Increased Mortality in Metal-on-Metal versus Non-Metal-on-Metal Primary Total Hip Arthroplasty at 10 Years and Longer Follow-Up: A Systematic Review and Meta-Analysis

Technology assistance in primary total knee replacement: hype or hope?

INTRODUCTION

Total knee replacement (TKR) reduces pain, it increases quality of life and it generally lasts a long time with revision rates of less than 5% at 10 years. Some authors have suggested that outcomes may be further improved by technology assistance.

AREAS COVERED

Technology assistance in primary TKR includes technologies such as navigated TKR, patient specific instrumentation TKR and robotic TKR.

EXPERT OPINION

In general, technology assistance results in higher accuracy of component positioning and alignment, but this is likely not clinically relevant as no clinically important difference in clinical outcomes, quality of life and complications such as revisions has been demonstrated in meta-analyses of randomized controlled trials. As technology assistance in primary TKR is increasingly used to capture patient and surgeon data, surgeons have an increasingly important role in protecting their patients' data and their own data. Real world evidence of implant registries has shown that TKR without technologically assistance can achieve perfectly acceptable outcomes. Although there is a genuine hope that technology-assisted TKR may further improve these outcomes, this hope is based on promises rather than solid evidence. At the same time, technology assisted TKR is heavily promoted including direct patient marketing, which are aspects of a hype.

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).

What enhances the in-hospital mortality following total hip arthroplasty? A national inpatient sample-based study

PURPOSE

With prolonged life expectancy and advancements in prosthetic designs, the proportion of patients belonging to diverse age groups undergoing total hip arthroplasty (THA) has progressively increased. In this context, the details regarding risk factors associated with mortality after THA, and its prevalence need to be clearly understood. This study sought to identify the possible co-morbidities associated with post-THA mortality.

METHODS

Based on Nationwide Inpatient Sample (NIS) database, patients undergoing THA from 2016 to 2019 (using ICD-10CMP) were identified. The included cohort was stratified into two groups: "early mortality" and "no mortality" groups. The data regarding patients' demographics, co-morbidities, and associated complications were compared between the groups.

RESULTS

Overall, 337,249 patients underwent THA, among whom, 332 (0.1%) died during their hospital admission ("early mortality" group). The remaining patients were included under "no mortality" group (336,917 patients). There was significantly higher mortality in the patients, who underwent emergent THA (as compared with elective THA: odd's ratio 0.075; p < 0.001). Based on multivariate analysis, presence of liver cirrhosis, chronic kidney disease (CKD) and previous history of organ transplant increased the odds of mortality {odds ratio [Exp (B)]} after THA by 4.66- (p < 0.001), 2.37-fold (p < 0.001) and 1.91-fold (p = 0.04), respectively. Among post-THA complications, acute renal failure (ARF), pulmonary embolism (PE), pneumonia, myocardial infarction (MI), and prosthetic dislocation increased the odds of post-THA mortality by 20.64-fold (p < 0.001), 19.35-fold (p < 0.001), 8.21-fold (p < 0.001), 2.71-fold (p = 0.05) and 2.54-fold (p < 0.001), respectively.

CONCLUSION

THA is a safe surgery with low mortality rate during early post-operative period. Cirrhosis, CKD, and previous history of organ transplant were the most common co-morbidities associated with post-THA mortality. Among post-operative complications, ARF, PE, pneumonia, MI, and prosthetic dislocation substantially enhanced the odds of post-THA mortality.

Constrained metal-on-metal hip arthroplasty: ever heard of a 50-year survival story?

BACKGROUND

The history of total hip arthroplasty dates back to the first half of the twentieth century. Data on hip endoprostheses implanted during the 1960s and 1970s suggest widely varying survival rates of the prosthesis.

CASE

A case of a patient who underwent total hip arthroplasty in 1972 using a Sivash prosthesis, developed in 1956 in the former Soviet Union, is presented in this article. The prosthesis has remained unrevised in the patient's body for 50 years and he continues to be widely free of implant-related symptoms. Despite the constrained metal-on-metal design of the implant, which can lead to adverse reactions to metal debris, no elevated systemic metal ion levels were detected.

CONCLUSION

The likelihood of encountering patients with prosthesis survival beyond 50 years is still rare. Nevertheless, changing demographics and the steadily improving designs and materials of hip endoprostheses may likely result in such cases.

The efficacy and safety of patient-specific instrumentation in primary total knee replacement: a systematic review and meta-analysis

INTRODUCTION

Patient-specific instrumentation (PSI) for primary total knee arthroplasty (TKA) surgery has been shown to increase accuracy of component positioning. However, it is unclear whether this also translates to actual benefits for patients in terms of better outcomes (efficacy) or less complications such as revisions (safety). We therefore systematically reviewed the literature to determine the efficacy and safety of PSI in primary TKA.

METHODS

Randomized controlled trials comparing PSI to non-PSI in primary TKA were included. A random effects model was used with meta-regression in case of heterogeneity.

RESULTS

Forty-three studies were included with a total of 1816 TKA in the PSI group and 1887 TKA in the control group. There were no clinically relevant differences between the PSI-group and non-PSI group regarding all outcomes. There was considerable heterogeneity: meta-regression analyses showed that the year the study was published was an important effect modifier. Early publications tended to show a positive effect for PSI compared to non-PSI TKA, whereas later studies found the opposite.

CONCLUSION

Based on evidence of moderate certainty, our study suggested that there were no clinically relevant differences in efficacy and safety between patients treated with PSI TKA and patients treated with non-PSI TKA.

Single Wedge Femoral Stem Designs are Associated With a Higher Risk for Revision After Cementless Primary Total Hip Arthroplasty

BACKGROUND

Cementless total hip arthroplasty (THA) femoral stems are the most commonly selected prostheses in the United States. Optimal stem geometry remains controversial with excellent survivorship reported for many designs. We compared cause-specific stem revision of single-wedge versus double-wedge designs from a multicenter US cohort.

METHODS

Data from an integrated healthcare network's total joint replacement registry were used to conduct a cohort study. Primary elective cementless THAs were identified (2001 to 2018). Implant exposure groups were classified by design geometry using the system proposed by Khanuja et al. Type 1 single-wedge (n = 11,082) and type 2 double-wedge (n = 32,380) designs were compared, and other design types were excluded; the final study cohort comprised 43,462 THAs. Cause-specific multivariable Cox regressions were used to evaluate risk for revision due to infection or aseptic reasons, including loosening, instability, periprosthetic fracture, or other reasons.

RESULTS

After adjustment for covariates, a higher aseptic revision risk was observed for type 1 when compared to type 2 designs (hazard ratio = 1.91, 95% confidence interval = 1.33-2.75). When looking at specific revision reasons, revision for aseptic loosening (hazard ratio = 3.46, 95% confidence interval = 2.24-5.34) was higher for type 1 versus type 2 designs. No differences were found for septic revision, instability, periprosthetic fracture, or revisions for other reasons.

CONCLUSIONS

Type 1 single-wedge designs were found to have a higher risk of revision due to aseptic loosening relative to type 2 double-wedge designs. Femoral stem geometry should be considered when selecting a cementless femoral implant.

LEVEL OF EVIDENCE

Level III.

Systemic Metal Ion Concentrations in Patients With Hip and Knee Megaprostheses: A Prospective Cohort Study

Background

Local tissue and serum metal ions have been shown to be elevated in some metal-on-metal and metal-on-polyethylene joint replacements. Local elevations have been linked to adverse local tissue reactions in some patients, and systemic elevation has been less commonly implicated cardiac and neurologic issues. Using a prospective study design, we aimed to identify the changes in serum metal ion levels after hip or knee megaprosthesis reconstruction. Furthermore, we will evaluate the occurrence of adverse effects and complications, possibly linked to metal ion elevation.

Methods

Fourteen consecutive patients receiving a Modular Universal Tumor Revision System megaprosthesis were enrolled. Blood samples were collected preoperatively and postoperatively to determine the serum ion concentrations of aluminum, chromium, cobalt, and silver. To evaluate the safety of the megaprostheses and the subsequently possible related (elevated) serum metal ion concentrations, all adverse effects and complications were registered until last outpatient clinic visit at the time of this study.

Results

Compared to the preoperative median serum concentrations, the postoperative median serum concentrations of chromium, silver, and cobalt increased 11-fold, 62-fold, and 64-fold, respectively. The median serum concentration of aluminum increased with 16%. Elevations were primarily noted in patients with knee prostheses. Eight patients had no adverse effects or complications during the period between preoperative and postoperative blood sampling. One adverse effect directly related to the serum metal ion concentrations, namely argyria, was observed.

Conclusions

This study documents significantly elevated concentrations of the metal ions, but only one adverse effect directly related to the metal ion concentrations was observed. Future studies are needed to further assess the impact of elevated metal ion levels after megaprostheses, specifically knee implants, which are metal-on-metal.

The parallels between particle induced lung overload and particle induced periprosthetic osteolysis (PPOL)

Background: When particles deposit for instance in the lung after inhalation or in the hip joint after local release from a hip implant material they can initiate a defense response. Even though these particles originate from inert materials such as polyethylene (PE) or titanium, they may cause harm when reaching high local doses and overwhelming local defense mechanisms. Main body: This paper describes the parallels between adverse outcome pathways (AOP) and particle properties in lung overload and periprosthetic osteolysis (PPOL). It is noted that in both outcomes in different organs , the macrophage and cytokine orchestrated persistent inflammation is the common driver of events, in the bone leading to loss of bone density and structure, and in the lung leading to fibrosis and cancer. Most evidence on lung overload and its AOP is derived from chronic inhalation studies in rats, and the relevance to man is questioned. In PPOL, the paradigms and metrics are based on human clinical data, with additional insights generated from in vitro and animal studies. In both organ pathologies the total volume of particle deposition has been used to set threshold values for the onset of pathological alterations. The estimated clinical threshold for PPOL of 130 mg/ml is much higher than the amount to cause lung overload in the rat (10 mg/ml),although the threshold in PPOL is not necessarily synonymous to particle overload. Conclusions: The paradigms developed in two very different areas of particle response in the human body have major similarities in their AOP. Connecting the clinical evidence in PPOL to lung overload challenges relevance of rat inhalation studies to the human lung cancer hazard. .

Revision Risk in a Cohort of US Patients Younger Than 55 Undergoing Primary Elective Total Hip Arthroplasty

BACKGROUND

As indications for elective total hip arthroplasty (THA) expand to younger patients, we sought to (1) compare revision risk following primary elective THA in patients <55 years at the time of their THA to patients aged ≥65 years and (2) identify specific risk factors for revision in patients <55 years.

METHODS

A Kaiser Permanente's total joint replacement registry was used to conduct a cohort study including primary elective THA patients aged ≥18 (2001-2018). In total, 11,671 patients <55 years and 53,106 patients ≥65 years were included. Multiple Cox regression was used to evaluate cause-specific revision risk, including septic revision, aseptic loosening, instability, and periprosthetic fracture. Stepwise Cox regression was used to identify patient and surgical factors associated with cause-specific revision in patients <55 years.

RESULTS

Patients <55 years had a higher risk of septic revision (hazard ratio [HR] = 1.30, 95% confidence interval [CI] = 1.02-1.66), aseptic loosening (HR = 2.60, 95% CI = 1.99-3.40), and instability (HR = 1.35, 95% CI = 1.09-1.68), but a lower risk of revision for periprosthetic fracture (HR = 0.36, 95% CI = 0.22-0.59) compared to patients aged ≥65 years. In the <55 age group, risk factors for septic revision included higher body mass index, drug abuse, and liver disease. Hypertension, anterior approach, and ceramic-on-ceramic were associated with aseptic loosening. White race, American Society of Anesthesiologists classification ≥3, smoker, paralysis, posterior approach, ceramic-on-ceramic, and smaller head diameter were associated with instability.

CONCLUSION

Identified risk factors varied depending on the cause for revision. Although septic revisions were related to patient characteristics, more modifiable factors, such as implant or surgical approach, were associated with revision due to aseptic loosening and instability.

LEVEL OF EVIDENCE

III.

Decreased mortality and increased side effects in COVID-19 patients treated with IL-6 receptor antagonists: systematic review and meta-analysis

There is controversy whether IL-6 (receptor) antagonists are beneficial in treating COVID-19 patients. We therefore update our systematic review to answer the following research questions: (1) Do patients hospitalized for COVID-19 treated with IL-6 (receptor) antagonists have lower mortality compared to standard of care? (2) Do patients hospitalized for COVID-19 treated with IL-6 (receptor) antagonists have more side effects compared to standard of care? The following databases were search up to December 1st 2020: PubMed, PMC PubMed Central, MEDLINE, WHO COVID-19 Database, Embase, Web-of-Science, COCHRANE LIBRARY, Emcare and Academic Search Premier. In order to pool the risk ratio (RR) and risk difference of individual studies we used random effects meta-analysis. The search strategy retrieved 2975 unique titles of which 71 studies (9 RCTs and 62 observational) studies comprising 29,495 patients were included. Mortality (RR 0.75) and mechanical ventilation (RR 0.78) were lower and the risk of neutropenia (RR 7.3), impaired liver function (RR 1.67) and secondary infections (RR 1.26) were higher for patients treated with IL-6 (receptor) antagonists compared to patients not treated with treated with IL-6 (receptor) antagonists. Our results showed that IL-6 (receptor) antagonists are effective in reducing mortality in COVID-19 patients, while the risk of side effects was higher. The baseline risk of mortality was an important effect modifier: IL-6 (receptor) antagonists were effective when the baseline mortality risk was high (e.g. ICU setting), while they could be harmful when the baseline mortality risk was low.

An integrated benefit-risk assessment of cobalt-containing alloys used in medical devices: Implications for regulatory requirements in the European Union

In 2017, the European Union (EU) Committee for Risk Assessment (RAC) recommended the classification of metallic cobalt (Co) as Category 1B with respect to its carcinogenic and reproductive hazard potential and Category 2 for mutagenicity but did not evaluate the relevance of these classifications for patients exposed to Co-containing alloys (CoCA) used in medical devices. CoCA are inherently different materials from Co metal from a toxicological perspective and thus require a separate assessment. CoCA are biocompatible materials with a unique combination of properties including strength, durability, and a long history of safe use that make them uniquely suited for use in a wide-range of medical devices. Assessments were performed on relevant preclinical and clinical carcinogenicity and reproductive toxicity data for Co and CoCA to meet the requirements under the EU Medical Device Regulation triggered by the ECHA re-classification (adopted in October 2019 under the 14th Adaptation to Technical Progress to CLP) and to address their relevance to patient safety. The objective of this review is to present an integrated overview of these assessments, a benefit-risk assessment and an examination of potential alternative materials. The data support the conclusion that the exposure to CoCA in medical devices via clinically relevant routes does not represent a hazard for carcinogenicity or reproductive toxicity. Additionally, the risk for the adverse effects that are known to occur with elevated Co concentrations (e.g., cardiomyopathy) are very low for CoCA implant devices (infrequent reports often reflecting a unique catastrophic failure event out of millions of patients) and negligible for CoCA non-implant devices (not measurable/no case reports). In conclusion, the favorable benefit-risk profile also in relation to possible alternatives presented herein strongly support continued use of CoCA in medical devices.

Decreased Mortality in Coronavirus Disease 2019 Patients Treated With Tocilizumab: A Rapid Systematic Review and Meta-analysis of Observational Studies

Background

We systematically reviewed the literature to answer the following research questions: 1) does IL-6 (receptor) antagonist therapy reduce mortality in COVID-19 patients compared to patients not treated with IL-6 (receptor) antagonists and 2) is there an increased risk of side effects in COVID-19 patients treated with IL-6 (receptor) antagonists compared to patients not treated with IL-6 (receptor) antagonists?.

Methods

We systematically searched PubMed, PMC PubMed Central, MEDLINE, WHO COVID-19 Database, Embase, Web-of-Science, COCHRANE LIBRARY, Emcare and Academic Search Premier (until June 30th2020). Random effects meta-analysis was used to pool the risk ratio and risk difference of individual studies. Risk of bias was appraised using the MINORS checklist.

Results

The search strategy retrieved 743 unique titles of which 10 studies (all on tocilizumab) comprising 1358 patients were included. Nine out of ten studies were considered to be of high quality. Meta-analysis showed that the tocilizumab group had lower mortality than the control group. The risk ratio (RR) was 0.27 95%CI 0.12 to 0.59 and the risk difference (RD) was 12% 95%CI 4.6% to 20% in favour of the tocilizumab group. With only a few studies available there were no differences observed regarding side effects.

Conclusions

Our results showed that mortality was 12% lower for COVID-19 patients treated with tocilizumab compared to COVID-19 patients who were not treated with tocilizumab. The number needed to treat was 11, suggesting that for every 11 (severe) COVID-19 patients treated with tocilizumab 1 death is prevented. These results require confirmation by randomized controlled trials.

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

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

Survival at 11 to 21 years for 779 Metasul® metal-on-metal total hip arthroplasties

BACKGROUND

Total hip arthroplasties (THAs) bearing is one of the most important factors for hip replacement because THA survival depends on it. Metal-on-metal (MoM) bearing has lower wear than metal-on-polyethylene but lot of aseptic loosening decrease utilization. We analyze the survival rate of 28 mm Metasul® bearings after a mean follow-up of 12.9 years.

METHODS

The main objective of this study was to evaluate the survival of the MoM. We evaluate 779 consecutive THAs performed between January 1995 and December 2005 for primary osteoarthritis, congenital dysplasia classified Crowe I, or rheumatoid arthritis. Survival rate was calculated by the Kaplan-Meir method. The association between survival and age, gender, body mass index (BMI), and surface coating was investigated with a proportional odds model. The clinical assessment included Oxford score.

RESULTS

Six hundred fifty-two THAs were reviewed. Sixty-two revisions (9.5%) were performed including 34 aseptic loosening and 11 deep infections. The survival for prosthesis with any reason at 20 years was 87% (confidence interval (CI) 83-90.2) for aseptic loosening at 20 years was 90.1% (CI 87-93.8). There was no association with age, BMI, and surface coating. Gender was significant with lower aseptic loosening for men, hazard ratio = 0.45, p value = 0.035. Oxford score was 57 ± 6.7 (19-60).

CONCLUSION

The survival rate of Metasul was well and seems to be like our clinical finding. However, radiographic aseptic loosening without surgery is not included in the survival rate. The Oxford score was very good with a lot of patients with asymptomatic hip.

LEVEL OF EVIDENCE

Level IV/Retrospective study.

It's worth cleaning - The examination of the female taper could identify a particular cause of trunnionosis at revision 16 years after total hip arthroplasty

Adverse reaction to metal debris (ARMD) is an issue in metal-on-metal (MoM) total hip replacements (THR). It mainly affects large-head MoM THR, whereas 28-32 mm MoM pairings are associated with low long-term revision rates. However, the bearing surface is not necessarily the only cause of metal debris. This report documents with advanced analysis of the retrievals a particular cause of trunnionosis in late failure of a small diameter MoM THR and illustrates the importance of cleaning of the taper when seating the head in THR. A 65-year-old patient was revised due to ARMD 16 years after small diameter MoM THR. Debridement and exchange of the inlay and the head had been performed through an anterior approach. While the cup and the outer surface of the head were accessible to direct analysis by an optical coordinate measuring machine, the female taper had to be analysed indirectly by measuring an imprint. Wear from the cup and the head was within expected low ranges. The analysis of the female taper identified bone fragments, which contributed to trunnionosis. Failure due to ARMD after MoM THR is not necessarily caused by the bearing, but can be due to trunnionosis. Bone fragments within the taper contact in this case highlight the importance of meticulous cleaning of the taper before seating the head, to avoid trunnionosis.

15-year follow-up of MoM 36-mm THA: clinical, laboratory, and radiological (CT and MRI) prospective assessment

INTRODUCTION

There is limited knowledge of the long-term results of metal-on-metal total hip arthroplasty (MoM THA), particularly concerning adverse local tissue reaction (ALTR), Co/Cr ions level and revision rate. Even if MoM bearing surfaces are no longer used, long-term data could help in defining the course and best management for these patients. The purpose of this study is to investigate the clinical outcomes, describe radiological findings including CT metal artefact reduction algorithm for orthopaedic implants (O-MAR) and MRI multi acquisition variable resonance image combination (MAVRIC) in 36-mm MoM THA.

METHODS

In this long-term prospective study, 46 consecutive patients with primary MoM THA (mono- or bilateral) were enrolled between 2004 and 2005. Pinnacle acetabular cup, Summit cementless stem with 36-mm metal head and Ultamet CoCr alloy liner (Depuy Inc.) were implanted, in the same centre by the same senior surgeon. Patients were reviewed at 5-, 10- and 15-years, including Co/Cr levels and standard radiographs at every follow-up, whilst the 15-year follow-up included hip sonography, MRI MAVRIC and CT O-MAR.

RESULTS

At 15 years, the overall survival rate of the implants (both stems and cups) was 83% (30/36). Revisions were performed in 9% (4/46) because of ALTR, 2% (1/46) septic loosening and 2% periprosthetic fracture. Both Cr and Co concentration increased over time, even though remaining at low level risk at 15 years: Co from 0.11 (+/- 0.18) to 4.29 (+/- 3.26) and Cr from 0.38 (+/- 0.32) to 1.37 (+/- 1.15). Functional scores in non-revised patients showed good to excellent results in more than 90%. Engh-score correlated with time from surgery (p = 0.017) and with sonographic, CT and RM findings (p < 0.05). Concordance has been found between CT and MRI findings (sign-rank test, p = 0.241; Intraclass Correlation Coefficients 0.987); however, no specific MRI or CT lesion patterns could be recognised among symptomatic and non-symptomatic patients.

DISCUSSION

The long-term rate of ALTR after 36-mm MoM THA was comparable with previous studies; a regular follow-up for those implants is mandatory. During follow-up Co-Cr levels increased over time and radiography was a suitable screening technique; the Engh score in particular, proved to be a reliable assessment tool. CT O-MAR and MRI with MAVRIC protocols may add valuable data in clinical practice, although MRI is significantly more efficient than CT in the identification of ALTR lesions, peri-articular effusion and in the evaluation of soft tissues.

Global diversity in bearings in primary THA

Choice of articulating materials, head size and the design of the articulation will become decisive for the long-term performance of a total hip arthroplasty (THA) and especially in terms of risk for dislocation and wear-related problems. Here we account for common alternatives based on available studies and the evidence that can be derived from them.Metal or ceramic femoral heads articulating against a liner or cup made of highly cross-linked polyethylene and ceramic-on-ceramic articulations have about similar risk for complications leading to revision, whereas the performance of metal-on-metal articulations, especially with use of big heads, is inferior. The clinical significance of problems related to ceramic-on-ceramic articulations such as squeaking remains unclear. With use of current technology ceramic fractures are rare.Large femoral heads have the potential to increase the range of hip movement before impingement occurs and are therefore expected to reduce dislocation rates. On the other hand, issues related to bearing wear, corrosion at the taper-trunnion junction and groin pain may arise with larger heads and jeopardize the longevity of THA. Based on current knowledge, 32-mm heads seem to be optimal for metal-on-polyethylene bearings. Patients with ceramic-on-ceramic bearings may benefit from even larger heads such as 36 or 40 mm, but so far there are no long-term reports that confirm the safety of bearings larger than 36 mm.Assessment of lipped liners is difficult because randomized studies are lacking, but retrospective clinical studies and registry data seem to indicate that this liner modification will reduce the rate of dislocation or revision due to dislocation without clear evidence of clinically obvious problems due to neck-liner impingement.The majority of studies support the view that constrained liners and dual mobility cups (DMC) will reduce the risk of revision due to dislocation both in primary and revision THA, the latter gaining increasing popularity in some countries. Both these devices suffer from implant-specific problems, which seem to be more common for the constrained liner designs. The majority of studies of these implants suffer from various methodological problems, not least selection bias, which calls for randomized studies preferably in a multi-centre setting to obtain sufficient power. In the 2020s, the orthopaedic profession should place more effort on such studies, as has already been achieved within other medical specialties, to improve the level of evidence in the choice of articulation when performing one of the most common in-hospital surgical procedures in Europe. Cite this article: EFORT Open Rev 2020;5:763-775. DOI: 10.1302/2058-5241.5.200002.

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.

MoM total hip replacements in Europe: a NORE report

The purpose of this paper is to determine the prevalence of metal-on-metal (MoM) total hip replacement (THR) in European registries, to assess the incidence of revision surgery and to describe the national follow-up guidelines for patients with MoM THR including resurfacings.

Eleven registries of the Network of Orthopaedic Registries of Europe (NORE) participated totalling 54 434 resurfacings and 58 498 large stemmed MoM THRs.

The resurfacings and stemmed large head MoM had higher pooled revision rates at five years than the standard total hip arthroplasties (THA): 6.0%, 95% confidence interval (CI) 5.3 to 6.8 for resurfacings; 6.9%, 95% CI 4.4 to 9.4 for stemmed large head MoM; and 3.0%, 95% CI 2.5 to 3.6 for conventional THA.

The resurfacings and stemmed large head MoM had higher pooled revision rates at ten years than the standard THAs: 12.1%, 95% CI 11.0 to 13.3 for resurfacings; 15.5%, 95% CI 9.0 to 22 for stemmed large head MoM; and 5.1%, 95% CI 3.8 to 6.4 for conventional THA.

Although every national registry reports slightly different protocols for follow-up, these mostly consist of annual assessments of cobalt and chromium levels in blood and MRI (MARS) imaging.

Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180078

Total Hip Arthroplasty in Young Patients in The Netherlands: Trend Analysis of >19,000 Primary Hip Replacements in the Dutch Arthroplasty Register

BACKGROUND

Total hip arthroplasty (THA) is one of the most successful interventions in medical care. Because of shifting trends in THA and failure rates being higher in younger patients, we aimed to assess trends in implant fixation, bearing type, head diameter, and surgical approach in patients younger than 55 years in the Netherlands using data from the Dutch Arthroplasty Register.

METHODS

Trends in the method of implant fixation, bearing type, head diameter, and surgical approach were analyzed over year of surgery (2007-2016) and over age groups (<25, 25-29, 30-34, 35-39, 40-44, 45-49, and 50-54 years).

RESULTS

Between 2007 and 2016, a total of 19,915 primary THAs were performed in patients <55 years. Osteoarthritis was the most prevalent diagnosis (66.1%). Uncemented fixation was used in 79.5% of all performed THAs. The use of 32-mm head diameters increased (from 32.6% in 2007 to 50.1% in 2016), where an increasing trend toward the use of ceramic-on-polyethylene as most frequently used bearing type was present (from 37.5% in 2007 to 53.8% in 2016). The posterolateral surgical approach was the most frequently used approach; however, the anterior approach is used increasingly (0.1% in 2007 to 21.1% in 2016). Ceramic-on-polyethylene bearing surfaces, 32-mm head diameters, and the anterior approach were most commonly used in patients between 50 and 54 years.

CONCLUSION

There was a clear preference for uncemented fixation in young patients. In head diameter, bearing type, and surgical approach, clear trends were visible. Characteristics of THA in young patients were subject to changing perspectives.

Engineering standards for trauma and orthopaedic implants worldwide: a systematic review protocol

INTRODUCTION

Despite multiple scandals in the medical implant sector, premarket testing has been the attention of little published research. Complications related to new devices, such as the DePuy Articular Surface Replacement (ASR, DePuy Synthes, USA), have raised the issue of how designs are tested and whether engineering standards remain up to date with our understanding of implant biomechanics. Despite much work setting up national joint registries to improve implant monitoring, there have been few academic studies examining the premarket engineering standards new implants must meet. Emerging global economies mean that the markets have changed, and it is unknown to what degree engineering standards vary around the world. Governments, industry and independent regulatory bodies all produce engineering standards; therefore, the comparison of surgical implants across different manufacturers and jurisdictions is difficult. In this review, we will systematically collate and compare engineering standards for trauma and orthopaedic implants around the world. This will help inform patient, hospital and surgeon choice and provide an evidence base for future research in this area.

METHODS AND ANALYSIS

This protocol is based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocol (PRISMA-P) guidelines. We will conduct a systematic review of trauma and orthopaedic engineering standards from four main sources of information as identified in our preliminary scoping searches: governments, industry, independent regulatory bodies and engineering and medical publications. Any current standard relevant to trauma and orthopaedic implants will be included. We will use a predefined search strategy and follow the recommendations of the Cochrane handbook where applicable. We will undertake a narrative synthesis with qualitative evaluation of homogeneity between engineering standards.

ETHICS AND DISSEMINATION

No ethics approval is required as no primary data are being collected. The results will be made available by peer-reviewed publication and reported according to PRISMA-P guidelines.

Midterm risk of cancer with metal-on-metal hip replacements not increased in a Finnish population

Background and purpose - Metal-on-metal (MoM) total hip arthroplasty (THA) and hip resurfacing arthroplasty (HRA) have been widely used during the early 21st century. We assessed the midterm risk of cancer of patients treated with modern MoM hip implants compared with patients with non-MoM hip implants and the general Finnish population with special interest in soft tissue sarcomas and basalioma due to the findings of our previous report. Patients and methods - All large-diameter head MoM THAs and hip resurfacings performed in Finland between 2001 and 2010 were extracted from the Finnish Arthroplasty Register (10,728 patients). Patients who underwent conventional THA formed the non-MoM reference cohort (18,235 patients). Data on cancer cases up to 2014 were extracted from the Finnish Cancer Registry. The relative risk of cancer in the general population was expressed as the ratio of observed to expected number of cases, i.e., standardized incidence ratio (SIR). Poisson regression analysis was used to compare the cancer risk between the cohorts. The mean follow-up was 7.4 years (1-14) in the MoM cohort and 8.4 years (1-14) in the non-MoM cohort. Results - The overall risk of cancer in the MoM cohort was comparable to the general Finnish population (SIR 0.9, 95% CI 0.9-1.0). Risk of basalioma in the MoM cohort was higher than in the general Finnish population (SIR 1.2, CI 1.1-1.4) and higher than in the non-MoM cohort in the stratified regression analysis (RR 1.2, CI 1.0-1.4, p = 0.02). The SIR of soft-tissue sarcoma in the MoM cohort was 1.4 (CI 0.6-2.8); the incidence was same as in the non-MoM cohort. Interpretation - Metal-on-metal hip implants are not associated with an increased overall risk of cancer during midterm follow-up.

Cobalt and its compounds: update on genotoxic and carcinogenic activities

This article summarizes recent experimental and epidemiological data on the genotoxic and carcinogenic activities of cobalt compounds. Emphasis is on the respiratory system, but endogenous exposure from Co-containing alloys used in endoprostheses, and limited data on nanomaterials and oral exposures are also considered. Two groups of cobalt compounds are differentiated on the basis of their mechanisms of toxicity: (1) those essentially involving the solubilization of Co(II) ions, and (2) metallic materials for which both surface corrosion and release of Co(II) ions act in concert. For both groups, identified genotoxic and carcinogenic mechanisms are non-stochastic and thus expected to exhibit a threshold. Cobalt compounds should, therefore, be considered as genotoxic carcinogens with a practical threshold. Accumulating evidence indicates that chronic inhalation of cobalt compounds can induce respiratory tumors locally. No evidence of systemic carcinogenicity upon inhalation, oral or endogenous exposure is available. The scarce data available for Co-based nanosized materials does not allow deriving a specific mode of action or assessment for these species.

The risk of cardiac failure following metal-on-metal hip arthroplasty

AIMS

The aim of this study was to determine whether patients with metal-on-metal (MoM) arthroplasties of the hip have an increased risk of cardiac failure compared with those with alternative types of arthroplasties (non-MoM).

PATIENTS AND METHODS

A linkage study between the National Joint Registry, Hospital Episodes Statistics and records of the Office for National Statistics on deaths was undertaken. Patients who underwent elective total hip arthroplasty between January 2003 and December 2014 with no past history of cardiac failure were included and stratified as having either a MoM (n = 53 529) or a non-MoM (n = 482 247) arthroplasty. The primary outcome measure was the time to an admission to hospital for cardiac failure or death. Analysis was carried out using data from all patients and from those matched by propensity score.

RESULTS

The risk of cardiac failure was lower in the MoM cohort compared with the non-MoM cohort (adjusted hazard ratio (aHR) 0.901; 95% confidence interval (CI) 0.853 to 0.953). The risk of cardiac failure was similar following matching (aHR 0.909; 95% CI 0.838 to 0.987) and the findings were consistent in subgroup analysis.

CONCLUSION

The risk of cardiac failure following total hip arthroplasty was not increased in those in whom MoM implants were used, compared with those in whom other types of prostheses were used, in the first seven years after surgery. Cite this article: Bone Joint J 2018;100-B:20-7.

Are Trends in Total Hip Arthroplasty Bearing Surface Continuing to Change? 2007-2015 Usage in a Large Database Cohort

BACKGROUND

Bearing surface issues related to trunnionosis or metal-on-metal (MoM) articulations have likely impacted recent trends in bearing surface choice. The purpose of this study is to evaluate trends in total hip arthroplasty (THA) bearing surface use, including 2015 data, with respect to the date of operation and patient demographics.

METHODS

The Humana dataset was reviewed from 2007 through 2015 to analyze bearing surface usage in primary THA. Four bearing surface types were identified by International Classification of Disease, 10th Revision codes and trended throughout the years: metal-on-polyethylene (MoP), ceramic-on-ceramic (CoC), ceramic-on-polyethylene (CoP), and MoM. Prevalence was analyzed as a function of age and sex.

RESULTS

Of the 28,504 primary THA procedures, the most commonly used bearing was MoP (46.1%), followed by CoP (33.2%), MoM (17.1%), and ceramic-on-ceramic (3.6%). The use of CoP bearings significantly increased from 6.4% in 2007 to 52.0% in 2015, while MoM bearings decreased during this period. MoP bearings decreased over 2012-2015 (P < .001). CoP usage decreased with age, while MoP bearings increased with a transition occurring at 65-69 years of age. Women were more likely to receive MoP bearings (odds ratio [OR] 1.2), while men were more likely to receive MoM and CoP bearings (OR 1.1). Multivariate logistic regression showed age to be an independent predictor of bearing surface choice with patients 65 and older more likely to receive MoP bearings (OR 3.2).

CONCLUSION

Bearing surface choice in primary THA has changed tremendously from 2007 to 2015. MoM bearing use has decreased as a result of adverse effects. Age continues to remain a significant factor in bearing surface choice.

Challenges in Total Hip Arthroplasty in the Setting of Developmental Dysplasia of the Hip

BACKGROUND

Developmental dysplasia of the hip (DDH) is a recognized cause of secondary arthritis, which may eventually lead to total hip arthroplasty (THA). An understanding of the common acetabular and femoral morphologic abnormalities will aid the surgeon in preparing for the complexity of the surgical case.

METHODS

We present the challenges associated with acetabular and femoral morphologies that may be present in the dysplastic hip and discuss surgical options to consider when performing THA. In addition, common complications associated with this population are reviewed.

RESULTS

The complexity of THA in the DDH patient is due to a broad range of pathomorphologic changes of the acetabulum and femur, as well as the diverse and often younger age of these patients. As such, THA in the DDH patient may offer a typical primary hip arthroplasty or be a highly complex reconstruction. It is important to be familiar with all the subtleties associated with DDH in the THA population. The surgeon must be prepared for bone deficiency when reconstructing the acetabulum and should place the component low and medial (at the anatomic hip center), and avoid oversizing the acetabular component. Femoral dysplasia is also complex and variable, and the surgeon must be prepared for different stem choices that allow for decoupling of the metaphyseal stem fit from the implanted stem version. In Crowe III and IV dysplasia, femoral derotation/shortening osteotomy may be required. Many complications associated with THA in the DDH patient may be mitigated with careful planning and surgical technique.

CONCLUSION

Performed correctly, THA can yield excellent results in this complex patient population.