Abstract
Total hip replacement procedures provide a very effective treatment modality for a wide range of diseases and injures to joints.
The annual number of primary and surgeries has been increasing. In Region Emilia Romagna, 4000000 inhabitants, 4587 total hip replacements (THA) were performed in 1997 and the number raised up to 5410 in 2002 ( + 18%). Emiarthoplasties were respectively 1914 and 2215 (+ 16%). Parallely number of revision raised from 550 to 938 (+71%).
In 2003 incidence of primary THAs in Emilia-Romagna is 107/100.000 inhabitants, higher than mean national value (76/100000).
Data of both primary and revision surgeries are collected by RIPO (Register for Orthopaedic Prosthetic Implantology) that started its activity in Rizzoli Institute on January 1990 and in Regione Emilia-Romagna on January 2000. The recording of data is done for each joint replacement operation and it consists on the identification of the patient, information about diagnosis or reason for re-operation, surgical approach, antibiotic and antithromboembolic prophylaxis, perioperative complications. Acetabular, femoral and head components are separately registered, on the basis of stickers with catalogue numbers provided by manufacturers with the implants. Fixation of the components is recorded as well.
Among the purposes of the Register there are the identification of early prosthesis failures, the information of surgeons on the outcome of their patients, the creation of a benchmarking tool for consultants and the speedy identification of relevant patients if a particular prosthesis or a particular batch gives cause for concern.
As for Scandinavian registers, revision is used as an end-point in the analyses. On this basis it is possible to calculate survival curves either aggregated or stratified.
By Cox multivariate analysis it has been ascertained that risk factors in total hip arthroplasties are represented by sex (females have lower risk than males), by age (younger than 40 are more at risk than 40–70s, and older than 70 are less at risk than 40–70s) and by pathology (fracture, coxites and Paget diseases have higher risk than coxarthrosis).
Basing on these data, survival analysis was normalized and the influence of articular coupling and fixation of the components on prosthesis outcome have been evaluated.
It resulted that failures are more likely to occur when metal on metal, or metal on polyethylene or ceramic on polyethylene devices rather than ceramic on ceramic implants are implanted.
Similarly cemented and hybrid THAs fail at higher rate than uncemented ones. All data are referred to a 11 years follow-up.
At present time Kaplan Meier analysis indicates a survival rate of total hip arthroplasties performed at Istituto Rizzoli of nearly 90% at ten years follow-up (9717 primary implants, 435 failures).
Main reasons for revisions are aseptic loosening of the cup (33%),aseptic loosening of both components (18%), aseptic loosening of the stem (17%), deep infection (7.9%),dislocation (7.6%),prosthesis fracture (3%) etc. Aseptic loosening represent, therefore, the most frequent cause for revision.
Results obtained at Istituto Rizzoli fit in the benchmarking set by the British NICE (National Institute for Clinical Excellence) that states that the revision rate should be of 10% or less at 10 years.
To improve these results attention should be pointed on new models: hip prosthesis technology is continually changing, with new designs and techniques being introduced. There is a need to strike a balance between using prostheses with published long-term performance data, and the need to develop and improve hip prosthesis. A solution to this problem could be to entrust reference clinical centers the evaluation of the effectiveness of any new prosthesis for at least three years, before opening free distribution in standard orthopaedic units,as suggested by NICE. Only models that reach the ‘entry benchmark’ in adequately sized, well conducted observational studies, can be implanted with a good safety. At present time it is unlikely that clinical evaluation data on long term effectiveness is required by Notified Body for ‘CE’ marking, unless new materials are involved in the manufacture. This happens despite the fact that even small changes to existing prostheses can have a significant impact on implant performance and revision rate.
Other factors than the already discussed can influence the surgery outcome, and among these the volume of operations performed in the hospital, the ability of the surgeon and its confidence with the technique, the compliance of the patient. Only an overall view of the situation will allow to reach the goal of reduction of need for revision of total hip arthroplasties.
The abstracts were prepared by Ms Grazia Gliozzi. Correspondence should be addressed to her at the Italian Orthopaedic Research Society, Laboratory for Pathophysiology, Instituti Ortopedici Rizzoli, University of Bologna, Bologna, Italy.
