Taper corrosion in modular hip prostheses: analysis of serum metal ions in 19 patients

Comparison of chromium and cobalt serum levels between a modular neck stem and its monoblock counterpart in primary total hip arthroplasty

BACKGROUND

The addition of junctions in modular stems implies a greater susceptibility to corrosion.

PURPOSE

The aim of this study is to compare serum chromium and cobalt levels after using a bimodular stem and its monoblock counterpart in primary total hip arthroplasty. Postoperative clinical scores were also compared.

PATIENTS AND METHODS

A prospective cohort study between 2012 and 2015 was designed. One arm of the cohort included patients with the cementless modular neck stem H-Max M® and the other with the cementless monoblock stem counterpart H-Max S®.

RESULTS

No statistically significant difference was found in chromium value between groups (p = 0.621) at two years postoperative. Cobalt value was higher in the modular group (p = < 0.001). No statistically significant difference was found in clinical postoperative scores except for the Harris Hip Score, with better results at six months in modular group (p = 0.007).

CONCLUSIONS

Higher serum cobalt level in the modular group has limited the use of modular stems in our daily practice. Advantages of modular stem were not found.

LEVEL OF EVIDENCE

II.

Metal-on-Metal Hip Arthroplasty: A Comprehensive Review of the Current Literature

Metal-on-metal (MoM) total hip arthroplasty has been widely used since the end of the 20th century, although rates have now decreased due to concerns regarding adverse reactions and failure rates. The MoM implant has been replaced with other materials, such as ceramic-on-ceramic (CoC) and metal-on-polyethylene (MoP). This literature review looks at the past and present use of MoM prostheses to assess whether the turn away from MoM use is justified. Online literature searches were performed on PubMed, Ovid Medical Literature Analysis and Retrieval System Online (MEDLINE), and Web of Science online databases using the search terms "MoM and (ARMD and ALVAL)" (ARMD: adverse reaction to metal debris; ALVAL: aseptic lymphocyte-dominant vasculitis-associated lesion). A total of 64 relevant titles were included in the review. Although risk factors for adverse reactions and the causes of ARMD are generally agreed upon, more work is required to further understand the specific thresholds of blood metal ion levels that can be used to consistently identify ARMD and excessive metal wear-debris in patients who have not had their MoM implants revised. Metal-on-metal devices are not an acceptable option for total hip arthroplasties (THAs) in their current formulation due to the high rate and risk of ARMD. Some MoM hip resurfacing operations are appropriate for very carefully selected patients who are fully aware of the risks posed by the implant. It is recommended that device-specific thresholds for metal ion levels be developed to identify patients at risk of ARMD locally and systemically while using auxiliary tools to assist diagnosis, such as metal artefact reduction sequences (MARS)-MRI and hip scoring tools. Further work should investigate device-specific blood metal ion levels, the systemic effects of raised metal ion concentrations secondary to MoM arthroprosthetic wear, and the potential risks of ARMD caused by wear from tapered stems (including the implications this has for patients with CoC and MoP prostheses).

Metallosis in Total Hip Arthroplasty

» Metallosis is a rare but significant complication that can occur after total hip arthroplasty (THA) for a variety of reasons but most commonly in patients with metal-on-metal implants.» It is characterized by the visible staining, necrosis, and fibrosis of the periprosthetic soft tissues, along with the variable presence of aseptic cysts and solid soft tissue masses called pseudotumors secondary to the corrosion and deposition of metal debris.» Metallosis can present with a spectrum of complications ranging from pain and inflammation to more severe symptoms such as osteolysis, soft tissue damage, and pseudotumor formation.» Workup of metallosis includes a clinical evaluation of the patient's symptoms, imaging studies, serum metal-ion levels, and intraoperative visualization of the staining of tissues. Inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein along with intraoperative frozen slice analysis may be useful in certain cases to rule out concurrent periprosthetic joint infection.» Management depends on the severity and extent of the condition; however, revision THA is often required to prevent rapid progression of bone loss and tissue necrosis.

Breakage of Tapered Junctions of Modular Stems in Revision Total Hip Arthroplasty—High Incidence in a Consecutive Series of a Single Institution

Background: Modularity in revision THA (RTHA) has become accepted during the last three decades. Nevertheless, specific risks of modularity of current revision devices such as breakage of taper junctions occur during follow-up. Data reporting failure rates are predominantly given by the manufacturers but independent data acquisition is missing so far. Questions/Purposes: 1. What time-related risk of breakage of taper junction between neck and body of an established modular revision device can be expected in a consecutive single institutional series and a mid-term follow-up? 2. Are there specific factors influencing breakage in this cohort? Materials and Methods: A retrospective analysis was performed of a consecutive series of 89 cases after femoral revision using a tapered modular revision stem. Mean follow-up period was 7.1 (range: 3.0–13.7) years. Breakage of stem as failure criteria of the implant was investigated with a Kaplan–Meier analysis. Results: Breakage of taper junctions occurred in four patients during follow-up showing a time-depending implant survival of 94.2 (95% CI: 88.6–100%) after 13.7 years. Implant survival of stems with lateralized necks of 87.4 (95% CI: 75.6–100%) after 13.7 years was significantly lower compared to the standard offset variant with 100% after 13.5 years (log rank test p = 0.0283). Chi square test also revealed a significantly higher risk of breakage of lateralized necks compared to standard offset pieces (p = 0.0141). Three of four patients were obese with a mean BMI of 37.9 kg/m2. Grade of obesity (grade 1 or higher) had significant influence on risk of breakage. Survival of the implant was significantly lower in obese patients with at least grade 1 obesity compared to patients with a BMI < 30 kg/m2 (82.9 (95% CI: 64.9–100%) after 11.6 years vs. 98.4 (95% CI: 95.3–100%) after 13.7 years; log-rank p = 0.0327). Conclusions: Cumulative risk for failure of taper junctions was high in this consecutive single institutional cohort and may further increase during follow-up. As independent data acquisition in registries is missing, failure rate may be higher than reported data of the manufacturers. The use of lateralized offset necks in obese patients of at least grade 1 obesity showed a significantly higher risk of breakage. The use of monobloc revision devices may be an option, but randomized control trials are currently missing to establish standardized treatment protocols considering individual risks for both monobloc and/or modular implants.

Cobalt Levels and Pseudotumor Characteristics Vary due to Metal Ion Source: Modular Femoral Neck vs Metal-on-Metal Articulations

BACKGROUND

This study examines cobalt levels and pseudotumor characteristics in a non-recalled modular femoral prosthesis. We sought to determine relationships between serum cobalt levels and pseudotumors following modular and metal-on-metal (MoM) total hip arthroplasty (THA), the location and size of pseudotumors, and changes to pseudotumor grade over time.

METHODS

We retrospectively evaluated a cohort of 190 primary THAs implanted with a dual-modular femoral stem by one surgeon from 2005 to 2013. One hundred seventeen THAs used a cobalt-chromium modular neck (CoCrMN) component and non-MoM articulation, 63 THAs had a titanium neck component and MoM articulation, and 10 had a titanium neck component and polyethylene liner. Serum ion levels were recorded for all patients. Pseudotumor grade and location were measured by musculoskeletal-trained radiologists.

RESULTS

Cobalt levels did not correlate to time after index arthroplasty. In the CoCrMN group, cobalt levels were elevated in 11 of 19 (57.9%) patients with pseudotumor compared to 14 of 19 (73.7%) in the MoM group. Pseudotumors were more often located lateral to the hip joint in the CoCrMN group compared to anteromedial following MoM arthroplasty. In CoCrMN THAs, pseudotumors were visualized in 12 of 51 (23.5%) initial MARS MRIs within 40 months compared to 5 of 66 (7.6%) performed later (P = .02).

CONCLUSION

Pseudotumor characteristics differ between patients with CoCrMN designs vs those with an MoM articulation. Normal serum cobalt levels did not exclude the presence of a pseudotumor and routine MARS MRI should be included in follow-up of patients with this CoCrMN prostheses.

Risk Stratification Algorithm for Management of Head-Neck Taper Tribocorrosion in Patients with Metal-on-Polyethylene Total Hip Arthroplasty: Consensus Statement of the American Association of Hip and Knee Surgeons, the American Academy of Orthopaedic Surgeons, and The Hip Society

Adverse local tissue reactions (ALTRs) were initially reported as complications associated with metal-on-metal (MoM) bearings; however, there is increasing concern regarding the occurrence of adverse local tissue reactions from mechanically assisted crevice corrosion (MACC) at the femoral head-neck junction or between other modular junctions of the implant containing cobalt chromium parts in patients with metal-on-polyethylene (MoP) bearings. ALTR due to MACC at the head-neck junction has primarily been reported in association with cobalt chromium alloy femoral heads. As pain following total hip arthroplasty may have various intrinsic and extrinsic causes, a systematic approach to evaluation (risk stratification algorithm) based on the currently available data is recommended to optimize patient management. Evaluation should begin by ruling out common causes of pain, including component loosening and periprosthetic joint infection. While specialized tests such as blood metal analysis and metal artifact reduction sequence magnetic resonance imaging (MARS MRI) are useful modalities in evaluating for ALTRs, over-reliance on any single investigative tool in the clinical decision-making process should be avoided. There should be a low threshold to perform a systematic evaluation for ALTR due to MACC in patients with metal-on-polyethylene total hip arthroplasty as early recognition and diagnosis is critical, as delays in appropriate treatment initiation may result in soft-tissue damage, which complicates surgical treatment and is associated with a higher risk of complications and poorer patient outcomes.

Catastrophic failure of femoral stem modular junction when combined with metal-on-metal bearing in comparison to ceramic-on-ceramic: A retrospective cohort study

BACKGROUND

Metal ion release from total hip arthroplasty's (THA) metal-on-metal (MoM) bearing surfaces or head-neck modular junction (trunnionosis) has been identified as a major cause of adverse reaction to metal debris (ARMD). No study has compared the effects of these bearing couples when combined with modular neck femoral stems (MNFS) (i.e. did a modular CoCr have a higher effect than large MoM bearings on whole blood ion concentrations and ARMD). Therefore we did a retrospective comparative analysis of prospectively collected data aiming to: (1) assess the difference in metal ion release between a group of MoM and CoC bearings implanted with a non-cemented MNFS; (2) compare the ARMD and the related revision rates between the two bearing types; (3) compare the patients' HOOS and Harris Hip scores.

HYPOTHESIS

Metal ion levels and complications rate will be higher in MoM group.

METHODS

Thirty hips received the same short MNFS with modular CoCr. Seventeen had CoC bearing (16=36mm) and 13 large diameter head (LDH) MoM bearing (mean=50mm, 44-54mm) Both groups had whole blood Cobalt (Co) and Chromium (Cr) concentrations measurements at last follow up or before revision surgery (if any) and were compared to 41 control individuals without implants. ARMD, revision rates and other complications were censed. Functional outcome differences between operative groups were assessed with HOOS and Harris Hip scores.

RESULTS

Mean whole blood Co and Cr were 1.9μg/L (0.1-10.6 min-max) and 1.2μg/L (0.2-4.6 min-max) in the CoC group and 12.7μg/L (2.5-40.7 min-max) and 8.2μg/L (2.8-40.6 min-max) for MoM group. Controls presented whole blood Co and Cr levels of 0.2μg/L (0.04-0.2 min-max) and 0.6μg/L (0.1-0.7 min-max) respectively. CoC had significantly higher whole blood metal ion concentrations than controls, while MoM had significantly higher concentrations than both (p<0.001). MoM had a 9/13 (69%) revision rate due to ARMD (with stem-neck junction corrosion and wear were present in all cases) while the CoC had none. Functional scores at last follow up did not statistically differ between groups (Harris: CoC=94.1±8.4 vs MoM 91.8±14.8 (p=0.22) and CoC HOOS 90.2±10.7 vs 75.6±21.7 (p=0.08)).

CONCLUSION

In our study, MNFS with CoCr modular neck released metal ion systemically, as shown in CoC THAs, but when combined with MoM LDH bearings, that elevation was significantly higher. In MNFS MoM, these high metal ion levels translated into a dramatic ARMD related revision rate where stem-neck junction corrosion and wear were present in all cases. More research is required to understand the effects of MoM bearing on neck-stem junctions, and its mechanisms of corrosion.

LEVEL OF EVIDENCE

III; retrospective comparative study.

Does modularity of metal-on-metal hip implants increase cobalt: chromium ratio?

BACKGROUND

Blood metal ion levels are used in the surveillance of metal-on-metal (MoM) hip implants. Modular implants contain an extra source of metal debris that may affect the ratio of metal ions in the blood.

METHODS

This was a retrospective study of 503 patients with hip replacements made by a single manufacturer (Smith & Nephew, Warwick, UK) with the same bearing surface. There were 54 total hip arthroplasties, 35 Birmingham Mid-Head Resections and 414 hip resurfacings. Whole blood metal ion levels and their ratios were analysed to investigate the effect of a modular junction.

RESULTS

The cobalt:chromium ratios were greater in the total hip arthroplasty group (mean 2.3:1) when compared to the resurfacings group (mean 1.3:1, p = <0.05) and Birmingham Mid-Head Resection group (mean 1.1:1, p = 0.11).

CONCLUSIONS

This study demonstrated a trend for a higher cobalt:chromium ratio in patients with MoM total hip replacement that may be due to metal debris from the modular stem-head junction. Further work is required to correlate clinical data with retrieval analysis to confirm the effect of taper material loss on the cobalt:chromium ratio.

Sensitivity and Specificity of Serum and Synovial Fluid Markers in Diagnosis of Infection in Head-Neck Taper Corrosion of Metal-On-Polyethylene Total Hip Arthroplasty

BACKGROUND

The accurate diagnosis of periprosthetic joint infection (PJI) in the setting of adverse local tissue reactions in patients with metal-on-polyethylene (MoP) total hip arthroplasty (THA) secondary to head-neck taper junction corrosion is challenging as it frequently has the appearance of purulence. The aim of this study is to evaluate the utility of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and synovial fluid markers in diagnosing PJI in failed MoP THA due to head-neck taper corrosion.

METHODS

A total of 89 consecutive patients with MoP THA with head-neck taper corrosion in 2 groups was evaluated: (1) infection group (n = 11) and (2) noninfection group (n = 78). All patients had highly crossed polyethylene with cobalt chromium femoral heads and had preoperative synovial fluid aspiration. In addition, serum cobalt and chromium levels were analyzed.

RESULTS

The optimal cutoff value for synovial white blood cell was 2144 with 93% sensitivity and 84% specificity. Neutrophil count optimal cutoff value was 82% with 93% sensitivity and 82% specificity. Receiver operating characteristic analysis of ESR and CRP determined optimal cutoff at 57 mm/h and 35 mg/L with 57% sensitivity and 94% specificity and 93% sensitivity and 76% specificity, respectively. There were no significant differences in metal ion levels between the infected and noninfected groups.

CONCLUSION

The results of this study suggest that ESR and CRP are useful in excluding PJI, whereas both synovial white blood cell count and neutrophil percentage in hip aspirate are useful markers for diagnosing infection in MoP THA patients with head-neck taper corrosion associated adverse local tissue reaction.

MARS MRI Characteristics of Adverse Local Tissue Reactions in Taper Corrosion of Metal-On-Polyethylene THA Differ From Metal-On-Metal THA

BACKGROUND

Metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) has been recommended as a cross-sectional imaging modality in clinical evaluation of adverse local tissue reactions (ALTRs) in metal-on-metal (MoM) patients and metal-on-polyethylene (MoP) patients with taper corrosion. The aim of the study was to compare MARS MRI characteristics of ALTR in MoM total hip arthroplasty (THA) with ALTR in MoP THA with modular taper corrosion.

METHODS

A total of 197 patients with ALTR were evaluated: 86 patients with MoM THA; 37 MoP patients with head-neck taper corrosion; and 74 MoP patients with neck-stem dual taper corrosion. MARS MRI scans were evaluated to identify location, size, type of ALTR (I-III), and associated ALTR synovitis (cystic, solid, and mixed).

RESULTS

MARS MRI characteristics of ALTR were significantly different between the MoM and MoP groups (P = .017). The MoP group demonstrated the highest proportion of thick-walled cystic masses type II (56.7% in head-neck taper corrosion MoP and 46.5% in dual taper corrosion MoP vs 28.7% in MoM), whereas the MoM group had the highest proportion of thin-walled cystic masses type I. MoM implants (96.8%) were significantly more likely to have ALTR in multiple locations compared with both MoP groups (P = .001).

CONCLUSION

This study demonstrates that MARS MRI characteristics of ALTR differ by bearing type with a significantly higher percentage of mixed type and solid type ALTR in the taper corrosion MoP THA compared with MoM THA. This information provides clinically useful information in evaluation of symptomatic MoP and MoM THA patients for ALTRs.

Patients With Modular-Neck Total Hip Arthroplasty: A Brief Five-Year Follow-Up Study

BACKGROUND

We have previously reported the early clinical results of a modular-neck stem identifying an early 2-year revision rate of 13% due to neck-stem corrosion. This report updates our findings to a midterm mean follow-up of 5 years.

METHODS

This is a consecutive retrospective review of 186 modular-neck hips in 175 patients with a mean follow-up period was 60.1 ± 22.9 months (range 24-100). We reviewed clinical findings, routine radiographs, detailed imaging (metal artifact reduction software-magnetic resonance imaging, ultrasound), and serum ion levels of cobalt and chromium. We performed a survival analysis with the endpoint defined as revision total hip arthroplasty due to neck-stem corrosion.

RESULTS

We revised 41 hips (22.0%) for neck-stem corrosion. Clinical symptoms (groin pain ± local swelling) were consistently present in those that came for revision. Mean serum cobalt ion levels increased as time passed in all patients. Detailed image findings showed that larger fluid collections and local soft tissue masses were seen predominately in symptomatic patients. However, 14% of patients who underwent revision did not have positive magnetic resonance imaging or ultrasound findings. The survival rate was 87% (95% confidence interval 81-92) at 3 years postoperatively and 72% (95% confidence interval 64-80) at 7 years postoperatively.

CONCLUSION

The revision rate for this modular-neck stem due to neck-stem corrosion at mid-term follow-up almost doubled in comparison to previous short-term results. It seems reasonable to consider clinical follow-up alone as symptoms, rather than blood testing for ion levels, seem to be the defining characteristic of failure.

How to proceed with asymptomatic modular dual taper hip stems in the case of acetabular revision

How to proceed with a clinically asymptomatic modular Metha® Ti alloy stem with dual taper CoCr neck adapter in case of acetabular revision? To systematically answer this question the status of research and appropriate diagnostic methods in context to clinically symptomatic and asymptomatic dual taper stem-neck couplings has been evaluated based on a systematic literature review. A retrieval analysis of thirteen Metha® modular dual taper CoCr/Ti alloy hip stems has been performed and a rational decision making model as basis for a clinical recommendation was developed. From our observations we propose that in cases of acetabular revision, that for patients with a serum cobalt level of > 4 µg/L and a Co/Cr ratio > 3.6, the revision of the modular dual taper stem may be considered. Prior to acetabular revision surgery a systematic diagnostic evaluation should be executed, using specific tests such as serum metal (Co, Cr) ion analysis, plain antero-posterior and lateral radiographs and cross-sectional imaging modalities (Metal Artefact Reduction Sequence Magnetic Resonance Imaging). For an asymptomatic Metha® dual taper Ti alloy/CoCr stem-neck coupling at the stage of acetabular revision careful clinical decision making according to the proposed model should be followed and overreliance on any single examination should be avoided, considering the complete individual differential diagnosis and patient situation.

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.

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.

The Distribution and Severity of Corrosion Damage at Eight Distinct Zones of Metallic Femoral Stem Implants

Metallic taper junctions of modular total hip replacement implants are analysed for corrosion damage using visual scoring based on different granularity levels that span from analysing the taper holistically to dividing the taper into several distinct zones. This study aims to objectively explore the spatial distribution and the severity of corrosion damage onto the surface of metallic stem tapers. An ordinal logistic regression model was developed to find the odds of receiving a higher score at eight distinct zones of 137 retrieved stem tapers. A method to find the order of damage severity across the eight zones is introduced based on an overall test of statistical significance. The findings show that corrosion at the stem tapers occurred more commonly in the distal region in comparison with the proximal region. Also, the medial distal zone was found to possess the most severe corrosion damage among all the studied eight zones.

Withdrawn: A Randomized Controlled Trial Comparing Modular and Nonmodular Neck Versions of a Titanium Stem

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Sensitivity and Specificity of Metal Ion Level in Predicting Adverse Local Tissue Reactions Due to Head-Neck Taper Corrosion in Primary Metal-on-Polyethylene Total Hip Arthroplasty

BACKGROUND

There is increasing concern regarding the occurrence of adverse local tissue reactions (ALTRs) in metal-on-polyethylene (MoP) total hip arthroplasty (THA) patients due to mechanically assisted crevice corrosion at the head-neck modular taper junction. The utility of metal ion levels in evaluating MoP patients with head-neck taper has not been fully characterized. This study aimed to investigate the sensitivity and specificity of serum metal ions as a predictor of ALTR in MoP THA patients.

METHODS

A total of 62 MoP THA patients in 2 cohorts were investigated: (1) ALTR on metal artifact reduction sequence magnetic resonance imaging (n = 43) and (2) without ALTR on metal artifact reduction sequence magnetic resonance imaging (n = 19). Receiver-operating characteristic curve was constructed to determine the sensitivity and specificity using different metal ion thresholds and the optimal metal ion cutoff values.

RESULTS

The presence of ALTR was associated with significantly higher cobalt (8.9 ng/mL vs 0.3 ng/mL, P < .001), chromium (2.26 ng/mL vs 0.21 ng/mL, P < .001), and Co/Cr ratio (5.9 vs 2.0, P < .001). The sensitivity and specificity for cobalt (1 ng/mL) was 95% and 94% and for Co/Cr ratio (2) was 83% and 72%, respectively.

CONCLUSIONS

Although metal ion levels alone should not be relied on as the sole parameter to determine revision surgery, serum cobalt level of >1 ng/mL (1 ppb) and Co/Cr ratio >2 thresholds provide evidence-based practical information for surgeons when interpreting metal ion levels in MoP THA patients for clinically relevant head-neck taper corrosion.

Effect of Femoral Stem Modular Neck's Material on Metal Ion Release

Background:

In recent decades, the popularity of modular necks in total hip arthroplasty (THA) has increased since modular necks offer the potential to restore the patient’s native anatomy, and thus improve stability. Unfortunately, modular necks are associated with higher complication rates, including implant fracture and modular junction corrosion with adverse local tissue reaction to metal debris.

Objective:

The objective of this study was to determine the impact of modular neck material on titanium (Ti), chrome (Cr), and cobalt (Co) metal ion levels in patients who underwent a THA with Ti femoral stem, Ti or CrCo modular neck, and ceramic-on-ceramic (CoC) bearing.

Methods:

Whole blood Ti, Cr, and Co levels were compared at a minimum 1-year follow-up in 36 patients who underwent unilateral, primary CoC large-diameter head THA with Profemur^® Preserve modular femoral stems (MicroPort, Arlington, TX, USA).

Results:

Higher Co concentrations were observed in the CrCo modular neck group (0.46 versus 0.26 µg/l in the Ti neck group, P=0.004) and higher Ti concentrations were observed in the Ti modular neck group (1.98 vs 1.59 µg/l in the CrCo neck group, P=0.007). However, these differences were not clinically meaningful since the absolute values remained within what is considered the safe range of Ti, Cr, and Co ions in whole blood. No patients were re-operated or revised.

Conclusion:

Modular neck materials had an impact on whole blood metal ion levels but the concentrations measured remained within the safe range at 1-year follow-up. There were no indirect signs of modular junction corrosion with either CrCo or Ti femoral necks.

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).

Modular Neck vs Nonmodular Femoral Stems in Total Hip Arthroplasty-Clinical Outcome, Metal Ion Levels, and Radiologic Findings

BACKGROUND

Modular neck femoral stem (MNFS) for total hip arthroplasty (THA) was introduced to optimize the outcome, but created concerns about pain, elevated blood metal ion levels, and adverse reaction to metal debris such as pseudotumors (PTs), related to corrosion between femoral neck and stem. We compared these outcomes in patients with MNFS or nonmodular femoral stem (NFS) THA.

METHODS

Thirty-three patients with unilateral MNFS THA were compared with 30 patients with unilateral NFS THA. Levels of pain, serum cobalt, serum chromium were determined. Magnetic resonance imaging was performed to describe PT and fatty atrophy of muscles.

RESULTS

The MNFS and NFS group had a mean follow-up of 2.3 and 3.1 years, respectively. Four and 13 patients in the MNFS and NFS group had pain, respectively (P = .005). The MNFS group had higher levels of serum cobalt (P < .0001) and chromium (P = .006). PTs were present in both the MNFS (n = 15) and NFS (n = 7) groups (P = .066). PTs were related to serum cobalt (P = .04) but not to pain or serum chromium. Fatty atrophy prevalence in the piriformis and gluteal muscles were higher in patients with MNFS (P = .009 and P = .032, respectively).

CONCLUSION

More patients in the NFS group had pain. Serum cobalt and chromium levels were higher in the MNFS group. Prevalence of PTs was twice as high in the MNFS group, but the difference was insignificant.

Assessment of Corrosion, Fretting, and Material Loss of Retrieved Modular Total Knee Arthroplasties

BACKGROUND

Modular junctions in total hip arthroplasties have been associated with fretting, corrosion, and debris release. The purpose of this study is to analyze damage severity in total knee arthroplasties of a single design by qualitative visual assessment and quantitative material loss measurements to evaluate implant performance and patient impact via material loss.

METHODS

Twenty-two modular knee retrievals of the same manufacturer were identified from an institutional review board-approved database. Junction designs included tapers with an axial screw and tapers with a radial screw. Constructs consisted of 2 metal alloys: CoCr and Ti6Al4V. Components were qualitatively scored and quantitatively measured for corrosion and fretting. Negative values represent adhered material. Statistical differences were analyzed using sign tests. Correlations were tested with a Spearman rank order test (P < .05).

RESULTS

The median volumetric material loss and the maximum linear depth for the total population were -0.23 mm³ and 5.84 μm, respectively. CoCr components in mixed metal junctions had higher maximum linear depth (P = .007) than corresponding Ti components. Fretting scores of Ti6Al4V alloy components in mixed metal junctions were statistically higher than the remaining groups. Taper angle did not correlate with material loss.

CONCLUSION

Results suggest that CoCr components in mixed metal junctions are more vulnerable to corrosion than other components, suggesting preferential corrosion when interfacing with Ti6Al4V. Overall, although corrosion was noted in this series, material loss was low, and none were revised for clinical metal-related reaction. This suggests the clinical impact from corrosion in total knee arthroplasty is low.

The use of femoral stems with exchangeable necks in primary total hip arthroplasty increases the rate of revision

Aims

Femoral stems with exchangeable (modular) necks were introduced to offer surgeons an increased choice when determining the version, offset and length of the femoral neck during total hip arthroplasty (THA). It was hoped that this would improve outcomes and reduce complications, particularly dislocation. In 2010, the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) first reported an increased rate of revision after primary THA using femoral stems with an exchangeable neck. The aim of this study was to provide a more comprehensive up-to-date analysis of primary THA using femoral stems with exchangeable and fixed necks.

Materials and Methods

The data included all primary THA procedures performed for osteoarthritis (OA), reported to the AOANJRR between 01 September 1999 and 31 December 2014. There were 9289 femoral stems with an exchangeable neck and 253 165 femoral stems with a fixed neck. The characteristics of the patients and prostheses including the bearing surface and stem/neck metal combinations were examined using Cox proportional hazard ratios (HRs) and Kaplan-Meier estimates of survivorship.

Results

It was found that prostheses with an exchangeable neck had a higher rate of revision and this was evident regardless of the bearing surface or the size of the femoral head. Exchangeable neck prostheses with a titanium stem and a cobalt-chromium neck had a significantly higher rate of revision compared with titanium stem/titanium neck combinations (HR 1.83, 95% confidence interval 1.49 to 2.23, p < 0.001). Revisions were higher for these combinations compared with femoral stems with a fixed neck.

Conclusion

There appears to be little evidence to support the continued use of prostheses with an exchangeable neck in primary THA undertaken for OA. Cite this article: Bone Joint J 2017;99-B:766–73.

Sensitivity and Specificity of Metal Ion Levels in Predicting "Pseudotumors" due to Taper Corrosion in Patients With Dual Taper Modular Total Hip Arthroplasty

BACKGROUND

Currently, no serum metal ion threshold exists to identify adverse tissue reactions in total hip arthroplasty (THA) patients with taper corrosion. Our study aims to investigate the sensitivity and specificity of serum metal ions in detecting taper corrosion related pseudotumors in patients with dual taper modular THA.

METHODS

A total of 148 patients with dual taper modular THA were investigated: (1) 90 patients with pseudotumors detected with metal artifact reduction sequence-magnetic resonance imaging (MARS-MRI) and (2) 58 patients without pseudotumors on MARS-MRI. Receiver operating characteristic curves were constructed to determine the sensitivity and specificity using different metal ion thresholds. The severity of intraoperative tissue damage was correlated with preoperative metal ion levels.

RESULTS

Pseudotumor was associated with higher cobalt (5.0 μg/L vs 3.7 μg/L, P < .01) and Co/Cr ratio (6.0 vs 3.7, P < .01). The sensitivity and specificity for cobalt level of 2.8 μg/L and Co/Cr ratio of 3.8 in detecting taper corrosion-related pseudotumors on MARS-MRI was 88% and 32% and 70% and 50%, respectively. Higher intraoperative tissue damage grades demonstrated significantly higher Co/Cr ratios (8.6 vs 3.4, P = .03).

CONCLUSION

Although metal ion levels alone should not be relied on as the sole parameter to determine revision surgery, cobalt level >2.8 μg/L and the Co/Cr ratio >3.8 are useful clinical diagnostic adjuncts in the systematic clinical evaluation for taper corrosion-related adverse tissue reactions in patients with dual modular taper THA.

Metal ion levels in ceramic-on-ceramic THR with cobalt-chrome modular necks: analysis of cobalt and chromium serum levels in 23 healthy hip patients

BACKGROUND

Modular necks in total hip replacement (THR) can be a source of metal ion release.

METHODS

We measured the level of cobalt (Co) and chromium (Cr) ions in the serum of 23 healthy volunteers with a well-functioning ceramic-on-ceramic THR of a particular design, containing a cobalt-chrome (Co-Cr) stem and a Co-Cr modular neck.

RESULTS

Average Co in serum was 1,71 µg/l; median Co was 1.50 µg/l. No patient had Co levels higher than 3.70 µg/l. Average Cr level was 0.49 µg/l; in all but one patient Cr was below the detection limit (<0.50 µg/l). Co was higher for varus necks compared to all other subtypes: 2.14 µg/l vs 1.58 µg/l (p<0.05). The same system with Titanium modular necks shows lower Co serum levels: 1.26 µg/l (p<0.01 ). In conclusion, the hybrid THR Profemur Xm® - Procotyle L® with a Co-Cr modular neck on a Co-Cr stem design shows very low Cr ion serum levels in a randomly selected group of well-functioning hip patients.

CONCLUSIONS

Co ion serum levels are low, but significantly higher for 8° varus necks, and Co levels are significantly higher than values of this system with a Titanium modular neck.

How to Approach a Recalled Dual Modular Hip Implant: An Update

BACKGROUND

The aim of this study was to provide an update on the "Modular taper junction corrosion and failure: how to approach a recalled total hip arthroplasty implant" (Pivec et al JOA 2014) publication.

METHODS

We performed a comprehensive review of the literature in English, with search terms referencing to the diagnosis, management, and outcomes of patients who underwent total hip arthroplasty with a recalled dual modular hip implant.

RESULTS

Based on this review and the new guidelines by the American Academy of Orthopedic Surgeons and the Hip Society, we propose an updated algorithm for the diagnosis and management of patients with these recalled implants.

CONCLUSION

When encountering patients with these prostheses, it is imperative to take a step-by-step approach to evaluate whether patients are having potential complications. We hope that this has further clarified the appropriate steps that need to be carried out when confronted with these recalled devices.

Asymptomatic Pseudotumors in Patients with Taper Corrosion of a Dual-Taper Modular Femoral Stem: MARS-MRI and Metal Ion Study

BACKGROUND

Modularity in total hip arthroplasty facilitates intraoperative restoration of patient anatomy. Although dual-taper modular total hip arthroplasty offers potential advantages for optimizing the hip center of rotation, it has been associated with modular taper corrosion. This corrosion has led to adverse local tissue reactions (pseudotumors) at the neck-stem junction and elevated metal-ion levels. However, the occurrence of taper-corrosion-related pseudotumors in patients who remain asymptomatic following total hip arthroplasty with a dual-taper modular femoral stem remains largely unknown. The aims of this study were (1) to determine the prevalence of asymptomatic pseudotumors by utilizing metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) and (2) compare serum metal-ion levels between symptomatic and asymptomatic patients with a dual-taper modular stem total hip replacement.

METHODS

We performed a retrospective cross-sectional study of 97 consecutive patients who had been treated with a dual-taper modular femoral stem total hip arthroplasty. Eighty-three patients were stratified into symptomatic and asymptomatic groups and evaluated with MARS-MRI, measurement of serum metal-ion levels, and the University of California at Los Angeles (UCLA) functional hip score.

RESULTS

The prevalence of pseudotumors as determined with MARS-MRI was 15% in our asymptomatic patients and 36% in the overall cohort. The median serum cobalt level and cobalt/chromium ratio were significantly higher in patients with a pseudotumor than in those without a pseudotumor (8.0 versus 2.0 μg/L [p = 0.004] and 10.3 versus 2.4 μg/L [p = 0.012], respectively). However, there was no significant difference in the serum cobalt level or cobalt/chromium ratio between symptomatic patients with a pseudotumor and asymptomatic patients with a pseudotumor (7.6 versus 6.2 μg/L [p = 0.37] and 8.3 versus 10.6 μg/L [p = 0.46], respectively). The UCLA scores of asymptomatic patients with a pseudotumor were similar to those of patients without a pseudotumor (6.7 versus 6.6).

CONCLUSIONS

The prevalence of asymptomatic taper-corrosion-related pseudotumors on MARS-MRI in this study demonstrated that the absence of symptoms does not exclude the presence of adverse local tissue reactions. Elevated cobalt levels and cobalt/chromium ratios were associated with the presence of pseudotumors in asymptomatic and symptomatic patients. Cross-sectional imaging such as MARS-MRI is indicated for patients with elevated metal-ion levels. A longitudinal study is required to determine whether asymptomatic patients with taper-corrosion-related pseudotumors will develop symptoms with time.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Sequelae of large-head metal-on-metal hip arthroplasties: Current status and future prospects

Large-head metal-on-metal (MoM) bearings were re-popularised in the late 1990s with the introduction of modern hip resurfacing (HR), followed closely by large metal head total hip arthroplasty (THA). A worldwide increase in the use of MoM hip arthroplasty subsequently saw a sharp decline, due to serious complications.MoM was rapidly adopted in the early 2000s until medical device alerts were issued by government regulatory agencies and national and international organisations, leading to post-marketing surveillance and discontinuation of these implants.Guidelines for MoM hip implant follow-up differ considerably between regulatory authorities worldwide; this can in part be attributed to missing or conflicting evidence.The authors consider that the use of large-head MoM THA should be discontinued. MoM HR should be approached with caution and, when considered, should be used only in patients who meet all of the recommended selection criteria, which limits its indications considerably.The phased introduction of new prostheses should be mandatory in future. Close monitoring of outcomes and long-term follow-up is also necessary for the introduction of new prostheses. Cite this article: van Lingen CP, Zagra LM, Ettema HB, Verheyen CC. Sequelae of large-head metal-on-metal hip arthroplasties: current status and future prospects. EFORT Open Rev 2016;1:345-353. DOI: 10.1302/2058-5241.1.160014.

Magnetic Resonance Imaging Predicts Adverse Local Tissue Reaction Histologic Severity in Modular Neck Total Hip Arthroplasty

BACKGROUND

The association between advanced imaging, serum metal ion levels, and histologic adverse local tissue reaction (ALTR) severity has not been previously reported for Rejuvenate modular neck femoral stems.

METHODS

A cohort of 90 patients with 98 Rejuvenate modular neck femoral stems was revised by a single surgeon from July 2011 to December 2014. Before revision, patients underwent multiacquisition variable resonance image combination sequence magnetic resonance imaging (MRI), and serum cobalt and chromium ion levels were measured. Histologic samples from the revision surgery were scored for synovial lining, inflammatory infiltrate, and tissue organization as proposed by Campbell. Regression based on the generalized estimating equations approach was used to assess the univariate association between each MRI, demographic, and metal ion measure and ALTR severity while accounting for the correlation between bilateral hips. Random forest analysis was then used to determine the relative importance of MRI characteristics, demographics, and metal ion levels in predicting ALTR severity.

RESULTS

Synovial thickness as measured on MRI was found to be the strongest predictor of ALTR histologic severity in a recalled modular neck femoral stem.

CONCLUSION

MRI can accurately describe ALTR in modular femoral neck total hip arthroplasty. MRI characteristics, particularly maximal synovial thickness and synovitis volume, predicted histologic severity. Serum metal ion levels do not correlate with histologic severity in Rejuvenate modular neck total hip arthroplasty.

High serum ion levels in Conserve Plus big femoral head cemented total hip arthroplasty

AIM

We report the short-term clinical, radiographic and ion level data of the Conserve Plus metal-on-metal (MoM) big femoral head (BFH) total hip arthroplasty (THA), used with a cemented cobalt-chrome (Co-Cr) Profemur Xm stem and a titanium (Ti) modular neck.

RESULTS

In a consecutive series of 40 hips, survivorship at 3 years was 92.5% with revision for any reason. Average Harris Hip Score was 91.3. There were no implant loosenings. No osteolysis was observed. 5 patients had signs of adverse local tissue reaction (ALTR); their clinical scores were not different from the whole cohort. All but 1 patient had their Co serum ion levels measured. The average Co level was 14,1 µg/l (range 0.9-29.0; median 13.0 µg/l). Clinical scores did not correlate with ion level data. A comparative group of 42 hip resurfacing arthroplasties from the same manufacturer had significantly lower serum Co levels: 1.51 µg/l (range 0.9-4.0; median 0.9 µg/l).

CONCLUSIONS

All patients with the MoM BFH THA design should be followed regularly and should have ion level testing.

Effects of Cobalt and Chromium Levels Following Modular Hip Stem Total Hip Arthroplasty

Due to the increased number of revision total hip arthroplasties (THAs) to correct pain secondary to fretting from modular hip stems, this study was conducted in an effort to correlate objective findings of serum cobalt (Co) levels, serum chromium (Cr) levels, and/or reactive tissue seen on metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) with a patient's need for revision THA. The study group comprised 66 patients, 18 of whom received MARS MRI. Serum Co levels, serum Cr levels, and standard numeric rating scale for pain were documented for all patients. Statistical analysis was then performed to determine whether there was a correlation between the aforementioned variables and the need for revision THA. Serum Cr levels were higher in patients with positive reactive tissue findings on MARS MRI, although this only approached significance (P=.083). Serum Co levels were higher in those undergoing revision THA, but this also only approached significance (P=.076). Pain scores were significantly different between those undergoing revision and those not (P<.001). It is the opinion of the authors that there is no objective finding in this study that can be used to identify patients who require revision THA secondary to fretting of a modular hip stem prosthesis. Only a patient's stated pain level can assist a surgeon in the decision-making process regarding the need for revision THA secondary to fretting. [Orthopedics.2016; 39(5):288-292.].

Metal ion levels in ceramic-on-ceramic THR with modular necks: analysis of cobalt and chromium serum levels in 30 healthy hip patients

BACKGROUND

Modular necks in total hip replacement (THR) can be a source of metal ion release. There are no data to date on the level of cobalt and chromium ions in the serum of patients with a cobalt-chrome stem and a titanium modular neck.

METHODS

Serum ion levels were measured in healthy volunteers with a well-functioning ceramic-on-ceramic THR.

RESULTS

Average cobalt in serum was 1.21 µg/l for unilateral THR and 2.2 µg/l for bilateral THR. No patient had cobalt levels higher than 2.4 µg/l. No patient had measurable chromium levels. There were no differences in cobalt levels for hips with short necks versus hips with long necks.

CONCLUSIONS

The hybrid THR Profemur® Xm - Procotyl® L with a titanium modular neck on a cobalt-chrome stem design shows no signs of abnormal toxic ion levels (cobalt or chromium) in a randomly selected group of well-functioning hip patients.

Metal Ion Levels Are Not Correlated With Histopathology of Adverse Local Tissue Reactions in Taper Corrosion of Total Hip Arthroplasty

BACKGROUND

The underlying biological mechanism in the formation of adverse local tissue reaction in taper corrosion of total hip arthroplasty (THA) remains unknown. This study evaluated whether there was a dose-dependent relationship between metal ion levels, intraoperative tissue damage and ALVAL (aseptic lymphocyte-dominated vasculitis-associated lesion) scores in dual taper THA patients who underwent revisions for taper corrosion.

METHODS

We performed a retrospective review of 31 dual taper THA patients who underwent revision surgery from May 2013 to October 2013. Preoperative serum metal ion levels, intraoperative tissue damage grading, and ALVAL scores were reviewed. Multivariate analysis was performed to determine if an association existed between metal ion levels, intraoperative tissue damage, and ALVAL scores.

RESULTS

Findings consistent with adverse local tissue reaction were found in all cases. We noted 10 patients with low, 8 with moderate, and 13 with high ALVAL scores, respectively. For intraoperative tissue damage, we recorded 2 (grade 1), 22 (grade 2) and 7 (grade 3) cases. Preoperatively, there was preferential elevation of serum cobalt (3.8 ng/mL, 2.3-17.0) compared to serum chromium (1.0 ng/mL, 0.2-5.8). There was no correlation between preoperative metal ion levels and intraoperative tissue damage (R = -0.06, P = .74) or ALVAL scores (R = -0.04, P = .481). There was also no correlation between intraoperative tissue damage and ALVAL score (R = -0.06, P = .73).

CONCLUSION

There was no significant correlation between ALVAL scores and prerevision surgery metal ion levels or intraoperative tissue damage, suggesting that the biological mechanism of histologic morphology cannot be solely attributed to elevated metal ion levels and is likely multifactorial, reflecting a complex interplay between implant and patient factors.

Systemic Metal Ion Levels in Patients With Modular-Neck Stems: A Prospective Cohort Study

BACKGROUND

Recent registry data reveal that modular-neck hip prostheses are associated with increased revision rates compared to fixed-neck stems. Poor implant survival has been associated to corrosion at the neck-stem junction, inducing metal ion release and subsequently adverse local tissue reactions. Data on metal ion release on the neck-stem junction of such stems are scarce. The purpose of this study was to evaluate corrosion at this interface by determining metal ion release.

METHODS

Serum and whole blood metal ion levels of 40 patients after 1 year of implantation of a modular-neck stem (titanium stem and cobalt-chromium neck) were compared with 10 patients with a monobloc version of the stem (all titanium) and 10 patients having no implant at all.

RESULTS

Seven of 40 patients (18%) with a modular-neck stem had cobalt or chromium concentrations >2 μg/L. These patients underwent magnetic resonance imaging using metal artifact reduction sequences, which revealed a pseudotumor in 1 patient.

CONCLUSION

Corrosion at the neck-stem junction of modular-neck stems is a reported phenomenon, which is in part reflected by elevated systemic ion levels. The use of such implants should be restricted to a minimum, and screening algorithms of patients with such implants must be developed.

Histopathological characterization of corrosion product associated adverse local tissue reaction in hip implants: a study of 285 cases

Background

Adverse local tissue reaction (ALTR), characterized by a heterogeneous cellular inflammatory infiltrate and the presence of corrosion products in the periprosthetic soft tissues, has been recognized as a mechanism of failure in total hip replacement (THA). Different histological subtypes may have unique needs for longitudinal clinical follow-up and complication rates after revision arthroplasty. The purpose of this study was to describe the histological patterns observed in the periprosthetic tissue of failed THA in three different implant classes due to ALTR and their association with clinical features of implant failure.

Methods

Consecutive patients presenting with ALTR from three major hip implant classes (N = 285 cases) were identified from our prospective Osteolysis Tissue Database and Repository. Clinical characteristics including age, sex, BMI, length of implantation, and serum metal ion levels were recorded. Retrieved synovial tissue morphology was graded using light microscopy. Clinical characteristics and features of synovial tissue analysis were compared between the three implant classes. Histological patterns of ALTR identified from our observations and the literature were used to classify each case. The association between implant class and histological patterns was compared.

Results

Our histological analysis demonstrates that ALTR encompasses three main histological patterns: 1) macrophage predominant, 2) mixed lymphocytic and macrophagic with or without features of associated with hypersensitivity/allergy or response to particle toxicity (eosinophils/mast cells and/or lymphocytic germinal centers), and 3) predominant sarcoid-like granulomas. Implant classification was associated with histological pattern of failure, and the macrophagic predominant pattern was more common in implants with metal-on-metal bearing surfaces (MoM HRA and MoM LHTHA groups). Duration of implantation and composition of periprosthetic cellular infiltrates was significantly different amongst the three implant types examined suggesting that histopathological features of ALTR may explain the variability of clinical implant performance in these cases.

Conclusions

ALTR encompasses a diverse range of histological patterns, which are reflective of both the implant configuration independent of manufacturer and clinical features such as duration of implantation. The macrophagic predominant pattern and its mechanism of implant failure represent an important subgroup of ALTR which could become more prominent with increased length of implantation.

Revision for taper corrosion at the neck-body junction following total hip arthroplasty: pearls and pitfalls

The management of the patient with a recalled, modular neck-body total hip arthroplasty can be complex, as it involves a combination of clinical, technical, and medicolegal challenges. Management begins with a thorough history and physical exam, radiographic evaluation, infection workup, and serum metal ion levels. Three-dimensional imaging is obtained based on patient symptomatology and metal ion levels and is used to evaluate for the presence of an adverse local tissue response as well as the integrity of the existing soft tissue envelope. The decision to perform revision surgery is based on a combination of patient symptomatology, laboratory values, and imaging findings. Revision surgery involves the entire armamentarium of femoral revision techniques, and the acetabulum may need to be revised at the surgeon's discretion. The femoral implant can often be removed without disrupting the femoral bone envelope; however, the surgeon should have a low threshold to perform an extended trochanteric osteotomy.

Quantification of material loss from the neck piece taper junctions of a bimodular primary hip prosthesis. A retrieval study from 27 failed Rejuvenate bimodular hip arthroplasties

The early failure and revision of bimodular primary total hip arthroplasty prostheses requires the identification of the risk factors for material loss and wear at the taper junctions through taper wear analysis. Deviations in taper geometries between revised and pristine modular neck tapers were determined using high resolution tactile measurements. A new algorithm was developed and validated to allow the quantitative analysis of material loss, complementing the standard visual inspection currently used. The algorithm was applied to a sample of 27 retrievals (in situ from 2.9 to 38.1 months) of the withdrawn Rejuvenate modular prosthesis. The mean wear volumes on the flat distal neck piece taper was 3.35 mm(3) (0.55 to 7.57), mainly occurring in a characteristic pattern in areas with high mechanical loading. Wear volume tended to increase with time to revision (r² = 0.423, p = 0.001). Implant and patient specific data (offset, stem size, patient's mass, age and body mass index) did not correlate with the amount of material loss observed (p > 0.078). Bilaterally revised implants showed higher amounts of combined total material loss and similar wear patterns on both sides. The consistent wear pattern found in this study has not been reported previously, suggesting that the device design and materials are associated with the failure of this prosthesis.

Quantification of the Contact Area at the Head-Stem Taper Interface of Modular Hip Prostheses

Corrosion of modular taper junctions of hip implants may be associated with clinical failure. Taper design parameters, as well as the intraoperatively applied assembly forces, have been proposed to affect corrosion. Fretting corrosion is related to relative interface shear motion and fluid ingress, which may vary with contact force and area. It was hypothesised in this study that assembly forces modify the extent and distribution of the surface contact area at the taper interface between a cobalt chrome head and titanium stem taper with a standard threaded surface profile. Local abrasion of a thin gold coating applied to the stem taper prior to assembly was used to determine the contact area after disassembly. Profilometry was then used to assess permanent deformation of the stem taper surface profile. With increasing assembly force (500 N, 2000 N, 4000 N and 8000 N) the number of stem taper surface profile ridges in contact with the head taper was found to increase (9.2±9.3%, 65.4±10.8%, 92.8±6.0% and 100%) and the overall taper area in contact was also found to increase (0.6±0.7%, 5.5±1.0%, 9.9±1.1% and 16.1±0.9%). Contact was inconsistently distributed over the length of the taper. An increase in plastic radial deformation of the surface ridges (-0.05±0.14 μm, 0.1±0.14 μm, 0.21±0.22 μm and 0.96±0.25 μm) was also observed with increasing assembly force. The limited contact of the taper surface ridges at lower assembly forces may influence corrosion rates, suggesting that the magnitude of the assembly force may affect clinical outcome. The method presented provides a simple and practical assessment of the contact area at the taper interface.

[Histopathological particle algorithm. Particle identification in the synovia and the SLIM]

BACKGROUND

In the histopathological diagnostics of synovitis and the synovium-like interface membrane (SLIM) the identification of crystals and crystal-like deposits and the associated inflammatory reactions play an important role. The multitude of endogenous crystals, the range of implant materials and material combinations, and the variability in the formation process of different particles explain the high morphological particle heterogeneity which complicates the diagnostic identification of diagnostic particles.

STUDY DESIGN AND METHODS

A simple histopathological particle algorithm has been designed which allows methodological particle identification based on (1) conventional transmitted light microscopy with a guide to particle size, shape and color, (2) optical polarization criteria and (3) enzyme histochemical properties (oil red staining and Prussian blue reaction). These methods, the importance for particle identification and the differential diagnostics from non-prosthetic materials are summarized in the so-called histopathological particle algorithm.

RESULTS

A total of 35 cases of synovitis and SLIM were analyzed and validated according to these criteria. Based on these criteria and a dichotomous differentiation the complete spectrum of particles in the SLIM and synovia can be defined histopathologically.

CONCLUSION

For histopathological diagnosis a particle score for synovitis and SLIM is recommended to evaluate (1) the predominant type of prothetic wear debris with differentiation between microparticles, and macroparticles, (2) the presence of non-prosthesis material particles and (3) the quantification of particle-association necrosis and lymphocytosis. An open, continuously updated web-based particle algorithm would be helpful to address the issue of particle heterogeneity and include all new particle materials generated in a rapidly changing field.

Gross trunnion failure after primary total hip arthroplasty

Unfavorable outcomes from trunnion fretting and corrosion damage have been reported in the literature, gross failures of tapers in primary total hip arthroplasties have been less frequently reported. We report on 5 patients, who presented with gross trunnion failures of modular metal-on-polyethylene or ceramic-on-polyethylene bearings from 5 implant manufacturers, all necessitating revision surgery. None of these patients had an antecedent history of trauma, and the majority presented with pain or instability. No common factor was identified that may be predictive of these type of failures. Since there were 5 different stem designs, this suggests that it may be a rare generic phenomenon occurring with multiple designs. Currently, further investigations are necessary, including retrieval analysis, to identify risk factors that may predispose to such failures.

Risk stratification algorithm for management of patients with dual modular taper total hip arthroplasty: consensus statement of the American Association of Hip and Knee Surgeons, the American Academy of Orthopaedic Surgeons and the Hip Society

Although 'dual taper' modular stems with interchangeable modular necks have the potential to optimize hip biomechanical parameters, there is increasing concern regarding the occurrence of adverse local tissue reactions from mechanically assisted crevice corrosion at the neck-stem taper junction. A systematic treatment approach (risk stratification algorithm) based on the currently available data is recommended to optimize patient management. While specialized tests such as metal ion analysis and MARS MRI are useful modalities in evaluating for adverse tissue reactions, over-reliance on any single investigative tool in the clinical decision-making process should be avoided. There should be a low threshold to perform a systematic evaluation of patients with dual taper stem total hip arthroplasty as early recognition and diagnosis will facilitate the initiation of appropriate treatment.

Adverse clinical outcomes in a primary modular neck/stem system

We report our experience with 215 recalled neck modular stems due to corrosion. Among the 195 hips with 2 years follow-up, 56% had no clinical symptoms, 26% had groin pain (typical of corrosion), and 17% had other symptoms. Cobalt levels were comparable between asymptomatic (3.4 μg/L, range 0.7-7.3 μg/L) and symptomatic patients (4.0 μg/L range 0-13.2 μg/L). Abnormal imaging findings were seen in 46% of symptomatic and 11% of asymptomatic hips (P=0.001). Twenty-six hips (13%) have either undergone revision surgery or have been scheduled. Evidence of corrosion was seen at revision surgery in all patients. Despite modest elevations in serum cobalt levels, abnormal imaging studies were seen in 36%, clinical symptoms were seen in 44%, and revision for corrosion was undertaken or scheduled in 13% of the hips.

Modular necks in primary hip arthroplasty without anatomical deformity: no clear benefit on restoration of hip geometry and dislocation rate. An exploratory study

Modular necks were introduced in total hip arthroplasty (THA) to improve restoration of hip-geometry and reduce dislocation-rates. This presumed advantage was evaluated retrospectively for patients with arthritis in otherwise anatomically normal hips. Restoration of hip-geometry was assessed on preoperative and postoperative calibrated radiographs in 95 consecutive primary THAs with a modular neck design and compared with 95 match controlled THAs with a similar monoblock stem. No significant differences were seen in restoration of body moment arm, leg length and cupangle. Offset restoration revealed a borderline significant difference (P = 0.48) with higher values for the monoblock stem. In both groups 4 dislocations within one year were encountered. In this study modular necks did not reveal a clear benefit in restoring hip geometry and dislocation rate after straightforward THA.

Potential release of in vivo trace metals from metallic medical implants in the human body: from ions to nanoparticles--a systematic analytical review

Metal ion release from metallic materials, e.g. metallic alloys and pure metals, implanted into the human body in dental and orthopedic surgery is becoming a major cause for concern. This review briefly provides an overview of both metallic alloys and pure metals used in implant materials in dental and orthopedic surgery. Additionally, a short section is dedicated to important biomaterials and their corrosive behavior in both real solutions and various types of media that model human biological fluids and tissues. The present review gives an overview of analytical methods, techniques and different approaches applied to the measurement of in vivo trace metals released into body fluids and tissues from patients carrying metal-on-metal prostheses and metal dental implants. Reference levels of ion concentrations in body fluids and tissues that have been determined by a host of studies are compiled, reviewed and presented in this paper. Finally, a collection of published clinical data on in vivo released trace metals from metallic medical implants is included.

Utility of modular implants in primary total hip arthroplasty

Most surgeons believe that some level of modularity has a valuable role to play in primary total hip arthroplasty. However, all modular junctions carry some risk and recent problems with taper tribocorrosion have elevated concerns. These problems suggest that more rigorous preclinical testing should be undertaken before new types of modularity are widely used. Efforts to further optimize these junctions where they are needed, avoidance of gratuitous use of modular junctions where they provide only modest benefits, and a judicious approach to adopting new modularity are reasonable approaches to current concerns.

Cross-sectional imaging in evaluation of soft tissue reactions secondary to metal debris

An integral component of systematic treatment algorithms to optimize evaluation and management of patients with MoM hip arthroplasty recommend the use of cross-sectional imaging to diagnose the presence of adverse local tissue reactions. Cross-sectional imaging studies such as ultrasound is a useful screening tool to detect the presence of a soft-tissue mass adjacent to a MoM implant. MARS MRI is a useful diagnostic test for assessing MoM hip arthroplasty and modular taper corrosion for adverse tissue reactions. Each cross-sectional imaging modality has unique utility and limitations. As metal artifact reduction technique continues to be refined, the utility of MARS MRI in evaluating patients with MoM hip arthroplasty and modular taper corrosion is likely to have an increased role in the clinical decision making process. However, over-reliance on any single investigative tool in the clinical decision-making process should be avoided.