Ossification of the Sacrotuberous Ligaments

Ossification of the sacrotuberous ligaments has a caudocranial direction of growth. On frontal radiographs, pencil-like opacities project over the obturator foramina and extend cephalad and medially towards the sacrum. On cross-sectional imaging, the ossifications have a ventrodorsal flattened appearance and extend cephalad from the ischial tuberosities medially and posteriorly.

It has been suggested that ossification of the sacrotuberous ligaments is a good indicator of diffuse idiopathic skeletal hyperostosis (DISH), although others have contested this association. For what it's worth, our patient, a 50-year-old man, had no manifestations of DISH in the spine. Ossification of the sacrotuberous ligaments has also been associated with pudendal nerve entrapment.

Atherosclerotic calcifications can mimic the appearance of ossified sacrotuberous ligaments, but recognition of the course and tubular nature of these calcifications should be sufficient to avoid confusion.

References

• Arora J, Mehta V, Suri RK, Rath G. Unilateral partial ossification of sacrotuberous ligament: anatomico-radiological evaluation and clinical implications. Rom J Morphol Embryol. 2009;50(3):505-8.
• Prescher A, Bohndorf K. Anatomical and radiological observations concerning ossification of the sacrotuberous ligament: is there a relation to spinal diffuse idiopathic skeletal hyperostosis (DISH)? Skeletal Radiol. 1993 Nov;22(8):581-5.
• Robert R, Prat-Pradal D, Labat JJ, Bensignor M, Raoul S, Rebai R, Leborgne J. Anatomic basis of chronic perineal pain: role of the pudendal nerve. Surg Radiol Anat. 1998;20(2):93-8.