Orthopaedic manifestations of neurofibromatosis in children: an update

Multiparametric whole-body MRI of patients with neurofibromatosis type I: spectrum of imaging findings

Neurofibromatosis (NF) type I is a neuroectodermal and mesodermal dysplasia caused by a mutation of the neurofibromin tumor suppressor gene. Phenotypic features of NF1 vary, and patients develop benign peripheral nerve sheath tumors and malignant neoplasms, such as malignant peripheral nerve sheath tumor, malignant melanoma, and astrocytoma. Multiparametric whole-body MR imaging (WBMRI) plays a critical role in disease surveillance. Multiparametric MRI, typically used in prostate imaging, is a general term for a technique that includes multiple sequences, i.e. anatomic, diffusion, and Dixon-based pre- and post-contrast imaging. This article discusses the value of multiparametric WBMRI and illustrates the spectrum of whole-body lesions of NF1 in a single imaging setting. Examples of lesions include those in the skin (tumors and axillary freckling), soft tissues (benign and malignant peripheral nerve sheath tumors, visceral plexiform, and diffuse lesions), bone and joints (nutrient nerve lesions, non-ossifying fibromas, intra-articular neurofibroma, etc.), spine (acute-angled scoliosis, dural ectasia, intraspinal tumors, etc.), and brain/skull (optic nerve glioma, choroid plexus xanthogranuloma, sphenoid wing dysplasia, cerebral hamartomas, etc.). After reading this article, the reader will gain knowledge of the variety of lesions encountered with NF1 and their WBMRI appearances. Timely identification of such lesions can aid in accurate diagnosis and appropriate patient management.

Recent Developments in Surgical Treatment of Spinal Deformity in Pediatric Patients: Experience from a Single-Center Series of 42 Neurofibromatosis Type 1 Patients

BACKGROUND

The management of spinal deformities in patients with NF-1 is challenging. The study aimed to assess the outcomes of the surgical treatment of spine deformities in children with neurofibromatosis type 1 with our treatment approach.

METHODS

A retrospective single-center study on pediatric patients with spinal deformities associated with NF-1 who received surgical treatment between 2006 and 2024.

RESULTS

The study group comprised 42 patients with a mean age at surgery of 9.8 years. Twenty-five patients (60%) were treated by means of growth-preserving techniques and 17 patients (40%) by means of definitive fusion. Preoperative halo-gravity traction was used in 14 (33%) cases. In the group treated with a growth-preserving technique, a 54.1% mean curve correction was observed at the latest follow-up, and growth of the thoracic spine was maintained at a physiological rate; however, 25 unplanned revision surgeries (mostly due to mechanical complications) were necessary. In the group treated by definitive fusion, a 66% curve correction was achieved at initial surgery, which remained unchanged at latest follow-up, and revision surgery was performed in three cases for augmentation of the fusion mass. There was one neurological complication (2%). Another patient developed a deep wound infection (2%).

CONCLUSIONS

Good and sustainable surgical correction of spinal deformities can be achieved in pediatric patients with NF-1. Due to the bony dystrophic changes, surgical treatment is challenging and the complication rate is higher than in spinal deformities of other etiologies.

Visual Deficits and Diagnostic and Therapeutic Strategies for Neurofibromatosis Type 1: Bridging Science and Patient-Centered Care

Neurofibromatosis type 1 (NF1) is an inherited autosomal dominant disorder primarily affecting children and adolescents characterized by multisystemic clinical manifestations. Mutations in neurofibromin, the protein encoded by the Nf1 tumor suppressor gene, result in dysregulation of the RAS/MAPK pathway leading to uncontrolled cell growth and migration. Neurofibromin is highly expressed in several cell lineages including melanocytes, glial cells, neurons, and Schwann cells. Individuals with NF1 possess a genetic predisposition to central nervous system neoplasms, particularly gliomas affecting the visual pathway, known as optic pathway gliomas (OPGs). While OPGs are typically asymptomatic and benign, they can induce visual impairment in some patients. This review provides insight into the spectrum and visual outcomes of NF1, current diagnostic techniques and therapeutic interventions, and explores the influence of NF1-OPGS on visual abnormalities. We focus on recent advancements in preclinical animal models to elucidate the underlying mechanisms of NF1 pathology and therapies targeting NF1-OPGs. Overall, our review highlights the involvement of retinal ganglion cell dysfunction and degeneration in NF1 disease, and the need for further research to transform scientific laboratory discoveries to improved patient outcomes.

The role of scoliosis on the comorbidity and demographics of neurofibromatosis type 1 patients: A retrospective analysis of the National Inpatient Sample database

Neurofibromatosis type 1 (NF1) is the most common neurocutaneous syndrome in the United States, affecting every 1 in 3000 individuals. NF1 occurs due to non-functional mutations in the NF1 gene, which expresses neurofibromin, a protein involved in tumour suppression. As a result, NF1 typically presents with non-cancerous neoplasm masses called neurofibromas across the body. Out of all NF1 abnormalities, the most common skeletal abnormality seen in around 10%-30% of NF1 patients is scoliosis, an improver curvature of the spine. However, there is a lack of research on the effects of scoliosis on demographics and morbidities of NF1 patients. We performed a national analysis to investigate the complex relationship between NF1 and scoliosis on patients' demographics and comorbidities. We conducted a retrospective cross-sectional analysis of the 2017 US National Inpatient Sample database using univariable Chi-square analysis and multivariable binary logistic regression analysis to determine the interplay of NF1 and scoliosis on patients' demographics and comorbidities. Our query resulted in 4635 total NF1 patients, of which 475 (10.25%) had scoliosis and 4160 (89.75%) did not. Demographic analysis showed that NF1 patients with scoliosis were typically younger, female and white compared to NF1 patients without scoliosis. Comorbidity analysis showed that NF1 patients with scoliosis were more likely to develop malignant brain neoplasms, epilepsy, hydrocephalus, pigmentation disorders, hypothyroidism, diabetes with chronic complications and coagulopathy disorders. NF1 patients with scoliosis were less likely to develop congestive heart failure, pulmonary circulation disease, peripheral vascular disease, paralysis, chronic pulmonary disease, lymphoma and psychosis. NF1 patients with scoliosis were predominantly younger, female, white patients. The presence of scoliosis in NF1 patients increases the risks for certain brain neoplasms and disorders but serves a protective effect against some pulmonary and cardiac complications.

Outcomes and Safety of Traditional Growing Rod Technique in the Treatment of Early-onset Dystrophic Scoliosis Secondary to Type 1 Neurofibromatosis With Intraspinal Rib Head Dislocation in Children

PURPOSE

The purpose of this study was to investigate the outcomes and safety of traditional growing rod (TGR) in the treatment of early-onset dystrophic scoliosis secondary to type 1 neurofibromatosis (NF1-EOS) with intraspinal rib head dislocation (IRH) in children.

METHODS

From September 2006 to June 2020, 21 patients with NF1-EOS were treated with TGR. The patients comprised 13 boys and 8 girls with a mean age of 7.1±1.5 years. Two patients had IRH-induced nerve injury [American Spinal Injury Association (ASIA) grade D]. No neurological symptoms were found in the other patients. The intraspinal rib proportion, apical vertebral rotation, apical vertebral translation, coronal main thoracic curve, trunk shift, thoracic kyphosis, lumbar lordosis, sagittal balance, and T1-S1 height were measured before and after TGR implantation and at the last follow-up. Complications were also evaluated.

RESULTS

The mean follow-up time was 3.4±2.0 years. An average of 3.1 times (range: 1 to 8 times) lengthening procedures were performed in each patient. The intraspinal rib proportion was significantly lower postoperatively than preoperatively (22±11% vs. 33±18%, respectively; P <0.001), and no significant correction loss was found at the last follow-up (24±12%, P= 0.364). Compared with the measurements before TGR implantation, the major coronal curve and T1-S1 height after TGR implantation and at the last follow-up were significantly different ( P <0.05). Significant correction of apical vertebral translation, thoracic kyphosis, lumbar lordosis, and sagittal balance were noted after TGR implantation, and no significant correction loss was found at the last follow-up ( P >0.05). Ten complications occurred in 7 patients. Two patients with nerve injury recovered after the operation. No neurological complications were found during the follow-up.

CONCLUSIONS

TGR is a safe and effective therapy for NF1-EOS with IRH where there was no direct compression of the spinal cord, which was confirmed by preoperative magnetic resonance imaging. Through this procedure, IRH could be partly removed from the spinal canal.

LEVEL OF EVIDENCE

Level III.

How to select the lowest instrumented vertebra in NF-1 non-dystrophic scoliosis

PURPOSE

To investigate lowest instrumented vertebra (LIV) selection strategy for neurofibromatosis type 1 (NF-1) non-dystrophic scoliosis.

METHODS

Consecutive eligible subjects with NF-1 non-dystrophic scoliosis were included. All patients were followed up at least for 24 months. Enrolled patients with LIV in stable vertebra were divided into stable vertebra group (SV group), and the other patients with LIV above the stable vertebra were divided into above stable vertebra group (ASV group). Demographic data, operative data, preoperative and postoperative radiographic data, and clinical outcome were collected and analyzed.

RESULTS

There were 14 patients in SV group (ten males and four females, mean age 13.9 ± 4.1 years) and 14 patients in ASV group (nine males and five females, mean age 12.9 ± 3.5 years). The mean follow-up period was 31.7 ± 17.4 months for patients in SV group and 33.6 ± 17.4 months for patients in ASV group, respectively. No significant differences were found in demographic data between two groups. The coronal Cobb angle, C7-CSVL, AVT, LIVDA, LIV tilt and SRS-22 questionnaire outcome significantly improved at the final follow-up in both groups. However, significantly higher loss of correction rate and increasement of LIVDA were found in ASV group. Two patients (14.3%) in ASV group but none in SV group suffered adding-on phenomenon.

CONCLUSIONS

Although patients in both SV and ASV groups obtained improved therapeutic efficacy at final follow-up, the radiographic and clinical outcome seemed more likely to deteriorate in ASV group after surgery. The stable vertebra should be recommended as LIV for NF-1 non-dystrophic scoliosis.

Anterolateral Tibial Bowing and Congenital Pseudoarthrosis of the Tibia: Current Concept Review and Future Directions

PURPOSE OF REVIEW

Congenital pseudarthrosis of the tibia (CPT) is a rare condition closely associated with neurofibromatosis type I. Affected children are born with anterolateral bowing of the tibia which progresses to pathologic fracture, pseudarthrosis, and high risk of refracture even after initial union has been attained. There is currently no consensus on the classification of this disease or consensus on its treatment. The purpose of this review is to (1) review the clinical presentation, etiology, epidemiology, classification, and natural history of congenital pseudarthrosis of the tibia and (2) review the existing trends in treatment of congenital pseudarthrosis of the tibia and its associated complications.

RECENT FINDINGS

Current treatment protocols focus primarily on combining intramedullary fixation with external or internal fixation to achieve union rates between 74 and 100%. Intramedullary devices should be retained as long as possible to prevent refracture. Cross-union techniques, though technically difficult, have a reported union rate of 100% and no refractures at mid- to long-term follow-up. Vascularized fibular grafting and induced membrane technique can be successful, but at the cost of numerous surgical procedures. Growth modulation is a promising new approach to preventing fracture altogether, though further study with larger patient series is necessary. The primary consideration in treatment of CPT is expected union rate and refracture risk. Combined intramedullary and external or internal fixation, especially with cross-union techniques, show most promise. Perhaps most exciting is further research on preventing fracture through guided growth, which may reduce the morbidity of multiple surgical procedures which have been the mainstay of treatment for CPT thus far.

How to rectify the convex coronal imbalance in patients with unstable dystrophic scoliosis secondary to type I neurofibromatosis: experience from a case series

BACKGROUND

There was a paucity of valid information on how to rectify the convex coronal imbalance effectively in dystrophic scoliosis secondary to Type I neurofibromatosis (DS-NF1), while postoperative inadvertent aggravation of CCI occurred regularly resulting in poor patient satisfaction. We aimed to identify the risk factors for persistent postoperative CCI in DS-NF1, and to optimize the coronal rebalancing strategies based on the lessons learned from this rare case series.

METHODS

NF1-related scoliosis database was reviewed and those with significant CCI (> 3 cm) were identified, sorted and the outcomes of surgical coronal rebalance were analyzed to identify the factors being responsible for failure of CCI correction.

RESULTS

CCI with dystrophic thoracolumbar/lumbar apex was prone to remain uncorrected (7 failure cases in 11) when compared to those with thoracic apex (0 failure cases in 4) (63.6% vs. 0.0%, p = 0.077). Further comparison between those with and without post-op CCI showed a higher correction of main curve Cobb angle (65.9 ± 9.1% vs. 51.5 ± 37.3%, p = 0.040), more tilted instrumentation (10.3 ± 3.6° vs. 3.2 ± 3.1°, p = 0.001) and reverse tilt and translation of upper instrumented vertebra (UIV) to convex side (8.0 ± 2.3° vs. -3.4 ± 5.9°, p < 0.001; 35.4 ± 6.9 mm vs. 12.3 ± 13.1 mm, p = 0.001) in the uncorrected imbalanced group. Multiple linear regression analysis revealed that △UIV translation (pre- to post-operation) (β = 0.832; p = 0.030) was significantly correlated with the correction of CBD.

CONCLUSION

Thoracolumbar/lumbar CCI in dystrophic scoliosis was prone to suffer high risk of persistent post-op CCI. Satisfying coronal rebalance should avoid UIV tilt and translation to the convex side, tilted morphology of instrumentation and over correction maneuvers for main curve, the upper hemi-curve region in particular.

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.

Management of NF-1 dystrophic scoliosis associated with rib heads dislocation into the spinal canal in neurological intact patients: a systematic literature review

PURPOSE

The management of scoliosis and kyphoscoliosis in patients with Type 1 Neurofibromatosis (NF-1) among spinal surgeons is still challenging due to the severity of the deformity especially in dystrophic deformity types. This rapid and progressive condition is likely to be associated with dislocated rib heads into the spinal canal, hence representing a real dilemma on the decision making between its resection versus not resection during the corrective surgery, especially in patients with normal neurological status. The objective of this publication is to discuss the management options in this patient population through a literature review.

METHODS

A comprehensive systematic literature search was performed for relevant studies using PubMed, Web of Science, and Scopus databases. Previous publications depicting neurologically intact patients with NF-1 and rib dislocation into the canal were reviewed. Articles reporting individual cases or case series/cohorts with patient-discriminated findings were included.

RESULTS

The data collection retrieved a total of 55 neurologically intact patients with NF-1 dystrophic scoliosis and rib penetration into the canal who underwent spinal surgery. Among them, 37 patients underwent surgery without head rib resection and 18 patients with rib excision. No patient presented postoperative neurological deficit except for one case of late postoperative neurological deterioration reported in a patient within situ fusion in which the surgeons ignored the presence of previous spinal cord compression.

CONCLUSION

Corrective surgery for patients with NF-1 and rib penetration into the canal in neurologically intact patients can be safely performed without the resection of the dislocated rib heads without a higher risk of neurological compromise.

Surgical Treatment of the Intraspinal Rib Head Dislocation in Children With Dystrophic Scoliosis Secondary to Type 1 Neurofibromatosis

BACKGROUND

The purpose of this study was to explore the surgical treatment of intraspinal rib head dislocation (IRH) in children with dystrophic scoliosis secondary to type 1 neurofibromatosis (NF1-DS).

METHODS

From 2006 to 2019, 32 of 128 patients with NF1-DS were found to have IRH and enrolled in this study. There were 19 boys and 13 girls with an average age of 8.8±2.6 years. Patients were divided into 2 groups: group A (n=25) without IRH resection and group B (n=7) with IRH resection. The intraspinal rib proportion (IRP), apical vertebra rotation, apical vertebral translation, main thoracic curve Cobb angle, trunk shift and thoracic kyphosis, lumbar lordosis, and sagittal vertebral axis were measured before and after the operation. Spinal injury was graded based on the American Spinal Injury Association (ASIA) Impairment Scale.

RESULTS

The study group had a total of 42 IRH. The mean follow-up duration was 46.1±28.7 months. The preoperative IRP in both groups was similar (35.5±14.3% vs. 31.2±15.3%, P=0.522). The postoperative IRP was lower in group B (18.5±11.2% vs. 0%, P=0.002). The IRP in group A decreased from preoperative (31.2±15.3%) to postoperative (18.5±11.2%) (P<0.05). There was no significant difference in the apical vertebra rotation, apical vertebral translation, main thoracic curve Cobb angle, trunk shift, thoracic kyphosis, lumbar lordosis, and sagittal vertebral axis between the 2 groups before surgery and after surgery. Four patients with nerve injury caused by the IRH had full neurological recovery postoperatively. All patients were ASIA grade E at the last follow-up.

CONCLUSIONS

The surgical treatment of IRH in children with NF1-DS should be determined on the basis of the presence of preoperative neurological symptoms. This study supports the practice of correcting spinal deformities only in patients with mild or no spinal cord injury. If there are obvious neurological symptoms, IRH resection is necessary to relieve spinal cord compression to recover nerve function.

LEVEL OF EVIDENCE

Level III.

Development of tibia & fibula bone deficits in children with neurofibromatosis type I - A longitudinal case-control comparison

Neurofibromatosis type 1 (NF1) is associated with lower bone mass and increased risk of fracture. Children with NF1 display faltering growth from mid-childhood. However, to date tibia bone development in children with NF1 across childhood and the role of body size have not been explored. Therefore, we recruited 24 children with NF1 (12 girls, mean age 8.2 ± 1.1y) and 104 children without NF1 (52 girls, mean age 11 ± 1.7y). Tibia and fibula bone characteristics were assessed at 4% and 38% distal-proximal tibia length in all children at baseline using peripheral quantitative computed tomography (pQCT). Longitudinal scans were obtained in 21 children with NF1 (12 girls) over 3.4 ± 0.3y and 71 children without NF1 (34 girls) over 1.1 ± 0.1y, such that at follow-up mean age of both groups (NF1 10.9 ± 1.3y, controls 11.4 ± 1.4y) were similar. Effects of group (NF1/control) on bone outcomes as well as group-by-age interactions, indicating differences in rate of change in bone outcome bone outcomes were assessed via linear mixed effects models with adjustment for sex, age, pubertal status and in additional models with adjustment for height and weight Z-scores. Group (NF1/control)-by-age interactions indicated a slower rate of tibia and fibula bone mass accrual in children with NF1 at all measured sites. These associations were attenuated by 25-50% by adjustment for height and weight Z-scores. At the 4% site, deficits in bone mass at older ages were related to slower trabecular BMD accrual. At the 38% site, group-by-age interactions suggested that bone mass deficits resulted from poorer accrual of cortical CSA and to a lesser extent cortical BMD. Lower limb bone mass deficits evident in children with NF1 appear to be progressive and emerge in mid-childhood. In part, they are related to development of a similar pattern of deficits in longitudinal growth and body weight in NF1. Interventions promoting muscle development or physical activity may be partially effective in attenuating bone mass accrual deficits in this population.

Autophagy is involved in neurofibromatosis type I gene-modulated osteogenic differentiation in human bone mesenchymal stem cells

Neurofibromatosis type I (NF1) is an autosomal dominant genetic disease that is caused by mutations in the NF1 gene. Various studies have previously demonstrated that the mTOR complex 1 signaling pathway is essential for the NF1-modulated osteogenic differentiation of bone mesenchymal stem cells (BMSCs). Additionally, the mTOR signaling pathway plays a notable role in autophagy. The present study hypothesized that NF1 could modulate the osteogenic differentiation of BMSCs by regulating the autophagic activities of BMSCs. In the present study, human BMSCs were cultured in an osteogenic induction medium. The expression of the NF1 gene was either knocked down or overexpressed by transfection with a specific small interfering RNA (siRNA) targeting NF1 or the pcDNA3.0 NF1-overexpression plasmid, respectively. Autophagic activities of BMSCs (Beclin-1, P62, LC3B I, and LC3B II) were determined using western blotting, electron microscopy, acridine orange (AO) staining and autophagic flux/lysosomal detection by fluorescence microscopy. In addition, the autophagy activator rapamycin (RAPA) and inhibitor 3-methyladenine (3-MA) were used to investigate the effects of autophagy on NF1-modulated osteogenic differentiation in BMSCs. Inhibiting NF1 with siRNA significantly decreased the expression levels of autophagy markers Beclin-1 and LC3B-II, in addition to osteogenic differentiation markers osterix, runt-related transcription factor 2 and alkaline phosphatase. By contrast, overexpressing NF1 with pcDNA3.0 significantly increased their levels. Transmission electron microscopy, AO staining and autophagic flux/lysosomal detection assays revealed that the extent of autophagosome formation was significantly decreased in the NF1-siRNA group but significantly increased in the NF1-pcDNA3.0 group when compared with the NC-siRNA and pcDNA3.0 groups, respectively. In addition, the activity of the PI3K/AKT/mTOR pathway [phosphorylated (p)-PI3K, p-AKT, p-mTOR and p-p70S6 kinase] was significantly upregulated in the NF1-siRNA group compared with the NC-siRNA group, and significantly inhibited in the NF1-pcDNA3.0 group, compared with the pcDNA3.0 group. The knockdown effects of NF1-siRNA on the autophagy and osteogenic differentiation of BMSCs were reversed by the autophagy activator RAPA, while the overexpression effects of NF1-pcDNA3.0 on the autophagy and osteogenic differentiation of BMSCs were reversed by the autophagy inhibitor 3-MA. In conclusion, results from the present study suggest at the involvement of autophagy in the NF1-modulated osteogenic differentiation of BMSCs. Furthermore, NF1 may partially regulate the autophagic activity of BMSCs through the PI3K/AKT/mTOR signaling pathway.

Intra-articular hip neurofibromas in von Recklinghausen's disease

Neurofibromatosis is a genetic disorder with osteo-articular manifestations. The intra-articular location of neurofibroma is scarce.

Natural History of Scoliosis in Children with NF1: An Observation Study

(1) Background. Scoliosis is the most common musculoskeletal manifestation of Neurofibromatosis type 1 (NF1), and it might be dystrophic (D) or non-dystrophic (ND) depending on the presence of dysplastic changes of the spine. The aim of our study was to describe the characteristics and natural history of patients with NF1 and scoliosis. (2) Methods. We retrospectively reviewed records from patients with NF1 and scoliosis. Scoliosis was classified as D if at least two dystrophic changes were documented at imaging. (3) Results. Of the 438 patients reviewed, 43 fulfilled inclusion criteria; 17 were classified in D group and 26 in ND. The groups did not differ in age and localization of scoliosis curvature. Surgery was needed more often in D group, but the between-group difference was not significant. Male-to-female ratios of 3:1 and 4:1 were reported in surgically treated NF1 patients with ND and D scoliosis, respectively. (4) Conclusions. Our data suggests independently by the presence of dysplastic changes affecting the spine that males with NF1 are more often affected by scoliosis that requires surgery.

Neurofibromatosis Type 1 with Severe Dystrophic Kyphosis: Surgical Treatment and Prognostic Analysis of 27 Patients

OBJECTIVE

The aim of the present study was to explore the surgical treatment and prognosis of 27 cases of neurofibromatosis type 1 with severe dystrophic kyphosis.

METHODS

We performed surgical treatment for scoliosis and kyphosis caused by dystrophic curves at Peking Union Medical College Hospital, Beijing, China from December 2015 to December 2017. The study included 21 patients with moderate to severe kyphosis, 12 males and 9 females, with an average age of 14.95 ± 6.05 years. All patients had kyphosis angles greater than 70° and had more than four skeletal developmental defects. A total of 6 patients with severe kyphosis, 2 males and 4 females, with an average age of 12.5 years, had more than five skeletal developmental defects with a kyphosis angle greater than 90° or a lumbar kyphosis angle greater than 40°. According to the patient's own situation, we adopted a low-grade surgery scheme (grades 1 or 2) or a high-grade surgery scheme (grades 3-6). The low-grade surgery was mainly lower articular surface resection or pontodestomy, and the high-grade surgery was mainly apical vertebral body or upper discectomy. All patients were followed up to determine their prognosis.

RESULTS

Statistical analysis showed that there was a significant difference in preoperative and postoperative scores between the two groups (P < 0.05), and scoliosis correction showed that surgical treatment had a significant effect on scoliosis kyphosis. The mean follow-up time was 66.7 months. Follow-up results showed that 50% of complications after internal fixation were related to high-level surgery. Complications included displacement of the titanium cage, removal of the lamina hook, formation of pseudoarthrosis, and internal fixation failure (with a rate of 7.7%-14.3%). In contrast, there were no associated symptoms for low-grade surgery. In addition, the results showed that gender, age, extent of resection, height, and body mass index had no significant effect on preoperative, postoperative, and prognostic indicators of patients (P > 0.05).

CONCLUSION

Early identification of dysplastic scoliosis-related deformities plays an important role in surgical planning and prognosis, and low-level surgical procedures are more favorable for patients' prognosis.

Neurofibromatosis -1 diagnosed from an intraoral swelling - a case series

The neurofibromatoses [NF 1, NF 2 and schwannomatosis] are a group of genetic disorders that lead to the development of nervous system tumours and have diverse dermatologic, neurologic, ophthalmic, skeletal and vascular effects. The most common is NF 1 (Neurofibromatosis 1) also known as von Recklinghausen's disease, which is one of the most common human genetic diseases. Oral manifestations of NF 1 are reported in 72% of cases and in one of our cases precipitated attendance at a general dental practitioner (GDP), subsequent diagnosis and genetic screening for family members. This disease may go undiagnosed due to its variable expressivity of symptoms. The pivotal importance of a GDP in the discovery and early referral to an oral or oral and maxillofacial surgeon for further investigation and diagnosis of this condition is highlighted. Knowledge of the most common features of neurofibromatosis can facilitate the speedy referral and subsequent diagnosis of generalized neurofibromatosis, local surgical management of benign neoplasms and long term management of its other clinical features. Dentists should be aware of the classic symptoms of this condition and of their role in long-term care in view of the risk of local recurrence and malignant transformation.

Understanding the Biological Activities of Vitamin D in Type 1 Neurofibromatosis: New Insights into Disease Pathogenesis and Therapeutic Design

Vitamin D is a fat-soluble steroid hormone playing a pivotal role in calcium and phosphate homeostasis as well as in bone health. Vitamin D levels are not exclusively dependent on food intake. Indeed, the endogenous production-occurring in the skin and dependent on sun exposure-contributes to the majority amount of vitamin D present in the body. Since vitamin D receptors (VDRs) are ubiquitous and drive the expression of hundreds of genes, the interest in vitamin D has tremendously grown and its role in different diseases has been extensively studied. Several investigations indicated that vitamin D action extends far beyond bone health and calcium metabolism, showing broad effects on a variety of critical illnesses, including cancer, infections, cardiovascular and autoimmune diseases. Epidemiological studies indicated that low circulating vitamin D levels inversely correlate with cutaneous manifestations and bone abnormalities, clinical hallmarks of neurofibromatosis type 1 (NF1). NF1 is an autosomal dominant tumour predisposition syndrome causing significant pain and morbidity, for which limited treatment options are available. In this context, vitamin D or its analogues have been used to treat both skin and bone lesions in NF1 patients, alone or combined with other therapeutic agents. Here we provide an overview of vitamin D, its characteristic nutritional properties relevant for health benefits and its role in NF1 disorder. We focus on preclinical and clinical studies that demonstrated the clinical correlation between vitamin D status and NF1 disease, thus providing important insights into disease pathogenesis and new opportunities for targeted therapy.

Congenital Forearm Pseudarthrosis, a Systematic Review for a Treatment Algorithm on a Rare Condition

BACKGROUND

A congenital forearm pseudarthrosis is a rare condition and is strongly associated with neurofibromatosis type 1. Several surgical techniques are described in the literature, but the most optimal treatment strategy remains unclear. This systematic review aims to develop a treatment algorithm that may aid in clinical decision making.

METHODS

The PROSPERO registration number for this study was CRD42018099602 and adheres to the PRISMA guidelines for systematic reviews. Embase, MEDLINE, Cochrane Central, Web of Science, and Google Scholar databases were searched for published studies reporting on congenital forearm pseudarthrosis not related to other underlying pathologies like bacterial infection or fibrous dysplasia. Results were not restricted by date or study type, only English literature was allowed. Studies were assessed for quality using the critical appraisal checklist for case reports from the Joanna Briggs Institute. Patient characteristics, underlying disease, type of surgery, union rate, and functional outcome were extracted from included studies.

RESULTS

Of 829 studies identified, 47 were included in this review (17 case series and 30 case reports, a total of 84 cases). A one-bone forearm procedure showed highest union rates (92%), however, it results in loss of forearm rotation. Free vascularized fibula grafting showed high union rates (87%) and was related to good functional outcome of elbow flexion and forearm rotations. Other procedures showed disappointing outcomes.

CONCLUSIONS

Congenital forearm pseudarthrosis is best treated with a free vascularized fibula grafting, a one-bone forearm procedure should be used as a salvage procedure. Evidence extracted from the case reports was sufficient to generate a treatment algorithm to be used in clinical pediatric practice.

LEVEL OF EVIDENCE

Level IV-therapeutic.

Neurofibromatosis type 1: New developments in genetics and treatment

Neurofibromatosis type 1 is the most common neurocutaneous syndrome, with a frequency of 1 in 2500 persons. Diagnosis is paramount in the pretumor stage to provide proper anticipatory guidance for a number of neoplasms, both benign and malignant. Loss-of-function mutations in the NF1 gene result in truncated and nonfunctional production of neurofibromin, a tumor suppressor protein involved in downregulating the RAS signaling pathway. New therapeutic and preventive options include tyrosine kinase inhibitors, mTOR inhibitors, interferons, and radiofrequency therapy. This review summarizes recent updates in genetics, mutation analysis assays, and treatment options targeting aberrant genetic pathways. We also propose modified diagnostic criteria and provide an algorithm for surveillance of patients with neurofibromatosis type 1.

Does neurofibromatosis 1 status impact outcomes for pediatric/young adults undergoing spinal fusion?

Background:

Although spinal deformities are common in patients with neurofibromatosis type 1 (NF1), there is a paucity of data as to how this impacts outcomes of spinal fusion surgery in pediatric/young adult patients.

Methods:

Using the Nationwide Inpatient Sample (2005–2014) for all patients undergoing spinal fusion ≤26 years of age, we compared the following factors: demographics, comorbidities, and perioperative variables (e.g., between NF1 vs. non-NF1, and between NF1 and propensity score (PS)-matched non- NF1 spinal fusion patients) using univariate hypothesis tests and multivariate regression analyses. Our main interest focused on length of stay, complication rates, adverse postoperative events, and incidence of nonroutine discharges.

Results:

In this study, 238 (0.92%) NF1 spine patients were compared to 25,558 (99.08%) non-NF1 spine patients. NF1 fusion patients were younger, included fewer females, and were more likely to be on Medicaid. Perioperatively, NF1 patients underwent more anterior approaches, had more vertebrae fused, required more transfusions, had a longer length of stay (LOS), and were less likely to be discharged home. However, after PS- matching, all differences between NF1 and non-NF1 groups disappeared were similar (P > 0.05). In PS-matched multivariate analyses, NF1-status was not a significant independent predictor of length of stay or nonroutine discharge disposition.

Conclusion:

NF1-status was, therefore, not an independent predictor of complications, adverse postoperative events, longer LOS, or nonroutine hospital discharge in this cohort analysis. Further prospective studies are necessary to understand how outcomes in patients with NF1 compare to non-NF1 pediatric and young adult patients.

Grade V Thoracic Spondylolisthesis in Neurofibromatosis Type 1: Case Report and Literature Review

BACKGROUND

Grade V thoracic spondylolisthesis secondary to neurofibromatosis type 1 (NF-1), especially combined with vertebral fusion, is rare. We reported a case of a 26-year-old female diagnosed with grade V T2spondylolisthesis and T2-T5 autofusion secondary to NF-1, which caused severe kyphotic deformity and neurologic deficits, and she was treated with posterior decompression, internal fixation, and fusion.

CASE DESCRIPTION

The right-handed patient admitted to the clinic due to weakness of her legs. An eye examination documented a sign of Lisch nodules in the iris. Café-au-lait macules, dermal neurofibroma of multiple forms, and rubbery bumps of varying sizes could be observed on her skin. Paresis with muscle strength of 2/5 in both lower extremities with increased muscle tone and decreased muscle mass could be observed. Radiographic results indicated grade V thoracic spondylolisthesis with vertebral fusion from T2-T5 level. To alleviate neurologic dysfunction, posterior decompression, internal fixation, and fusion were performed. She reported marked improvement in lower limb motor and sensory functions during the follow-up, and her muscle strength recovered to 5/5.

CONCLUSIONS

Grade V thoracic spondylolisthesis combined with vertebral fusion on T2-T5 level in NF-1 is rare. Early surgical intervention of posterior spinal decompression with internal fixation and fusion yielded satisfactory clinical outcomes.

Unusual form of the distal bone defect of ulna with neurofibromatosis type 1: A case report

RATIONALE

Bone malformation occurs in 10% to 25% neurofibromatosis type 1 (NF-1) patients, and the manifestations are scoliosis, congenital arch and pseudo-joint formation, bone cyst, and pathologic fracture. However, a large segmental defect without obvious signs of bone destruction has rarely been reported.

PATIENT CONCERNS

A 4.5-year-old male presented with a 4-year history of shortening of the right upper limb and radial head dislocation. The X-ray indicated a lack of the distal part of the right ulna and radial head dislocation.

DIAGNOSIS

The X-ray showed obvious bone resorption at the right ulna distal, proximal stubble, and distal part of the epiphyseal residue, which was 4.3 mm shorter after 14 months. The patient was finally diagnosed with NF-1 according to the pathologic examination.

INTERVENTIONS

The treatment included tumor resection, ulnar osteotomy, and fixation by an Ilizarov frame.

OUTCOMES

The Ilizarov frame was removed after 2.7 months of surgery. The radial head was successfully repositioned, and the elbow joint function was significantly improved. No recurrence of the deformity was noted until now.

LESSONS

Osteolysis (defect without bone destruction) is an extremely rare symptom in patients with NF1. Therefore, it is essential to make the right diagnosis by comprehensive and careful physical examination.

Identification and characterization of NF1 and non-NF1 congenital pseudarthrosis of the tibia based on germline NF1 variants: genetic and clinical analysis of 75 patients

Background

Congenital pseudarthrosis of the tibia (CPT) is a rare disease. Some patients present neurofibromatosis type 1 (NF1), while some others do not manifest NF1 (non-NF1). The etiology of CPT, particularly non-NF1 CPT, is not well understood. Here we screened germline variants of 75 CPT cases, including 55 NF1 and 20 non-NF1. Clinical data were classified and analyzed based on NF1 gene variations to investigate the genotype-phenotype relations of the two types of patients.

Results

Using whole-exome sequencing and Multiplex Ligation-Dependent Probe Amplification, 44 out of 55 NF1 CPT patients (80.0%) were identified as carrying pathogenic variants of the NF1 gene. Twenty-five variants were novel; 53.5% of variants were de novo, and a higher proportion of their carriers presented bone fractures compared to inherited variant carriers. No NF1 pathogenic variants were found in all 20 non-NF1 patients. Clinical features comparing NF1 CPT to non-NF1 CPT did not show significant differences in bowing or fracture onset, lateralization, tissue pathogenical results, abnormality of the proximal tibial epiphysis, and follow-up tibial union after surgery. A considerably higher proportion of non-NF1 patients have cystic lesion (Crawford type III) and used braces after surgery.

Conclusions

We analyzed a large cohort of non-NF1 and NF1 CPT patients and provided a new perspective for genotype-phenotype features related to germline NF1 variants. Non-NF1 CPT in general had similar clinical features of the tibia as NF1 CPT. Germline NF1 pathogenic variants could differentiate NF1 from non-NF1 CPT but could not explain the CPT heterogeneity of NF1 patients. Our results suggested that non-NF1 CPT was probably not caused by germline NF1 pathogenic variants. In addition to NF1, other genetic variants could also contribute to CPT pathogenesis. Our findings would facilitate the interpretation of NF1 pathogenic variants in CPT genetic counseling.

Supplementary information

The online version of this article (10.1186/s13023-019-1196-0) contains supplementary material, which is available to authorized users.

Early and Midterm Outcomes of Surgical Correction for Severe Dystrophic Cervical Kyphosis in Patients with Neurofibromatosis Type 1: A Retrospective Multicenter Study

OBJECTIVE

To evaluate the early and midterm outcomes of surgical correction for severe dystrophic cervical kyphosis in patients with neurofibromatosis type 1 (NF-1) and analyze the pathomechanics and the influence on surgical efficacy of related systemic skeletal dystrophy.

METHODS

Ten patients who underwent surgical correction for NF-1-related severe dystrophic cervical kyphosis were reviewed. Radiographic parameters, including local and global Cobb angle, sagittal vertical axis, and T-1 slope, were measured. The visual analog scale score, Japanese Orthopaedic Association score, Neck Disability Index, Patient Satisfaction Index, and complications were evaluated.

RESULTS

The average follow-up was 50.6 months. The local and global Cobb angle improved from the preoperative average of 82.0° and 54.9° to an average of 35.6° and 29.8°, respectively, at the time of final follow-up. The C2-7 sagittal vertical axis averaged 5.8 mm before surgery and 8.9 mm at the final follow-up. The average T1 slope was -12.3° before surgery and -1.6° at the final follow-up. The visual analog scale score, Japanese Orthopaedic Association score, and Neck Disability Index improved significantly, and the overall satisfaction rate was 90.0%. One death and 4 instrumentation failures occurred, 3 patients showed progression of the kyphosis, and 2 fusion failures were observed.

CONCLUSIONS

Surgical correction, specifically the combined anteroposterior procedure, is essential and effective for management of NF-1-related severe dystrophic cervical kyphosis. However, high incidences of instrumentation failure, kyphosis progression, and fusion failure were observed. NF-1-related continuous skeletal dystrophy caused by multiple metabolic factors remarkably affected the midterm outcomes. Early prevention and targeted pharmacotherapy may be necessary.

Rotatory Dislocation of the Spine in Dystrophic Kyphoscoliosis Secondary to Neurofibromatosis Type 1

Aim of the study

Neurofibromatosis type 1 (NF-1) is associated with the development of scoliosis or kyphoscoliosis. The deformity is rapidly progressive in the presence of dystrophic changes producing bone erosion. Vertebral subluxation or dislocation can occur in children with highly dystrophic kyphoscoliosis and carries an increased risk of paralysis. There is no standardised treatment for this extreme deformity with very few patients currently reported in the literature.

Methods

Retrospective review of a patient with NF-1 who developed a dystrophic upper thoracic kyphoscoliosis with segmental displacement of T2 on T3.

Results

We report a patient with NF-1 who presented at 8.9 years with a progressive upper thoracic kyphoscoliosis. At 18.8 years, the deformity had deteriorated to scoliosis 65° and kyphosis 78° with fixed segmental rotatory dislocation at T2-T3. He underwent posterior cervico-thoracic fusion with concave pedicle screw/hook/rod instrumentation and iliac crest bone. Minimum correction was achieved due to curve rigidity and inability to reduce the T2/T3 displacement by halo-femoral traction. At 7 months, an elective posterior re-grafting procedure was performed followed by anterior fusion with rib strut grafts between T2-T6 through a midline sternotomy. The patient is now 3.5 years after anterior surgery and remains neurologically intact with stable residual deformity and computed tomographic evidence of circumferential fusion. He has no back pain and resumed non-contact physical activities.

Conclusions

Patients with NF-1 can develop dystrophic kyphoscoliosis with segmental spinal subluxation/dislocation. Circumferential fusion is a technically challenging procedure which often requires a multi-disciplinary surgical team but produces satisfactory clinical outcome preventing paraplegia.

Improved union and bone strength in a mouse model of NF1 pseudarthrosis treated with recombinant human bone morphogenetic protein-2 and zoledronic acid

Tibial pseudarthrosis associated with Neurofibromatosis type 1 (NF1) is an orthopedic condition with consistently poor clinical outcomes. Using a murine model that features localized double inactivation of the Nf1 gene in an experimental tibial fracture, we tested the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) and/or the bisphosphonate zoledronic acid (ZA). Tibiae were harvested at 3 weeks for analysis, at which time there was negligible healing in un-treated control fractures (7% union). In contrast, rhBMP-2 and rhBMP-2/ZA groups showed significantly greater union (87% and 93%, p < 0.01 for both). Treatment with rhBMP-2 led to a 12-fold increase in callus bone volume and this was further increased in the rhBMP-2/ZA group. Mechanical testing of the healed rhBMP-2 and rhBMP-2/ZA fractures showed that the latter group had significantly higher mechanical strength and was restored to that of the un-fractured contralateral leg. Co-treatment with rhBMP-2/ZA also reduced fibrous tissue infiltration at the fracture site compared to rhBMP alone (p = 0.068). These data support the future clinical investigation of this combination of anabolic and anti-resorptive agents for the treatment of NF1 pseudarthrosis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:930-936, 2018.

The reduced osteogenic potential of Nf1-deficient osteoprogenitors is EGFR-independent

Neurofibromatosis type 1 (NF1) is a common genetic disorder caused by mutations in the NF1 gene. Recalcitrant bone healing following fracture (i.e. pseudarthrosis) is one of the most problematic skeletal complications associated with NF1. The etiology of this condition is still unclear; thus, pharmacological options for clinical management are limited. Multiple studies have shown the reduced osteogenic potential of Nf1-deficient osteoprogenitors. A recent transcriptome profiling investigation revealed that EREG and EGFR, encoding epiregulin and its receptor Epidermal Growth Factor Receptor 1, respectively, were among the top over-expressed genes in cells of the NF1 pseudarthrosis site. Because EGFR stimulation is known to inhibit osteogenic differentiation, we hypothesized that increased EREG and EGFR expression in NF1-deficient skeletal progenitors may contribute to their reduced osteogenic differentiation potential. In this study, we first confirmed via single-cell mRNA sequencing that EREG over-expression was associated with NF1 second hit somatic mutations in human bone cells, whereas Transforming Growth Factor beta 1 (TGFβ1) expression was unchanged. Second, using ex-vivo recombined Nf1-deficient mouse bone marrow stromal cells (mBMSCs), we show that this molecular signature is conserved between mice and humans, and that epiregulin generated by these cells is overexpressed and active, whereas soluble TGFβ1 expression and activity are not affected. However, blocking either epiregulin function or EGFR signaling by EGFR1 or pan EGFR inhibition (using AG-1478 and Poziotinib respectively) did not correct the differentiation defect of Nf1-deficient mBMSCs, as measured by the expression of Alpl, Ibsp and alkaline phosphatase activity. These results suggest that clinically available drugs aimed at inhibiting EGFR signaling are unlikely to have a significant benefit for the management of bone non-union in children with NF1 PA.

Does spinal deformity correction of non-dystrophic scoliosis in neurofibromatosis type I with one-stage posterior pedicle screw technique produce outcomes similar to adolescent idiopathic scoliosis?

BACKGROUND CONTEXT

The efficacy of one-stage posterior pedicle screw instrument used in the treatment of non-dystrophic scoliosis in neurofibromatosis type I (NF-1) is unknown. Also, there is no study that has directly compared the results of spinal deformity correction between non-dystrophic scoliosis in NF-1 and adolescent idiopathic scoliosis (AIS).

PURPOSE

The objectives of this study were to study the efficacy of a one-stage posterior pedicle screw instrument used in the treatment of non-dystrophic scoliosis in NF-1 and to compare non-dystrophic scoliosis in NF-1 with matched AIS to illustrate the differences.

STUDY DESIGN

This is a retrospective case control study.

PATIENT SAMPLE

Fifteen patients with non-dystrophic scoliosis in NF-1 and 15 patients with AIS underwent a one-stage posterior surgery with the pedicle screw system.

OUTCOME MEASURES

Preoperative and postoperative whole-spine radiographs were used to determine coronal and sagittal Cobb angles. Also, the distance between the C7 plumb line and the center sacral vertical line and the sagittal vertebral axis was measured to assess spinal balance. The Scoliosis Research Society (SRS)-22 questionnaire was used to evaluate functional outcomes.

METHODS

We matched 15 patients with non-dystrophic scoliosis in NF-1 with patients with AIS (ratio, 1:1) for age, sex, and degree of major deformity. The overall mean age was 13.4±2.0 and 14.0±2.1 years, respectively. The NF-1 group consisted of 10 boys and 5 girls, and the AIS group consisted of 9 boys and 6 girls. The mean follow-up was 37.6±3.9 and 33.5±5.0 months, respectively. The AIS group underwent end vertebra (EV) or EV+1 fusion. The NF-1 group underwent EV+1, 2, or 3 fusion. Both coronal and sagittal Cobb angles, trunk balance, operative time, blood loss, fusion levels, length of stay, and scores on the SRS-22 questionnaire were compared between the two groups. The study was supported by the National Natural Science Foundation of China (Grant No. 81401760). There were no study-specific conflict of interest-associated biases.

RESULTS

The preoperative main curve magnitude was similar between the two groups; however, the flexibility of the NF-1 group tended to be less than that of the AIS group. The rate of correction of the main curve obtained surgically (79.8% compared with 81.1%) was similar in the NF-1 and AIS groups. There were no significant differences in the loss of correction between the two groups (p>.05). Also, there were no significant differences between the groups in operative time, blood loss, fusion levels, screw number, length of stay, trunk balance, and scores on the SRS-22. There were no serious complications related to surgery in both groups.

CONCLUSIONS

Despite the differences in preoperative flexibilities and fusion strategies, non-dystrophic scoliosis in NF-1 can be treated with a satisfied correction rate and progression rate similar to comparable AIS by using the one-stage posterior pedicle screw technique. Dural ectasia or thin pedicles in non-dystrophic scoliosis could make pedicle screw placement challenging.

Pedicle screw versus hybrid posterior instrumentation for dystrophic neurofibromatosis scoliosis

Surgical management of severe rigid dystrophic neurofibromatosis (NF) scoliosis is technically demanding and produces varying results. In the current study, we reviewed 9 patients who were treated with combined anterior and posterior fusion using different types of instrumentation (i.e., pedicle screw, hybrid, and all-hook constructs) at our institute.Between September 2001 and July 2010 at our institute, 9 patients received anterior release/fusion and posterior fusion with different types of instrumentation, including a pedicle screw construct (n = 5), a hybrid construct (n = 3), and an all-hook construct (n = 1). We compared the pedicle screw group with the hybrid group to analyze differences in preoperative curve angle, immediate postoperative curve reduction, and latest follow-up curve angle.The mean follow-up period was 9.5 ± 2.9 years. The average age at surgery was 10.3 ± 3.9 years. The average preoperative scoliosis curve was 61.3 ± 13.8°, and the average preoperative kyphosis curve was 39.8 ± 19.7°. The average postoperative scoliosis and kyphosis curves were 29.7 ± 10.7° and 21.0 ± 13.5°, respectively. The most recent follow-up scoliosis and kyphosis curves were 43.4 ± 17.3° and 29.4 ± 18.9°, respectively. There was no significant difference in the correction angle (either coronal or sagittal), and there was no significant difference in the loss of sagittal correction between the pedicle screw construct group and the hybrid construct group. However, the patients who received pedicle screw constructs had significantly less loss of coronal correction (P < .05). Two patients with posterior instrumentation, one with an all-hook construct and the other with a hybrid construct, required surgical revision because of progression of deformity.It is difficult to intraoperatively correct dystrophic deformity and to maintain this correction after surgery. Combined anterior release/fusion and posterior fusion using either a pedicle screw construct or a hybrid construct provide similar curve corrections both sagittally and coronally. After long-term follow-up, sagittal correction was maintained with both constructs. However, patients treated with posterior instrumentation using pedicle screw constructs had significantly less loss of coronal correction.

Bone mineral density and bone metabolic markers' status in children with neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is a multisystem disorder characterized by progressive manifestations, which is inherited in an autosomal dominant manner. The majority of patients with NF1 experience a diffuse, significant reduction in bone mass over time, with osteoporosis, osteopenia in the absence of severe scoliosis, or gross bone deformities. This study aimed to determine the bone mineral density (BMD) status, evaluate bone metabolism, and to determine the relevant factors in children with NF1.

METHODS

The study population included 33 pediatric NF1 patients (20 males and 13 females). Bone metabolic markers, such as total calcium, phosphorus, magnesium, alkaline phosphatase, parathyroid hormone, and 25-OH vitamin D, the urinary calcium/creatine ratio were measured. In addition, BMD was measured at both the lumbar spine (LS) and the femoral neck in all the patients.

RESULTS

All the patients had a low 25-OH vitamin D level, but it was significantly lower in the females than in the males (p<0.009). Overall, 18.2% of the patients had skeletal abnormalities. The lumbar Z-score was ≤2 in 21.2% of the patients, whereas the femoral neck Z-score was ≤2 in 9.1%. The urinary calcium/creatine ratio was significantly higher in the female than in the male patients (p<0.027). In all, six patients had skeletal abnormalities.

CONCLUSIONS

It is widely known that bone mineral metabolism markers and BMD are significantly affected in NF1 patients; however, the present study did not identify any effective parameters that could be used to predict skeletal abnormalities, or diagnose early osteoporosis and osteopenia in pediatric NF1 patients.

Thoracic compression myelopathy due to the progression of dystrophic scoliosis, the presence of a paraspinal tumor, and high and excessive amplitude movement of the shoulder

The authors present a case of 45-year-old man with neurofibromatosis type 1 (NF-1) and thoracic scoliosis, previously undergoing fusion surgery, who developed myelopathy. This patient further complained of lightning pain when he extended and horizontally abducted the convex-side shoulder. Radiological examination revealed the progression of dystrophic scoliosis with opened spinal canals and the presence of a neurofibroma behind the spinal cord at the apical levels. Delayed development of spinal instability can occur due to dystrophy even postoperatively in patients with NF-1. After tumor resection, he had rapid recovery from myelopathy and no recurrence of radiating pain despite shoulder movement. These findings provide a speculation that high, intense amplitude movement of the shoulder toward the spinal canal causes the impingement on the neurofibroma, resulting in indirect compression of the exposed spinal cord. This is the first report describing thoracic compression myelopathy associated with paraspinal displacement of the scapula.

Prevalence of neurofibromatosis type 1 in congenital pseudarthrosis of the tibia

A strong relationship between congenital pseudarthrosis of the tibia (CPT) and neurofibromatosis type 1 (NF1) has been suggested, but prevalence varies widely throughout the literature and the criteria used for diagnosis are very heterogeneous. Literature focus is mainly on treatment and no specific review on the prevalence of NF1 has been published. Based on our own observations, we hypothesized the prevalence of NF1 in patients with CPT to be higher than what is previously accepted. We conducted a comprehensive literature review on this topic and compared results with our study population. Twenty-one out of twenty-five patients in the study population matched the NIH diagnostic criteria for NF1 (84.0 %, CI95 = 69.6-98.4 %). These results are higher than the prevalence reported in the literature (55.4 %, CI95 = 50.4-60.4 %).

CONCLUSIONS

The prevalence of NF1 in patients with CPT might be higher than what is reported until now because the criteria of NF1 generally appear only after the diagnosis of CPT. We propose a repeat meticulous examination and a multidisciplinary approach with a clinical genetic counseling in all CPT patients.

WHAT IS KNOWN

• Congenital pseudarthrosis of the tibia and neurofibromatosis type 1 are closely related. • Literature focus is mainly on treatment and little epidemiologic research is available. What is New: • Prevalence of neurofibromatosis type 1 in patient with congenital pseudarthrosis of the tibia might be higher than what is reported until now. • A multidisciplinary approach with meticulous clinical examination and genetic counseling might lead to an earlier diagnosis of neurofibromatosis type 1 in patients with congenital pseudarthrosis of the tibia.

Hip dislocation following minor trauma in a patient with neurofibromatosis type 1: a case report and review of the literature

Neurofibromatosis type 1 (NF-1) is a common autosomal dominant disorder which is known to have associated skeletal manifestations. There are documented cases of hip dislocation in NF-1, although it is a rare occurrence. Previous cases have been associated with intra-articular neurofibromas, acetabular protrusio and femoral deformities such as coxa valga and in one case increased femoral offset.The authors review the literature on pelvic manifestations and report a case of hip dislocation in a 19-year-old woman with neurofibromatosis-one following minor trauma believed to be secondary to markedly increased femoral offset.This case illustrates the effect the NF-1 can have on the anatomy of the proximal femur and one of the complications that can present to the orthopaedic surgeon, without the presence on an intra-articular neurofibroma. In a review of the literature the authors found only two other cases of hip dislocation associated with NF-1 that occurred without the presence of an intra-articular neurofibroma.

Treatment of dystrophic scoliosis in neurofibromatosis Type 1 with one-stage posterior pedicle screw technique

BACKGROUND CONTEXT

Corrective surgery for dystrophic scoliosis in neurofibromatosis Type 1 (NF-1) is challenging. There are various surgical methods, all with unsatisfactory outcomes.

PURPOSE

The purpose of the study was to evaluate the clinical outcomes of the treatment of dystrophic scoliosis in NF-1 with one-stage posterior pedicle screw approach.

STUDY DESIGN

This is a retrospective clinical study.

PATIENT SAMPLE

Sixteen patients with dystrophic scoliosis in NF-1 underwent one-stage posterior surgery with pedicle screw system.

OUTCOME MEASUREMENT

We used preoperative and postoperative whole-spine radiographs to determine coronal and sagittal Cobb angles (curve correction); distance between apex vertebra and central sacral vertical line (DAC), pelvic obliquity, and shoulder tilt (coronal balance improvement); and sagittal vertical axis and pelvic tilt angle (sagittal balance improvement). We assessed the fusion rate using fusion segment computed tomography scan.

METHODS

Patients underwent surgery with or without osteotomy according to spinal flexibility. Fusion segment selection method of fusion segments selection which mean fusing from one or two levels proximal to upper end vertebra to one or two levels distal to the lower end vertebra (EV+1 or 2) or stable vertebrae fusion. There were no study-specific conflict of interest-associated biases.

RESULTS

The average follow-up time was 40.9 months. Mean scoliosis and kyphosis improved from 83.2° to 27.6° and 58.5° to 26.8°, respectively; at the last follow-up, it was 30.4° and 27.4°, respectively. Mean DAC, pelvic obliquity, and shoulder tilt improved from 53.0 to 23.9, 8.1 to 4.9, and 9.8 to 7.5 mm, respectively. Sagittal vertical axis and pelvic tilt angle improved from -5.8 to 1.6 mm and 17.9° to -5.8°, respectively. During follow-up, mean coronal and sagittal correction losses were 2.8° and 0.7°, respectively. Two EV+1 or 2 patients had decompensation. No pseudoarthrosis was identified.

CONCLUSIONS

The one-stage posterior pedicle screw approach is safe and effective in the treatment of dystrophic scoliosis in NF-1. Posterior vertebral column resection is recommended if flexibility is less than 35%. Stable vertebrae fusing is recommended.

Animal models of scoliosis

Multiple techniques designed to induce scoliotic deformity have been applied across many animal species. We have undertaken a review of the literature regarding experimental models of scoliosis in animals to discuss their utility in comprehending disease aetiology and treatment. Models of scoliosis in animals can be broadly divided into quadrupedal and bipedal experiments. Quadrupedal models, in the absence of axial gravitation force, depend upon development of a mechanical asymmetry along the spine to initiate a scoliotic deformity. Bipedal models more accurately mimic human posture and consequently are subject to similar forces due to gravity, which have been long appreciated to be a contributing factor to the development of scoliosis. Many effective models of scoliosis in smaller animals have not been successfully translated to primates and humans. Though these models may not clarify the aetiology of human scoliosis, by providing a reliable and reproducible deformity in the spine they are a useful means with which to test interventions designed to correct and prevent deformity.

Dystrophic spinal deformities in a neurofibromatosis type 1 murine model

Despite the high prevalence and significant morbidity of spinal anomalies in neurofibromatosis type 1 (NF1), the pathogenesis of these defects remains largely unknown. Here, we present two murine models: Nf1^flox/−;PeriCre and Nf1^flox/−;Col.2.3Cre mice, which recapitulate spinal deformities seen in the human disease. Dynamic histomorphometry and microtomographic studies show recalcitrant bone remodeling and distorted bone microarchitecture within the vertebral spine of Nf1^flox/−;PeriCre and Nf1^flox/−;Col2.3Cre mice, with analogous histological features present in a human patient with dystrophic scoliosis. Intriguingly, 36–60% of Nf1^flox/−;PeriCre and Nf1^flox/−;Col2.3Cre mice exhibit segmental vertebral fusion anomalies with boney obliteration of the intervertebral disc (IVD). While analogous findings have not yet been reported in the NF1 patient population, we herein present two case reports of IVD defects and interarticular vertebral fusion in patients with NF1. Collectively, these data provide novel insights regarding the pathophysiology of dystrophic spinal anomalies in NF1, and provide impetus for future radiographic analyses of larger patient cohorts to determine whether IVD and vertebral fusion defects may have been previously overlooked or underreported in the NF1 patient population.

Multidetector CT with 3-dimensional volume rendering in the evaluation of the spine in patients with Neurofibromatosis type 1: a retrospective review in 73 patients

INTRODUCTION

Neurofibromatosis type 1 (NF-1) may involve the spine as various abnormalities including bony dysplasia, scoliosis, and nerve sheath tumors. Surgery may be performed for stabilization of the spine. We have seen an increase in requests for multidetector CT (MDCT) imaging with the (three-dimensional) 3D-volume rendered (VR) images in patients evaluated at our institution. We, therefore, investigated how MDCT could be best utilized in this patient population.

METHODS

Seventy-three patients with NF-1 were identified in whom MDCT imaging was performed for diagnostic, pre-operative, or post-operative evaluation of spinal abnormalities. True axial source images and two dimensional (2D) orthogonal reconstructed MDCT images, as well as the VR images, were compared with plain radiographs and MRI. In addition, the MDCT study was compared to the VR images. These studies were reviewed to compare assessment of A) bony abnormalities such as remodeling from dural ectasia, dysplasia, and fusion, B) abnormal spinal curvature, C) nerve sheath tumors, and D) surgical instrumentation.

RESULTS

When compared to plain radiographs, the MDCT and VR images were rated as helpful for evaluating the abnormalities of the spine in 19 of 24 patients for a total of 30 findings. This included the following categories A) (n = 6), B) (n = 5), C) (n = 7), and D) (n = 12). Compared to MR, the MDCT and VR study was helpful in evaluating the findings of NF-1 in 24 of 36 patients for a total of 40 findings. This included the following categories A) (n = 12), B) (n = 10), C) (n = 3), and D) (n = 15). When the VR images were compared to the orthogonal MDCT, the VR images was rated as helpful in 41 of 73 patients for a total of 60 findings, including the following categories: A) (n = 11), B) (n = 24), C) (n = 0), and D) (n = 25).

CONCLUSION

MDCT has distinct advantages over plain radiographs and MR imaging, and the VR images over MDCT in the evaluation of the spine in patients with NF-1, especially for the assessment of bony abnormalities, abnormal spinal curvature, and spinal instrumentation.

A Combination of rhBMP-2 (Recombinant Human Bone Morphogenetic Protein-2) and MEK (MAP Kinase/ERK Kinase) Inhibitor PD0325901 Increases Bone Formation in a Murine Model of Neurofibromatosis Type I Pseudarthrosis

BACKGROUND

Congenital tibial dysplasia is a severe pediatric condition that classically results in a persistent pseudarthrosis. A majority of these cases are associated with neurofibromatosis type I (NF1), a genetic disorder in which inactivation of the NF1 gene leads to overactivity of the Ras-MEK-MAPK (mitogen-activated protein kinase) signaling pathway. We therefore hypothesized that pharmaceutical inhibition of MEK-MAPK may be a beneficial therapeutic strategy.

METHODS

In vitro methods were used to demonstrate a role for the MEK inhibitor PD0325901 in promoting osteogenic differentiation in Nf1^-/- calvarial osteoblasts. Local applications of rhBMP-2 and/or PD0325901 were then tested in a mouse model of NF1 tibial pseudarthrosis featuring localized double inactivation of the Nf1 gene in a fracture. Mice received no treatment, PD0325901 (10 mg/kg/day from two days before fracture to ten days after fracture), rhBMP-2 (10 μg), or a combination of rhBMP-2 and PD0325901.

RESULTS

Animals treated with the delivery vehicle alone, PD0325901, rhBMP-2, or the PD0325901 + rhBMP-2 combination showed union rates of 0%, 8%, 69% (p < 0.01), or 80% (p < 0.01), respectively, at twenty-one days after fracture. Mice treated with the rhBMP-2 + PD0325901 combination displayed a callus volume sixfold greater than the vehicle controls and twofold greater than the group receiving rhBMP-2 alone. Although MEK inhibition combined with rhBMP-2 led to increases in bone formation and union, the proportion of fibrous tissue in the callus was not significantly reduced.

CONCLUSIONS

The data suggest that MEK inhibition can promote bone formation in combination with rhBMP-2 in the context of an NF1 pseudarthrosis. However, PD0325901 did not promote substantive bone anabolism in the absence of an exogenous anabolic stimulus and did not suppress fibrosis.

CLINICAL RELEVANCE

This study examines a signaling pathway-based approach to treating poor bone healing in a model of NF1 pseudarthrosis.

Asfotase-α improves bone growth, mineralization and strength in mouse models of neurofibromatosis type-1

Mineralization of the skeleton depends on the balance between levels of pyrophosphate (PPi), an inhibitor of hydroxyapatite formation, and phosphate generated from PPi breakdown by alkaline phosphatase (ALP). We report here that ablation of Nf1, encoding the RAS/GTPase–activating protein neurofibromin, in bone–forming cells leads to supraphysiologic PPi accumulation, caused by a chronic ERK–dependent increase in genes promoting PPi synthesis and extracellular transport, namely Enpp1 and Ank. It also prevents BMP2–induced osteoprogenitor differentiation and, consequently, expression of ALP and PPi breakdown, further contributing to PPi accumulation. The short stature, impaired bone mineralization and strength in mice lacking Nf1 in osteochondroprogenitors or osteoblasts could be corrected by enzyme therapy aimed at reducing PPi concentration. These results establish neurofibromin as an essential regulator of bone mineralization, suggest that altered PPi homeostasis contributes to the skeletal dysplasiae associated with neurofibromatosis type-1 (NF1), and that some of the NF1 skeletal conditions might be preventable pharmacologically.

Effectiveness of recombinant human bone morphogenetic protein-7 in the management of congenital pseudoarthrosis of the tibia: a randomised controlled trial

PURPOSE

Despite the popularity and an increased use of bone morphogenetic protein to improve bone healing in patients with congenital pseudoarthrosis of the tibia (CPT), no previous study has compared its efficacy against any other procedure.

METHODS

We randomised 20 consecutive patients (mean age 4.1 years) with CPT (Crawford type IV) associated with neurofibromatosis type 1(NF1) and no previous history of surgery into two groups. Group 1 received recombinant human bone morphogenetic protein-7 (rhBMP-7) along with intramedullary Kirschner (K)-wire fixation and autologous bone grafting; group 2 received only K wire and grafting. Outcome measures were time to achieve union, Johnston grade, tibial length and the American Orthopaedic Foot and Ankle Society (AOFAS) score, which were evaluated preoperatively and at five year follow-up.

RESULTS

Study results showed that patients in group 1 achieved primary bone union at a mean of 14.5 months [standard error (SE) 5.2], whereas group 2 took a mean of 17.11 months (SE 5.0). However, the log-rank test showed no difference in healing times between groups at all time points (P = 0.636). There was a statistically significant pre- to post operative improvement (P < 0.05) within groups for the other outcome measures.

CONCLUSION

In a five year follow-up, these results suggest that rh-BMP-7 and autologous bone grafting is no better than autologous grafting alone.

Hyperactive transforming growth factor-β1 signaling potentiates skeletal defects in a neurofibromatosis type 1 mouse model

Dysregulated transforming growth factor beta (TGF-β) signaling is associated with a spectrum of osseous defects as seen in Loeys-Dietz syndrome, Marfan syndrome, and Camurati-Engelmann disease. Intriguingly, neurofibromatosis type 1 (NF1) patients exhibit many of these characteristic skeletal features, including kyphoscoliosis, osteoporosis, tibial dysplasia, and pseudarthrosis; however, the molecular mechanisms mediating these phenotypes remain unclear. Here, we provide genetic and pharmacologic evidence that hyperactive TGF-β1 signaling pivotally underpins osseous defects in Nf1(flox/-) ;Col2.3Cre mice, a model which closely recapitulates the skeletal abnormalities found in the human disease. Compared to controls, we show that serum TGF-β1 levels are fivefold to sixfold increased both in Nf1(flox/-) ;Col2.3Cre mice and in a cohort of NF1 patients. Nf1-deficient osteoblasts, the principal source of TGF-β1 in bone, overexpress TGF-β1 in a gene dosage-dependent fashion. Moreover, Nf1-deficient osteoblasts and osteoclasts are hyperresponsive to TGF-β1 stimulation, potentiating osteoclast bone resorptive activity while inhibiting osteoblast differentiation. These cellular phenotypes are further accompanied by p21-Ras-dependent hyperactivation of the canonical TGF-β1-Smad pathway. Reexpression of the human, full-length neurofibromin guanosine triphosphatase (GTPase)-activating protein (GAP)-related domain (NF1 GRD) in primary Nf1-deficient osteoblast progenitors, attenuated TGF-β1 expression levels and reduced Smad phosphorylation in response to TGF-β1 stimulation. As an in vivo proof of principle, we demonstrate that administration of the TGF-β receptor 1 (TβRI) kinase inhibitor, SD-208, can rescue bone mass deficits and prevent tibial fracture nonunion in Nf1(flox/-) ;Col2.3Cre mice. In sum, these data demonstrate a pivotal role for hyperactive TGF-β1 signaling in the pathogenesis of NF1-associated osteoporosis and pseudarthrosis, thus implicating the TGF-β signaling pathway as a potential therapeutic target in the treatment of NF1 osseous defects that are refractory to current therapies.

Calvarial defects and skeletal dysplasia in patients with neurofibromatosis Type 1

OBJECT

Skull defects, including sphenoid dysplasia and calvarial defects, are rare but distinct findings in patients with neurofibromatosis Type 1 (NF1). The underlying pathophysiology is unclear. The goal of this study was to identify the clinical characteristics and natural history of skull defects in patients with NF1.

METHODS

An electronic search engine of medical records was used to identify patients with NF1 and bony skull anomalies. All clinical, radiographic, pathology, and operative reports were reviewed. The relationship between bony anomalies and significant clinical associations was evaluated. This study received institutional review board approval.

RESULTS

Twenty-one patients were identified. The mean age at NF1 diagnosis was 4.2 years. The mean age at skull defect diagnosis was 8.8 years (9.7 years in the sphenoid wing dysplasia group and 11.9 years in the calvarial defect group). Sphenoid dysplasia was associated with a plexiform neurofibroma or dural ectasia in 73.3% and 80.0% of cases, respectively. Calvarial defects were associated with a plexiform neurofibroma or dural ectasia in 66.7% and 33.3% of patients, respectively. An absence of either an associated neurofibroma or ectasia was not noted in any patient with sphenoid wing dysplasia or 25.0% of those with calvarial defects. In 6 patients, both types of skull defects presented simultaneously. Serial imaging studies were obtained for a mean follow-up time of 7.5 years (range 0.4-20.0 years). Of these patients with serial imaging, radiographic progression was found in 60% of cases of calvarial defects and 56% of cases of sphenoid wing dysplasia. Two patients underwent surgical repair of a skull defect, and both required repeat procedures.

CONCLUSIONS

The majority of skull defects in patients with NF1 were associated with an adjacent structural lesion, such as a plexiform neurofibroma or dural ectasia. This findings from this cohort also support the concept of progression in defect size in more than half of the patients. Potential mechanisms by which these secondary lesions contribute to pathogenesis of the bony defect may include changes in the bony microenvironment. A better understanding of the pathophysiology of skull defects will help guide detection, improve treatment and outcome, and may contribute to the understanding of the pathogenesis of bony lesions in NF1.