Search

Fracture occurs when mechanical loading exceeds bones strength. The National Institute of Health defines osteoporosis as a skeletal disorder characterized by decreased bone strength, but no medical device measures bone strength directly in vivo. Bone stiffness is strongly associated with bone strength, but no clinical method measures bone stiffness in vivo, either. Quasistatic Mechanical Testing (QMT) is the reference gold standard method for directly measuring the stiffness and strength of bones, but it can only be employed on excised bones and bone samples. Mechanical Response Tissue Analysis (MRTA) is a minimal-risk, non-invasive, radiation-free technique for measuring the bending stiffness of certain long bones, such as the ulna, in humans in vivo. MRTA was originally developed at Stanford University in the 1980's, but limited information has been published about its accuracy. Ohio University is further developing an MRTA device and the purpose of the research reported in this thesis was to validate the accuracy, precision, and repeatability of this device by comparison to QMT. The stiffness of standard and custom artificial human ulnas (N = 39) with -10% to +10% excess glass fill in the glass-epoxy composite emulating cortical bone (Pacific Research Laboratories/Sawbones, Vashon, WA) were measured by MRTA and QMT in 3-point antero-posterior bending with proximal support by an articulating vertical Sawbones® humerus and distal support by the anterior distal radio-ulnar articular surface on a steel block. The load was applied at the mid-point of the posterior border. The precision and repeatability, respectively, of stiffness measurements were calculated without and with dismounting of ulnas from the humerus between repeated measures. Fifteen of the artificial human ulnas were then fractured by QMT under the same support conditions to determine the relationship between bending stiffness and strength. Results demonstrated that in our hands MRTA and QMT measurements of bending stiffness in artificial human ulnas were virtually identical (MRTA = 1.001*QMT (R^2 = 0.999), and MRTA measurements would be sufficiently precise (1.0 ± 1.0 %), repeatable (3.1 ± 3.1 %), unbiased and interchangeable (± 5%) with QMT for clinical purposes. Additionally, MRTA and QMT measurements of ulna bending stiffness were both strongly associated (R^2 = 0.97) with QMT measurements of ulna bending strength. If ongoing research finds that Ohio University’s MRTA device also achieves sufficient measurement performance in cadaveric human arms and ulnas, then MRTA may eventually prove clinically useful for measuring ulna stiffness, estimating ulna strength and predicting fracture risk.