The effect of different pin configurations on cyclic stability in pediatric proximal humerus fracture fixation: A Sawbones model study

Composite synthetic models of the human femur have recently become commercially available as substitutes for cadaveric specimens. Their quick diffusion was justified by the advantages they offer as a substitute for real femurs. The present investigation concentrated on an extensive experimental validation of the mechanical behaviour of the whole bone composite model, compared to human fresh-frozen and dried-rehydrated specimens for different loading conditions. First, the viscoelastic behaviour of the models was investigated under simulated single leg stance loading, showing that the little time dependent phenomena observed tend to extinguish within a few minutes of the load application. The behaviour under axial loading was then studied by comparing the vertical displacement of the head as well as the axial strains, by application of a parametric descriptive model of the strain distribution. Finally, a four point bending test and a torsional test were performed to characterize the whole bone stiffness of the femur. In all these tests, the composite femurs were shown to fall well within the range for cadaveric specimens, with no significant differences being detected between the synthetic femurs and the two groups of cadaveric femurs. Moreover, the interfemur variability for the composite femurs was 20-200 times lower than that for the cadaveric specimens, thus allowing smaller differences to be characterized as significant using the same simple size, if the composite femurs are employed.

This review brings together a complex and extensive literature to address the question of whether it is possible to distinguish human from nonhuman bone using the histological appearance of cortical bone. The mammalian species included are rat, hare, badger, racoon dog, cat, dog, pig, cow, goat, sheep, deer, horse, water buffalo, bear, nonhuman primates, and human and are therefore not exhaustive, but cover those mammals that may contribute to a North American or Eurasian forensic assemblage. The review has demonstrated that differentiation of human from certain nonhuman species is possible, including small mammals exhibiting Haversian bone tissue and large mammals exhibiting plexiform bone tissue. Pig, cow, goat, sheep, horse, and water buffalo exhibit both plexiform and Haversian bone tissue and where only Haversian bone tissue exists in bone fragments, differentiation of these species from humans is not possible. Other primate Haversian bone tissue is also not distinguishable from humans. Where differentiation using Haversian bone tissue is undertaken, both the general microstructural appearance and measurements of histological structures should be applied. Haversian system diameter and Haversian canal diameter are the most optimal and diagnostic measurements to use. Haversian system density may be usefully applied to provide an upper and lower limit for humans.

We report our experience of elastic stable intramedullary nailing (ESIN) of severely displaced proximal humeral fracture Type III and IV according to Neer in children. Thirty-five children (mean age 12.7 years) with 19 Salter-Harris Type II epiphyseal fractures and 16 children with metaphyseal fractures of the proximal humerus were treated with ESIN by one-nail or two-nail-technique. There were the following complications: two perforations of the nail at the head of the humerus with loss of position, one loss of position without nail perforation, one misplacement of a nail, one revision due to haematoma and two difficult removals of metal. For follow-up examinations after 26 months the children were classified by use of the Constant-Murley score. On average they gained 99 points. All children were able to resume their sporting activities as before. For the treatment of displaced proximal humeral fractures in children more than 10 years old the retrograde ESIN represents a safe minimal invasive surgical procedure.