INCIDENCE OF IMPLANT FRACTURES AFTER TOTAL HIP ARTHROPLASTY

Abstract

Background: Implant fractures are complications that have a great impact on the patient’s quality of life after total hip arthroplasty. Nevertheless their occurrence is often considered as rare in clinical practice. We compared incidences of implant fractures in various datasets in order to calculate the risk of a fracture and assess the quality of these datasets for such evaluations.

Methods: In a structured literature analysis based on a standardised methodology the incidence of reoperations was evaluated comparing clinical studies published in Medline-listed journals and annual reports of National Arthroplasty Registers worldwide. Case reports and experimental studies were not considered.

Results: The majority of clinical studies are monocentre trials. The publications comprise a cumulative number of 72,571 stems with 234 stem fractures, 73,743 cups with 191 component fractures, and 16,381 ceramic heads with 44 fractures. A survey among the members of the American Association of Hip and Knee Surgeons covered 64,483 primary operations, hence including a similar number of primary cases as all monocentre studies together. This dataset involves 355 implant fractures.

By contrast, worldwide Register data refer to 733,000 primary operations, i.e. approximately 10 times as many as sample-based datasets.

In general, sample-based datasets present higher revision rates than register data. The deviations are high, with a maximum factor of 64 for hip stems. Whereas the AAHKS survey exhibits lower deviations than the monocentre trials, they are still too high for this data collection tool being considered as reliable and safe to provide valid data for general conclusions.

The incidence of implant fractures after total hip arthroplasty in pooled worldwide arthroplasty register datasets is 304 fractures per 100.000 implants. In other words, one out of 323 patients has to undergo revision surgery due to an implant fracture after THA in their lifetime.

Conclusion: For general assessments in the context of implant fractures, register data have the highest value. Clinical studies, which often focus on a particular implant, are of very limited value for global conclusions. Structured surveys produce more reliable data than clinical studies and are superior to monocentre trials. However, the AAHKS survey presents data that also show considerable differences to data from registers.

For the detection of rare, but severe complications like implant fractures sample-based studies achieve the goal of providing accurate figures only to a very limited extent, even if the samples are large. Here, too, comprehensive national arthroplasty registers are the most suitable tool to identify such incidents and calculate reliable figures.

Contrary to the prevalent opinion, implant fractures still are a relevant problem in arthroplasty.