neurofibromatosis type-1 ( nf-1 ) is a multisystem , autosomal dominant disorder of peripheral nerves affecting nearly 1/3000 individuals worldwide.1 it was first described by a german pathologist , friedrich daniel von recklinghausen . inherited or spontaneous mutation of the neurofibromin gene located on chromosome 17 is responsible for this diverse disorder . common skeletal manifestations of nf-1 include spinal deformities , congenital tibial dysplasia ( congenital bowing and pseudarthrosis ) , sphenoidal dysplasia and cystic lesions in bones . pathological fracture of the acetabulum with anterior dislocation of hip secondary to osseous involvement of the acetabulum , femoral head , and pubic rami has never been documented in a case of nf-1 . a 16-year - old boy presented with the complaints of pain in the left hip associated with the inability to bear weight following a trivial fall . on examination , the affected limb was 1.5 cm short , abducted and externally rotated . on general examination , patient had 8 caf au lait spots over the body , bilateral axillary freckles and multiple palpable neurofibromas in the subcutaneous tissues of forearm , thighs and back [ figure 1 ] . patient met three out of seven criteria described for the diagnosis of nf-1 [ table 1].2 plain radiograph and computed tomography scan of pelvis revealed an ill - defined lytic lesion causing pathological fracture - dislocation of the left hip [ figure 2 ] . magnetic resonance imaging ( mri ) showed additional soft tissue involvement and joint effusion [ figure 3 ] . ultrasound guided fine - needle aspiration cytology showed scanty cellularity with round to oval cells having minimal pleomorphism ; hyperchromatic nucleus and moderate cytoplasm with spindle cells and osteoblasts . clinical photograph showing skin lesions - caf au lait spots ( black arrows ) and axillary freckling ( white arrow ) criteria for diagnosis of nf-1 ( at least 2 or more features ) preoperative radiograph anteroposterior view ( a ) and computed tomography scan ( b ) of pelvis showing an ill - defined lytic lesion destroying anterior column of acetabulum , pubic rami and part of the femoral head coronal ( a ) and axial ( b ) sections of magnetic resonance imaging of pelvis showing expansile lytic lesion of acetabulum and pubic rami with soft tissue involvement and joint effusion a wide local excision followed by arthrodesis of the joint was planned . considering the extent of bony and soft tissue involvement , we used a modification of the ilioinguinal and iliofemoral approach to have a wide exposure . we used the conventional ilioinguinal incision and combined it with femoral part of the iliofemoral incision [ figure 4a ] . on exposing the pelvis , anatomy was distorted . the deformed femur head and acetabulum with deficient pubic rami there was extensive soft tissue involvement adjacent to the acetabulum and lower part of the ilium . the entire acetabulum with 2 - 3 cm clear margin of the ilium was resected along with the abnormal soft tissue . iliofemoral arthrodesis was done using a 14 hole stainless steel dynamic compression plate [ figures 4c  d , and 5 ] . intraoperative photographs showing ( a ) skin incision ( b ) deformed femoral head ( c ) 14 hole dcp ( d ) iliofemoral arthrodesis postoperative radiograph after tumor resection and iliofemoral arthrodesis histopathology revealed dense collagenous tissue cores with spindle cells having blunt nuclei with minimal atypia and no mitosis or necrosis [ figure 6a ] . on immunohistochemistry , cells were s-100 positive and of neural origin [ figure 6b ] . partial weight bearing was allowed at 6 weeks and full weight bearing at 10 weeks . at 1-year followup , the patient was comfortable , pain free , able to ambulate unassisted , stand on one limb , sit and climb stairs without any difficulty [ figure 7 ] . ( a ) histopathological photomicrograph showing dense collagenous tissue cores and spindle cells with blunt nuclei . ( b ) immunohistochemistry showing neural marker s-100 positivity clinical photographs showing functional outcome at 1-year followup type 1 neurofibromatosis or von recklinghausen disease , is a multisystem disorder that primarily affects the cell growth of neural tissue and characterized by involvement of skin , peripheral nerves , subcutaneous tissue , eyes , and skeletal system . although involvement of the musculoskeletal system is common , there have been only a few cases of subluxation / dislocation of hip in patients with nf [ table 3].34567891011121314 on reviewing the literature , the etiology of hip instability leading to pathological subluxation / dislocation in patients with nf-1 can be classified as local and remote . most of the cases are secondary to local ( intra and peri - articular ) neurofibromas , which can result in mass effect , bony erosions ( ilium , acetabulum , and femoral neck ) , acetabular dysplasia , narrowing of the femoral neck , coxa valga , increased femoral neck offset , capsuloligamentous laxity , and synovial membrane proliferation.3458101113 remote causes of hip instability include intra spinal neurofibromas / schwannomas leading to motor deficit ( hip abductor weakness ) or sensory deficit ( charcot 's neuropathic arthropathy ) , limb length discrepancies secondary to hemi - hypertrophy of lower limb and abnormal biomechanical alteration in the spinopelvic alignment due to scoliosis.6791011 endo et al . described anterior subluxation of hip secondary to decreased femoral head coverage resulting from decreased lumbosacral lordosis and posterior pelvic inclination following scoliosis correction.11 until date , there has been no case of nf-1 reported in the literature with pathological fracture of the acetabulum with anterior dislocation of hip attributable to a neurofibroma involving the acetabulum , pubic rami and femoral head . orthopedic manifestations of nf-1 comprehensive literature review on published cases of hip dislocation / subluxation in nf-1 the various treatment options described for pathological hip dislocations in nf-1 include closed reduction , open reduction , shelf operation with fascia lata tenorraphy , rotational acetabular osteotomy with femoral varus osteotomy , girdle stone resection , total hip replacement with the trochanteric distalisation.791114 the rate of re dislocation is very high in most of the cases , subsequently requiring a secondary surgical procedure for stabilization . since only a handful of cases have been described in the literature , it is difficult to comment upon the best line of management . in our case , arthrodesis was the best possible option since the bone stock after tumor resection was so inadequate that none of the above mentioned procedures could be tried . moreover , the fear of redislocation , which might necessitate repeated surgeries , was negated . a combination of ilioinguinal and iliofemoral approach was employed to have a better exposure of the hip joint . the neurofibromatous tumors associated with nf-1 are usually benign ; however , there is a 2 - 5% chance of malignant transformation , especially with plexiform neurofibromas.15 plexiform neurofibromas are diffuse , poorly defined nerve sheath tumors arising from multiple nerve fascicles and surrounding tissues . they are more prone for hemorrhage , dysfunction , pain , disfigurement , and malignant transformation.16 there was no clinical or radiological evidence of recurrence or malignant transformation in our patient at 1-year followup . subtle clinical signs such as skin patches , axillary freckling , and subcutaneous neurofibromas can be easily missed . orthopedic surgeons must be aware about the various management options available and tailor them as per the needs of their patient . iliofemoral arthrodesis offered a good functional outcome with improved quality of life in our case .
skeletal neurofibromatosis ( nf ) commonly manifests as scoliosis and tibial dysplasias . 
 nf affecting the pelvic girdle is extremely rare . 
 pathological fracture of the acetabulum leading to anterior hip dislocation in a patient with nf-1 has never been reported in the literature . 
 the paper presents the clinical symptomatology , the course of management and the successful outcome of such a rare case of nf-1 . 
 histopathological and immunohistochemistry studies showing abundant spindle cells , which are s-100 positive and of neural origin are the classical hallmarks of neurofibromatous lesions . 
 tumor resection and iliofemoral arthrodesis can be considered as a valid option in young patients with pathological fracture dislocation of the acetabulum .