Hypersensitivity reactions to metallic implants - diagnostic algorithm and suggested patch test series for clinical use

Hypoallergenic Knee Implant Usage and Clinical Outcomes: Are They Safe and Effective?

Background

One of the most debated topics in modern total knee arthroplasty (TKA) is the impact of metal hypersensitivity (MH) as a potential cause of prosthesis failure. Implanting hypoallergenic prostheses to avoid potential problems in suspected cases of MH is one treatment option that can be used in such cases. However, their long-term clinical safety and efficacy are not well proven.

Methods

All literature relevant to modern hypoallergenic implants were reviewed and summarized to provide a comprehensive synopsis. In addition, a detailed literature search was performed on PUBMED, MEDLINE, and Google Scholar to identify all the clinical studies reporting outcomes for hypoallergenic knee implants. Our search was confined to those studies published as full manuscripts in the English language from July 2018 to July 2023.

Results

To minimize the risk of MH, new implant variants have been developed which are either under clinical evaluation or in routine clinical use. These include conventional metal implants with protective coatings (mono- or multilayer) and metal-free implants. However, there is insufficient clinical data to confirm the rationale and effectiveness of using these "hypoallergenic" TKA implants.

Conclusions

Published studies and arthroplasty registry data analyses indicate no significant differences between hypoallergenic and standard TKAs with overall good survival rates. In the future, further high-quality studies are needed to better understand the complexity of this subject.

A literature review and expert consensus statement on diagnostics in suspected metal implant allergy

BACKGROUND

Although rare, allergic reactions to metal implants represent a diagnostic challenge in view of missing guidelines.

OBJECTIVES

To develop an European expert consensus on characteristics of metal allergy reactions and the utility of various diagnostic tools in suspected metal implant allergy.

METHODS

A nominal group technique (NGT) was applied to develop consensus statements. Initially an online literature database was created on a secure server to enable a comprehensive information. Twenty-three statements were formulated on potential aspects of metal implant allergy with a focus on diagnostics and grouped into five domains. For the consensus development, the panel of 12 experts initially did refine and reformulate those statements that were ambiguous or had unclear wording. By face-to-face (9/12) or virtual participation (3/12), an anonymous online voting was performed.

RESULTS

Consensus (≥80% of agreement) was reached in 20/23 statements. The panel agreed that implant allergy despite being rare should be considered in case of persistent unexplained symptoms. It was, however, recommended to allow adequate time for resolution of symptoms associated with healing and integration of an implant. Obtaining questionnaire-aided standardized medical history and standardized scoring of patient outcomes was also considered an important step by all experts There was broad consensus regarding the utility/performance of patch testing with additional late reading. It was recognized that the lymphocyte transformation test (LTT) has to many limitations to be generally recommended. Prior to orthopaedic implant, allergy screening of patients without a history of potential allergy to implant components was not recommended.

CONCLUSIONS

Using an expert consensus process, statements concerning allergy diagnostics in suspected metal implant allergy were created. Areas of nonconsensus were identified, stressing uncertainty among the experts around topics such as preoperative testing in assumed allergy, histological correlate of periimplant allergy and in vitro testing, which underscores the need for further research.

Advantages and limitations of mobile-bearing unicompartmental knee arthroplasty: an overview of the literature

INTRODUCTION

Interest in unicompartmental knee arthroplasty (UKA) has recently grown. Mobile bearing UKA, in which the bearing is not fixed but rather perfectly conforms with femoral and tibial components and moves completely passively between the femoral and tibial implant, has now been used for approximately half a century.

AREAS COVERED

Alongside the recognized advantages of UKA, the mobile-bearing variant benefits from an extremely low rate of polyethylene wear and tolerable minor malalignment. Revision rates for UKA have been reported to exceed those of total knee arthroplasty, but long-term survival rates and outcomes from mobile-bearing UKA have been found to be satisfactory. In addition to the lateral osteoarthritis and loosening, which are main complications of UKA, bearing dislocation is a specific complication of mobile bearing UKA. Fractures and valgus subsidence are more prevalent than in the cementless UKA. While these continue to be features to be addressed, they have been partially solved.

EXPERT OPINION

Given the manifold benefits of UKA, its application could be extended to a larger patient population. Successful outcomes rely on careful patient selection and the surgeon's extensive familiarity with the procedure. Looking ahead, the incorporation of robotic surgery, already a feature of some fixed-bearing UKAs, might shape the future trajectory of mobile-bearing UKA.

Metal implant allergy: A retrospective cohort analysis at a university allergy practice

Background: Concern of metal sensitization in pre- and postsurgical evaluation is growing, with the recent guidelines remaining the criterion standard for consideration of patch testing. Information remains scarce on surgical screening in the groups of patients who reported a history of metal sensitivity versus those with no reported history. Objective: The objective of this study was to assess the utility of patch testing in surgical candidates based on reported metal allergy history. The secondary objective was to evaluate the utility and outcomes in postsurgical patch testing. Methods: Nine hundred and thirty-one patient charts of patients with the diagnosis of "contact dermatitis" who underwent an evaluation at a single allergy clinic site between January 2013 and December 2022 were identified and reviewed as part of a retrospective chart review study. Patients were included in subgroups based on the time of patch testing and history of reported metal allergy. Results: In all, 67 patients underwent patch testing, 10 (14.9%) of whom were surgical candidates without a history of metal sensitivity, 31 (46.2%) of whom were surgical candidates with a history of metal sensitivity, and 26 (38.8%) of whom were postsurgical patients. Twenty-nine (43.3%) of patients had positive patch testing results, with only one (10%) in the presurgical group, 17 (54.8%) in the presurgical with a history of metal sensitivity, and 11 (42.3%) in the postsurgical group. Zero patients in our cohort without metal sensitivity who were undergoing the Nuss procedure had positive reactions on patch testing, whereas two of four (50%) with reported metal sensitivity who were undergoing the Nuss procedure had positive relevant metal reactions. Conclusion: Ambiguity in the utility of patch testing for surgical decision making remains, despite common utilization. Recent guidelines along with coordination of care among the surgeon, allergist, and patient remains the criterion standard of care.

The contribution of metal allergy to the failure of metal alloy implants, with special reference to titanium: Current knowledge and controversies

After almost three-quarters of a century during which contact dermatologists have often struggled to comprehend the relationship between metal allergy and failure of metal-alloy containing implant, it is possible to say that a relationship does exist, particularly for cobalt and chromium, but also for nickel. There is still debate as to whether allergy develops as a consequent of failure but thenceforth contributes to it, or whether sensitisation starts first and induces failure secondarily-opinion probably favours the first. Metal-on-polypropylene articulations were associated with few metal allergic problems but now are less favoured by orthopaedists due to plastic wear products causing osteolysis and pseudotumour formation through local inflammation. New metal alloys are regularly being introduced such that interested dermatologists need to stay on top of the situation. The jury is still out as to whether the recent favouring of titanium-containing alloys will confirm them to be more inert allergenically. Case reports do show some clinical reactions to titanium-containing implants and patch test series have inferred sometimes quite a high background rate of allergy, but interpretation must be tempered by the awareness that titanium salts on patch testing have a tendency to cause irritant reactions. Blood monitoring of metal ion values is now recommended in certain situations after joint replacement and increasing levels may be an indication that allergy with joint failure can develop, in which case patch testing is indicated, and suggested series are available. Predictive patch testing, whilst generally not recommended in the past, has been introduced into some protocols often by non-dermatologists, such that it is now needed for temporo-mandibular joint and Nuss bar insertion, and it can be anticipated that this may become more commonplace in the future. One of the major current deficits for patch testers is standardised guidance on which preparation or preparations to use for suspected titanium allergy. One suggestion is 0.5% titanium sulphate in petrolatum, though experience in at least one centre suggests the use of a battery of titanium salts might be desirable.

Systemic allergic contact dermatitis to palladium, platinum, and titanium: mechanisms, clinical manifestations, prevalence, and therapeutic approaches

Contact dermatitis (CD) is an inflammatory skin disease of eczema that is elicited by chemicals or metal ions that have toxic effects without eliciting a T-cell response (contact elicitation) or by small reactive chemicals that modify proteins and induce innate and adaptive immune responses (contact allergens). The clinical condition is characterized by localized skin rash, pruritus, redness, swelling, and lesions, which are mainly detected by patch tests and lymphocyte stimulation. Heavy metals such as palladium (Pd), platinum (Pt), and titanium (Ti) are ubiquitous in our environment. These heavy metals have shown CD effects as allergic agents. Immunological responses result from the interaction of cytokines and T cells. Occupational metal CD accounts for most cases of work-related cutaneous disorders. In this systematic review, the allergic effects of heavy metals, including Pd, Pt, and Ti, and the mechanisms, clinical manifestations, prevalence, and therapeutic approaches are discussed in detail. Furthermore, the therapeutic approaches introduced to treat CD, including corticosteroids, topical calcineurin inhibitors, systemic immunosuppressive agents, phototherapy, and antihistamines, can be effective in the treatment of these diseases in the future. Ultimately, the insights identified could lead to improved therapeutic and diagnostic pathways.

Magnetic Resonance Safety Evaluation of a Novel Alumina Matrix Composite Ceramic Knee and Image Artifact Comparison to a Metal Knee Implant of Analogous Design

Background

Image artifacts caused by metal knee implants in 1.5T and 3T magnetic resonance imaging (MRI) systems complicate imaging-based diagnosis of the peri-implant region after total knee arthroplasty. Alternatively, metal-free knee prostheses could effectively minimize MRI safety hazards and offer the potential for higher quality diagnostic images.

Methods

A novel knee arthroplasty device composed of BIOLOX delta, an alumina matrix composite (AMC) ceramic, was tested in a magnetic resonance (MR) environment. American Society for Testing and Materials test methods were used for evaluating magnetically induced displacement force, magnetically induced torque, radiofrequency-induced heating, and MR image artifact.

Results

Magnetically induced displacement force and magnetically induced torque results of the AMC ceramic knee indicated that these effects do not pose a known risk in a clinical MR environment, as assessed in a 3T magnetic field. Moreover, minimal radiofrequency-induced heating of the device was observed. In addition, the AMC ceramic knee demonstrated minimal MR image artifacts (7 mm) in comparison to a cobalt-chromium knee (88 mm). The extremely low magnetic susceptibility of AMC (2 ppm) underlines that it is a nonmetallic and nonmagnetic material well suited for the manufacturing of MR Safe orthopaedic implants.

Conclusions

The AMC ceramic knee is a novel metal-free total knee arthroplasty device that can be regarded as MR Safe, as suggested by the absence of hazards from the exposure of this implant to a MR environment. The AMC ceramic knee presents the advantage of being scanned with superior imaging results in 3T MRI systems compared to alternative metal implants on the market.

Difficult Preoperative Diagnosis of Suspected Metal Hypersensitivity in a Case with Early Failure of Bipolar Hemiarthroplasty

Background

Metal hypersensitivity is a rare complication after total hip arthroplasty (THA), and no reliable diagnostic method for metal hypersensitivity to orthopedic metal implants has yet been established. Case report. A 57-year-old woman underwent hemiarthroplasty using a metal implant despite a skin allergy to metal jewelry. Two years after surgery, the patient developed early hemiarthroplasty failure and refractory erythema. Although the patient was clinically suspected to have a hypersensitivity to metal, the preoperative screening test was negative, and patient underwent revision surgery with cemented THA. Postoperatively, the erythema as well as her hip pain disappeared completely.

Conclusion

Patients with clinically suspected metal hypersensitivity should undergo primary and revision total hip arthroplasty using hypoallergenic implants regardless of preoperative screening results.

A comparison of clinical outcomes after total knee arthroplasty (TKA) in patients with preoperative nickel allergy receiving Cobalt-Chromium (CoCr) or Nickel-Free Implant

INTRODUCTION

The role of metal hypersensitivity reactions in total knee arthroplasty (TKA) failure is debated. There is no consensus on whether use of a more expensive nickel-free implant is indicated for patients who have pre-operative nickel allergy. The purpose of this study was to examine the outcome of patients who have pre-operative nickel allergy receiving nickel-free or cobalt chromium (CoCr) implants.

METHODS

This was a retrospective review of 17,798 patients who underwent 20,324 unilateral primary TKAs between 2016 and 2020. Presence of pre-operative nickel allergy was determined (n=282). Patients were divided into 2 cohorts: those receiving (1) nickel-free or (2) CoCr implants. Clinical outcome scores and revision rates were assessed.

RESULTS

243 received a nickel-free implant and 39 received a CoCr implant. There was no significant difference in revision rate between the cohorts. Survivorship free of revision was 94% in the CoCr implant cohort and 98% in the nickel-free implant cohort (P=0.9). When comparing clinical outcome scores between cohorts, there was no difference in preoperative, 6-week or 1-year Knee Osteoarthritis Outcome Score Joint Replacement (KOOS JR.), Visual Analog Scale (VAS), Lower Extremity Activity Scale (LEAS), Patient-Reported Outcomes Measurement Information System (PROMIS), and Veterans RAND 12-item (VR12) scores between cohorts.

CONCLUSIONS

In this retrospective cohort study, there was no difference in revision rates or clinical outcomes in patients who had a nickel allergy undergoing primary TKA with CoCr or nickel-free implants. Further studies are needed to determine if nickel allergy is an independent risk factor for worse TKA outcomes in general.

Hypersensitivity Reactions to Components of Cardiac Implantable Electronic Devices and Their Treatment: A Systematic Review

Background: Hypersensitivity reactions (HSRs) to components of cardiac implantable electronic devices (CIEDs) are rare but difficult to differentiate from device infection. Data on best management strategies of HSRs to CIEDs are lacking. The aims of this systematic review are to summarise the available literature on the aetiology, diagnosis and management of HSR in CIED patients and to provide guidance on best management strategies for these patients. Methods and results: A systematic search for publications on HSR to CIED in PubMed from January 1970 to November 2022 was conducted, resulting in 43 publications reporting on 57 individual cases. The quality of data was low. The mean age was 57 ± 21 years, and 48% of patients were women. The mean time from implant to diagnosis was 29 ± 59 months. Multiple allergens were identified in 11 patients (19%). In 14 cases (25%) no allergen was identified. Blood tests were mostly normal (55%), but eosinophilia (23%), raised inflammatory markers (18%) and raised immunoglobulin E (5%) were also encountered. Symptoms included local reactions, systemic reactions or both in 77%, 21% and 7% of patients, respectively. Explantation of CIED and reimplantation of another CIED coated with a non-allergenic material was usually successful. Use of topical or systemic steroids was associated with high failure rates. Conclusion: Based on the limited data available, the treatment of choice for HSRs to CIEDs is full CIED removal, reassessment of CIED indication and reimplantation of devices coated in non-allergenic materials. Steroids (topical/systemic) have limited efficiency and should not be used. There is an urgent need for further research in this field.

Hypersensitivity and lymphocyte activation after total hip arthroplasty

In the last decades total hip arthroplasty (THA) has become a standard procedure with many benefits but also a few still unsolved complications, which can lead to surgical revision in 19-23% of cases. Thus, aseptic loosening and metal hypersensitivity remain challenges. The phenomenon of wear debris causes chronic inflammation, which produces osteolysis and aseptic loosening. Wear debris promotes osteoclast production and inhibits osteoblasts by secretion of pro-inflammatory cytokines. Micro-abrasions can be induced by abrasive, adhesive and fatigue wear and cause a liberation of metal ions, which lead to another immune response elicited mostly by macrophages. Another reaction in the neocapsule can be a type IV hypersensitivity reaction to various alloys, containing metals such as nickel, cobalt and chromium. Patch testing and the lymphocyte transformation test (LTT) are not the best diagnostic possibilities to exclude a postoperative hypersensitivity reaction, because of the different alignment of the epicutaneous cells compared to the periprosthetic deep tissue. This hypersensitivity reaction is mostly induced by cytokines, which are secreted by macrophages rather than lymphocytes. In cell cultures and in animal studies, multipotent mesenchymal stem cells (MSC) have been shown to play a role in improving initial implant integration, to limit periprosthetic osteolysis and also to reconstitute peri-implant bone stock during implant revision. Thus, MSC might be used in the future to prolong the durability of THA. A better understanding of the interactions between primary chronic inflammation, corrosion, osteolysis and hypersensitivity is mandatory to develop new therapeutic strategies, aiming at the reduction of the incidence of implant failures. In this article the underlying immunological mechanisms to aseptic loosening are presented.

Allergy Testing Has No Correlation with Intraoperative Histopathology from Revision Total Knee Arthroplasty for Implant-Related Metal Allergy

Lymphocyte transformation testing (LTT) is often used in the workup for possible metal allergy after total knee arthroplasty (TKA) but the correlation of this test with other diagnostic metal-allergy findings in patients undergoing revision TKA for suspected metal allergy has not been established. A single-center, single-surgeon cohort of 19 TKAs in which both components were revised for presumed implant-related metal allergy based on history, physical, and LTT testing, to nonnickel-containing implants were retrospectively identified. Histopathologic samples obtained intraoperatively were semiquantitatively analyzed using both the Hospital for Special Surgery (HSS) synovial pathology score and the Campbell aseptic lymphocyte-dominant vasculitis-associated lesion (ALVAL) score. As histopathology control group, we included in the study an additional cohort of 17 patients who received aseptic revision TKA and had no history of reported or tested metal sensitivity. All preoperative LTT results were highly reactive to nickel. However, this did not correlate with local periarticular tissue response in 18 of 19 cases which demonstrated a low HSS synovial score (mean: 3.8 ± 2.8, of a maximum score of 28) and the low Campbell ALVAL scores (mean: 2.5/10 ± 1.3, of a maximum score of 10). There were not any significant differences between the study group (suspected implant-related metal allergy) and the control group (nonsuspected implant-related metal allergy) in regard to (1) the Campbell score and (2) the HSS synovial inflammatory score. Knee Society Clinical Rating System (KSCRS) function score improved significantly after revision (mean postoperative increase: 34.0 ± 17. 2; p < 0.001), as well as mean visual analog scale (VAS) pain (mean postoperative decrease: 33.3 ± 26.4; p < 0.01) score. The short-term survival rate (at mean follow-up of 26.1 months) of this patient cohort was 100%. In this cohort of revised TKA patients with suspected nickel allergy based on clinical presentation and LTT positive results, intraoperative histopathology was essentially normal. However, all patients with suspected nickel allergy showed a significant clinical and functional improvement with excellent short-term survival rates. The clinical significance of a positive LTT needs further study.

Preoperative Metal Patch Testing and Titanium Bar Use Criteria in Nuss Procedure: A 56-Patients' Cohort Study

INTRODUCTION

 Nuss procedure is the main reason for metal implants use by pediatric and thoracic surgeons. There is an ongoing debate on how to avoid allergic complications. Herein we describe our 8-year experience with systematic preoperative metal patch testing and our selective titanium bar use in Nuss procedure.

MATERIALS AND METHODS

 This is a single center retrospective observational cohort study of patients who underwent the Nuss procedure from 2013 to 2020. Preoperative metal patch testing was done in all cases. Criteria for titanium bar utilization were: a positive test for a major component of the stainless-steel bar; or a positive metal patch test and a positive history of atopy, food or metal allergy, or previous allergic reaction to an implant or device.

RESULTS

 In total, 56 patients were included. Most were male (91.1%) with a median age of 15.0 (13.0-22.0) years old. 19.6% had a positive preoperative metal patch test and 54.5% of these had no personal history of atopy. Stainless-steel bars were used in 27.3% of those patients and titanium bars were used in 72.7%. One patient had a documented minor allergy reaction. None of the 56 patients required early bar removal.

CONCLUSION

 Our study suggests that routine preoperative allergy testing and a judicious use of titanium bar are safe and avoid metal allergic complications.

The effect of Nickel hypersensitivity on the outcome of total knee arthroplasty and the value of skin patch testing: a systematic review

Background

To assess the Nickel sensitizing potential of total knee arthroplasty (TKA), explore the relationship between hypersensitivity and clinical outcomes, and evaluate the utility of skin patch testing pre- and/or postoperatively.

Materials and methods

A literature search was performed through EMBASE, Medline and PubMed databases. Articles were screened independently by two investigators. The level of evidence of studies was assessed using the Oxford Centre for Evidence-Based Medicine Criteria and the quality evaluated using the Methodological Index for Non-randomized Studies and Cochrane risk-of-bias tools.

Results

Twenty studies met the eligibility criteria, reporting on 1354 knee arthroplasties. Studies included patients undergoing primary or revision TKA, pre- and/or postoperatively, and used patch testing to identify Nickel hypersensitivity. Prevalence of Nickel hypersensitivity ranged from 0% to 87.5%. One study compared the prevalence of Nickel hypersensitivity in the same patient group before and after surgery and noted newly positive patch test reactions in three patients (4.2%). Three studies reported lower prevalence of Nickel hypersensitivity in postoperative patients compared to preoperative ones. Seven studies suggested that hypersensitivity might cause adverse clinical outcomes, but six did not support any relationship. Seven studies recommended preoperative patch testing in patients with history of metal allergy, and nine concluded that testing may be valuable postoperatively.

Conclusions

Patients undergoing TKA with no prior history of metal hypersensitivity do not seem to be at an increased risk of developing Nickel hypersensitivity, and there is conflicting evidence that patients with pre-existing hypersensitivity are more likely to experience adverse outcomes. Patch testing remains the most commonly used method for diagnosing hypersensitivity, and evidence suggests preoperative testing in patients with history of metal allergy to aid prosthesis selection, and postoperatively in patients with suspected hypersensitivity once common causes of implant failure have been excluded, since revision with hypoallergenic implants may alleviate symptoms.

Beneficial effect of a zirconium-nitride-coated implant in total knee arthroplasty revision for suspected metal hypersensitivity

INTRODUCTION

Revision of total knee arthroplasty (rTKA) for suspicion of metal hypersensitivity (MHS) may require hypoallergenic implants. Results for coated implants have not been reported. The aim of the present study was to assess short-term results and survival of rTKA for MHS using a multilayer implant coating.

HYPOTHESIS

Multilayer implant coating improves functional results in rTKA, with survival comparable to primary coated implants.

MATERIAL AND METHODS

A single-center retrospective observational study included 28 patients (30 knees) undergoing rTKA for MHS using a coated implant between May 2011 and November 2016. Exclusion criteria comprised implant malpositioning and history of infection in the affected knee. Clinical and radiological results were assessed on the International Knee Society (IKS) and SF-36 functional scores and Ewald radiological score. Survival was calculated on Kaplan-Meier estimation.

RESULTS

Mean follow-up was 3.8 years. Mean IKS score increased by 40.2 points (40%) [range, 28.1-52.3] (p<0.05). Mean range of motion increased by 17° [range, 9.5-24.5°] (p<0.05). Mean physical and mental SF-36 components were respectively 44.7 and 46.1. Survivorship was 93%.

DISCUSSION

There was significant functional improvement after rTKA for MHS. There were no short-term complications related to the zirconium nitrate coating. However, studies with longer follow-up will be needed for confirmation.

LEVEL OF EVIDENCE

IV; retrospective study.

Diagnostic tests for titanium hypersensitivity in implant dentistry: a systematic review of the literature

PURPOSE

There are rising concerns about titanium hypersensitivity reaction regarding dental endosseous implants. This review aims to summarize and compare the validity and reliability of the available dermatological and laboratory diagnostic tests regarding titanium hypersensitivity. The following PICO design was used: In Patients with titanium dental implants (P) does epicutaneous testing (ECT) (I), compared to lymphocyte transformation test (LTT) or Memory Lymphocyte Immunostimulation Assay (MELISA) (C) detect hypersensitivity reactions (O)? A literature search was performed including all studies dealing with this topic. Studies regarding orthopedic implants were excluded.

METHODS

Three databases (MEDLINE PubMed, Cochrane Library, SciELO) were screened for suitable studies and an additional manual search was also performed. Literature regarding hypersensitivity reactions in orthopedic implants, hypersensitivity reactions regarding implants not related to dental or maxillofacial surgery, animal studies and in vitro studies were excluded. A quality assessment of all selected full-text articles was performed. Randomized, controlled trials were evaluated with the Cochrane Risk of Bias Tool I. Cohort studies were assessed according to the New Castle-Ottawa Scale and case series according to Moga et al. (Development of a quality appraisal tool for case series studies using a modified Delphi technique. 2012).

RESULTS

10 studies were included in the quantitative synthesis and available for the endpoint diagnostics of intolerance reactions to titanium dental implants: 2 clinical studies, 7 cohort studies and 1 case series. The potential for bias (internal validity) for these studies was overall rated as high.

CONCLUSIONS

The study of the available literature regarding ECT and MELISA or LTT in patients with suspected titanium hypersensitivity showed inconsistent results in terms of reliability and validity and thus, those tests should be regarded cautiously. There is strong evidence that titanium hypersensitivity in dental implants is associated with innate immunity: unspecific pro-inflammatory responses due to particle induced hyperreactivity of macrophages or toxicological responses especially towards nanoparticles rather than activation of the adaptive immune system. Therefore, tests detecting allergies do not seem expedient and inflammatory clinical signs should be regarded as leading parameters.

Contact allergens for the allergist

OBJECTIVE

The objective of this article is to provide an overview and describe typically encountered skin contact allergens implicated in allergic contact dermatitis (ACD).

DATA SOURCES

Published literature obtained through textbooks, online PubMed, and Google Scholar database searches, author photography, and adapted figures were used.

STUDY SELECTIONS

Studies on the evaluation of ACD and specific skin contact allergens were selected, with a focus on original research articles and clinical reviews.

RESULTS

Major classifications of common contact allergens include the following: (1) fragrances, (2) preservatives, (3) excipients, (4) rubber chemicals, (5) textile dyes, (6) topical medications, and (6) metals and other biomedical device components. The dermatitis distribution can aid in identifying the suspected contact allergen culprit. Certain contact allergens have features that are important to consider in the patch testing (PT) interpretation; these include possible irritant reactions, false-negative reactions or missed detection, and delayed reactions. Fragrances, preservatives, and excipients are culprits in personal products and facial or neck dermatitis. Patch testing with fragrances, preservatives, and patient-supplied products requires careful interpretation. Hand or foot dermatitis may be attributed to rubber chemicals or textile dyes. The management of topical corticosteroid contact allergy is guided on the basis of structural group classifications. Metal sensitization has been associated with dermatitis or biomedical device complications.

CONCLUSION

Each skin contact allergen has unique characteristics with regard to the dermatitis clinical presentation and potential PT nuances. These features are critical to recognize in the evaluation of ACD and PT interpretation and clinical relevance, leading to an accurate diagnosis.

[Allergic reactions to bioimplants]

BACKGROUND

Bioimplants are used in a variety of ways in otorhinolaryngology, most commonly in facial reconstructive surgery, cochlear implants (CI), bone-anchored hearing aids, and partial/total ossicular replacement prostheses (PORP/TORP), but also for tympanic drainage, laryngeal cannula, voice prostheses after laryngectomy, etc., and in otorhinolaryngology-related procedures as dental implants in dentistry.

METHODS

A literature search was performed to analyze the immunology of allergic reactions to bioimplants and to determine the available evidence by searching Medline, PubMed, and national and international study and guideline registries and the Cochrane Library. Human studies published in the period up to and including 12/2021 were considered.

RESULTS

Based on the international literature and previous experience, a review of allergies to bioimplants in otolaryngology is presented.

CONCLUSION

Otorhinolaryngologists should always consider the possibility of allergic reactions when inserting allogeneic materials, particularly, but not only, when using bioimplants.

Metal Hypersensitivity or Missed Periprosthetic Joint Infection? A Critical Review

The World Association Against Infection in Orthopedics And Trauma (W.A.I.O.T.) Study Group on Bone And Joint Infection Definitions Metal hypersensitivity (MHS) has been investigated by several authors as a possible reason for painful total joint arthroplasty, with controversial results. Periprosthetic joint infection (PJI) is another possible source of unexplained pain and implant failure that may be difficult to diagnose if not properly investigated. We performed this critical review to assess whether the current literature on MHS includes an adequate diagnostic workup to discern metal allergy from PJI. The results of this review highlight the importance of assessing patients for PJI before making a diagnosis of MHS and emphasize that the methods currently used to exclude PJI are substantially inadequate. Therefore, well-designed clinical trials with adequate diagnostic protocols and definitions of PJI that can differentiate MHS from low-grade PJI are needed. [Orthopedics. 2022;45(2):e73-e78.].

Epicutaneous Patch Testing in Type IV Allergy Diagnostics: State of the Art and Best Practice Recommendations

This chapter summarises all relevant aspects of patch testing, closely following recommendations outlined in a recent European, and a German S3 guideline on diagnostic patch testing with contact allergens and medicinal products (drugs). Patch testing is indicated in patients suspected of suffering, or having been suffering, from delayed-type hypersensitivity leading to allergic contact dermatitis or other skin and mucosal diseases. Sections of this chapter include detailed indications, reasons for possibly postponing the test, considerations on choosing haptens (contact allergens) to test, various aspects of the application of patch test allergen preparations (storage, dosing) and of testing with individual materials provided by the patients. Special aspects of patch testing in cutaneous adverse drug reactions, children, or occupational contact dermatitis are outlined. Supplemental test methods, notably the repeated open application test, are briefly described. Finally, the final evaluation in terms of assessment of clinical relevance of reactions and patient counselling are outlined.

Metal allergy in primary and revision total knee arthroplasty : a scoping review and evidence-based practical approach

Aims

Metal allergy in knee arthroplasty patients is a controversial topic. We aimed to conduct a scoping review to clarify the management of metal allergy in primary and revision total knee arthroplasty (TKA).

Methods

Studies were identified by searching electronic databases: Cochrane Central Register of Controlled Trials, Ovid MEDLINE, and Embase, from their inception to November 2020, for studies evaluating TKA patients with metal hypersensitivity/allergy. All studies reporting on diagnosing or managing metal hypersensitivity in TKA were included. Data were extracted and summarized based on study design, study population, interventions and outcomes. A practical guide is then formulated based on the available evidence.

Results

We included 38 heterogeneous studies (two randomized controlled trials, six comparative studies, 19 case series, and 11 case reports). The evidence indicates that metal hypersensitivity is a rare complication with some histopathological features leading to pain and dissatisfaction with no reliable screening tests preoperatively. Hypoallergenic implants are viable alternatives for patients with self-reported/confirmed metal hypersensitivity if declared preoperatively; however, concerns remain over their long-term outcomes with ceramic implants outperforming titanium nitride-coated implants and informed consent is paramount. For patients presenting with painful TKA, metal hypersensitivity is a diagnosis of exclusion where patch skin testing, lymphocyte transformation test, and synovial biopsies are useful adjuncts before revision surgery is undertaken to hypoallergenic implants with shared decision-making and informed consent.

Conclusion

Using the limited available evidence in the literature, we provide a practical approach to metal hypersensitivity in TKA patients. Future national/registry-based studies are needed to identify the scale of metal hypersensitivity, agreed diagnostic criteria, and management strategies.

Cite this article: Bone Jt Open 2021;2(10):785–795.

Contact dermatitis

Contact dermatitis (CD) is among the most common inflammatory dermatological conditions and includes allergic CD, photoallergic CD, irritant CD, photoirritant CD (also called phototoxic CD) and protein CD. Occupational CD can be of any type and is the most prevalent occupational skin disease. Each CD type is characterized by different immunological mechanisms and/or requisite exposures. Clinical manifestations of CD vary widely and multiple subtypes may occur simultaneously. The diagnosis relies on clinical presentation, thorough exposure assessment and evaluation with techniques such as patch testing and skin-prick testing. Management is based on patient education, avoidance strategies of specific substances, and topical treatments; in severe or recalcitrant cases, which can negatively affect the quality of life of patients, systemic medications may be needed.

Sensitization to Implant Components Is Associated with Joint Replacement Failure: Identification and Revision to Nonallergenic Hardware Improves Outcomes

BACKGROUND

Over 90% of one million annual US joint replacements are highly successful. Nonetheless, 10% do poorly owing to infection or mechanical issues. Many implant components are sensitizers, and sensitization could also contribute to implant failure.

OBJECTIVE

To determine the prevalence of implant sensitization in joint failure patients, their clinical characteristics, and implant revision outcomes. We hypothesized that sensitized patients would improve when revised with nonallergenic materials.

METHODS

We prospectively enrolled 105 joint failure patients referred by orthopedic surgeons who had already excluded infection or mechanical causes. Patients provided informed consent, completed a history and physical examination, patch testing to metals and bone cement, and a nickel lymphocyte proliferation test. A study coordinator was able to contact 64% of patients (n = 67) 9 to 12 months later to evaluate outcomes.

RESULTS

A total of 59% were sensitized to an implant component: 32% to metal and 37% to bone cement. The nickel lymphocyte proliferation test was 60% sensitive and 96% specific in diagnosing nickel sensitization. Most sensitized subjects reported no or uncertain histories of reactions to a specific material. Implant sensitized patients were younger and reported previous eczema, joint itching, and implant loosening. By 9 to 12 months later, most patients with a revised implant (revised) described significant improvement (16 of 22 revised for sensitization [P = .0003] vs 9 of 13 revised without sensitization [P = .047]) compared with patients without implant revision). All revised patients with sensitization used components to which they were not sensitized. Pain (P = .001), swelling (P = .035), and instability (P = .006) were significantly reduced in the revised sensitized group.

CONCLUSIONS

Sensitization to implant components is an important cause of unexplained joint replacement failure. Joint revisions based on sensitization information resulted in significant improvements.

Metal allergy after the Nuss procedure for pectus excavatum: a review

Minimally invasive repair of pectus excavatum (MIRPE) technique (the Nuss procedure) is a minimally-invasive method that is commonly used in the treatment of pectus excavatum. An allergic reaction to the metal alloy bar that is implanted in the thorax during the procedure is a reported complication. We briefly review current literature concerning epidemiology, mechanisms and research results of allergic reactions after Nuss bar implantation. This allergic reaction occurs in approximately 2.7% of patients and is caused by metals used in the medical implant. The most common symptoms include fever and skin lesions such as allergic dermatitis. Elevated levels of C-reactive protein is a frequent finding in laboratory tests. In order to minimize the risk of such complications, taking a detailed allergy-based medical history and conducting allergy tests, i.e. patch test are required. Allergic reactions can be managed with conservative treatment such as general or topical glucocorticosteroid therapy and antihistamine agents. Severe allergic reactions can be addressed by implant revision, replacement of the steel bar with a titanium substitute or removal of the stabilization at all. Although the risk of an allergic reaction to titanium is smaller it still exists, the titanium substitute is not routinely used due to its higher cost and lesser plasticity which has a negative impact on matching a stabilizing bar during the surgery. Surgeons treating pectus excavatum should remember about the possible allergic reactions after implantation of the metal bar and be familiar with methods of diagnosis and treatment of those complications.

Titanium Niobium Nitride Mobile-Bearing Unicompartmental Knee Arthroplasty Results in Good to Excellent Clinical and Radiographic Outcomes in Metal Allergy Patients With Medial Knee Osteoarthritis

BACKGROUND

The main purpose of the present study was to analyze the clinical and radiological outcomes of patients with positive skin patch tests who underwent medial mobile-bearing titanium niobium nitride unicompartmental knee arthroplasty (UKA) during a mid-term follow-up.

METHODS

Thirty-seven patients with positive skin patch tests were included in this prospective study. The clinical evaluation consisted of Oxford Knee Score and Knee Society Score (KSS) reports. Each patient was clinically evaluated the day before surgery (T₀) as well as at T₁ (11.9 ± 1.3 months) and during the final follow-up T₂ (67.2 ± 19.1 months). The positioning of the UKA was evaluated during the final follow-up using standardized radiographs (T₂: 67.2 ± 19.1 months).

RESULTS

Oxford and KSS ranged from a respective mean preoperative value of 23.0 ± 2.7 and 51.5 ± 5.0 to 42.1 ± 1.7 and 87.6 ± 2.2, respectively, at T₁ (P < .001) and to the final values of 45.0 ± 1.9 and 91.9 ± 3.4, respectively, at T₂ (P < .001 both vs T₁ and T₂). At T₂, the mean femoral angle was 7.0° ± 4.5°, mean tibial angle was 3.0° ± 2.1°, and mean tibial slope was 5.1° ± 3.2°. A significant difference was found between KSS and Oxford with ANOVA for repeated measures over time (P < .001). The Oxford and KSS scores showed significant improvements during each follow-up. No complications were found, and not a single patient required a revision surgery during the follow-up period.

CONCLUSION

The hypoallergenic titanium niobium nitride mobile-bearing UKA showed comparable results to standard CoCr UKA regardless of the gender, age, BMI, and implant size of metal allergy patients with medial knee osteoarthritis. Careful patient selection processes and accurate medical histories played key roles in the choice of hypersensitivity-friendly implants.

Self-reported metal hypersensitivity in patients undergoing unicondylar knee arthroplasty

OBJECTIVES

There is ongoing discussion about arthroplasty surgery of patients with metal hypersensitivity. The aim of this study was to compare the functional outcomes and eosinophil counts of unicondylar knee arthroplasty (UKA) patients with and without a history of metal hypersensitivity.

METHODS

A retrospective review was made of the medical records of 148 extremities of 140 consecutive patients who underwent primary UKA between January 2016 and December 2017. The patients who met the inclusion criteria were screened for history of metal hypersensitivity using a questionnaire. The functional outcomes of patients and eosinophil levels were evaluated immediately before and at 6 weeks after surgery.

RESULTS

The mean follow-up period was 37 months (range, 18-48 months). Of the total 128 patients, 13 (10.2%) reported a history of metal hypersensitivity before the operation. There was no statistically significant difference between patients with or without a history of metal hypersensitivity in respect of the functional outcomes or eosinophil counts (p > 0.05).

CONCLUSIONS

The results of this study showed that the functional outcomes of patients who underwent UKA using a standard alloy did not change between the groups who reported having or not having a history of metal hypersensitivity. Although the study also showed that the eosinophil counts decreased after surgery compared to the preoperative counts, there was no statistical relationship between the eosinophil count and functional outcomes or metal hypersensitivity history.

Early Outcomes of an Alternative Bearing Surface in Primary Total Knee Arthroplasty in Patients with Self-reported Metal Allergy

Background

Most implants for total knee arthroplasty (TKA) are comprised of alloys that contain nickel. Controversy exists whether metal allergies produce negative effects and affect clinical outcomes. The purpose of this study was to retrospectively review a minimum 2-year follow-up with an ion-bombarded titanium TKA implant in patients with reported metal sensitivity.

Methods

A retrospective review of patients who underwent primary TKA with the ion-bombarded titanium Vanguard (Zimmer Biomet, Warsaw, IN) implant with 2-year minimum follow-up was performed from 2008 through 2017. The query revealed 346 patients (451 knees) with minimum 2-year follow-up. The mean age was 64.7 years, the mean body mass index was 35.1 kg/m², and 95% of patients were women.

Results

The mean follow-up was 4.6 years. The mean range of motion improved from 109° to 112° (P = .03), University of California Los Angeles activity scale from 4.1 to 5.1 (P < .001), Knee Society Clinical scores from 36 to 89 (P < .001), and Knee Society Functional scores from 48 to 73 (P < .001). There were 5 (1.1%) revisions: 2 infections (2-staged exchange), 1 tibial revision for aseptic loosening after a fall, and 2 bearing exchanges for instability. Other surgeries were open reduction internal fixation of periprosthetic fracture, 1 arthroscopic release of snapping popliteus, and 4 local wound incision and debridement (2 superficial infections and 2 nonhealing wounds). Manipulation under anesthesia was required in 27 (6%) patients.

Conclusions

These early results are encouraging for the use of alternative metal titanium alloy implants in metal-sensitive patients undergoing primary TKA. At 4.6 years of mean follow-up, patients had substantial improvement in the range of motion and clinical outcomes with a low frequency of revision.

Prevalence of metal hypersensitivity in patients with shoulder pathologies

BACKGROUND

To date, medical history and dedicated questionnaires are the fastest and easiest way to assess risks of joint metal hypersensitivity. No published studies determined the overall prevalence of hypersensitivity to metals in patients with shoulder pathologies. The purpose of this study was therefore to estimate the prevalence of metal hypersensitivity reported by patients with shoulder pathologies, and to identify patients at risk of joint metal hypersensitivity based on a dedicated questionnaire.

METHODS

The authors prospectively asked all adult patients consulting for shoulder pathologies between September 2018 and February 2019 at 10 centers to fill in a form. The main outcome was "reported hypersensitivity to metals," comprising belt buckles, coins, earrings, fancy jewelry, keys, leather, metallic buttons, piercings, spectacles, watch bracelets, or zips.

RESULTS

A total of 3217 patients agreed to fill in the survey, aged 55 ± 16 (range, 18-101) with equal proportions of men (51%) and women (49%), and a majority of patients consulting for cuff pathology (55%). A total of 891 (28%) patients had professions considered at risk for metal hypersensitivity. The most frequently reported metal hypersensitivities were fancy jewelry (15%), earrings (13%), and watch bracelets (9%). A total of 629 (20%) patients, of which the vast majority were women, reported hypersensitivity to 1 or more metals.

CONCLUSIONS

This survey of 3217 patients identified 20% who reported metal hypersensitivities, though only 2.2% had done patch tests. Matching profiles of those with positive patch tests to those with no patch tests revealed that 9.4% of the total cohort had similar sex and self-reported metal hypersensitivities. Factors associated with a positive patch test were female sex, self-reported cutaneous allergy, and self-reported metal hypersensitivity. The clinical applicability of these estimates remains uncertain as there is insufficient evidence that allergy to metal implants can be predicted by questionnaires or patch tests.

S3 guidelines: Epicutaneous patch testing with contact allergens and drugs - Short version, Part 1

Epicutaneous patch testing is the diagnostic standard for the detection of allergic contact dermatitis. The present guidelines are aimed at residents and board-certified physicians in the fields of dermatology and allergology as well as other medical specialties involved in establishing the indication for patch testing and its execution in patients with contact dermatitis and other forms of delayed-type hypersensitivity. The target audience also includes other health care providers and insurance funds. Based on a systematic literature search and a formal consensus process (S3), the guidelines were developed by dermatologists in collaboration with pediatricians, occupational medicine physicians, nursing staff as well as patient representatives. The systematic methodological approach and appraisal of evidence upon which the recommendations are based are outlined in a separate method report that also contains evidence tables. The guidelines address general aspects of patch testing as well as medicolegal issues. The recommendations given relate to topics such as the indication for patch testing, informed patient consent, as well as the choice of test substances, test chambers and test site, duration of exposure, reading times and interpretation of test reactions. Furthermore, recommendations are provided with respect to endogenous and exogenous factors, specific patient groups (children, pregnant women, immunosuppressed individuals) as well as possible risks and adverse events associated with patch testing using contact allergens. Note: This publication is part 1 of the short version of the S3 guidelines for "Epicutaneous patch testing using contact allergens and drugs" (registry no. 013 - 018; date: March 20, 2019; valid until December 31, 2021). Part 2 of the short version will be published in the next issue. The long version of these guidelines can be accessed at www.awmf.org. The method report is available as online publication (https://www.awmf.org/leitlinien/detail/ll/013-018.html) and contains the evidence tables in its appendix.

Symptoms of titanium and nickel allergic sensitization in orthodontic treatment

Aim

The study aimed to evaluate to which extent self-reported symptomatology, age, and sex are predictors of titanium and nickel allergic sensitization in patients in treatment with fixed orthodontic appliances.

Methods

The study analyzed 228 subjects aged 11–45 years (median 18, interquartile range 16–22); 68% of them were females, and 52% were adolescents. The allergic sensitization testing included epicutaneous patch test to titanium, titanium dioxide, titanium oxalate, titanium nitride, and nickel sulfate. The questionnaire on symptoms potentially linked to titanium and nickel sensitization was used.

Results

Prevalence of the allergic sensitization to titanium in patients undergoing orthodontic treatment was 4% (2% only to titanium without nickel) while to nickel 14% (12% nickel without titanium). Hypersensitivity to both metals at the same time was present in 2% of subjects. Sensitization to nickel was more common in females than in males (17 vs. 8%) and much more common in adults than in adolescents with small effect size (20 vs. 8%; p = 0.013). Sensitization to titanium was more common in females than in males (6 vs. 1%) with no difference in age. Multiple logistic regression analysis revealed that adult age increases the odds for being sensitized to nickel for 2.4 × (95% CI 1.1–5.6; p = 0.044) while watery eyes for 3.7 × (95% CI 1.2–11.1; p = 0.022). None of the symptoms were significant predictors of titanium sensitization.

Conclusion

Allergic sensitization to titanium and nickel are not very frequent in orthodontic patients, and self-reported symptomatology is a weak predictor of those sensitizations.

Patch Testing With an Extended Metal Allergen Series at the Massachusetts General Hospital (2006-2017)

BACKGROUND

Reports of patch test data with an extended metal series that includes rare metals are limited.

OBJECTIVE

The aims of the study were to analyze and report patch testing results from an extended metal series, examine associations with sex and age, and highlight concomitant metal reactions.

METHODS

This study is a retrospective review of 150 patients referred for suspected metal allergy from January 1, 2007, to December 31, 2016.

RESULTS

The most common indications for evaluation referral were those having symptoms after implantation of a metal device (55.3%) and those with a history and concern of metal allergy before implantation of a metal device (22.0%). One or more positive patch test reactions were observed in 87 patients (58.0%). Metals with the highest frequencies were nickel sulfate 2.5% (26.2%), gold sodium thiosulfate 0.5% (23.0%), gold sodium thiosulfate 2.0% (20.7%), palladium chloride 2.0% (19.6%), cobalt chloride 1.0% (12.0%), and manganese chloride 2.0% (10.1%). Of the 45 metals tested, 15 caused no patch test reactions. Female patients were more likely to be sensitized to nickel, gold, and palladium (P < 0.05). Younger patients (≤40 years) had higher reaction rates to nickel, mercury, palladium, and cobalt. Concomitant reactions of the top metals (nickel, palladium, gold, and cobalt) were statistically associated bidirectionally (P < 0.05), except for cobalt and gold.

CONCLUSIONS

Allergy to metals, including those not included in standard series, may be more prevalent than previously suspected. Results may help guide future testing for suspected metal allergy, although future studies are warranted.

Metallic allergy requiring removal of iliac stent: report of a case

BACKGROUND

The use of metallic stents, which are predominantly composed of nickel, in the treatment of patients with nickel allergy has not been well studied.

CASE PRESENTATION

A patient who suffered from contact dermatitis due to implantation of an iliac stent was successfully treated by removing the stent that caused nickel allergy. The patient has exhibited no symptoms of claudication or severe pruritic rash in the 2-year follow-up period after iliac stent removal.

CONCLUSIONS

We herein report a case of nickel allergy in which a metallic iliac stent that was predominantly composed of nickel was removed. The patient showed a marked recovery from her contact dermatitis. In cases of suspected metallic allergy, it is necessary to consider revascularization without using a metal device.

Rare Systemic Response to Titanium Spinal Fusion Implant: Case Report

Neurosurgical patients with titanium spinal implant hypersensitivity can be difficult to diagnosis due to its rarity. Suspicion for titanium allergy is generally localized to the hardware site and may initially be thought to be an infectious process. Patients who report anorexia and fatigue over a long duration after the initial post-operative period may be diagnosed with depression rather than a systemic response to spinal metallic instrumentation. To our knowledge, a systemic titanium hypersensitivity reaction to spinal fixation devices has not been reported in the literature. We offer this report to give spine surgeons additional insight into suspected systemic titanium hypersensitivity symptoms which, if remain unidentified, can severely impair patient outcomes. A 67-year-old female with an unreported nickel allergy developed severe debilitating anorexia and fatigue one month post operatively, secondary to minimally invasive thoracic spinal fixation for T11 burst fracture with disruption of posterior elements. Over a two year period, weight loss reached approximately 25 kilograms with loss of muscle mass and subcutaneous tissue surrounding the spinal implants. The screws and rods were removed to avoid skin erosion. Upon hardware removal, the patient had rapid weight gain, improved stamina and generalized sense of well-being. We recommend the removal of spinal hardware in patients with suspected systemic titanium hypersensitivity reaction.

The effect of patient-reported metal allergies on the outcomes of shoulder arthroplasty

BACKGROUND

Although literature exists regarding hip and knee arthroplasty outcomes in patients with skin allergy to metals, there is minimal information about skin allergy implications on shoulder arthroplasty outcomes. The purpose of this study was to determine the results, complications, and failure rate among patients with a self-reported metal allergy undergoing shoulder arthroplasty.

METHODS

Fifty-two shoulder arthroplasties were performed at our Institution in 43 patients with self-reported metal allergies. Forty primary and 12 revision shoulder arthroplasties were performed using anatomic (30) and reverse (22) components. Retrospective chart review was performed to determine metal allergy history, implant composition, pain, motion, and complications. Radiographs were reviewed to determine mechanical failure rates. Average follow-up time was 65 months.

RESULTS

Allergies reported included nickel (37), cobalt chrome (4), copper (2), zinc (1), titanium (1), gold (1), and nonspecific metal allergy (8); 8 patients reported multiple metal allergies. All components implanted in patients with nickel allergies contained nickel. At most recent follow-up, pain was rated as none or mild in 88% of shoulders. Active elevation improved from 80° to 141° and external rotation from 24° to 52°. Two revisions were performed for glenoid loosening (3.8%); both were revision cases with substantial glenoid bone loss. One patient with mild pain had a radiographically loose glenoid component 12 years after anatomic shoulder arthroplasty.

CONCLUSION

Results from this study suggest that shoulder arthroplasty in patients with self-reported metal allergy provides satisfactory pain relief and improved range of motion with low revision rates.