The innovation trap: modular neck in total hip arthroplasty (original) (raw)

2017, DOAJ (DOAJ: Directory of Open Access Journals)

Background: Innovations play a key role in the success of orthopeadic surgery. However, even minor modifications in the established concepts and designs may result in disasters. We face an endemic of modular femoral neck failures occurring in fully modular total hip arthroplasty (24 of approx.4000 implanted), which has been popular in Slovenia for the last 20 years. Its most unfortunate consequences challenge us to seriously address this problem. The aim of this report was to analyse the volume, and the causes of the problem, on the one hand, and to propose possible solutions, on the other. Methods: The literature was searched for problems associated with Profemur Z fully-modular femoral stem, made of titanium alloy (Ti6Al4V)or earlier versions with the same taper-cone design.The available hip arthroplasty registries were used to determine failure rates associated with the above mentioned design. The mechanisms of failure were studied in order to get in-depth understanding of this hip reconstruction device. Results: Since 2010, several case reports on catastrophic modular femoral neck fractures of Profemur Z have been published. In Slovenia the first case was described in 2012. The first two large series with modular femoral neck fractures were reported in 2016. The Australian Joint Replacement Registry was the first to discover elevated revision rates due to fractures of this hip reconstruction system. In 2010, the Agency for Medicinal Products and Medical Devices of the Republic of Slovenia (JAZMP) received the first 2 reports on Profemur Z modular neck complications, submitted by foreign institutions. The first Slovenian report dates back to 2012, and altogether 7 reports from Slovene hospitals had been received by December 2016. Corrosion at the neck-taper interface, where two equal or different materials are subject to constant wear in the presence of body fluids, was assumed to be responsible for the unacceptably high failure rates. Conclusions: Manufacturers are responsible for producing and marketing safe devices. However, orthopaedic surgeons should carefully monitor all innovations for any adverse effects. JAZMP took appropriate measures only after receiving urgent field safety corrective notice from the manufacturer in 2015, stating that all lots of long modular necks made from cobalt-chromium alloy should be withdrawn. It should be noted here that the regulatory agency of the Republic of Slovenia was not receiving vigilance reports as appropriate, and was thus unaware of the dimension of this problem. A national arthroplasty registry would have most probably alerted the orthopaedic community to this questionable innovation earlier. Regulatory bodies should set up such a registry for the benefit of our patients as soon as possible.