Abstract
As part of a user group of a collarless polished tapered stem a database was established in 1993 recording all significant data pre-operatively, intra-operatively and at 1,3,5 and 7 years.
All were primary hip replacements and the study included 38 different surgeons who were free to use the head size, approach and cup of their choosing. All hips had a collarless polished tapered prosthesis (Zimmer inc.).
Data on 2,250 hips were available for analysis and stratification of risk factors for dislocation. Correlation of head size and surgical approach was performed and tested for significance. The patient demographics were standard for a typical arthroplasty study group. Of the surgical approaches used, 13.1% were anterolateral, 27.55% lateral, 23.88% posterior and 35.47% Hardinge. There were no trochanter osteotomies or anterior approaches.
94 (100%) of the hips had a first dislocation occurring in the first two years: 38 during acute stay (40.43%), 45 from acute stay to the first year (47.88%) and 11 during the second year (11.7%). The 22mm head was associated with the greatest risk of dislocation (5.93%, P < 0.001). The risks with the 28mm head (3.05%) and the 26mm head (2.5%) were not significantly different. The lowest risk of dislocation occurred with the lateral approach (2.11%) and the highest with the posterior approach (5.99%). Dislocation rates for the anterolateral and Hardinge approaches (4.1% and 3.28% respectively) were not significantly different. Unfortunately data pertaining to frequency of capsular repair combined with the posterior approach was not available.
The combination of lateral approach and 28mm head was associated with the lowest dislocation risk of 1.56%, while the risk with the posterior approach and 22mm head was the highest at 10.09%.
Editoral Secretary Mr Peter Howard. Correspondence should be addressed to BHS at the Royal College of Surgeons, 35 - 43 Lincoln’s Inn Fields, London WC2A 3PN.
