BACKGROUND: Crossed k-wire osteosynthesis is a widely used procedure for displaced supracondylar humerus fractures in children, but the rate of secondary displacements is up to 31%. Alternative techniques including casts, elastic stable intramedullary nailing, and the fixateur extern, have been used, but there are no biomechanical data comparing these methods. We developed a biomechanical model to compare four osteosynthesis techniques for stabilizing supracondylar humerus fractures in children. METHODS: An osteotomy to simulate a fracture was made in a total of 32 adult cadaver humeri. The pseudofractures were then stabilized by crossed k-wires, elastic nailing, a fixateur extern with either k-wires, or Schanz screws. We measured the stiffness values in flexion and extension and torsion with static loading. The movements in cyclic loading were chosen to resemble the mechanism described in the development of a clinical cubitus varus. FINDINGS: No significant differences were found with static loading. With cyclic loading all methods showed an irreversible torsional deformation less than 20 degrees . Crossed k-wires and elastic nailing showed significantly lower reversible torsional deformation than the external fixateurs. INTERPRETATION: Our biomechanical data reveal that the crossed k-wires have the highest stiffness and lowest loss of reduction under cyclic loading. The external fixators proved to be good alternatives.
BACKGROUND: Crossed k-wire osteosynthesis is a widely used procedure for displaced supracondylar humerus fractures in children, but the rate of secondary displacements is up to 31%. Alternative techniques including casts, elastic stable intramedullary nailing, and the fixateur extern, have been used, but there are no biomechanical data comparing these methods. We developed a biomechanical model to compare four osteosynthesis techniques for stabilizing supracondylar humerus fractures in children. METHODS: An osteotomy to simulate a fracture was made in a total of 32 adult cadaver humeri. The pseudofractures were then stabilized by crossed k-wires, elastic nailing, a fixateur extern with either k-wires, or Schanz screws. We measured the stiffness values in flexion and extension and torsion with static loading. The movements in cyclic loading were chosen to resemble the mechanism described in the development of a clinical cubitus varus. FINDINGS: No significant differences were found with static loading. With cyclic loading all methods showed an irreversible torsional deformation less than 20 degrees . Crossed k-wires and elastic nailing showed significantly lower reversible torsional deformation than the external fixateurs. INTERPRETATION: Our biomechanical data reveal that the crossed k-wires have the highest stiffness and lowest loss of reduction under cyclic loading. The external fixators proved to be good alternatives.
Authors: Robert Eberl; Christian Eder; Elisabeth Smolle; Annelie M Weinberg; Michael E Hoellwarth; Georg Singer Journal: Acta Orthop Date: 2011-10 Impact factor: 3.717