Effect of higher implant density on curve correction in dystrophic thoracic scoliosis secondary to neurofibromatosis Type 1

Vertebral Column Subluxation in Neurofibromatosis Type 1-Associated Dystrophic Scoliosis: A Report of Two Cases and Narrative Review

BACKGROUND AND OBJECTIVE

Neurofibromatosis-1 (NF1) dystrophic scoliosis is a challenging disease to manage surgically, with multiplanar curves progressing rapidly and unpredictably. Conservative management with bracing is often unsuccessful, and many patients necessitate instrumented fusion to halt progression of their curves. In rare cases, patients can present with spontaneous vertebral subluxation, significantly complicating the surgical management of this already complex disease process. The objective here was to describe 2 cases of vertebral subluxation in NF1-associated dystrophic scoliosis along with their surgical corrections and clinical courses.

METHODS

A retrospective review of 2 cases at the authors' institution was performed to describe their preoperative symptom complexes, surgical corrections, and postoperative courses. A narrative review of the literature surrounding NF1-associated dystrophic scoliosis and subluxation is also presented.

RESULTS

Two cases of vertebral subluxation at T4-5 and C7-T1 are presented. Both patients had significant dystrophic features throughout their spines, and halo-gravity traction was unsuccessful in 1 patient and led to vertebral and subclavian artery injuries in the other. One patient underwent an uncomplicated deformity correction with partial vertebral column resection to facilitate his deformity correction. The other patient, after her vascular injuries, ultimately suffered a spinal cord injury after a fall and underwent emergent instrumentation, decompression, and partial vertebral column resection at the site of subluxation, with improvement in her neurological function afterward.

CONCLUSION

Dystrophic scoliosis in NF1 remains a difficult disease to treat, and deformity correction in patients with subluxation is particularly complex. These cases here highlight the unpredictability and possible complications of halo-gravity traction, need for good fixation to facilitate subluxation reduction, high chance of hardware complications and proximal or distal failure, and importance of cooperative management of these patients in conjunction with other surgical services.

Clinical features and surgical treatments of scoliosis in neurofibromatosis type 1: a systemic review and meta-analysis

BACKGROUND

Neurofibromatosis type 1 (NF 1) is an autosomal-dominant tumor predisposition genetic disease affecting approximately 1 in 3000 live births. The condition could present various manifestations ranging from skin abnormalities to neurological tumors. The musculoskeletal system could also be frequently affected, and scoliosis is the most common orthopedic manifestation. Characterized by the early-onset and rapid progression tendency, NF 1-related dystrophic scoliosis presented discrepancies from idiopathic scoliosis in terms of natural history, clinical features, and management outcomes and thus required special attention. In the current study, the authors conducted a systemic review to outline the body of evidence of the natural history, clinical characteristics, surgical outcomes, and surgical complications of NF 1-induced scoliosis, aiming to provide an elucidative insight into this condition.

METHOD

Systemic review and meta-analysis were conducted according to the latest Preferred Reporting Items for Systematic Reviews Meta-Analyses (PRISMA) guidelines. The search was performed in Medline, Embase, and Web of Science Core Collection up to December 27, 2022, using related keywords. Clinical features such as frequencies, segmental involvement, and hereditary information were summarized and described qualitatively. Meta-analysis was conducted using R software and the 'meta' package to yield an overall outcome of efficacy and safety of surgical management, precisely, spinal fusion procedure and growing rods procedure. Corrective rate of Cobb angle, sagittal kyphosis angle, and T1-S1 length post-operative and at the last follow-up was used to evaluate the efficacy, and the occurrence of surgery-related complications was used to evaluate the safety.

RESULT

A total of 37 articles involving 1023 patients were included. Approximately 26.6% of the NF 1 patients would present with scoliosis. Patients tend to develop scoliosis at an earlier age. The thoracic part turned out to be the most affected segment. No obvious correlation between scoliosis and genotype or hereditary type was observed. Both spinal fusion and growing rod surgery have shown acceptable treatment outcomes, with spinal fusion demonstrating better performance in terms of effectiveness and safety. The growing rods technique seemed to allow a better lengthening of the spine. The mainstay post-operative complications were implant-related complications but could be managed with limited revision surgery. Severe neurological deficits were rarely reported.

CONCLUSION

Scoliosis, especially the subtype characterized by dystrophic bony changes, is a significant orthopedic manifestation of NF1. It has an early onset, a tendency to persistently and rapidly progress, and is challenging to deal with. The current review outlines the available evidence from the perspective of natural history, clinical features, and the treatment efficacy and safety of the mainstay surgical options. Patients with NF1 scoliosis will benefit from a better understanding of the disease and evidence based treatment strategies.

Functional and Radiological Outcomes of All-Posterior Surgical Correction of Dystrophic Curves in Patients with Neurofibromatosis Type 1

STUDY DESIGN

A retrospective cohort study.

PURPOSE

To determine outcomes following all-posterior surgery using computed tomography navigation, hybrid stabilization, and multiple anchor point techniques in patients with neurofibromatosis type 1 (NF-1) and dystrophic scoliosis.

OVERVIEW OF LITERATURE

Previous studies favored antero-posterior fusion as the most reliable method; however, approaching the spine anteriorly was fraught with significant complications. With the advent of computer assisted navigation and multiple anchor point method, posterior only approach is reporting successful outcomes.

METHODS

This study included patients who underwent all-posterior surgical deformity correction for dystrophic NF-1 curves. Coronal and sagittal Cobbs angles, apical rotation, and the presence of dystrophic features were evaluated before surgery. Postoperatively, sagittal, coronal, and axial correction, implant position, and implant densities were evaluated. The decline in curve correction and implant-related complications were evaluated at follow-up. Clinical outcomes were evaluated using the Scoliosis Research Society-22 revised index.

RESULTS

This study involved 50 patients with a mean age of 13.6 years and a mean follow-up duration of 5.52 years. With a mean coronal flexibility of 18.7%, the mean apical vertebral rotation (AVR), preoperative coronal Cobb angle, and sagittal kyphosis were 27.4°, 64.01°, and 47.70°, respectively. The postoperative mean coronal Cobb angle was 30.17° (p <0.05), and the sagittal kyphosis angle was 25.4° (p <0.05). The average AVR correction rate was 41.3%. The correction remained significant at the final mean follow-up, with a coronal Cobb angle of 34.14° and sagittal kyphosis of 25.02° (p <0.05). The average implant density was 1.41, with 46% of patients having a high implant density (HID). The HID had a markedly higher mean curve correction (29.30° vs. 38.05°, p <0.05) and a lower mean loss of correction (5.7° vs. 3.8°, p <0.05).

CONCLUSIONS

Utilizing computer-assisted navigation, hybrid instrumentation, and multiple anchor point technique and attaining high implant densities, this study demonstrates successful outcomes following posterior-only surgical correction of dystrophic scoliosis in patients with NF-1.

A Novel Hybrid Technique in the Treatment of Dystrophic Scoliosis Secondary to Neurofibromatosis Type 1 Lacking Pedicles in the Apical Area

STUDY DESIGN

A retrospective observational study.

OBJECTIVE

To introduce a novel hybrid technique using segmentation correction (SC) and to compare it with traditional correction (TC) in treating dystrophic scoliosis secondary to neurofibromatosis type 1 (NF1-S) lacking pedicles in the apical area.

METHODS

We reviewed the NF1-S cases lacking pedicles diagnosed in our hospital between January 2015 and December 2019. Patients were divided into the SC and TC groups and were followed up for at least 2 years. The degree of deformities, correction rate, and vertebral rotatory subluxation (RS) were assessed before the operation, post-traction, post operation, and during follow-up visits.

RESULTS

A total of 27 patients were included in the SC group and 21 in the TC group. There was no significant difference in the 2 groups before the surgery regarding age, height, weight, degree of deformities, and spinal flexibility. The correction rate of patients in the SC group was higher (57.7% ± 17.3% vs. 40.9% ± 19.0%, P = 0.002) than in the TC group. During the 2-year follow-up, the loss of Cobb angles of the SC group in both coronal and sagittal planes were lower than those of the TC group (coronal plane, 1.2° ± 1.1° vs. 2.0° ± 1.4°, P = 0.039; sagittal plane, 0.9° ± 0.5° vs. 1.7° ± 1.0°, P = 0.002).

CONCLUSIONS

The SC technique showed better deformity correction than TC, suggesting that SC may be an alternative method for treating NF1-S patients lacking pedicles in the apical area.

The Utilization of Dual Second Sacral Alar-Iliac Screws for Spinopelvic Fixation in Patients with Severe Kyphoscoliosis

OBJECTIVES

As a new pelvic fixation technique, the dual S2AI screws fixation technique could provide highly stable distal strength, and have wide clinical prospect in the correction of severe kyphoscoliosis. However, the ideal trajectory parameters, indications and clinical outcomes of this technique have not been reported so far. This study aimed to determine the anatomical parameters of dual S2AI screws in the normal Chinese adult population, investigating the indications of this technique and evaluating the feasibility and clinical outcomes.

METHODS

Fifteen males and 15 females with normal pelvis underwent a pelvic CT scan to determine ideal dual S2AI screws trajectories. Sagittal angle (SA), transverse angle (TA), maximal length (ML), sacral length, and skin distance were measured. Subsequently, we retrospectively reviewed the data of 16 patients (seven males and nine females) who underwent dual S2AI screw fixation and 23 patients who underwent single S2AI screw fixation between January 2014 and December 2019. Preoperative, postoperative, and latest follow-up measurements of Cobb angle, coronal balance (CB), spinal pelvic obliquity (SPO), and regional kyphosis (RK) were obtained. The mean follow-up time was 16.7 ± 7.1 months (range: 12-30 months). Independent t-test was used to determine the difference in the analysis of the trajectories. The paired sample non-parametric Wilcoxon test was performed to assess the changes in radiographic parameters between different time points and different groups.

RESULTS

For both male and females, the proximal S2AI screws had significantly higher TA and ML, but a lower SA than distal screws. Females showed significantly more caudal (SA: 25.03° ± 2.32° vs. 29.82° ± 2.47°, t = 7.742, P < 0.001) trajectories of distal screw. Additionally, ML in the females were significantly shorter than that in males (106.81 mm ± 6.79 mm vs. 101.63 mm ± 6.55 mm, t = 3.007, P = 0.003, 124.41 mm ± 7.57 mm vs. 116.23 mm ± 7.03 mm, t = 4.337, P < 0.001). Eight had unilateral and eight had bilateral dual S2AI screw placement. Respectively, both the single S2AI and dual S2AI groups showed significant postoperative improvement of Cobb angle, RK angle and SPO angle. In patients with dual S2AI screws fixation, two patients found that screws loosening occurred in one of dual screws at 1-year follow-up, and in patients with single S2AI screws fixation, six patients found screw loosing as well as two patients found screw breakage at 1-year follow-up. None of all patients had any prominent loss of correction.

CONCLUSION

The ideal trajectory of dual S2AI screw could be well established. The dual S2AI screw fixation technique is feasible in patients with severe kyphoscoliosis, and provides satisfactory correction of deformity with few postoperative complications.

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

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.

Surgical outcomes of severe spinal deformities exceeding 100° or treated by vertebral column resection (VCR). Does implant density matter?: an observational study of deformity groupings

STUDY DESIGN

Prospective multicenter international observational study.

OBJECTIVE

To investigate the effect of implant density on clinical outcomes in complex pediatric spine reconstruction. Implant density in spine deformity surgery has been a subject of much debate with some authors advocating higher density for better correction. Few studies have looked at the effect of implant density on severe curves > 100 deg or treated with vertebral column resection (VCR).

METHODS

250/311 pts with 2-year f/u enrolled in the FOX pediatric database from 17 international sites were queried for the impact of implant density and surgical outcomes. Patients were grouped into three implant density categories for comparative analysis Group 1 (density ≤ 1), Group 2 (1 < density < 1.5) and Group 3 (density; 1.5-2).

RESULTS

250 pts: 47 (Grp1)/99 (Grp2) /104 (Grp3); Pre-op age and etiology and curve types were similar in all groups, but body mass index (BMI) was higher in Grp3. Grps 1 and 2 had significantly higher sagittal deformity angular ratio (S-DAR) compared to Grp 3 (p < 0.001). Pre-op Halo Gravity Traction (HGT) was used in 55.3%/44.4%/31.7%, p = 0.017; Grp1/Grp2/Grp3, respectively. Average duration of surgery (min) was higher in Grp3 relative to Grp1 only: 352.5/456.5/515.0, p = 0.0029. Blood loss was similar in all Grps. Rate of VCR, PSO and SPO was similar in all Grps. Pre-op Coronal Cobb avg 96.1/83.6/88.6, p = 0.2342, attained similar correction after HGT (24.6%/27.2%/23.2%, p = 0.4864. Coronal Cobb corrections at 2-year follow-up (FU) were (37.1%/40.3%/53.5%, p = 0.0004). Pre-op sagittal Cobb was (105.4/101.9/75.9, p < 0.01.), achieved similar %correction in HGT (19.1%/22.3%/22.5%, p = 0.6851) and at 2-year FU (39.6%/41.4%/29.8%, p = 0.1916). After adjusting for C-DAR, S-DAR, pre-op coronal and sagittal Cobb, etiology, curve types, age, BMI and number of rods in multivariate analysis, the odds of developing post-operative implant complication was 11 times greater in group 1 compared to group 3 (OR = 11.17,95% CI 2.34-53.32). There was significant improvement in SRS scores in all Grps at 2-year FU.

CONCLUSION

Although higher implant density was observed to be associated with greater curve correction and lower rates of post-operative implant-related complication and revision in heterogeneous case groups, the results may not imply causality of implant density on the outcomes in severe pediatric spine reconstruction.

Could screw/hook insertion at the apical vertebrae with rib head dislocation effectively retract the corresponding rib head from spinal canal in dystrophic scoliosis secondary to type 1 neurofibromatosis?

Background

Rib head dislocation (RHD) in dystrophic scoliosis of type 1 neurofibromatosis (DS-NF1) is a unique disorder caused by skeletal dystrophy and scoliotic instability. No particular surgical manipulation is mentioned in the literature to instruct the spine surgeons to effectively obtain more migration of the dislocated rib head without resection. The present study aimed to investigate the effectiveness of screw/hook insertion at vertebrae with RHDs on the retraction of penetrated rib head from spinal canal.

Methods

37 neurologically intact patients with DS-NF1 and concomitant 53 RHDs undergoing scoliosis surgery without rib head excision were retrospectively reviewed. We used pre and postoperative whole-spine radiographs to determine the Cobb angle and the vertebral translation (VT), and the CT scans to evaluate the intraspinal rib length (IRL) and rib-vertebral angle (RVA). The dislocated ribs were assigned into two groups according to the presence of screw/hook insertion at vertebrae with RHD: screw/hook group and non-screw/hook group.

Results

37 dislocated ribs with screws/hooks insertion at corresponding vertebrae were assigned into the screw/hook group and the remaining 16 dislocated ribs consisted of the non-screw/hook group. In the screw/hook group, the correction rates of Cobb angle and VT were significantly higher than the non-screw/hook group after surgery (58.7 ± 16.0% vs. 30.9 ± 12.4%, p = 0.003; 61.8 ± 18.8% vs. 35.1 ± 16.6%, p = 0.001; respectively). Similarly, more correction rates of IRL and RVA were found in the screw/hook group than the non-screw/hook group (63.1 ± 31.3% vs. 30.1 ± 20.7%, p = 0.008; 17.6 ± 9.7% vs. 7.2 ± 3.6%, p = 0.006; respectively). Multiple linear regression analysis revealed that the correction rates of Cobb angle, VT and RVA contributed significantly to correction of IRL (β = 0.389, 0.939 and 1.869, respectively; p = 0.019, 0.001 and 0.002, respectively).

Conclusion

Screw/hook insertion at dystrophic vertebrae with RHDs contributed significantly to the degree of retraction of penetrated rib head from spinal canal. This effectiveness is mediated by more corrections of VT and RVA.

Anatomical changes in vertebra in dystrophic scoliosis due to neurofibromatosis and its implications on surgical safety

STUDY DESIGN

Detailed radiological analysis by multimodality imaging.

OBJECTIVE

To document anatomical changes jeopardizing instrumentation safety in Neurofibromatosis deformity correction surgeries.

MATERIALS AND METHODS

The apical and 3 adjacent vertebral segments above and below amounting to 70 segments in 10 NF scoliosis were studied by radiographs, CT and MRI. The changes in lamina, pedicle and vertebral body that could jeopardize pedicle screw and sublaminar wire placement were documented and changes were appropriately classified.

RESULTS

Extensive anatomical changes were noted. These changes were more severe at the apex and independent of the curve severity. Both laminae were normal in only 36 (Type 1), rest had either gross asymmetry in length and shape (Type 2; 21) or also in sloping (Type 3; 13). Of the 140 pedicles, normal pedicles were found only in 48 (Type 1); while they were divergent (Type 2; 4) or abnormally elongated with only thinning (Type 3a; 26); or with sclerosis (3b; 34); or very curved and wavy (3c; 23) and even fractured or indistinct (Type 4; 5). It was notable that 92 of the 140 pedicles were unsuitable for pedicle screws. A unique phenomenon of body drift was identified in 29 segments which could jeopardize screw placement and rib dislocation into the canal was found in 18 segments.

CONCLUSION

Gross anatomical changes jeopardizing both sublaminar wire strength and trajectory of pedicle screws were common in NF and independent of curve severity. Therefore, detailed preoperative assessment and planning by a 3D CT are essential.

Combined Anterior-Posterior Versus Posterior-only Spinal Fusion in Treating Dystrophic Neurofibromatosis Scoliosis With Modern Instrumentation: A Systematic Review and Meta-analysis

STUDY DESIGN

This is a systematic review and meta-analysis study.

OBJECTIVES

To compare the efficacy, long-term stability, and safety of combined anterior-posterior spinal fusion (APSF) with posterior-only spinal fusion (PSF) in treating dystrophic neurofibromatosis scoliosis with the use of modern instrumentation.

SUMMARY OF BACKGROUND DATA

When the Harrington or Luque technique was used, APSF had relatively reliable results and had been recommended by many authors. But with the development of instrumentation and techniques, many surgeons performed PSF with satisfactory results. No systematic review and meta-analysis have been conducted to compare the outcomes of the 2 approaches.

MATERIALS AND METHODS

Relevant studies on anterior-posterior or posterior fusion of dystrophic neurofibromatosis scoliosis were retrieved from the PubMed, Embase, Cochrane, Springer Link, and Google Scholar databases. Then studies were manually selected for inclusion based on predefined criteria. Data extraction and quality assessment were conducted, and a systematic review and meta-analysis were performed.

RESULTS

Sixteen eligible studies were included. The angles of scoliosis curves and kyphosis curves were significantly and similarly corrected after surgery in both APSF and PSF group, respectively. At the last follow-up, the loss of correction was significant in the coronal plane but not in the sagittal plane with a similar progression of scoliosis in 2 groups. The overall complication rate was slightly higher in the APSF group, but the difference was not statistically significant. Meanwhile, there was no visible difference in the incidence of pseudarthrosis and instrumentation failures between the 2 groups.

CONCLUSIONS

APSF and PSF by means of the third-generation spinal instrumentation system have similar efficacy, long-term stability, and safety for treating dystrophic scoliosis secondary to type-1 neurofibromatosis.

LEVEL OF EVIDENCE

Level III-systematic review and meta-analysis study.

Influence of implant density and flexibility index on curve correction after scoliosis surgery

BACKGROUND

Numerous studies proved that all pedicle screw constructs produce the best outcome in the surgical treatment of patients with scoliosis. However, the optimal amount and distribution of screws has not yet been defined. In recent studies on idiopathic scoliosis, the correlation between curve correction and implant density has been discussed with diversifying results.

PURPOSE

The aim of this study was to detect a possible correlation of sagittal and coronal curve correction in dependence of metal load and flexibility index.

MATERIALS AND METHODS

Twenty-six patients were included in this study with surgical correction by one surgeon between January 2014 and December 2017. Clinical data and radiographic images (preoperative, postoperative and one-year follow-up) were retrospectively analyzed and metal load, flexibility index, correction rate and correction index were consequently calculated. The Pearson correlation analysis was used for metal load-correction index and metal load-correction rate, correction of kyphosis-metal load and correction of lordosis-metal load. According to the mean metal load of 88%, patients were divided into two subgroups-a low-density group of 12 patients and a high-density group of 14 patients. Clinical and radiographic features were examined by an independent two-sided t-test.

RESULTS

Eight patients were male, 18 patients female. Ten suffered from neuromuscular and 16 from idiopathic scoliosis. Mean age was 17.1 years. Correction rate directly postoperative was 70.43%, at the follow-up 67.90%. Mean correction index directly postoperative was 3.40 and at the follow-up 3.23. Pearson correlation of metal load-correction index directly postoperative was - 0.188 and one year postoperative - 0.189. The correlation between metal load-correction rate immediately after the surgery was 0.324 and at the follow-up 0.285. Correlation for correction of kyphosis-metal load postoperative was - 0.120 and one year later - 0.178. Pearson coefficient of lordosis-metal load directly after the surgical intervention was - 0.214 and at the follow-up - 0.220. Dependency of flexibility index and correction rate showed a positive trend (Pearson flexibility-correction rate direct 0.616; flexibility index-correction rate follow-up 0.516). A statistically significant difference between the high- and the low-density group was detected in the correction rate directly postoperative (p = 0.047).

CONCLUSION

With an implant density over 70%, satisfactory surgical treatment can be achieved in idiopathic and neuromuscular scoliosis. No statistical significance between the high-density (88-100%) and the low-density (73-87%) group could be verified in curve correction, ICU stay and complications.

Intra-operative neurophysiological monitoring in patients with dystrophic neurofibromatosis type 1 scoliosis

OBJECTIVE

To analyse the intra-operative neurophysiological monitoring (IONM) data in patients with dystrophic neurofibromatosis type 1 (NF1) associated scoliosis, and to investigate the possible risk factors for failed IONM monitoring.

METHODS

Patients undergoing posterior spinal fusion from September 2015 to December 2019 were retrospectively reviewed. The latency (P37, N50) and amplitude of somatosensory evoked potentials (SEP) in bilateral lower extremities, latency and amplitude of motor evoked potentials (MEP) in bilateral lower extremities and unilateral upper extremity were recorded. The neurological status, curve pattern, Cobb angle of main curve, vertebral rotatory subluxation and dystrophic features at pre-operation were assessed for each patient. The failed IONM monitoring was defined as no reliable SEP or MEP waveforms of all monitored muscles.

RESULTS

A total of 92 patients (53 M, 39 F) with an average age of 14.1 ± 2.7 years were included. Failed IONM monitoring was identified in 17 patients with overall success rates being 87.0 and 94.6% for SEP and MEP. The average P37 latency, N50 latency, SEP amplitude and MEP latency showed no significant difference between concave and convex sides (p > 0.05 for all). The MEP amplitudes of lower extremities were lower on concave side than convex side (334.5 ± 291.9 µV VS 417.5 ± 380.5 µV, p = 0.030). Higher risk of failed IONM monitoring was found in patients with neurological deficit (p = 0.014) and more dystrophic features (p = 0.002) at pre-operation.

CONCLUSIONS

The overall success rates were 87.0% for SEP and 94.6% for MEP in patients with NF1-associated scoliosis. Neurological deficit and more dystrophic features at pre-operation indicated higher risk of failed IONM monitoring.

Surgical treatment of scoliosis in neurofibromatosis type I: A retrospective study on posterior-only correction with third-generation instrumentation

Background:

Scoliosis is the most common orthopedic complication of neurofibromatosis type I. Scoliosis can be occurred with two patterns: dystrophic or idiopathic-like. In adolescence, in consideration of bone dystrophy, osteopenia, and often associated hyperkyphosis, most of the authors recommend an anterior-posterior approach. According to other authors, modern instrumentations could be sufficient to sustain a solid posterior arthrodesis.

Materials and Methods:

Ten patients were diagnosed with scoliosis in neurofibromatosis type I aged between 8 and 25 years, Cobb angle of the thoracic curve >45°, and minimum follow-up (FU) of 1 year and treated with posterior-only approach with third-generation high-density instrumentations. Radiographic measurements were performed on the coronal and sagittal planes. Nonparametric tests (Friedman test and Wilcoxon test) were applied to evaluate the reducibility of the preoperative curve (T0), the postoperative surgical correction (T1), and its maintenance on FU.

Results:

Statistics showed results compared to those evaluated in the literature with a combined approach regarding surgical correction and its maintenance on FU. On T1, a median correction of 53.5% of the scoliotic curve and of 33.7% of the thoracic hyperkyphosis was observed. On FU, the correction was maintained. A global improvement in balance was appreciated. The curves, despite rigid, showed a relative reducibility to bending tests and traction. No significant complications occurred.

Conclusions:

The posterior-only approach produces a satisfactory correction of the dystrophic neurofibromatosis scoliosis if associated with the use of high-density third-generation instrumentations. We are confident in recommending posterior-only approach in dystrophic neurofibromatosis scoliosis with coronal curves till 110° and coexisting thoracic kyphosis till 80°

Comparison between surgical fusion and the growing-rod technique for early-onset neurofibromatosis type-1 dystrophic scoliosis

Background

Spinal deformities constitute one of the most common types of manifestations of neurofibromatosis type-1 (NF-1), which can lead to either dystrophic or non-dystrophic early-onset scoliosis (EOS). Surgical treatment for EOS with NF-1 is challenging, and the outcomes have rarely been reported. The anterior-posterior procedure is widely used, but posterior-only fusion is theoretically easier and safer to perform. Is it possible that a new surgery that accommodates growth is a better choice? A direct comparison between posterior fusion and growth-friendly surgery in terms of surgical outcomes has not yet been conducted in dystrophic EOS with NF-1 patients.

Methods

Baseline information was extracted from the NF-1 database at our institute with approval from the local ethics committee. All enrolled patients were diagnosed with NF-1. Clinical and radiographic data were recorded preoperatively, after the initial surgery, and at the final follow-up. Implant-related, alignment, neurological complication and unplanned revision surgery data were recorded. We compared the outcomes of these two groups in terms of curve correction, growth parameters, complications and unplanned revision surgeries.

Results

There were eight patients in the PF group and eight patients in the GR group, with a mean follow-up of 51.0 ± 17.5 months. The main curve size was similar (PF 67.38° ± 17.43° versus GR 75.1° ± 26.43°, P = 0.501), and there were no significant differences in the initial surgery correction rate or the rate of correction. However, the patients in the GR group exhibited more T1-S1 growth during the follow-up overall and per year than did those in the PF group. The operative time was significantly longer for the PF group than for the GR group (PF, 4.39 ± 1.38 vs. GR, 3.00 ± 0.42 h; p = 0.008). Significantly fewer segments were involved in the PF group (8.25 ± 3.20) than in the GR group (13.00 ± 1.60).

Conclusion

For the initial treatment of dystrophic EOS in patients with NF-1, the GR technique is possibly a more appropriate treatment than is the PF technique in terms of trunk growth. However, the repeated procedures required for GR may be a considerable disadvantage. More studies with direct measurement of pulmonary function must be conducted to determine the effect of GR on pulmonary development. More studies with larger sample sizes and longer follow-up periods are needed to fully assess the treatment strategies.

Posterior only instrumented fusion provides incomplete curve control for early-onset scoliosis in type 1 neurofibromatosis

Background

The mid-long term outcomes of posterior spinal fusion in pediatric neurofibromatosis type 1 (NF-1) patients are rarely reported, so does the effectiveness of itsorthopeidc maintenance function. This study aims to evaluate the mid-long term surgical outcomes of posterior only instrumented spinal fusion for early-onset scoliosis (EOS) in NF-1 patients.

Methods

A retrospective review was performed on a cohort of 10 NF-1 patients having EOS from 2008 to 2014 in our hospital, the age averaged at 7.8 years old when they underwent posterior only instrumented spinal fusion for their EOS. Both general clinical data and surgical specific data of the patients were collected and reviewed, and the dystrophic progression of EOS was evaluated during the follow-up.

Results

The average duration of follow-up was 54 months (24 to 88 months). All patients underwent posterior only instrumented spinal fusion at 1 stage. The primary curves of EOS were thoracic in 9 cases and 1 patient had lumbar scoliosis. Preoperative major curve was significantly corrected (from 66.1 to 31.1 degrees). However, the major curve deteriorated significantly to 40.1 degrees on average at the end of the follow-up. The T1-S1 distance increased 2.8 cm on average and kept increasing at a rate of 0.6 cm/year during the follow-up.

Conclusions

Posterior only fusion surgery was not a good option to treat the EOS in NF-1 patients despite the relatively short segments involvement in the disease. The maintenance of orthopedic effect after treatment was not satisfactory.

Correction of Scoliosis with Large Thoracic Curves in Marfan Syndrome: Does the High-Density Pedicle Screw Construct Contribute to Better Surgical Outcomes

Background

The aim of this study was to determine whether higher density screw constructs resulted in better surgical outcomes in patients with scoliosis secondary to Marfan syndrome (MF-S) with large thoracic curves (≥70°).

Material/Methods

There were 34 MF-S patients who met the inclusion criteria and were evaluated radiographically before surgery, 2 weeks after operation, and at the final follow-up. The mean screw density was taken as the boundary, and patients were categorized as either in the high density (HD) group or the low density (LD) group. Parameters measured included coronal Cobb angle, T5–T12 kyphosis (TK), and T12–S1 lordosis (LL). Additionally, the operation duration, estimated blood loss, screw accuracy, complication rate, and clinical outcomes were compared between the 2 groups.

Results

The mean screw density of all patients was 1.40±0.15 (range 1.13 to 1.67). Correction rate of the thoracic curve was closely related to the screw density at the concave side (r=0.783, P=0.007). Intergroup comparison showed a significantly higher correction rate of the thoracic coronal curve in HD group (56.59±4.80% versus 44.54±9.61%, P=0.036). At last follow-up, coronal correction loss of >5° occurred in 8 cases (47.1%) in the LD group and 3 cases (17.6%) in the HD group. Both groups demonstrated improvement in each domain of the SRS-22 questionnaire after surgery and no significant intergroup difference was found.

Conclusions

The high-density pedicle screw construct contributed to the significantly improved correction rate of thoracic curves in MF-S patients with large thoracic curves (≥70°). Additionally, increasing of pedicle screw number could help to enhance the structural stability and reduce the correction loss during the follow-up period.

Incidence and Risk Factors for Instrumentation-related Complications After Scoliosis Surgery in Pediatric Patients With NF-1

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To assess the incidence and risk factors of instrumentation-related complication (IRC) in pediatric patients surgically treated for neurofibromatosis type 1 (NF-1) dystrophic scoliosis.

SUMMARY OF BACKGROUND DATA

Surgical management including growing rods technique and early definitive fusion has been recommended to avoid progression of NF-1 scoliosis. However, no study has yet investigated the incidence and risk factors of IRC in these surgical interventions.

METHODS

Data of 59 pediatric NF-1 patients who had been surgically treated for dystrophic scoliosis were retrospectively reviewed. All of their clinical and radiographic data were collected. We evaluated potential risk factors, including age, sex, curve type, preoperative Cobb angle, kyphosis angle and spinal length, and surgical procedure. The univariate analysis and multivariate logistic regression analysis were performed to identify the risk factors associated with IRC.

RESULTS

Seventeen (28.8%) patients suffered 19 IRCs, including seven cases of curve progression, three cases of screw dislodgement, three cases of adding-on phenomenon, two cases of rod breakage, two cases of proximal junctional kyphosis, one case of cap loosing, and one case of pedicle cutting. The univariate logistic regression analysis revealed age<9, kyphosis≥50°, and growing-rod techniques the significant risk factors (P < 0.05). Binomial logistic regression analysis demonstrated two independent risk factors of IRC, including kyphosis≥50° (OR: 8.23; P = 0.025) and application of growing-rod technique (OR: 8.75; P = 0.032).

CONCLUSION

17/59 (28.8%) patients suffered IRCs and age less than 9 years, kyphosis more than 50° and application of growing-rod are three risk factors for IRC after surgical treatment of NF-1 dystrophic scoliosis. Identification of these risk factors aids in stratifying preoperative risk to reduce IRC incidence. In addition, the results could be used in counseling patients and their families during the consent process.

LEVEL OF EVIDENCE

3.