Fractures and Dislocations of the Pelvis
Sacral Fractures Usually from fall or direct trauma; 2 types: Horizontal(transverse) fxs.- m.c. type; m.c. levels are S3 and S4 – AP view shows disruption of foramina – Lateral shows disruption of anterior cortex and possible angulation or displaced distal fragment Vertical fractures- result from indirect pelvic trauma – AP may show asymmetry of foramina – Not visible on lateral
Coccygeal Fractures Usually transversely oriented Best seen on lateral view – May show angulation or anterior displacement of distal fragment
Fractures of the Ilium Iliac wing fxs.- AKA Duverney fx.; splitting of iliac wing from direct lateral trauma Malgaine's fx.- double injury; ipsilateral double vertical fracture of the superior pubic ramus and ischiopubic ramus, with fracture or dislocation of the sacroiliac joint herapy.com/searchResults. aspx?searchStr=iliac+wing+ fractures&rootterm=iliac+ wing+fractures&rootID=49 853&searchType=1&searc hSource=1
Fractures of the Ilium Acetabular fractures: Resulting acetabular injury depends on position of femur at the moment of impact -4 types - Posterior rim fracture (dashboard fracture)- occurs after a blow to the knee while the leg is flexed and adducted (1/3 of acetabular fxs.) -Simple posterior column fx- uncommon -Central acetabular fx. (explosion fx.)- m.c. acetabular fx; divides innominate bone into superior and inferior halves -Simple anterior column fx- on AP, there is loss of continuity of the iliopubic line
Fractures of the Ilium Avulsion fractures- more common in adolescents at apophyses before fusion of the involved growth centers; more common in athletes – ASIS- avulsed by sartorius muscle – AIIS- avulsed by avulsed by rectus femoris muscle
Pubis and Ischium Fractures Straddle fx.- m.c. type of unstable pelvis fx. – Double vertical fracture that involves both superior pubic rami and ischiopubic junctions bilaterally – Fragments may rupture the bladder
Pubis and Ischium Fractures Avulsion fractures: – Symphysis pubis- avulsion by major adductor muscles at superior or inferior pubic rami near pubic articulation – Ischial tuberosity (rider’s bone)- avulsion by hamstring attachment Frequently bilateral Fragment may show overgrowth over time and get mistaken for osteo- chondroma
Pelvic Dislocations Sprung pelvis- represents complete separation of the symphysis pubis and one or both of the SI joints (pelvis looks like an open book) – Severe pelvic basin visceral damage may occur
Pubic Diastasis Represents shearing separation of the pubic articulation Normal distance b/t pubic bones should not exceed 8mm in non-pregnant adults or 10mm in children Often present with unilateral dislocation of SI joint
References Yochum, T.R. (2005) Yochum and Rowe’s Essentials of Skeletal Radiology, Third Edition. Lippincott, Williams and Wilkins: Baltimore.