Differences in the fretting corrosion of metal-metal and ceramic-metal modular junctions of total hip replacements

The effect of trunnionosis on the risk of re-revision following femoral head exchange in hip arthroplasty

BACKGROUND

Fretting corrosion at modular junctions contributes to arthroplasty failure. Currently, no evidence-based guidelines are available regarding the acceptable level of trunnion corrosion that can occur in vivo. We aimed to examine the relationship between trunnion corrosion and risk of re-revision to assist surgeons with intraoperative decision making.

METHOD

Grading by 3 independent examiners of revised and re-revised head components was performed using a modified Goldberg corrosion scale. Samples were separated into low-grade (LG) and high-grade (HG) corrosion. Mechanical testing determined the relationship between corrosion severity and pull-off strength at the head-stem junction.

RESULTS

529 retrieved femoral heads were analysed. A positive association was detected between males and HG corrosion (OR 2.07; 95% CI, 1.45-2.94; p < 0.001). No difference between the survivorship of LG and HG heads was detected (p-value = 0.247). In the re-revised sample, the first implant had a time in situ that was on average 7.97 years longer (95% CI, 5.4-10.6) than that of the subsequent re-revised femoral head. Severe corrosion on the first head was associated with a 37.5 (95% CI, 4.00-1944) fold increase of HG on the subsequent head (p < 0.001). Femoral disassembly force had a positive correlation with stem taper corrosion grade (p = 0.001).

CONCLUSIONS

A well-fixed stem with corrosion may remain in situ.

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.

Metals and Trace Elements in Calcified Valves in Patients with Acquired Severe Aortic Valve Stenosis: Is There a Connection with the Degeneration Process?

BACKGROUND

Acquired calcified aortic valve stenosis is the most common valve disease in adulthood. In the etiopathogenesis of this complex pathology, the importance of inflammation is mentioned, in which non-infectious influences represented by the biological effects of metal pollutants may participate. The main goal of the study was to determine the concentration of 21 metals and trace elements-aluminium (Al), barium (Ba), cadmium (Cd), calcium (Ca), chrome (Cr), cobalt (Co), copper (Cu), gold (Au), lead (Pb), magnesium (Mg), mercury (Hg), molybdenum (Mo), nickel (Ni), phosphorus (P), selenium (Se), strontium (Sr), sulfur (S), tin (Sn), titanium (Ti), vanadium (V) and zinc (Zn)-in the tissue of calcified aortic valves and to compare them with the concentrations of the same elements in the tissue of healthy aortic valves in the control group.

MATERIAL AND METHODS

The study group consisted of 49 patients (25 men, mean age: 74) with acquired, severe, calcified aortic valve stenosis with indicated heart surgery. The control group included 34 deceased (20 men, median age: 53) with no evidence of heart disease. Calcified valves were explanted during cardiac surgery and deep frozen. Similarly, the valves of the control group were removed. All valves were lyophilized and analyzed by inductively coupled plasma mass spectrometry. The concentrations of selected elements were compared by means of standard statistical methods.

RESULTS

Calcified aortic valves contained significantly higher (p < 0.05) concentrations of Ba, Ca, Co, Cr, Mg, P, Pb, Se, Sn, Sr and Zn and-in contrast-lower concentrations of Cd, Cu, Mo, S and V than valves of the control group. Significant positive correlations of concentrations between the pairs Ca-P, Cu-S and Se-S and strong negative correlations between the elements Mg-Se, P-S and Ca-S were found in the affected valves.

CONCLUSION

Aortic valve calcification is associated with increased tissue accumulation of the majority of the analyzed elements, including metal pollutants. Some exposure factors may increase their accumulation in the valve tissue. A relationship between exposure to environmental burden and the aortic valve calcification process cannot be ruled out. Advances in histochemical and imaging techniques allowing imaging of metal pollutants directly in valve tissue may represent an important future perspective.

No dislocation and low complication rate for a modern dual mobility cup with pre-impacted femoral head in primary hip replacement: A consecutive series of 175 hips at minimum 5-year follow-up

INTRODUCTION

Despite its excellent results in preventing dislocation, the dual mobility cup (DMC) is still struggling to be adopted by some teams due to premature wear and loosening reported on first-generation implants. Therefore, this study aimed to assess the mid-term survivorship of a modern DMC with a pre-impacted head and the radio-clinical results at a minimum follow-up of 5 years.

METHODS

This was a retrospective single-centre study performed on patients who had a primary total hip replacement for osteoarthritis in 2016. The cup was a third-generation DMC with a pre-impacted femoral head. Clinical (harris hip score (HHS)) and radiological (cup abduction, anteversion, overhang, and radiolucent lines) results were recorded, as well as complications, particularly dislocations and survivorship. A minimum of five years of follow-ups was required.

RESULTS

One hundred and seventy-five hips (167 patients) met the inclusion criteria. Five hips (2.9%, 5/175) were lost to follow-up and excluded from the postoperative analysis. The mean follow-up period was 70 ± 2.9 months [63.6-76.5]. Three cups needed revision surgery (1.8%, 3/170): one for septic loosening, and two for chronic infection. At 77 months, the global survival probability was 98.2% ± 1, and the survival probability excluding septic aetiology was 100%. There was a significant improvement in the HHS from pre-operatively (48.3 ± 6.0 [14.0-70.0]) to post-operatively (96 ± 4.5 [50-100]) (p < 0.0001). There were no postoperative dislocations recorded, nor any iliopsoas-impingement or symptomatic cam-effect.

DISCUSSION

This study showed excellent survival and good radiological and clinical results of this dual mobility cup at a mid-term follow-up. None of the patients had dislocation or any specific complication feared with dual mobility cups.

Hip implant modular junction: The role of CoCrMo alloy microstructure on fretting-corrosion

Cobalt-chromium-molybdenum (CoCrMo) alloy is one of the most used metals in total hip replacement (THR) due to the alloy's superior corrosion qualities and biocompatibility. Over time these prostheses may undergo wear and corrosion processes in a synergistic process known as tribocorrosion. Implant retrieval studies have shown that damage patterns on THR modular junction surfaces indicating specifically in vivo fretting-corrosion to take place. To date, there have been no studies on the fretting-corrosion behaviors of CoCrMo alloy under the consideration of specific microstructural features. A custom-built flat-on-flat fretting-corrosion setup was utilized to test the synergistic tribocorrosion behavior of fretting-corrosion. The difference in microstructure was generated through the cutting orientations of the transverse and the longitudinal direction of the bar stock material, where the longitudinal cut exhibits a characteristic banded microstructure (banded group) and the transverse cut a homogenous microstructure (unbanded group). A three-electrode system was employed to monitor the induced currents. Two different types of electrolytes were used in the current study: 1. Bovine calf serum (BCS-30 g/L protein) (normal conditions) 2. BCS with Lipopolysaccharide (LPS, 0.15 μg/ml) (simulated infectious conditions). In the free potential mode, banded samples showed an increased potential compared to the unbanded samples. In potentiostatic conditions, the banded group also exhibited a higher induced current in both electrolyte environments, indicating more corrosion loss. Both Nyquist and Bode plots showed both orientations of metal becoming more corrosion resistant post-fretting when compared to pre-fretting data. The longitudinal group at OCP demonstrated a unique shape of the fretting-loop, which might be related to tribochemical reactions. Based on the mechanical, electrochemical, and surface characterization data, the transverse group (unbanded) microstructures demonstrates a higher resistance to fretting-corrosion damage.

Insights into Imprinting: How Is the Phenomenon of Tribocorrosion at Head-Neck Taper Interfaces Related to Corrosion, Fretting, and Implant Design Parameters?

BACKGROUND

Wear and corrosion at modular neck tapers in THA can lead to major clinical implications such as periprosthetic osteolysis, adverse local tissue reactions, or implant failure. The material degradation processes at the taper interface are complex and involve fretting corrosion, third-body abrasion, as well as electrochemical and crevice corrosion. One phenomenon in this context is imprinting of the head taper, where the initially smooth surface develops a topography that reflects the rougher neck taper profile. The formation mechanism of this specific phenomenon, and its relation to other observed damage features, is unclear. An analysis of retrieved implants may offer some insights into this process.

QUESTIONS/PURPOSES

(1) Is imprinting related to time in situ of the implants and to the taper damage modes of corrosion and fretting? (2) Are implant design parameters like neck taper profile, stem material, or head seating associated with the formation of imprinting? (3) Is imprinting created by an impression of the neck taper profile or can a different mechanistic explanation for imprinting be derived?

METHODS

Thirty-one THAs with cobalt-chromium-molybdenum-alloy (CoCrMo) heads retrieved between 2013 and 2019 at revision surgery from an institutional registry were investigated. Inclusion criteria were: 12/14 tapers, a head size of 36 mm or smaller, time in situ more than 1 year, and intact nonmodular stems without sleeve adaptors. After grouping the residual THAs according to stem type, stem material, and manufacturer, all groups of three or more were included. Of the resulting subset of 31 retrievals, nine THAs exhibited a still assembled head-neck taper connection. The median (range) time in situ was 5 years (1 to 23). Two stem materials (21 titanium-alloy and 10 stainless steel), three kinds of bearing couples (11 metal-on-metal, 13 metal-on-polyethylene, and seven dual-mobility heads), and two different neck taper profiles (six wavy profile and 25 fluted profile) were present in the collection. Four THAs exhibited signs of eccentric head seating. The 31 investigated THAs represented 21% of the retrieved THAs with a CoCrMo alloy head during the specified period.At the head tapers, the damage modes of corrosion, fretting, and imprinting were semiquantitatively rated on a scale between 0 (no corrosion/fretting/imprinting) and 3 (severe corrosion/fretting/imprinting). Corrosion and fretting were assessed applying the Goldberg score, with the modification that the scale started at 0 and not at 1. Imprinting was assessed with a custom scoring system. Rating was done individually at the proximal and distal head taper half and summed to one total damage score for each retrieval and damage mode. Correlations between the damage modes and time in situ and between the damage modes among each other, were assessed using the Spearman rank order correlation coefficient (ρ). Associations between imprinting and implant design parameters were investigated by comparing the total imprinting score distributions with the Mann-Whitney U-test. Metallographically prepared cross-sections of assembled head-neck taper connections were examined by optical microscopy and disassembled head and neck taper surfaces were assessed by scanning electron microscopy (SEM).

RESULTS

The imprinting damage score increased with time in-situ (ρ = 0.72; p < 0.001) and the corrosion damage score (ρ = 0.63; p < 0.001) but not with the fretting damage score (ρ = 0.35; p = 0.05). There was no difference in total imprinting score comparing neck taper profiles or stem materials, with the numbers available. Eccentric head seating had elevated total imprinting score (median 6 [interquartile range 0]) compared with centric seating (median 1 [2]; p = 0.001). Light optical investigations showed that imprinting can be present on the head taper surfaces even if the depth of abraded material exceeds the neck taper profile height. SEM investigations showed bands of pitting corrosion in the imprinted grooves.

CONCLUSION

The microscopic investigations suggest that imprinting is not an independent phenomenon but a process that accompanies the continuous material degradation of the head taper surface because of circular damage on the passive layer induced by grooved neck tapers.

CLINICAL RELEVANCE

Material loss from head-neck taper connections involving CoCrMo alloy heads is a source of metal ions and could potentially be reduced if hip stems with smooth neck tapers were used. Surgeons should pay attention to the exact centric seating of the femoral head onto the stem taper during joining of the parts.

Survivorship of a Metal-on-Metal Total Hip Implant With Modular Titanium Adapter

BACKGROUND

Use of metal-on-metal (MoM) articulations in total hip arthroplasty (THA) has sharply declined due to high failure rates from metal-related complications. Although certain MoM designs have demonstrated only 46% survival, not all MoM designs have performed the same. The purpose of this study is to evaluate mid-term to long-term survival of a specific MoM implant with a modular titanium taper adapter.

METHODS

A retrospective review was performed on all patients who underwent primary THA at our center with the M²a-Magnum system (Zimmer Biomet, Warsaw, IN). Of 829 patients (956 hips) identified, 754 patients (869 hips) met inclusion criteria of signed research consent, minimum 2-year follow-up, and/or any revision surgery.

RESULTS

Mean follow-up was 11.0 years (range 2-16; ±3.5). Mean cup angle of inclination was 42.8° (range 24°-70°, ±6.3°), with 88.0% reconstructed within the 40° ± 10° safe zone. There were 64 revisions (7.36%): 7 (0.81%) septic and 57 (6.56%) aseptic. Of those, 32 (3.68%) were adverse reactions to metal debris. Kaplan-Meier survival free of revision for all causes was 88.6% at 16 years (95% confidence interval 86.8-90.4). Univariate analysis of risk factors for all-cause, aseptic, and adverse reaction to metal debris revision found no relationship with female gender, age ≥65 years, body mass index >30 kg/m², higher activity level, or inclination angle outlier.

CONCLUSION

The results of this study demonstrate a more favorable mid-term to long-term survivorship with this specific MoM implant compared to other designs. Although our institution no longer performs MoM THA, further investigation into differences in MoM implant designs is warranted.

A biomechanical evaluation on Cubic, Octet, and TPMS gyroid Ti6Al4V lattice structures fabricated by selective laser melting and the effects of their debris on human osteoblast-like cells

Lattice structures are widely used in orthopedic implants due to their unique features, such as high strength-to-weight ratios and adjustable biomechanical properties. Based on the type of unit cell geometry, lattice structures may be classified into two types: strut-based structures and sheet-based structures. In this study, strut-based structures (Cubic & Octet) and sheet-based structure (triply periodic minimal surface (TPMS) gyroid) were investigated. The biomechanical properties of the three different Ti6Al4V lattice structures fabricated by selective laser melting (SLM) were investigated using room temperature compression testing. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to check the 3D printing quality with regards to defects and quantitative compositional information of 3D printed parts. Experimental results indicated that TPMS gyroid has superior biomechanical properties when compared to Cubic and Octet. Also, TPMS gyroid was found to be less affected by the variations in relative density. The biocompatibility of Ti6Al4V lattice structures was validated through the cytotoxicity test with human osteoblast-like SAOS2 cells. The debris generated during the degradation process in the form of particles and ions is among the primary causes of implant failure over time. In this study, Ti6Al4V particles with spherical and irregular shapes having average particle sizes of 36.5 μm and 28.8 μm, respectively, were used to mimic the actual Ti6Al4V particles to understand their harmful effects better. Also, the effects and amount of Ti6Al4V ions released after immersion within the cell culture media were investigated using the indirect cytotoxicity test and ion release test.

Sliding Corrosion Fatigue of Metallic Joint Implants: A Comparative Study of CoCrMo and Ti6Al4V in Simulated Synovial Environments

Mechanical contact in a corrosive synovial environment leads to progressive surface damage at the modular interface of the joint implants. The wear debris and corrosion products degrade the synovial fluids and change the lubrication mechanisms at the joints. Consequently, the unstable joint lubrication and corrosion products will further induce the undesirable performance of the joint implants. In this study, the two major joint materials, CoCrMo and Ti6Al4V, were tested during the course of reciprocal sliding contact in simulated synovial liquids. Open circuit potential and coefficient of friction were monitored to describe electrochemical and mechanical responses. Potentiostatic test results illustrated electrochemical damage on both surfaces that modified oxidation chemistry on both surfaces. However, more significant modification of the CoCrMo surface was detected during wear in the simulated joint liquid. Even with a reduced coefficient of friction on the CoCrMo surface in sodium lactate environments, fretting current density drastically increased in corrosive sodium lactate with pH 2. However, the test results from the Ti6Al4V surface presented less coefficient of friction values, and moderate change in fretting current. Therefore, the experimental study concluded that the biocompatibility of Ti6Al4V is superior to that of CoCrMo in the combined effect of mechanical loadings and an electrochemical environment.

Tribocorrosion is Common, but Mild in Modular Humeral Components in Shoulder Arthroplasty: An Implant Retrieval Analysis

Background

Wear and corrosion at the junctions of modular implants are increasingly recognized issues in the design of hip and knee arthroplasty prostheses, yet less is known about their significance in shoulder arthroplasty.

Methods

A query of paired total shoulder implant specimens (eg, humeral head and stem components from the same patient) was performed using an institutional implant retrieval registry. Implants were examined under a stereomicroscope and evaluated for evidence of fretting and corrosion using the modified Goldberg scoring system. Available electronic medical records of included specimens were reviewed to report relevant clinical characteristics and identify potential associations with the presence of tribocorrosion.

Results

Eighty-three paired total shoulder implant specimens, explanted at a single institution between 2013 and 2020, were analyzed. Corrosion was identified in 52% (43/83) of humeral head components and 40% (33/83) of humeral stem components. Fretting was identified in 29% (24/83) of humeral head components and 28% (23/83) of humeral stem components. Of the 56 paired implants for which clinical data were available, the duration of implantation (DOI) was less than 2 years in 29% of paired implants and greater than 5 years in 36% of implants. The presence of corrosion or fretting was not associated with DOI, a male humeral head taper, or periprosthetic infection as the indication for revision.

Conclusion

Mild tribocorrosion was present in more than half of the retrieved humeral implant specimens. However, trunnionosis did not manifest as a clinical cause of revision surgery in our study.

Intraoperative assembly of anatomical shoulder prosthesis frequently results in malalignment of the modular taper junction

Anatomical shoulder arthroplasties (ASA) may fail because of micromotion at the modular taper junction causing wear due to fretting. Sufficient taper strength can reduce micromotion and potential reasons for failure. However, there are no normative standards for a safe assembly process performed intraoperatively by the surgeon. The purpose of this study is to determine the effect of common intraoperative assembly strategies and to identify critical influencing factors on taper stability. ASA with standard and stemless humeral component in combination with concentric Al₂ O₃ heads and eccentric CoCr28Mo6 alloyed humeral heads were tested. Taper angles and surface roughness were determined. Force magnitudes and impact directions were recorded using a sensorized head impactor and a three-dimensional force measuring platform. Subsequently, the axial pull-off forces were measured and taper engagement areas were macroscopically evaluated. In comparison to standard stem tapers that were impacted with an assembly device, stemless tapers were impacted into the artificial bone with significantly lower forces. Taper strength correlates to maximum impact force and was higher for CoCr28Mo6 heads with a mean pull-off ratio of 0.56 than for Al₂ O₃ heads with 0.37. Interestingly, all tapers showed an asymmetric clamping behavior, due to tilting during impaction. This is caused by the variation of the resulting force vector and further promoted by humeral head eccentricity. Assembly technique markedly influences the force magnitude, impact direction, impulse, and consequently taper strength. The resulting force vector and head eccentricity were identified as potential risk factors for taper malalignment.

A comparison of metal/metal and ceramic/metal taper-trunnion modular connections in explanted total hip replacements

Corrosion and wear are commonly found at the taper-trunnion connection of modular total hip arthroplasty (THA) explanted devices. While metal/metal (M/M) modular taper-trunnion connections exhibit more wear/corrosion than ceramic/metal (C/M) modular taper-trunnion connections, damage is present in both, regardless of material. This study used a combination of assessment techniques including clinical data, visual scoring assessment, optical imaging, profilometry, and x-ray photoelectron microscopy (XPS), to investigate wear mechanisms and damage features at the modular taper-trunnion connection of 10 M/M and 8 C/M explanted THAs. No correlation was found between any demographic variable and corrosion wear and assessment scores. All assessment techniques demonstrated that the stem trunnions had more damage than head tapers for both explant groups and agreed that C/M explants had less corrosion and wear compared to M/M explants. However, visual assessment scores differed between assessment techniques when evaluating the tapers and trunnions within the two groups. Profilometry showed an increase (p <.05) in surface roughness for stem trunnions compared to head tapers for both explant groups. X-ray photoelectron spectroscopy performed on deposits from two M/M explants found chromium and molybdenum carbides beneath the surface while chromium sulfate and aged bone mineral were found on the surface suggesting that the debris is a result of corrosion rather than wear. These results indicate that taper-trunnion damage is more prevalent for M/M explants, but C/M explants are still susceptible to damage. More comprehensive analysis of damage is necessary to better understand the origins of taper-trunnion damage.

Variability in stem taper surface topography affects the degree of corrosion and fretting in total hip arthroplasty

Degradation at the modular head-neck interface in total hip arthroplasty (THA) is predominately expressed in the form of corrosion and fretting, potentially causing peri-prosthetic failure by adverse reactions to metal debris. This retrieval study aimed to quantify variations in stem taper surface topographies and to assess the influence on the formation of corrosion and/or fretting in titanium alloy stem tapers combined with metal and ceramic heads. Four hip stem designs (Alloclassic, CLS, Bicontact and SL-Plus) were characterized using high-resolution 3D microscopy, and corrosion and fretting were rated using the Goldberg scoring scheme. Quantification of the taper surface topographies revealed a high variability in surface characteristics between threaded stem tapers: Alloclassic and CLS tapers feature deeply threaded trapezoid-shaped profiles with thread heights over 65 µm. The sawtooth-shaped Bicontact and triangular SL-Plus taper are characterized by low thread heights below 14 µm. Significantly lower corrosion and fretting scores were observed in lightly threaded compared to deeply threaded tapers in ceramic head combinations. No significant differences in corrosion or fretting scores with thread height were found in pairings with metal heads. Understanding the relationship between stem taper surface topography and the formation of corrosion and fretting could help to improve the performance of modern THAs and lead to longer-lasting clinical results.

[Tribology in hip arthroplasty : Benefits of different materials]

When it comes to total hip replacements, choosing the suitable material combination is of clinical relevance. The present review article examines the technical differences in wear and corrosion of the relevant material combinations of ceramics, metals, ceramized metals and various types of polyethylene. The material characteristics, which were often tested under standardized conditions in the laboratory, are compared with clinical results on the basis of evidence-graded clinical studies and on the basis of register studies. This article thus represents an up-to-date snapshot of the expectations and actual clinical outcomes of the present choice of material combinations. It shows that some tendencies from the field of materials research, e.g. with regard to cross-linked polyethylene, coincide with observations from practical clinical experience, while for other materials, a proven technical superiority has not yet been confirmed as an evident advantage in clinical practice.

No radiological and biological sign of trunnionosis with Large Diameter Head Ceramic Bearing Total Hip Arthroplasty after 5 years

BACKGROUND

Trunnionosis of large diameter (LDH) metal-on-metal total hip arthroplasty (THA) was linked to high systemic chromium (Cr) and cobalt (Co) ion levels and local adverse reactions to metal debris (ARMD). The safety of CoC LDH THA is not yet available at mid-term. Measuring whole blood Ti level of ceramic on ceramic (CoC) LDH THA with a titanium (Ti) stem is an indirect way to assess the performance of its head-neck taper modular junction. Therefore, we wanted to determine: (1) if the whole blood Ti ion levels in patients with LDH CoC THA after a minimum of 5 years of implantation is within the expected values for similar well performing Ti THA, (2) if Ti level scientifically increases over time, which would suggest the presence of a progressive modular head/neck junction wear process, (3) if clinical or radiographical manifestations of implant dysfunction are present?

HYPOTHESIS

Ti blood levels of LDH CoC THA will indirectly reflect the expected levels due to passive corrosion of the implants and will be stable over time.

PATIENTS AND METHODS

We report the whole blood Ti, Cr, and Co levels at 5years minimum for 57 patients with unilateral primary LDH CoC THA with head sizes ranging from 36 to 48mm using Ti stem and acetabular component. To compare Ti ion levels modification over time, in 25 patients were a previous measurement (1-3years) was available, we compared it to their last follow-up results (>5 years). Mean Ti level in well performing Ti THAs is recognized to be around 2.0 ug/L. Although, there are no universally accepted Ti levels associated with problematic implant, we used safety threshold of 10 ug/L. Clinical and radiological outcomes were recorded at last follow-up.

RESULTS

At 79 months mean follow-up, all mean Ti levels were 1.9μg/L (min 1.2, max 4.4) and all subject had values below the safety threshold of 10ug/L. In the subgroup of 25 cases with a previous measurement, there was a decrease in mean Ti levels between 20 months and 78 months follow-up (2.2μg/L (1.6-3.9) versus 2.0μg/L (1.4-2.8), p=0.007). No statistically significant relation was observed between Ti level at last FU and bearing diameter (rho=0.046, p=0.0734) or the presence or absence of a Ti adaptor sleeve (p=0.454): 1.94ug/L (min 1.20, max 2.80) versus 1.90ug/L (min 1.20, max 4.40). At last follow up, no patients presented osteolysis signs on radiographs, clinical signs of ARMD or were reoperated. Most patients had excellent clinical with 98% of them reporting minor (29%) or no functional limitation (69%) and 44% perceive their THA as a natural hip joint. However, 3/57patients (5%) temporarily experienced hip squeaking and 18/57 (31%) reported clicking sound.

CONCLUSION

With the tested LDH CoC THA, Ti levels were low and related the uneventful and unavoidable passive corrosion of implant surfaces. Mid-term measurement of Ti in subjects with LDH CoC did not reveal any indirect signs of trunnionosis, which should already be observable by this time.

LEVEL OF EVIDENCE

IV, retrospective study.

Taper junctions in modular hip joint replacements: What affects their stability?

BACKGROUND

Although taper junctions are beneficial in the reconstruction of hip joints, some clinical concerns like the formation of adverse local tissue reactions have recently emerged. These reactions are associated with wear and corrosion products from the interface of insufficient taper connections regarding strength. Commonly used tapers vary in their geometric and topographical design parameter. Therefore, this study aims to evaluate interactions between design and surgical related parameters to the taper connection strength.

METHODS

In this study, the effect of the taper contact situation, surface roughness and head material in combination with assembly force on the taper connection strength were assessed using torque-off tests. Furthermore, the type of use in terms of single-use or re-use of the stem taper was investigated.

RESULTS

The study showed that the impaction force is the predominant factor that determines the taper strength followed by the type of use and the head material. The contact situation seems to slightly influence the determined torque-off moment, whereas the surface topography of the stem taper obviously plays a minor role for the taper connection strength.

CONCLUSION

Clinical users should be aware that an increased assembly force will strengthen the stability of the taper junction, whereas care should be taken when reusing hip stems with metal heads as this may decrease their connection strength.

In vitro fretting crevice corrosion damage of CoCrMo alloys in phosphate buffered saline: Debris generation, chemistry and distribution

Fretting crevice corrosion in modular tapers of total hip replacements has become a major concern in orthopedic medical devices. Solid and ionic debris arising from fretting crevice corrosion have been implicated in device failure and revision surgery. This study aims to use a 2D pin-on-disk fretting corrosion test system to visualize damage progression and debris generation during fretting corrosion of CoCrMo alloys in phosphate buffered saline (PBS). The results provide direct evidence of rapid debris generation during fretting corrosion (after only 12 min of testing). Debris was generated and either extruded from the contact region or impacted into adjacent crevice sites as long as fretting continued. After testing, the fretting region consisted of a damaged and plastically deformed contact region surrounded by a halo of fretting debris consisting entirely of oxides and phosphates within the crevice region. Evidence of pitting corrosion and grain boundary corrosion was observed. Solid debris consisted of chromium (Cr), phosphate (P) and oxygen (O). X-ray photoelectron spectroscopy analysis of the near-fretted metal surface area showed a thicker oxygen (O1s) containing film with the depth profile of O1s above 10% penetrating up to 5.75 nm while the O1s concentration on the unfretted area fell to below 10% after 1 nm depth. Ion concentration in the PBS, measured using inductively coupled mass spectrometry, showed cobalt (Co) ions were most prevalent (1.46 ppm) compared to chromium (Cr) (0.07 ppm) and molybdenum (Mo) (0.05 ppm) (p <0.05). All of these results are consistent with the analysis of in vivo modular taper corrosion processes. STATEMENT OF SIGNIFICANCE: CoCrMo alloys has been widely used as a metallic biomaterial for implant devices and can lose their durability and reliability due to wear, corrosion and tribocorrosion. Debris, as one of the major products of these reactions, is associated with implant device failure. In the first time, we developed a fretting corrosion testing system to visualize the debris generation process in real-time between CoCrMo alloy pin and disk samples. Debris was generated rapidly during fretting corrosion and some of the debris egressed from the crevice site while also accumulating within the crevice area as fretting continued. Our study opens a new method for future studies to advance understanding of debris generation processes during wear and tribocorrosion phenomenon.

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.

Delayed-type Hypersensitivity to Metals in Newly Diagnosed Patients with Nonischemic Dilated Cardiomyopathy

The causes of nonischemic dilated cardiomyopathy are classified as genetic or nongenetic, but environmental factors such as metal pollutants may interact with genetic susceptibility. The presence of metal particles has been detected in the myocardium, including in those patients with dilated cardiomyopathy. It is also known that hypersensitivity reactions can induce inflammation in tissue. The present study aimed to verify if metal-induced delayed-type hypersensitivity is present in patients with nonischemic dilated cardiomyopathy. The patient group consisted of 30 patients with newly diagnosed dilated cardiomyopathy; the control group comprised 41 healthy subjects. All patients and control subjects provided blood samples for lymphocyte transformation testing (MELISA®) to assess possible hypersensitivity to seven common metals. Specific exposure to metals was based on interview data. Results showed that exposure to cadmium and lead (p = 0.0002), aluminum (p = 0.0006), nickel (p = 0.0012), and chromium (p = 0.0065) was more often reported by patients than controls. The patients also had significantly more frequent hypersensitivity reactions to mercury (26.7% vs. 7.3%, p = 0.014624), nickel (40% vs. 12.2%, p = 0.02341), and silver (20% vs. 4.8%, p = 0.025468) than the control group. Patients with dilated cardiomyopathy had greater exposure to certain metals compared with healthy controls. Hypersensitivity to metals was more frequent in patients with dilated cardiomyopathy, suggesting a possible association that warrants further investigation.

Influence of Different Damage Patterns of the Stem Taper on Fixation and Fracture Strength of Ceramic Ball Heads for Total Hip Replacement

Background

Modularity finds frequent application in total hip replacement, allowing a preferable individual configuration and a simplified revision by retaining the femoral stem and replacing the prosthetic head. However, micromotions within the interface between the head and the stem taper can arise, resulting in the release of wear debris and corrosion products. The aim of our experimental study was to evaluate the influence of different taper damages on the fixation and fracture stability of ceramic femoral heads, after static and dynamic implant loading.

Methods

Ceramic ball heads (36 mm diameter) and 12/14 stem tapers made of titanium with various mild damage patterns (intact, scratched, and truncated) were tested. The heads were assembled on the taper with a quasistatic load of 2 kN and separated into a static and a dynamic group afterwards. The dynamic group (n = 18) was loaded over 1.5 million gait cycles in a hip wear simulator (ISO 14242-1). In contrast, the static group (n = 18) was not mechanically loaded after assembly. To determine the taper stability, all heads of the dynamic and static groups were either pulled off (ASTM 2009) or turned off (ISO 7206-16). A head fracture test (ISO 7206-10) was also performed. Subsequent to the fixation stability tests, the taper surface was visually evaluated in terms of any signs of wear or corrosion after the dynamic loading.

Results

In 10 of the 18 cases, discoloration of the taper was determined after the dynamic loading and subsequent cleaning, indicating the first signs of corrosion. Pull-off forces as well as turn-off moments were increased between 23% and 54% after the dynamic loading compared to the unloaded tapers. No significant influence of taper damage was determined in terms of taper fixation strength. However, the taper damage led to a decrease in fracture strength by approximately 20% (scratched) and 40% (truncated), respectively.

Conclusion

The results suggest that careful handling and accurate manufacturing of the stem taper are crucial for the ceramic head fracture strength, even though a mild damage showed no significant influence on taper stability. Moreover, our data indicate that a further seating of the prosthetic head may occur during daily activities, when the resulting hip force increases the assembly load.

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.

In Vitro Evidence for Cell-Accelerated Corrosion Within Modular Junctions of Total Hip Replacements

Corrosion at modular junctions of total hip replacement (THR) remains a major concern today. Multiple types of damage modes have been identified at modular junctions, correlated with different corrosion characteristics that may eventually lead to implant failure. Recently, within the head-taper region of the CoCrMo retrieval implants, cell-like features and trails of etching patterns were observed that could potentially be linked to the involvement of cells of the periprosthetic region. However, there is no experimental evidence to corroborate this phenomenon. Therefore, we aimed to study the potential role of periprosthetic cell types on corrosion of CoCrMo alloy under different culture conditions, including the presence of CoCrMo wear debris. Cells were incubated with and without CoCrMo wear debris (obtained from a hip simulator) with an average particle size of 119 ± 138 nm. Electrochemical impedance spectroscopy (EIS) was used to evaluate the corrosion tendency, corrosion rate, and corrosion kinetics using the media after 24 h of cell culture as the electrolyte. Results of the study showed that there was lower corrosion resistance (p < 0.02) and higher capacitance (p < 0.05) within cell media from macrophages challenged with particles when compared with the other media conditions studied. The potentiodynamic results were also in agreement with the EIS values, showing significantly higher corrosion tendency (low E_corr ) (p < 0.0001) and high I_corr (p < 0.05) in media from challenged macrophages compared with media with H₂ O₂ solution. Overall, the study provides in vitro experimental evidence for the possible role of macrophages in altering the chemical environment within the crevice and thereby accelerating corrosion of CoCrMo alloy. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:393-404, 2020.

Modular junction may be more problematic than bearing wear in metal-on-metal total hip arthroplasty

INTRODUCTION

In total hip arthroplasty (THA), local adverse reaction to metal debris (ARMD) may be caused by abnormal metal ion release from a metal-on-metal (MoM) bearing, or by wear and corrosion of the implant's modular junction. The aim of this study was to compare ion levels and rate of ARMD between patients sharing the same MoM bearing but 1 group having monoblock stems versus another having modular stems.

MATERIALS AND METHODS

Whole blood cobalt (Co) and chromium (Cr) ion concentrations, ARMD rate, revision rate, and function measured by UCLA and WOMAC scores were compared between groups.

RESULTS

ARMD rate was significantly higher in the modular group (46%) compared with the monoblock group (16%, p = 0.031). Revision for ARMD was performed at 52.8 ± 8.1 months in the modular group versus 98.2 ± 15.5 months after primary THA in the monoblock group. ARMD originated from wear and corrosion of the junction between stem and femoral head adapter sleeve in all monoblock cases, and the junction between stem and modular neck in all the modular ones. Cr and Co ions levels were significantly higher in the modular stem group ( p < 0.001 for both).

CONCLUSIONS

Although both groups had MoM bearings, corrosion at stem/neck or neck/head junctions combining dissimilar metal (Ti and Cr-Co) was seen as the source of excess metal ions release leading to ARMD. Poor performance of the modular junction may be more deleterious than wear of the bearing. To avoid such complications, THA femoral stem modular junctions should be eliminated (return to a full monoblock implant) or have improved junction design.

There Is No Significant Difference in Fretting and Corrosion at the Trunnion of Metal and Ceramic Heads

No study has compared the prevalence of fretting and corrosion at the trunnion of cobalt-chrome (Co-Cr) and zirconia ceramic heads in the same patients. The authors sought to compare the prevalence of fretting and corrosion at the trunnion after total hip arthroplasty with a 32-mm Co-Cr or a 32-mm zirconia ceramic head-on-polyethylene bearing. Isolated revision of the ace-tabular components was performed in 78 patients (156 hips) for polyethylene wear and osteolysis of the acetabulum. Seventy-eight Co-Cr head-titanium alloy stem pairs were compared with 78 zirconia ceramic head-titanium alloy stem pairs in the same patients. Using a visual scoring technique, the 156 head-stem pairs were analyzed for the prevalence of fretting and/or corrosion at the trunnion of the stem and the prevalence of metal transfer to the inner taper of the femoral head. Mean patient age was 48 years, and there were 65 men and 13 women. There was no trunnionosis in either group. Prevalence of fretting (81% vs 83%) and corrosion (4% vs 3%) at the trunnion was not significantly different (P=.518 vs .612, respectively) between the 2 groups. The median fretting scores (1.4±1.1 vs 1.2±1.4 points) and corrosion scores (1.2±0.8 vs 1.3±0.9 points) at the trunnion were not significantly different (P=.893 vs .781, respectively) between the 2 groups. Prevalence of metal transfer to the inner taper of the femoral head (8% vs 10%) and the median metal transfer scores (1.2±0.9 vs 1.4±1.1 points) were not significantly different (P=.213 vs .729, respectively) between the 2 groups. [Orthopedics. 2019; 42(1):e99-e103.].

Do Well-functioning THAs Retrieved at Autopsy Exhibit Evidence of Fretting and Corrosion?

BACKGROUND

Our understanding of fretting and corrosion at head-neck junctions in modular THAs in vivo is based largely on the analysis of retrieved implants removed for various diagnoses. Little is known about the condition of head-neck tapers in well-functioning THAs.

QUESTIONS/PURPOSES

Regarding a cohort of well-functioning autopsy-retrieved modular THAs, we asked: (1) Does trunnion geometry or femoral head material affect the pull-off force of the femoral head? (2) Is there a relationship between trunnion damage and length of implantation time, head diameter, and neck length? (3) Does visual damage scoring accurately determine the presence or absence of corrosion on cobalt-chrome trunnions?

METHODS

Sixty-six femoral stems and engaged femoral heads were retrieved at autopsy from 53 patients at Anderson Orthopaedic Research Institute from 1998 to 2014. Ten stems were excluded for low stem design group size or insufficient head-stem clearance for pull-off testing, leaving a cohort of 56 THAs with a median implantation time of 10 years (range, 1-24 years). The femoral stems included three cobalt-chrome (CoCr) designs from a single manufacturer with either a 12/14 or 14/16 trunnion design (N = 36 and 20, respectively) mated with alumina or CoCr heads (N = 13 and 43, respectively). The force required to pull off the femoral heads was measured using a uniaxial load frame according to ASTM F2009-00. Mating surfaces were visually examined to assess the presence and severity of fretting and corrosion using a modified Goldberg scoring system. Three 12/14 trunnions of similar implantation lengths and varied damage scores were selected for imaging with a scanning electron microscope (SEM) and energy dispersive x-ray analysis (EDAX) to confirm the absence or presence of corrosion damage.

RESULTS

No difference was seen in pull-off force between groups based on trunnion geometry and head material (median [range], alumina-12/14: 3127 [2320-6992] N, alumina-14/16: 2670 [1095-7919] N, CoCr-12/14: 2255 [1332-5939] N, CoCr-14/16: 2812 [1655-4246] N; p = 0.132). A positive correlation was found between damage score and length of implantation (ρ = 0.543, p < 0.001). However, no correlation between damage score and either head diameter or neck length was found (ρ = -0.012, p = 0.930 and ρ < 0.001, p = 0.995, respectively). In all, 39 of 56 specimens demonstrated no fretting or corrosion, and 16 specimens had mild damage scores. One specimen demonstrated severe corrosion without visual evidence of fretting. The presence of intergranular corrosion on this trunnion was determined by SEM imaging and EDAX. The absence of corrosion products on two trunnions with no observed damage was confirmed.

CONCLUSIONS

This study found little evidence of fretting and corrosion in a cohort of well-functioning CoCr-CoCr and alumina-CoCr head-neck couples. Further studies are necessary to characterize fretting and corrosion at head-neck junctions of well-functioning implants of other designs and manufacturers.

CLINICAL RELEVANCE

The results from this study suggest that patients with well-functioning THAs using polyethylene bearing surfaces with alumina or CoCr heads appear to be at low risk for trunnion corrosion for the specific CoCr alloy stems and trunnion geometries analyzed here.

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

Mechanically assisted crevice corrosion (MACC) is a mechanism for trunnion damage in total hip arthroplasties (THAs). Retrieval studies have shown reduced MACC-related damage for ceramic heads compared with cobalt-chromium (CoCr) heads. We propose that ceramic heads demonstrate fretting at higher cyclic compressive loads than CoCr heads on titanium alloy trunnions in a simulated corrosion model. A closed electrochemical chamber was used to measure fretting current onset loads for two modern titanium alloy trunnions (Zimmer 12/14 and Stryker V-40) in which trunnion failure has been reported. Ceramic and CoCr alloy 36 + 0 mm heads were impacted on each trunnion and cyclically loaded at 3 Hz with increasing magnitude from 100 to 3,400 N for 540 cycles. Onset load was the cyclic compressive load at which the slope of the average fretting current increased significantly. A CoCr head with V40 trunnion demonstrated the lowest onset load (1,400 N), while the V40 trunnion with a ceramic head showed the highest onset load (2,200 N). Significant differences occurred in average fretting current between head materials for V40 trunnions (p < 0.001) at loads over 2,000 N. CoCr-12/14 and ceramic-12/14 couples demonstrated similar onset loads (2,000 N). All head-trunnion combinations showed cyclical fretting response to loading at 100 N. Head material composition was observed to increase fretting at the taper junction but the effect was taper geometry dependent. Using ceramic heads may reduce the phenomena of trunnion fretting and corrosion but the effect of both trunnion geometry and metallurgy warrants further investigation. Statement of clinical significance: Trunnion corrosion may occur with titanium alloy stems regardless of the head material used. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1630-1636, 2018.

Trunnion corrosion: what surgeons need to know in 2018

AIMS

To present a surgically relevant update of trunnionosis.

MATERIALS AND METHODS

Systematic review performed April 2017.

RESULTS

Trunnionosis accounts for approximately 2% of the revision total hip arthroplasty (THA) burden. Thinner (reduced flexural rigidity) and shorter trunnions (reduced contact area at the taper junction) may contribute to mechanically assisted corrosion, exacerbated by high offset implants. The contribution of large heads and mixed metallurgy is discussed.

CONCLUSION

Identifying causative risk factors is challenging due to the multifactorial nature of this problem. Cite this article: Bone Joint J 2018;100-B(1 Supple A):44-9.

Evidence based recommendations for reducing head-neck taper connection fretting corrosion in hip replacement prostheses

INTRODUCTION

This systematic review seeks to summarise the published studies investigating prosthetic design, manufacture and surgical technique's effect on fretting corrosion at the head-neck taper connection, and provide clinical recommendations to reduce its occurrence.

METHODS

PubMed, MEDLINE and EMBASE electronic databases were searched using the terms taper, trunnion, cone and head-neck junction. Articles investigating prosthetic design, manufacture and surgical technique's effect on fretting corrosion were retrieved, reviewed and graded according to OCEBM levels of evidence and grades of recommendation.

RESULTS

The initial search yielded 1,224 unique articles, and 91 were included in the analysis.

CONCLUSIONS

There is fair evidence to recommend against the use of high offset femoral heads, larger diameter femoral heads, and to pay particular consideration to fretting corrosion's progression with time and risk with heavier or more active patients. Particular to metal-on-metal hip prostheses, there is fair evidence to recommend positioning the acetabular component to minimise edge loading. Particular to metal-on-polyethylene hip prostheses, there is fair evidence to recommend the use of ceramic femoral heads, against use of cast cobalt alloy femoral heads, and against use of low flexural rigidity femoral stems. Evidence related to taper connection design is largely conflicting or inconclusive. Head-neck taper connection fretting corrosion is a multifactorial problem. Strict adherence to the guidelines presented herein does not eliminate the risk. Prosthesis selection is critical, and well-controlled studies to identify each design parameter's relative contribution to head-neck taper connection fretting corrosion are required.

Comparison of metal ion levels in patients with hip resurfacing versus total hip arthroplasty

Mechanical wear at the articular surface and corrosive processes at modular junctions, such as the trunnion, are responsible for metal ions production. We retrospectively reviewed 64 patients who underwent THA with a metal on metal bearing surface and 34 patients with hip Resurfacing. Metal ion measurements, six-week post-op radiographs, and functional scores were included in the analysis. Cobalt ion levels were significantly elevated in THA patients, 2.95 μg/L as compared to resurfacing patients, (2.95 versus 1.30 μg/L, p < 0.0005). Chromium levels were not significantly different between THA patients and resurfacing patients (1.05 versus 1.00 μg/L, p = 0.529).

Squeaking in ceramic-on-ceramic hips: No evidence of contribution from the trunnion morse taper

Squeaking in ceramic-on-ceramic (CoC) total hip arthroplasty (THA) was investigated with an acoustic monitoring device to distinguish between squeaking emanating from the trunnion morse taper (TMT) connection versus the articular surface. 82 patients with implant problems scheduled for revision were selected and acoustic emissions (AE) with simple movements monitored. Five of these patients with CoC implants underwent surgery and their retrieved implant components were analyzed in vitro. In vivo recordings of all 82 patients found audible squeaks produce frequency content across the entire 0-50 kHz spectrum. Of the five CoC implants the in vivo peak frequency range of flexion/extension motions was 0.8 kHz and comparable to the range of in vitro testing (0.2 kHz). In vitro TMT connection motions were very large comparatively, producing a higher average peak frequency range of 22.5 kHz. All retrieved implants showed evidence of wear at the TMT connection. These findings suggest, the TMT connection does not directly cause audible squeaking. Wear occurring at this junction may contribute to debris which disrupt lubrication, increase friction, and produce noise. This observation supports current evidence suggesting that squeaking is from the bearing surface. Our findings are the first to demonstrate that in CoC THA the recordable noise of a hip squeak does not originate nor have contribution from the TMT connection. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1793-1798, 2017.

In Vivo Damage of the Head-Neck Junction in Hard-on-Hard Total Hip Replacements: Effect of Femoral Head Size, Metal Combination, and 12/14 Taper Design

Recently, concerns have been raised about the potential effect of head-neck junction damage products at the local and systemic levels. Factors that may affect this damage process have not been fully established yet. This study investigated the possible correlations among head-neck junction damage level, implant design, material combination, and patient characteristics. Head-neck junctions of 148 retrieved implants were analysed, including both ceramic-on-ceramic (N = 61) and metal-on-metal (N = 87) bearings. In all cases, the male taper was made of titanium alloy. Damage was evaluated using a four-point scoring system based on damage morphology and extension. Patient age at implantation, implantation time, damage risk factor, and serum ion concentration were considered as independent potential predicting variables. The damage risk factor summarises head-neck design characteristics and junction loading condition. Junction damage correlated with both implantation time and damage factor risk when the head was made of ceramic. A poor correlation was found when the head was made of cobalt alloy. The fretting-corrosion phenomenon seemed mainly mechanically regulated, at least when cobalt alloy components were not involved. When a component was made of cobalt alloy, the role of chemical phenomena increased, likely becoming, over implantation time, the damage driving phenomena of highly stressed junctions.

A combined experimental and finite element approach to analyse the fretting mechanism of the head-stem taper junction in total hip replacement

Fretting corrosion at the taper interface of modular hip implants has been implicated as a possible cause of implant failure. This study was set up to gain more insight in the taper mechanics that lead to fretting corrosion. The objectives of this study therefore were (1) to select experimental loading conditions to reproduce clinically relevant fretting corrosion features observed in retrieved components, (2) to develop a finite element model consistent with the fretting experiments and (3) to apply more complicated loading conditions of activities of daily living to the finite element model to study the taper mechanics. The experiments showed similar wear patterns on the taper surface as observed in retrievals. The finite element wear score based on Archard’s law did not correlate well with the amount of material loss measured in the experiments. However, similar patterns were observed between the simulated micromotions and the experimental wear measurements. Although the finite element model could not be validated, the loading conditions based on activities of daily living demonstrate the importance of assembly load on the wear potential. These findings suggest that finite element models that do not incorporate geometry updates to account for wear loss may not be appropriate to predict wear volumes of taper connections.

Retrieval analysis of metal and ceramic femoral heads on a single CoCr stem design

Objectives

The use of ceramic femoral heads in total hip arthroplasty (THA) has increased due to their proven low bearing wear characteristics. Ceramic femoral heads are also thought to reduce wear and corrosion at the head-stem junction with titanium (Ti) stems when compared with metal heads. We sought to evaluate taper damage of ceramic compared with metal heads when paired with cobalt chromium (CoCr) alloy stems in a single stem design.

Methods

This retrieval study involved 48 total hip arthroplasties (THAs) with CoCr V40 trunnions paired with either CoCr (n = 21) or ceramic (n = 27) heads. The taper junction of all hips was evaluated for fretting/corrosion damage and volumetric material loss using a roundness-measuring machine. We used linear regression analysis to investigate taper damage differences after adjusting for potential confounding variables.

Results

We measured median taper material loss rates of 0.210 mm³/year (0.030 to 0.448) for the metal head group and 0.084 mm³/year (0.059 to 0.108) for the ceramic group. The difference was not significant (p = 0.58). Moreover, no significant correlation between material loss and implant or patient factors (p > 0.05) was found.

Conclusions

Metal heads did not increase taper damage on CoCr trunnions compared with ceramic heads from the same hip design. The amount of material released at the taper junctions was very low when compared with available data regarding CoCr/Ti coupling in metal-on-metal bearings.

Cite this article: A. Di Laura, H. Hothi, J. Henckel, I. Swiatkowska, M. H. L. Liow, Y-M. Kwon, J. A. Skinner, A. J. Hart. Retrieval analysis of metal and ceramic femoral heads on a single CoCr stem design. Bone Joint Res 2017;6:–350. DOI: 10.1302/2046-3758.65.BJR-2016-0325.R1.

Choosing a Femoral Head: A Survey Study of Academic Adult Reconstructive Surgeons

BACKGROUND

Our aim was to examine how academic adult reconstructive surgeons have interpreted evidence on femoral head material in total hip arthroplasty (THA).

METHODS

A 16-question survey to evaluate attitudes toward ceramic and cobalt-chrome head use was emailed to 274 faculty at 42 US adult reconstruction fellowship programs.

RESULTS

With 116 respondents, the response rate was 42.2%. Faculty use ceramic heads 72.9% of the time. The most common reason why respondents do not use ceramic heads is cost (44.8%). Ninety-four percent of faculty have observed head-neck taper corrosion in cobalt-chrome on polyethylene THA, while 9.5% of faculty have observed head-neck taper corrosion in ceramic on polyethylene THA. Only 6.0% of surgeons have seen Biolox Delta ceramic fracture.

CONCLUSION

Adult reconstruction thought leaders are guided by evidence suggesting that with ceramic heads, taper corrosion and fracture are rare. Cost and personal experience also strongly influence their implant selection. Efforts to equalize cost of ceramic and cobalt-chrome heads may free surgeons to practice in a purely evidence-based fashion.

Comparative study of material loss at the taper interface in retrieved metal-on-polyethylene and metal-on-metal femoral components from a single manufacturer

There have been a number of reports on the occurrence of taper corrosion and/or fretting and some have speculated on a link to the occurrence of adverse local tissue reaction specifically in relation to total hip replacement which have a metal-on-metal bearing. As such a study was carried out to compare the magnitude of material loss at the taper in a series of retrieved femoral heads used in metal-on-polyethylene bearings with that in a series of retrieved heads used in metal-on-metal bearings. A total of 36 metal-on-polyethylene and 21 metal-on-metal femoral components were included in the study all of which were received from a customer complaint database. Furthermore, a total of nine as-manufactured femoral components were included to provide a baseline for characterisation. All taper surfaces were assessed using an established corrosion scoring method and measurements were taken of the female taper surface using a contact profilometry. In the case of metal-on-metal components, the bearing wear was also assessed using coordinate metrology to determine whether or not there was a relationship between bearing and taper material loss in these cases. The study found that in this cohort the median value of metal-on-polyethylene taper loss was 1.25 mm³ with the consequent median value for metal-on-metal taper loss being 1.75 mm³. This study also suggests that manufacturing form can result in an apparent loss of material from the taper surface determined to have a median value of 0.59 mm³. Therefore, it is clear that form variability is a significant confounding factor in the measurement of material loss from the tapers of femoral heads retrieved following revision surgery.

Effects of tissue digestion solutions on surface properties of nitinol stents

Analysis of explanted medical implants can provide a wealth of knowledge about device safety and performance. However, the quality of information may be compromised if the methods used to clean tissue from the device disturb the retrieved condition. Common solutions used to digest tissue may adversely affect the surface of the device and its severity can be material and processing dependent. In this study, two groups of stents made from the same material (Nitinol) were shape set in a salt pot (SP) or further processed by mechanical polishing (MP) and then immersed in one of three tissue digestion solutions (TDS): nitric acid (HNO₃ ), sodium hydroxide (NaOH), or papain enzyme (papain). Nickel (Ni) ion concentrations were measured for each stent-TDS combination and post-immersion stent surface constituents, morphology and oxide depths were compared to baseline samples. Exposure to the HNO₃ TDS resulted in relatively high Ni ion release and surface damage for both stent types. Papain TDS induced a greater Ni ion release than NaOH TDS, however, both were significantly lower than HNO₃ . The NaOH TDS increased the oxide layer thickness on MP stents. In contrast, all other stent immersions resulted in thinner oxide layers. For the Nitinol finishes used in this study, HNO₃ is not recommended while papain and NaOH solutions may be appropriate depending on the post-retrieval analysis performed. This study elucidates the importance of preliminary testing for TDS selection and how the surface finish can affect the sensitivity of a material to a TDS. 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 331-339, 2018.

Trunnion Corrosion in Metal-on-Polyethylene Total Hip Arthroplasty: A Case Series

INTRODUCTION

Modular total hip arthroplasty implants can help the operating surgeon reproduce the optimum limb length and offset; however, the modularity can lead to fretting and corrosion with associated metal-related problems. Although metal-on-metal bearings are often reported to have problems, recent case reports suggest that the problems can occur with any articulation, usually as a result of problems at the head/neck junction.

METHODS

We retrospectively reviewed three cases of a specific implant combination with nontraumatic trunnion failure, with two cases presenting as acute complete dissociation of the femoral head from the neck.

RESULTS

All three cases had failure of the Accolade TMZF plus stem and trunnion (Stryker) that progressed rapidly from the onset of symptoms. The most likely contributing factors to failure were large femoral head size, high horizontal offset, a low angled neck, and a β titanium alloy taper with a cobalt-chromium head.

CONCLUSION

We recommend regular follow-up of all patients with Accolade TMZF stems, and patients should be advised to seek immediate medical attention if they have any new mechanical symptoms in a metal-on-polyethylene total hip arthroplasty. Providers should specifically look for any alteration of alignment between the femoral head and neck in follow-up radiographs.

Pseudotumour formation and subsequent resolution in metal-on-metal total hip arthroplasty following revision: Instructional review and an illustrative case report with revision using a dual mobility design

The use of large-diameter metal-on-metal (MoM) components in total hip arthroplasty (THA) is associated with an increased risk of early failure due to adverse local tissue reaction to metal debris (ARMD) in response to the release of metal ions from the bearing couple and/or head-neck taper corrosion. The aim of this paper was to present a review of the incidence and natural history of ARMD and the forms of treatment, with a focus on the need for and extent of resection or debulking of the pseudotumour. An illustrative case report is presented of a patient with an intra-pelvic pseudotumour associated with a large diameter MoM THA, which was treated successfully with revision of the bearing surface to a dual mobility couple and retention of the well-fixed acetabular and femoral components. The pseudotumour was left in situ Resolution of the intra-pelvic mass and normalisation of metal ion levels was observed seven months post-operatively. Cite this article: Bone Joint J 2016;98-B:736-40.

Metal in Total Hip Arthroplasty: Wear Particles, Biology, and Diagnosis

Total hip arthroplasty (THA) has been performed for nearly 50 years. Between 2006 and 2012, more than 600,000 metal-on-metal THA procedures were performed in the United States. This article reviews the production of metal wear debris in a metal-on-metal articulation and the interaction of cobalt and chromium ions that ultimately led to a dramatic decline in the use of metal-on-metal THA articulations. Additionally, the article reviews mechanisms of metal wear, the biologic reaction to cobalt and chromium ions, the clinical presentation of failing metal-on-metal articulations, and current diagnostic strategies. Further, the article discusses the use of inflammatory markers, metal ion levels, radiographs, metal artifact reduction sequence magnetic resonance imaging, and ultrasound for failed metal-on-metal THA procedures. When adopting new technologies, orthopedic surgeons must weigh the potential increased benefits against the possibility of new mechanisms of failure. Metal-on-metal bearings are a prime example of the give and take between innovation and clinical results, especially in the setting of an already successful procedure such as THA. [Orthopedics. 2016; 39(6):371-379.].

Does Surface Topography Play a Role in Taper Damage in Head-neck Modular Junctions?

BACKGROUND

There are increasing reports of total hip arthroplasty failure subsequent to modular taper junction corrosion. The surfaces of tapers are machined to have circumferential machining marks, resulting in a surface topography of alternating peaks and valleys on the scale of micrometers. It is unclear if the geometry of this machined surface topography influences the degree of fretting and corrosion damage present on modular taper junctions or if there are differences between modular taper junction material couples.

QUESTIONS/PURPOSES

(1) What are the differences in damage score and surface topography between CoCr/CoCr and CoCr/Ti modular junctions? (2) How are initial surface topography, flexural rigidity, taper angle mismatch, and time in situ related to visual taper damage scores for CoCr/CoCr couples? (3) How are initial surface topography, flexural rigidity, taper angle mismatch, and time in situ related to visual taper damage scores for CoCr/Ti couples?

METHODS

Damage on stem and head tapers was evaluated with a modified Goldberg score. Differences in damage scores were determined between a group of 140 CoCr/CoCr couples and 129 CoCr/Ti couples using a chi-square test. For a subgroup of 70 retrievals, selected at random, we measured five variables, including initial stem taper machining mark height and spacing, initial head taper roughness, flexural rigidity, and taper angle mismatch. All retrievals were obtained at revision surgeries. None were retrieved as a result of metal-on-metal failures or were recalled implants. Components were chosen so there was a comparable number of each material couple and damage score. Machining marks around the circumference of the tapers were measured using white light interferometry to characterize the initial stem taper surface topography in terms of the height of and spacing between machining mark peaks as well as initial head taper roughness. The taper angle mismatch was assessed with a coordinate measuring machine. Flexural rigidity was determined based on measurements of gross taper dimensions and material properties. Differences of median or mean values of all variables between material couples were determined (Wilcoxon rank-sum tests and t-tests). The effect of all five variables along with time in situ on stem and head taper damage scores was tested with a multiple regression model. With 70 retrievals, a statistical power of 0.8 could be achieved for the model.

RESULTS

Damage scores were different between CoCr/CoCr and CoCr/Ti modular taper junction material couples. CoCr/CoCr stem tapers were less likely to be mildly damaged (11%, p = 0.006) but more likely to be severely damaged (4%, p = 0.02) than CoCr/Ti stem tapers (28% and 1%, respectively). CoCr/CoCr couples were less likely to have moderately worn head tapers (7% versus 17%, p = 0.003). Stem taper machining mark height and spacing and head taper roughness were 11 (SD 3), 185 (SD 46), and 0.57 (SD 0.5) for CoCr/CoCr couples and 10 (SD 3), 170 (SD 56), and 0.64 (SD 0.4) for CoCr/Ti couples, respectively. There was no difference (p = 0.09, p = 0.1, p = 0.16, respectively) for either factor between material couples. Larger stem taper machining mark heights (p = 0.001) were associated with lower stem taper damage scores, and time in situ (p = 0.006) was associated with higher stem taper damage scores for CoCr/CoCr material couples. Stem taper machining marks that had higher peaks resulted in slower damage progression over time. For CoCr/Ti material couples, head taper roughness was associated with higher stem (p = 0.001) and head taper (p = 0.003) damage scores, and stem taper machining mark height, but not time in situ, was associated with lower stem taper damage scores (p = 0.007).

CONCLUSIONS

Stem taper surface topography was related to damage scores on retrieved head-neck modular junctions; however, it affected CoCr/CoCr and CoCr/Ti couples differently.

CLINICAL RELEVANCE

A taper topography of circumferential machining marks with higher peaks appears to enable slower damage progression and, subsequently, a reduction of the reported release of corrosion products. This may be of interest to implant designers and manufacturers in an effort to reduce the effects of metal release from modular femoral components.

Clinical outcome of design modifications to the CLS Spotorno Stem in total hip replacement

PURPOSE

historically, the original CLS Spotorno Stem has demonstrated excellent survival. The design of this stem was recently modified, resulting in the introduction of a shorter, modular version (CLS Brevius). The purpose of the current study was to evaluate the functional, radiological and survivorship outcomes of the cementless CLS Brevius Stem in a multi-surgeon, single center, consecutive series study at two years post-surgery.

METHODS

the Authors performed 170 total hip arthroplasties in 155 patients using the shorter, triple-taper stem design (CLS Brevius). The patients' diagnoses were primary hip osteoarthritis (OA) in 74.4%, secondary hip OA in 22.6%, and post-traumatic hip OA in 3%. All operations were performed through a mini-posterior approach, with the patient in the lateral decubitus position. The mean follow-up was 32 months (24-44 months). Outcome was assessed using the Harris Hip Score (HHS).

RESULTS

the mean HHS improved from 32 preoperatively to 92 points at final follow-up, while the stem survival rate was 99.4%. Overall, the results were excellent in148 hips (87%), good in 14 hips (8.2%), fair in six hips (3.6%), and poor in two hips (1.2%). Intraoperative complications included a calcar fissure in three hips (1.7%). Correct femoral offset was reproduced in 97% while the planned center of hip rotation was achieved in 98%. Only one hip underwent early stem revision; this was due to major subsidence.

CONCLUSIONS

the modified CLS stem design showed excellent short-term results with a low rate of early postoperative complications. One of the main findings of this study was the high correlation between the planned femoral offset and center of hip rotation and the final radiographic measurements. This high reproducibility, which indicates the ability of the system to restore normal hip anatomy, is indeed due to the extensive modularity that characterizes this stem system. Long-term follow-up studies are necessary to fully compare the outcomes of the new design with its highly successful predecessor.

LEVEL OF EVIDENCE

Level IV, therapeutic cases series.

Corrosion of the Head-neck Junction After Total Hip Arthroplasty

Corrosion of the head-neck junction of implants used in total hip arthroplasty is a complex problem. Clinical severity appears to be multifactorial, and the predictive variables have yet to be consistently identified in the literature. Corrosion should be considered in the differential diagnosis of hip pain following total hip arthroplasty regardless of the type of bearing surface used. The most common presentation, pain followed by instability, is similar to complications associated with metal-on-metal articulations. The diagnosis of implant corrosion of the head-neck junction can be challenging; an infection workup should be performed along with analysis of serum metal ion levels and cross-sectional imaging. In the short term, a well-fixed stem may be retained, and the exchange of an isolated head with a ceramic femoral head seems to be a promising option for certain implants. Further research with longer follow-up is warranted, and high levels of evidence are needed to determine whether this approach is generalizable.

Characterization of the fretting corrosion behavior, surface and debris from head-taper interface of two different modular hip prostheses

Modular hip prostheses are flexible to match anatomical variations and to optimize mechanical and tribological properties of each part by using different materials. However, micromotions associated with the modular components can lead to fretting corrosion and, consequently, to release of debris which can cause adverse local tissue reactions in human body. In the present study, the surface damage and residues released during in vitro fretting corrosion tests were characterized by stereomicroscope, SEM and EDS. Two models of modular hip prosthesis were studied: Model SS/Ti Cementless whose stem was made of ASTM F136 Ti-6Al-4V alloy and whose metallic head was made of ASTM F138 austenitic stainless steel, and Model SS/SS Cemented with both components made of ASTM F138 stainless steel. The fretting corrosion tests were evaluated according to the criteria of ASTM F1875 standard. Micromotions during the test caused mechanical wear and material loss in the head-taper interface, resulting in fretting-corrosion. Model SS/SS showed higher grade of corrosion. Different morphologies of debris predominated in each model studied. Small and agglomerated particles were observed in the Model SS/Ti and irregular particles in the Model SS/SS. After 10 million cycles, the Model SS/Ti was more resistant to fretting corrosion than the Model SS/SS.

Corrosion at the head-neck interface of current designs of modular femoral components

There is increasing global awareness of adverse reactions to metal debris and elevated serum metal ion concentrations following the use of second generation metal-on-metal total hip arthroplasties. The high incidence of these complications can be largely attributed to corrosion at the head-neck interface. Severe corrosion of the taper is identified most commonly in association with larger diameter femoral heads. However, there is emerging evidence of varying levels of corrosion observed in retrieved components with smaller diameter femoral heads. This same mechanism of galvanic and mechanically-assisted crevice corrosion has been observed in metal-on-polyethylene and ceramic components, suggesting an inherent biomechanical problem with current designs of the head-neck interface.

We provide a review of the fundamental questions and answers clinicians and researchers must understand regarding corrosion of the taper, and its relevance to current orthopaedic practice.

Cite this article: Bone Joint J 2016;98-B:579–84.

Ceramic Heads Decrease Metal Release Caused by Head-taper Fretting and Corrosion

BACKGROUND

Metal release resulting from taper fretting and corrosion is a clinical concern, because wear and corrosion products may stimulate adverse local tissue reactions. Unimodular hip arthroplasties have a conical taper between the femoral head (head bore taper) and the femoral stem (stem cone taper). The use of ceramic heads has been suggested as a way of reducing the generation of wear and corrosion products from the head bore/stem cone taper junction. A previous semiquantitative study found that ceramic heads had less visual evidence of fretting-corrosion damage compared with CoCr heads; but, to our knowledge, no studies have quantified the volumetric material loss from the head bore and stem cone tapers of a matched cohort of ceramic and metal heads.

QUESTIONS/PURPOSES

We asked: (1) Do ceramic heads result in less volume of material loss at the head-stem junction compared with CoCr heads; (2) do stem cone tapers have less volumetric material loss compared with CoCr head bore tapers; (3) do visual fretting-corrosion scores correlate with volumetric material loss; and (4) are device, patient, or intraoperative factors associated with volumetric material loss?

METHODS

A quantitative method was developed to estimate volumetric material loss from the head and stem taper in previously matched cohorts of 50 ceramic and 50 CoCr head-stem pairs retrieved during revision surgery for causes not related to adverse reactions to metal particles. The cohorts were matched according to (1) implantation time, (2) stem flexural rigidity, and (3) lateral offset. Fretting corrosion was assessed visually using a previously published four-point, semiquantitative scoring system. The volumetric loss was measured using a precision roundness machine. Using 24 equally spaced axial traces, the volumetric loss was estimated using a linear least squares fit to interpolate the as-manufactured surfaces. The results of this analysis were considered in the context of device (taper angle clearance, head size, head offset, lateral offset, stem material, and stem surface finish) and patient factors that were obtained from the patients' operative records (implantation time, age at insertion, activity level, and BMI).

RESULTS

The cumulative volumetric material losses estimated for the ceramic cohort had a median of 0.0 mm(3) per year (range, 0.0-0.4 mm(3)). The cumulative volumetric material losses estimated for the CoCr cohort had a median of 0.1 mm(3) per year (range, 0.0-8.8 mm(3)). An order of magnitude reduction in volumetric material loss was found when a ceramic head was used instead of a CoCr head (p < 0.0001). In the CoCr cohort, the femoral head bore tapers had a median material loss of 0.02 mm(3) (range, 0.0-8.7 mm(3)) and the stem cone tapers had a median material loss of 0.0 mm(3) (range, 0.0-0.32 mm(3)/year). There was greater material loss from femoral head bore tapers compared with stem cone tapers in the CoCr cohort (p < 0.001). There was a positive correlation between visual scoring and volumetric material loss (Spearman's ρ = 0.67, p < 0.01). Although visual scoring was effective for preliminary screening to separate tapers with no or mild damage from tapers with moderate to severe damage, it was not capable of discriminating in the large range of material loss observed at the taper surfaces with moderate to severe fretting-corrosion damage, indicated with a score of 3 or 4. We observed no correlations between volumetric material loss and device and patient factors.

CONCLUSIONS

The majority of estimated material loss from the head bore-stem cone junctions resulting from taper fretting and corrosion was from the CoCr head bore tapers as opposed to the stem cone tapers. Additionally, the total material loss from the ceramic cohort showed a reduction in the amount of metal released by an order of magnitude compared with the CoCr cohort.

CLINICAL RELEVANCE

We found that ceramic femoral heads may be an effective means by which to reduce metal release caused by taper fretting and corrosion at the head bore-stem cone modular interface in THAs.