A new method for measuring the thickness of the cement mantle in endoprostheses

The distribution of bone cement around an endoprosthesis influences its sta bility over the long term. We have developed a new method for the experimen tal measurement of the cement mantle thickness of an endoprosthesis. The us e of this computer-aided procedure is described in a hip prosthesis. Transv erse sections of a human femur containing a cemented stem were prepared, re corded with a CCD camera and the images fed into a computer. The image-proc essing software differentiated the metal and bone cement on the basis of th e different colours. Radial lines were drawn from the calculated centre of gravity of the stem, and the cement thickness was measured automatically al ong these lines. In our experiment, the accuracy of the method was 0.2 mm. This method of measuring the thickness of the cement mantle is accurate, ra pid and practical.