Correlation of the Postoperative Mechanical Properties of Femoral IM Nails to the Fracture Management Process

Abstract

A biomechanical study of twenty-six Grosse-Kempf interlocking intramedullary nails was carried out aiming to assess the effect of the femoral fracture characteristics and the fracture management process on the postoperative mechanical properties of the nails. The nails were retrieved from recovered patients. Full medical records were maintained. They included fracture topology, fracture type, locking type, patient mobilization time, callus formation time, time until the nail has been retrieved, patient's gender and age. The nails have been tested on a specially built four point bending jig on a 10 kN loading testing machine after establishing a specific testing protocol. The ultimate load was recorded and the nail bending stiffness was calculated. Additionally, three intact nails have been tested for comparative purposes. Two nails exhibited visible angle deformation beyond their designed curvature before testing, in the order of 1° to 3°. Only four nails exhibited ultimate load and bending stiffness values below the 90 % of the average and nominal values. Two of them were the pre-distorted specimens and one corresponded to a case of a non-union where a revision took place. There was no evident explanation for the fourth nail. Finally, the mechanical testing results were correlated to the medical records data. It was shown that the mechanical properties of the nails had hardly been affected by any of the parameters included in the medical records. This indicates that more flexible nails could be employed in the future for the treatment of femoral fractures, especially if it facilitates insertion technique.