Mapping of surface area 'containment' of the femoral head during walking.

This note describes a mathematical method for the calculation of surface area of the femoral head covered ('contained') by the acetabulum as a time-dependent function. It uses displacement vectors from the center of rotation of the hip joint to the femoral joint surface, and rotates these vectors in small increments to simulate the desired motion. At each interval, the vectors are tested to determine whether they lie within the coverage area of the acetabulum. The result is a containment density plot which displays coverage area as a function of time. The general method is used in a variety of clinically important situations, and an example of its use in the study of abduction bracing is described.