Abstract
The durable fixation of an uncemented cup is due to two major factors: the primary stability obtained by the design of the cup and the secondary fixation obtained by the features of the surface of the cup. The CSF (cancellous screws fixation) cup is an emispheric press-fit Hydroxyapatite coated cup that has 5 holes for screws. This permit to insert screws not only in the superior part of the acetabulum but also in the inferior and supero-medial. This theoretically guarantee, also in those cases in which a perfect press-fit was non achievable, a good primary fixation. This primary fixation permit the osteo-conductive function of the HA coating in order to gain secondary e more stable fixation.
From january 1999 to september 2003 we per-formed130 uncemented THR with the CSF cup and the Furlong stem. In the first 100we always insert three screws. In the next 30 only in case of a non perfect-press-fit (10). The mean age was 65 years (14–80). The follow-up varying from 5 years to 6 months. The study is retrospective.
At the last follow-up all implants resulted well integrated.. The formation of new trabecular bone bonding the cup was noted on the X-ray since the third month’s control. There was no complication due to the position of the screws. All patients regained full authonomy.
Primary stability is mandatory in order to obtain a good secondary fixation by osteointegration. The possibility to insert additional screws in a triaxial fashion permit to obtain good primary stability. in all the cases. The screws must be inserted carefully under X-ray in order to avoid complications. Hydroxyapatite, guiding the growth of new trabecular bone bonding the cup to the pelvic bone, guarantee a good secondary fixation.
Correspondence should be addressed to Richard Komistek, PhD, International Society for Technology in Arthroplasty, PO Box 6564, Auburn, CA 95604, USA. E-mail: ista@pacbell.net
