FAILURE CHARACTERISTICS OF OSTEOPOROTIC VERTEBRAL BODIES MONITORED BYACOUSTIC-EMISSION

The third lumbar vertebrae of nine elderly subjects (average age, 81.4 +/- 6.7 years) graded osteoporotic and the second to fifth lumbar ver tebrae of a 37-year-old man graded as normal were used to investigate microdamage accumulation during quasi-static compression loading with an acoustic emission detection system. Mechanical parameters (apparent elastic modulus, stress, and strain) and acoustic emission event coun t rates were measured simultaneously. The normalized mean value of any mechanical parameters of normal group was significantly high with res pect to that of osteoporotic group. The normalized mean value of cumul ative acoustic emission event counts to maximum stress of the normal v ertebrae was substantially small with respect to that of the osteoporo tic vertebrae (p < 0.0005, z-test). Postloading microradiographs displ ayed fracture lines adjacent to the end plates in six vertebrae of ost eoporotic group. These results are consistent with the hypotheses that microdamages of osteoporotic vertebral bodies are generated and accum ulate at lower strains than those of normal vertebrae at a specific si te.