Motion Capture Analysis of Sacroiliac Joint Motion After Manipulation

The Sacroiliac (SI) joint is a diarthrodial joint with the contradictory biomechanical function of transmitting compressive loads from the lumbar spine to the lower extremity while maintaining a nutating motion in the pelvis.

Recent studies identify the Sacroiliac (SI) joints as a significant source of pain in patients with chronic low back pain, contributing up to 27%. Recent studies have demonstrated that historical and physical examination findings and radiological imaging alone are insufficient to diagnose SI joint pain.

The purpose of this study is to examine the effects of manipulation on sacroiliac joint motion using a Polhemus motion capture system. The Absolute angular deviation of sacroiliac joint motion will be assessed during the normal gait cycle with the Polhemus Liberty motion capture system. Six sensors will be attached to specific anatomical landmarks of the pelvis which recorded motion characteristics while walking on a treadmill at 5 mph. The subjects then receive a HVLA manipulation to the SI joint and were retested at the same treadmill speed.

The Motion capture system tracks objects at a speed of 240 updates per second on all sensors simultaneously. The latency of data sampling is less than 4ms; 240 x 60 sec x 8 Sensors totaling 115,200 data points per minute. The system generates and tracks electromagnetic fields (EMF), computes position and orientation of sensors in an X, Y, and Z coordinate system while interfacing with a computer. The EMF source contains electromagnetic coils that emit a magnetic field. The source is the system's reference frame for sensor measurements. The sensor contains electromagnetic coils (accelerometers) that detect the position and orientation of the magnetic fields emitted by the EMF source.