Anatomical changes in vertebra in dystrophic scoliosis due to neurofibromatosis and its implications on surgical safety.

Detailed radiological analysis by multimodality imaging. To document anatomical changes jeopardizing instrumentation safety in Neurofibromatosis deformity correction surgeries. The apical and 3 adjacent vertebral segments above and below amounting to 70 segments in 10 NF scoliosis were studied by radiographs, CT and MRI. The changes in lamina, pedicle and vertebral body that could jeopardize pedicle screw and sublaminar wire placement were documented and changes were appropriately classified. Extensive anatomical changes were noted. These changes were more severe at the apex and independent of the curve severity. Both laminae were normal in only 36 (Type 1), rest had either gross asymmetry in length and shape (Type 2; 21) or also in sloping (Type 3; 13). Of the 140 pedicles, normal pedicles were found only in 48 (Type 1); while they were divergent (Type 2; 4) or abnormally elongated with only thinning (Type 3a; 26); or with sclerosis (3b; 34); or very curved and wavy (3c; 23) and even fractured or indistinct (Type 4; 5). It was notable that 92 of the 140 pedicles were unsuitable for pedicle screws. A unique phenomenon of body drift was identified in 29 segments which could jeopardize screw placement and rib dislocation into the canal was found in 18 segments. Gross anatomical changes jeopardizing both sublaminar wire strength and trajectory of pedicle screws were common in NF and independent of curve severity. Therefore, detailed preoperative assessment and planning by a 3D CT are essential.