In vitro ultrasonic and mechanic characterization of the modulus of elasticity of children cortical bone

• Berteau Jean-Philippe
• Pithioux Martine
• Baron Cécile
• Franck Launay
• Chabrand Patrick
• Lasaygues Philippe

• Ultrasonic wave velocities
• Elastic properties
• Pediatrics
• Cortical bone

The assessment of elastic properties in children's cortical bone is a major challenge for biomechanical engineering community, more widely for health care professionals. Even with classical clinical modalities such as X-ray tomography, MRI, and/or echography, inappropriate diagnosis can result from the lack of reference values for children bone. This study provides values for elastic properties of cortical bone in children using ultrasonic and mechanical measurements, and compares them with adult values. 17 fibula samples from 8 children (4 to 16 years old, mean age 10 years old +/- 4.5) were compared to 16 fibulae samples from elderly adults (more than 75 years old). First, the dynamic modulus of elasticity (MOEdyn) and Poisson's ratio (ν) are evaluated via an ultrasonic method. Second, the static modulus of elasticity (MOEsta) is estimated from a 3-point microbending test. The mean values of longitudinal and transverse wave velocities measured at 10 MHz for the children's samples are respectively 3.2 mm/μs (+/- 0.5) and 1.8 mm/μs (+/- 0.1); for the elderly adults' samples, velocities are respectively 3.5 mm/μs (+/- 0.2) and 1.9 mm/ μs (+/- 0.09). The mean MOEdyn and the mean MOEsta for the children's samples are respectively 15.5 GPa (+/- 3.4) and 9.1 GPa (+/- 3.5); for the elderly adults' samples, they are respectively 16.7 GPa (+/- 1.9) and 5.8 GPa (+/- 2.1). MOEdyn, ν and MOEsta are in the same range for children's and elderly adults' bone without any statistical difference; a ranking correlation between MOEdyn and MOEsta is shown for the first time.