Early Detection of Fretting Corrosion in Hip Replacement by Acoustic Emission Non-Invasive Technique.

The present study aimed to investigate the feasibility of using acoustic emission (AE) as a detection method for identifying failure mechanisms at the modular junction interface in total hip replacements (THRs) subjected to fretting corrosion. The experimental setup involved simulating fretting corrosion using a Ti6Al4V disc representing the femoral neck and a ZrO2 pin representing the femoral head. Mechanical testing provided insights into the wear and frictional behavior occurring at the modular junction interface. The results revealed that for all three potential conditions, a fretting condition of partial slip was observed. These findings highlight the importance of understanding the mechanical interactions and their influence on the overall performance and longevity of THRs. Electrochemical analysis shed light on the corrosion behavior under different potentiostatic conditions. High potentials in the anodic condition led to increased corrosion and ion transfer due to the breakdown of the passive oxide layer. Conversely, the cathodic potential condition exhibited a regrowth of the passive oxide layer, protecting the Ti6Al4V surface from further corrosion. The mid-range corrosion potential condition showed a dynamic equilibrium between corrosion and passivation processes. These electrochemical insights enhance our understanding of the mechanisms involved in fretting corrosion. The AE data proved to be promising in detecting and monitoring the onset and progression of failure mechanisms. The AE signals exhibited distinctive patterns that correlated with the severity of fretting corrosion. Notably, the hit driven data results, derived from AE signals, demonstrated the ability to differentiate between different levels of fretting conditions. This suggests that AE can serve as a valuable diagnostic tool for early detection and continuous monitoring of implant failure in THRs.

Gross Taper Failure and Fracture of the True Neck in Total Hip Arthroplasty: Retrieval Scanning Electron Microscope Analysis.

Background and objectives: wear and corrosion can lead to the gross failure of the Morse taper junction with the consequent fracture of the true neck of the prosthetic stem in hip arthroplasty. Materials and Methods: 58-year-old male patient, with a BMI of 38 kg/m2. Because of avascular necrosis, in 2007, a metal-on-metal total hip arthroplasty was implanted in him, with a TMZF stem and a Co-Cr head. In December 2020, he complained of acute left hip pain associated with the deterioration of his left leg and total functional impairment, preceded by the crunching of the hip. X-rays and CT scan showed a fracture of the prosthetic neck that necessitated prosthetic revision surgery. A Scanning Electron Microscope (SEM) analysis of the retrieved prosthetic components was conducted. Results: Macroscopically, the trunnion showed a typical bird beak appearance, due to a massive material loss of about half of its volume. The gross material loss apparently due to abrasion extended beyond the trunnion to the point of failure on the true neck about half a centimeter distal from the taper. SEM analysis demonstrated fatigue rupture modes, and the crack began close to the neck's surface. On the lateral surface, several scratches were found, suggesting an intense wear that could be due to abrasion. Conclusions: The analysis we conducted on the explanted THA showed a ductile rupture, began close to the upper surface of the prosthetic neck where the presence of many scratches had concentrated stresses and led to a fatigue fracture.

Larger-diameter trunnions and bolt-reinforced taper junctions are associated with less tribocorrosion in reverse total shoulder arthroplasty.

BACKGROUND: Morse taper junction tribocorrosion is recognized as an important failure mode in total hip arthroplasty. Although taper junctions are used in almost all shoulder arthroplasty systems currently available in the United States, with large variation in design, limited literature has described comparable analyses of taper damage in these implants. In this study, taper junction damage in retrieved reverse total shoulder arthroplasty (RTSA) implants was assessed and analyzed. METHODS: Fifty-seven retrieved RTSAs with paired baseplate and glenosphere components with Morse taper junctions were identified via database query; 19 of these also included paired humeral stems and trays or spacers with taper junctions. Components were graded for standard damage modes and for fretting and corrosion with a modified Goldberg-Cusick classification system. Medical records and preoperative radiographs were reviewed. Comparative analyses were performed assessing the impact of various implant, radiographic, and patient factors on taper damage. RESULTS: Standard damage modes were commonly found at the evaluated trunnion junctions, with scratching and edge deformation damage on 76% and 46% of all components, respectively. Fretting and corrosion damage was also common, observed on 86% and 72% of baseplates, respectively, and 23% and 40% of glenospheres, respectively. Baseplates showed greater moderate to severe (grade ≥ 3) fretting (43%) and corrosion (27%) damage than matched glenospheres (fretting, 9%; corrosion, 13%). Humeral stems showed moderate to severe fretting and corrosion on 28% and 30% of implants, respectively; matched humeral trays or spacers showed both less fretting (14%) and less corrosion (17%). On subgroup analysis, large-tapered implants had significantly lower summed fretting and corrosion grades than small-tapered implants (P < .001 for both) on glenospheres; paired baseplate corrosion grades were also significantly lower (P = .031) on large-tapered implants. Factorial analysis showed that bolt reinforcement of the taper junction was also associated with less fretting and corrosion damage on both baseplates and glenospheres. Summed fretting and corrosion grades on glenospheres with trunnions (male) were significantly greater than on glenospheres with bores (female) (P < .001 for both). CONCLUSIONS: Damage to the taper junction is commonly found in retrieved RTSAs and can occur after only months of being implanted. In this study, tribocorrosion predominantly occurred on the taper surface of the baseplate (vs. glenosphere) and on the humeral stem (vs. tray or spacer), which may relate to the flexural rigidity difference between the titanium and cobalt-chrome components. Bolt reinforcement and the use of large-diameter trunnions led to less tribocorrosion of the taper junction. The findings of this study provide evidence for the improved design of RTSA prostheses to decrease tribocorrosion.

Evaluating trunnionosis in modular anatomic shoulder arthroplasties: a retrieval study.

BACKGROUND: Shoulder arthroplasty procedures are widely indicated, and the number of shoulder arthroplasty procedures has drastically increased over the years. Rapid expansion of the utilization of reverse total shoulder arthroplasty has outpaced the more modest growth of anatomic total shoulder arthroplasty (aTSA) while shoulder hemiarthroplasty (HA) has trended down. Recently, shoulder prostheses have transitioned to increasingly modular systems offering more individualized options with the potential for decreased pain and increased range of motion. However, increased primary procedures has resulted in increased revision surgeries, with one potential cause being fretting and corrosion damage within these modular systems. METHODS: Following institutional review board approval, 130 retrieved aTSA and 135 HA explants were identified through database query. Humeral stem and head components were included in all 265 explants, whereas 108 included polyethylene glenoid liner components. All explanted components were macroscopically evaluated for standard damage modes, and taper junctions were microscopically examined for fretting/corrosion using a modified Goldberg-Cusick classification system that was 4-quadrant graded for both the male and female component. Medical records were reviewed for patient demographics and surgical information. RESULTS: In this series, 158 of explants were from female patients (male = 107), and 162 explants were from the right shoulder. Average age at implantation was 61 years (range: 24-83), average age at explanation was 66 years (range, 32-90), and average duration of implantation was 61.4 months (range, 0.5-240). Scratching, edge deformation, and burnishing were the most commonly observed standard damage modes. Of the 265 explants, 146 had a male stem component vs. 118 with a female stem component. Average summed fretting grades on male and female stem components were 8.3 and 5.9, respectively (P < .001). Average summed corrosion grades for male and female stem components were 8.2 and 6.2, respectively (P < .001). Wider male tapers (>11 mm) showed significantly less fretting and corrosion (P < .001). Lastly, mismatched metal compositions between the head and stem components showed greater fretting and corrosion damage (P = .002). CONCLUSION: In this series of 265 aTSA and HA explants, there was substantial damage present on the explanted components. All components demonstrated macroscopic damage. In this retrieval study, small-tapered male stems with small, thin female heads and mismatched metal composition between components were risk factors for increased implant wear. As shoulder arthroplasty volume increases, optimizing design is paramount for long-term success. Additional work could determine the clinical significance of these findings.

Are Corrosion and Material Loss a Threat for Titanium-Titanium Tapers in Total Hip Arthroplasty Modular Acetabular Components?

BACKGROUND: Extensive research has reported on fretting corrosion and material loss for a variety of metal taper interfaces in orthopedic devices. For modular acetabular shell-liner constructs, the interfaces studied thus far have consisted of mixed-metal pairings, and the risk of fretting corrosion and material loss for the all-titanium (Ti) shell-liner taper junction in one ceramic-on-ceramic (COC) design remains poorly understood. We asked: do Ti shell-liner taper interfaces in COC total hip arthroplasty devices show in vivo evidence of (1) fretting and/or corrosion, and (2) quantifiable potential material loss? METHODS: We examined 22 shell-liner pairs and 22 single liners from retrieved COC components. The taper interface surfaces were assessed for fretting corrosion using a semiquantitative scoring method and imaged with scanning electron microscopy. A subcohort of components was measured with a coordinate measuring machine, and volumetric material loss and maximum wear depth were calculated. RESULTS: Fretting corrosion at the taper interfaces was minimal to mild for 95% of liners and 100% of shells. Imaging revealed fretting marks within a band of corrosion on some implants and evidence of corrosion not in the proximity of mechanical damage. Estimated material loss ranged from 0.2 to 1.3 mm3 for liners, and 0.5 to 1.1 mm3 for shells. Maximum wear depth for all components was 0.03 mm or less. CONCLUSIONS: Our results indicate that, compared to other taper junctions in total joint arthroplasty, the risk of corrosion and material loss may be minimal for Ti shell-liner interfaces.

Long-term survivorship of an exchangeable-neck hip prosthesis with a Ti-alloy/Ti-alloy neck-stem junction.

INTRODUCTION: Breakage of exchangeable-neck (EN) and adverse local tissue reactions (ALTRs) to neck-stem junction (NSJ) damage products are responsible for increasing the revision rate of EN hip prostheses. We investigated the survivorship of an EN hip prosthesis including a NSJ with both components made of titanium alloy (Ti-alloy/Ti-alloy) to assess whether, and to what extent, EN breakage and NSJ damage affected implant survivorship. MATERIALS AND METHODS: Using data from a hip replacement registry, we determined survivorship of 2857 EN prostheses. Long-offset configurations of head and EN were implanted in heavy (> 90 kg) patients only in 23 hips. We investigated under which conditions EN breakages or ALTRs occurred. We also measured titanium (Ti) and vanadium (V) blood concentrations in 24 patients with a unilateral well-working prosthesis. RESULTS: The 17-year survival rates for any reason and aseptic loosening of any component were 88.9% (95%CI 87.5-90.1; 857 hips at risk) and 96.9% (95%CI 96.0-97.6), respectively. There were two cases of EN breakage and one case of ALTR (metallosis), due to rim-neck impingement, out of 276 revisions. After an average period of 9.8 years (range 7.8-12.8 years), the maximum Ti and V blood concentrations in patients with a well-working prosthesis were 5.0 µg/l and 0.16 µg/l, respectively. CONCLUSION: The present incidence of EN breakage or ALTR is lower than those reported in other studies evaluating EN hip prosthesis survivorship. This study suggests that (i) the risk of EN breakage is reduced by limiting the use of long-offset configurations in heavy patients and (ii) Ti-alloy/Ti-alloy NSJ damage products do not promote ALTR nor significantly alter the rate of implant loosening. Since design decisions and implant configuration determine the NSJ strength, the NSJ strength in working conditions must be thoroughly investigated to proper define the clinical indications for any EN design.

Assessing Taper Geometry, Head Size, Head Material, and Their Interactions in Taper Fretting Corrosion of Retrieved Total Hip Arthroplasty Implants.

BACKGROUND: Decreased fretting and corrosion damage at the taper interface of retrieved ceramic-on-polyethylene total hip arthroplasty (THA) implants has been consistently reported; however, resultant fretting corrosion as a function of femoral head size and taper geometry has not been definitively explained. METHODS: Eight cohorts were defined from 157 retrieved THA implants based on femoral head composition (n = 95, zirconia-toughened alumina, ZTA vs n = 62, cobalt-chromium alloy, CoCr), head size (n = 56, 32mm vs n = 101, 36mm), and taper geometry (n = 84, 12/14 vs n = 73, V40). THA implants were evaluated and graded for taper fretting and corrosion. Data were statistically analyzed, including via a 23 factorial modeling. RESULTS: Factorial-based analysis indicated the significant factors related to both resultant (summed) fretting and corrosion damage were head material and taper geometry; head material-taper geometry interaction was also a significant factor in resultant corrosion damage. Lower rates of moderate-to-severe fretting and corrosion damage were exhibited on ZTA heads (ZTA = 13%, CoCr = 38%), smaller heads (32mm = 18%, 36mm = 26%), and 12/14 tapers (12/14 = 13%, V40 = 35%). ZTA+32mm heads demonstrated the lowest rates of moderate-to-severe fretting and corrosion damage (12/14 = 2%, V40 = 7%), whereas CoCr heads with V40 tapers demonstrated the greatest rates of moderate-to-severe damage (32mm = 47%, 36mm = 59%). CONCLUSION: In this series, retrieved implants with ZTA, 32-mm heads paired with 12/14 tapers exhibited lower rates of moderate-to-severe damage. Factorial analysis showed head material, taper geometry, and their interactions were the most significant factors associated with resultant damage grades. Isolating implant features may provide additional information regarding factors leading to fretting and corrosion damage in THA. LEVEL OF EVIDENCE: IV (case series).

Fretting Corrosion, Third-Body Polyethylene Damage, and Cup Positioning in Primary vs Revision Dual Mobility Total Hip Arthroplasty.

BACKGROUND: Dual mobility (DM) articulations were introduced for total hip arthroplasty to reduce the risk of instability for patients who have a high risk of dislocation. The use of DM constructs in both primary and revision total hip arthroplasty has been steadily increasing, leading to concerns regarding potential risks of fretting corrosion, polyethylene wear, metal release, and failure due to component positioning. METHODS: A total of 56 retrieved DM constructs were collected. The inner and outer polyethylene liner surfaces were assessed for 7 damage mechanisms, and fretting corrosion was evaluated for the femoral stem, head, and modular liner. Three polyethylene liners with the greatest amounts of embedded debris were examined using scanning electron microscopy. Energy-dispersive X-ray spectroscopy was used to determine the elemental content of the debris. Acetabular cup orientation was analyzed radiographically using the EBRA (Einzel-Bild-Roentgen-Analyse) method. RESULTS: The devices were revised most frequently for infection (36%), loosening (21%), and instability/dislocation (18%). The most common polyethylene damage mechanisms were scratching, pitting, burnishing, and embedded debris, and no difference in total damage was found between primary and revision cases. Scanning electron microscopy/energy-dispersive X-ray spectroscopy revealed that debris morphology and composition were consistent with porous titanium coating, resulting from cup loosening or broken screws and augments. A total of 71% and 50% of the constructs were determined to be within the Lewinnek safe zone for inclination and anteversion, respectively. CONCLUSION: The most notable mechanisms of surface damage were due to third-body debris, especially for the polyethylene surfaces which articulate against cobalt-chromium femoral heads and acetabular liners. Scratching of the femoral head and the metal liner from this debris may support the clinical use of ceramic for DM bearing surfaces in the future.

Fretting-corrosion of CoCr-alloys against TiAl6V4: The importance of molybdenum in oxidative biological environments.

Periprosthetic fluids often contain reactive oxygen species, including H2O2, that are generated during inflammatory processes. Here, we investigated the fretting-corrosion behavior of CoCrX-alloys (X = Mo, Fe) in a complex protein-containing lubricant, with and without the addition of H2O2. Given the known protective role of molybdenum as an alloying element in metal degradation, we considered its effects by designing a two-way factorial experiment. The aim of the study was to investigate tribocorrosive mechanisms in modular joints of knee and hip prostheses. A previously described test-rig was used to run fretting corrosion tests of CoCrX-alloys with (X=Mo) and without (X=Fe) molybdenum against TiAl6V4 in bovine calf serum (BCS) with and without a physiological relevant H2O2 level (3 mM) in gross slip mode (4 Hz, ±50 µm, pmax=0.18 GPa, 37 °C, 50,000 cycles). Two CoCr-pins were pressed against a cylindrical TiAl6V4-rod, forming a line contact. Normal and frictional forces, the displacement, and the open circuit potential (OCP) were measured and recorded continuously. The dissipated frictional work was independent of alloy composition. The addition of H2O2 lowered the dissipated frictional work and increased wear, and this was significant in the absence of Mo. The mean OCP value was lower with Mo-containing than with Mo-free alloy in both pure BCS (p = .042), and BCS ± H2O2 (p < .0005). The wear scar was deeper for the Mo-free alloy, and this was significant (p = .013) in the presence of H2O2. These findings suggest a marked weakening of the passive film in the presence of H2O2, which is mitigated by the availability of Mo.

Patients Following Revision Total Hip Arthroplasty With Modular Dual Mobility Components and Cobalt-Chromium Inner Metal Head are at Risk of Increased Serum Metal Ion Levels.

BACKGROUND: Modular dual-mobility (MDM) total hip arthroplasty (THA) is designed with a cobalt-chromium liner inserted into a titanium acetabular component. The purpose of this study is to investigate the potential risks for fretting corrosion at this junction, by measuring serum metal ions, after MDM acetabular revision. METHODS: Thirty-seven patients with well-functioning revision THAs participated in a cross-sectional study at mean 5.1 (2-10) years after surgery. All received a trabecular titanium MDM acetabular component. The serum levels of cobalt and chromium were measured using mass spectrometry. RESULTS: The mean values of chromium and cobalt were 2.08 µg/L (95% confidence interval 0.9-3.2, range 0.02-11.8) and 1.99 µg/L (95% confidence interval 0.81-3.17, range 0.07-16.05), respectively. Eleven patients (29, 7%) had ion levels above the normal range, with 6 (16.2%) above 5 µg/L and 5 (13.5%) between 1 and 5 µg/L. A significant correlation was found between an elevated serum metal ion level and University of California Los Angeles score (P = .016). CONCLUSION: We conclude that serum metal level elevation may occur secondary to metal debris resulting from corrosion of the index MDM THA. This potential risk should be included in the decision-making process when dealing with revision arthroplasty in young and active patients.

On the Role of Contact and System Stiffness in the Measurement of Principal Variables in Fretting Wear Testing.

In this work, the role of the contact stiffness in the measurement of principal variables in fretting wear tests is assessed. Several fretting wear tribometers found in the literature, including one developed by the authors, are analysed and modelled using numerical methods. The results show the importance of the tribosystem stiffness and tangential contact stiffness in the displacement sensor calibration and in the correct numerical modelling of fretting wear tests, especially for flat-to-flat contact configuration. The study highlights that, in most cases, direct comparisons between fretting results with severe wear obtained with different tribometers cannot be performed if the contact stiffness is not properly considered during the development of the experiments.

Does Taper Design Affect Taper Fretting Corrosion in Ceramic-on-Polyethylene Total Hip Arthroplasty? A Retrieval Analysis.

BACKGROUND: Ceramic-on-polyethylene (CoP) implants have exhibited lower fretting and corrosion scores than metal-on-polyethylene implants. This study aims at investigating the effect of taper design on taper corrosion and fretting in modular CoP total hip arthroplasty (THA) systems. METHODS: Under an institutional review board--approved protocol, a query of an implant retrieval library from 2002 to 2017 identified 120 retrieved CoP THA systems with zirconia toughened alumina femoral heads. Femoral stem trunnions were visually evaluated and graded for fretting, corrosion, and damage at the taper interface. Medical records were reviewed for patient demographics and implant characteristics. Data were statistically analyzed using Spearman correlation and rank-sum tests with a Dunn's post hoc test, with a significance level of α = 0.05. RESULTS: Four different taper designs were evaluated: 11/13 (n = 18), 12/14 (n = 53), 16/18 (n = 21), and V40 (n = 28). There were no statistically significant demographic differences between taper groups for duration of implantation, laterality, patient age, and patient sex, but patients with 16/18 tapers had a higher body mass index than V40 tapers (P = .012). Duration of implantation had a weak positive correlation with both trunnion fretting (ρ = 0.224, P = .016) and corrosion (ρ = 0.253, P = .006). Summed fretting and corrosion scores were significantly greater on the V40 and 16/18 tapers compared with the 12/14 tapers (all P ≤ .001). CONCLUSION: Taper fretting and corrosion were observed in CoP THA implants and were greatest with V40 and 16/18 tapers and lowest with 12/14 tapers. Differences in taper design characteristics may lead to greater micromotion at the taper-head interface, leading to increased fretting and corrosion.

Design, Material, and Seating Load Effects on In Vitro Fretting Corrosion Performance of Modular Head-Neck Tapers.

BACKGROUND: The short-term corrosion and micromechanical behavior of 32 unique head-neck taper design/material/assembly conditions was tested using an incremental cyclic fretting corrosion (ICFC) test method previously developed. METHODS: Seven materials, design, and simulated surgical parameters were evaluated, each being assigned 2 conditions for testing, using a 27-2 (7 factor, quarter factorial) design of experiments test matrix. The factors explored were (1) seating load, (2) head-neck offset, (3) material combination, (4) taper diameter, (5) taper roughness, (6) angular mismatch/engagement, and (7) taper length. Each sample underwent assembly, ICFC testing, pull off. RESULTS: Low seating load and high head offset correlated with increased fretting corrosion (P < .05). High head offset also contributed to a lower onset load for fretting current and higher micromotion (P < .05). Head subsidence measured over the ICFC test for samples seated at 100 N was significantly higher than samples seated at 4000 N. Micromotion for 12-mm head offsets was statistically higher than samples with a 1.5-mm head offset. A number of interactive effects were observed. For example, samples seated at 4000 N were less sensitive to head offset than samples seated at 100 N in terms of the resulting fretting current. CONCLUSION: Taper locking position, material combination, taper engagement length, taper roughness, and taper dimensions all had weak or no correlation with fretting current and taper micromotion. This test method and experimental design is a versatile means of assessing potential new taper designs in the future.

Is There Material Loss at the Conical Junctions of Modular Components for Total Knee Arthroplasty?

BACKGROUND: Clinical concern exists regarding fretting corrosion and material loss from taper junctions in orthopedic devices, with previous research focusing on the modular components from total hip arthroplasty. Comparatively little has been published regarding the fretting corrosion and material loss in modular knee devices. The purpose of this study is to evaluate fretting corrosion damage and quantify material loss for conical total knee arthroplasty taper interfaces. METHODS: Stem tapers of 166 retrieved modular knee devices were evaluated for fretting corrosion using a semiquantitative scoring method. High precision profilometry was then used to determine volumetric material loss and maximum wear depth for a subset of 37 components (implanted for 0.25-18.76 years). Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to characterize the observed damage. RESULTS: Mild to severe fretting corrosion was observed on the majority of tapers, with 23% receiving a maximum visually determined damage score of 4. The median rate of volumetric material loss was 0.11 mm3/y (range 0.00-0.76) for femoral components (both cone and bore taper surfaces combined) and 0.01 mm3 (range 0.00-8.10) for tibial components. Greater rates of material loss were associated with mixed metal pairings. There was a strong correlation between visual fretting corrosion score and calculated material loss (ρ = 0.68, P < .001). Scanning electron microscopy revealed varying degrees of scratching, wear, fretting corrosion, and instances of cracking with morphology not consistent with fretting corrosion, wear, or fatigue. CONCLUSION: Although visual evidence of fretting corrosion damage was prevalent and correlated with taper material loss, the measured volumetric material loss was low compared with prior reports from total hip arthroplasty.

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

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 < .0001). Summed corrosion score was moderately correlated with presence of embedding on the PE liner (ρ = 0.690, P = .017). PE liner abrasion and edge deformation of the femoral stem taper were moderately positively correlated (ρ = 0.690, P = .017). Fretting and corrosion damage were not significantly correlated with patient demographics or radiographic positioning of implants. There were no differences in scores between modular and monoblock designs. 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.

Taper-Trunnion Interface Stress Varies Significantly With Head Size and Activity.

BACKGROUND: Total hip arthroplasty is performed with modular parts. Either a metal or ceramic ball is fastened to the trunnion of a femoral stem via a Morse taper. This implant scenario has been successful. However, recently larger (36 mm or greater) metal heads have become more popular as a means to reduce the incidence of hip joint dislocation. Today, a number of clinical failures have occurred due to mechanically assisted crevice corrosion at the head (taper) stem (trunnion) interface necessitating revision surgery. The objective of this research is to investigate how trunnion stress varies with head size, and how taper-trunnion geometric parameters including horizontal lever arm (HLA), taper engagement level, and a new parameter called trunnion load offset affect trunnion stresses. We hypothesized that trunnion stress may increase with increasing head size and HLA. METHODS: This hypothesis was tested by conducting finite element analysis of a titanium hip stem and 4 commercially available cobalt-chromium femoral heads subjected to 4 different moderate to severe physiological loading conditions. RESULTS: Results showed that trunnion stress increases with increasing head size, increased HLA, and trunnion load offset. It was also found that under certain load cases the trunnion stresses get exceptionally high, especially for the larger head sizes. CONCLUSION: This study suggests trying to avoid larger femoral head sizes that may result in higher implant stresses under certain loading conditions.

Fretting and Corrosion Damage in Retrieved Metal-on-Polyethylene Modular Total Hip Arthroplasty Systems: What Is the Importance of Femoral Head Size?

BACKGROUND: Fretting and corrosion at the modular femoral head-femoral neck (taper) interface have been reported in retrieved total hip arthroplasty (THA) prostheses. This study investigated associations among implant design, radiographic factors, and patient factors with corrosion and fretting at the taper interface in retrieved metal-on-polyethylene modular THA prostheses. METHODS: Ninety-two retrieved primary metal-on-polyethylene THA implants were evaluated and graded for fretting, corrosion, and damage at the taper interface, including the femoral stem trunnion and femoral head. Preoperative radiographs were assessed for osteolysis and femoral stem alignment; and medical records were reviewed for demographic data. RESULTS: Male patients had greater head corrosion (P = .037), patient age at revision had a weak, negative correlation with trunnion corrosion (ρ = -0.20, P = .04), and both body mass index and duration of implantation had weak, positive correlations with head fretting (ρ = 0.26, P = .01 and ρ = 0.33, P = .001, respectively). A weak, negative correlation was found between femoral head size and both head fretting and head corrosion (ρ = -0.26, P = .007 and ρ = -0.21, P = .028, respectively), and a weak, positive correlation was found between head offset and trunnion fretting (ρ = 0.23, P = .030). Varus femoral stem alignment was associated with greater head fretting (P = .038). CONCLUSION: Larger femoral head sizes were correlated with less severe head corrosion and head fretting, with 28-mm heads exhibiting more moderate-to-severe damage. Other factors, such as head-taper engagement and geometry, rather than head size, may affect rates of corrosion and fretting damage at the taper interface.

Effects of Seating Load Magnitude on Incremental Cyclic Fretting Corrosion in 5°40' Mixed Alloy Modular Taper Junctions.

BACKGROUND: Mechanically assisted crevice corrosion of modular tapers continues to be a concern in total joint arthroplasties. A surgical factor that may affect taper fretting corrosion during cyclic loading is seating load magnitude. In this study, modular head-neck taper junctions were seated, capturing load-displacement, over a range of axially oriented loads, and electrochemical and micromotion data were captured during short-term incremental cyclic fretting corrosion (ICFC) tests. The hypothesis is low seating loads result in greater motion and fretting corrosion in ICFC tests. The effect of assembly load on pull-off force post-ICFC testing was also evaluated. METHODS: The study employed custom-built test fixtures which measured head-neck micromotion and an electrochemical chamber to monitor electrochemical reactions. Head-neck motion measurements were captured using 2 noncontact differential variable reluctance transducers mounted to the head. Seating experiments ranged from 1000 to 8000 N. RESULTS: Significant differences due to seating loads were reported in seating displacement, ICFC subsidence, and fretting current at 4000 N cyclic load. Seating load decreased but did not eliminate currents. Fretting onset load remained fixed (approximately 1200 N) for tapers seated above 2000 N. Fretting subsidence was negligible for seating loads of 4000 N or higher, and increased subsidence was observed below 4000 N. CONCLUSION: This short-term test method evaluated the acute performance of modular implants which were assembled under various loads and demonstrated the link between seating loads, fretting motions, and electrochemical reactions. While increased seating loads reduced fretting corrosion and taper subsidence, it did not prevent fretting corrosion even at 8 kN seating.

Management of the Implant With Taper Corrosion: What to Change and What to Change It to?

Management of implant corrosion remains a challenge for the revision arthroplasty surgeon. Our field continues to gain insight in to how to manage this clinical scenario but there are still gaps in what is known to be considered to be the standard of care. There is a significant amount of effort going in to determining the best means of managing this issue but more work is needed. There is no doubt more studies are needed to further delineate the appropriate treatment algorithms for this clinical problem.

Does the Additional Articulation in Retrieved Bipolar Hemiarthroplasty Implants Decrease Trunnionosis Compared to Total Hip Arthroplasty?

BACKGROUND: Trunnionosis at the modular head-neck taper interface in metal-on-polyethylene total hip arthroplasty (MoP THA) has been shown to occur, and represents a potential mode of MoP THA failure. The purpose of the present investigation is to elucidate differences in fretting and corrosion at the head-neck taper interface of prostheses retrieved from bipolar hemiarthroplasty (BH) and MoP THA. METHODS: A retrieval analysis of BH and MoP THA prostheses featuring a single taper design from a single manufacturer and in vivo for a minimum 2 years was performed. Fifteen femoral heads of 28-mm diameter and corresponding femoral stems retrieved from BH were compared with MoP THA implants matched based on time in vivo and head length (28 mm, -3 mm to 28 mm, +8 mm). Fretting and corrosion damage scoring was completed under stereomicroscopic visualization. RESULTS: Femoral head bore tapers retrieved from BH exhibited decreased overall fretting (P = .02), when compared to those retrieved from MoP THA. Total corrosion scores for all retrieved implants were positively correlated with implantation time (ρ = 0.54, P < .02). CONCLUSION: Femoral heads retrieved from BH exhibit decreased fretting damage compared to those retrieved from MoP THA. The added articulation in BH implants may decrease torque produced at the head-neck taper junction, thereby decreasing fretting. Increased fretting damage in implants from MoP THA is not associated with increased corrosion in 28-mm heads of this taper design. The longer a BH or MoP THA prosthesis is implanted, the greater the risk of damage due to corrosion.