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Posterior Sacrococcygeal Ligaments

ligamenta sacrococcygea posteriora

The posterior sacrococcygeal complex consists of a superficial and a deep ligament. The deep posterior sacrococcygeal ligament corresponds to the posterior longitudinal ligament, connecting the posterior surfaces of the sacral and coccygeal vertebral bodies. The superficial posterior sacrococcygeal ligament corresponds to the ligamentum flavum, connecting the posterior aspect of the sacral hiatus to the posterior surface of the coccyx.

Region: Pelvis & Hip

Biomechanics

Function & Actions

Restrain forward flexion and distraction of the coccyx from the sacrum, protect the sacral hiatus opening, and provide the posterior ligamentous envelope of the sacrococcygeal joint.

Clinical Relevance

Clinical Notes

The superficial posterior sacrococcygeal ligament overlies the sacral hiatus, through which the caudal epidural space is accessed. Palpation of the sacral cornua and the soft tissue cover of the hiatus is the first step in caudal epidural block technique. Calcification or thickening of the posterior ligament complex can obliterate the sacral hiatus, making caudal block technically impossible without imaging guidance. Coccydynia involves the sacrococcygeal joint and associated ligaments.

Pathology

Common Injuries & Conditions

Coccydynia

Trauma, childbirth, or repetitive pressure on the coccyx disrupts the sacrococcygeal ligaments and joint, producing focal coccygeal pain worsened by sitting, defecation, and rising from a chair, managed with cushions, injection, and rarely coccygectomy.

Caudal Epidural Block Failure

Calcification of the posterior sacrococcygeal ligament occluding the sacral hiatus prevents successful caudal epidural needle insertion by tactile palpation alone, requiring ultrasound guidance to identify the patent portion of the hiatus.