Sacrum: fracture

Etiology

• Direct trauma following the horse falling backward, backing into a hard object like a wall, or collisions from behind like road traffic collisions.
• Injudicious use of tail rope.

Pathophysiology

• Impact on sacrum and caudal vertebrae →
  • If cranial sacrum, protected by the tuber sacrale which means that sacroiliac subluxation Pelvis: trauma - sacroiliac is more likely than fracture at this level which tends to lead to chronic hindlimb lameness. If fracture does occur it is most likely at S2.
  • Tail head acts as lever on the caudal sacrum and first two coccygeal vertebrae, predisposing it to injury in this region.

• Sacrum contains the S4, S5 and caudal cord segments, plus the termination of the cauda equina - peripheral nerves to perineum as well as sacral and lumbar nerves contributing to the sciatic and gluteal nerves.
• Fracture through S2 results initially in damage to the cauda equina from S2 caudally.
• Sacrococcygeal luxation, initially compresses the coccygeal roots only.
• Subsequent instability of fractures and soft tissue swelling may lead to involvement of nerve roots and spinal segments cranial to S2.

Adult

• Sacrum consists of five fused sacral vertebrae and it functions as one unit.
• Injury concentrated on caudal part of sacrum.
• Fractures may be incomplete or complete.

Foals

• Sacral vertebrae are separate and can operate independently.
• Injury may affect individual vertebra at any point.
• Range of clinical signs is greater in foals.