Does the location of the entry point affect the reduction of proximal humeral fractures? A cadaveric study.

The selection of the correct entry point for stabilisation of long bone fractures and particularly of the humérus with intramedullary nailing is of paramount importance. The insertion of a nail from the correct entry point ensures anatomical alignment of the head and the shaft fragment. However, particularly for the humérus, the literature addressing this issue is obscure. Twenty cadaveric humeri without soft tissue attachment were studied. Two groups were studied: Group A (straight nail) and Group B (angled nail). A fracture of the surgical neck of the humérus was simulated. Then intramedullary nail was inserted through the correct entry hole. Displacement at the fracture site and force to reduce the displacement were measured. The average horizontal displacement was 2.5 ± 2.2 mm in Group A and 1.9 ± 1.1 mm in Group B. The humeral shaft tended to displace medially. The force required to reduce the produced displacement was usually less than 15 N. Anatomical reduction could not be obtained in 3/20 humeri even after applying a force of over 35 N. Our results of an average displacement of 2 mm following nail insertion, supports the significance of the entry point as a cause of loss of reduction at the fracture site post nail insertion. In most cases, anatomical reduction can be corrected with relative small forces, whereas in the rest the correction of the displacement is not feasible even with the application of substantial forces.