• P Schandelmaier, O Farouk, C Krettek, N Reimers, J Mannss, and H Tscherne.
• Trauma Department, Hannover Medical School, Carl Neuberg Str 1, 30623, Hannover, Germany. peter@schandelmaier.de
• Injury. 2000 Jul 1; 31 (6): 437-43.

AbstractToday there is a variety of different interlocking intramedullary nail designs available for the femur. We compared different nail types in the bone implant complex (BIC) of four unreamed solid nails and a slotted reamed nail with simulated comminuted mid shaft fractures to see if there are major differences in stiffness for axial load, bending and torsion. The fractures were simulated by a 2 cm defect osteotomy in paired human cadaver femora. Each bone was tested intact in a universal testing machine, osteotomy and osteosynthesis were performed, and the BIC was tested. Relative stiffness was calculated. In torque testing the unslotted solid nail showed significantly more stiffness (0.6-1.8 Nm/degrees) compared to the slotted nail (0.2 Nm/degrees). Compared to intact bone (6.9 Nm/degrees), both groups of nails were significantly less stiff (relative stiffness 2-20%). In axial load and bending testing the large diameter unreamed nail showed significantly higher stiffness (32-68%). This study shows that stiffness of bone implant complex in interlocking femoral nails is more dependent on nail profile than on the pressfit of nails in the medullary canal.

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