CANCELLOUS BONE ARCHITECTURE - ADVANTAGES OF NONORTHOGONAL TRABECULARALIGNMENT UNDER MULTIDIRECTIONAL JOINT LOADING

Wolff proposed that trabeculae align al 90 degrees angles (orthogonal) . However, nonorthogonal alignment of trabeculae has been observed nea r many joints, including the proximal femur. We propose that nonorthog onal alignment is an adaptation to multidirectional joint loads. When the loading direction does not correspond with the trabecular alignmen t, warping or shear coupling occurs leading to large shear strains wit hin the cancellous structure. Using a simplified continuum model for t rabecular bone, we demonstrate that shear coupling caused by multidire ctional joint loads is reduced 33-75% when trabeculae are aligned 60 d egrees from one another (as is observed in regions of the proximal fem ur), as opposed to 90 degrees from one another (as was predicted by Wo lff). The results suggest that an optimal cancellous structure may app ear differently under multidirectional joint loads than the 'trajector ial' organization proposed by Wolff, which was based upon assumptions drawn from unidirectional loading. (C) 1997 Elsevier Science Ltd.