title: Compressive behaviour of child and adult cortical bone.
abstract: In this study, cortical bone tissue from children was investigated. It is extremely difficult to obtain human child tissue. Therefore, the only possibility was to use bone tissue, free from any lesion, collected from young bone cancer patients. The compressive mechanical behaviour of child bone tissue was compared to the behaviour of adult tissue. Moreover, two hypotheses were tested: 1) that the mechanical behaviour of both groups is correlated to ash density; 2) that yield strain is an invariant. Small parts of the diaphysis of femora or tibiae from 12 children (4-15 years) and 12 adults (22-61 years) were collected. Cylindrical specimens were extracted from the cortical wall along the longitudinal axis of the diaphysis. A total of 107 specimens underwent compressive testing (strain rate: 0.1 s(-1)). Only the specimens showing a regular load-displacement curve (94) were considered valid and thereafter reduced to ash. It was found that the child bone tissue had significant lower compressive Young's modulus (-34%), yield stress (-38%), ultimate stress (-33%) and ash density (-17%) than the adult tissue. Conversely, higher compressive ultimate strain was found in the child group (+24%). Despite specimens extracted from both children and adults, ash density largely described the variation in tissue strength and stiffness (R(2)=in the range of 0.86-0.91). Furthermore, yield strain seemed to be roughly an invariant to subject age and tissue density. These results confirm that the mechanical properties of child cortical bone tissue are different from that of adult tissue. However, such differences are correlated to differences in tissue ash density. In fact, ash density was found to be a good predictor of strength and stiffness, also for cortical bone collected from children. Finally, the present findings support the hypothesis that compressive yield strain is an invariant.
authors.affiliation: Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy.
authors.forename: Caroline
authors.initials: C
authors.lastname: Öhman
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Baleani
authors.forename: Carla
authors.initials: C
authors.lastname: Pani
authors.forename: Fulvia
authors.initials: F
authors.lastname: Taddei
authors.forename: Marco
authors.initials: M
authors.lastname: Alberghini
authors.forename: Marco
authors.initials: M
authors.lastname: Viceconti
authors.forename: Marco
authors.initials: M
authors.lastname: Manfrini
mesh_terms: D000328:Adult; D001842:Bone and Bones / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D019245:Compressive Strength / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D055815:Young Adult