Rapid application fracture fixators - an evaluation of mechanical performance

Objective. This study evaluates the mechanical performance of the Pinless a nd Centrafix fixators for rapid application to tibial fractures in a disast er or battlefield scenario. Design. Comparative study based on measurements made in the laboratory. Background The Pinless and Centrafix fixators may be considered for rapid a pplication to stabilise fractures in emergency conditions without the aid o f electrical equipment such as power drills for bone screw insertion or ima ge intensifiers to facilitate bone alignment. Methods. Stiffnesses, maximum service loads and fatigue strengths of the fi xators were measured in the orientations of loading that correspond to walk ing and stretcher-bearing. These properties were compared with measurements on three conventional fixators, the AO, Shearer and Triax. Results. The Centrafix stiffnesses were 31 N/mm (axial), 1 N/degrees (torsi onal shear), 0.4 N/degrees (coronal plane bending), 4 N/degrees (sagittal p lane bending) and 11 N/mm (transverse shear) and strengths were 95 N (axial ) and 1.9 Nm (bending). Corresponding Pinless stiffnesses were 43 N/mm, 0.7 N/degrees. 0.3 N/degrees 8 N/degrees and 50 N/mm, and strength was 55 N (a xial). Conclusions. The stiffness and strength of both rapid application fixators in simulated walking was judged to be low, and additionally the stiffness a nd strength of the Centrafix in simulated stretcher-bearing was judged to b e low.