BONE STREAMING POTENTIALS AND CURRENTS DEPEND ON ANATOMICAL STRUCTUREAND LOADING ORIENTATION

Bone streaming potentials (SPs) and streaming currents (SCs) may be a remodeling signal to cells, and might also be used to probe bone pore structure and fluid flows. For SPs or SCs to serve as either a remodel ing signal or as a probe for pore structure, they must depend on bone structure. This study was undertaken to address two related questions. First, will differences in Haversian and laminar bone structure and f luid flow direction produce measurable differences in SP and SC? Secon d, do differences in SP or SC relate to differences in macroscopic bon e impedance or large pore structure? SPs and SCs were measured across Haversian and laminar bone specimens with fluid flow driven in differe nt directions by sinusoidal four-point bending. Data were grouped by b one type and flow direction (Haversian tissue, laminar tissue with rad ial flow, and laminar tissue with tangential flow) and flow direction alone (tangential and radial). SPs were larger for Haversian tissue an d for laminar tissue with radial flow than for laminar tissue with tan gential flow. SP and SC magnitude, and impedance were larger for radia l than tangential flow. No difference in SC magnitude, SP or SC kineti cs, or macroscopic bone impedance was observed between Haversian tissu e, laminar tissue with radial flow, and laminar tissue with tangential flow. Thus, since laminar tissue with tangential flow had more vascul ar connections in the direction of fluid flow, SP was smallest for gre atest vascular connectivity. The relation between SP or SC and impedan ce was inconclusive. (C) 1997 Elsevier Science Ltd. All rights reserve d.