P Szulc1, E Seeman. 1. INSERM 831 Research Unit, University of Lyon, Lyon, France.
Abstract
INTRODUCTION: Bone modeling and remodeling is the final common pathway expressing all genetic and environmental factors that influence the attainment and maintenance of bone's material and structural strength. Modeling and remodeling require a surface, and during growth this cellular machinery fashions bone's external size, shape, and internal architecture by depositing bone on, and removing bone from, both its periosteal (external) and endosteal (internal) envelopes. Bone is distributed and redistributed to achieve strength commensurate with its loading requirements. METHODS: Advancing age is associated with: (1) a reduction in the volume of bone resorbed by each basic multicellular unit (BMU); (2) an even greater reduction in the volume of bone formed by each BMU so that each remodeling event, whether adaptive or reparative, removes bone from the bone; (3) increased remodeling (number of BMUs) on the three (endocortical, intracortical, and trabecular) components of its endosteal envelope in midlife in women and late in life in both sexes; and (4) reduced bone formation on the periosteal envelope. The net effect is cortical thinning, increased intracortical porosity, trabecular thinning, and loss of connectivity. RESULTS: While remodeling intensity on an envelope determines structure (e.g., trabecular perforations), the surface area of the envelope determines remodeling intensity, and, so, structure. High remodeling on trabecular surfaces decreases as trabeculae (with their surface) are lost. Conversely, remodeling on the endocortical and intracortical envelopes increases their surface area, so remodeling intensity increases and bone loss becomes predominantly cortical. CONCLUSIONS: Understanding bone structural strength and its decay and the effects of genetic factors, exercise, nutrition, and drug therapy on bone requires thinking outside and inside these envelopes; their absolute and relative movements during growth and aging determine bone structure and its strength.
INTRODUCTION: Bone modeling and remodeling is the final common pathway expressing all genetic and environmental factors that influence the attainment and maintenance of bone's material and structural strength. Modeling and remodeling require a surface, and during growth this cellular machinery fashions bone's external size, shape, and internal architecture by depositing bone on, and removing bone from, both its periosteal (external) and endosteal (internal) envelopes. Bone is distributed and redistributed to achieve strength commensurate with its loading requirements. METHODS: Advancing age is associated with: (1) a reduction in the volume of bone resorbed by each basic multicellular unit (BMU); (2) an even greater reduction in the volume of bone formed by each BMU so that each remodeling event, whether adaptive or reparative, removes bone from the bone; (3) increased remodeling (number of BMUs) on the three (endocortical, intracortical, and trabecular) components of its endosteal envelope in midlife in women and late in life in both sexes; and (4) reduced bone formation on the periosteal envelope. The net effect is cortical thinning, increased intracortical porosity, trabecular thinning, and loss of connectivity. RESULTS: While remodeling intensity on an envelope determines structure (e.g., trabecular perforations), the surface area of the envelope determines remodeling intensity, and, so, structure. High remodeling on trabecular surfaces decreases as trabeculae (with their surface) are lost. Conversely, remodeling on the endocortical and intracortical envelopes increases their surface area, so remodeling intensity increases and bone loss becomes predominantly cortical. CONCLUSIONS: Understanding bone structural strength and its decay and the effects of genetic factors, exercise, nutrition, and drug therapy on bone requires thinking outside and inside these envelopes; their absolute and relative movements during growth and aging determine bone structure and its strength.
Authors: Henrik G Ahlborg; Olof Johnell; Charles H Turner; Gunnar Rannevik; Magnus K Karlsson Journal: N Engl J Med Date: 2003-07-24 Impact factor: 91.245
Authors: B Lawrence Riggs; L Joseph Melton; Richard A Robb; Jon J Camp; Elizabeth J Atkinson; Lisa McDaniel; Shreyasee Amin; Peggy A Rouleau; Sundeep Khosla Journal: J Bone Miner Res Date: 2008-02 Impact factor: 6.741
Authors: C Chappard; S Bensalah; C Olivier; P J Gouttenoire; A Marchadier; C Benhamou; F Peyrin Journal: Osteoporos Int Date: 2012-07-20 Impact factor: 4.507
Authors: Chelsea M Heveran; Charles A Schurman; Claire Acevedo; Eric W Livingston; Danielle Howe; Eric G Schaible; Heather B Hunt; Adam Rauff; Eve Donnelly; R Dana Carpenter; Moshe Levi; Anthony G Lau; Ted A Bateman; Tamara Alliston; Karen B King; Virginia L Ferguson Journal: Bone Date: 2019-05-02 Impact factor: 4.398