Computed tomography reconstruction from hollow projections: an application to in vivo evaluation of artificial hip joints.

The long-term mechanical stability of total hip arthroplasties limits the application of this widely used surgical procedure in cases of severe coxarthroses. A noninvasive method of assessing the tissue distribution in the vicinity of the implant--bone interface is needed to identify early signs of implant loosening and to evaluate new prosthetic solutions. In order to develop such a method, a modified computed tomography technique has been devised that yields cross-sectional images without the usual artifacts caused by metallic implants. This technique provides information on bone mineral and bone cement distributions as well as on the precise position and orientation of the implant within the femur shaft. Results obtained from excised human femurs and preliminary data from measurements on patients made 3 months postoperatively reveal that the bone cement distribution is much less favorable than is indicated by radiographs.