Structural and geometric changes in iliac bone: Relationship to normal aging and osteoporosis

Abstract

We Measured Indices Of Bone Volume (Cancellous And Cortical) And Bone Surface (Cancellous, Endocortical, And Intracortical) In Intact, Full-Thickness Transiliac Bone Biopsies Obtained From 47 Healthy White Women (23 Premenopausal And 24 Postmenopausal) And 82 Patients With Postmenopausal Osteoporosis. In The Normal Subjects There Was The Expected Loss Of Cancellous Bone With Age, Best Shown By A Reduction In Bone Surface/Tissue Volume, But No Fall In Cortical Thickness With Age Despite A Significant Reduction In Forearm Bone Density Measured By Single-Photon Absorptiometry. Bone Surface/Bone Volume Was About Four Times Higher In Cancellous Than In Cortical Bone, And Cancellous Bone Contributed About One-Third Of The Total Bone Volume And About Two-Thirds Of The Bone Surface When Related To The Core Volume Referent. In The Osteoporotic Patients, Core Width, An Index Of Iliac Bone Thickness At The Biopsy Site, Was Reduced By 10%, But We Could Not Determine Whether This Was The Result Of Compaction Of The Core Or Of Bone Slenderness. All Indices Of Bone Volume, Cortical As Well As Cancellous, Were Significantly Smaller, As Were The Values For Forearm Bone Densitometry; The Relative Deficits At Different Sites Depended On Whether They Were Expressed As Percentages Or As Z Scores. Bone Surface/Bone Volume Was Increased In Both Cancellous And Cortical Bone, But Bone Surface/Tissue Volume Was Reduced In Cancellous Bone And Increased In Cortical Bone. The Proportions Of Total Bone Volume And Surface Contributed By Cancellous And Cortical Bone Were Almost The Same As In Normal Postmenopausal Women. We Reached The Following Conclusions: (1) Age-Related Bone Loss In Normal Subjects Is More Difficult To Detect By Histomorphometry Than By Densitometry. (2) Cortical Bone Loss May Be Slower In The Axial Than In The Appendicular Skeleton. (3) The Amount Of Bone Is Reduced At All Sites In Osteoporotic Patients; The Deficit Is Not Necessarily Greater In Cancellous Than In Cortical Bone But May Be Greater In The Axial Than In The Appendicular Skeleton. (4) Cortical Bone Contributes Relatively Less Volume And Relatively More Surface In The Axial Then In The Appendicular Skeleton. (5) Depending On The Location And The Referent, Bone Surface And Volume May Change In The Same Or In Opposite Directions, With Consequences For The Time Course Of Bone Loss And The Relationships Between Biochemical And Histologic Indices Of Bone Remodeling.