Joshua rush nyu11/11/2023 ![]() This device has a measurement accuracy of ± 0.02 mm. 1), which we defined as the tapered male portion of the neck intended to engage the female taper of the femoral head. There is no universal standard for tapers, with considerable variability between or in some manufacturers for different stems.Ī series of measurements were taken to the nearest 0.1 mm with a digital caliper (Neiko Tools, Ontario, CA, USA) to characterize the taper geometry of the femoral trunnion (Fig. Some designs are proprietary to specific manufacturers and are given trade names. * Tapers can be described by either the taper angle (in degrees) or proximal and distal diameters (in mm). Care was taken to identify the correct taper design in these cases from the laser etchings or markings on the trunnion. Several stems analyzed underwent evolutionary changes in their taper design and therefore can have one of two possible taper geometries depending on the year of manufacture. Data regarding stem design and year of release were taken from manufacturer literature or one of two published implant atlases, which allowed determination that these stems were first released for clinical use between 19. The stem designs had 10 different taper geometries (Table 2), some of which are no longer in use. These represent approximately 25% of all stem designs with modular head-neck junctions indexed in a comprehensive implant atlas. The 85 stems represented designs from 16 different historical implant manufacturers, several of which have since merged (Table 1). Stems originally were implanted during a 22-year period from 1991 to 2012. Despite these design and manufacturing changes, including the introduction of numerous novel taper geometries, to our knowledge there has been no published documentation regarding how trunnions have changed with time and how these changes may have influenced biomechanical properties of the femoral trunnion.īy analyzing a large revision retrieval database of femoral stems released during a span of three decades, we asked: (1) how much does flexural rigidity vary among different taper designs (2) what is the contribution of taper geometry alone to flexural rigidity of the femoral trunnion and (3) how have flexural rigidity and taper length changed with time in this group of revised retrievals?Īn analysis of 85 unique femoral stem designs retrieved from two separate centers at the time of revision surgery was performed none was retrieved for a diagnosis related to a problem at the head-neck taper junction. There has been an ongoing evolution in trunnion design during the last several decades with implant manufacturers offering smaller trunnion designs with the rationale that an increased head-neck ratio may help prevent component impingement and reduce the risk of postoperative instability. Although taper corrosion involves a complex interplay of many factors, a previous study correlated higher flexural rigidity of the femoral trunnion with a decreased likelihood of corrosion. Increasing attention to local and systemic effects of wear debris and metallosis in patients with metal-on-metal devices led to the discovery that corrosion at the head-neck taper can be the cause for adverse local tissue reactions, even in patients without a metal-on-metal bearing surface. Recently, there has been renewed concern surrounding the potential for corrosion at the modular head-neck junction to cause early failure of modern hip implants. These changes curtailed initial concerns and helped lead to universal acceptance of these versatile implants. Because of early reports of corrosion, fretting, and implant fracture at the modular interface with associated biologic reactions, improvements in manufacturing and design subsequently were made, including making the femoral trunnions larger and more rigid. Concerns regarding the potential local and systemic effects of soluble and particulate debris from corrosion at the head-neck interface were expressed as these modular implants became available. Early retrieval analyses of femoral components attempted to identify the cause of corrosion, and although initially thought to be galvanic, an increasing body of literature points toward a mechanical etiology secondary to fretting and crevice-associated mechanisms of corrosion at the head-neck junction. Shortly after the introduction of modularity in THA, issues of fretting and corrosion at the modular head-neck junction were identified, and have since been well documented. Should revision arthroplasty be required, it also allows for easier surgical exposure and more potential options. Modularity at the head-neck junction of the femoral component in THA confers several advantages, including the ability to intraoperatively adjust head size, neck length, and choice of bearing surface after femoral fixation has been achieved.
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