Stability of cemented sockets after 3-14 years.

The strength of the mechanical fixation of cemented sockets was studied in 10 pelvic specimens retrieved at autopsy from patients who had had total hip arthroplasty (THA) (group 1). A further 11 sockets, cemented into the acetabulae of fresh cadaver specimens, served as a control group (group 2). The mean twisting torques required to break the sockets loose were 80 Nm and 86 Nm in groups 1 and 2, respectively (no significant difference). However, in all 21 cases the mode of loosening deviated from what is commonly observed in revision operations of loosened THA sockets. The authors conclude that tests of implant stability should not be performed by breaking the implant loose since it is a poor simulation of what seems to occur in vivo.