The role of metal sensitivity or allergy in causing persistent symptoms or failure and need for a revision of a total joint replacement has been the topic of debate and controversy for decades. There was renewed interest in this area with the rise of metal-on-metal hip arthroplasty and the advent of adverse local tissue reactions. This led to an increase in metal ion testing as well as metal sensitivity testing. With the decline of the use of metal-on-metal hip components, this is now mostly an issue in knee arthroplasty. It is well known that a substantial percentage of patients have persistent symptoms following knee replacement. What remains in question is whether allergy to metal or other materials such as PMMA may be a contributing factor. It is accepted that the incidence of positive skin patch tests is higher in symptomatic failed joint replacements. Nickel sensitivity is most common as a positive skin test with up to 15% of patients demonstrating this followed by chromium and cobalt. A recent review by Lachiewicz et al. concluded that there was insufficient evidence to recommend routine or widespread cutaneous or in vitro hypersensitivity testing before primary TKA, that there is no evidence-based rationale to recommend a routine metal allergy screening questionnaire, that there is only anecdotal support for Ni-free implants, and that local dermatitis should be treated with topical steroids. In another article, routine screening for metal allergy was not recommended, however, selective screening for history of sensitivity or unexplained pain or early loosening was suggested. Other experts have recommended a role for utilizing a commercially available alternative to components containing nickel or cobalt in patients thought to be hypersensitive. A recent study, however, concluded that there was no difference in complications, revisions, or reoperations among patients who tested positive with patch testing whether they were treated with standard components or nickel free components. Likewise, a consensus panel published results from the United Kingdom in which cobalt chrome implants were recommended regardless of the patients metal allergy status. Patient perception is important, however, and among patients who report multiple allergies of any kind, a higher percentage are likely to be dissatisfied with their knee replacement. Of more importance are those reporting a specific allergy to metal are substantially more likely to express some dissatisfaction with their components. Metal allergy as a cause of chronic pain and/or early failure of joint replacement is rare if it exists at all. It is always a diagnosis of exclusion. Patients who think they are allergic are probably more likely to be more symptomatic following joint replacement. Whether or not to use a nickel free or hypoallergenic component in such patients remains an area of controversy

Total joint arthroplasty has proven to be efficient to relieve pain and regain mobility. In fact, most patients undergoing a total knee arthroplasty (TKA) are satisfied with their surgery (80 to 90%), yet 4 to 7% still complain of unexplainable pain and stiffness. Several authors have proposed that reactivity to the implant could explain this phenomenon. Still, no strong evidence supports this theory as of today. We aimed to determine the prevalence of metal and cement hypersensitivity in a cohort of patients with unexplained pain and stiffness after TKA. We retrieved data for a group of patients presenting unexplained pain and stiffness. We excluded all other potential known causes of pain. All patients were tested with a Lymphocyte Transformation Test from whole blood taps. We analysed data of hypersensitivity to metals (alloy particles of titanium and cobalt, aluminum, cobalt, nickel, zirconium, vanadium, molybdenum, cobalt, chromium and iron) and PMMA cement (bone cement monomer and particles). Fifty-three patients underwent a LTT for unexplained pain and stiffness after total knee arthroplasty between May 2012 and May 2015. The cohort consisted of 26 men and 27 women with a mean age of 66.3(±8.0) years. Six patients had no hypersensitivity (11.3%), leaving 88.7% of the cohort with hypersensitivity to metal and/or cement. Almost half the cohort of patients tested for PMMA was hypersensitive to cement (44.0%). The most common metal hypersensitivity was nickel (69.8%). Twelve patients presented sensitivity to only one metal (22.6%), whereas 35 patients were hypersensitive to more than one metal (66.0%). Eleven patients had revision surgery with a hypoallergenic prosthesis. Patients reported a significant diminution of pain as well as better knee function compared to preoperative status as early as 6 weeks postop, although some reported residual stiffness. The results of this study suggest that metal and/or cement hypersensitivity could play a role in cases of total knee arthroplasty with unexplained pain and stiffness. Randomised controlled clinical trials on the subject will be initiated by our team to further investigate this phenomenon

Introduction. Adverse Local Tissue Reactions (ALTR) have been reported in association with both wear and corrosion. Tissue reactions have been reported in association with corrosion at CoCr head-CoCr neck, CoCr head-TiAl6V4 neck, and CoCr modular neck on beta-titanium (TMZF) stem junctions. The current abstract reports on 3 cases of ALTR in association with CoCr modular necks on convention titanium (TiAl6V4) stem junctions. Case 1. A 67 year old male (87 kg, 1.73 m, BMI 29.1) presented with new onset hip irritation 11 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 95, CRP = 5, Cr level = 1.0, Co level = 4.1, leukocyte transformation testing = highly reactive to nickel. Hip aspiration was culture negative with 11,250 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the greater trochanter. Case 2. A 52 year old male (89 kg, 1.83 m, BMI 26.5) presented with new onset hip irritation 30 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 7, CRP = 5.4, Cr level = 2.1, Co level = 4.8, leukocyte transformation testing = reactive to nickel. Hip aspiration was culture negative with 3995 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the iliopsoas. Case 3. A 52 year old male (104 kg, 1.85 m, BMI 30.1) presented with new onset hip irritation 26 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 33, CRP = 34.9, Cr level = 1.0, Co level = 3.7, leukocyte transformation testing = no reactivity to any of the biomaterials. Hip aspiration was culture negative with 3,780 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the iliopsoas. Discussion. All three of these patients are scheduled for revision surgery. All three had ceramic-ceramic bearings. We have experience with 1029 ceramic-ceramic THA with fixed neck conventional titanium and modular titanium neck implants with minimum 2 yr f/u and have never diagnosed an adverse reaction in any of these patients. It is possible that corrosion at the CoCr neck on TiAl6V4 stem junction is the root cause of these reactions. Although the incidence of diagnosed reactions is roughly 1%, it appears that the use of CoCr at any junction under significant mechanical stress can result in adverse local tissue reaction and therefore should either be avoided or used with great caution and compelling indications

It is estimated that 15 % of the population is allergic to metal, most commonly to Nickel, which is a common component of the alloys in most knee and hip arthroplasties. It would therefore be expected that allergy to metal is a frequent form of implant failure – but very little is reported in the literature. With the recent concerns about metal-on-metal bearings and metal ion issues, there has been renewed interest in metal allergy – with the Australian Joint Registry 2010 reporting it as a causative factor in 7 % of Hip Resurfacing revisions. With over 200 BHR and 571 ASR Hip Resurfacing arthroplasties in my series from 2001, I have identified only 1 patient with implant failure due to metal allergy. In 2010 two Total Knee Arthroplasty patients presented with pain and strongly positive Melisa allergy tests – these patients were revised to Titanium coated implants resulting in a complete relief of symptoms. This paper will analyse the problem of metal sensitivity, the investigation and management of the allergic patient who has, or requires, joint arthroplasty

Background. When reversing the hard-soft articulation in inverse shoulder replacement, i.e. hard inlay and soft glenosphere (cf. Figure 1), the tribological behaviour of such a pairing has to be tested thoroughly. Therefore, two hard materials for the inlay, CoCr alloy and alumina toughened zirconia ceramic (ceramys®) articulating on two soft materials, conventional UHMWPE and vitamin E stabilised, highly cross-linked PE (vitamys®) were tested in a joint simulator. Methods. The simulator tests were performed at Endolab GmbH, Rosenheim, Germany, analogue to standardised gravimetric wear tests for hip prosthesis (ISO 14242-1) with load and motion curves adapted to the shoulder. The test parameters differing from the standard were the maximum force (1.0 kN) and the range of motion. A servo-hydraulic six station joint simulator (EndoLab) was used to run the tests up to 5*106 cycles with diluted calf serum at 37° C as lubricant. Visual inspection and mass measurements were done at 0.1, 0.5, 1, 2, 3, 4 and 5 million cycles using a high precision scale and a stereo microscope, respectivly. Results. The wear rates measured in the simulator are summarised in the table below and illustrated in Figure 2. The simulator wear rate of the standard articulation CoCr – UHMWPE is similar to that found in the corresponding pairing for hip endoprosthesis, although the articulation diameter of the glenospheres tested is larger (42 mm compared to 28 – 32 mm in hip joints). Replacing UHMWPE by the cross-linked vitamys®, the wear rate is reduced to about 1/3 for both hard counterparts, CoCr and ceramys®, respectively. Replacing the CoCr inlay by a part made from ceramys® lowers wear by about 37 % in articulation against UHMWPE. This difference is significant (p = 0.002, significance level 5 %). And comparing CoCr and ceramys® against vitamys®, yields a reduction of about 44 %. Which is significant again (p = 0.015, significance level 5 %). The lowest wear rate, with a reduction of about 80 % compared to the standard CoCr – UHMWPE, exhibits the pairing of both advanced materials, ceramys® – vitamys®. Conclusions. Long-term clinical follow-up will confirm if this in-vitro wear reduction leads to longer in-vivo survival of reverse total shoulder arthroplasty. Such a study is under ethic approval, currently. However, the ceramys® inlay offers the benefits of a nickel free inverse shoulder replacement with less x-ray opacity, compared to CoCr. To view tables/figures, please contact authors directly

Background. Residual stress remains in bone tissues after press-fit-fixation of a joint prosthesis, recently employed for joint arthroplasty. The response of bone tissues to the residual stress is, however, unknown because it is not physiological. This unnatural stimulus may have adverse effects on bone tissues, including causing thigh pain or bone resorption. In the present study, we designed an experimental method to apply a stationary load from inside an animal femur using a loop spring of titanium alloy with super elasticity. The femoral response was assessed based on the migration of the wire into bone twelve weeks after implantation. As the results, wire migration was noted in 10 of 11 cases. Methods. We developed a method using a loop spring made of super elastic titanium alloy, which can maintain sufficient stress in a rat femur for a prolonged period. This titanium alloy, which contains 43.94% titanium and 56.06% nickel, was supplied as a wire (WDL1, Actment Co., Ltd., Kasukabe, Japan). In the present study, an experimental method was designed to apply a stationary load from inside a rat femur by inserting a loop spring made of super elastic wire. Results. Ten weeks after implantation, migration of the spring wire into the cortical bone was noted in 10 of 11 cases. To assess spring migration in cortical bone, we measured the distance from the endocortical surface to the tip of springs on micro-CT images. The line of the endocortical surface was extrapolated from the adjacent to the wire contact area. The estimated load was distributed from 1.19 to 3.28 N. The migration depth on anterior and posterior sides was not associated with the estimated load. Discussion. In the present study, we developed a method of generating a stationary stress field in a rat femur using a loop spring made from Ni-Ti alloy with super ermore, implantation of the pin was presumed to be able to interpretation by the thelasticity. The load that originated from elastic deformation was large enough to apply mechanical stimulation to bone tissue. The estimated load was distributed from 1.19 to 3.28 N. Migration of the implanted loop spring in the femur was observed in ten of the eleven. The migration depth apparently did not increase with the increase in estimated load. Therefore, regardless of the load, that is stationary load is applied has been suggested to be involved in the migration of the pin. Furtheory of bone remodeling. n a state where the pin load of is applied, the bone implanted pin to which was destroyed by osteoclasts, was presumed to occur is bone formation in the implanted state. Interpretation. The present findings suggest that an excessive stationary load at the implant surface induces endosteal bone resorption together with the migration or protrusion of a prosthesis

The aim of this study is to investigate whether Metal-on-Metal (MoM) implants result in more chromosome aberrations and increased blood metal ions post-operatively when compared to Metal-on-Polyethylene (MoP) implants. Metal-on-metal arthroplasties are being inserted in increasing numbers of younger patients due to the increased durability and reduced requirement for revision in these implants. Recent studies have raised many concerns over possible genotoxicity of MoM implants. This is a prospective study of patients who have undergone elective total hip replacement, they were selected and then randomised into two groups. Group A received a MoP implant and group B received a MoM implant. Patients are reviewed pre-operatively (control group), at 3 months, 6 months, 1 year and 2 years post-operatively. On each occasion blood tests are taken to quantify metal ion levels (chromium, cobalt, titanium, nickel and vanadium) using HR-ICPMS method and chromosome aberrations in T lymphocytes using 24 colour fluorescent in situ hybridisation (FISH). 53 patients have been recruited to date. 24 of whom had MoP prosthesis and 29 a MoM. 37 of these have had their one year follow-up with blood analysis and 14 have had 2 year follow up. Cobalt and chromium concentration increased during the first 6 months in both MoM and MoP groups, in the MoM group the chromium levels were twice that of MoP group and 12x that of the preoperative samples. Chromosome aberrations occurred in both groups. At 6 months both the MoM and MoP groups showed increase frequency of aneuploidy aberrations with further increases after one year. Structural damage in the form of translocations occurred in the MoM group after one year, but not in the MoP group, by two years there was a profound increase in translocations Preliminary results of this study show that the levels of chromium and cobalt are significantly higher in the MoM group compared to the MoP group. This corresponds to increases in chromosome aberrations in the groups with increases in structural chromosome damage after two years

Introduction. While prosthesis survival in Total Knee Arthroplasty (TKA) exceeds 90% at 10 year, failures do occur. One area of concern has been the potential for metal allergy or metal sensitivity causing persistent pain, swelling or early failure of the implant in some patients. Definitive tests for diagnosing metal allergy and metal sensitivity have not been developed and this field remains controversial. In most cases where metal sensitivity is a concern, metals such as Chromium and Nickel are implicated. Despite the lack of good diagnostic tests for identifying these patients, several orthopedic prosthesis manufacturers have developed implants made of Titanium or ceramic designed for use in patients where concerns exist regarding metal allergy. In the absence of good diagnostic tests, use of these devices in patients that self identify is one option. To date, little information has been presented about the incidence of self reported metal sensitivity in patients undergoing joint replacement. This study was undertaken to determine the incidence of self reported metal allergy or sensitivity in patients undergoing total knee arthroplasty. Methods. An IRB approved, retrospective chart review was performed in a consecutive series of 194 patients who had undergone TKA at one institution, with one surgeon. Self reported metal sensitivity and allergy had been routinely elicited from each individual who had not undergone implantation of a previous metallic device, during pre-operative consultation. Results. 36 of the 194 patients had a previously well functioning implanted metal device. In addition, data was missing in 19 patients. Therefore, data from 139 out of 158 consecutive patients who had no prior implanted metal devices was available. 20 of 139 patients (14%) reported a known metal allergy or sensitivity. This included 19 of 86 females (22%) and 1 of 53 males (2%). This difference was statistically significant (P=0.001). Conclusions. If self reported prior metal sensitivity or allergy is used to guide prosthesis selection in TKA, approximately 14% of patients would be candidates for “hypo-allergenic” prostheses. If only particular sizes of components are offered in these alternative materials, smaller sizes or female gender specific sizes should be considered due to the higher incidence of self reported metal allergies in female patients