Factors Affecting Aseptic Loosening of 4750 Total Hip Arthroplasties: Multivariate Survival Analysis

Abstract and Background

Background: Total hip arthroplasty is a successful surgery, that fails at a rate of approximately 10% at ten years from surgery. Causes for failure are mainly aseptic loosening of one or both components partially due to wear of articular surfaces and partially to design. The present analysis aimed to identify risk factors and quantify their effects on aseptic failure.
Methods: Multivariate survival analysis was applied to 4,750 primary total hip arthroplasties performed between 1995 and 2000.
Results: The survival of the prosthesis is affected by gender, age, pathology, type of the prosthesis and skill of the. The worst conditions are male patients, younger than 40 years, affected by sequelae of congenital diseases, operated by a who performed less than 400 total hip artroplasty in the period. Furthermore, cemented cups and stems (less expensive) have a higher risk of failure compared with uncemented ones (more expensive).
Conclusion: The only variable that affects survival and that can be modified by is the type of prosthesis: a lower cost is associated to a higher risk. Results concerning the risk associated with cemented components are partially in disagreement with studies performed in countries where cemented prostheses are used more often than uncemented ones.

From a surgical point of view, total hip arthroplasty is a well-standardized operation that has proven to be very effective. However, failure can sometimes occur in the immediate postoperative period or even some years after. According to the NICE guidelines, for a hip prosthesis to be considered safe its mean survival rate should be at least 90% at ten years.^[1] Although the failure rate is low, it varies greatly and can be influenced by several factors, such as the type of prosthesis used and the patient's characteristics, and whereas the patient's characteristics are practically unchangeable, factors related to s and their choices can be modified. The literature includes numerous studies analysing factors that influence hip prosthesis failure, but they often concern small series of patients. Poon observed that weight and age influenced the outcome of total hip arthroplasty (THA) using cemented prostheses.^[2] Kobayashi studied a consecutive series of 293 primary cemented Charnley prostheses and found that rapid wear of polyethylene and abnormal geometry of the femoral medullary canal affect prosthesis survival.^[3] Kolundzic found that demographic factors explained only a minor part of the survival variability of 82 cementless acetabular cups.^[4]

The largest series concerned only patients treated using cemented prostheses. Among them Berry analysed 2000 primary Charnley prostheses at 25 years' follow-up and found that age, gender and underlying diagnosis affected long-term survivorship of both components.^[5] Dawson compared 598 cemented prostheses and found no significant differences between the performance of the two models.^[6] As clearly stated the weakness of all the long-term studies depends on the fact that they assess the success or failure of old technologies and designs.^[7] Comparison among prostheses with different fixation (cementless vs cemented) is limited to few clinical trials that indicate the better performance of cementless components.^[8,9,10]

Analyses performed on data from northern European registers only partially fill this gap since there is a clear-cut prevalence of cemented prostheses with metal-polyethylene couplings.

In fact, 93.1% of prostheses implanted in patients in Sweden between 1979 - 2004,^[11] and 80% of those used in Norway between 1987 - 2004^[12] were cemented. The figure is lower in Denmark, 49.8% between 1995 - 2004,^[13] and in Finland 55% from 1980 - 2003.^[14] The data collected for the UK were only for 2004, and although they included cemented prostheses in 49% of cases, they cannot be used for an effective analysis.^[15]

However, an analysis of the data from the Norwegian resister Furnes revealed that in over 53,000 operations some diseases (femoral neck fracture sequelae, congenital hip dysplasia, and rare diseases) represent risk factors for prosthesis survival.^[16]

When limiting the analysis to young osteoarthritic patients, Eskelinen found that age and gender influence the result.^[17]

The Danish register identified age and gender as confounding factors in the evaluation of prosthesis survival.^[13]

None of these analyses, due to the nature of the operations analyzed, considered the influence of the type of prosthesis fixation among the possible risk factors. Only when analysing the Finish data Visuri find that low age, male gender, uncemented prostheses and first 10 year-period of surgery were risk factors for loosening of the prostheses.^[18] Therefore, we analyzed the data of a series of patients with a minimum of six years' follow-up taken from the RIPO register (Register of Orthopedic Prosthetic Implantology), which includes cemented and uncemented prostheses, to determine the influence of patient characteristics, 's experience, and type of prosthesis used, on the outcome of the operation.

BMC Musculoskelet Disord © 2007 Bordini et al; licensee BioMed Central Ltd.
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Cite this: Factors Affecting Aseptic Loosening of 4750 Total Hip Arthroplasties: Multivariate Survival Analysis - Medscape - Jul 24, 2007.