Long-term studies have shown that failure of the acetabular component in a total hip replacement increases exponentially ten years following surgery (Morscher, 1992). During the cemented fixation of the acetabular cup in a total hip replacement,anchorage holes are drilled in the acetabulum in order to increase the torsional resistance of cement bonding. So far, there seems to be no definite number, size, shape, location and depth of the anchorage holes. Usually, the depth is 10 mm, the edge is90°, while the number and size of holes are interrelated, the smaller the diameter of the hole, the larger the number of holes are drilled and vice versa.Research has shown that a larger number of smaller holes add more torsional resistance to the cement bonding than a smaller number of larger holes (Oh, 1983). In practice, however, the smaller the diameter of the anchorage hole, the more difficult thecement penetration is. Moreover, it is more difficult for the surgeon to introduce bone cement into deeper anchorage holes. Also, the risk of damage to large blood vessels and organs, such as the bladder, increases when drilling deeper anchorage holes.The depth of the anchorage does not appear to affect the torsional resistance of the cement bonding (Mburu et al.,1998).
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