Interface gap after implantation of a cemented femoral stem in pigs

We studied the interface gap around cemented femoral stems. Fresh pig femor a were used. Bone cement mixed under vacuum or at atmospheric pressure was injected into the femoral canal and a cobalt chrome stem was then implanted . The femora were sectioned transversely from the minor trochanter and dist ally by using a high-pressure water cutter. Most of the interfaces had inti mate contact. However, in all specimens, small gaps were found at the bone- cement and cement-stem interfaces. The gaps at the interfaces between the b one and cement and the cement and stem were measured, using a computerized video digital system. They occupied about 10% of the circumference at the b one-cement interface and about 15% of the circumference at the cement-stem interface, irrespective of the mixing procedures. Most gaps were less than 100 mu at the interfaces, In conclusion, cemented implants in the animal mo del showed that small gaps are found at the interfaces directly after impla ntation. These gaps may be weak points and initiate debonding when loading the prostheses.