Anatomical and radiological observations concerning ossification of the sacrotuberous ligament: is there a relation to spinal diffuse idiopathic skeletal hyperostosis (DISH)?

In a collection of 101 anatomical preparations of the human pelvis, ossification of the sacrotuberous ligament was found in 8 cases. In 7 of these, the ossification showed a characteristic intraligamentous morphology, with a broad-based origin at the ischial tuberosity and tapering off craniomedially. The length varied between 1.1 and 7.2 cm. The surface of the bone formations appeared fasciculated, except in one case which had a wax-like flowing bone formation lying upon the sacrotuberous ligament. Careful anatomical and radiological examination of the spine, the ulnae, the calcanei and the iliac crests in these 8 cases, revealed in only one case any findings (spurs at the olecranon) that could be attributed to extraspinal manifestations of diffuse idiopathic skeletal hyperostosis (DISH). Indeed, in no case were the most widely accepted diagnostic criteria of DISH, the spinal alterations, seen. We therefore suggest that ossification of the sacrotuberous ligament is an autonomous finding and not a good indicator of the presence of spinal DISH.