2/59; adding on: 6/59; trunk shift: 5/59; curve progression: 3/592/32: initial fusion; 8/27: GRsPst fusion CA correction rate: 55.1% ± 25%; pst fusion kyphosis correction rate: 47.5% ± 25%; GR CA correction rate: 42.4% ± 23%; GR kyphosis correction rate: 56.3% ± 28%NoNA
Yao et al., 201839NANANA0/59 (0%)0/59 (0%)NA19 complications in 17/59 pts9 unplanned revisions in 7/59 pts (reasons not specified)NRNoNA
Zhao et al., 201640475 mL (range 330–740 mL)2/31 (6%)Dural tear (1), superficial infection (1)0/31 (0%)0/31 (0%)NA2/312/31: hook dislodgment, pseudarthrosisPostop CA: 21° (range 10–37°); postop kyphosis: 20° (range 10–39°)Yes, SRS-30No comparison made pre- & postop; mean SRS score at FU: 109 (range 97–135)

EBL = estimated blood loss; PJK = proximal junctional kyphosis; Perm = permanent; UTI = urinary tract infection.

Only reported for 15 patients who underwent posterior fusion with Harrington rods.

Fusing additional levels above or below the original site of surgical fusion.

Pathophysiology of Dystrophic Scoliosis

The characteristics of dystrophic scoliosis are well described, and bony dysplastic changes include rib penciling, vertebral body scalloping, spindling of the transverse process, widened interpediculate distance, and enlarged intervertebral foramina.2 These features are likely due to extra-, para-, and intraspinal tumor burden, growth, and mass effect resulting in osseous changes. Spinal tumors reportedly occur in 1.5% to 24% of patients with NF1, most of which are intraforaminal (56%), followed by intradural extramedullary (33%) and intramedullary (6%).41 Paraspinal neurofibromas are associated with increased apical vertebral rotation and rotatory subluxation.42 However, a number of additional factors contribute to their development and progression.7

Dural ectasia is reported in up to 29% of NF1 patients with dystrophic scoliosis and 11% of those with nondystrophic scoliosis.43 Dural ectasia is an abnormal expansion of the thecal sac with increased CSF space and associated dysmorphic bony findings (vertebral body scalloping and wedging); it is controversial whether this is due to abnormally high hydrostatic pressure.4446 Dural ectasia in dystrophic scoliosis may simply represent filling of the spinal canal as independent osseous changes occur. This is supported by findings of dysregulated bony metabolism in NF1 patients that are thought to contribute to de novo pathologic bone remodeling independent of external elements.4749 These pathological factors then lead to rapid curve progression, multiplanar deformity, biomechanical instability, neural compression, and eventually pulmonary compromise.3,5,7,911

Natural History of Dystrophic Scoliosis

NF1 dystrophic scoliosis classically has an early onset with rapid progression and results in kyphoscoliosis and spontaneous subluxation in severe untreated cases.3,5 Calvert et al. reported a case series of 32 patients managed with observation and conservative measures for a mean of 3.6 years.11 The mean coronal Cobb angle at presentation was 59°, and the mean rate of progression was 8.1° per year. The mean sagittal Cobb angle at presentation was 49°, and the mean rate of progression was 11.2° per year. Unlike idiopathic scoliosis, even mild to moderate curves (< 40°) progressed after skeletal maturity, and severe curves progressed more rapidly.11 Funasaki et al. suggested that vertebral body scalloping, greater than 11° of apical vertebral rotation, early onset, and larger curves were predictors of progression.50 Additionally, Calvert et al. observed that patients with severe anterior vertebral body scalloping experienced more curve progression, with average annual rates of 22.6° and 23.3° in the coronal and sagittal planes, respectively.11

Treatment Indications for Dystrophic Scoliosis

There is no clear census as to when conservative or surgical management should be considered for dystrophic scoliosis. Many surgeons practice the habits used for adolescent idiopathic scoliosis (AIS) as a starting framework.51,52 For skeletally immature patients, curves less than 20° are typically observed with serial imaging every 3–6 months. There is less consensus regarding patients with skeletal immaturity and curves between 20° and 40°; the options are observation, bracing (although controversial), and surgery. In this group, there is a general sense that these patients experience progression despite conservative measures, but the true natural history is not well described. Unlike AIS, corrective bracing for NF1 dystrophic scoliosis has fallen out of favor and is deemed contraindicated by some because of reported data describing its failure to control curves. The most commonly cited study is one published in 1979 by Winter et al. in which significant curve progression from an average of 53° to 80° in 10 patients who wore a brace for at least 12 months was demonstrated.9 Nine of the 10 patients underwent surgery, and the authors concluded “bracing [was] of no value” in the treatment of dystrophic scoliosis. In this systematic review, preoperative corrective bracing was used in 33.3% of studies, and 99.0% of those patients ultimately required surgery. Some surgeons posit that all moderate curves with dystrophic features warrant surgical intervention regardless of skeletal maturity or extent of the curve.3 In fact, many of the identified studies reported surgical outcomes of all dystrophic scoliosis patients, with curve thresholds of 20° to 35° and greater.1820,25,27,29

Surgical Considerations and Challenges

Tumor Resection

Up to 58% of NF1 patients have some form of spinal nerve sheath tumor, and nearly 30% have spinal plexiform neurofibromas; the incidence and tumor burden are even higher in patients with dystrophic scoliosis.53 None of the studies addressed the intricacies of tumor resection. In patients with extensive tumor burden (circumferential involvement), tumor resection is essential in order to expose the spine and aid in spinal deformity correction. Plexiform neurofibromas are unpredictability vascular.5,9,54 Meticulous hemostasis is crucial, especially for pediatric patients, as high-volume blood loss can lead to hemodynamic instability, clinical coagulopathy, and physiological extremis.55 The need for resection of intraspinal (foraminal, extradural, and/or intradural) tumors is based mainly on whether the tumor causes neurological deficits or puts the patient at risk for neurological compromise following deformity correction.53

Spinal Fixation and Instrumentation

Spinal fixation and instrumentation are key to achieving adequate correction of any spinal deformity. Furthermore, in order to perform high-grade osteotomies and corrective techniques, spinal fixation cannot be spared. In dystrophic scoliosis, dysplastic osseous changes can occur throughout the spinal column, making spinal fixation a challenging feat.2 Thirteen of the 30 studies specified that fixation techniques and constructs were used.1416,18,20,21,2427,29,35,37 Of the patients in these studies, 51.5% underwent pedicle screw–based constructs, 42.5% hybrid constructs, and 6.0% hook-based (Harrington rod) constructs. These studies spanned 5 decades, and the standard for spinal fixation has evolved from hooks to pedicle screw fixation. Wang et al. suggested that pedicle screw constructs have less loss of coronal correction at long-term follow-up compared with hybrid constructs.56 Pedicle morphology often dictates the fixation technique, and in many circumstances, severely dysplastic pedicles may not be appropriate for pedicle screws.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.25

While pedicle screw fixation offers the greatest control, reliability, and rigidity, other fixation techniques need to be considered for dystrophic scoliosis patients. Despite controversy over implant density in AIS,57,58 implant density in dystrophic scoliosis has a significant impact on scoliosis correction. Li et al. have shown that a higher implant density (hooks and screws) was correlated with both increased initial coronal correction (r = 0.505) and decreased loss of correction (r = −0.379); 55% of the low-implant-density group had a loss of greater than 5° compared with 19% in the high-implant-density group.29 Thus, a hybrid fixation construct, with pedicle screws at all segments amenable to them and hooks (laminar, pedicle, transverse process), laminar bands, and wires at levels with severe pedicle dysplasia, could help optimize high implant density.

Growing rods were used in 8 of the 30 studies across 110 patients.14,15,24,30,34,3739 Growing rod constructs were compared with fusion in 4 of these reports. The indications and timing of surgery were quite variable, and the outcomes were mixed. In 3 studies, growing constructs were associated with higher rates of implant-related complications and reoperation, a lower rate of curve correction, and worse pulmonary fuction.30,34,39 However, Cai et al. found growing constructs to result in fewer alignment complications with similar hardware-related complications compared with fusion.15

Use of High-Grade Osteotomies

Osteotomy use for scoliosis is highly dependent on training/comfort level and the goals of surgery. Most commonly, low-grade osteotomies (facetectomies and Ponte osteotomies) are used for less rigid scoliosis but do offer improved rotational and global correction.59 Among the identified studies, the details of low-grade osteotomy use are not readily reported. Assessing the utility and morbidity profile of osteotomy is not possible with the available data. Among the identified studies, 0.9% of the patients underwent VCR.60 The use of high-grade osteotomies in a patient with dystrophic scoliosis was first reported by Singh et al. in 2005, via a combined anterior-posterior approach.61 Stoker et al. similarly reported a case of a posterior-only approach in a patient with NF1 dystrophic kyphoscoliosis.62 Nearly 100° of kyphotic correction and complete coronal imbalance reduction were achieved in both patients. One patient experienced urinary retention, while the other remained intubated for 5 days postoperatively, but both ultimately recovered well. These case reports highlight that, while technically demanding, VCR can be performed in carefully selected patients with dystrophic scoliosis.

Dural Ectasia

Dural ectasia is common in dystrophic scoliosis, affecting more than 25% of NF1 patients.53 Dural ectasia can result in intraoperative challenges and postoperative complications, particularly when decompressions or osteotomies are performed, due to the increased risk of CSF leaks. While associations between dural ectasia and postoperative complications were not specifically reported across the identified studies, some reports have discussed anecdotal evidence suggesting a higher risk of complications in the setting of dural ectasia. Winter et al. reported on 2 patients who experienced postoperative paralysis due to unexpected areas of laminar erosion from dural ectasia.9 When CSF leaks are encountered, they can be difficult to primarily repair, leaving patients at risk for further complications, including wound complications and both septic and aseptic meningitis.

Case Illustration: Dystrophic Kyphoscoliosis

To further illustrate surgical considerations and challenges encountered in severe cases of dystrophic scoliosis, we present the following case illustration. A 16-year-old male with NF1 (diagnosed at age 5 years) presented with progressive lumbar kyphoscoliosis and the following measurements: sagittal vertical axis (SVA) of 7.8 cm, coronal vertical axis (CVA) of 0 cm, T12–L2 levoscoliosis of 103°, L2–5 dextroscoliosis of 112°, lumbar kyphosis of 51° (apex at L2), pelvic incidence of 60°, and pelvic tilt of 17° (Fig. 2A and B). Lateral bending demonstrated a rigid deformity (Fig. 2C and D). The patient had extensive plexiform neurofibromas encasing his retroperitoneal cavity and entire right lower extremity (Fig. 3A and B). His plexiform neurofibroma extended through the foramen and intradurally at L2–3. Diffuse lumbar dural ectasia was evident (Fig. 3C). With the exception of difficulty moving his right leg due to the weight of the neurofibromas, he was neurologically intact and able to stand. The patient underwent T9–pelvis instrumentation and fusion, multilevel Smith-Petersen osteotomies, and an L2 extended pedicle subtraction osteotomy. Because of the dysplastic pedicles and vertebral rotation, navigation and laminar bands were used at the curve apex (Fig. 4). The exposure required extensive paraspinal tumor resection (Fig. 5A and B). The final correction and hybrid construct of pedicle screws and laminar bands at the apex can be seen in Fig. 5C. The estimated blood loss was 1500 mL. Postoperative images revealed significant correction with maintained global balance: SVA 0 cm, CVA 0 cm, T12–L2 levoscoliosis 23°, L2–5 dextroscoliosis 27°, and lumbar lordosis 31° (Fig. 6). The patient was discharged home without complications.

FIG. 2.
FIG. 2.

Preoperative lateral (A), anteroposterior (B), anteroposterior with rightward bending (C), and anteroposterior with leftward bending (D) standing whole-spine radiographs demonstrating the degree of spinal deformity.

FIG. 3.
FIG. 3.

A: Preoperative standing whole-body radiograph demonstrating the extent of the patient’s limb asymmetry. B: Preoperative MR images demonstrating the extent of the patient’s right lower-extremity plexiform neurofibroma burden. The inset is an axial section demonstrating the neurofibroma’s size. C: Preoperative lumbar spine MR images demonstrating the paraspinal plexiform neurofibromas with dural ectasia in the lumbosacral spine.

FIG. 4.
FIG. 4.

Preoperative CT scans demonstrating extensive pedicle dysplasia and vertebral rotation, particularly at the apex of the curve.

FIG. 5.
FIG. 5.

Intraoperative photographs demonstrating the plexiform neurofibroma and curve architecture (A), resected neurofibroma measuring approximately 10 cm in length (B), and placement of segmental instrumentation (C).

FIG. 6.
FIG. 6.

Postoperative lateral (left) and anteroposterior (right) standing whole-spine radiographs demonstrating correction of the deformity, restoration of lumbar lordosis, and a balanced sagittal alignment.

Perioperative Complications and Neurological Morbidity

Nonneurological perioperative complications were reported in 20 of the 30 studies, and the overall complication rate was 14.0%. The rates between studies were quite variable, with a range of 0% to 72%, and the classification of specific complications was heterogeneous. Tauchi et al. reported a 64% complication rate (7 of 11 patients), although 5 of these complications were atelectasis.34 Whether this atelectasis led to a clinically significant change in management was not specified. The most common complications reported were wound infections (4.2%) and dural tears (2.4%), although many individual complications were not identified separately. Other major but less frequent complications included postoperative hematoma with cord compression and pulmonary complications (direct injury and hemothorax).17,22,3335

The overall incidences of temporary postoperative and permanent neurological deficits were 2.1% and 1.2%, respectively. In other words, 58.3% of new postoperative deficits persisted at the last follow-up. The type of neurological injury was only reported in a few studies and included both nerve root and spinal cord injuries.11,17,22,26,30,35,36 Spinal cord injuries tended to remain permanent, with 6 of the 7 permanent neurological deficits involving the spinal cord, as opposed to only 1 nerve root deficit.

Radiographic Correction

Coronal scoliosis curve measurements were reported preoperatively in 93.3% of articles and postoperatively in 76.7% of articles.5,11,1416,1840 The coronal Cobb angle at the time of surgery ranged from 47° to 125°, with a mean of 75.2°. Thoracic kyphosis measurements were reported preoperatively in 66.7% of articles and postoperatively in 50%.14,16,1823,2536,3840 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. The mean overall correction in the coronal plane was 40.3° and in the sagittal plane was 23.6°.

A smaller number of studies (46.7%) reported on follow-up radiographic measurements.5,11,14,16,18,19,23,24,26,31,32,34,35,37 The mean coronal scoliosis and thoracic kyphosis at the time of last follow-up were 33.8° (range 23.5°–56°) and 33.8° (range 24.1°–60.6°), respectively. The loss of coronal correction at the final follow-up was noted in the majority of these studies (72.7%); this loss was on average greater than 10°.5,11,14,16,18,19,23,24,27,31,32,34,35,37 Loss of sagittal plane correction at final follow-up occurred in 100% of the studies, but this loss did not exceed 10°.11,14,16,18,19,23,27,31,32,34,35 There was a relatively high rate of curve progression following fusion for dystrophic scoliosis in both the skeletally immature and mature patients. Wilde et al. followed 25 NF1 patients who underwent fusion for dystrophic scoliosis for an average of 9.7 years (range 2–24 years).36 Thirteen patients had curves that progressed more than 10° despite only one occurrence of pseudarthrosis. Patients with hyperkyphosis (kyphosis > 50° and sharp angulation over 3 vertebrae) had the greatest risk of progression, with a mean curve deterioration of 38° at the final follow-up. Additional prognostic features for postoperative curve progression included vertebral subluxation, disc wedging, and peripheral skeletal dystrophy. In a study by Parisini et al., 22 of 56 patients who underwent deformity surgery for dystrophic scoliosis required reoperation, 16 of which were for curve progression and 6 of which were for complete relapse, although further information on the reasons for these progressions/relapses was not provided.31

Revision Surgery: Mechanical Complications

Among the identified studies with follow-up outcome data, the overall revision rate was 21.5%, with individual reoperation rates ranging from 0% to 82% (Table 1). The specific reasons for reoperation were not reported in many studies, but mechanical complications seem to be the most common reason. Mechanical complications were reported in 24 studies, and there were 141 events of mechanical complications.5,11,1420,2224,2630,3335,3740 Few reports specified the type of mechanical complication, but there were 10 instances of proximal junctional kyphosis, 10 instances of rod breakage, 16 instances of screw or anchor loosening, 11 further instances of unspecified hardware complications, and 23 instances of pseudarthrosis. Because of the lack of specification in the reports, it was not possible to calculate the proportion of mechanical complications requiring reoperation.

Patient-Reported Outcomes

Very few studies (17%) reported PROMs, and not all of those studies reported incremental changes before and after surgery.13,23,2628,40 Iwai et al. and Zhao et al. provided postoperative SRS-22 and SRS-30 scores without any comparative metrics.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.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.

Discussion

NF1 dystrophic scoliosis is an early-onset, rapidly progressive, debilitating spinal deformity, and its management and surgical treatment are extremely challenging. There is accumulating evidence that dystrophic scoliosis is the result of multiple etiologies: tumor burden, mass effect, dural ectasia, asymmetrical growth of endplates, abnormal bony metabolism, and biomechanical instability.2,7 Corrective brace therapy is not effective, even for mild to moderate curves less than 40°, and the majority of patients experience curve progression despite brace compliance and ultimately require surgery.11 In early-onset, skeletally immature patients with large dystrophic curves, growing constructs can be considered a viable option. There are little and mixed outcomes. If possible, waiting for definitive fusion seems most optimal. The dystrophic features lead to significant intraoperative challenges. Extensive tumor burden requires adequate tumor resection, but this is not a focus of past studies and should be further emphasized. While posterior neurofibromas are generally nonfunctional and tumor resection does not cause neurological deficits, deciding when tumor resection is sufficient and managing blood loss can be challenging. Careful thought should be given to early transfusions or staging surgeries in younger pediatric patients with small blood volumes.

Many of the studies identified are 2 to 3 decades old, and surgeons have come to rely mainly on pedicle screws for fixation. However, in patients with dysplastic pedicles, this may not be possible, even with the use of navigation. 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 operative 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.29 Navigation is essential to maximizing the placement of pedicle screws, and at dysplastic levels, hooks and laminar bands should be used.

The extent of deformity correction is variable and highly dependent on various factors, including the goals of surgery, severity of deformity, and anatomical considerations. Correction in the coronal and sagittal planes was moderate, at 40.3° and 23.6°, respectively. It is difficult to interpret whether this correction was sufficient without more global spinal measures. In fact, there may be a component of undercorrection. Fewer than 1% of patients underwent a VCR or high-grade osteotomy for deformity correction. This seems quite low given the frequency with which surgeons encounter rigid and severely deformed dystrophic curves. This low rate of high-grade osteotomy use could be related to the steep learning curve, inability to gain adequate fixation at the apex of curves, presence of dural ectasia, and/or surgical goals (stabilization vs correction).63

The perioperative complication rate of 14% seems appropriately high, particularly when compared with complication rates in AIS surgery. On the other hand, the postoperative neurological deficit rate was surprisingly low at approximately 2%, with 1% remaining permanent. In comparison, the neurological deficit rate following VCR in the correction of severe pediatric deformity is around 10%.64 The reasons for the low incidence of neurological deficits are unclear but most likely relate to the methodology used for defining and reporting complications. The low neurological morbidity could also represent less-aggressive approaches to deformity correction, as represented by the low rates of high-grade osteotomy. The majority of permanent deficits were associated with spinal cord rather than nerve root injuries, which is a direct result of the higher incidence of thoracic curves. Neurological deficits from spinal cord injury following the correction of dystrophic curves also have a lower chance of recovery (58.3% with residual deficit). In comparison, other types of pediatric deformity have an approximately 10% incidence of residual deficits.65,66 This might be a reflection of inconsistent data reporting throughout studies and/or be due to intraspinal dystrophic anomalies.

Patients with dystrophic scoliosis are at particularly high risk for revision surgery (> 20%), mostly because of mechanical complications. Preventing such complications requires a detailed understanding of biomechanical failure and the implementation of risk mitigation strategies. Many of the preventative mechanisms for rod fractures and junctional failure used in adult spinal deformity can be translated to dystrophic scoliosis cases, including multiple rods, cement augmentation, the use of hooks in the proximal thoracic region, and ligament augmentation.6769 Despite the need for reoperation, available PROMs support the findings that patients are satisfied with surgery and have improvements in the mental health, self-image, and activity domains on SRS questionnaires.27,28

Taking into consideration the aforementioned challenges with dystrophic scoliosis, our modern framework to surgery consists of 3 main strategic approaches: adequate preoperative planning/optimization, optimal execution of the surgical plan, and overcoming postoperative morbidity. More specifically, each patient is discussed in a multidisciplinary NF1 conference in which a comprehensive, agreeable goal is set. By combining intraoperative enabling technology with advanced surgical techniques (for spinal fixation and osteotomies), surgical plans are accomplished in a succinct manner to achieve goal deformity correction. Modern medicine has also allowed us to mitigate and overcome perioperative complications to ensure the best clinical outcome possible. This systematic approach helps in achieving adequate deformity correction while minimizing perioperative morbidity and mechanical complications compared with historic cohorts.

There are several limitations to this review that reflect the lack of large granular studies available on NF1 dystrophic scoliosis. The search criteria were intentionally broad to capture as many patients as possible, but this led to inconsistent data points between studies. This heterogeneity between studies prevented a true meta-analysis from being performed. In addition, there are very little high-quality, prospective data regarding the management of dystrophic scoliosis. Nonetheless, this review provides a detailed overlook of the management care plan and surgical outcomes of patients undergoing dystrophic scoliosis surgery.

Conclusions

Surgery for dystrophic scoliosis in NF-1 remains a challenging endeavor, with high complication and revision rates. A lack of granularity and consistency in the current literature base make it difficult to draw strong conclusions regarding best practices for this patient population. However, a number of strategies exist for mitigating complications and optimizing outcomes. Future multicenter, prospective research efforts are greatly needed to further understand how to mitigate morbidity and optimize surgical outcomes for deformity correction in NF1 patients with dystrophic scoliosis.

Appendix

The search term used was (Neurofibromatosis[Title/Abstract]) AND ((Dystrophic[Title/Abstract]) OR (Scoliosis[Title/Abstract])). Two reviewers (S.N.N. and H.A.K.) independently screened all papers found initially by title and abstract. For full-text review, all papers were independently screened by the same two reviewers, and there were no disputes as to whether to include certain reports. No measurements of bias or uncertainty were assessed, and no formal meta-analysis was performed. The review was not registered. There were no sources of outside funding. Data extracted in performing this systematic review are available on request.

Disclosures

Dr. Samdani: consultant for DePuy Synthes Spine, Ethicon, Globus Medical, Medical Device Business Services, Mirus, NuVasive, Orthofix, Stryker, and Zimmer Biomet; Board of Directors and Executive Committee member of Setting Scoliosis Straight Foundation; and Executive Committee member of Pediatric Spine Study Group. Dr. Hwang: speakers bureau for NuVasive, Stryker, and Zimmer Biomet; direct stock ownership in Auctus; and travel fees from and board member of NASS.

Author Contributions

Conception and design: Lau, Neifert, Khan, Yohay, Segal, Samdani, Hwang. Acquisition of data: Lau, Neifert, Khan. Analysis and interpretation of data: Lau, Neifert, Khan. Drafting the article: Lau, Neifert, Khan, Kurland, Kim. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Lau. Statistical analysis: Neifert, Khan. Administrative/technical/material support: Lau, Yohay, Segal, Samdani, Hwang. Study supervision: Lau, Kurland, Kim, Yohay, Segal, Samdani, Hwang.

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Figure from Shahrestani et al. (E3). Created with Biorender.com.

  • View in gallery

    PRISMA diagram for systematic review.

  • View in gallery

    Preoperative lateral (A), anteroposterior (B), anteroposterior with rightward bending (C), and anteroposterior with leftward bending (D) standing whole-spine radiographs demonstrating the degree of spinal deformity.

  • View in gallery

    A: Preoperative standing whole-body radiograph demonstrating the extent of the patient’s limb asymmetry. B: Preoperative MR images demonstrating the extent of the patient’s right lower-extremity plexiform neurofibroma burden. The inset is an axial section demonstrating the neurofibroma’s size. C: Preoperative lumbar spine MR images demonstrating the paraspinal plexiform neurofibromas with dural ectasia in the lumbosacral spine.

  • View in gallery

    Preoperative CT scans demonstrating extensive pedicle dysplasia and vertebral rotation, particularly at the apex of the curve.

  • View in gallery

    Intraoperative photographs demonstrating the plexiform neurofibroma and curve architecture (A), resected neurofibroma measuring approximately 10 cm in length (B), and placement of segmental instrumentation (C).

  • View in gallery

    Postoperative lateral (left) and anteroposterior (right) standing whole-spine radiographs demonstrating correction of the deformity, restoration of lumbar lordosis, and a balanced sagittal alignment.

  • 1.

    Gutmann DH, Ferner RE, Listernick RH, Korf BR, Wolters PL, Johnson KJ. Neurofibromatosis type 1. Nat Rev Dis Primers. 2017;3 17004.

  • 2.

    Crawford AH, Herrera-Soto J. Scoliosis associated with neurofibromatosis. Orthop Clin North Am. 2007;38(4):553562, vii.

  • 3.

    Crawford AH, Parikh S, Schorry EK, Von Stein D. The immature spine in type-1 neurofibromatosis. J Bone Joint Surg Am. 2007;89(suppl 1):123142.

  • 4.

    Larson AN, Ledonio CGT, Brearley AM, et al. Predictive value and interrater reliability of radiographic factors in neurofibromatosis patients with dystrophic scoliosis. Spine Deform. 2018;6(5):560567.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5.

    Sirois JL III, Drennan JC. Dystrophic spinal deformity in neurofibromatosis. J Pediatr Orthop. 1990;10(4):522526.

  • 6.

    Holt RT, Johnson JR. Cotrel-Dubousset instrumentation in neurofibromatosis spine curves. A preliminary report. Clin Orthop Relat Res. 1989;(245):1923.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7.

    Weinstein S. The Pediatric Spine: Principles and Practice. 2nd ed. Lippincott Williams & Wilkins;2001.

  • 8.

    Kim HW, Weinstein SL. Spine update. The management of scoliosis in neurofibromatosis. Spine (Phila Pa 1976). 1997;22(23):27702776.

  • 9.

    Winter RB, Moe JH, Bradford DS, Lonstein JE, Pedras CV, Weber AH. Spine deformity in neurofibromatosis. A review of one hundred and two patients. J Bone Joint Surg Am. 1979;61(5):677694.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10.

    Winter RB, Lonstein JE, Anderson M. Neurofibromatosis hyperkyphosis: a review of 33 patients with kyphosis of 80 degrees or greater. J Spinal Disord. 1988;1(1):3949.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11.

    Calvert PT, Edgar MA, Webb PJ. Scoliosis in neurofibromatosis. The natural history with and without operation. J Bone Joint Surg Br. 1989;71(2):246251.

  • 12.

    Page MJ, McKenzie JE, Bossuyt PM, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021;372(71):n71.

  • 13.

    Betz RR, Iorio R, Lombardi AV, Clancy M, Steel HH. Scoliosis surgery in neurofibromatosis. Clin Orthop Relat Res. 1989;(245):53-56.

  • 14.

    Bouthors C, Dukan R, Glorion C, Miladi L. Outcomes of growing rods in a series of early-onset scoliosis patients with neurofibromatosis type 1. J Neurosurg Spine. 2020;33(3):373380.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15.

    Cai S, Cui L, Qiu G, Shen J, Zhang J. Comparison between surgical fusion and the growing-rod technique for early-onset neurofibromatosis type-1 dystrophic scoliosis. BMC Musculoskelet Disord. 2020;21(1):455.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16.

    Cai S, Li Z, Qiu G, et al. Posterior only instrumented fusion provides incomplete curve control for early-onset scoliosis in type 1 neurofibromatosis. BMC Pediatr. 2020;20(1):63.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 17.

    Chaglassian JH, Riseborough EJ, Hall JE. Neurofibromatous scoliosis. Natural history and results of treatment in thirty-seven cases. J Bone Joint Surg Am. 1976;58(5):695702.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18.

    Cinnella P, Amico S, Rava A, Cravino M, Gargiulo G, Girardo M. Surgical treatment of scoliosis in neurofibromatosis type I: a retrospective study on posterior-only correction with third-generation instrumentation. J Craniovertebr Junction Spine. 2020;11(2):104110.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19.

    Deng A, Zhang HQ, Tang MX, Liu SH, Wang YX, Gao QL. Posterior-only surgical correction of dystrophic scoliosis in 31 patients with neurofibromatosis Type 1 using the multiple anchor point method. J Neurosurg Pediatr. 2017;19(1):96101.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20.

    Greggi T, Martikos K. Surgical treatment of early onset scoliosis in neurofibromatosis. Stud Health Technol Inform. 2012;176(330):333.

  • 21.

    Halmai V, Domán I, de Jonge T, Illés T. Surgical treatment of spinal deformities associated with neurofibromatosis type 1. Report of 12 cases. J Neurosurg. 2002;97(3)(suppl):310316.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 22.

    Hsu LC, Lee PC, Leong JC. Dystrophic spinal deformities in neurofibromatosis. Treatment by anterior and posterior fusion. J Bone Joint Surg Br. 1984;66(4):495499.

    • Crossref
    • PubMed
    • Search Google Scholar
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