BACKGROUND: Intramedullary nails and angle-fixed plates have recently been used in proximal humerus fractures. Rigid implants might be associated with an increased risk of failure in osteoporotic conditions. METHODS: Unstable fractures of the surgical neck were created in 24 pairs of human humeri. The biomechanical properties of four implants were analysed. These were a nail with conventional interlocking (PHN-K), a nail with spiral blade interlocking (PHN-S), the T-plate, and an internal fixator with elastic screw properties (reference). The specimens were subjected to axial loading and torque. Stiffness, plastic deformity, and load to failure were assessed. RESULTS: The PHN-S was stiffer than the internal fixator. The PHN-K and T-plate were stiffer only during torque. Less subsidence was observed for the PHN-S. This implant failed at higher loads than the other implants. CONCLUSIONS: The PHN-S offers biomechanical advantages in unstable fractures of the surgical neck of the humerus. Elastic implant properties, however, are disadvantageous.
BACKGROUND: Intramedullary nails and angle-fixed plates have recently been used in proximal humerus fractures. Rigid implants might be associated with an increased risk of failure in osteoporotic conditions. METHODS: Unstable fractures of the surgical neck were created in 24 pairs of human humeri. The biomechanical properties of four implants were analysed. These were a nail with conventional interlocking (PHN-K), a nail with spiral blade interlocking (PHN-S), the T-plate, and an internal fixator with elastic screw properties (reference). The specimens were subjected to axial loading and torque. Stiffness, plastic deformity, and load to failure were assessed. RESULTS: The PHN-S was stiffer than the internal fixator. The PHN-K and T-plate were stiffer only during torque. Less subsidence was observed for the PHN-S. This implant failed at higher loads than the other implants. CONCLUSIONS: The PHN-S offers biomechanical advantages in unstable fractures of the surgical neck of the humerus. Elastic implant properties, however, are disadvantageous.
Authors: Christian Spross; Andreas Platz; Matthias Erschbamer; Thomas Lattmann; Michael Dietrich Journal: Clin Orthop Relat Res Date: 2011-12-13 Impact factor: 4.176