DISLOCATION FOLLOWING THA - COMPARISON OF 2 ACETABULAR COMPONENT DESIGNS

One hundred ninety-seven consecutive primary cemented total hip arthro plasties using 22 mm heads were evaluated for the rate of dislocation. All surgery was performed by one surgeon through a posterior approach . A Charnley type femoral component was used in each case. Patients we re divided into three groups based on the acetabular component used. G roup I had 60 Charnley HPW cups implanted between January 1985 and Dec ember 1986; group II bad 70 Tibac cups implanted between January 1987 and August 1987; and group III had 67 Charnley HPW cups implanted betw een September 1987 and February 1988. The groups were similar with reg ards to age, sex, original diagnosis, and surgical technique. There wa s a total of 11 dislocations (5.6%), of which 8 (11.4%) occurred in gr oup II (Tibac cup). Furthermore, 6 patients (3%) developed recurrent h ip dislocations, 5 (7.1%) of which were from group II. Group II had a statistically significant increase in the dislocation rate (P<.05). Th e authors conclude that the dislocation rate with the 22 mm Tibac cup is unacceptably high and that the design of the Charnley cup affords g reater stability to the artificial hip joint than the hemispherical de sign of the Tibac cup.