n Revisions Median follow-up (range) Mean age (min–max) % < 60 years % male Deceased Emigrated Missing Alive Diagnosis Osteoarthritis RA/Inflammatory Sequelae hip fracture Dysplasia Perthes’ Other 3-year survival (95%CI) 5-year survival (95%CI) 7-year survival (95%CI) RR c (95%CI) 37,666 1,140 4.7 (0–10) 73 (16–98) 9 29 5,928 (15.7%) 58 (0.2%) 2 31,678 (84.1%) 78.6% 3.3% 8.9% 4.3% 0.6% 4.4% 97.9 (97.7–98.0) 97.0 (96.8–97.2) 96.0 (95.7–96.2) 1 (Reference) a Chi-squared test. b Non-parametric Mann-Whitney. c RR adjusted for age, sex, and diagnosis. 3,963 108 2.9 (0–10) 61 (18–92) 42 36 104 (2.6%) 8 (0.2%) 0 3,851 (97.2%) 70.9% 4.2% 5.2% 11.6% 2.2% 5.9% 97.7 (97.2–98.2) 96.7 (96.0–97.4) 95.6 (94.4–96.7) 1.1 (0.9–1.4) p-value < 0.001 b < 0.001 b < 0.001 a < 0.001 a < 0.001 a 0.3 3,480 135 5.2 (0–10) 54 (16–60) 100 36 229 (6.6%) 21 (0.6%) 0 3,230 (92.8%) 56.6% 8.0% 7.1% 16.5% 3.1% 8.7% 98.0 (97.5–98.5) 96.7 (96.0–97.3) 94.9 (94.0–95.9) 1 (Reference) 1,647 41 3.4 (0–10) 52 (18–60) 100 39 25 (1.5%) 4 (0.4%) 0 1,618 (98.2%) 55.9% 6.0% 4.8% 20.4% 4.5% 8.4% 98.3 (97.7–99.0) 97.5 (96.6–98.5) 96.2 (94.6–97.8) 0.9 (0.6–1.3) p-value < 0.001 b < 0.001 b 0.06 a < 0.001 a 0.5 642 Acta Orthopaedica 2011; 82 (6): 639–645 Table 5. Comparison of demographic data for cemented and reverse hybrid THRs, both for total material and for patients aged < 60 years. Comparison of survival (in %) and relative risk (RR) of revision for cemented and reverse hybrid THRs, with all revisions as endpoint, for total material and for patients aged < 60 years Total material Cemented Reverse hybrid Age < 60 years Cemented Reverse hybrid Results The mean age was lower in the reverse hybrid group than in the cemented group: 61 (18–92) years as opposed to 73 (16–98) years. The proportion of males was higher in the reverse hybrid group than in the cemented group (36% vs. 29%). In addition, 9% of patients were below 60 years of age in the cemented group and the corresponding proportion in the reverse hybrid group was 42%. Furthermore, there were significant differ- ences regarding diagnosis, age, and sex (Table 5). In the total material, median follow-up was 2.9 (0–10) years in the reverse hybrid group and 4.7 (0–10) years in the cemented group. For patients aged less than 60 years, the median follow-up was 3.4 (0–10) years for reverse hybrid and 5.2 (0–10) years for cemented (Table 5). There was no statistically significant difference in implant survival between cemented and reverse hybrid THRs when the endpoint was any revision. This was also found in analyses of cases less than 60 years of age (Figures 2 and 3, Table 5). In subanalyses of the total material using the endpoints revision due to deep infection, dislocation, aseptically loosened stem, and aseptically loosened cup, no statistically significant differ- ences between cemented and reverse hybrid THRs were found. The reverse hybrids had a 3.6 times higher risk of revision for periprosthetic femoral fracture compared to the cemented implants (CI: 1.9–6.9; p < 0.001). The survival was 99.85% (99.8–99.9) and 99.6% (99.3–99.9), respectively, at 5 years using this endpoint. We performed analyses of the different cup/stem combina- tions in the reverse hybrid group with all revisions as the end- point at 3 and 5 years. No statistically significant differences were found. Reflection PE/Hactiv and Reflection PE/Taperloc had less than 20 hips left at risk at 5 years; thus, 5-year sur- vival of these combinations could not be estimated. In the reverse hybrid group, 3,832 of the 3,963 prostheses had a femoral head with a diameter of 28 mm. 2,467 heads were made of alumina and 1,286 heads were made of cobalt chromium. In these 2 groups, all head sizes were included. Among the different groups of reverse hybrid combinations, we noted differences in age, in median follow–up time, and in the male/female ratio. The ReflectionPE/Taperloc com- bination has been used since 2005, but maximum follow-up for this group only reached 4.7 years. All the other groups of reverse hybrid combinations had a maximum follow-up of more than 5 years (Table 2). Discussion The use of reverse hybrids has increased in Norway and Sweden during the last decade. Before 2000, few reverse hybrid operations were performed each year, and with many