Bone Abstracts

Objectives: The ability to discriminate bone fractures that result from non-accidental injuries and those that result from underlying bone fragility is limited by the lack of clinical instrumentation to directly measure bone mechanical properties. The BioDent Hfc (Active Life Scientific) is an experimental device that has been validated for measuring cortical bone fracture resistance in adults. We are currently developing protocols to test the feasibility of its use in infants and children. As part of our studies, we are investigating the practical limitations of testing fracture resistance using animal models. In this study we assessed the ability of the instrument to detect age-related differences in bone mechanical properties between young and old mice.

Methods: Femora from C57BL/6 male mice aged 3, 12 and 24 months (n=6 per group) were dissected free of muscles and tendons and stored at −80 °C wrapped in gauze wetted in Hanks Balanced Salt Solution. For measurements, bones were thawed at room temperature for 2 h and indented at five locations using a reference force of 260 g and a test force of 2N over 10 cycles at 2 Hz. Indentation parameters were calculated using dedicated software from the manufacturer.

Results: Both the total indentation distance (TID) and indentation distance increment (IDI) were significantly higher in the 24-month-old mice: (TID (μm): 3 mo, 30.7±2.8; 12 mo, 38.3±8.9; 24 mo, 48.4±11.8; P<0.05, 3 vs 24 mo. IDI (μm): 3 mo, 6.4±0.8; 12 mo, 9.4±2.8; 24 mo, 15.5±7.0; P<0.01, 3 mo vs 24 mo).

Discussion: The increase in both IDI and TID implies a reduction in fracture resistance with aging. With increasing age, the variation in both measurements increased, possibly indicating that genotype exerts less of an effect than environmental factors in the age-related deterioration of the skeleton. The data show that age-related changes in bone mechanical properties can be detected using the reference point indentation technique, and suggest that the instrument will be a useful tool in studying paediatric bone diseases.