1. Survival of total hip arthroplasty (THA) in younger patients Effect of hydroxyapatite coating and cement Aksel Paulsen, Søren P. Johnsen, Alma B. Pedersen, Ulf Lucht, Søren Overgaard Department of Orthopedics, Aarhus University Hospital, Denmark. Department of Clinical Epidemiology, Aarhus University Hospital, Denmark. Department of Orthopedics, Odense University Hospital, Denmark. University of Southern Denmark, SDU, Denmark

2. INTRODUCTION: Hydroxyapatite (HA) coating of uncemented THA is widely used; however, the effect of HA on implant survival are sparse. AIM: 1. What is the effect of HA coating on the survival of uncemented THA, compared to non HA coating, in cups and stems? 2. What is the effect compared to cemented THA?

3. MATERIAL: This review is a cohort analysis based on the Danish Hip Arthroplasty Registry (DHR). We identified all primary THA in patients less than 70 years during 1995-2003. The follow-up was 0-9 years.

4. MATERIAL: Available for analyses: Cups : A total of 23,516; 8,556 cemented 3,151 uncemented, HA-coated 11,809 uncemented, non-HA-coated Stems: A total of 23,434; 15,634 cemented 2,318 uncemented, HA-coated 5,482 uncemented, non-HA-coated.

5. METHODS: We defined revision of the components as endpoint, divided into two different outcomes; revision because of aseptic loosening, and revision due to ”any reason” Revision and ”any reason” was defined in accordance to the DHR registration form. METHODS: We defined revision of the components as endpoint, divided into two different outcomes; revision because of aseptic loosening, and revision due to ”any reason” Revision and ”any reason” was defined in accordance to the DHR registration form.

6. METHODS: The relative risk (RR) of revision due to aseptic loosening or “any reason”, was adjusted for possible confounders using multivariate Cox regression analysis. The analyzes were adjusted for: age (< 50, 50-59, 60-69), gender, primary diagnosis, and fixation of the opposite implant part (Cup /Stem). METHODS: The relative risk (RR) of revision due to aseptic loosening or “any reason”, was adjusted for possible confounders using multivariate Cox regression analysis. The analyzes were adjusted for: age (< 50, 50-59, 60-69), gender, primary diagnosis, and fixation of the opposite implant part (Cup /Stem).

7. METHODS: Statistical analyzes: age (<60, 60-69), gender, producer/ model of the components, diagnosis (primary arthrosis/ “all diagnosis”). METHODS: Statistical analyzes: age (<60, 60-69), gender, producer/ model of the components, diagnosis (primary arthrosis/ “all diagnosis”). None of the groups had less than 400 patients. The software we used was SAS. Statistician Anders Riis was of technical assistance in the formulation of the statistical analysis. Statistical level of significance was set to 5 %.

8. RESULTS: Cups; HA-coating VS. non HA-coating (all diagnosis) Adjusted RRs of revision; Endpoint: aseptic loosening; N total N total N revised N revised RR RR 95 % CI 95 % CI Uncemented - HA 11,809 11,809 49 49 1 Uncemented + HA 3,151 3,151 60.67 0.29 - 1.57

9. RESULTS: Cups; HA-coating VS. non HA-coating (all diagnosis) Adjusted RRs of revision; Endpoint: aseptic loosening; Endpoint: any reason; Same findings for: idiopathic arthrosis, age, gender, component type N total N total N revised N revised RR RR 95 % CI 95 % CI Uncemented - HA 11,809 11,809 49 49 1 Uncemented + HA 3,151 3,151 60.67 0.29 - 1.57 N total N total N revised N revised RR RR 95 % CI 95 % CI Uncemented - HA 11,809 11,809 406 406 1 Uncemented + HA 3,151 3,151 87 870.97 0.77 - 1.22

10. RESULTS: Cups; Cemented VS. Uncemented (all diagnosis) Adjusted RRs of revision; Endpoint: aseptic loosening; N total N total N revised N revised RR RR 95 % CI 95 % CI Cemented 8,556 8,556 131 131 1 Uncemented - HA 11,809 11,809 49 490.32 0.22 - 0.45 Uncemented + HA 3,151 3,151 60.21 0.09 - 0.48

11. RESULTS: Cups; Cemented VS. Uncemented (all diagnosis) Adjusted RRs of revision; Endpoint: aseptic loosening; Endpoint: any reason; Same findings for: idiopathic arthrosis, age, gender, component type N total N total N revised N revised RR RR 95 % CI 95 % CI Cemented 8,556 8,556 131 131 1 Uncemented - HA 11,809 11,809 49 490.32 0.22 - 0.45 Uncemented + HA 3,151 3,151 60.21 0.09 - 0.48 Cemented 8,556 8,556 331 331 1 Uncemented - HA 11,809 11,809 406 4060.99 0.85 - 1.15 Uncemented + HA 3,151 3,151 87 870.96 0.75 - 1.23

12. RESULTS: RESULTS: Cup; Aseptic loosening: ( * = none in group) N total N total N revised N revised RR RR 95 % CI 95 % CI Trilogy Uncemented -HA 5,187151 Trilogy Uncemented +HA 6530** Universal Uncemented / Mallory-Head +HA 1,99750.92 0.33 - 2.54 Universal Uncemented / Mallory-Head -HA 2,795121.07 0.50 - 2.29 Müller Cemented 829307.22 3.80 - 13.73 Lubinus Cemented 2,253192.06 1.03 - 4.10 Exeter Cemented 2,001333.13 1.67 - 5.85 ZCA Cemented 1,06751.66 0.60 - 4.59 Charnley Cemented 1,681273.01 1.59 - 5.72

13. RESULTS: RESULTS: Cup; Any reason: N total N total N revised N revised RR RR 95 % CI 95 % CI Trilogy Uncemented -HA 5,1871601 Trilogy Uncemented +HA 653221.20 0.77 - 1.87 Universal Uncemented / Mallory-Head +HA 1,997480.82 0.60 - 1.14 Universal Uncemented / Mallory-Head -HA 2,795930.91 0.70 - 1.17 Müller Cemented 829531.41 1.02 - 1.94 Lubinus Cemented 2,253640.74 0.55 - 0.99 Exeter Cemented 2,001900.99 0.76 - 1.29 ZCA Cemented 1,067240.73 0.48 - 1.13 Charnley Cemented 1,681630.84 0.63 - 1.13

14. RESULTS: Stems; HA-coating VS. non HA-coating (all diagnosis) Adjusted RRs of revision; Endpoint: aseptic loosening; N total N total N revised N revised RR RR 95 % CI 95 % CI Uncemented - HA 5,482 5,482 15 15 1 Uncemented + HA 2,318 2,318 10.24 0.03 - 1.79

15. RESULTS: Stems; HA-coating VS. non HA-coating (all diagnosis) Adjusted RRs of revision; Endpoint: aseptic loosening; Endpoint: any reason; Same findings for: idiopathic arthrosis, age, gender, component type N total N total N revised N revised RR RR 95 % CI 95 % CI Uncemented - HA 5,482 5,482 15 15 1 Uncemented + HA 2,318 2,318 10.24 0.03 - 1.79 N total N total N revised N revised RR RR 95 % CI 95 % CI Uncemented - HA 5,482 5,4821691 Uncemented + HA 2,318 2,318500.86 0.63 - 1.18

16. RESULTS: Stems; Cemented VS. Uncemented (all diagnosis) Adjusted RRs of revision; Endpoint: aseptic loosening; N total N total N revised N revised RR RR 95 % CI 95 % CI Cemented 15,634 15,634 223 223 1 Uncemented - HA 5,482 5,482 15 150.22 0.13 - 0.37 Uncemented + HA 2,318 2,318 10.05 0.01 - 0.38

17. RESULTS: Stems; Cemented VS. Uncemented (all diagnosis) Adjusted RRs of revision; Endpoint: aseptic loosening; Endpoint: any reason; Same findings for: idiopathic arthrosis, age, gender, component type N total N total N revised N revised RR RR 95 % CI 95 % CI Cemented 15,634 15,634 223 223 1 Uncemented - HA 5,482 5,482 15 150.22 0.13 - 0.37 Uncemented + HA 2,318 2,318 10.05 0.01 - 0.38 Cemented 15,634 15,634 653 653 1 Uncemented - HA 5,482 5,482 169 1690.76 0.64 - 0.91 Uncemented + HA 2,318 2,318 50 500.68 0.51 - 0.91

18. RESULTS: RESULTS: Stem; Aseptic loosening: N total N total N revised N revised RR RR 95 % CI 95 % CI Exeter Cemented4,511201 Bi-metric Cemented3,425886.82 4.19 - 11.10 Bi-metric Uncemented +HA1,76210.25 0.03 - 1.87 Bi-metric Uncemented - HA3,55790.71 0.32 - 1.58 Lubinus SP II Cemented2,810221.87 1.02 - 3.42 CPT Cemented1,98260.90 0.36 - 2.24 Charnley Cemented1,237365.13 2.97 - 8.87

19. RESULTS: RESULTS: Stem; Any reason: N total N total N revised N revised RR RR 95 % CI 95 % CI Exeter Cemented4,5111361 Bi-metric Cemented3,4251952.00 1.61 - 2.49 Bi-metric Uncemented +HA1,762370.95 0.66 - 1.38 Bi-metric Uncemented - HA3,5571141.14 0.88 - 1.48 Lubinus SP II Cemented2,8101021.22 0.94 - 1.57 CPT Cemented1,982430.82 0.58 - 1.15 Charnley Cemented1,237591.33 0.98 - 1.81

20. CONCLUSION: Use of HA-coated implants was not associated with any overall reduced risk of revision compared with uncoated implants, in this medium term follow-up study of younger patients (<70). CONCLUSION: Use of HA-coated implants was not associated with any overall reduced risk of revision compared with uncoated implants, in this medium term follow-up study of younger patients (<70).

21. CONCLUSION: Use of HA-coated implants was not associated with any overall reduced risk of revision compared with uncoated implants, in this medium term follow-up study of younger patients (<70). Cemented implants as a group had higher revision rates due to aseptic loosening than cementless implants, but not unambiguously higher revision rates due to “any reason” than cementless implants in this study. CONCLUSION: Use of HA-coated implants was not associated with any overall reduced risk of revision compared with uncoated implants, in this medium term follow-up study of younger patients (<70). Cemented implants as a group had higher revision rates due to aseptic loosening than cementless implants, but not unambiguously higher revision rates due to “any reason” than cementless implants in this study.

22. CONCLUSION: Use of HA-coated implants was not associated with any overall reduced risk of revision compared with uncoated implants, in this medium term follow-up study of younger patients (<70). Cemented implants as a group had higher revision rates due to aseptic loosening than cementless implants, but not unambiguously higher revision rates due to “any reason” than cementless implants in this study. Müller, Exeter, and Charnley cups had the highest revision rates of the cups. Bi-metric Cemented, Charnley and Lubinus SP II stems had the highest revision rates for stems in this medium term follow-up study of younger patients (<70). CONCLUSION: Use of HA-coated implants was not associated with any overall reduced risk of revision compared with uncoated implants, in this medium term follow-up study of younger patients (<70). Cemented implants as a group had higher revision rates due to aseptic loosening than cementless implants, but not unambiguously higher revision rates due to “any reason” than cementless implants in this study. Müller, Exeter, and Charnley cups had the highest revision rates of the cups. Bi-metric Cemented, Charnley and Lubinus SP II stems had the highest revision rates for stems in this medium term follow-up study of younger patients (<70).