A new method to reconstruct the spatial structure of human proximal femur and establishment of the finite element model / 生物医学工程学杂志

In current study of femoral head necrosis and femoral neck fractures, more attentions has been paid to relationship between the femoral head trabecular bone within the spatial structure and its biomechanics. In this connection, PMMA (polymethyl methacrylate), special square iron, dental base acrylic resin liquid and powder were used to embed and fix human dry femur. Then, M618 Lie Axle Rectangle Desk Plane Grinding Machine was applied to grind the femur specimen, and then air blower clean, two-dimensional cross section image was obtained by using scanner. With Mimics software reconstruction, a three-dimensional model of spatial structure of trabecular bone was obtained, and the trabecular bone three-dimensional parameters were calculated. The authors obtained clear three-dimensional model of trabecular bone, reconstructed the real anatomic morphology of proximal femur. This is a good method to research into the interior structure of femur and to provide the foundation for the three-dimensional finite element analysis.

Biomechanical evaluation of dynamic hip screw with bone cement augmentation in normal bone / 中国组织工程研究

BACKGROUND: Dynamic hip screw (DHS) is a standard internal fixation for intertrochanteric fracture, whereas the patient combined with osteoporosis, cut-out incidence of lag screw is common. The articles in China and abroad indicate bone cement augmentation of DHS to achieve firm fixation. As for normal bone, no reports is published that whether bone cement augmentation is effective.OBJECTIVE: To investigate the biomechanics of DHS with bone cement augmentation for the fixation of intertrochanteric fracture specimen that has a normal bone density.DESIGN, TIME AND SETTING: Bilateral contrast observation study of the same sample was performed in the Laboratory of Biomechanics, Hebei Orthopaedic Research Institute (Shijiazhuang, Hebei Province, China) between March and April In 2005.MATERIALS: Bilateral upper femora from the embalmed male cadaver were provided by Anatomy Department of Hebei Medical University (China). X-ray scan results proved the absence of tuberculosis, anatomical deformity and tumor.METHODS: Twenty-four matched pairs of the upper femora (48 sides) were used to make the specimens of the intertrochanteric fracture of type A2. The right femur specimens were fixed with DHS augmented by bone cement, as the augmentation group (The screw track of femoral neck was expended by curette, and the femoral head facing upwards were injected with 2mL low viscosity bone cement. Then lag screw was wrested to keep the position unchanged till the bone cement coagulated. Placing barrel, compressing through tighten tail screw, and cortical screw fixing side-plate were. followed). And the left femur specimen was fixed with DHS conventional fixation, as the control group. The bending and torsional tests were performed in the two groups.MAIN OUTCOME MEASURES: The maximum load and the maximum torque in the two groupsRESULTS: The maximum load and the maximum torque were (3852.1602±143.6031) N and (15.5+2.6) Nm in the augmentation group, and (3702.9667±133.8601) N and (14.7±3.4) Nm in the control group. There was no significant difference in the biomechanical effects between the two groups (P>0.05).CONCLUSION: The augmenting fixation with bone cement for intertrochanteric fracture specimen has no significant effect on the strength of DHS fixation or on the overall stability of the fractured bone in normal bone density.