Rapid application fracture fixators - an evaluation of mechanical performance

OBJECTIVE: This study evaluates the mechanical performance of the Pinless and Centrafix fixators for rapid application to tibial fractures in a disaster or battlefield scenario. DESIGN: Comparative study based on measurements made in the laboratory. BACKGROUND: The Pinless and Centrafix fixators may be considered for rapid application to stabilise fractures in emergency conditions without the aid of electrical equipment such as power drills for bone screw insertion or image intensifiers to facilitate bone alignment. METHODS: Stiffnesses, maximum service loads and fatigue strengths of the fixators were measured in the orientations of loading that correspond to walking 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 (torsional shear), 0.4 N/ degrees (coronal plane bending), 4 N/ degrees (sagittal plane 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 (axial). CONCLUSIONS: The stiffness and strength of both rapid application fixators in simulated walking was judged to be low, and additionally the stiffness and strength of the Centrafix in simulated stretcher-bearing was judged to be low. RELEVANCE: The Pinless is not recommended for weight-bearing subjects with unstable fractures. The Centrafix is not recommended for stretcher-bearing or weight-bearing with unstable fractures.