Elastic and viscoelastic properties of the human pubic symphysis joint: effects of lateral impact joint loading.

The human pelvis is susceptible to severe injury in vehicle side impacts owing to its close proximity to the intruding door and unnatural loading through the greater trochanter. Whereas fractures of the pelvic bones are diagnosed with routine radiographs (x-rays) and computerized tomography (CT scans), non-displaced damage to the soft tissues of pubic symphysis joints may go undetected. If present, trauma-induced joint laxity may cause pelvic instability, which has been associated with pelvic pain in non-traumatic cases. In this study, mechanical properties of cadaveric pubic symphysis joints from twelve normal and eight laterally impacted pelves were compared. Axial stiffness and creep responses of these isolated symphyses were measured in tension and compression (perpendicular to the joint). Bending stiffness was determined in four primary directions followed by a tension-to-failure test. Loading rate and direction correlated significantly (p<0.05) with stiffness and tensile strength of the unimpacted joints, more so than donor age or gender. The impacted joints had significantly lower stiffness in tension (p <0.04), compression (p<0.003), and posterior bending (p<0.03), and more creep under a compressive step load (p<0.008) than the unimpacted specimens. Tensile strength was reduced following impact, however, not significantly. We concluded that the symphysis joints from the impacted pelves had greater laxity, which may correlate with post-traumatic pelvic pain in some motor vehicle crash occupants.

Acetabular fracture patterns: associations with motor vehicle crash information.

BACKGROUND: Motor vehicle crashes are the most common cause of acetabular fractures, which have been associated with significant morbidity and mortality. METHODS: To date, medical and collision information has been collected on 83 acetabular fracture patients treated at the University of Alabama at Birmingham's Level I trauma center. The fractures were grouped according to the Judet-Letournel classification scheme and investigated for correlation with age, sex, vehicle type, impact direction, and seat-belt use. RESULTS: The database included 41 women and 42 men with a combined average age of 32.8 years. Femoral shaft axis loading fractures correlated significantly with male sex, trucks, and frontal impacts. Greater trochanter loading fractures occurred statistically more frequently in side impacts. Women received a significant higher percentage of off-axis loading fractures, which were associated more in angled frontal impacts. CONCLUSION: Acetabular fracture type strongly correlated with impact direction, supporting the fracture mechanisms proposed by Judet and Letournel.