Digital Marker Tracing Combined with Center-of-Mass Algorithm in Analyzing Viscoelasticity Characteristic of Lumbosacroiliac Complex

The objective of this study is to analyze stability and viscoelasticity of lunibosacroiliac complex and to provide data to relative biomechanical analysis and clinic pelvic operations. Six cadaveric specimens of the third lumbar vertebra to the proximal 1/3 part of femur were used in present study, fixed on special bench. The specimens had no structural abnormality and all the soft tissues were dissected, reserving the hip joint capsules and the ligaments of the pelvic ring and floor. Markers with black dots against white background were used to mark the key points of the pelvis. Axial loadings from the proximal lumbar were applied by MTS in the gradient of ON to 500 N. Images of the front and lateral views were obtained using two CCD cameras.Using image J software, we calculated relative falling distance of L5, abducent degree of pelvic coronal plane and rotational degree of pelvic vertical plane by measuring the marker's movement. Under a vertical load of 500 N, the average relative falling distance of L5 was (1.157plusmn0.794) mm, the average abducent degree of pelvic coronal plane was (0.370plusmn0.260)deg and the average rotational degree of pelvic vertical plane was (1.051plusmn1.728)deg. Common pelvic specimen has satisfactory stability and shows viscoelastic property of lumbosacroiliac complex by using digital marker tracing method combined with the center-of-mass algorithm.