Analyses of the bone mass alone of osteoporotic vertebrae are not sufficient to predict fracture risks and assess the recovery of bone strength during drug treatment. Instead, finite element analyses (FEAs) is superior, because changes in the vertebral strength are strongly dependent on the inner vertebral stress distribution, which is related to the individual bone shape and bone density distribution in cancellous and cortical region. To investigate how FEAs can detect drug effects, we performed patient-specific FEAs of the first lumbar vertebra of osteoporotic patients at five time points (before therapy, and after 6 and 12 months and 2 and 3 years of therapy) during a 3-year drug treatment with alendronate and vitamin D, in four osteoporotic female patients in this study. The FEAs revealed notable decreases in the compressive principal strains in cancellous bone, but these decreases did not necessarily correspond to increases in the bone densities. In addition, statistical analyses by Friedman's test (nonparametric analysis) showed that evaluation based only on the average compressive principal strains over the 3-year treatment identified drug effects significantly, suggesting that compressive principal strain is an useful indicators for monitoring drug effects. Our data implied that compressive fracture of the vertebrae may be prevented as a result of the drug treatment, in a manner that was optimally detectable by patient-specific FEAs.

Keywords

Computational Biomechanics, Finite Element Method, Bone Strength, Therapeutic Effect, Patient-Specific Modeling, Vertebra, Osteoporosis

Paper information

Daisuke TAWARA, Jiro SAKAMOTO, Hideki MURAKAMI, Norio KAWAHARA and Katsuro TOMITA, “Patient-Specific Finite Element Analyses Detect Significant Mechanical Therapeutic Effects on Osteoporotic Vertebrae During a Three-Year Treatment”, Journal of Biomechanical Science and Engineering, Vol. 6, No. 4 (2011), pp.248-261 . doi:10.1299/jbse.6.248

Patient-specific nonlinear finite element analysis (FEA) is promising for evaluating the recovery of vertebral strength. Vertebral strength is closely related to inner vertebral stress distribution and is used to assess the fracture risk for individual osteoporotic patients during drug treatment. Moreover, stress distribution is affected by individual bone shape, bone density distribution and nonlinear behavior of the mechanical properties of bone. To investigate the effectiveness of FEA considering these factors for the evaluation of drug treatment effects, patient-specific nonlinear FEAs of the first lumbar vertebrae in patients undergoing a 3-year drug treatment were performed. Changes in fracture load and distribution of failure elements in the FE models at four time points (before therapy, and after 6 and 12 months and 3 years of therapy) were compared with those of average bone density. The FEAs demonstrated that failure elements decreased notably, and fracture load increased gradually by the 3-year time point, suggesting that the vertebrae were strengthened as a result of drug treatments. Furthermore, statistical tests indicated that mechanical evaluation using the nonlinear FEAs is more sensitive for evaluating drug effects on osteoporotic bone than assessments based on average bone density.

Keywords

Computational Biomechanics, Bone Strength, Patient-Specific Image-Based Modeling, Vertebra, Osteoporosis, Therapeutic Effect

Paper information

Daisuke TAWARA, Jiro SAKAMOTO, Hideki MURAKAMI, Norio KAWAHARA, Juhachi ODA and Katsuro TOMITA, “Mechanical Therapeutic Effects in Osteoporotic L1-Vertebrae Evaluated by Nonlinear Patient-specific Finite Element Analysis”, Journal of Biomechanical Science and Engineering, Vol. 5, No. 5 (2010), pp.499-514 . doi:10.1299/jbse.5.499

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Keywords

Paper information

Jiro Sakamoto, “Preface”, Journal of Biomechanical Science and Engineering, Vol. 5, No. 5 (2010), pp.484-484 . doi:10.1299/jbse.5.484