BONE-MINERAL CONTENT AND FIXATION STRENGTH OF FEMORAL-NECK FRACTURES - A CADAVER STUDY

We measured the bone mineral content (BMC) of 21 human femoral autopsy specimens using Radiographic Attenuation Technique (RAT). The specime ns were then tested for stiffness in a material-testing machine. Osteo synthesis was performed after medial femoral neck osteotomy, using 1 o f 3 different pinning methods: 2 hook pins (LIH), 2 cannulated screws (Uppsala), and 3 cannulated screws (CHP). The specimens were allocated to each method by grouping them in triplets with similar BMC. Cyclic loading at 500-1000 N and 1 Hz was performed during 50 minutes. The am ount of axial compression during loading was measured. Finally, loadin g to failure was done and post-fixation stiffness and ultimate compres sion strength recorded. With one exception, all cases failed where the BMC was less than 0.4 g/cm2. No differences between the methods of os teosynthesis were found. The fixation strength was mostly dependent on the strength of the bone, i.e., the degree of osteoporosis.