Neurofibromatosis update

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.

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.

Congenital Pseudoarthrosis of Tibia With Anterolateral Bowing Treated With Ilizarov Ring Fixator: A Case Report

Congenital pseudarthrosis of the tibia (CPT) is a rare, dysplastic condition that is characterized by a "false joint" in the tibia, leading to potential disability. We present a rare case report of a 12-year-old male from India with a history of neurofibromatosis type 1 (NF1) and anterolateral bowing of the tibia since birth. He sustained a tibial fracture during play. X-ray evaluation confirmed the fracture, and a clinical diagnosis of CPT was established. The treatment involved corticotomy for deformity correction and stabilization using Ilizarov's ring fixation. The procedure was successful, with post-operative radiological evaluations showing significant improvement in the center of rotation of angulation (CORA) from 60° pre-operatively to 25° post-operatively. The patient was discharged with an external fixator and after seven months, transitioned to full weight-bearing ambulation with a specialized brace. The Ilizarov procedure proved to be a safe and effective treatment for CPT, offering benefits such as limb lengthening and ankle stabilization.

Neurofibromatosis type1, type 2, tuberous sclerosis and Von Hippel-Lindau disease

Neurocutaneous syndromes (also known as phakomatoses) are heterogenous group of disorders that involve derivatives of the neuroectoderm. Each disease has diagnostic and pathognomonic criteria, once identified, thorough clinical examination to the patient and the family members should be done. Magnetic resonance imaging (MRI) is used to study the pathognomonic findings withing the CNS (Evans et al. in Am J Med Genet A 152A:327-332, 2010). This chapter includes the 4 most common syndromes faced by neurosurgeons and neurologists; neurofibromatosis types 1 and 2, tuberous sclerosis and Von Hippel-Lindau disease. Each syndrome has specific genetic anomaly that involves a tumor suppressor gene and the loss of inhibition of specific pathways. The result is a spectrum of cutaneous manifestations and neoplasms.

Questions about Using the Induced Membrane Technique to Manage Cases of Congenital Tibial Pseudarthrosis

The induced membrane technique is an innovative approach for repairing critical bone defects and has been applied recently in patients with congenital pseudarthrosis of the tibia (CPT). CPT is frequently associated with neurofibromatosis type 1 (NF1). Here, we briefly describe the clinical results of the induced membrane technique in NF1-deficient patients with CPT and in an animal model of CPT. Furthermore, we discuss the hypotheses used to explain inconsistent outcomes for the induced membrane technique in CPT-especially when associated with NF1.

Molecular Dissection of Somatic Skeletal Disease in Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is a tumor predisposition syndrome caused by heterozygous NF1 gene mutations. Patients with NF1 present with pleiotropic somatic secondary manifestations, including development of bone pseudarthrosis after fracture. Somatic NF1 gene mutations were reproducibly identified in patient-derived pseudarthrosis specimens, suggesting a local mosaic cell population including somatic pathologic cells. The somatic cellular pathogenesis of NF1 pseudarthroses remains unclear, though defects in osteogenesis have been posited. Here, we applied time-series single-cell RNA-sequencing (scRNA-seq) to patient-matched control and pseudarthrosis-derived primary bone stromal cells (BSCs). We show that osteogenic specification to an osteoblast progenitor cell population was evident for control bone-derived cells and haploinsufficient pseudarthrosis-derived cells. Similar results were observed for somatic patient fracture-derived NF1^-/- cells; however, expression of genetic pathways associated with skeletal mineralization were significantly reduced in NF1^-/- cells compared with fracture-derived NF1^+/- cells. In mice, we show that Nf1 expressed in bone marrow osteoprogenitors is required for the maintenance of the adult skeleton. Results from our study implicate impaired Clec11a-Itga11-Wnt signaling in the pathogenesis of NF1-associated skeletal disease. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Safety and Efficacy of Mek Inhibitors in the Treatment of Plexiform Neurofibromas: A Retrospective Study

INTRODUCTION

Plexiform neurofibromas (PN) represent the main cause of morbidity in patients affected by Neurofibromatosis Type 1 (NF1). Until recently, surgery has been the main treatment option in these patients, but it is burdened with a low efficacy rate and a high incidence of side effects as well as recurrence. In recent years, MEK inhibitors (MEKi) such as selumetinib and trametinib have shown great promise.

METHODS

We retrospectively describe a single center cohort of NF1 patients affected by PN1 and treated with MEKi since 2019 to 2021. Patients recruited in the study were affected by PN that were not eligible to complete surgical excision, symptomatic or with major cosmetic deformation or functional neurological deficits.

RESULTS

Most patients experienced improvement in clinical symptoms and quality of life, with reduction or stabilization of lesions. However, no complete response was achieved. The most common adverse effects involved the skin, affecting every patient. Importantly, no life-threatening adverse effects occurred.

CONCLUSIONS

In our experience, MEKi treatment has been shown to be both safe and effective in improving symptomatology and quality of life.

Congenital Pseudoarthrosis of the Tibia: A Narrative Review

Congenital pseudoarthrosis of the tibia, also known as CPT, is a rare bone disease mostly occurring in the pediatric age group of 10. The case generally represents anterolateral bowing of the tibia with refractures. This condition is quite rare and has very few cases per year. CPT is still a challenging concern in orthopedics. Bone reunion often requires repeated surgical measurements. With advancements, we have new treatment plans that include induced membrane techniques and bone marrow stromal cell grafts of various induced and morphogenetic protein, which still requires confirmation. Different treatment strategies based on surgical, mechanical, and biological concepts have been shown with varying success rates. Ilizarov technique and vascularised fibular grafts have vastly increased the effectiveness in treating CPT of the tibia. Constant and recurrent refracture, residual deformities, and difficulty obtaining bone union remain the challenges in managing CPT. Hence, phasing CPT as bowing the tibia in an anterolateral fashion is more appropriate because it's a heterogeneous entity with varying prognoses.

New insights into pathogenesis of congenital pseudarthrosis of tibia in children using periosteum proteomics analysis

RATIONALE

The exact etiology and pathogenesis of congenital pseudarthrosis of tibia (CPT) are not clear. Quantitative proteomics analysis plays a vital role in disease pathology research. Tandem mass tag (TMT)-based proteomics techniques were employed to identify and analyze the differentially expressed proteins (DEP) in the tibia periosteum tissues of CPT patients.

METHODS

The samples were divided into three groups: CPT with NF1 group, CPT without NF1 group (non-NF1-CPT), and control group (patients with open tibial fracture). A fold change ≥1.5 or ≤0.66 and P-value <0.05 were used as the thresholds to screen DEPs. Subsequently, bioinformatics resources such as online tools DAVID and String were used to generate gene ontology (GO) annotation, KEGG pathways enrichment, and protein-protein interaction (PPI) network for these DEPs.

RESULTS

The results show that a total of 347 proteins were differentially expressed in NF1-CPT groups, 212 of which were upregulated and 135 were downregulated. There were more DEPs in non-NF1-CPT groups; we identified 467 DEPs, including 281 upregulated and 186 downregulated. Among them, NF1-CPT groups and non-NF1-CPT groups shared 231 DEPs, and the remaining 230 DEPs showed the same expression trend in the two disease groups, with 117 upregulated and 113 downregulated. In particular, 116 proteins were altered only in NF1-CPT groups (94 were upregulated and 22 were downregulated), whereas 236 proteins were altered only in non-NF1-CPT groups (164 were upregulated and 72 were downregulated). Finally, compared with non-NF1-CPT groups, 47 proteins changed 1.5-fold and P-value < 0.05 in NF1-CPT groups.

CONCLUSIONS

To sum up, we found that common DEPS in periosteum of NF1-CPT and non-NF1-CPT groups are mainly involved in cell matrix assembly, cell adhesion, AKT-PI3K signal pathway activation, and vascular agglutination, which indicate that these are the pathological characteristics of CPT. The osteogenic ability is weak, the osteoclastic ability is strong, the vascular lumen is narrow, the invasive growth and the proliferation of fibroblasts are enhanced in CPT patients.

Identifying Bone Matrix Impairments in a Mouse Model of Neurofibromatosis Type 1 (NF1) by Clinically Translatable Techniques

Three-to-four percent of children with neurofibromatosis type 1 (NF1) present with unilateral tibia bowing, fracture, and recalcitrant healing. Alkaline phosphatase (ALP) enzyme therapy prevented poor bone mineralization and poor mechanical properties in mouse models of NF1 skeletal dysplasia; but transition to clinical trials is hampered by the lack of a technique that (i) identifies NF1 patients at risk of tibia bowing and fracture making them eligible for trial enrollment and (ii) monitors treatment effects on matrix characteristics related to bone strength. Therefore, we assessed the ability of matrix-sensitive techniques to provide characteristics that differentiate between cortical bone from mice characterized by postnatal loss of Nf1 in Osx-cre^Tet-Off ;Nf1^flox/flox osteoprogenitors (cKO) and from wild-type (WT) mice. Following euthanasia at two time points of bone disease progression, femur and tibia were harvested from both genotypes (n ≥ 8/age/sex/genotype). A reduction in the mid-diaphysis ultimate force during three-point bending at 20 weeks confirmed deleterious changes in bone induced by Nf1 deficiency, regardless of sex. Pooling females and males, low bound water (BW), and low cortical volumetric bone mineral density (Ct.vBMD) were the most accurate outcomes in distinguishing cKO from WT femurs with accuracy improving with age. Ct.vBMD and the average unloading slope (Avg-US) from cyclic reference point indentation tests were the most sensitive in differentiating WT from cKO tibias. Mineral-to-matrix ratio and carbonate substitution from Raman spectroscopy were not good classifiers. However, when combined with Ct.vBMD and BW (femur), they helped predict bending strength. Nf1 deficiency in osteoprogenitors negatively affected bone microstructure and matrix quality with deficits in properties becoming more pronounced with duration of Nf1 deficiency. Clinically measurable without ionizing radiation, BW and Avg-US are sensitive to deleterious changes in bone matrix in a preclinical model of NF1 bone dysplasia and require further clinical investigation as potential indicators of an onset of bone weakness in children with NF1. © 2022 American Society for Bone and Mineral Research (ASBMR).

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.

Neurofibromatosis from Head to Toe: What the Radiologist Needs to Know

Neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2) are autosomal dominant inherited neurocutaneous disorders or phakomatoses secondary to mutations in the NF1 and NF2 tumor suppressor genes, respectively. Although they share a common name, NF1 and NF2 are distinct disorders with a wide range of multisystem manifestations that include benign and malignant tumors. Imaging plays an essential role in diagnosis, surveillance, and management of individuals with NF1 and NF2. Therefore, it is crucial for radiologists to be familiar with the imaging features of NF1 and NF2 to allow prompt diagnosis and appropriate management. Key manifestations of NF1 include café-au-lait macules, axillary or inguinal freckling, neurofibromas or plexiform neurofibromas, optic pathway gliomas, Lisch nodules, and osseous lesions such as sphenoid dysplasia, all of which are considered diagnostic features of NF1. Other manifestations include focal areas of signal intensity in the brain, low-grade gliomas, interstitial lung disease, various abdominopelvic neoplasms, scoliosis, and vascular dysplasia. The various NF1-associated abdominopelvic neoplasms can be categorized by their cellular origin: neurogenic neoplasms, interstitial cells of Cajal neoplasms, neuroendocrine neoplasms, and embryonal neoplasms. Malignant peripheral nerve sheath tumors and intracranial tumors are the leading contributors to mortality in NF1. Classic manifestations of NF2 include schwannomas, meningiomas, and ependymomas. However, NF2 may have shared cutaneous manifestations with NF1. Lifelong multidisciplinary management is critical for patients with either disease. The authors highlight the genetics and molecular pathogenesis, clinical and pathologic features, imaging manifestations, and multidisciplinary management and surveillance of NF1 and NF2. Online supplemental material is available for this article. ^©RSNA, 2022.

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 options for congenital pseudarthrosis of tibia in children: cross-union versus other options: a systematic review

The systematic review aimed to provide a comprehensive update on various surgical treatment options for congenital pseudarthrosis of tibia (CPT) in children and the outcome achieved in terms of union, union time and complications of non-union and refracture. A literature search was performed in PubMed (including Medline) database for broad keywords: 'Congenital pseudarthrosis of tibia and children'. Studies selected included full-text articles on surgical treatments of CPT following: intra-medullary rod (IMR)/Ilizarov/combined IMR with Ilizarov/vascularized fibular graft (VFG) and cross-union. Out of 719 studies, 57(1227 CPT patients/1235 tibias) were included for review. Cross-union group had 100% union rate with no non-unions, least refracture rate (22.5%) and minimal time to primary union (4.5 months). For IMR, Ilizarov, combined IMR with Ilizarov and VFG, the respective results were as follows: primary union rates - 67.7, 84.2, 83.7 and 65.3%; final union - 76.5, 81.5, 92.4 and 87.1%; primary union time - 12.6, 9.3, 5.3 and 9.5 months; non-union rates - 17.0, 13.6, 6.0 and 7.9%; refracture rates - 48.1, 47.7, 33.7 and 34.6%. The success probability was lowest for IMR (35.2%), 44% for Ilizarov, 55.5% for combined IMR with Ilizarov, 42.7% for VFG and highest 77.5% for cross-union group. Outcomes of the more recent cross-union technique fare better than other surgical methods. However, studies on cross-union are few and longer follow-up is lacking. Combined IMR with Ilizarov and VFG have better results compared to IMR or Ilizarov alone.

RASopathies: The musculoskeletal consequences and their etiology and pathogenesis

The RASopathies comprise an ever-growing number of clinical syndromes resulting from germline mutations in components of the RAS/MAPK signaling pathway. While multiple organs and tissues may be affected by these mutations, this review will focus on how these mutations specifically impact the musculoskeletal system. Herein, we review the genetics and musculoskeletal phenotypes of these syndromes in humans. We discuss how mutations in the RASopathy syndromes have been studied in translational mouse models. Finally, we discuss how signaling molecules within the RAS/MAPK pathway are involved in normal and abnormal bone biology in the context of osteoblasts, osteoclasts and chondrocytes.

Phenotyping spinal abnormalities in patients with Neurofibromatosis type 1 using whole-body MRI

Neurofibromatosis Type 1 (NF1) has been reported to be associated with a variety of spinal abnormalities. The purpose of this study was to quantify the prevalence of spinal abnormalities in a collective of NF1 patients that is representative for the general NF1 population, to associate the co-appearance of spinal abnormalities with both NF1 and clinical symptoms and to investigate if different mutations of the NF1 gene affect the prevalence of these abnormalities. Retrospectively, 275 patients with NF1 and an age- and sex-matched collective of 262 patients were analyzed. The prevalence of spinal abnormalities was recorded. Mutational analysis of the NF1 gene was obtained in 235 NF1 patients. Associations between spinal abnormalities, clinical symptoms and genotype were investigated by binary logistic regression analysis. Prevalence of all spinal abnormalities was higher in NF1 patients than in the control group. Six characteristics of spinal abnormalities were significantly associated with NF1 (all p < 0.05). An influence of scalloping on scoliosis (OR 3.01; p = 0.002); of meningoceles (OR 7.63) and neuroforaminal tumors (OR 2.96) on scalloping, and of dural ectasia on neuroforaminal tumors (OR 1.93) was identified. Backpain and loss of motor function were associated with neuroforaminal tumors, spinal tumors and scalloping of vertebral bodies (all p < 0.05). Specific mutations of the NF1 gene were not relevantly associated with the development of spinal abnormalities. These findings can aid clinicians to improve clinical care of NF1 patients by creating awareness for co-appearences of specific spinal abnormalities and associated symptoms.

Schwannoma and Neurofibroma, Originating from the Ulnar Nerve in Neurofibromatosis: A Case Report and Review of the Literature

Schwannomas and neurofibromas are rare benign tumors originating from the peripheral nerve sheath. Tumors in neurofibromatosis are mostly neurofibromas and often appear in the soft tissue of peripheral nerves. In this report, a patient presented with two large adjacent soft tissue tumors in the right wrist and distal forearm which originated from a common nerve. A schwannoma had formed beside a neurofibroma from the ulnar nerve and induced numbness and paresthesia in the little and ring fingers. Although the patient had café au lait spots on the skin, neurofibromatosis was not suspected due to lack of symptoms. The patient was referred to the current research clinic suffering from two soft tissue masses in the wrist and ulnar nerve dysfunction. In neurofibromatosis patients, two tumors of a different nature originating from a common nerve close together have rarely been described in the literature. The patient was treated by en bloc excision of the mass while protecting the nerve fascicles. The follow-up results indicated no neurological symptoms and complete restoration of ulnar nerve function.

Management of Proximal Thoracic Kyphoscoliosis with Early Myelopathy in a Young Adult with Neurofibromatosis Type 1: A Case Report and Review of Literature

INTRODUCTION

Neurofibromatosis (NF) 1 is associated with skeletal deformities. Scoliosis is seen in about 10-64% of NF-1 patients. NF-1 may be associated with dystrophic or non-dystrophic type of curve. There are technical difficulties in treating large dystrophic curve with proximal thoracic kyphoscoliosis in NF-1. This case report and subsequent review of literature attempts to provide a line of management for such difficult lesions.

MATERIALS AND METHODS

We present a case of 22-year-old male with NF-1 who came to us with gradually progressive upper back deformity and signs of early myelopathy for 2-3 months. The patient had a 100° proximal thoracic kyphosis and 100° scoliosis with no neurological deficit and brisk reflexes. A single stage posterior fixation with three column osteotomy at the apex of the curve was performed.

RESULTS

The kyphosis was corrected to 65° from 100, the scoliosis was corrected to 60° from 100. Clinically, the hump in the upper back was visibly reduced. At 1-year follow-up, the patient remained asymptomatic with no loss of correction and implant breakage on X-ray.

CONCLUSION

Large dystrophic proximal thoracic kyphoscoliosis is a difficult lesion to treat and can be managed with an all posterior approach, achieving good cosmetic and neurological outcomes, as demonstrated by this case.

Management of spinal deformities and tibial pseudarthrosis in children with neurofibromatosis type 1 (NF-1)

The skeletal system is affected in up to 60% of patients with neurofibromatosis type 1. The most commonly observed entities are spinal deformities and tibial dysplasia. Early recognition of radiologic osseous dystrophy signs is of utmost importance because worsening of the deformities without treatment is commonly observed and surgical intervention is often necessary. Due to the relative rarity and the heterogenic presentation of the disease, evidence regarding the best surgical strategy is still lacking.

PURPOSE

To report our experience with the treatment of skeletal manifestations in pediatric patients with (neurofibromatosis type 1) NF-1 and to present the results with our treatment protocols.

MATERIALS AND METHODS

This is a retrospective, single expert center study on children with spinal deformities and tibial dysplasia associated with NF-1 treated between 2006 and 2020 in a tertiary referral institution.

RESULTS

Spinal deformity: Thirty-three patients (n = 33) were included. Mean age at index surgery was 9.8 years. In 30 patients (91%), the deformity was localized in the thoracic and/or lumbar spine, and in 3 patients (9%), there was isolated involvement of the cervical spine. Eleven patients (33%) received definitive spinal fusion as an index procedure and 22 (67%) were treated by means of "growth-preserving" spinal surgery. Halo-gravity traction before index surgery was applied in 11 patients (33%). Progression of deformity was stopped in all patients and a mean curve correction of 60% (range 23-98%) was achieved. Mechanical problems with instrumentation requiring revision surgery were observed in 55% of the patients treated by growth-preserving techniques and in none of the patients treated by definitive fusion. One patient (3%) developed a late incomplete paraplegia due to a progressive kyphotic deformity. Tibial dysplasia: The study group comprised of 14 patients. In 5 of them (36%) pathological fractures were present on initial presentation. In the remaining 9 patients (64%), anterior tibial bowing without fracture was observed initially. Four of them (n = 4, 28%) subsequently developed a pathologic fracture despite brace treatment. Surgical treatment was indicated in 89% of the children with pathological fractures. This involved resection of the pseudarthrosis, autologous bone grafting, and intramedullary nailing combined with external fixation in some of the cases. In 50% of the patients, bone morphogenic protein was used "off-label" in order to promote union. Healing of the pseudarthrosis was achieved in all of the cases and occurred between 5 to 13 months after the index surgical intervention. Four of the patients treated surgically needed more than one surgical intervention in order to achieve union; one patient had a re-fracture. All patients had a good functional result at last follow-up.

CONCLUSION

Early surgical intervention is recommended for the treatment dystrophic spinal deformity in children with NF-1. Good and sustainable curve correction without relevant thoracic growth inhibition can be achieved with growth-preserving techniques alone or in combination with short spinal fusion at the apex of the curve. Preoperative halo-gravity traction is a safe and very effective tool for the correction of severe and rigid deformity in order to avoid neurologic injury. Fracture union in tibial dysplasia with satisfactory functional results can be obtained in over 80% of the children by means of surgical resection of the pseudarthrosis, intramedullary nailing, and bone grafting. Wearing a brace until skeletal maturity is achieved is mandatory in order to minimize the risk of re-fracture.

National Trends in Spinal Fusion Surgery for Neurofibromatosis

STUDY DESIGN

Analysis of a national database.

OBJECTIVE

To analyze trends in spinal fusion surgery for neurofibromatosis type I (NF-1) patients and to compare the surgical approaches.

SUMMARY OF BACKGROUND DATA

The preferred surgical approach for fusion treatment of spinal deformity in NF is not well established.

METHODS

We identified 548 patients with a diagnosis of NF-1 who had received spinal fusion surgery between 2003 and 2014. We compared posterior spinal fusion (PSF), anterior-posterior spinal fusion (APSF), and anterior spinal fusion with respect to patient demographics, institutional characteristics, in-hospital complications, and hospitalization lengths and costs. Significance was set at a value of p less than .05.

RESULTS

The number of spinal fusions for NF-1 significantly increased (p = .02) over the study period. The rate of PSF surgeries increased 2.9-fold, whereas the rate of APSF surgeries decreased 2.2-fold. There was also a significant association between the location of the fusion and surgical approach (p<.01), with 66% of ASF cases being cervical spine cases. Compared with patients undergoing PSF and ASF, patients undergoing APSF were significantly younger (p<.01) and had significantly higher hospitalization lengths and costs (p<.01). APSF costs were $180,714 as compared to $144,027 for PSF and $105,312 for ASF.

CONCLUSIONS

There have been significant increases in the rate of spinal fusion surgeries for NF-1 patients. Surgical treatment has shifted over the years and is dependent on the location of the deformity. Patients undergoing APSF are significantly younger.

LEVEL OF EVIDENCE

Level III.

Evaluation of bone marrow-derived mesenchymal stem cell quality from patients with congenital pseudoarthrosis of the tibia

Background

The treatment of congenital pseudoarthrosis of the tibia (CPT) remains challenging in pediatric orthopedics due to the difficulties in bone union, continuous angulation, joint stiffness, and severe limb length discrepancy. Mesenchymal stem cells (MSCs) therapy offers a complementary approach to improve the conventional surgical treatments. Although the autologous MSC treatment shows a promising strategy to promote bone healing in CPT patients, the quality of MSCs from CPT patients has not been well studied. The purpose of this study is to investigate the quality of MSCs isolated from patients with CPT.

Methods

The bone marrow-derived MSCs from the fracture site and iliac crest of six CPT patients were isolated and compared. The cumulative population doubling level (cPDL), phenotype characteristics, and trilineage differentiation potency were observed to assess the quality of both MSCs.

Results

There were no significant differences of the MSCs derived from the fracture site and the MSCs from the iliac crest of the subjects, in terms of cPDL, phenotype characteristics, and trilineage differentiation potency (all p > 0.05). However, MSCs from the fracture site had a higher senescence tendency than those from the iliac crest.

Conclusion

MSC quality is not the main reason for delayed bone regeneration in those with CPT. Thus, autologous MSC is a promising source for treating CPT patients

Neurofibromatosis type I and multiple myeloma coexistence: A possible link?

The association between Neurofibromatosis type I (NF1) and multiple myeloma (MM), a plasma cell, dyscrasia is very rare. Here we put to the attention of the scientific community two new cases. The first one is a patient with active MM whereas the second with smoldering MM. Both patients present typical features of NF1 but skeletal alterations were present only in the second case including dysplasia, marked scoliosis and osteoporosis. MM osteolytic lesions were absent in both patients. In addition to the clinical diagnosis of NF1, a molecular testing for NF1 gene mutations has been performed finding that patient one was heterozygous for the c.6855C>A (Tyr2285Ter) mutation, while patient two was heterozygous for the c.7838dupC (Lys2614GlufsTer20) mutation. The two mutations were diagnosed both in genomic DNA from peripheral blood and from MM cells. The potential link between NF1 mutation and the increased risk of MM is discussed in the report.

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.

Pseudoartrosis congénita de antebrazo asociada a luxación de radio proximal: Tratamiento quirúrgico mediante antebrazo de un solo hueso. [Congenital forearm pseudoarthrosis associated with proximal radius dislocation: Surgical treatment using a single bone forearm.]

<p><strong>Introducción</strong></p><p><strong></strong>La pseudoartrosis congénita de antebrazo es una entidad clínica rara que se asocia a habitualmente Neurofibromatosis tipo 1. La lesión de ambos huesos del antebrazo asociada con luxación de cabeza de radio es extremadamente inusual.</p><p><strong><em> </em>Material y métodos</strong></p><p><strong></strong>Se presenta el caso de una niña de 13 años de edad con Neurofibromatosis tipo 1 y pseudoartrosis de ambos huesos del antebrazo asociada a luxación de la cabeza de radio. Se le realizó escisión amplia de la pseudoartrosis y reconstrucción mediante antebrazo de un hueso con placa. La primer cirugía fracasó y requirió una revisión con retiro del implante, injerto óseo autólogo y fijación con enclavado endomedular. Luego de la segunda cirugía, la niña presenta un antebrazo de un hueso estable, con un acortamiento de 7cms. En el último control, 4 años después, la paciente se encuentra asintomática y utiliza el miembro superior con una mínima limitación de la flexo-extensión de muñeca.</p><p><em> </em><strong>Conclusión</strong></p><p><strong></strong>La reconstrucción mediante antebrazo de un hueso es una opción razonable para la pseudoartrosis de ambos huesos del antebrazo con luxación de cabeza radial en niños. El procedimiento de salvataje, produce un miembro superior estable, con una función satisfactoria de muñeca y codo.</p>

Femoral overgrowth in children with congenital pseudarthrosis of the Tibia

Background

Having observed a tendency towards femoral overgrowth (FO) of the affected limb in children with atrophic-type congenital pseudarthrosis of the tibia (CPT), we aimed to identify the incidence of, contributors to, and patterns of FO among such children.

Methods

We retrospectively evaluated 55 children with CPT, 22 with prepseudarthrosis and 33 with atrophic-type CPT from 1989 to 2012. FO was defined as an affected femoral segment ≥10 mm longer than the contralateral segment. We investigated FO incidences in prepseudarthrosis versus atrophic-type CPT. Sex, laterality, coexistence of neurofibromatosis type 1, development of frank pseudarthrosis, extent of tibial shortening, shortening in foot height, deformity severity, distraction osteogenesis (DO) treatment, refracture, increased femoral neck-shaft angle, tibiofemoral angle, and ankle valgus angle were investigated to identify potential contributors to FO. Patterns of FO were also determined.

Results

At initial presentation, 11 patients exhibited a mean of 13 mm (10–23) of FO. However, the nature of FO changed over time during the follow-up period (mean, 10.8 years; range, 4.3–19.3). At the last follow-up, 14 patients presented with a mean of 12 mm (10–18) of FO. With the exception of one patient, all patients with FO presented with atrophic-type CPT. Frank pseudarthrosis, DO treatment, and increased femoral neck-shaft angle were significantly associated with FO (p = 0.016, p = 0.001, and p = 0.005, respectively). Diverse patterns of FO were observed.

Conclusions

FO of the affected limb is frequently encountered in patients with atrophic-type CPT. A compensatory response to frank pseudarthrosis, DO treatment, and neurofibromatosis may play a role in the diverse patterns of FO.

Triterpenoid saponin flaccidoside II from Anemone flaccida triggers apoptosis of NF1-associated malignant peripheral nerve sheath tumors via the MAPK-HO-1 pathway

Malignant peripheral nerve sheath tumors (MPNSTs) are highly aggressive soft tissue neoplasms that are extremely rare and are frequently associated with neurofibromatosis type 1 patients. MPNSTs are typically fatal, and there is no effective treatment so far. In our previous study, we showed that flaccidoside II, one of the triterpenoid saponins isolated from Anemone flaccida Fr. Schmidt, has antitumor potential by inducing apoptosis. In the present study, we found that flaccidoside II inhibits proliferation and facilitates apoptosis in MPNST cell lines ST88-14 and S462. Furthermore, this study provides a mechanism by which the downregulation of heme oxygenase-1 via extracellular signal-regulated kinase-1/2 and p38 mitogen-activated protein kinase pathways is involved in the apoptotic role of flaccidoside II. This study suggested the potential of flaccidoside II as a novel pharmacotherapeutic approach for MPNSTs.

Morphological Differences in the Vertebrae of Scoliosis Secondary to Neurofibromatosis Type 1 With and Without Paraspinal Neurofibromas

STUDY DESIGN

A retrospective study.

OBJECTIVE

Aim of the study was to investigate morphological differences in the vertebrae of scoliosis secondary to neurofibromatosis type 1 (NF1-S) with and without paraspinal neurofibromas and to identify the relationship between paraspinal neurofibromas and vertebral deformity.

SUMMARY OF BACKGROUND DATA

Scoliosis is the most common orthopedic manifestation of NF1. Erosion or infiltration of the bone by localized neurofibromas was suggested as one of the primary etiology for the vertebral deformity.

METHODS

One hundred fourteen patients with NF1-S were classified into spinal tumor (ST) group and nontumor (NT) group with respect to the presence of paraspinal neurofibromas. The curve pattern, curve magnitude, the shape and location of paraspinal neurofibromas, and various kinds of morphological changes of vertebrae were evaluated by complete radiographs were compared between the two groups to determine whether the presence of paraspinal neurofibromas could be associated with a more severe vertebral deformity.

RESULTS

The ST and NT groups included 54 patients (age, 16.8 ± 5.5 years) and 60 patients (age, 17.3 ± 4.2 years), respectively. The Cobb angles of the main curve were 72.3° ± 20.6° and 65.4° ± 19.4° for the ST and NT groups, respectively. No significant differences were observed between the two groups in age, sex ratio, and Cobb angle. There were significant differences between the ST and NT groups in apical vertebral rotation (36.8° ± 7.2° vs. 27.5° ± 6.8°; P < 0.001) and the prevalence of rotatory subluxation (66.1% vs. 35.0%; P = 0.04). Most of the paraspinal neurofibromas (70.4%) developed within the apical region, with the majority (29/38) located on the concave side.

CONCLUSION

The NF1-S patients with paraspinal neurofibromas had significantly higher prevalence of morphological changes of vertebrae. The paraspinal neurofibromas, most of which were located on the concave side of the apical region, could be associated with more severe vertebral deformities.

LEVEL OF EVIDENCE

3.

Capturing the wide variety of impaired fracture healing phenotypes in Neurofibromatosis Type 1 with eight key factors: a computational study

Congenital pseudarthrosis of the tibia (CPT) is a rare disease which normally presents itself during early childhood by anterolateral bowing of the tibia and spontaneous tibial fractures. Although the exact etiology of CPT is highly debated, 40–80% of CPT patients are carriers of a mutation in the Neurofibromatosis Type 1 (NF1) gene, which can potentially result in an altered phenotype of the skeletal cells and impaired bone healing. In this study we use a computational model of bone regeneration to examine the effect of the Nf1 mutation on bone fracture healing by altering the parameter values of eight key factors which describe the aberrant cellular behaviour of Nf1 haploinsufficient and Nf1 bi-allelically inactivated cells. We show that the computational model is able to predict the formation of a hamartoma as well as a wide variety of CPT phenotypes through different combinations of altered parameter values. A sensitivity analysis by “Design of Experiments” identified the impaired endochondral ossification process and increased infiltration of fibroblastic cells as key contributors to the degree of severity of CPT. Hence, the computational model results have added credibility to the experimental hypothesis of a genetic cause (i.e. Nf1 mutation) for CPT.

Ilizarov bone transport as a treatment of congenital pseudarthrosis of the tibia: a long-term follow-up study

PURPOSE

Most studies on congenital pseudarthrosis of the tibia (CPT) report on the short-term union rate and refracture rate but do not take into account the long-term outcome. This review includes patients treated with an Ilizarov bone transport, who all reached skeletal maturity. It describes long-term results and highlights any prognostic factors that could predict the final outcome.

METHODS

The records of patients with CPT treated with an Ilizarov bone transport in our institution were retrospectively evaluated.

RESULTS

A total of 12 consecutive patients were studied. The mean follow-up was 24.5 years (range 6-39 years). Primary consolidation was seen in ten patients (83 %). Half of these patients had a refracture. At final follow-up, eight patients experienced union and four remained un-united, of whom one had an amputation.

CONCLUSIONS

The present data confirm a good primary healing rate. However, tibial union at final follow-up was only seen in 67 %, indicating that refracture is the main issue. United bone is often of inferior biological and mechanical quality, so lifetime protection with intramedullary devices, braces or a combination of both is recommended.

Dural ectasia in a child with Larsen syndrome

INTRODUCTION

We present a case of an incidental finding of dural ectasia in a child diagnosed with Larsen syndrome. Larsen syndrome is a rare inherited disorder of connective tissue characterized by facial dysmorphism, congenital joint dislocations of the hips, knees and elbows, and deformities of the hands and feet. Dural ectasia is as an abnormal expansion of the dural sac surrounding the spinal cord and may result in spinal morphologic changes, instability, and spontaneous dislocation. To the best of our knowledge, the presence of dural ectasia in Larsen syndrome has not previously been reported.

CASE STUDY

A 6-year-old boy diagnosed with Larsen syndrome presented with an upper thoracic curve measuring 74 degrees, a right thoracic curve measuring 65 degrees, and significant cervicothoracic kyphosis with 50% anterior subluxation of C6 on C7 and C7 on T1. Advanced imaging studies showed dural ectasia (evidenced by spinal canal and dural sac expansion), thinning of pedicles and lamina, and C4 and C6 pars defects with cervical foramen enlargement. The patient received growing rod instrumentation (attached to cervical spine fixation) by a combined anterior/posterior surgical approach using intraoperative halo. Complications included intraoperative medial breach (fully resolved), wound dehiscence, 2 instances of bilateral broken rods, and a broken cervical rod. Following 7 lengthening procedures, the patient underwent definitive fusion.

DISCUSSION

Surgeons should be aware of the potential for dural ectasia in patients with Larsen syndrome. Its presence will cause difficulties in the surgical intervention for spinal deformity. Multiple factors must be considered, and surgical approach and technique will require modification to avoid complications. Although dural ectasia confounds surgical intervention in these patients, surgery still appears to outweigh the risks associated with delayed intervention. The presence of dural ectasia should not preclude surgical decompression and stabilization. This report adds to the body of knowledge on the treatment of Larsen syndrome by demonstrating the potential existence of dural ectasia and highlights the importance of careful and thorough preoperative evaluation and diagnostic imaging.

Successful treatment of congenital pseudarthrosis of the tibia: still a challenge

The congenital pseudarthrosis of the tibia (CPT) is one of the most challenging problems in pediatric orthopedics. The primary treatment goals are outlined as osteosynthesis, stabilization of the ankle mortise by fibular stabilization and lower-limb-length equalization. Despite the fact that each of the aforementioned goals is difficult to be achieved regardless the surgical option, the main biological consideration is the same: pseudarthrosis resection, biological bone bridging of the defect by stable fixation and the correction of any angular deformity. The external fixation method is suggested as valuable treatment of CPT because it can address not only pseudarthrosis but also all complex deformities associated with this condition. However, treatment of CPT is impaired with complications due to the complex nature of the disease thus failure is common. The most common of these are refracture, growth disturbance, poor foot and ankle function with stiffness. Of these, refracture is the most common and serious complication after primary healing and might result in the reestablishment of pseudarthrosis. Therefore, an effective, safe and practical treatment method that minimizes the residual challenges after healing and accomplishes the multiple goals of treatment is needed. In this article, we report a patient with CPT treated successfully with external fixation. Level of evidence IV retrospective.

Diagnosis and treatment of osteopenic fractures in children

Osteopenic fractures occur in children every day. At times the osteopenic nature of these fractures is painfully obvious, as in neurofibromatosis and osteogenesis imperfecta, while in many other situations overt osteopenia does not declare itself, such as in normal and obese children. Normal pediatric bone growth commonly involves periods of relative bone weakness. Childhood obesity creates a situation where bone is unable to fully adapt to the stresses placed upon it. Conditions like neurofibromatosis and osteogenesis imperfecta place pediatric bone at a distinct genetic disadvantage. This review will highlight recent research in these areas and provide radiographic examples of the treatment of osteopenic fractures in children.

Is double inactivation of the Nf1 gene responsible for the development of congenital pseudarthrosis of the tibia associated with NF1?

The pathogenic mechanism responsible for congenital pseudarthrosis of the tibia (CPT) is not well understood although the possibility of double inactivation of the neurofibromatosis type 1 (Nf1) gene has been suggested. In the present study, loss of heterozygosity was investigated in fibrous hamartoma tissues harvested from 16 patients with CPT associated with NF1 using four genetic markers that span the Nf1 gene. Based on the assumption that a single cell with double inactivation of Nf1 would undergo clonal growth and cause fibrous hamartoma, we investigated clonality in fibrous hamartoma tissues by analyzing X-chromosome inactivation patterns in 11 female patients. Loss of Nf1 heterozygosity in fibrous hamartoma tissues was observed at one or two genetic markers in 4 out of the 16 patients tested. In clonality assays, 3 of 11 patients showed a clonal growth pattern, 5 a non-clonal pattern, and 3 were non-informative. These findings support that double inactivation of the Nf1 gene and subsequent clonal growth could be a pathogenic feature of the fibrous hamartoma tissue at least in some of the CPT but might not be essential requirements of CPT development.

Musculoskeletal manifestations of neurofibromatosis type 1

OBJECTIVE

We will describe and illustrate various musculoskeletal manifestations of neurofibromatosis type 1 (NF1) encountered on imaging studies.

CONCLUSION

Because NF1 is one of the most common genetic disorders, radiologists should be familiar with its imaging manifestations.

A benign form of congenital anterolateral bowing of the tibia associated with ipsilateral polydactyly of the hallux: case report and literature review

Congenital anterolateral bowing of the tibia is generally considered a precursor of congenital pseudarthrosis of the tibia (CPT), which is usually associated with neurofibromatosis type 1 (NF1), a common autosomal dominant genetic disorder. In many cases, NF1 is initially suspected following the presentation of a child with anterolateral tibial bowing. The prognosis of CPT is poor, and amputation may be required. Congenital anterolateral bowing of the tibia combined with ipsilateral polydactyly of the hallux (CABTP) is a rare entity that resembles the anterolateral tibial bowing that occurs in association with CPT, and may be misdiagnosed as NF1. However, spontaneous correction of the tibial bowing with an almost normal fibula has been described in all previously reported cases. Here, we report three patients with CABTP and discuss the physical and imaging characteristics and follow-up results. We suggest that given the spontaneous resolution of bowing, the absence of neurocutaneous signs and the relatively favorable prognosis, CABTP is a distinct entity that merits its own place within the field of anterolateral bowing of the tibia and has no association with CPT or NF1. This should help avoid unnecessary investigations and interventions for NF1. This article shows for the first time tibial duplication in the area of bowing, with two medullary canals surrounded by well-defined cortex on CT.

Phalanges deformity associated with neurofibromatosis-1: a case report

We present a case of phalangeal deformity in a 17-year-old boy. The deformity was caused by a neurofibroma associated with neurofibromatosis type 1, affecting the left ring finger. The mass was surgically resected. Recurrence had not occurred at three-year follow-up.

Lengthening of the normal tibia in a patient with hemihypertrophy caused by Klippel- Trenaunay-Weber syndrome: a case report

We report a case of Klippel-Trenaunay-Weber syndrome in a 31-year-old woman who presented with hypertrophy of the left leg. She had severe osteoarthritic changes in the left hip joint secondary to the lack of acetabular coverage of the femoral head as the result of lateral inclination of the pelvis owing to leg-length discrepancy of 4 cm. The centre-edge angle (coverage ratio of the acetabulum to the femoral head) was improved from 15º to 33º after a foot lift. She underwent osteotomy and lengthening of the normal contralateral tibia using a Taylor spatial frame. Hip arthroplasty could be avoided as osteoarthritic changes of the hip joint had improved.

Congenital pseudarthrosis of the tibia

Congenital pseudarthrosis of the tibia (CPT) is an uncommon disease with various clinical presentations ranging from simple anterolateral tibial angulation to complete non-union with extensive bone defects. Classifications of radiographic findings include atrophic or hypertrophic pseudarthosis as well as cystic or dystrophic lesions. Although the relationship between CPT and type 1 neurofibromatosis is well known, the exact pathogenesis still remains unclear. The fibrous soft tissue found in the pseudarthosis and the abnormal periosteum are certainly a key to the pathology, possibly due to decreased osteogenic capacities and impaired local vascularization. Treatment of CPT is still challenging in pediatric orthopedics because of bone union difficulties, persistant angulation, joint stiffness and sometimes severe limb length discrepancy sequellae. Numerous treatments based on biological and/or mechanical concepts, surgical or not, have been reported with variable success rates. Vascularized fibular grafts and the Ilizarov technique have greatly transformed the prognosis of CPT. Despite these steps forward, repeated surgical procedures are often necessary to obtain bone union and the risk of amputation is never entirely eliminated. The effectiveness of new treatments (bone morphogenetic protein, bone marrow stromal cell grafts, pulsed electromagnetic fields, induced membrane technique…) still requires to be confirmed. Combining these new techniques with existing treatments may improve the final prognosis of CPT, which nevertheless remains poor.

"4-in-1 osteosynthesis" for atrophic-type congenital pseudarthrosis of the tibia

BACKGROUND

According to the authors' multi-targeted, fibular status-based algorithmic approach using the Ilizarov technique, ankle stabilization by end-to-end osteosynthesis of the fibula is advocated for mild (type B1), "4-in-1 osteosynthesis" in which all 4 proximal and distal segments of the tibia and fibula are placed in 1 healing mass for moderate (type B2), and distal tibiofibular (TF) fusion for severe (type B3) fibular pseudarthrosis in association with atrophic-type congenital pseudarthrosis of the tibia (CPT). This report describes the indications, operative technique, and outcomes of "4-in-1 osteosynthesis" for atrophic-type CPT associated with type B2 fibular pseudarthrosis.

METHODS

Thirteen patients presented with atrophic-type CPT associated with type B2 fibular pseudarthrosis underwent Ilizarov osteosynthesis between 1989 and 2007 for atrophic-type CPT. To validate the efficacy of "4-in-1 osteosynthesis" in these patients, fracture risk and ankle function were compared between 2 groups of type B2 patients, namely, 8 patients (mean age, 6.3 y) who underwent "4-in-1 osteosynthesis" according to our current protocol (Group I), and 5 patients (mean age, 3.2 y) treated by other techniques (3 distal TF fusion, 2 failed end-to-end osteosynthesis) during the learning period (Group II).

RESULTS

No refracture occurred in Group I, whereas refracture occurred in all except 1 in Group II. Ankles were eventually stabilized by distal TF fusion in all patients in Group II. The Kaplan-Meier method revealed a refracture-free cumulative survival rate of 100% in Group I, whereas in Group II, it dropped progressively and reached 60% at 1.8 years and 20% at 2.7 years. No significant difference in ankle function was evident between the 2 groups (american orthopaedic foot and ankle society (AOFAS) score, 89.25 ± 7.25 after 7.4 y of follow-up in Group I, and 84.6 ± 9.53 after 13 y of follow-up in Group II).

CONCLUSIONS

It is imperative that fibular status be evaluated carefully to enable the planning of the most effective, safe, practical treatment. "4-in-1 osteosynthesis," which is primarily considered for bony union with a large cross-sectional area and ankle stabilization, seems to be a better choice for atrophic-type CPT associated with type B2 fibular pseudarthrosis, in which end-to-end osteosynthesis of the fibula often fails.

LEVEL OF EVIDENCE

Level III, Retrospective comparative study.

Disturbed osteoblastic differentiation of fibrous hamartoma cell from congenital pseudarthrosis of the tibia associated with neurofibromatosis type I

BACKGROUND

Fibrous hamartoma is the key pathology of congenital pseudarthrosis of the tibia (CPT), which was shown to have low osteogenicity and high osteoclastogenicity. This study further investigated the mechanism of impaired osteoblastic differentiation of fibrous hamartoma cells.

METHODS

Fibroblast-like cells were obtained from enzymatically dissociated fibrous hamartomas of 11 patients with CPT associated with neurofibromatosis type I (NF1). Periosteal cells were also obtained from the distal tibial periosteum of 3 patients without CPT or NF1 as control. The mRNA levels of Wnt ligands and their canonical receptors, such as Lrp5 and β-catenin, were assayed using reverse transcriptase PCR (RT-PCR). Changes in mRNA expression of osteoblast marker genes by rhBMP2 treatment were assayed using quantitative real time RT-PCR. Changes in mRNA expression of transcription factors specifically involved in osteoblastic differentiation by rhBMP2 treatment was also assayed using quantitative real-time RT-PCR.

RESULTS

Wnt1 and Wnt3a mRNA expression was lower in fibrous hamartoma than in tibial periosteal cells, but their canonical receptors did not show significant difference. Response of osteoblastic marker gene expression to rhBMP2 treatment showed patient-to-patient variability. Col1a1 mRNA expression was up-regulated in most fibrous hamartoma tissues, osteocalcin was up-regulated in a small number of patients, and ALP expression was down-regulated in most fibrous hamartoma tissues. Changes in mRNA expression of the transcription factors in response to rhBMP2 also showed factor-to-factor and patient-to-patient variability. Dlx5 was consistently up-regulated by rhBMP2 treatment in all fibrous hamartoma tissues tested. Msx2 expression was down-regulated by rhBMP2 in most cases but by lesser extent than control tissue. Runx2 expression was up-regulated in 8 out of 18 fibrous hamartoma tissues tested. Osterix expression was up-regulated in 2 and down-regulated in 3 fibrous hamartoma tissues.

CONCLUSIONS

Congenital pseudarthrosis of the tibia appears to be caused by fibrous hamartoma originating from aberrant growth of Nf1 haploinsufficient periosteal cells, which failed in terminal osteoblastic differentiation and arrested at a certain stage of this process. This pathomechanism of CPT should be targeted in the development of novel therapeutic biologic intervention.

Primary osteopathy of vertebrae in a neurofibromatosis type 1 murine model

Neurofibromatosis type 1 (NF1) is a common autosomal dominant genetic disorder caused by mutation of the NF1 tumor suppressor gene. Spinal deformities are common skeletal manifestations in patients with NF1. To date, the mechanism of vertebral abnormalities remains unclear because of the lack of appropriate animal models for the skeletal manifestations of NF1. In the present study, we report a novel murine NF1 model, Nf1(flox/-);Col2.3Cre(+) mice. These mice display short vertebral segments. In addition, a significant reduction in cortical and trabecular bone mass of the vertebrae was observed in Nf1(flox/-);Col2.3Cre(+) mice as measured by dual-energy X-ray absorptiometry (DEXA) and peripheral quantitative computed tomography (pQCT). Peak stress and peak load were also significantly reduced in Nf1(flox/-);Col2.3Cre(+) mice as compared to controls. Furthermore, the lumbar vertebrae showed enlargement of the inter-vertebral canal, a characteristic feature of lumbar vertebrae in NF1 patients. Finally, histologic analysis demonstrated increased numbers of osteoclasts and decreased numbers of osteoblasts in the vertebrae of Nf1(flox/-);Col2.3Cre(+) mice in comparison to controls. In summary, Nf1(flox/-);Col2.3Cre(+) mice demonstrate multiple structural and functional abnormalities in the lumbar vertebrae which recapitulate the dystrophic vertebral changes in NF1 patients. This novel murine model provides a platform to understand the cellular and molecular mechanisms underlying the pathogenesis of spinal deficits in NF1 patients.

Plexiform neurofibroma of the submandibular gland in patient with von Recklinghausen's disease

Plexiform neurofibroma of the submandibular gland is an extremely rare tumor. Herein, we report a case of plexiform neurofibroma in a patient with a von Recklinghausen's disease (NF-1) who presented with a submandibular mass mimicking a submandibular gland tumor. Complete surgical excision provides the best treatment and final diagnosis. A neurofibroma should be considered in the differential diagnosis for submandibular mass.