Pelvic asymmetry in children with neuromuscular scoliosis: a computed tomography-based 3D analysis

Pelvic fixation in pediatric neuromuscular patients with scoliosis is performed when significant pelvic obliquity is present. Instrumentation to the pelvis can be technically demanding and challenging, often associated with a high complication rate, prolonged operative time, increased radiation exposure, and increased intraoperative bleeding. The high complexity of the pelvic instrumentation technique, particularly in severe cases, led us to develop computed tomography (CT)-based 3D in a series of 53 consecutive neuromuscular patients. This analysis aimed to improve the understanding of pelvic asymmetry and preoperatively simulate pelvic instrumentation.

A CT-based 3D analysis of all pelvises was performed using Mimics software (version 21), segmenting them for analysis in all three planes. We proceeded with the simulation of pelvic instrumentation with iliac screws, obtaining the angle values and corresponding orientations in the three planes for each screw. A total of 53 CT scans were analyzed, corresponding to 36 patients with myelodysplasia and 17 with neuromuscular disorders.

Pelvic asymmetry was observed in 88.6% (47 CT scans) of the patients. This asymmetry indicated that the weight-bearing hemipelvis underwent anatomical changes compared to the contralateral hemipelvis, including opening or closing of the pelvis relative to the sacroiliac joint, pivoting of the hemipelvis in a cephalocaudal or caudocephalic direction, and shortening of the innominate line.

The shape of the weight-bearing hemipelvis is closely related to pelvic asymmetry. A distinct pattern was identified, characterized by cephalic or caudal pivoting, greater prominence of the iliac crest, increased distance from the sciatic spine to the coccyx, and shortening of the innominate line. This finding is relevant for surgical planning and pelvic fixation.

IV.