The subject matter considered in this thesis is the analysis required to obtain the force transmitted between the loaded surfaces of the human hip joint. This information is desirable for the design of implants to repair fractured bones or to replace diseased joints or, more generally, toallow the discusssion of the functional behaviour of the joint in the normal person. No published work has been found giving values of hip joint force patterns during walking for normal subjects. Procedures have been described in the literature for the determination of the resultant force actions between body segments but this thesis presents the first application of dynamic measuring techniques to the functional anatomy of the body in order to determine the internal force actions.

The relevant anatomy of the hip region is described in a preliminary chapter. Thereafter, a chronological review of the studies of human body dynamics is presented covering the time period up to 1890. Further publications after that date are presented in chronological order under the separate headings of (1) the analysis of human gait and the corresponding forces in muscles. (2) determination of body mass properties. (3) physiology. and dynamics of muscle action.

The work undertaken by the author comprised the application and modification of known engineering techniques for dynamic and kinematic measurement to the analysis of the motion of the human body. The resultant force actions between the ground and the foot of a test subject were measured by a force platform and the positions of his leg in space were recorded by cine cameras. The resultant force and moment actions transmitted across a section of the leg through the hip joint could thus be calculated. From a consideration of the time pattern of action of the hip muscles as demonstrated electromyographically, and their spatial configuration, muscle groups were defined and consideration of the resultant forces in the groups allowed the calculation of the hip joint force. The calculation procedure required the assessment of the mass properties of limb segments, and their spatial accelerations, and was performed for every fiftieth of a second interval for a complete walking cycle for each test. The procedure was therefore arranged for calculation using a digital computer and this programme, devised by the author, is outlined in the text.

Results are presented of the analyses performed on 18 tests on three female and ten male subjects. Graphs are presented of the variation with time of the resultant joint force and its components relative to the hip and to the femur. The patterns and values obtained in these tests are substantiated by results published by Dr. N. W. Rydell of the University of Gothenburg. Rydell performed tests on two patients having a strain gauged implant replacing the head of one femur. Rydell's results are included with the present author's in a statistical analysis which shows a positive correlation between (the product of body weight and stride length)and resultant joint force. The average values of joint forces on female and male subjects were 3.27 and 5.55 times body weight respectively. These values are lower bounds corresponding to the action of the muscle groups exerting the greatest moments about the joint axes. Upper bound values are also presented.

In view of the variability of the experimental quantities measured and the complex calculation procedure, the effect of these variations is subjected to critical assessment in the discussion.