The etiology of clinically relevant trunnion corrosion remains to be fully understood, but appears to be multifactorial with synergy among implant-based, surgeon-based, and patient-based factors.Trunnion corrosion causing an adverse local tissue reaction (ALTR) typically manifests as delayed onset o

Trunnionosis in Total Hip Arthroplasty.

Background Taper corrosion in total hip arthroplasty for bearings with metal heads against polyethylene has developed from an anecdotal observation to a clinical problem. Increased taper wear and even gross taper failure have been reported for one particular design. It is hypothesized that corrosion of the female head taper results in taper widening, allowing the cobalt-chromium head to turn on the stem and wear down the softer titanium alloy by abrasive wear, ultimately causing failure. The purpose of this study is to investigate the time course of this process and the general role of taper dimensions and material in this problem. Methods Retrieved cobalt-chromium alloy heads (n = 30, LFIT; Stryker, Mahwah, NJ) and Ti-12Mo-6Zr-2Fe (TMZF) stems (n = 10, Accolade I; Stryker) were available for analysis. Taper material loss was determined using three-dimensional coordinate measurements and scanning. The pristine tip clearance between head and stem was analytically determined. The influence of taper material and taper size on taper deformation and micromotion was investigated using a finite element model. Results Material loss at the head taper increased with time in situ up to a volume of 20.8 mm3 (P Conclusion A 11/13 TMZF taper design with 36-mm head diameters bears a higher risk for corrosion than larger tapers made from stiffer materials. Failures of this combination are not restricted to the head sizes included in the recall. Patients with this implant combination should be closely monitored.

/pdf/head-taper-corrosion-causing-head-bottoming-out-and-3xjnuo5kfx.pdf

Head Taper Corrosion Causing Head Bottoming Out and Consecutive Gross Stem Taper Failure in Total Hip Arthroplasty

Background Taper corrosion has been identified to be a major concern in total hip replacement during the past years. So far, the mechanisms that lead to taper corrosion in modular taper junctions are not fully understood. However, it has been shown that corrosion is also influenced by the geometry and topography of the taper, and these parameters vary among the implant manufacturers. The purpose of this study was to investigate the variations of common stem and head tapers regarding design and surface characteristics. Methods An analysis of selected commercially available 12/14 stem and head tapers was performed. As geometrical parameters, the taper angle, the opening taper diameter and the taper length were measured using a coordinate measuring machine. Several topographical parameters were determined using a tactile roughness measurement instrument. Results Although all investigated tapers are so-called 12/14 tapers, this study showed that the stem and head tapers differ among the manufacturers. The stem tapers were clearly different in both geometry and topography, and the range in variation of the topographical parameter was greater than it was for the geometrical parameter. In contrast, the head tapers were different in their geometry, though not in topography. Conclusion Ultimately, this study provides an overview on the characteristics and variations of modular hip taper connections and additionally, a new classification system regarding the surface finish is presented. These findings could be further considered in experimental corrosion or retrieval studies.

Same Same But Different? 12/14 Stem and Head Tapers in Total Hip Arthroplasty

Background Dual-mobility (DM) total hip arthroplasty (THA) systems are designed to increase stability while potentially avoiding problems associated with large femoral heads. Complications of these systems are not yet fully understood. This study aims at characterizing in vivo performance of DM hip systems and assessing modes of clinical failure. Methods Under an institutional review board–approved implant retrieval protocol, 18 DM THA systems from 17 patients were included. Implants were graded at the head-neck junction for fretting and corrosion based on the system of Goldberg et al. Components were also macroscopically examined for different damage modes. Demographics and surgical data were collected from medical records, and radiographs were assessed for component positioning. Data were analyzed through Spearman rank-order correlation and Mann-Whitney U-tests, with α = 0.05. Results The average length of implantation was 13.4 months with mild to moderate fretting corrosion damage. Polyethylene (PE) liners exhibited edge deformation, scratching, and pitting damage. Metallic components exhibited burnishing and scratching damage. Summed fretting and corrosion scores were strongly correlated (ρ = 0.967, P Conclusion These findings demonstrate that dual-mobility THA systems may be susceptible to the same fretting and corrosion damage observed in traditional modular THA systems. Future studies are needed to confirm these results and clinical significance.

Fretting and Corrosion Damage of Retrieved Dual-Mobility Total Hip Arthroplasty Systems.

/pdf/medical-device-materials-v-4tugc6smem.pdf

Medical Device Materials V

Background Previous studies identified imprinting of the stem morphology onto the interior head bore, leading researchers to hypothesize an influence of taper topography on mechanically assisted crevice corrosion. The purpose of this study was to analyze whether microgrooved stem tapers result in greater fretting corrosion damage than smooth stem tapers. Methods A matched cohort of 120 retrieved head-stem pairs from metal-on-polyethylene bearings was created controlling for implantation time, flexural rigidity, apparent length of engagement, and head size. There were 2 groups of 60 heads each, mated with either smooth or microgrooved stem tapers. A high-precision roundness machine was used to measure and categorize the surface morphology. Fretting corrosion damage at the head-neck junction was characterized using the Higgs-Goldberg scoring method. Fourteen of the most damaged heads were analyzed for the maximum depth of material loss and focused ion beam cross-sectioned to view oxide and base metal. Results Fretting corrosion damage was not different between the 2 cohorts at the femoral head ( P  = .14, Mann-Whitney) or stem tapers ( P  = .35). There was no difference in the maximum depths of material loss between the cohorts ( P  = .71). Cross-sectioning revealed contact damage, signs of micro-motion, and chromium-rich oxide layers in both cohorts. Microgroove imprinting did not appear to have a different effect on the fretting corrosion behavior. Conclusion The results of this matched cohort retrieval study do not support the hypothesis that taper surfaces with microgrooved stems exhibit increased in vivo fretting corrosion damage or material release.

Do Stem Taper Microgrooves Influence Taper Corrosion in Total Hip Arthroplasty? A Matched Cohort Retrieval Study

Ultrasonic cleaning is often used as part of the manufacturing process of small medical devices such as guide wires and vascular implants. Ultrasonic cleaning at frequencies close to the natural frequency of the device can result in resonance, resulting in significant mechanical damage and possibly premature failure. This paper provides case studies of ultrasonic cleaning-induced fatigue and corresponding failures in small medical devices. Preventative measures, including analytical tools such as finite element analysis (FEA), to ensure that ultrasonic cleaning frequencies do not result in resonance and stresses sufficient to cause fatigue damage are also discussed.

Ultrasonic Cleaning-Induced Failures in Medical Devices

Accelerated Testing Of Active Implantable Medical Devices

The hardware used for plumbing assemblies play an important role in modern home, business, and industrial systems. Engineered plumbing hardware made from metals allow for an extensive network of plumbing assemblies accommodating complex designs which facilitate product and installation effectiveness, in addition to maintaining cost efficiency. Examples of plumbing hardware include fittings, valves, drains, fixtures, pipes, and so on. These materials are often subjected to a range of environments dependent on local water chemistry as well as varying service environments and installation techniques. Given the vast number of components in use failures do occur, often as a result of extreme service conditions or inappropriate installation techniques. Understanding the failure mechanisms associated with plumbing hardware and their assemblies is an important step in material and design optimization for future development. In view of that, this paper provides a range of plumbing component failure case studies for potable and non-potable water systems.

Plumbing Hardware Failure Analyses

The tools used during surgical procedures are an important component to clinical success. Innovative surgical tool designs have enabled more intricate and less-invasive procedures resulting in advanced procedures, reduced patient pain, and recovery time. Examples of surgical tools include drills, catheters, needles, cannulas, scissors, and so on. These tools are often subjected to corrosive environments, high stresses, high loading frequencies, sterilization, and/or cleaning procedures. Given the extreme use conditions to which surgical tools can be exposed, and the potential for misuse, these devices can and do fail. These failures often occur during a surgical procedure and therefore can compromise clinical success. Understanding how and why failures occur is an important first step to prevent their occurrence. Accordingly, this paper provides selected surgical tool failure case studies.

Eric P. Guyer

Papers

Do Stem Taper Microgrooves Influence Taper Corrosion in Total Hip Arthroplasty? A Matched Cohort Retrieval Study

Ultrasonic Cleaning-Induced Failures in Medical Devices

Accelerated Testing Of Active Implantable Medical Devices

Plumbing Hardware Failure Analyses

Surgical Tool Failure Analyses