VOL. 91-B, No. 12, DECEMBER 2009 1545  ANNOTATION Comparison of the performance of hip implants with data from different arthroplasty registers A. Migliore, M. R. Perrini, E. Romanini, D. Fella, A. Cavallo, M. Cerbo, T. Jefferson From Agenzia nazionale per i servizi sanitari regionali, Rome, Italy  A. Migliore, MSc, Researcher  M. R. Perrini, MSc, Researcher  D. Fella, Editorial Assistant  A. Cavallo, MSc, Researcher  M. Cerbo, MSc, Director  T. Jefferson, MD, Epidemiologist Agenzia Nazionale per io servizi sanitari regionali, Sez. ISS - Innovazione, Sperimantazione e Sviluppo, via Puglie, 23 - 00197 Rome, Italy.  E. Romanini, MD, Orthopaedic Surgeon Gruppo di Lavoro di Ortopedia Basata sulle prove di Efficacia, via Nicola Martelli, 3-00197, Rome, Italy. Correspondence should be sent to Dr A. Migliore; e-mail: migliore@agenas.it ©2009 British Editorial Society of Bone and Joint Surgery doi:10.1302/0301-620X.91B12. 22692 $2.00 J Bone Joint Surg [Br] 2009;91-B:1545-9. This study evaluated the feasibility of using published data from more than one register to define the performance of different hip implants. In order to obtain estimates of performance for specific types of hip system from different register, we analysed data from the annual reports of five national and one Italian regional register. We extracted the number of implants and rates of implant survival at different periods of follow-up. Our aim was to assess whether estimates of cumulative survival rate were comparable with data from registers from different countries, and our conclusion was that such a comparison could only be performed incompletely. Registers are important tools in evidence- based clinical practice. 1,2 Arthroplasty regis- ters collect data on primary and revision pro- cedures performed in a defined geographical area. They usually operate on a national basis, but some regional registers also exist. 3,4 In the Scandinavian countries arthroplasty registers have been functioning for some decades and have recently come together into the Nordic Arthroplasty Register Association (NARA). 5 Finland established its national arthroplasty register in 1980, 6 whereas in other countries, such as Australia, England and Wales, and New Zealand, the national arthroplasty register has been established in the last ten years. 7-9 A national joint registry was recently started in Malawi 10 and a hip registry is being formed in Italy and will start to operate in 2010. 11 In the field of hip arthroplasty, data from registers are used to produce reliable estimates of the performance of implant systems in terms of effectiveness and safety. However, because each national register is integrated into a par- ticular health system, its data are context spe- cific and reflect the standards of practice in that nation. Differences between countries, such as experience in cementing techniques, various implant designs, surgical approaches, regimens of rehabilitation or the general organisational and cultural features of the health system, may affect the outcome of the operation. 12 Some of the problems of interpretation of information in registers from different countries have recently been highlighted by Labek et al, 12 who concluded that to make data from differ- ent registers available and useful for surgeons, healthcare providers and patients, more inter- national co-operation is required. The aim of this study was to evaluate the feasibility of using published data from more than one register to define the performance of different hip implants. In order to obtain esti- mates of performance for specific types of sys- tems from different registers, we analysed data from the annual reports of five national and one Italian regional register. We extracted the number of implants and the survival rate at dif- ferent periods of follow-up, and assessed whether estimates of the cumulative survival rate were calculable using the data of registers from different countries. Materials and Methods The basis for our analysis was a report pro- duced for the first Italian Health Technology Assessment Programme. 13 The Ministry of Health commissioned the National Agency for Regional Healthcare (AGE.NA.S.) to assess whether the prostheses for total hip replace- ment which were available and used in Italy were employed on the basis of documented evi- dence of good performance. We used some of the findings of this report to conduct a further analysis on the comparison of performance of hip implants from data from different arthro- plasty registers. We carried out a PubMed 14 search using the terms ‘arthroplasty’ and ‘register’ to identify any paper using or discussing data from arthroplasty registers. We intentionally used a