In the development and design of the ISC Interlock Cup the prevailing idea was to develop a spherical press-fit cup with flattened pole which, in this form, proved itself in practical use for many years.
New in the ISC Cup is that the primary stability is achieved not only by press-fit using an oversized cup in the equatorial region, but, thanks to an idea and encouragement from Prof. Hanns Hofer from Salzburg, also through 3 spiral-shaped ribs on the outer surface of the metal cup at 0, 120 and 240 degrees, whereby it is possible to do without fixation with cancellous bone screws and therefore without screw holes in the ISC Cup.
Not only the rotational stability but also the axial stability is clearly enhanced through the 3 mentioned spiral-shaped ribs on the outer surface of the ISC Cup.
A further advantage of the interlock cup is the presence of the central hole at the bottom of the metal cup, which provides a good insight and overview during positioning of the cup. Through this central opening it is possible to estimate exactly the distance from the ISC Cup to the bony bottom of the acetabulum and determine the necessity for a possible introduction of bone material. (The mentioned opening at the bottom of the cup has a diameter of 15 mm for cup sizes 46-54 and a diameter of 18 mm for sizes 56-66, what allows to introduce the cancellous bone without difficulties.) This central hole at the bottom of the cup is tightly closed by a titanium lid, which is very simply handled by a well thought-out device. The tightly closing titanium lid prevents the intrusion of connective tissue from the bottom into the inner side of the titanium cup and thereby enhances the osseointergration in the regions of the acetabular bottom.