Abstract:

Objective　To construct the model of the sacroiliac joints (SIJ) displacement and prelimilarily explore the biomechanical characteristics of the sacroiliac complex(SIC) injury.   Methods　Six frozen pelvis taken from six adult male cadavers were examined and fixed on the Material Testing System (MTS). Six markers were fixed to pot the pelvis in order to measure the displacement of the SIJ. The pelvis were then subjected to dynamic compressive loading at a rate of approximately 2 m/s using the servo-hydraulic MTS. The maximum impact stress and response time were measured when the SIJ was completely disrupted, at the same time, we measured the 3-dimensional displacement using a 3-dimensional video system (Gait Analasis System) at the point of joint failure, furthermore, anatomic characteristics of the disrupted SIC were explored.  Results　The SIJ displacement model was constructed succeed. The average maximum impact stress was about 4.05±0.42kN and average response time 22.99±1.89ms. The maximum vertical displacement was about 8.15±1.34mm. The SIC injury always combined with fracture of ilium or sacrum. Each concerned ligament had different injury characteristics.   Conclusions　For the vertically unstable pelvic fracture, some regularity and characteristics can be summaried and considered during the clinical diagnosis and treatment. Under the condition of the vertical displacement beyond 0.9cm, all the ligaments concerned with the SIC maybe destroy.

Key words: Pelvic fracture!Vertically instability!Sacroiliac complex!Biomechanics!Dynamic impact