Biomechanics of femoral interlocking nails.
Today 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.
Schandelmaier
P
P
Trauma Department, Hannover Medical School, Carl Neuberg Str 1, 30623, Hannover, Germany. peter@schandelmaier.de
Farouk
O
O
Krettek
C
C
Reimers
N
N
Mannss
J
J
Tscherne
H
H
D000328:Adult; D001696:Biomechanical Phenomena; D001858:Bone Nails; D002102:Cadaver; D018483:Diaphyses; D005264:Femoral Fractures / Q000503:physiopathology*; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation*; D006801:Humans; D008875:Middle Aged