TTU Home COE Home Mechanical Engineering Orthopaedic Biomechanics Laboratory Projects Biomechanical Analysis of a New Fixation Device for Disrupted Pubic Symphysis

Biomechanical analysis of a new fixation device for disrupted pubic symphysis

The pubic symphysis is the midline cartilaginous joint uniting the superior rami of the left and right pubic bones. It is located anterior to the urinary bladder and superior to the external genitalia; for females it is above the vulva and for males it is above penis. In males, the suspensory ligament of the penis attaches to the pubic symphysis [1]. The pubic symphysis is essential in the stability of the pelvic ring.  Without an intact pubic symphysis, the pelvic ring is compromised and small forces can cause bones or other ligaments to fail.  The purpose of this project is to test standard pelvic fixation techniques through cyclic loading, and to test experimental pelvic fixation methods through cyclic loading.

In this project the pubic symphysis is secured with plates and screws and the sacroiliac joint is secured with either a sacral bar or sacroiliac screws. The purpose is to demonstrate the exact pattern of failure with each fixation method and the best method of pelvic fixation in this injury pattern. Testing is performed on models demonstrating fixation with either two hole (4.5 mm) dynamic compression plate on the superior portion of the pubic symphysis, four hole (3.5 mm or 4.5 mm) dynamic compression plate on the superior portion of the pubic symphysis, four hole recon plate in similar placement as the previous case, or 90/90 plating with four hole 4.5mm dynamic compression plates. All models are  tested with fixation of the sacroiliac joint with either sacroiliac bar or sacroiliac screws. Cyclic testing is conducted through a standard number of cycles to demonstrate six weeks in the recovery process.

Next a new fixation method of the pelvis is developed that will allow for a more physiologic pattern of movement during healing and decrease the incidence of hardware failure and therefore decrease the morbidity associated with injury.

[1] http://en.wikipedia.org/wiki/Pubic_symphysis