title: In vivo loading model to examine bone adaptation in humans: a pilot study.
abstract: Bone is typically well suited for its habitual loading environment because of its ability to adapt. Although characteristics of the mechanical loading environment predict the bone adaptive response in animals, this has not been prospectively validated in humans. Here, we describe an in vivo loading model in which women apply forces to the radius by leaning onto their hand. We characterized the strain environment imposed on the radius using cadaveric experimentation and conducted a prospective study in which 19 adult women loaded their distal radii 50 cycles/day, 3 days/week, for 28 weeks and seven additional adult women served as controls. In four cadaveric specimens, loading caused compressive principal strains of -1,695 ± 396 με with radial bending dorsally and towards the ulna. Prospective in vivo loading produced measurable improvements to bone and appeared to protect against bone loss associated with seasonal fluctuations in physical activity and sun exposure. Experimental subjects had significant gains to bone volume (BV) and moments of inertia, while, control subjects had significant losses in BMC and moments of inertia. The loading model is thus suitable as a model system for exploring bone adaptation in humans, and may eventually be clinically useful for strengthening the radius of women.
authors.affiliation: Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, USA. klreed@uic.edu
authors.forename: Karen L
authors.initials: KL
authors.lastname: Troy
authors.forename: William Brent
authors.initials: WB
authors.lastname: Edwards
authors.forename: Varun A
authors.initials: VA
authors.lastname: Bhatia
authors.forename: Mary Lou
authors.initials: ML
authors.lastname: Bareither
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000369:Aged, 80 and over; D016723:Bone Remodeling / Q000502:physiology*; D005260:Female; D006801:Humans; D010865:Pilot Projects; D011446:Prospective Studies; D011884:Radius / Q000502:physiology*; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology; D014955:Wrist Joint / Q000502:physiology; D055815:Young Adult
keywords: CT; QCT; quantitative computed tomography; upper extremity; wrist