Primary Thoracolumbar Scoliosis in Pinealectomized Chickens

Abstract

Study Design. This study examines the gross anatomic changes in the chicken spine after pinealectomy and was undertaken because initial observation suggested that the pattern of curve development appears to be different from that reported in the literature. Objective. To characterize the spinal deformity in chickens after pinealectomy. Summary of Background Data. The most common curve pattern seen after pinealectomy in chickens is said to be thoracic curves with structural changes and rotation. This is based largely on radiographic observations and forms the basis of the claim that chicken and human adolescent idiopathic scoliosis are similar. Method. Thirty-five chickens were divided into 2 groups, a pinealectomy group (n = 25) and a control group with no surgery performed (n = 10). The spines were harvested at 3 months of age and examined visually, by radiographs and computed tomography scans. Results. Thirteen out of 25 (52%) of the pinealectomized chickens developed scoliosis. In contrast to previous studies, all the curves were located at the thoraco-lumbar junction with the apex at either T7 or L1. Structural changes including apical vertebral wedging, lordosis (mean of 14.3°), and rotation (mean of 14°) were seen in all cases. Pelvic wing deformity was seen in all cases and significantly contributed to the posterior rotational hump. Conclusion. The primary curve in these chickens is at the thoracolumbar junction. Previous reports of curve pattern based on radiographic findings would not have identified these as the thoracolumbar junction is obscured by the bony pelvis and heavy musculature. The finding of pelvic wing deformity has not been previously reported, and raises the question as to whether these curves are secondary to asymmetric muscle pull.