Prevalence of pseudotumor in asymptomatic patients after metal-on-metal hip arthroplasty

Pseudotumor following total hip arthroplasty: experience of a tertiary referral center and proposal of the new "PCS" classification system

INTRODUCTION

This study summarizes outcomes in treating pseudotumors of the hip at a tertiary referral center and introduces a classification system to aid treatment decisions and enhance communication among providers.

MATERIALS AND METHODS

We collected data from 39 patients who underwent surgery for hip pseudotumor, analyzing implant failures based on patient history, revision reasons, bearing surface type, mass location and size, bone loss, revision type, and whether it was single- or two-stage. We introduce the PCS classification: 'P' for Pseudotumor (with 's' for symptomatic, 'e/I' for intra/extrapelvic location, and 'm' for high Chromium/Cobalt levels), 'C' for implant status, and 'S' for bone loss extent. In 37 patients, we evaluated Cohen's kappa coefficient to evaluate interobserver reliability.

RESULTS

Twenty (51.2%) patients were female, with a mean age of 71 years (range 36-89; σ 12.11); the mean follow-up duration was 54.43 months (range 12.2-128.3). The average size of the pseudotumor was 13.10 cm (range 3.3-37.2; σ 7.11) with 61.5% exhibiting extra-pelvic localization only. Bearing surfaces were MoM in 27 patients (69.2%). Single-stage revision surgery was performed in 87.1% of patients. There were 7 (17.9%) implant failures. No significant differences in failure rates were observed based on considered parameters. The agreement following Cohen's coefficient for the combined PCS classification was k = 0.43. Moderate to almost perfect agreement was obtained for parameter P and S, with k = 0.48 for parameter C.

CONCLUSION

No correlation was found between failures and analyzed characteristics. Our classification assesses clinical scenarios and stratifies surgical complexity for indication purposes. While interobserver agreement varies with parameter C, it is consistent with parameters P and S.

Correlation and diagnostic performance of metal ions in patients with pseudotumor after MoM hip arthroplasty: a systematic review and meta-analysis

BACKGROUND

The persistently rising complication, pseudotumor, after hip arthroplasty required surgeons' vigilance. Although the remaining controversial relationship between metal ions and pseudotumor, metal ion detection had been widely employed in clinic. The aim of this study is to evaluate the correlation between metal ions and pseudotumor, as well as the effectiveness of metal ion analysis in the screening and diagnosis of pseudotumor through systematic review and meta-analysis.

METHODS

The Medline and Embase databases were searched for studies evaluating metal ions and patients with pseudotumors after hip arthroplasty. A systematic review of risk ratio and diagnostic performance for metal ions was conducted.

RESULTS

Seven studies were included in the systematic review. The mean Methodological Index for Non-Randomized Studies (MINORS) score of the included studies was 19 (range, 14 to 22). Pooled risk ratio (RR) value was 2.01(95% CI: 1.25-3.24; P = 0.004) for cobalt ions level and 1.44 (95% CI: 1.10-1.88; P = 0.008) for chromium ions level. The pooled sensitivity, specificity and the area under the curve (AUC) for cobalt and chromium ions were determined to be 0.59, 0.82, 0.73 and 0.34, 0.82, 0.56, respectively.

CONCLUSIONS

The metal ions level has a low diagnostic value. It is of certain value for confirmation, but should not be used as a routine screening indicator. The diagnostic value of cobalt ions is higher than that of chromium.

LEVEL OF EVIDENCE

Diagnostic Level IV.

Possible Transformation of Pseudotumor to Synovial Sarcoma in a Failed Metal-on-Metal Total Hip Arthroplasty

Adverse local tissue reaction (ALTR) from the release of chromium and cobalt ions in metal-on-metal total hip arthroplasty (MoM THA) is a well-reported complication, but there is little evidence suggesting that this inflammatory reaction causes malignancy. We present a 69-year-old female with MoM THA who developed synovial sarcoma (SS). She underwent mass resection and revision THA. Postoperative pathologic analysis revealed the unanticipated diagnosis of SS. She subsequently underwent chemotherapy, sarcoma resection, and endoprosthetic reconstruction. We hypothesize that the SS developed from an ALTR in the setting of failed MoM THA. Given the paucity of data on possible malignant transformation of an ALTR to SS, we advise surgeons to consider potential malignancies when diagnosing ALTR in the setting of failed MoM THA bearings.

Clinical Outcomes and Risk Factors for Re-Revision Due to Trunnion Corrosion in Primary Metal-on-Polyethylene Total Hip Arthroplasty

BACKGROUND

There is a paucity of literature regarding the mid-term (greater than 2 years) outcomes of revision for adverse local tissue reaction to metal debris due to corrosion at the head-neck junction (trunnionosis) in metal-on-polyethylene total hip arthroplasty (THA), and risk factors for re-revision remain largely unknown. We aimed to report the re-revision-free survival and functional outcomes for this patient population and to identify risk factors for re-revision.

METHODS

A total of 80 hips (79 patients) with a metal-on-polyethylene THA who had undergone revision for trunnionosis at our institution were included. The mean study follow-up from index trunnionosis revision was 4.6 years (range, 2.0 to 9.4). Kaplan-Meier survival analysis was performed with all-cause re-revision as the end point, and multivariate logistic regression was used to identify risk factors for re-revision.

RESULTS

We saw that twenty-one hips (26%) underwent re-revision at a mean of 8.0 months (range, 0.03 to 36.3) after the index trunnionosis revision, most commonly for instability and infection. The two- and five-year all-cause re-revision-free survival rates were 75.0 and 73.2%, respectively. The mean Oxford Hip Score was 33.7 (range, 11 to 48); 76% were satisfied, and 24% were dissatisfied with their hip. Multivariate analysis identified not undergoing a cup revision (odds ratio: 4.5; 95% confidence interval: 1.03 to 19.7) and time from primary THA to the index trunnionosis revision (odds ratio: 0.77; 95% confidence interval: 0.62 to 0.97) as risk factors for undergoing re-revision.

CONCLUSIONS

The risk of early re-revision for these patients is high (26%), mostly due to infection and instability, and functional outcomes are fair. Not performing a cup revision appears to be a risk factor for re-revision, as is the shorter time from primary THA to trunnionosis revision.

LEVEL OF EVIDENCE

III.

Case report: Formation and recurrence of inflammatory pseudotumor after metal-on-metal hip arthroplasty

The metal-on-metal (MoM) artificial hip joint is a prosthesis used in early hip arthroplasty, particularly for hip resurfacing and total hip arthroplasty. However, abrasion and corrosion of MoM bearings result in the production of metal ions, such as cobalt and chromium, thereby inducing several complications such as inflammatory pseudotumor, aseptic inflammation, and allergy to metal ions (delayed type IV hypersensitivity). In this case report, we present a patient who was hospitalized for recurrence of a mass in the right inguinal area. In 2010, the patient underwent right MoM total hip arthroplasty for right femoral head necrosis and exhibited a good postoperative recovery. In 2019, the patient experienced pain in the right hip with activity limitation without any evident triggers, and a palpable mass was observed in the right inguinal area. A large periprosthetic mass was resected under general anesthesia, and the patient recovered well after the operation. Based on post-surgery imaging and pathological examinations, the mass was diagnosed as a periprosthetic inflammatory pseudotumor. In 2021, the inflammatory pseudotumor recurred at the same site. He then underwent right total hip revision surgery under epidural anesthesia and recovered well after surgery. No recurrence was noted at moderate follow-up. The incidence of inflammatory pseudotumors is high in MoM hip arthroplasty. Early revision is necessary in patients who meet the indications for revision, while regular postoperative follow-up is crucial.

Metal artifact reduction sequence-MRI abnormalities in asymptomatic patients with dual-mobility hip prostheses

Aims

Modular dual-mobility (DM) articulations are increasingly used during total hip arthroplasty (THA). However, concerns remain regarding the metal liner modularity. This study aims to correlate metal artifact reduction sequence (MARS)-MRI abnormalities with serum metal ion levels in patients with DM articulations.

Methods

A total of 45 patients (50 hips) with a modular DM articulation were included with mean follow-up of 3.7 years (SD 1.2). Enrolled patients with an asymptomatic, primary THA and DM articulation with over two years' follow-up underwent MARS-MRI. Each patient had serum cobalt, chromium, and titanium levels drawn. Patient satisfaction, Oxford Hip Score, and Forgotten Joint Score-12 (FJS-12) were collected. Each MARS-MRI was independently reviewed by fellowship-trained musculoskeletal radiologists blinded to serum ion levels.

Results

Overall, two patients (4.4%) had abnormal periprosthetic fluid collections on MARS-MRI with cobalt levels > 3.0 μg/l. Four patients (8.9%) had MARS-MRI findings consistent with greater trochanteric bursitis, all with cobalt levels < 1.0 μg/l. A seventh patient had a periprosthetic fluid collection with normal ion levels. Of the 38 patients without MARS-MRI abnormalities, 37 (97.4%) had cobalt levels < 1.0 μg/l, while one (2.6%) had a cobalt level of 1.4 μg/l. One patient (2.2%) had a chromium level > 3.0 μg/l and a periprosthetic fluid collection. Of the 41 patients with titanium levels, five (12.2%) had titanium levels > 5.0 μg/l without associated MARS-MRI abnormalities.

Conclusion

Periprosthetic fluid collections associated with elevated serum cobalt levels in patients with asymptomatic DM articulations occur infrequently (4.4%), but further assessment is necessary due to implant heterogeneity.

ACR Appropriateness Criteria® Imaging After Total Hip Arthroplasty

This article reviews evidence for performing various imaging studies in patients with total hip prostheses. Routine follow-up is generally performed with radiography. Radiographs are also usually the initial imaging modality for patients with symptoms related to the prosthesis. Following acute injury with pain, noncontrast CT may add information to radiographic examination regarding the presence and location of a fracture, component stability, and bone stock. Image-guided joint aspiration, noncontrast MRI, and white blood cell scan and sulfur colloid scan of the hip, are usually appropriate studies for patients suspected of having periprosthetic infection. For evaluation of component loosening, wear, and/or osteolysis, noncontrast CT or MRI are usually appropriate studies. Noncontrast MRI is usually appropriate for identifying adverse reaction to metal debris related to metal-on-metal articulations. For assessing patients after hip arthroplasty, who have trochanteric pain and nondiagnostic radiographs, ultrasound, or MRI are usually appropriate studies. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

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.

High Incidence of Mechanically Assisted Crevice Corrosion at 10 Years in Non-Cemented, Non-Recalled, Contemporary Total Hip Arthroplasties

BACKGROUND

One percent to 3% of contemporary non-cemented total hip arthroplasties (THAs) present with symptomatic mechanically assisted crevice corrosion (MACC). The incidence of this problem, however, as well as the rate of asymptomatic elevations in serum cobalt, is unknown.

METHODS

Cobalt and chromium levels were obtained in conjunction with radiographs at routine 10-year surveillance follow-up of THAs from a single manufacturer with a titanium stem, cobalt alloy femoral head, and cross-linked polyethylene countersurface.

RESULTS

Ten-year follow-up of patients with 162 consecutive THAs revealed that 17 patients with 18 hips had died of unrelated causes prior to metal ion testing. Two hips were revised for other reasons, and of the remaining 142 hips, 33 were in patients who were lost, leaving 109 hips (77% of those in alive patients and unrevised for other reasons and 67% of the entire cohort) for investigation. Sixty-three patients (58%) had a serum cobalt less than 1 ppb, and 35 (32%) a cobalt of ≥1 ppb, a cutoff consistent with MACC. Of the 32 hips with definite MACC, 15 of 32 (47%) patients were symptomatic, 16 of 30 (53%) patients had adverse local tissue reaction on magnetic resonance imaging, and 19 of 32 (59%) patients have undergone revision surgery for MACC to date.

CONCLUSION

At 10-year follow-up, a minimum of 22% (35/162) of hips had a cobalt level more than 1 ppb, consistent with MACC. Symptoms and adverse local tissue reactions are each present about one-half of the time, and 59% of those with documented MACC have undergone revision.

Critically high metal ion levels found in metal-on-metal modular hinged knee arthroplasty : a comparison of two different systems

AIMS

This study compared the cobalt and chromium serum ion concentration of patients treated with two different metal-on-metal (MoM) hinged total knee arthroplasty (TKA) systems, as well as a titanium nitride (TiN)-coated variant.

METHODS

A total of 63 patients (65 implants) were treated using either a MoM-coated (n = 29) or TiN-coated (n = 7) hinged TKA (GenuX mobile bearing, MUTARS; Implantcast, Germany) versus the BPKS (Brehm, Germany) hinged TKA (n = 27), in which the weight placed on the MoM hinge is diffused through a polyethylene (PE) inlay, reducing the direct load on the MoM hinge. Serum cobalt and chromium ion concentrations were assessed after minimum follow-up of 12 months, as well as functional outcome and quality of life.

RESULTS

No differences in mean age (69 years, 40 to 86), mean age adapted Charlson Comorbidity Index (3.1 (SD 1.4)), mean BMI (29.2 kg/m² (SD 5.8)), or number of other implants were observed between groups. Significant improvements in outcome scores and pain levels were achieved for all groups, and there was no difference in quality of life (12-Item Short-Form Health Survey questionnaire (SF-12)). Mean cobalt and chromium ion levels were significantly higher for the GenuX versus the BPKS hinged TKA (GenuX vs BPKS: cobalt: 16.3 vs 9.4 µg/l; chromium: 9.5 vs 5.2 µg/l). The TiN-coated implants did not appear to confer improvement in the metal ion levels. Metal ion concentrations above 7 µg/l were detected in 81%(29/36) of GenuX patients versus 41% (11/27) in the BPKS group. No GenuX patients had normal levels under 2 µg/l, versus 22% of BPKS patients. No significant reduction in outcome scores was observed regardless of the metal ion levels, whereas higher work-related activity was correlated with higher chromium concentrations.

CONCLUSION

Hinged TKA, using MoM hinges, resulted in critically high cobalt and chromium ion concentrations. The BPKS hinged TKA showed significantly lower metal ion concentrations compared with the GenuX TKA. No benefits were observed using TiN coating. The different weightbearing mechanics might influence the wear of the component materials. Higher workloads and physical activity could influence chromium levels. Cite this article: Bone Joint J 2022;104-B(3):376-385.

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.

Updates in postoperative imaging modalities following musculoskeletal surgery

Postoperative imaging following orthopaedic surgeries is essential in assessing complications post-surgery and also helps plan further treatment. Combining a high degree of clinical insight with appropriate imaging can guide the treating clinician to the correct diagnosis. Imaging is quite challenging because of surgery-related soft tissue changes, especially in the early postoperative period and the presence of metal implants resulting in image scatter and metal artifacts. Newer modalities and advances in imaging have helped overcome shortcomings and assess better, especially in procedures that involve implants. Collaborative decision-making involving radiologists and clinicians has shown to be beneficial and is the way forward. This narrative review discusses the utility of imaging in evaluating postoperative complications following musculoskeletal surgeries with specific relation to trauma, arthroplasty, and tumour by discussing commonly encountered clinical scenarios.

Comparison of Asymptomatic and Symptomatic Adverse Local Tissue Reaction in Patients With Head-Neck Taper Corrosion

BACKGROUND

Diagnosis of adverse local tissue reaction (ALTR) in metal-on-polyethylene (MoP) total hip arthroplasty (THA) secondary to head-neck taper corrosion is challenging. The purpose of this study is to compare differences between asymptomatic and symptomatic ALTR in an observational cohort, including presentation, metal ion differences, and metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) findings.

METHODS

We performed a retrospective review of an observational cohort of 492 MoP THA patients at increased risk of developing ALTR. Ninety-four patients underwent revision arthroplasty for ALTR. Patients were stratified into symptomatic and asymptomatic ALTR groups. Presentation, metal ion levels, and imaging findings were compared.

RESULTS

For patients with confirmed ALTR, 41% were asymptomatic. There was a statistically significant difference in the serum chromium levels between symptomatic and asymptomatic ALTR patients (2.2 μg/L vs 3.1 μg/L, P = .05). There was no statistically significant difference between the serum cobalt levels or MRI findings in these 2 groups. We observed that extracapsular disease associated with ALTR could be misinterpreted as trochanteric bursitis.

CONCLUSION

Almost half of the MoP THA ALTR cases identified were asymptomatic. Cobalt levels could not differentiate between symptomatic and asymptomatic pseudotumor formation. Symptomatic and asymptomatic MoP ALTRs have similar MARS MRI characteristics. Our findings suggest that it is essential to risk stratify patients who could potentially have ALTR based on implant type, symptoms, ion levels, and MARS MRI.

Complications, Reoperations, and Mid-Term Outcomes Following Anterior Vertebral Body Tethering Versus Posterior Spinal Fusion: A Meta-Analysis

Background

Anterior vertebral body tethering (AVBT) is a growth-modulation technique theorized to correct adolescent idiopathic scoliosis (AIS) without the postoperative stiffness imposed by posterior spinal fusion. However, data are limited to small series examining short-term outcomes. To assess AVBT's potential as a viable alternative to posterior spinal fusion (PSF), a comprehensive comparison is warranted. The purpose of this meta-analysis was to compare postoperative outcomes between patients with AIS undergoing PSF and AVBT. Our primary objective was to compare complication and reoperation rates at available follow-up times. Secondary objectives included comparing mid-term Scoliosis Research Society (SRS)-22 scores, and coronal and sagittal-plane Cobb angle corrections.

Methods

We performed a systematic review of outcome studies following AVBT and/or PSF procedures. The inclusion criteria included the following: AVBT and/or PSF procedures; Lenke 1 or 2 curves; an age of 10 to 18 years for >90% of the patient population; <10% non-AIS scoliosis etiology; and follow-up of ≥1 year. A single-arm, random-effects meta-analysis was performed. Deformity corrections, complication and reoperation rates, and postoperative SRS-22 scores were recorded.

Results

Ten AVBT studies (211 patients) and 14 PSF studies (1,069 patients) were included. The mean follow-up durations were similar for both groups. Pooled complication rates were 26% for AVBT versus 2% for PSF, and reoperation rates were 14.1% for AVBT versus 0.6% for PSF with nonoverlapping confidence intervals (CIs). The pooled reoperation rate among studies with follow-up times of ≥36 months was 24.7% in AVBT versus 1.8% in PSF. Deformity correction, clinical outcomes, and mid-term SRS-22 scores were similar.

Conclusions

Our study showed greater rates of complications and reoperations with AVBT compared with PSF. Reoperation rates were significantly greater in AVBT studies with longer follow-up (≥36 months). Deformity correction, clinical outcomes, and mid-term SRS-22 scores were similar. While a potential fusionless treatment for AIS merits excitement, clinicians should consider AVBT with caution. Future long-term randomized prospective studies are needed.

Level of Evidence

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

Distinct Concentration-Dependent Molecular Pathways Regulate Bone Cell Responses to Cobalt and Chromium Exposure from Joint Replacement Prostheses

Systemic cobalt (Co) and chromium (Cr) concentrations may be elevated in patients with metal joint replacement prostheses. Several studies have highlighted the detrimental effects of this exposure on bone cells in vitro, but the underlying mechanisms remain unclear. In this study, we use whole-genome microarrays to comprehensively assess gene expression in primary human osteoblasts, osteoclast precursors and mature resorbing osteoclasts following exposure to clinically relevant circulating versus local periprosthetic tissue concentrations of Co²⁺ and Cr³⁺ ions and CoCr nanoparticles. We also describe the gene expression response in osteoblasts on routinely used prosthesis surfaces in the presence of metal exposure. Our results suggest that systemic levels of metal exposure have no effect on osteoblasts, and primarily inhibit osteoclast differentiation and function via altering the focal adhesion and extracellular matrix interaction pathways. In contrast, periprosthetic levels of metal exposure inhibit both osteoblast and osteoclast activity by altering HIF-1α signaling and endocytic/cytoskeletal genes respectively, as well as increasing inflammatory signaling with mechanistic implications for adverse reactions to metal debris. Furthermore, we identify gene clusters and KEGG pathways for which the expression correlates with increasing Co²⁺:Cr³⁺ concentrations, and has the potential to serve as early markers of metal toxicity. Finally, our study provides a molecular basis for the improved clinical outcomes for hydroxyapatite-coated prostheses that elicit a pro-survival osteogenic gene signature compared to grit-blasted and plasma-sprayed titanium-coated surfaces in the presence of metal exposure.

Fatal vascular complication due to metallosis

Metallosis is a well-known complication at the site of total hip and knee arthroplasty. Vascular involvement of this complication is rare and generally results from vascular compression by a mass or pseudotumor. In the present report, we have described a case of lower limb acute arterial ischemia due to arterial injury as a complication of metallosis with a fatal outcome.

Incidence of Pseudotumors in a Dual Modular Stem Construct With and Without Metal-on-Metal Bearing Surface

BACKGROUND

The purpose of this study was to compare the incidence of pseudotumors in metal-on-metal (MoM) titanium modular neck hip arthroplasties to non-MoM modular neck hip arthroplasties. A secondary goal was to determine whether a correlation exists between elevated metal concentrations and pseudotumor incidence.

METHODS

The data were collected and evaluated from 49 MoM joints and 26 non-MoM joints between the years 2012 and 2017. Hip ultrasonography was done after a minimum of 5 years postimplantation. Whole serum metal (titanium, cobalt, and chromium) concentrations were measured at the hip ultrasonography study.

RESULTS

The average time elapsed between surgery and ultrasonography visit was 7.6 years. In the 49 patients with MoM joints, 22.4% (n = 11) had a pseudotumor. In the 26 patients with non-MoM joints, 9.1% of metal-on-polyethylene hips (n = 1) and 0% of ceramic-on-ceramic/polyethylene hips developed a pseudotumor. No significant statistical correlation was observed between serum metal concentrations and pseudotumor formation (P > 0.05). A significant correlation was observed of serum titanium concentration to pseudotumor size (P = 0.024).

CONCLUSION

The incidence of pseudotumor formation in MoM total hip arthroplasties was more than five times the incidence associated with non-MoM bearings. The correlation between serum titanium concentration and pseudotumor size suggests that titanium levels may be a useful indicator for pseudotumor formation in patients with this particular titanium modular neck femoral implant. No notable correlation was observed between serum cobalt and chromium concentration and pseudotumor formation or size.

The Calpain Gene is Correlated With Metal-on-Metal Hip Replacement Failures

BACKGROUND

Metal-on-metal (MOM) total hip arthroplasty is associated with unacceptable failure rates secondary to metal ion reactions. Efforts to identify which patients will go on to failure have been limited; recently, there has been a suggestion for a potential genetic basis for the increased risk of revision in MOM hip replacements (MOMHRs). The purpose of this study is to determine whether certain immunologic genotypes are predictive of the need for revision in patients with MOM total hip implants.

METHODS

This is a case-control study of all patients undergoing primary MOMHR between September 2002 and January 2012 with a minimum of 5-year follow-up. Our investigational "case" cohort was comprised of patients who underwent revision for MOMHR for a reason other than infection. A single-nucleotide polymorphism (SNP) array analysis was performed to identify a potential genetic basis for failure.

RESULTS

Thirty-two patients (15 case and 17 control) were included in our analysis. All patients in the revision group had a chief complain of pain; revision patients were more likely to have a posterior approach (P = .01) and larger head size (P = .04) than nonrevision patients. No patient or implant characteristics were independently associated with revision in a multivariate analysis. Patients with SNP kgp9316441 were identified as having an increased odds of revision for MOM failure (P < .001).

CONCLUSION

This study identified an SNP, kgp9316441, encoding proteins associated with inflammation and macrophage activation. This SNP was associated with significantly increased odds of revision for MOMHR. Future studies are warranted to validate this gene target both in vitro and in vivo.

LEVEL OF EVIDENCE

III.

Metal Ion Release after Hip and Knee Arthroplasty - Causes, Biological Effects and Diagnostics

All metal implants in human bodies corrode which results in metal ions release. This is not necessarily a problem and represents for most patients no hazard. However, if a critical metal ion concentration is exceeded, local or rarely systemic problems can occur. This article summarizes the mechanisms of metal ion release and its clinical consequences. Several situations can result in increased metal ion release: metal-on-metal hip arthroplasties with increased wear, increased micromotion at taper interfaces, direct metal-metal contact (polyethylene wear, impingement), erroneously used metal heads after ceramic head fracture. Possible problems are in most cases located close to the concerned joint. Furthermore, there are reports about toxic damage to several organs. Most of these reports refer to erroneously used metal heads in revisions after a broken ceramic head. There is currently no evidence of carcinogenic or teratogenic effects of implants but data is not sufficient to exclude possible effects. Cobalt and chromium blood levels (favorably in whole blood) should be measured in patients with suspected elevated metal ions. According to current knowledge levels below 2 µg/l seem to be uncritical, levels between 2 and 7 µg/l are considered borderline with unknown biological consequences and levels above 7 µg/l indicate a local problem which should be further diagnosed. Metal ion levels always need to be interpreted together with clinical symptoms and imaging results.

Metal-on-metal total hip arthroplasty adverse local tissue reaction with intermittent unilateral vascular claudication

Osteolysis and adverse local soft-tissue reactions are well-documented complications of metal-on-metal prosthetic implants. This case report describes a 68-year-old man who presented to the clinic 10 years after staged bilateral metal-on-metal total hip arthroplasty revisions with the primary complaint of groin pain, intermittent right leg pain, swelling, and muscle cramping while ambulating that resolved with rest. A complete workup was negative for deep venous thrombosis and infection. His symptoms were found to be secondary to an iliopsoas bursal mass externally compressing the femoral vasculature resulting in vascular claudication. He was treated with revision arthroplasty and drainage of the fluid within the iliopsoas bursal effusion with symptomatic resolution.

The Outcome of Revision Surgery for Failed Metal-on-Metal Total Hip Arthroplasty

BACKGROUND

Metal-on-metal total hip arthroplasties (MoM THAs) are frequently revised, though there is a paucity of functional outcome data. We report on outcomes and prognostic factors predictive of outcome from the largest series of MoM THA revisions to date.

METHODS

A single-center consecutive series of revisions from MoM THAs was identified. The cohort was divided by the presence or absence of symptoms prior to revision. The primary outcome was functional outcome (Oxford Hip Score [OHS]). Secondary outcomes were complication data, pre-revision and post-revision blood metal ions, and modified Oxford classification of pre-revision magnetic resonance imaging.

RESULTS

One hundred eighty revisions at median follow-up of 5.48 years were identified. Median OHS improved from 29 to 37 with revision (P < .001). Symptomatic patients experienced the greatest functional benefit (ΔOHS 6.5 vs 1.4, P = .012), while the function of asymptomatic patients was unaffected by revision (P = .4). Use of a cobalt-chromium-containing bearing surface at revision and increased body mass index were predictive of poor functional outcome.

CONCLUSION

Symptomatic patients experience greater functional benefit from revision surgery but do not regain the same level of function as patients who were asymptomatic prior to revision. Body mass index and use of cobalt-chromium-containing bearing surfaces are prognostic for poor functional outcome.

Mechanisms of Adverse Local Tissue Reactions to Hip Implants

Adverse Local Tissue Reactions (ALTRs) are one of the main causes of hip implant failures. Although the metal release from the implants is considered as a main etiology, the mechanisms, and the roles of the released products are topics of ongoing research. The alloys used in the hip implants are considered biocompatible and show negligible corrosion in the body environment under static conditions. However, modularity and its associated mechanically assisted corrosion have been shown to release metal species into the body fluids. ALTRs associated with metal release have been observed in hip implants with metal-on-metal articulation initially, and later with metal-on-polyethylene articulation, the most commonly used design in current hip replacement. The etiological factors in ALTRs have been the topics of many studies. One commonly accepted theory is that the interactions between the metal species and body proteins and cells generate a delayed type IV hypersensitivity reaction leading to ALTRs. However, lymphocyte reactions are not always observed in ALTRS, and the molecular mechanisms have not been clearly demonstrated. A more accepted mechanism is that cell damage generated by metal ions may trigger the secretion of cytokines leading to the inflammatory reactions observed in ALTRs. In this inflammatory environment, some patients would develop hypersensitivity that is associated with poor outcomes. Concerns over ALTRS have brought significant impact to both the clinical selection and development of hip implants. This review is focused on the mechanisms of ALTRs, specifically, the metal release process and the roles of the metal species released in the etiology and pathogenesis of the disease. Hopefully, our presentation and discussion of this biological process from a material perspective could improve our current understanding on the ALTRs and provide useful guidance in developing preventive solutions.

Severe Wear and multiple Pseudotumor formation due to revision for ceramic head breakage after ceramic-on-ceramic Total hip arthroplasty: a case report

Background

Head breakage is a serious complication following total hip arthroplasty when using Ceramic on Ceramic bearings surfaces. There is still in controversy about the selection of bearing surfaces when conducting revision surgery.

Case presentation

We describe the case of a fifty-year-old man who had undergone right total hip arthroplasty (THA) with ceramic-on-ceramic prostheses in 2011. After a fall 6 years after the primary procedures, radiographs suggested a ceramic head breakage for revision THA with exchange of metal-on-polyethylene bearing. However, 8 months later, severe metallosis and multiple pseudotumor was confirmed in pelvis and surrounding hip after re-revision THA with ceramic-on-polyethylene prostheses. Analysis of the serum metal ion indicated massive wear of the metal head and erosion of the stem neck and taper.

Conclusions

This case vividly demonstrates metal bearings should be avoided and revision with complete synovectomy and thorough debridement should be performed whenever possible for a fractured ceramic bearing.

Host-specific factors affect the pathogenesis of adverse reaction to metal debris

Background

Adverse Reaction to Metal Debris (ARMD) is a major reason for revision surgeries in patients with metal-on-metal (MoM) hip replacements. Most failures are related to excessively wearing implant producing harmful metal debris (extrinsic factor). As ARMD may also occur in patients with low-wearing implants, it has been suggested that there are differences in host-specific intrinsic factors contributing to the development of ARMD. However, there are no studies that have directly assessed whether the development of ARMD is actually affected by these intrinsic factors.

Methods

We included all 29 patients (out of 33 patients) with sufficient data who had undergone bilateral revision of ASR MoM hips (58 hips) at our institution. Samples of the inflamed synovia and/or pseudotumour were obtained perioperatively and sent to histopathological analysis. Total wear volumes of the implants were assessed. Patients underwent MARS-MRI imaging of the hips preoperatively. Histological findings, imaging findings and total wear volumes between the hips of each patient were compared.

Results

The difference in wear volume between the hips was clinically and statistically significant (median difference 15.35 mm³, range 1 to 39 mm³, IQR 6 to 23 mm³) (p < 0.001). The median ratio of total wear volume between the hips was 2.0 (range 1.09 to 10.0, IQR 1.67 to 3.72). In majority of the histological features and in presence of pseudotumour, there were no differences between the left and right hip of each patient (p > 0.05 for all comparisons). These features included macrophage sheet thickness, perivascular lymphocyte cuff thickness, presence of plasma cells, presence of diffuse lymphocytic infiltration and presence of germinal centers.

Conclusions

Despite the significantly differing amounts of wear (extrinsic factor) seen between the sides, majority of the histological findings were similar in both hips and the presence of pseudotumour was symmetrical in most hips. As a direct consequence, it follows that there must be intrinsic factors which contribute to the symmetry of the findings, ie. the pathogenesis of ARMD, on individual level. This has been hypothesized in the literature but no studies have been conducted to confirm the hypothesis. Further, as the threshold of metal debris needed to develop ARMD appears to be largely variable based on the previous literature, it is likely that there are between-patient differences in these intrinsic factors, ie. the host response to metal debris is individual.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2578-0) contains supplementary material, which is available to authorized users.

Prevalence and natural course of pseudotumours after small-head metal-on-metal total hip arthroplasty: a minimum 18-year follow-up study of a previous report

AIMS

The present study investigated the five-year interval changes in pseudotumours and measured serum metal ions at long-term follow-up of a previous report of 28 mm diameter metal-on-metal (MoM) total hip arthroplasty (THA).

PATIENTS AND METHODS

A total of 72 patients (mean age 46.6 years (37 to 55); 43 men, 29 women; 91 hips) who underwent cementless primary MoM THA with a 28 mm modular head were included. The mean follow-up duration was 20.3 years (18 to 24). All patients had CT scans at a mean 15.1 years (13 to 19) after the index operation and subsequent follow-up at a mean of 20.2 years (18 to 24). Pseudotumour volume, type of mass, and new-onset pseudotumours were evaluated using CT scanning. Clinical outcomes were assessed by Harris Hip Score (HHS) and the presence of groin pain. Serum metal ion (cobalt (Co) and chromium (Cr)) levels were measured at the latest follow-up.

RESULTS

At final follow-up, pseudotumours were observed in 26/91 hips (28.6%). There was an increase in volume of the pseudotumour in four hips (15.4%), no change in volume in 21 hips (80.8%), and a decrease in volume in one hip (3.8%). There were no new-onset pseudotumours. There was no significant difference in HHS between patients with and without pseudotumours. At final follow-up, mean serum Co ion levels and median Co:Cr ratios were significantly greater in patients with pseudotumours, but the serum Cr ion levels were not significantly different.

CONCLUSION

At a mean 20 years of follow-up, pseudotumours were observed in 26/91 hips (28.6%) with no new-onset pseudotumours during subsequent follow-up. Most pseudotumours in small-head MoM THA were static in volume and asymptomatic with normal serum metal ion levels. Cite this article: Bone Joint J 2019;101-B:317-324.

Trends in total hip arthroplasty

This article discusses developments in total hip arthroplasty related to the use of highly cross-linked polyethylene (HXLPE) liner material as the new standard of care for acetabular cup articulation surfaces. The pathologic implications of metal-on-metal hip prostheses in asymptomatic patients also are discussed.

Adverse reaction to metal debris after small-head diameter metal-on-metal total hip arthroplasty: an increasing concern

INTRODUCTION:

Failures due to adverse reaction to metal debris (ARMD) have become an area of common focus among surgeons performing hip replacements. Several authors have reported data on the prevalence of these masses, in both symptomatic and asymptomatic patients after either large-diameter head metal-on-metal (MoM) total hip arthroplasty (THA) or hip resurfacing arthroplasty, with a large variability of rate. To our knowledge, few data are reported on the association of this lesion with the use of small-head diameter MoM.

METHODS:

15 hips that were revised for ARMD in small-head MoM THA were included in this study. We focused our attention on the difficulties of diagnosis and treatment and also on the histologic aspects of the harvested pathologic tissue.

RESULTS:

The histological examination of our cases showed a presence of lymphocytic infiltrate suggesting a delayed hypersensitivity reaction to the metal of type IV (ALVAL), but different from each other in term of the prevalence of the cellular component. Osteolysis and severe soft tissue damage were also observed. Revision resulted in remission of the lesion and successful implant.

CONCLUSIONS:

Our observation suggests that the evidence of ARMD should be considered even in case of small-head MoM arthroplasty and therefore these patients should be followed scrupulously with 2nd level diagnostic tools such as magnetic resonance imaging with metal artifact reduction sequence (MARS-MRI) and metal ion levels at least once. Further investigations are necessary to establish the real prevalence of this phenomenon in the whole population of small-head MoM THAs.

Metal ion trend in patients with metal-on-metal total hip arthroplasty: a 10-year prospective study

INTRODUCTION:

There have been reported adverse reactions in patients with large head metal-on-metal hip arthroplasty, therefore metal particle debris are a cause for concern. The aim of this study was to evaluate the release trend of metal ions and the correlated variables.

METHODS:

54 patients were prospectively enrolled into the study from 2004 to 2006. All patients had 36-mm metal head, Pinnacle acetabular component, Summit stem and Ultamet CoCr alloy liner (Depuy Inc.), and underwent clinical and radiological management. The haematic concentration of Cr-Co at 0, 6, 12, 24, 60 and 120 months after the implantation was analysed in a sub-cohort of 34 patients.

RESULTS:

10-year revision rate for each case was 8.9%. The average concentration of Co at 120 months was 3.12 μg/L (median 2.20) with 53% values >2 μg/L and 1 >7 μg/L. After 6 months the median levels of Cr and Co were higher than time 0 ( p < 0.0001); no significant differences were found between 6 and 24 months; while Co had significant increase between 60 and 120 months ( p = 0.002). Overweight, University of California at Los Angeles (UCLA) >9 and <50 years old patients have significantly higher circulating metal ions.

DISCUSSION:

This is 1 of the few prospective studies on the argument. The revision rate is conforming to records. Our data shows ionic concentration is not predictive of revision or adverse reaction to metals. We described a 3-phase trend for Co probably due to the loss of integrity of the surfaces.

Pleomorphic clinical spectrum of metallosis in total hip arthroplasty

PURPOSE

To summarize the biological effects of metal debris from hip arthroplasties which characterize a polymorphic clinical spectrum of local and remote manifestation.

METHODS

Retrospective study. Patient, implant, and surgical characteristics were collected, including implant survival, clinical manifestations, cause of arthroplasty revision or implant failure, and peri- and intra-operative complications. The primary endpoint was implant survivorship. Hip revision arthroplasty was decided considering clinical signs and symptoms, abnormal imaging (XR, MR, TC, echotomography, scintigraphy), and blood metal ion level. An ad hoc electronic form was used to collect demographic, epidemiological, and clinical variables. In-between group comparisons of quantitative variables were performed with the Student t test and the Mann-Whitney for parametric and non-parametric variables, respectively. Logistic regression analyses were carried out to assess the relationship between clinical and radiographic characteristics and stem and cup revision. Radiographic measurements of implant positioning validity and reliability were assessed using Krippendorff's alpha reliability coefficient. The statistical software STATA version 15 (StatsCorp, TX) was used to perform statistical computations.

RESULTS

In this MoM THA series, the most incident cause of implant failure was ARMD in 11 out of 14 (78.6%) patients. All clinical failure manifestations, revision surgery highlights, and intra-operative findings are reported.

CONCLUSIONS

The local adverse reactions include lesions of different clinical relevance from small asymptomatic soft tissue lesions to dramatic osteolysis, necrosis, effusion, and growing masses which can cause secondary pathological effects. Symptoms of systemic toxicity are rarely described but may have been largely unreported in literature. Despite the extensive literature on the topic, the patient's management is still uncertain and challenging. Every metallic implant (e.g., screws, plates, spinal instrumentations) has a potential local or systemic adverse effect. Organizing a national registry of arthroplasty should be mandatory, in order to collect data about the patients, the surgery, the implanted device (with a careful post-marketing tracking), and the follow-up for all the procedures performed at a national level. The data collected in the registry will allow to analyze the implant survival and to better recognize the undesirable and sometimes unexpected effects of different biomaterials on the whole body.

A case of bone necrosis with pseudotumor following metal-on-metal total hip arthroplasty

A case of bone necrosis with a pseudotumor following metal-on-metal total hip arthroplasty is presented. The patient showed no abnormal magnetic resonance findings 2 years postoperatively, but serum metal ion levels were elevated. The patient developed hip pain 3.5 years postoperatively, and bone necrosis with a pseudotumor was found. The present patient emphasized the fact that tissue necrosis associated with failed metal-on-metal bearing hip might not be limited to soft tissues, but bone necrosis could occur.

Indications for MARS-MRI in Patients Treated With Articular Surface Replacement XL Total Hip Arthroplasty

BACKGROUND

The purpose of this study was to identify which patient and clinical factors are predictive of adverse local tissue reaction (ALTR) and to use these factors to create a highly sensitive algorithm for indicating metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) in Articular Surface Replacement (ASR) XL total hip arthroplasty patients. Our secondary aim was to compare our algorithm to existing national guidelines on when to take MARS-MRI in metal-on-metal total hip arthroplasty patients.

METHODS

The study consisted of 137 patients treated with unilateral ASR XL implants from a prospective, multicenter study. Patients underwent MARS-MRI regardless of clinical presentation at a mean of 6.2 (range, 3.3-10.4) years from surgery. Univariate and multivariate analyses were conducted to determine which variables were predictive of ALTR. Predictors were used to create an algorithm to indicate MARS-MRI. Finally, we compared our algorithm's ability to detect ALTR to existing guidelines.

RESULTS

We found a visual analog scale pain score ≥2 (odds ratio [OR] = 2.53; P = .023), high blood cobalt (OR = 1.05; P = .023), and male gender (OR = 2.37; P = .034) to be significant predictors of ALTR presence in our cohort. The resultant algorithm achieved 86.4% sensitivity and 60.2% specificity in detecting ALTR within our cohort. Our algorithm had the highest area under the curve and was the only guideline that was significantly predictive of ALTR (P = .014).

CONCLUSION

Our algorithm including patient-reported pain and sex-specific cutoffs for blood cobalt levels could predict ALTR and indicate MARS-MRI in our cohort of ASR XL metal-on-metal patients with high sensitivity.

LEVEL OF EVIDENCE

Level II, diagnostic study.

Long-Term Outcomes After Metal-on-Metal Total Hip Arthroplasty With a 28-mm Head: A 17- to 23-Year Follow-Up Study of a Previous Report

BACKGROUND

Second-generation, metal-on-metal total hip arthroplasty (MoM THA) using a 28-mm head has shown favorable results compared with large head MoM THA. The purpose of this study is to evaluate the long-term outcomes of cementless primary MoM THA with a 28-mm head and the incidence of osteolysis using computed tomography.

METHODS

A total of 92 patients (53 men and 39 women) who underwent primary cementless MoM THA (114 hips) with a 28-mm head were enrolled in this study. Their mean age was 46.2 years at the time of surgery. The mean follow-up duration was 20 years. The Harris hip score, presence of thigh or groin pain, radiographic results, presence of peri-implant osteolysis, histologic analysis, and Kaplan-Meier survival curves were evaluated.

RESULTS

The mean preoperative Harris hip score of 50.5 improved to 85.1 at the final follow-up. Eight patients (8 hips) experienced groin pain, but none had thigh pain. Twelve revisions (6.2%) were performed including 10 hips for aseptic loosening with osteolysis and 2 hips for periprosthetic fracture around the stem. At 23 years, 91% of patients were free from revision of the acetabular component due to aseptic loosening and 90.1% were free from revision of both femoral and acetabular components due to any reason. Osteolysis was identified around the cup in 12 cases (10.5%) and around the stem in 7 cases (6.1%).

CONCLUSION

MoM THA with a 28-mm head showed a relatively low rate of aseptic implant loosening at a mean follow-up of 20 years.

Femoral offset found not to affect metal ion levels in metal-on-metal total hip arthroplasty

BACKGROUND

Failure to restore femoral offset in metal on polyethylene total hip arthroplasty (THA) causes polyethylene wear and aseptic loosening. To our knowledge, no study to date has investigated the relationship between femoral offset and wear in metal-on-metal (MOM) THA.

AIMS

In this study, we investigated the relationship between femoral offset and wear by measuring circulating metal ion levels in MOM THA.

METHODS

In this retrospective study, we identified patients who had undergone MOM THA with the ASR XL system (DePuy International Ltd., Leeds, UK). Femoral offset was measured using anteroposterior radiographs, and circulating metal ion levels (cobalt and chromium) were recorded.

RESULTS

In total, 95 patients were included (68 males and 27 females). The mean age at the time of surgery was 64.9. Mean time from surgery to blood sampling was 15.4 months. No statistically significant relationship was found between femoral offset and cobalt (p = 0.313) or chromium (p = 0.401) ions.

CONCLUSION

It is known that failure to restore femoral offset during THA can lead to high rates of wear in metal-on-polyethylene articulations. In our study, no statistically significant relationship was found between femoral offset and serum cobalt or chromium ions. This study adds to the information available to surgeons regarding factors that increase wear in metal-on-metal total hip arthroplasty.

[Mid-term effectiveness of large-head metal-on-metal total hip arthroplasty]

Objective

To explore the mid-term effectiveness of large-head metal-on-metal total hip arthroplasty (THA).

Methods

A retrospective analysis was made on the clinical date of 40 patients (43 hips) who were treated with the large-head metal-on-metal THA between April 2009 and June 2010. There were 18 males (20 hips) and 22 females (23 hips) with an average age of 55.1 years (range, 20-85 years). Unilateral hip was involved in 37 cases and bilateral hips in 3 cases. The disease causes included osteonecrosis of the femoral head in 14 cases (15 hips), osteoarthritis in 6 cases (7 hips), rheumatoid arthritis in 4 cases (4 hips), femoral neck fracture in 4 cases (4 hips), and developmental dysplasia of the hip in 12 cases (13 hips). Before operation, the Harris score and University of California Los Angeles (UCLA) score were 38.51±5.62 and 4.21±1.43, respectively. The visual analogue scale (VAS) score was 6.78±0.95.

Results

All patients were followed up 6.7-8.3 years (mean 7.5 years). All incisions healed primarily and no neurovascular injury, infection, and hip dislocation occurred. At last follow-up, the Harris score and UCLA score were 93.33±3.21 and 7.32±1.45, respectively, showing significant differences when compared with preoperative scores ( t=51.753, P=0.000; t=23.232, P=0.000). The thigh pain occurred in 3 cases (3 hips) in whom the inflammatory pseudotumor of soft tissues was found in 1 case (1 hip). Postoperative X-ray films showed that the acetabular abduction angle and anteversion angle were (46.5±3.2)° and (14.8±3.6) °, respectively. The initial stability of femoral stem prosthesis was excellent in 39 hips and good in 4 hips according to Mulliken standard. Osteolysis occurred in 2 hips and revision was performed in 1 hip of secondary loosening of prosthesis. The rest patients had no prosthesis loosening or sinking.

Conclusion

The mid-term effectiveness of large-head mental-on-mental THA in treatment of the terminal diseases of hips are good.

Systemic and local toxicity of metal debris released from hip prostheses: A review of experimental approaches

Despite the technological improvements in orthopedic joint replacement implants, wear and corrosion products associated with the metal components of these implants may result in adverse local tissue and perhaps systemic reactions and toxicities. The current review encompasses a literature review of the local and systemic toxicity studies concerning the effect of CoCrMo wear debris released from wear and corrosion of orthopedic implants and prostheses. Release of metallic debris is mainly in the form of micro- and nano-particles, ions of different valences, and oxides composed of Co and Cr. Though these substances alter human biology, their direct effects of these substances on specific tissue types remain poorly understood. This may partially be the consequence of the multivariate research methodologies employed, leading to inconsistent reports. This review proposes the importance of developing new and more appropriate in-vitro methodologies to study the cellular responses and toxicity mediated by joint replacement wear debris in-vivo.

Wear testing of a canine hip resurfacing implant that uses highly cross-linked polyethylene

Hip resurfacing offers advantages for young, active patients afflicted with hip osteoarthritis and may also be a beneficial treatment for adult canines. Conventional hip resurfacing uses metal-on-metal bearings to preserve bone stock, but it may be feasible to use metal-on-polyethylene bearings to reduce metal wear debris while still preserving bone. This study characterized the short-term wear behavior of a novel hip resurfacing implant for canines that uses a 1.5 mm thick liner of highly cross-linked polyethylene in the acetabular component. This implant was tested in an orbital bearing machine that simulated canine gait for 1.1 million cycles. Wear of the liner was evaluated using gravimetric analysis and by measuring wear depth with an optical scanner. The liners had a steady-state mass wear rate of 0.99 ± 0.17 mg per million cycles and an average wear depth in the central liner region of 0.028 mm. No liners, shells, or femoral heads had any catastrophic failure due to yielding or fracture. These results suggest that the thin liners will not prematurely crack after implantation in canines. This is the first hip resurfacing device developed for canines, and this study is the first to characterize the in vitro wear of highly cross-linked polyethylene liners in a hip resurfacing implant. The canine implant developed in this study may be an attractive treatment option for canines afflicted with hip osteoarthritis, and since canines are the preferred animal model for human hip replacement, this implant can support the development of metal-on-polyethylene hip resurfacing technology for human patients. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1196-1205, 2018.

Frank Stinchfield Award: Identification of the At-risk Genotype for Development of Pseudotumors Around Metal-on-metal THAs

BACKGROUND

Once touted as the future of hip arthroplasty, metal-on-metal (MoM) bearing surfaces have fallen sharply from favor with the emergence of a strong body of evidence demonstrating unacceptably high premature implant failure rates. The previously unpredictable development of adverse local tissue reactions (ALTRs) has been a substantive contributor to this. Although the underlying pathophysiology of these so-called "pseudotumors" is now well understood, the fundamental predisposing patient risk factors have remained elusive.

QUESTIONS/PURPOSES

The aim of this research, as a clinical-genotype correlation analysis, was to identify specific alleles (genes) associated with the development of ALTRs in patients with in situ MoM THAs.

METHODS

A case-control study of patients who received a large-head, primary MoM THA between 2005 and 2008 was performed with a minimum followup of 5 years. Twenty-six patients who had undergone revision of a primary MoM THA secondary to symptomatic ALTRs were recruited. The mean timeframe from primary MoM THA to symptomatic revision was 5.5 years (range, 1-10 years). Twenty-eight control subjects were randomly selected asymptomatic patients with no evidence of ALTRs on protocol-specific screening. Baseline demographics and high-resolution genotype (human leukocyte antigen [HLA] Class II) were collected for all patients. Cohorts were similar with respect to age at the time of primary MoM THA (mean, 54.8 versus 54.9 years, p = 0.95) and serum cobalt (mean, 5.5 versus 8.5 μg/L, p = 0.09) and chromium concentrations (mean, 2.9 versus 4.2 μg/L, p = 0.27). The association between genotype and revision surgery secondary to ALTRs was determined with gender as a covariate.

RESULTS

The prevalence of the risk genotype was 30% (16 of 54) among the entire cohort. Adjusting for sex, the odds of revision were 6.1 times greater among patients with the risk genotype present than among patients without (95% confidence interval [CI], 1.5-25.4; p = 0.01). Among females, the specificity of the risk genotype was 1.0 (95% CIexact, 0.5-1.0; pexact = 0.03), and for males, it was 0.8 (95% CIexact, 0.6-0.9; pexact < 0.01).

CONCLUSIONS

The findings of this study suggest that, among patients with a primary MoM THA, allelic variation within the HLA Class II loci may be a strong, independent risk factor associated with the need for subsequent revision surgery secondary to pseudotumor formation.

CLINICAL RELEVANCE

Given the hypothesis-generating nature of this novel undertaking, confirmatory prospective clinical studies are required to further elucidate this correlation and to explore the clinical utility of targeted genetic screening in this specific population. This research may, however, represent a key missing piece in the puzzle that is metal ion-induced pseudotumor formation.

What is appropriate surveillance for metal-on-metal hip arthroplasty patients?

The unexpected high revision rates of large-diameter (femoral head sizes of 36 mm or greater) metal-on-metal hip arthroplasties (MoMHAs) have led to worldwide regulatory authorities recommending regular surveillance, even for asymptomatic individuals. However, these recommendations are not evidence-based and are very costly. The rapidly evolving evidence base requires an update regarding the investigation and management of MoMHA patients. This article is the first of 2 (the second article in this series will consider the threshold for performing revision, and the outcomes following ARMD revision surgery: Matharu et al., Revision surgery of metal-on-metal hip arthroplasties for adverse reactions to metal debris: A clinical update. Acta Orthop 2018; in press), and considers the various investigative modalities used during surveillance, with specific focus on blood metal ion sampling and cross-sectional imaging. No single investigation can universally be used during MoMHA patient surveillance. Recent studies have now provided important information on interpreting blood metal ions (effective in identifying patients at low risk of problems), clarifying the roles of cross-sectional imaging (reserve combined ultrasound and MARS-MRI for complex cases), and providing parameters to safely exclude many asymptomatic patients from regular surveillance. This information will be useful when designing future surveillance protocols for MoMHA patients.

Pseudotumor in metal-on-metal hip arthroplasty: a comparison study of three grading systems with MRI

OBJECTIVE

Pseudotumors, a well-known complication of metal-on-metal total hip arthroplasty (MoM THA), are well identified on metal artifact-reducing sequences magnetic resonance imaging (MARS-MRI). Several MRI grading systems are described in the orthopedic literature, but their validity is unknown in large clinical studies. Our study was undertaken to describe the classification of pseudotumors in a preselected cohort divided into high- and low-risk patients, using three pseudotumor grading systems applied on MARS-MRI, and to determine the interobserver reliability of the grading systems.

PATIENTS AND METHODS

A retrospective study was performed on 377 consecutive patients (240 MRI scans) treated with an M2a-38 and Taperloc stem combination (Biomet, Warsaw, IN, USA). Patients were divided into a high-risk and a low-risk group based on previous published risk factors. Two observers determined the presence of pseudotumors using three different pseudotumor grading systems for classifying MARS-MRI results.

RESULTS

The prevalence of pseudotumors as determined with MARS-MRI was 59% in our high-risk group, 0% in the low-risk group and 43% in the control group. Serum cobalt values were increased in the high-risk group. The kappa values of the Anderson, Hauptfleisch and Matthies grading system scores were 0.43, 0.44, and 0.49 respectively.

CONCLUSIONS

High-risk patients are at a high risk for pseudotumor development. No pseudotumor development was found in low-risk patients. Interobserver reliability scored best with the Matthies system, but all three grading systems showed only a moderate agreement.

PET/CT to detect adverse reactions to metal debris in patients with metal-on-metal hip arthroplasty: an exploratory prospective study

Metal-on-metal (MoM) bearings in total hip arthroplasties and hip resurfacing arthroplasties have recently shown a new type of complication: adverse reactions to metal debris (ARMD). ARMD is characterized by local severe inflammation and tissue necrosis leading to implant failures. The gluteal muscle region is important for the patient outcome after revision surgery. This prospective positron emission tomography/computed tomography (PET/CT) study was undertaken to evaluate the characteristics of 2-deoxy-2-[¹⁸ F]fluoro-d-glucose ([¹⁸ F]FDG) and [⁶⁸ Ga]Gallium citrate ([⁶⁸ Ga]Citrate) PET/CT in ARMD patients. [¹⁸ F]FDG and [⁶⁸ Ga]Citrate PET/CT were performed in 18 hip arthroplasty patients: 12 ARMD patients (with 16 MoM hips) and six arthroplasty controls without ARMD. Tracer uptake was evaluated visually, and maximum standardized uptake (SUV_max ) was measured in the gluteal muscle region. ARMD severity was graded by metal artefact reduction sequence-magnetic resonance imaging (MARS-MRI). Periprosthetic [¹⁸ F]FDG uptake was observed in 15 of 16 hips, [⁶⁸ Ga]Citrate uptake in three of 16 hips, respectively. The distribution of tracer uptake resembled infection in three hips. In the gluteal muscle region, the SUV_max of [¹⁸ F]FDG was significantly greater in hips with moderate and severe ARMD compared with the controls (P = 0·009 for [¹⁸ F]FDG and P = 0·217 for [⁶⁸ Ga]Citrate). In patients who needed revision surgery, an intraoperative finding of gluteal muscle necrosis was associated with increased local SUV_max as detected by preoperative [¹⁸ F]FDG (P = 0·039), but not by [⁶⁸ Ga]Citrate (P = 0·301). In conclusion, the inflammatory reaction to metal debris in hip arthroplasty patients is best visualized with [¹⁸ F]FDG.

Microstructure and Surface Damage in Retrieved Metal-on-Metal Hip Arthroplasties

BACKGROUND

Besides promising results of metal-on-metal (MOM) hip arthroplasty (HA), frequent failures have been reported even in the short term. Many host, surgical, design, metallurgical, and processing factors have been evoked in the base of these events. We have tried to characterize and to evaluate metallurgical and processing features present in this type of implants.

METHODS

The acetabular and femoral components of 20 MOM HAs collected from a multicenter retrieval program were examined. All the specimens were inspected with naked eye, with confocal microscopy and vertical scanning interferometry, scanning electron microscopy, back-scattered electron imaging, and energy-dispersive X-ray spectroscopy, in 25 zones of each articular component.

RESULTS

Gas pores, shrinkage voids and holes of detached carbides, carbides on surface, embedded particles, scratches and marks of wear, surface discoloration, surface deposits, and tribochemical reaction layers were widely dispersed through a substantial percentage of the total bearing surface in all the implanted components. Surface cup and head voids, and cup scratches showed significant correlation with the clearance of pair. A higher surface damage of the cup and head was observed mainly in the low clearance prostheses. There was no other significant correlation or difference in the incidence and importance of any of these defects between resurfacing hip arthroplasties and total hip arthroplasties, or according to the pair diameter.

CONCLUSION

Some metallurgical features and surface damage were significantly present in the retrieved implants of MoM HAs. It would be desirable to improve the structure and metallurgical characteristics of these implants to avoid those effects and optimize their performance.

Biological effects of metal degradation in hip arthroplasties

Metals and metal alloys are the most used materials in orthopedic implants. The focus is on total hip arthroplasty (THA) that, though well tolerated, may be associated with local and remote adverse effects in the medium-long term. This review aims to summarize data on the biological consequences of the metal implant degradation that have been attributed predominantly to metal-on-metal (MoM) THA. Local responses to metals consist of a broad clinical spectrum ranging from small asymptomatic tissue lesions to severe destruction of bone and soft tissues, which are designated as metallosis, adverse reactions to metal debris (ARMD), aseptic lymphocytic vasculitis associated lesion (ALVAL), and pseudotumors. In addition, the dissemination of metal particles and ions throughout the body has been associated with systemic adverse effects, including organ toxicity, cancerogenesis, teratogenicity, and immunotoxicity. As proved by the multitude of studies in this field, metal degradation may increase safety issues associated with THA, especially with MoM hip systems. Data collection regarding local, systemic and long-term effects plays an essential role to better define any safety risks and to generate scientifically based recommendations.

Two-Stage Treatment of a Large Pelvic Cystic Pseudotumor in a Metal-On-Metal Total Hip Arthroplasty

The authors report a case of a huge cystic pseudotumor, surrounding a failed metal-on-metal total hip arthroplasty (THA). The cyst surrounded the hip anteriorly, occupied part of the anterior portion of the thigh, and extended to the anterolateral aspect of the abdomen. The case was treated by a two-stage procedure. The first stage consisted of a percutaneous drainage of the fluid content of the cyst (∼1,200 mL). This procedure reduced the risk of tearing the cyst capsule spreading the liquid in the tissues surrounding the THA, and in the abdomen. Thanks to this simple procedure, the second stage treatment consisted of a relatively usual THA revision. The patient recovered completely from the treatment and returned to pain-free full activities of daily living.

Allergic or Hypersensitivity Reactions to Orthopaedic Implants

Allergic or hypersensitivity reactions to orthopaedic implants can pose diagnostic and therapeutic challenges. Although 10% to 15% of the population exhibits cutaneous sensitivity to metals, deep-tissue reactions to metal implants are comparatively rare. Nevertheless, the link between cutaneous sensitivity and clinically relevant deep-tissue reactions is unclear. Most reactions to orthopaedic devices are type IV, or delayed-type hypersensitivity reactions. The most commonly implicated allergens are nickel, cobalt, and chromium; however, reactions to nonmetal compounds, such as polymethyl methacrylate, antibiotic spacers, and suture materials, have also been reported. Symptoms of hypersensitivity to implants are nonspecific and include pain, swelling, stiffness, and localized skin reactions. Following arthroplasty, internal fixation, or implantation of similarly allergenic devices, the persistence or early reappearance of inflammatory symptoms should raise suspicions for hypersensitivity. However, hypersensitivity is a diagnosis of exclusion. Infection, as well as aseptic loosening, particulate synovitis, instability, and other causes of failure must first be eliminated.

Surgical Approach May Influence Survival of Large-Diameter Head Metal-on-Metal Total Hip Arthroplasty: A 6- to 10-Year Follow-Up Study

Large-diameter head (LDH) metal-on-metal (MoM) total hip arthroplasty (THA) has lost popularity because of metal allergy or ALTRs (adverse local tissue reactions) in the past decade. Whether the surgical approach may influence the survival of LDH-MoM-THA has not been reported. From 2006 to 2009, we performed 96 LDH-MoM-THAs on 80 patients using an in situ head-neck assembly technique through a modified Watson-Jones approach. With a mean follow-up of 8.4 years (range, 6.3–10.1 years), the implant survival rate was 100%. All patients were satisfied with the results and the Harris Hip Score improved from 52 points to 98 points. No ALTRs were found, but 17.7% of the 96 hips (17 adverse events) experienced adverse events related to the cup, including 5 cases of outlier cup malposition, 11 cases of inadequate cup seating, and 1 acetabular fracture. The tissue tension that was improved by a muscle-sparing approach might lessen the chance of microseparation or edge-loading that is taken as the major risk for early implant failure. Further investigation of whether these LDH-MoM-THAs would fail or not would require a longer follow-up or even retrieval analysis in the future.

Correlation between serum metal ion levels and adverse local tissue reactions after Conserve® Plus hip resurfacing arthroplasty

BACKGROUND

Adverse local tissue reactions (ALTR) have been associated with the use of metal-on-metal (MoM) bearings and the monitoring of cobalt (Co) and chromium (Cr) ion levels in blood or serum may be the best way to evaluate in vivo the wear of these bearings. However, the relationship between Co and Cr ion concentrations and the formation of ALTR remains unclear.

METHODS

We investigated the relationship between ALTR and serum Co and Cr ion levels and identified the clinical factors influencing the formation of ALTR in patients treated with MoM hip resurfacing arthroplasties. 228 patients with unilateral Conserve® Plus MoM hip resurfacing had serum metal ion studies performed more than 1 year after surgery. Metal artifact reduction sequence magnetic resonance imaging (MARS MRI) was performed on subjects at risk for ALTR as determined by a screening protocol.

RESULTS

12 patients had ALTR. Logistic regression showed a strong association of ALTR with elevated ion levels and with low (<10 mm) contact patch to rim distance.

CONCLUSIONS

MoM bearings require enough functional coverage of the socket by design and then precise implantation to maximise functional coverage of the femoral ball, enhance lubrication, and avoid edge-loading wear.