An image processing technique for the identification of contact pixels applied to X-ray CT images of implanted hip prostheses

Uncemented prosthetic joint implants used in orthopaedic surgery are usually coated with a porous surface to encourage bone ingrowth. Better contact between the endosteal bone and the porous surface improves ingrowth, and such contact may be increased if the joint further subsides into position in the first weeks following implantation. An image processing technique has been developed as part of a study undertaken to determine the effect of early subsidence on endosteal contact. The method provides a measure of the degree of contact between the surfaces from transverse x-ray CT images, but is suitable for application to any image with a similar intensity distribution.