Methods

Total of 386 THAs with Trident or TriAD PSL shells were performed between January 2000 and December 2014. Exclusion criteria were shells with screw fixations (n=189), previous pelvic osteotomy (n=15) and less than 3 years’ follow-up (n=11). Finally, our study included 171 hips. Average age was 56.8 (17∼83) years at THA and average follow-up time was 8.3 (3∼16.3) years; 112 (66%) were women; and 120 hips (70.2%) had osteoarthrosis. As radiographic evaluation, we checked presence or absence of initial gap, maximum size of it, gap filling and cup stability. The presence of initial gap was defined as gap present on post-operative anteroposterior X-ray measuring 1mm or greater. Gap filling was defined as confirmed trabecular formation between the cup and acetabular floor without cup migration. And we determined the time to gap filling. As clinical evaluation, we retrospectively checked Harris Hip Score (HHS) at pre-operative and final follow-up period, and presence of shell revision. Furthermore, we compared clinical results with or without initial gap.