CORRInsights®: Exchangeable Femoral Neck (Dual-Modular) THA Prostheses Have Poorer Survivorship than Other Designs: A Nationwide Cohort of 324,108 Patients

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While discussing THA in the 21st century, one of my mentors would often declare: “Modularity is an addiction.” The modularity evolution offered surgeons the possibility of assembling the components in situ, rather than implanting them as a monoblock or with a monolithic design. Many of us became swept up in the idea that we could uncouple fixation from variables such as length, offset, and version. It was believed that in the hands of a skilled surgeon, this technology could offer perfect restoration of our patients’ anatomy, minimizing the likelihood of uncommon complications such as instability, leg length inequality, and impingement. The wide adoption of dual-modular femoral stems—despite sparse data to support their utility—remains the most striking example of this “movement.”
As with most addictions, some negative consequences arose from our fascination with modularity. There was the recognition that even the time-tested modular head-neck junction was a source of clinically important metal corrosion debris, occasionally causing severe adverse local tissue reactions [3]. Shortly thereafter, the modular junction between the neck and body of the femoral stem caused similar problems with specific stem designs [4, 7], albeit at a much earlier time point and at a much higher prevalence than that seen at the modular head-neck junction [9]. These dual-modular designs were subject to other unique failure mechanisms such as implant fracture [16] and disassociation [15].
Owing to these case reports, case series, and recalls of specific implant designs, dual-modular stems have mostly fallen out of favor. However, many designs still remain on the market and are available for use today. Several studies have demonstrated high complication rates with specific dual modular stem designs [9, 11, 14], yet it remains unclear whether this high failure rate is isolated to a handful of specific designs, or if it extends to the entire class of dual-modular stems.
In the current study, Colas and colleagues report the survivorship results of dual modular stems compared to monolithic designs in a registry analysis of 324,108 patients who underwent THA in France between 2009 and 2012. They found that dual-modular THAs had lower survivorship than their monolithic counterparts. This should lead us to question the routine use of dual-modular stems.
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