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

Abstract

Aim of the study:Neurofibromatosis type 1 (NF-1) is associated with the development of scoliosis or kyphoscoliosis. The deformity is rapidly progressive in the presence of dystrophic changes producing bone erosion. Vertebral subluxation or dislocation can occur in children with highly dystrophic kyphoscoliosis and carries an increased risk of paralysis. There is no standardised treatment for this extreme deformity with very few patients currently reported in the literature.Methods:Retrospective review of a patient with NF-1 who developed a dystrophic upper thoracic kyphoscoliosis with segmental displacement of T2 on T3.Results:We report a patient with NF-1 who presented at 8.9 years with a progressive upper thoracic kyphoscoliosis. At 18.8 years, the deformity had deteriorated to scoliosis 65° and kyphosis 78° with fixed segmental rotatory dislocation at T2-T3. He underwent posterior cervico-thoracic fusion with concave pedicle screw/hook/rod instrumentation and iliac crest bone. Minimum correction was achieved due to curve rigidity and inability to reduce the T2/T3 displacement by halo-femoral traction. At 7 months, an elective posterior re-grafting procedure was performed followed by anterior fusion with rib strut grafts between T2-T6 through a midline sternotomy. The patient is now 3.5 years after anterior surgery and remains neurologically intact with stable residual deformity and computed tomographic evidence of circumferential fusion. He has no back pain and resumed non-contact physical activities.Conclusions:Patients with NF-1 can develop dystrophic kyphoscoliosis with segmental spinal subluxation/dislocation. Circumferential fusion is a technically challenging procedure which often requires a multi-disciplinary surgical team but produces satisfactory clinical outcome preventing paraplegia.

Spinal Manifestations of Neurofibromatosis: An Update

“…Erosion, primary mesodermal dysplasia, and osteomalacia are the most important suggested reasons for bone deformities. Different studies have reported varying prevalence rates for scoliosis in patients afflicted with NF1-from 2% to 71% [4,[41][42][43][44].…”

“…Dystrophic: usually presents itself with kyphoscoliosis in the thoracic region of the vertebrae [43]. However, this is not the first sign of this disorder to make itself seen and dystrophic curves are usually visible in radiographies after the age of 3 [32].…”

“…This is always caused by erosion which in turn may be caused by neurogenic tumors like meningocele [48]. Some of the other changes seen in the dystrophic type are severe rotation of the apical vertebra, defective pedicles, widening of the spinal canal or the intervertebral foramina, sharpening of the vertebral margins, portion of the second rib, spindling appearance of the transverse process, or a paravertebral mass [29,38,43,46].…”

“…These changes are supposed to be as a result of the presence of intraspinal neurofibromas, primary dysplasia, pseudomeningoceles, and dural ectasia that erode the surrounding bony structures and cause primary bone dysplasia [38,49] which is recognizable in the normal graphs of the spinal column. In many cases, dystrophic scoliosis is accompanied by kyphosis which manifests as kyphoscoliosis, its manifestation is obviously linked with the progress of the deformity [43,50]. Dystrophic deformities can normally be observed in the thoracic and lumbar areas [49,50].…”

“…However, cases have been reported involving this type of deformity manifesting itself as kyphoscoliosis in the cervical region [48,49]. There have also been reports claiming rotatory dislocations as an accompanying complication that might be observed alongside scoliosis and kyphosis in patients [43,49,50]. Typical dysplastic changes evident on plain radiographs in patients with NF1 are presented in Table 2.…”