JL. Prudhona, R. Desmarchelierb, M. Hamadouchec, C. Delaunayd, R. Verdiere,
Introduction : Recent reports from European Northern Countries registries have pointed out a high risk of infection and mortality with Total Hip Arthroplasty (THA).
Based on a matched cohort of 231 cases of Dual Mobility Cups (DMC) and 231 cases Fixed Cups (FC), the purpose of this study is to assess whether revisions for infection are higher when using DMC than FC.
Material, Methods : During two years (2010, 2011) a prospective multi center study (40 centers involved in France) was carried out by two of us. Inclusion criteria were an exhaustive collection of first revision THA (one or both components revised). We have collected 2044 cases; 251(13.5%) were DM-THA and 1793 were FS-THA (87.7%).
Due to the significant differences between these 2 populations and in order to get a closer analysis of the reasons for revision of DMC-THA we have defined a matching process (matching ratio 1:1) between the 2 cohorts. Four mandatory criteria for this matching process were : 1-interval between index surgery and revision, 2-age of the patient at index surgery, 3-gender, 4-aetiology of the primary THA. ASA score, Charnley Class and BMI were used to select the most appropriate case if several cases were suitable for the matching process.
Results : Fourty seven (20.3%) FC THAs were revised for infection, 54 (23.3%) DM THA’s. There is no statistical difference between the 2 series (p value 0,65.)
If we compare infection group ( FC THA’s and DMC THA’s) to the « non infection group » (table 3) we can observe that infection occurs early (2 years vs 7 years), mean age at index surgery is older (69 years vs 64 years), there are more males (53%), ASA score is higher (2,36 vs 2,10), BMI is higher (28 vs 26).
Discussion : Infection and dislocation are the first causes for primary THA revision in the first 3 years.
Infection risk increases through the last ten years. This increase revision rate can not clearly be explained. Our data demonstrate that revision THA for infection is not correlated to the type of cup used (DMC or FC). On an epidemiologic point of view it is mandatory when comparing outcomes to report on comparable type of patients.
On a same patients profile :
1DMC THA’s are not revised more often for infection than FC THA’s
2FC THA’s are revised 3 times more (41vs11) for dislocation than DMC THA’s.