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Vol 7, No 4, July/August 1999 217 Type 1 neurofibromatosis (NF-1), or von Recklinghausen disease, is a multisystem disease that primarily affects cell growth of neural tissue. It is an autosomal dominant disorder, with approximately 50% of cases due to new mutation. The entity is quite common, affecting 1 in 4,000 individuals, and is one of the most common dominantly inherited gene disorders in humans. In 1990, the gene locus of NF-1 in humans was cloned, and its protein product, neurofibromin, was identified. 1 In 1993, the gene for central neurofibromatosis (NF-2) was cloned, and its protein product, merlin or schwanno- min, was identified. 2,3 Patients with NF-1 may develop Schwann cell tumors called neurofibromas and pigmentation abnormalities. In children with NF-1, complications are associated with both the orthopaedic manifestations of the disease and the treatment thereof. Strategies for their evaluation and management are critical. Neurofibromatosis was first graphically described by Tilesius von Tilenau in 1793. Von Reckling- hausen was the first (in 1882) to associate the origin of this disorder with tumors arising from cells of the nerve sheaths. Historically, NF-1 is well known because of the Òelephant man,Ó Joseph Carey Merrick, who was a medical curiosity in London in the 1880s. 4 His disfiguring deformity of the head, extremity involvement, and vertebral deformities made him a celebrity. More recently, Cohen 5 has speculated that Merrick had Proteus syndrome rather than NF-1. Nevertheless, the interest in his case brought needed attention to NF-1. The fact that Weber, one of the more renowned dermatologists of his time, examined Merrick and made no mention of cafŽ-au-lait spots gives credibility to CohenÕs treatise. Samples of MerrickÕs skin were lost during World War II and are not available for analysis. Type 1 neurofibromatosis can be clearly distinguished from NF-2, which is also an autosomal dominant disorder. The latter occurs much more rarely and is estimated to affect 1 in 40,000 individuals. Characteristically, in NF-2 there are bilateral schwannomas of the vestibular portion of the eighth cranial nerve. Schwannomas of other Dr. Crawford is Professor of Orthopaedics and Pediatrics, Division of Human Genetics, ChildrenÕs Hospital Medical Center, Cincinnati. Dr. Schorry is Assistant Professor of Pediatrics, Division of Human Genetics, ChildrenÕs Hospital Medical Center, Cincinnati. Reprint requests: Dr. Crawford, Division of Human Genetics, ChildrenÕs Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229-3039. Copyright 1999 by the American Academy of Orthopaedic Surgeons. Abstract Type 1 neurofibromatosis (NF-1), also known as von Recklinghausen disease, is one of the most common human single-gene disorders, affecting at least 1 million persons throughout the world. It encompasses a spectrum of multifaceted disorders and may present with a wide range of clinical manifestations, including abnormalities of the skin, nervous tissue, bones, and soft tissues. The condition can be conclusively diagnosed when two of seven criteria established by the National Institutes of Health Consensus Development Conference are met. Most children with NF-1 have no major orthopaedic problems. For those with musculoskeletal involvement, the most important issue is early recognition. Spinal deformity, congenital tibial dysplasia (congenital bowing and pseudarthrosis), and disorders of excessive bone and soft-tissue growth are the three types of musculoskeletal manifestations that require evaluation. Statistics gathered from the Cincinnati ChildrenÕs Hospital Neurofibromatosis Center database show the incidence of spinal deformity in children with NF-1 to be 23.6%; pectus deformity, 4.3%; limb-length inequality, 7.1%; congenital tibial dysplasia, 5.7%; hemihypertrophy, 1.4%; and plexiform neurofibromas, 25%. The orthopaedic complications can be managed, but only rarely are they cured. J Am Acad Orthop Surg 1999;7:217-230 Neurofibromatosis in Children: The Role of the Orthopaedist Alvin H. Crawford, MD, FACS, and Elizabeth K. Schorry, MD peripheral nerves, meningiomas, and ependymomas are also common. Tumors of the eighth cranial nerve are not found in NF-1. The gene for NF-2 has been localized on the long arm of chromosome 22 and cloned. Because NF-2 does not seem to have any musculoskeletal manifestations, it will not be discussed in this article. Approximately 50% of all NF-1 cases are new mutations, which is 100-fold higher than the usual mutation rate for a single locus and may reflect the huge size of the NF-1 locus (estimated at 350,000 base pairs). (Most genes are composed of several tens of thousands of base pairs; the largest known, the gene for Duchenne muscular dystrophy, extends over 2.5 million base pairs.) Prenatal testing is now possible in families with multiple affected gen- erations and in patients with an identifiable mutation. Mutations for NF-1 may be identified in the laboratory with the protein truncation test. This test can be used to detect an abnormal- ly shortened protein product due to gene mutations. Unfortunately, the protein truncation assay can detect only 70% of the NF-1 mutations, making it a less than ideal diagnostic test for NF-1. 6 The manifestations of NF-1 vary from one person to another, but each individual who carries the gene will eventually show some clinical features of the disease, the penetrance for NF-1 being close to 100%. Cloning of the gene has allowed creation of animal models, which may ultimately be used to develop more effective therapy against the disease. The Consensus Development Conference on Neurofibromatosis at the National Institutes of Health in 1987 concluded that the diagnosis of NF-1 could be assigned on the basis of the presence of two or more of the criteria shown in Table 1. 7 These criteria have been shown to be very useful even in young children. Since the consensus panel meeting, various types of learning disabilities and magnetic resonance (MR) imaging abnormalities (espe- cially in children) have also been specifically associated with NF-1. Other disorders of pigmentation, such as McCune-Albright and Leopard syndrome, can be confused with von Recklinghausen neurofibromatosis. Genetic studies have shown that Watson syndrome, but not Noonan syndrome, may be linked to the NF-1 locus. 8,9 Clinical Features Café-au-Lait Spots CafŽ-au-lait spots are hyperpig- mented macules that are usually ovoid and have smooth, well- defined borders (Fig. 1). CafŽ-au- lait spots are present in more than 90% of patients with NF-1. The pigmentation is melanotic in origin and is located both in the basal layer of the epidermis and in the melanocytes of the upper layers. The lesions are usually found in skin areas not exposed to the sun. Crowe et al 10 concluded that an adult who has more than six cafŽ- au-lait spots measuring 1.5 cm or more in diameter should be as- sumed to have NF-1. Whitehouse 11 evaluated 365 children under the age of 5 and concluded that fewer than two cafŽ-au-lait spots is a common and normal phenomenon in children but more than five spots with a diameter of at least 0.5 cm should be considered diagnostic of NF-1. Commonly, an infant or young child with no family history of NF-1 presents with multiple cafŽ- au-lait spots. Unfortunately, the diagnosis of NF-1 cannot be made in the absence of other features. The family should be told that NF-1 is likely to be the diagnosis, as familial cafŽ-au-lait spots are exceedingly rare. Additional criteria are almost always met by the age of 10 years. 12 Cutaneous Neurofibromas Neurofibromas are mixed cell tumors that are rich in Schwann cells but also include fibroblasts, endothe- lial cells, and glandular elements. The primary cell responsible for tumor formation is unknown. The tumor (formerly called fibroma mol- luscum) is usually raised over the skin surface and is slightly bluish. The tumors are generally seen in small numbers in preadolescence but tend to appear more extensively after puberty and pregnancy. 13 Neurofibromatosis in Children Journal of the American Academy of Orthopaedic Surgeons 218 Table 1 Criteria for Diagnosis of Neurofibromatosis, as Established by the NIH Consensus Development Conference 7 More than six cafŽ-au-lait spots, at least 15 mm in greatest diameter in adults and 5 mm in children Two or more neurofibromas of any type or one plexiform neurofibroma Freckling in the axillae or inguinal regions (Crowe sign) Optic glioma Two or more Lisch nodules (iris hamartomas) A distinctive bone lesion, such as sphenoid dysplasia or thinning of the cortex of a long bone, with or without pseudarthrosis A first-degree relative (parent, sibling, or offspring) with NF-1 by the above criteria Plexiform Neurofibroma Plexiform neurofibroma is a very sensitive subcutaneous neurofibroma with a ropy Òbag of wormsÓ feeling. Plexiform neurofibromas are often found underlying an area of cutaneous hyperpigmentation. The pigmentation is purplish with indistinct edges, and the skin lesion is slightly raised. When the pigmentation approaches or crosses the midline of the body, it is likely that the tumor originates from the spinal canal and will be aggressive. A plexiform neurofibroma has the potential to become malignant. Elephantiasis Elephantiasis is another derma- tologic manifestation of the disease. This condition is characterized by large soft-tissue masses with rough, raised, villous skin. Attempts to resect sizable portions of the soft tissue have met with limited success. There is also dysplasia of the underlying bone when the lesions occur in an extremity. 14 Verrucous Hyperplasia Verrucous hyperplasia is an in- frequent and unsightly cutaneous lesion of neurofibromatosis. There is tremendous overgrowth of the skin, with thickening but also a vel- vety soft, papillary quality. Many crevices form in this disorder; these crevices tend to break down easily, and some weeping occurs in the skin folds. The sites often become superficially infected, giving rise to a foul odor. This condition most often develops unilaterally and is one of the most grotesque cutaneous lesions of NF-1. Axillary and Inguinal Freckles The presence of diffuse, small (up to 2 to 3 mm in diameter), hy- perpigmented spots in the axillae and groin regions is helpful in the diagnosis of NF-1. Axillary or inguinal freckling is the second most common feature after cafŽ-au- lait spots to appear in children and is confirmatory of a diagnosis of NF-1. 12 A frequency of 81% by age 6 years has been reported. 15 The recognition of this skin-fold freckling in a young child with multiple cafŽ-au-lait spots will permit an early diagnosis of NF-1. Lisch Nodules Lisch nodules are slightly raised, well-circumscribed hamartomas in the iris. They are present in over 90% of patients with NF-1 who are 6 years of age or older. Some neurofibromatosis centers have reported incidence rates of less than 50% by 5 years old but 90% by adulthood. The lesions are thought to be spe- cific for NF-1. Optic Gliomas Although optic gliomas account for only 2% to 5% of all brain tumors in childhood, as many as 70% of the cases are found in persons with NF-1. In many NF-1 patients, these tumors change little in size over a period of years, but a small percentage may enlarge rapidly, leading to exophthalmos and visual impairment. Severity Type 1 neurofibromatosis presents with various degrees of severity. There seem to be two peaks of severe clinical problems for NF-1 patients: one at 5 to 10 years and the other at 36 to 50 years. At the second peak, 75% of the clinical problems are related to malignancy. 16 For children, the most important element is early recognition. Spinal Deformities Spinal deformities noted to occur in NF-1 include both dystrophic and nondystrophic changes in the vertebral bodies (Fig. 2). The radiographic appearance of nondystrophic deformity consists of wedging, angulation, and rotation similar to that seen in idiopathic deformities. The radiologic appearance of dystrophic changes includes scalloping of the posterior vertebral margins, severe rotation of the apical vertebrae, vertebral wedging, widening of the spinal canal, enlargement of the neural foramina, widened interpediculate distance, defective pedicles, presence of a paraspinal mass, spin- dling of the transverse process, and rotation of the ribs resembling a twisted ribbon (ÒpencilingÓ). 17 Rib penciling is diagnosed when a rib is smaller in diameter than the midportion of the second rib. These changes may be due to intraspinal lesions, such as tumors, meningoceles, and dural ectasia. However, the changes may occur even if the intraspinal contents are entirely normal. In these cases, the dystrophic changes have been explained as a primary bone dysplasia. Dural ectasia, meningoceles, pseudomeningoceles, and Òdumb- bellÓ lesions are all related to the presence of neurofibroma or abnormal pressure phenomena in and about the spinal canal neuraxis. Dural ectasia is a circumferential dilatation of the dural sac. The mechanism by which this occurs has not been defined. The neural elements are not abnormal or enlarged, and the expanded area contains increased cerebrospinal Alvin H. Crawford, MD, FACS, and Elizabeth K. Schorry, MD Vol 7, No 4, July/August 1999 219 Fig. 1 Multiple cafŽ-au-lait spots and cutaneous neurofibromas on the trunk of a patient with NF-1. fluid and a brownish proteinaceous material. The expanding dura erodes the surrounding osseous structures, widening the spinal canal, thinning the laminae, and destabilizing the vertebral elements. The process occasionally results in dislocation of the vertebral column. Its expansion out- ward through the neural foramina causes meningoceles and will give the radiographic dumbbell appearance. Because of spinal canal widening and expansion, there may be tremendous angular deformity and distortion without spinal cord compromise or neurologic deficit. Further destabilization at the costo- vertebral junction has been associated with rib penetration into the spinal canal with neurologic compromise. 18,19 Most often, however, the single dumbbell lesion (visual- ized as enlargement of a single neural foramen on an oblique x-ray film) is caused by a neurofibroma exiting from the spinal canal rather than dural ectasia (Fig. 3). Unrecognized extrapleural thoracic tumors have presented as focal scoliosis. These lesions are usually plexiform neurofibromas and are occasionally visible on plain radiographs. 20 High-volume computed tomographic (CT) myelography or MR imaging should be used in the investigation of all dystrophic curves before initiating treatment. 21 Intraspinal elements may occasionally compromise the cord directly when instrumentation and stabilization are attempted or may cause erosive changes in the bone, pre- venting primary fusion or weakening existing fusion. Care must be taken during surgical exposure to avoid directly entering the spinal canal through the very thin laminae and injuring the spinal cord. The cervical spine in NF-1 patients has not received enough attention and should be evaluated at the initial scoliosis investigation. There may be early evidence of dystrophic changes on lateral radiographs. Cervical abnormalities occur much more frequently when scoliosis or kyphoscoliosis is present in the thoracolumbar region, and the examinerÕs attention may be distracted by the more obvious deformity. The most common cervical abnormality is kyphosis, which in itself is highly suggestive of the disorder. In one study of 56 patients with NF-1, Yong-Hing et al 22 found that 17 had cervical abnormalities. Of these, 7 were asymptomatic, and the rest had either limited motion or pain in the neck. Four had neurologic deficits, which could proba- bly be attributed to cervical instability. Four patients required fusion of the cervical spine. Curtis et al 23 described eight patients with paraplegia and NF-1. In four cases, the paraplegia was due to cervical spine instability or intraspinal disorders in the cervical spine. Anterior dislocation of both the upper and the lower cervical spine has been reported. 24,25 Attention should also be paid to C1 and C2. Isu described three patients with NF-1 who had C1-2 dislocation with neurologic deficit. All improved after decompression or fusion. 17 In none of the patients were there any obvious osseous changes at the C1-C2 level on plain radiographs. Cervical instability sometimes develops after excision of tumors and resection of the laminae and posterior elements. Pro- gressive kyphosis is more common than nonprogressive kyphosis. It is important to obtain cervical spine radiographs of all NF-1 patients who undergo surgery, require endotracheal anesthesia, are placed in halo traction, or present with neck tumors, neck pain, torticollis, or dys- Neurofibromatosis in Children Journal of the American Academy of Orthopaedic Surgeons 220 Fig. 2 Spinal deformities associated with NF-1. A, Nondystrophic-appearing changes in the vertebral body associated with spinal deformities. The appearance is very similar to that of idiopathic scoliosis. B, Myelogram shows widening of the spinal canal and the characteristic short, segmented, sharply angulated deformity associated with neurofibromatosis. A B phagia. Widening of the neural foramina on oblique views may be represented by the dumbbell lesions characteristic of neurofibromas exiting the spinal canal. If there is any suspicion of subluxation, CT and/or MR imaging are appropriate. Scoliosis Scoliosis is the most common osseous defect associated with NF-1. It may vary in severity from mild, nonprogressive forms to severe curvatures. The cause of spinal deformity is unknown, but it may be secondary to osteomalacia, a localized neurofibroma that erodes bone, an endocrine disturbance, or mesodermal dysplasia. The exact prevalence of spinal deformity in NF-1 is unknown. We have reservations about estimating the incidence on the basis of the occurrence in populations in tertiary referral institutions with a primary interest in the disease or in spinal deformity. In a general orthopaedic clinic, 2% of the scoliosis population will have NF-1, whereas in an NF-1 population, perhaps 10% to 30% of patients will have some disorder of the spine. 26 Although both dystrophic and nondystrophic abnormalities are possible, most patients with spinal deformities who are seen in neurofibromatosis clinics have nondystrophic deformities. Functional scoliosis resulting from limb hypertrophy or long-bone dysplasia must be ruled out in patients with NF-1. 27 Preadolescent children with NF-1 should be evaluated for scoliosis, which occurs earlier in children with NF-1. The dystrophic curvature is characterized by short segments, sharp angulation with severe apical rotation and usually less than six spinal segments, vertebral scalloping, spindled ribs or a transverse process, a paravertebral soft-tissue mass, foraminal enlargement, and occasionally thinned defective pedicles. (Not all conditions need be present in any one individual.) These anomalies may predispose to subluxation or dislocation of a vertebral body. The dystrophic type has a tendency to progress to a severe deformity. 28,29 Some centers have noted a higher incidence of thoracic lordosis in young patients with dystrophic curves 30 (Figs. 2, B; 4). Others have noted a higher incidence of primary kyphosis in patients with dystrophic curvatures and have found it useful to divide this group on the basis of whether the deformity is angular or secondary to severe vertebral rotation. 29,31 A trend to a higher incidence of left convex dor- sal curvatures has also been noted. Left convex spinal deformities are known for their association with spinal axis tumors. 32 Nondystrophic curvature is quite similar to the idiopathic curvature seen in adolescents and appears to usually involve eight to ten spinal segments (Fig 2, A). It is most often convex to the right; however, this is not consistent. The majority of patients with spinal deformities in the NF-1 population have the nondystrophic type. Dystrophic curvatures of less than 20 degrees should be observed for progression at 6-month inter- vals. For curvatures greater than 20 to 40 degrees, a posterior spinal fusion with segmental spinal instrumentation is recommended. 33 Be- cause of the potential for unabated progression, modulation, and pseud- Alvin H. Crawford, MD, FACS, and Elizabeth K. Schorry, MD Vol 7, No 4, July/August 1999 221 Fig. 3 A, Axial computed tomographic (CT) image shows erosive defects and foraminal and spinal canal widening due to a dumbbell lesion. B, Axial CT image obtained at another level in the same patient shows that soft-tissue instability has allowed subluxation of one rib head into the spinal canal. C, Dumbbell tumor was removed from the neural foramen at the time of surgery. The dumbbell appearance refers to the conscription of the neurofibroma that occurs at the neural foramen, where the lesion exits the spinal canal. A B C arthrosis in patients with dystrophic curvatures, surgery is recommended for progressive deformities of lesser magnitude. 34 This is in contradis- tinction to the situation in patients with idiopathic scoliosis, in whom surgical stabilization of curvatures measuring less than 40 degrees is usually inappropriate. Dystrophic curves greater than 50 degrees should be treated with anterior and posterior fusion. Although thoracotomy is generally necessary, we have recently used video-assisted thoracoscopy to perform anterior release, costoplasty, and intervertebral fusion. 35 Oblique x-ray views should be taken every 6 months to rule out pseudarthrosis. Brace treatment alone has not been effective in the management of dystrophic deformities. For the very young child, early fusion will result in minimal stunting of growth. Nondystrophic curvatures of less than 20 degrees should be observed, those measuring 20 to 35 degrees should be braced, and those over 35 degrees should be treated with fusion. Close observation and follow- up are essential because of the tendency of these curves to modulate to dystrophic curves. 33 Funasaki et al 29 have documented the development of certain dystrophic features over time. It is possible that some patients are simply too young at presentation to show the typical manifestations of vertebral dysplasia. Patients with nondystrophic deformity have a higher incidence of pseudarthrosis after attempts at fusion and surgical stabilization than patients with idiopathic scoliosis. 33,36 If indicated, the fusion mass can be evaluated with technetium-99m bone scanning or tomography. Future refinements of MR imaging may allow identification of pseudarthrosis. 37 These tests may not be conclusive, and exploration and graft reinforcement may be necessary. Complications of spinal surgery include bleeding from plexiform venous channels, dural leaks, and paraplegia. Kyphoscoliosis The kyphoscoliosis seen in NF-1 is distinguished by acute sagittal- plane angulation. The term is used in those cases in which the scoliosis is accompanied by kyphosis greater than 50 degrees (Fig. 5). The vertebral bodies may be so severely deformed as to cause them to be confused with congenital anomalies. Occasionally, weakening of the spinal stabilizers (e.g., facets, pedicles, and ligaments) by dural ectasia with meningocele formation gives rise to kyphosis with subluxation and dislocation of the spine. 24 Even with severe ÒhairpinÓ angulation, the neurologic status may remain normal, and the spinal cord is protected because of the widened spinal canal. Bracing is recommended for patients with kyphosis measuring less than 50 degrees. Traction may be dangerous when performed on rigid deformities because it increases ten- sion on the midapical spinal cord, which may cause neurologic dam- age. Dystrophic rigid kyphotic curvatures greater than 50 degrees can rarely be stabilized with posterior fusion alone and are better treated by combined anterior-posterior segmental instrumentation. 26,32 Once a curvature exceeds 70 degrees, indefi- nite bracing may be required even after anterior-posterior spinal surgery. Because of the association of paraplegia with kyphosis, there has been a tendency to perform laminectomy. When neurologic changes of cord compression secondary to kyphosis are present, a trial of halo traction is warranted. The myelopathy will often improve, at which time anterior and posterior fusion with halo immobilization may be performed. If the myelopathy does not improve, anterior decompression followed by anterior-posterior fusion is indicated. Laminectomy alone for kyphotic cord compression is absolutely contraindicated for two reasons. First, the cord compression is usually anterior, and resection of the posterior element predisposes the spine to instability. Second, resection removes valuable bone stock required for fusion. Spinal fusion should always be performed after laminectomy. Lordoscoliosis The condition in which the kyphotic curve is physiologically normal but the sagittal-plane contour measures less than normal magnitude has been recognized as a sepa- rate entity in a small percentage of patients. 26,30,38,39 The prognostic implications of this deformity have not been clarified. It is well known that lordoscoliosis is associated with mitral valve prolapse and decreased pulmonary function. 40,41 Lordoscoliosis appears more commonly in patients with dystrophic Neurofibromatosis in Children Journal of the American Academy of Orthopaedic Surgeons 222 Fig. 4 Severe thoracic lordosis. deformities with dural ectasia causing considerable thinning of the posterior elements. Surgical plan- ning should include instrumentation and fusion well above the lor- dotic area because of the tendency to junctional kyphosis at the cervico- thoracic junction. Spondylolisthesis Spondylolisthesis is a very rare finding, most often associated with pathologic luxation of the lumbar vertebrae because of elongation and erosion of the pedicles or pars by lumbosacral foraminal neurofibroma or dural ectasia. It is important to evaluate the entire spine, including the sacral segments, in every patient. Anterior and posterior stabilization is recommended for progressive deformity. 39 Failure to recognize intraspinal lesions in patients with neurofibromatosis who undergo manipula- tion and instrumentation of the spine may result in neurologic compromise. Preoperative radiog- raphy, CT, or MR imaging is essential for patients with dystrophic vertebral elements and curvatures requiring instrumentation and fusion. Most patients with a signif- icant deformity have no preoperative neurologic deficit. It is the sur- geonÕs responsibility to stabilize the spine in the most expedient, safe, and permanent method without causing neurologic injury. Congenital Tibial Dysplasia Congenital tibial dysplasia (CTD) was first described by Hatzoecher in 1708. ÒCongenital pseudarthrosisÓ is a misnomer; CTD is the preferred term. It may present initially as either anterolateral bowing or a frank fracture. Congenital tibial dysplasia is rare, occurring in 1 per 140,000 live-born children. In contrast, its incidence is 1% to 2% in patients with NF-1. The deformity may present before the other common manifestations, such as cafŽ-au-lait spots. It is usually evident within the first year of life, with a fracture not uncommonly occurring by the age of 2 to 2 1 Ú2 years. Posteromedial congenital bowing, or Òkyphosco- liosis tibia,Ó is a benign condition associated with occasional limb- length inequality. Tibial bowing associated with skin dimples, bilateral presentation, ring constrictions, and foot deformities is rarely associated with NF-1. The early appearance of callus and subperiosteal new bone on the posteromedial concavity of an antero- laterally bowed tibia and the lack of involvement of the fibula are diagnostic of a spontaneously resolving benign condition. 42 The management of CTD associated with NF-1 is frustrating, and complications are frequent. Frac- ture and refracture are common after treatment and are often more frequent when the residual angular deformity is excessive. Stiffness of the ankle joint invariably occurs because of the need for rigid immobilization during treatment. Be- cause of the possibility of nonunion or pseudarthrosis after osteotomy, an increase in angular deformity should not be addressed surgically if the limb has not fractured and can be braced. Limb-length inequality may occur because of dis- use atrophy as well as deficiency of growth potential of the distal tibial physis. Most patients with CTD and angular deformity have a valgus deformity of the ankle. The valgus is caused by a deficiency in the fibular lateral buttress due to either fracture and/or pseudarthrosis in the lower part of the fibula or a sloping distal tibial epiphysis. 43 Surgical treatment of CTD does not appear to be particularly successful; the results of prefracture brace treatment are more encouraging. We have recently performed epiphyseal stapling and percutaneous- screw epiphysiodesis of the distal medial tibia to correct ankle valgus. Efforts have been made to classify the diverse forms of CTD by either Alvin H. Crawford, MD, FACS, and Elizabeth K. Schorry, MD Vol 7, No 4, July/August 1999 223 Fig. 5 This child presented with severe kyphoscoliosis. He had undergone three attempts at posterior spinal fusion, all of which were unsuccessful. The kyphosis was in excess of 100 degrees. radiographic or pathologic criteria to aid in determining prognosis and selecting appropriate treatment alternatives. Unfortunately, incon- sistency of treatment and results is the rule. 44-46 There are two basic types of CTD, nondysplastic and dysplastic (Table 2, Fig. 6). The fibula may be primarily involved by pseudarthrosis inde- pendently or may be angulated and/or pseudarthrotic with the tibia. However, its management will not be discussed here. Treatment Bracing Bracing can be both preventive and therapeutic (Fig. 7). Once the diagnosis of NF-1 is suspected and anterolateral bowing has been con- firmed, the prewalker child should be placed in an ankle-foot orthosis. When the child starts to stand, a change should be made to a poly- propylene knee-ankle-foot orthosis. The Òdrop-lockÓ type of knee-joint hinge is added as the child gets older, which allows sitting with the knee flexed. Orthotic support should be maintained until maturity whether or not surgical osteosynthesis has been achieved, because of the disastrous consequences of fracture and refracture. An articulated above-knee ankle brace is recommended arbi- trarily after 10 years of age if the stabilizing instrumentation has not been extended across the ankle. Pulsating Electromagnetic Fields Treatment with a pulsating electromagnetic field is advocated for some patients with progressive CTD. The source may be externalÑ the ÒclamshellÓ device over an ankle-foot orthosis or an internal unit implanted in the soft tissue around the area of pseudarthrosis, usually in conjunction with an autogenous bone graft. The effectiveness of these forms of treatment remains highly controversial. 47,48 Surgical Bone Grafting Autogenous bone is placed into the excised pseudarthrosis site. An intramedullary rod is placed from the proximal tibia across the pseudarthrosis site, incorporating the graft and extending down through the ankle across the talus and into the calcaneus. The Williams technique of transankle stabilization with a Rush rod has provided the best surgical results in our center. Residual ankle stiffness, growth disturbance to the distal tibia, ankle valgus, and lateral plantar nerve entrapment have been documented as complications of the procedure. 49 The possibility of fractur- ing at the tip of the nail during its distal migration or during removal or reinsertion is a further concern with this procedure. Rod elongation and/or replacement is required as the limb grows, and continuous bracing is necessary. 50-52 Bypass prophylactic bone grafting as a form of management as well Neurofibromatosis in Children Journal of the American Academy of Orthopaedic Surgeons 224 Table 2 Basic Types of Congenital Tibial Dysplasia Nondysplastic (type I) Anterolateral bowing with increased bone density Sclerosis of the medullary canal Possibility of conversion to dysplastic type after osteotomy to correct the angulation Dysplastic (type II) Subtype A: Anterolateral bowing with failure of tubularization Subtype B: Anterolateral bowing with cystic prefracture or canal enlargement from previous fracture Subtype C: Frank pseudarthrosis and atrophy with Òsucked candyÓ narrowing of the ends of the two fragments Fig. 6 Classification of congenital tibial dysplasia. Type I is characterized by anterior lateral bowing with increased cortical density and a narrow but normal medullary canal; type IIA, by anterior lateral bowing with failure of tubularization and a widened medullary canal; type IIB, by anterior lateral bowing with a cystic lesion before fracture or canal enlargement from a previous fracture; type IIC, by frank pseudarthrosis and bone atrophy with Òsucked candyÓ narrowing of the ends of the two fragments. Type I Type IIA Type IIB Type IIC as after fracture is used less frequently. 53 Vascularized Autogenous Graft The most commonly used vascularized graft is the contralateral fibula (Fig. 8), followed by the iliac crest and rib. The graft is removed extraperiosteally and placed into the pseudarthrosis site. The blood vessels are then anastomosed to those normally supplying the tibia. It is necessary to stabilize the grafted segment. It is most important to fuse or transfix the distal tibia and fibula of the donor leg to prevent proximal migration of the fibula and ankle valgus. 52,54 Problems associated with vascularized grafts include failure to unite, further pseudarthrosis, progressive angular deformity, failure to achieve normal length, valgus ankle instability, and disability of the donor limb. 18 Coleman and Coleman 50 have recommended using the ipsilateral fibula transferred with a vascular pedicle. Their rationale is that two abnormal legs are created with a contralateral graft, whereas the long-term effects of loss of the fibula on the ankle joint of the normal leg are unknown. This procedure is recommended only after conven- tional treatment has failed. It should be noted that only five cases with relatively short follow-up (average, 2.0 years) were reported. Compression and Distraction Histiogenesis Compression and distraction histiogenesis of bone and soft tissue by the Ilizarov method pro- vides many theoretical advantages in the treatment of problems associated with CTD. This method allows the surgeon to address limb-length inequality, angular deformity, fibular nonunion, proximal fibular migration, ankle valgus, and foot contractures. The technique encompasses various methods for treating the pseudarthrosis, including open reduc- tion, resection and shortening, compression/distraction, resection and bone transport, and invagina- tion of one end of the affected bone in the other. The Ilizarov method results in a high rate of initial union; however, the rate of refracture is extremely high. 43 Another disadvantage of the Ilizarov method has to do with its external location, which is less well tolerated by pediatric patients. The myriad complications with the procedure include joint stiffness, cartilage necrosis, cystic bone lesions, dorsiflexion ankle contrac- ture with calcaneovalgus deformity, pin-track infection, loosening, pin breakage, nerve injury, and com- partment syndrome. 43 The pin- holes also may create stress risers after union. Considerable preoperative plan- ning is essential to identify solu- tions for every possible problem. Boero et al 46 recently concluded that patients who were aged 5 years or older at operation had better results with this technique. Resection of the pseudarthrotic Alvin H. Crawford, MD, FACS, and Elizabeth K. Schorry, MD Vol 7, No 4, July/August 1999 225 A B Fig. 7 Congenital tibial dysplasia treated with chronic bracing after a fracture. A, Radiograph obtained after early union of a distal tibial fracture. An ankle-foot orthosis was used at that time. When the patient started walking, a change was made to a knee- ankle-foot orthosis. B, Radiograph taken 9 years later shows complete union of previous fracture. stumps, followed by short-term compression with corticotomy or epiphyseal distraction to correct limb-length discrepancy, gave better results than other combinations. This technique avoids risking injury to the contralateral leg, and other treatment methods are not excluded. Most authors who use the Ilizarov technique advocate continuing orthotic management after successful treatment or until skeletal maturity is achieved. Amputation The logic of performing multiple surgical procedures after failure of three attempts at bone union is questionable. If the ultimate outcome will be a short, scarred limb with a fibrotic ankle, amputation is a viable alternative. The weight-bearing surface of the foot should be maintained by means of a Boyd-Syme procedure rather than a midleg transbone amputation, which predisposes the child to subsequent surgeries for bony stump overgrowth. The resultant length after the Boyd-Syme procedure adds biomechanical stability for prosthetic wear. Contrary to previous reports, removing the foot and then placing the limb in a prosthesis that allows continuous compression forces across the pseudarthrosis has not resulted in osseous union of the pseudarthrosis. 55 The new ÒSeattle footÓ and ÒrunnerÕs footÓ have made chil- drenÕs prosthetics much more functional, and team sports like soccer are not out of the question after amputation. Long-term Bracing Regardless of the procedure used, some form of bracing is required for all patients until skeletal maturity, because of the marked propensity for refracture and re- currence of pseudarthrosis. The diminished quality of life that is the outcome of numerous unsuccessful operative procedures makes chronic bracing a reasonable alternative. Treatment of Pseudarthrosis Pseudarthrosis of other bones, including the fibula (Fig. 9), ulna, os pubis, and clavicle, is not as frequent as pseudarthrosis of the tibia. Nevertheless, the problems of achieving synostosis are similar. Fortunately, except for the fibula, most of these bones are not weight bearing and as a result pseudarthrosis is easier to manage; however, there is a consistent tendency to de- lay of synostosis after pseudarthrosis. Pseudarthrosis may develop spontaneously, after fracture, or after osteotomy of the involved bone. The treatment and complications associated with treatment are similar to those for pseudarthrosis of the tibia. Treatment of Bone-Growth Disorders Three disorders of bone growth are segmental hypertrophy, cystic lesions, and subperiosteal bone growth and proliferation (Fig. 10). Overgrowth of an extremity is not a rare complication of NF-1 and may be related to changes in the soft tissues, such as hemangiomatosis, lymphangiomatosis, elephantiasis, and beaded plexiform neurofibromas. 56 The zones of overgrowth in the bone and soft tissues are usually unilateral, involving the extremities or the head and neck. The osseous changes characteristically cause the bone to elongate with wavy irregu- larity or thickening of the cortex. Macrodactyly is commonly seen in NF-1, with disproportionate enlargement of either the toes or the fingers. Treatment is extremely em- pirical and individualized. Some combination of epiphysiodesis, debulking, and neurofibroma resection is recommended. 57,58 The incidence of neoplasia associated with segmental hypertrophy is higher than that of other lesions. Neurofibromatosis in Children Journal of the American Academy of Orthopaedic Surgeons 226 A B Fig. 8 Images of a child who underwent vascularized fibular bone grafting. Previous attempts at bone grafting and implanted electromagnetic bone stimulation were unsuccessful. The stimulator from the previous surgical procedure was not removed. A, Radiograph shows construct of vascularized fibular bone graft. B, Successful union of vascularized graft. Fig. 9 Anteroposterior (A) and lateral (B) views of the leg of a child with congenital fibular dysplasia and neurofibromatosis. Note valgus deformity of the ankle joint shown on anteroposterior view. A B [...]... Philadelphia, and a National Cancer Institute trial of phenylacetate for plexiform neurofibromas It is expected that additional medications, including drugs that act by blocking the RAS pathway, will be available for clinical trials in the near future It is important to remember that approximately 65% of all patients with NF-1 have only mild or moderate involvement throughout their lifetime Fewer than . credibility to CohenÕs treatise. Samples of MerrickÕs skin were lost during World War II and are not available for analysis. Type 1 neurofibromatosis can be clearly distinguished from NF-2, which is. expected that additional medications, including drugs that act by blocking the RAS pathway, will be available for clinical trials in the near future. It is important to remember that approximately

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