Introduction. The Kaplan Meier estimator is widely used in orthopedics. In situations where another event prevents the occurrence of the event of interest, the Kaplan Meier estimator is not appropriate and a competing risks model has to be applied. We questioned how much bias is introduced by erroneous use of the Kaplan Meier estimator instead of a competing risks model in a hip revision surgery cohort. Methods. In our previously published cohort study, 62 acetabular revisions (58 patients) were performed between January 1979 and March 1986. Twenty to twenty-five years after surgery, no patients were lost to follow-up. Thirteen patients underwent revision surgery. During the 20 to 25 years follow-up, 30 patients (33 acetabular revisions) died of causes unrelated to their hip surgery. Results. In the data set analyzed, the Kaplan Meier method overestimates the probability of implant failure by 6.7%, 13.8%,26.8%,48.6% at 5, 10, 15 and 20 years respectively. Discussion. We have performed two different analyses for a hip revision surgery cohort and discussed the use of a competing risks model. Ignoring competing risks leads to biased estimations of the probability of having future revision surgery. Therefore we recommended the use of a competing risks model whenever there are competing risks present

Between July 2000 and December 2002, 263 consecutive patients across 5 surgical centers underwent to a revision surgery of a failed acetabular component in which TM acetabular components were used.

There were 150 women and 113 men with a mean age of 69.5 years.

The indication for acetabular revision was aseptic loosening in 186 cases (70.7%)

Clinical evaluations were performed using the Harris hip score, the WOMAC and UCLA activity scale.

Implant and screw position, polyethylene wear, radiolucent lines, gaps, and osteolysis were assessed. Preoperatively, acetabular bone deficiency was categorized using the classification of Paprosky et al.

Statistical analysis was performed using nonparametric correlations. Standard life table was constructed, and the survival rate was calculated by means of Kaplan-Meier method.

The overall mean follow-up was 73.6 months (range, 60–84 months), and no patient was lost to follow-up.

The preoperative HHS rating improved from a mean of 43.6 ± 11.4 before revision, to a mean of 82.1 ± 10.7.

None of the patients was re-revised for loosening. The cumulative prosthesis survival was 99.2% at 5 years.

There was no correlation found between the various degrees of acetabular bony defect and the magnitude of clinical results (independent of pre-revision Paprosky grade). The use of component augments allowed us to minimize the volume of morsellized allograft used for defect repair.

TM acetabular component demonstrates promising midterm results similar to those reported by other authors.