The onset of fretting at the head-stem connection in hip arthroplasty is affected by head material and trunnion design under simulated corrosion conditions

The Progress in Tribocorrosion Research (2010-21): Focused on the Orthopedics and Dental Implants

Tribocorrosion is an integration of two areas-tribology and corrosion. It can be defined as the material degradation caused by the combined effect of corrosion and tribological process at the material interfaces. Significant development has occurred in the field of tribocorrosion over the past years. This development is due to its applications in various fields, such as aerospace, marine, biomedical, and space. Focusing on biomedical applications, tribocorrosion finds its applications in the implants used in cardiovascular, spine, orthopedics, trauma, and dental areas. It was reported that around 7.2 million Americans are living with joint implants. Implant surgery is a traumatic and expensive procedure. Tribocorrosion can affect the lifespan of the implants, thus leading to implant failure and a potential cause of revision surgery. Hence, it is essential to understand how tribocorrosion works, its interaction with the implants, and what procedures can be implemented to protect materials from tribocorrosion. This paper discusses how tribocorrosion research has evolved over the past 11 years (2010-2021). This is a comprehensive overview of tribocorrosion research in biomedical applications.

Evaluation of Mechanically-Assisted Crevice Corrosion of Different Modular Dual Mobility Constructs

BACKGROUND

Modular dual mobility (MDM) acetabular component use is rising in total hip arthroplasty. However, concern of mechanically-assisted crevice corrosion (MACC) at the shell-liner interface remains. We investigated shell-liner corrosion using retrieval analyses and corrosion chamber testing.

METHODS

We analyzed fretting and corrosion on 10 matched pairs of two commercial modular dual mobility constructs (MDM1 and MDM2). Also, pristine pairs of Ti6Al4V shells and CoCrMo liners from three commercial dual mobility systems (MDM1, MDM2, MDM3) were tested in vitro to model MACC performance. Three pairs of each were placed into an electrochemical chamber with stepwise increasing cyclic compression loads, while measuring currents generated at the shell-liner taper. Onset fretting loads and fretting currents were calculated.

RESULTS

Corrosion damage scores on retrieved components were low, but higher in the MDM2 to MDM1 liners (P = 0.006), specifically outside the taper region (P = 0.00003). Fretting currents were higher in the MDM2 than in MDM1 or MDM3 (P = 0.011). Onset loads were also higher in the MDM2 (P = 0.001).

CONCLUSION

Among retrieved liners, MDM2 tapers seem prone to non-mechanical corrosion modes. Higher onset loads and fretting currents in MDM2 tapers indicate greater MACC resistance, but higher severity once corrosion begins. Differences among the devices were likely due to taper design and surface finish. Currents in all three were <5 μA, much lower than those observed with head-neck tapers. Our findings suggest that among the types of corrosion observed in these MDM designs, mechanically driven corrosion may not be the most significant.

Decomposition of micromotion at the head-neck interface in total hip arthroplasty during walking

Fretting corrosion as one of the leading causes for failure of modular hip prostheses has been associated with micromotion at head-neck taper junction. Decomposition of micromotion is helpful to promote the development of more realistic experiments investigating failure mechanisms of the head-neck junction in total hip arthroplasty. The aim of this study was to decompose the complex three-dimensional micromotion at the head-neck junction into multiple fundamental modes, including three translational and three rotational components. A three-dimensional finite element model composed of head-neck junction, liner and acetabular cup with a typical 12/14 taper size, as well as the taper mismatch of -4', was developed during walking. The analysis was divided into three procedures: a) the assembly simulation of the head and neck during surgery, b) verification with a simplified axisymmetric model, and c) three-dimensional modelling under normal walking. This study revealed that the main forms of micromotion contained circumferential, longitudinal micromotion and longitudinal rolling toggling, and were closely related to the state of motion. The maximum translational micromotion was predicted to be 10.9 μm during the walking gait, with the predominant modes of the circumferential translation of 9.6 μm, the longitudinal translation of 5.5 μm and the longitudinal rotation of 0.29° along the taper junction. These findings may provide design considerations for further experimental testing about fretting and facilitate the understanding of the fretting mechanisms in hip prostheses.

A case-driven hypothesis for multi-stage crack growth mechanism in fourth-generation ceramic head fracture

BACKGROUND

Ceramic bearings are used in total hip arthroplasty due to their excellent wear behaviour and biocompatibility. The major concern related to their use is material brittleness, which significantly impacts on the risk of fracture of ceramic components. Fracture toughness improvement has contributed to the decrease in fracture rate, at least of the prosthetic head. However, the root cause behind these rare events is not fully understood. This study evaluated head fracture occurrence in a sizeable cohort of patients with fourth-generation ceramic-on-ceramic implants and described the circumstances reported by patients in the rare cases of head fracture.

METHODS

The clinical survivorship of 29,495 hip prostheses, with fourth-generation ceramic bearings, was determined using data from a joint replacement registry. The average follow-up period was 5.2 years (range 0.1-15.6). Retrieval analysis was performed in one case for which the ceramic components were available.

RESULTS

Clinical outcomes confirmed the extremely low fracture rate of fourth-generation ceramic heads: only two out of 29,495 heads fractured. The two fractures, both involving 36 mm heads, occurred without a concurrent or previous remarkable trauma. Considering the feature of the fractured head, a multi-stage crack growth mechanism has been hypothesized to occur following damage at the head-neck taper interface.

CONCLUSIONS

Surgeons must continue to pay attention to the assembly of the femoral head: achieving a proper head seating on a clean taper is a prerequisite to decrease the risk of occurrence of any damage process within head-neck junction, which may cause high stress concentration at the contact surface, promoting crack nucleation and propagation even in toughened ceramics.

Catastrophic Trunnion Failure in an Anatomic Titanium Alloy Stem

Introduction

Certain titanium alloy stems have been shown to be susceptible to failure at the neck with catastrophic trunnion failure. Failure has been particularly noted in the single wedge Accolade 1 stem design. Other stems also used this alloy including the anatomic designed Citation stem.

Methods

This case series details 3 catastrophic failures of the TMZF version of the Citation femoral stem.

Results

Each of these failures appear to be attributed to cyclical wear of the TMZF trunnion against the cobalt chromium femoral head. Wear resulted in ultimate implant failure and significant metal debris in the joint capsule at the time of revision surgery.

Discussion

While surgeons are aware of the risk of catastrophic failure for the Accolade 1 stem, failure may similarly happen in the TMZF Citation stem. Surgeons should monitor these implants with care and discuss the potential for trunnion failure with their patients.

Effect of head size and rotation on taper corrosion in a hip simulator

AIMS

This study investigates head-neck taper corrosion with varying head size in a novel hip simulator instrumented to measure corrosion related electrical activity under torsional loads.

METHODS

In all, six 28 mm and six 36 mm titanium stem-cobalt chrome head pairs with polyethylene sockets were tested in a novel instrumented hip simulator. Samples were tested using simulated gait data with incremental increasing loads to determine corrosion onset load and electrochemical activity. Half of each head size group were then cycled with simulated gait and the other half with gait compression only. Damage was measured by area and maximum linear wear depth.

RESULTS

Overall, 36 mm heads had lower corrosion onset load (p = 0.009) and change in open circuit potential (OCP) during simulated gait with (p = 0.006) and without joint movement (p = 0.004). Discontinuing gait's joint movement decreased corrosion currents (p = 0.042); however, wear testing showed no significant effect of joint movement on taper damage. In addition, 36 mm heads had greater corrosion area (p = 0.050), but no significant difference was found for maximum linear wear depth (p = 0.155).

CONCLUSION

Larger heads are more susceptible to taper corrosion; however, not due to frictional torque as hypothesized. An alternative hypothesis of taper flexural rigidity differential is proposed. Further studies are necessary to investigate the clinical significance and underlying mechanism of this finding. Cite this article: Bone Jt Open 2021;2(11):1004-1016.

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).

Impending Trunnion Failure: An Uncommon Radiographic Presentation of Total Hip Arthroplasty Failure

Trunnionosis is emerging as an early mode of failure in conventional metal-on-polyethylene total hip arthroplasty. It is defined as wear or corrosion at the trunnion, the taper at the femoral head-neck interface. Trunnion wear can result in a variety of negative sequelae and, in severe cases, necessitate revision arthroplasty. We describe a 64-year-old man with a metal-on-polyethylene total hip arthroplasty who presented with a sensation of clunking in the hip. Initial imaging and laboratory studies were inconclusive, and the decision was made to monitor. Two years later, trunnion wear was detected on radiographs, presenting as an abnormal alignment of the femoral neck relative to the femoral head. Several case reports and series describe catastrophic total hip arthroplasty failure due to trunnionosis. However, few describe the radiographic signs of wear at the trunnion before gross failure. This early presentation is important to recognize to minimize patient morbidity and aid surgical planning.

Corrosion Concerns? Trends in Metal-on-Polyethylene Total Hip Arthroplasty Revision Rates and Comparisons Against Ceramic-on-Polyethylene up to 10 Years of Follow-Up

BACKGROUND

We compared the revision risk between metal-on-polyethylene (MOP) and ceramic-on-polyethylene (COP) total hip arthroplasty patients and evaluated temporal changes in short-term revision risks for MOP patients.

METHODS

Primary MOP (n = 9480) and COP (n = 3620) total hip arthroplasties were evaluated from the Medicare data set (October 2005 to December 2015) for revision risk, with up to 10 years of follow-up using multivariate analysis. Temporal change in the short-term revision risk for MOP was evaluated (log-rank and Wilcoxon tests).

RESULTS

Revision incidence was 3.8% for COP and 4.3% for MOP. MOP short-term revision risk did not change over time (P ≥ .844 at 1 year and .627 at 2 years). Dislocation was the most common reason for revision (MOP: 23.5%; COP: 24.8%). Overall adjusted revision risks were not different between MOP and COP up to 10 years of follow-up (P ≥ .181).

CONCLUSIONS

Concerns with corrosion for metal heads do not appear to result in significantly elevated revision risk for MOP at up to 10 years. Corrosion does not appear as a primary reason for revision compared to other mechanisms.

2020 Otto Aufranc Award: Malseating of modular dual mobility liners

AIMS

This combined clinical and in vitro study aimed to determine the incidence of liner malseating in modular dual mobility (MDM) constructs in primary total hip arthroplasties (THAs) from a large volume arthroplasty centre, and determine whether malseating increases the potential for fretting and corrosion at the modular metal interface in malseated MDM constructs using a simulated corrosion chamber.

METHODS

For the clinical arm of the study, observers independently reviewed postoperative radiographs of 551 primary THAs using MDM constructs from a single manufacturer over a three-year period, to identify the incidence of MDM liner-shell malseating. Multivariable logistic regression analysis was performed to identify risk factors including age, sex, body mass index (BMI), cup design, cup size, and the MDM case volume of the surgeon. For the in vitro arm, six pristine MDM implants with cobalt-chrome liners were tested in a simulated corrosion chamber. Three were well-seated and three were malseated with 6° of canting. The liner-shell couples underwent cyclic loading of increasing magnitudes. Fretting current was measured throughout testing and the onset of fretting load was determined by analyzing the increase in average current.

RESULTS

The radiological review identified that 32 of 551 MDM liners (5.8%) were malseated. Malseating was noted in all of the three different cup designs. The incidence of malseating was significantly higher in low-volume MDM surgeons than high-volume MDM surgeons (p < 0.001). Pristine well-seated liners showed significantly lower fretting current values at all peak loads greater than 800 N (p < 0.044). Malseated liner-shell couples had lower fretting onset loads at 2,400 N.

CONCLUSION

MDM malseating remains an issue that can occur in at least one in 20 patients at a high-volume arthroplasty centre. The onset of fretting and increased fretting current throughout loading cycles suggests susceptibility to corrosion when this occurs. These results support the hypothesis that malseated liners may be at risk for fretting corrosion. Clinicians should be aware of this phenomenon. Cite this article: Bone Joint J 2020;102-B(7 Supple B):20-26.

Fretting corrosion of Si3 N4 vs CoCrMo femoral heads on Ti-6Al-V trunnions

Fretting corrosion at the head-neck taper junction was compared between silicon nitride (Si₃ N₄ ) and commercially available cobalt chrome (CoCrMo) femoral heads on titanium (Ti-6Al-4V) trunnions. An electrochemical setup was used to capture the fretting currents (characterized by oxide abrasion and repassivation) during cyclic loading. Onset load, pull-off force (disassembly load), short term and long term (1 million cycles) fretting currents were used to compare the fretting corrosion performance between the test group (Si₃ N₄ /Ti-6Al-4V) and the control group (CoCrMo/Ti-6Al-4V). Incremental cyclic fretting corrosion tests showed that the Si₃ N₄ /Ti-6Al-4V combination had statistically lower (P < .05) average fretting current of 0.189 µA (SD = 0.114 µA) compared to 0.685 µA (SD = 0.630 µA) for CoCrMo/Ti-6Al-4V for cyclic load of 3200 N. Similarly, for the one million cycle fretting corrosion tests, the Si₃ N₄ /Ti-6Al-4V couples had statistically lower (P < .05) average current (0.048 µA, SD = 0.025 µA) vs CoCrMo/Ti-6Al-4V couples (0.366 µA, SD = 0.143 µA). The Si₃ N₄ heads also had higher onset loads (P < .05) for fretting (vs CoCrMo, 2200 N vs 1740 N) indicating a difference in surface contact mechanics between the two groups. Scanning electron microscopy with energy dispersive spectroscopy confirmed material transfer from the trunnions to the heads for both groups tested, and from head to trunnion for the CoCrMo heads. Minimal Si₃ N₄ transfer was noted. The electrochemical, mechanical, and microscopic inspection data supported the hypothesis that Si₃ N₄ /Ti-6Al-4Vcombination had better fretting corrosion performance compared to CoCrMo/Ti-6Al-4V.

Taper Design, Head Material, and Manufacturer Affect the Onset of Fretting Under Simulated Corrosion Conditions

BACKGROUND

We investigated the effect of taper design, head material, and manufacturer on simulated mechanically assisted crevice corrosion (MACC).

METHODS

Six pristine C-taper stems coupled with alumina-zirconia or cobalt-chromium (CoCr) heads were tested in a mechanical/electrochemical setup to measure average fretting currents and fretting current onset loads. Outcomes were compared with previous data from V40 tapers from the same manufacturer and 12/14 tapers from another manufacturer.

RESULTS

Within a single manufacturer, differences in average fretting current between V40 and C-taper designs were dependent on head material. Only with V40 tapers did CoCr heads show higher average fretting currents than ceramic heads. Between manufacturers, differences were found between similar taper designs, as 12/14 taper couples showed higher average fretting currents than C-taper couples, regardless of head material.

CONCLUSION

Taper design, head material, and factors inherent to different manufacturers influence fretting current in simulated MACC. Unlike clinical and retrieval studies, this experimental design allows for investigations of factors affecting MACC in a controlled environment. Taper design, independent of manufacturer, contributes to the observed differences in average fretting current between head materials. In some taper designs, head composition, specifically ceramic, should not be considered alone to reduce risk of corrosion.

Fretting Wear in Orthodontic and Prosthetic Alloys with Ti(C, N) Coatings

Fretting occurs during orthodontic treatment or wearing prosthesis. Although weight of particles is marginal, the total releasing area is more of a concern due to amount and volume of molecules. The aim of the study was to examine the fretting wear resistance of orthodontic and prosthetic alloy Ni-Cr-Mo samples coated with Ti(C, N) and to compare them with samples without any coating. Five groups of cylindrical shape samples (S1–S5) made of Ni-Cr-Mo were coated with Ti(C, N) layers with different content of C and N. The control group (S0) was without layer. The alloys underwent fretting wear resistance tests with amplitude 100 μm, at frequency 0.8 Hz with averaged unit load: 5, 10, and 15 N for 15 min. The samples were subjected to microscopic observations using scanning electron microscope and a laser scanning microscope. Samples with Ti(C, N) coatings revealed higher fretting wear resistance. The wear in each case with Ti(C, N) coatings was over twice as low. The lowest wear and thus the highest resistance was demonstrated by sample S3 (1.02 µm) whereas in control group-S0 (2.64 µm). The use of Ti(C, N)-type coatings reduces the adverse effects of fretting wear, decreasing the amount of ions released during orthodontic treatment or wearing prosthesis.

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.

Influence of flexural rigidity on micromotion at the head-stem taper interface of modular hip prostheses

Fretting corrosion as one reason for failure of modular hip prostheses has been associated with micromotion at the head taper junction. Historically the taper diameter was reduced to improve the range of motion of the hip joint. In combination with other developments, this was accompanied by increased observations of taper fretting, possibly due to the reduced flexural rigidity of smaller tapers. The aim of the study was to investigate how the flexural rigidity of tapers influences the amount of micromotion at the head taper junction. Three different stem and two different taper designs were manufactured. Experimental testing was performed using three different activity levels with peak loads representing walking, stair climbing and stumbling. The relative motion at the head-stem taper was measured in six degrees of freedom. Micromotion was obtained by subtraction of the elastic deformation derived from monoblock and finite element analysis. Less rigid tapers lead to increased micromotion between the head and stem, enlarging the risk of fretting corrosion. The influence of the stem design on micromotion is secondary to taper design. Manufacturers should consider stiffer taper designs to reduce micromotion within the head taper junction.

Do oxidized zirconium heads decrease tribocorrosion in total hip arthroplasty? A study of retrieved components

AIMS

The aim of this study was to evaluate fretting and corrosion in retrieved oxidized zirconium (OxZr; OXINIUM, Smith & Nephew, Memphis, Tennessee) femoral heads and compare the results with those from a matched cohort of cobalt-chromium (CoCr) femoral heads.

PATIENTS AND METHODS

A total of 28 OxZr femoral heads were retrieved during revision total hip arthroplasty (THA) and matched to 28 retrieved CoCr heads according to patient demographics. The mean age at index was 56 years (46 to 83) in the OxZr group and 70 years (46 to 92) in the CoCr group. Fretting and corrosion scores of the female taper of the heads were measured according to the modified Goldberg scoring method.

RESULTS

The OxZr-retrieved femoral heads showed significantly lower mean corrosion scores than the CoCr heads (1.3 (1 to 2.75) vs 2.1 (1 to 4); p < 0.01). Mean fretting scores were also significantly lower in the OxZr cohort when compared with the CoCr cohort (1.3 (1 to 2) vs 1.5 (1 to 2.25); p = 0.02). OxZr heads had more damage in the proximal region compared with the distal region of the head. Location had no impact on damage of CoCr heads. A trend towards increased corrosion in large heads was seen only in the CoCr heads, although this was not statistically significant.

CONCLUSION

Retrieval analysis of OxZr femoral heads showed a decreased amount of fretting and corrosion compared with CoCr femoral heads. OxZr seems to be effective at reducing taper damage. Cite this article: Bone Joint J 2019;101-B:386-389.