Biomechanics of the Joints in the Leg

Abstract

Biomechanical analysis is frequently used with reference to Wolff′s Law (1) to explain the disposition of material in anatomical structures particularly with regard to the orientation of the trabeculae in the bone of the upper femoral shaft, neck and head. Most workers except Wolff′s Law as an article of faith since it seems eminently reasonable; although to the knowledge of the present author there has been no scientific validation of its relevance nor indeed an exploration of its modus operandi. For instance, it is not known whether the structure of the bone corresponds to the integral over a long period of the average value of loading experienced by the bone or whether it corresponds to the load actions developing higher than average stresses on a restricted number of occasions. Similarly, it is easy to conceive that there will be minimum and maximum thresholds corresponding to no laying down of bone or resorption of bone respectively. It is interesting to note that the lines of the trabeculae in the proximal femur are frequently associated with the lines of principal stress obtained by various means related to the loading of the head of femur and the greater trochanter. Rarely is the loading due to muscular forces included and few such studies assess the sensitivity of the position of the stress lines to the assumed direction of loading on the femoral head.