A new explanation of the cancellous bone architecture.

Abstract

Various objections can be made to all the theories so far put forward in explanation of the architecture of cancellous bone. The author suggests another explanation, which takes into account the following points: 1) the structure of the secondary spongiosa is based on the pre-existent primary spongiosa, 2) the secondary spongiosa develops under alternating pressures from different directions, 3) oblique forces from marginal directions corresponding to extreme positions on the joint place the greatest strain on the spongiosa trabeculae, as demonstrated by means of a geometrical model. Oblique forces are therefore of decisive morphogenetic importance. 4) The spongiosa trabeculae are oriented in the direction of the oblique marginal forces, in accordance with the experimentally demonstrated mechanism of the strain-dependent reaction of the bone. Spatially, the secondary spongiosa assumes a fan-shaped structure. Two-dimensionally, the two intersecting systems are compression systems, each of which depends on another marginal loading direction. This pattern offers an optimum solution to the problem of the transmission of alternating forces to the diaphysis from various directions, using a minimum of material.