Biomechanical analysis comparing titanium elastic nails with locked plating in two simulated pediatric femur fracture models

Scott E Porter, George R Booker, Douglas E Parsell, Mark D Weber, George V Russell, James Woodall, Michael Wagner, Thomas Neubauer
Journal of Pediatric Orthopedics 2012, 32 (6): 587-93

BACKGROUND: Increasing attention is being paid to the influences that the body habitus and weight of the pediatric patient impose upon the fixation methods for femur fractures. Of the widely accepted treatment options, little biomechanical or clinical data exist comparing flexible intramedullary nailing and locked plating. The aim of this study was to compare the mechanical stability of unstable pediatric diaphyseal femur fractures fixed with titanium flexible intramedullary nails or a titanium locking plate using a synthetic femur model.

METHODS: Fracture stabilization was carried out with either 4.0-mm titanium elastic nails or 16-hole 4.5-mm narrow titanium locking compression plates. Axial and rotational testing of each specimen was performed. The axial loading rate was 0.20 mm/s. The torsional loading rate was 0.1 degrees rotation per second. The axial compressive modulus was defined as the compressive stress divided by the compressive strain. The rotational stiffness was defined as the torque moment applied to the femoral head divided by the resulting rotational displacement (in radians). The yield point or load to failure of the simulated fracture constructs was recorded for each specimen.

RESULTS: The modulus for comminuted fractures measured during the application of axial compression was 0.657 GPa for plate constructs and 0.326 GPa for elastic nail constructs (P=0.021). The modulus for oblique fractures during axial loading treated with plate fixation or titanium elastic nails was 1.63 and 0.466 GPa, respectively (P<0.0001). The yield point for comminuted fractures occurred at an axial load of 2304.7 N (SD ± 315.77) for plate constructs and 383.6 N (SD ± 139.2) for elastic nail constructs (P<0.001). For oblique fractures, the yield load occurred at 3111.9 N (SD ± 821.9) for plate constructs and at 1367.0 N (SD ± 98.9) for elastic nail constructs (P<0.0001).

CONCLUSIONS: Locked plating provides a biomechanically more stable construct than elastic intramedullary nailing. Its use as part of the technique of indirect reduction and submuscular plating remain a viable alternative in the treatment of length-unstable pediatric femur fracture patterns.

CLINICAL RELEVANCE: : Provide biomechanical evidence supporting the use of plating techniques in the pediatric femur fracture population.

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