Stable ring injuries do not compromise vertical and horizontal stability of the pelvis.
The following types exists:
• Avulsion fractures
• Transverse iliac fractures
• Transverse sacrum fractures inferior to the SI joint
Avulsion fractures are caused by strong muscle pull in adolescent athletes.
Avulsions may occur depending on the athletes activity and the most common are:
- ASIS - Anterior superior iliac spine (Sartorius muscle)
- AIIS - Anterior inferior iliac spine (Rectus femoris muscle)
- Tuber ossis ischi (Hamstring muscles)
The dislocation is always caudal in the direction of muscle pull.
Transverse iliac fractures
Transverse iliac fractures are caused by direct blow to the iliac wing.
The fracture dislocation of the anterior part is anterior caudal due the pull of the rectus sartorius muscle.
The pelvic crest is often undisplaced as it is stabilized by the strong muscle envelope.
Transverse sacrum fractures inferior to the SI joint
Transverse sacral fractures are mostly caused by direct blow with the dislocation of the distal part anterior.
In these fractures, care should be taken to diagnose even discrete neurological deficits.