The evolution of orthopedic implants has witnessed a great evolution and allowed insights into the various metals and alloys compatible with the human body. However, some recent reports have raised concerns regarding hypersensitivity to several metals used in orthopedic implants. These cases are mostly documented in the field of arthroplasty. Metal ion release following hip or knee arthroplasty is a known phenomenon and associated immune reactions to these metal ions have been implicated in the causation of these hypersensitivity reactions. These reactions frequently lead to poor outcome following these implant surgeries. We here present two rare cases of metal induced hypersensitivity reactions following orthopedic surgeries. We have also reviewed the literature in this context to look into the various causes of metal reactions, types of implant involved in hypersensitivity, methods of testing and management options in these cases

Hip simulator studies have shown reduced hip offset can cause microseparation and increased wear in hard-on-hard hip bearings. However this has not been analysed yet in vivo. We studied the effect of reduced hip offset on serum metal ion levels in patients with metal-on-metal (MoM) hip arthroplasty. From all patients who underwent unilateral MoM bearing hip arthroplasty between 2005 and 2009, 63 patients had complete clinical evaluation, measurement of serum chromium and cobalt ion levels as well as biomechanical measurements on pre- and post operative radiographs (cup inclination, head inclination, change in hip offset and change in hip length.). Ten arthroplasties were revised due to adverse metal reaction and six patients awaiting revision. 55% of ASR hips showed higher metal ions (>7 ppb) whereas only 15% of non-ASR hips had higher ion levels. Patients with reduced postoperative hip offset by more than 5 mm had significantly higher mean metal ion levels compared to the the rest of the hips (31.8 ppb vs. 7.4 ppb, p=0.002). On subgroup analysis this effect was present in non-ASR hips (18.7 ppb vs. 4.7 ppb, p=0.025) but was not significant in ASR hips (29.6 ppb vs. 16.3 ppb, p=0.347). Our study demonstrated significantly higher serum metal ion levels in patients who lost more than 5 mm hip offset after arthroplasty. Reduced soft tissue tension leading to microseparation of the articulation and edge loading is a theoretical explanation for this effect. This may be relevant in other hard bearings such as ceramic-on-ceramic as well

BACKGROUND. The most common salvage of a failed metal-on-metal hip resurfacing is to remove both the femoral and acetabular resurfacing components and perform a total hip replacement. The other choices are to perform an acetabular or femoral only revision. A one or two piece acetabular component or a polyethylene bipolar femoral component that matches the retained metal resurfacing acetabular component is used. The considerations in favor of performing a one component resurfacing revision are maintaining the natural femoral head size, limiting the surgical effort for the patient and surgeon, and bone conservation. There are often favorable cost considerations with single component revision surgery. The reasons for femoral component revision are femoral neck fracture, femoral component loosening and an adverse reaction to metal wear debris. Performing a femoral component only revision requires a well fixed and well oriented acetabular component. Acetabular revision is most often performed for an adverse reaction to metal wear debris or loosening. METHODS. 81 acetabular revisions and 46 femoral revisions were evaluated 4 to 14 years after surgery. 83% of patients had their initial surgery at outside institutions. The mean age was 46 and 65% of patients were women. A two piece titanium backed polyethylene component was used in 44 patients and a one or two piece metal component was used in 37. A dual mobility femoral prosthesis mated to a retained metal acetabular component was used for the femoral revisions and no conversions to a metal-on-metal total hip replacement were performed. We selected polyethylene acetabular components for patients with adverse reactions to metal wear debris if their femoral component was less than 48 mm or if there was no matching metal acetabular component available for their femoral component. We used dual mobility components for femoral loosening, femoral neck fractures and adverse reactions to metal wear debris in patients with well-fixed and well oriented metal acetabular components. Dual mobility components were also used if there are any concerns about the femoral component or in some older patients. We performed one component revisions rather than conversion to total hip replacement on 88% of patients presenting with failed resurfacing prostheses. RESULTS. There were no failures with polyethylene acetabular components. There were two failures due to ongoing adverse metal reactions in patients receiving metal revision acetabular components. There was one failure with a dual mobility prosthesis due to accelerated polyethylene wear from undetected edge loading on a retained worn metal acetabular component. There were two infections and one patient with continued pain. There were no dislocations. The average Harris Hip Score was 94. The UCLA activity score was 6 or greater for all but 4 patients. There were 6 revisions to total hip replacement. The Kaplan-Meier survivorship was 94%. 95% of patients rated their outcome as excellent or good. CONCLUSIONS. Failed metal-on-metal hip resurfacing prostheses can be successfully revised without conversion to total hip replacement in most instances. A detailed knowledge of matching prostheses is necessary. Polyethylene prostheses for the acetabular or femoral reconstruction are often needed

Introduction. There has been much controversy around metal on metal hip replacements of late due to adverse metal reactions. There is evidence implicating lymphocyte mediated response (type IV delayed-hypersensitivity) to metal debris generated by the implants as one of the main factors responsible for the reactions. Our understanding of these adverse reactions continues to improve but we also recognize that the majority of patients with MOM implants are asymptomatic with well functioning implants. Studies have shown up to 16% allergy to metal ions on pre-operative allergy patch testing. We set out to determine the incidence of hypersensitivity to Cobalt, Chromium and Molybdenum in a arthroplasty population. Method. We assayed whole blood using a validated optimized lymphocyte transformation test, MELISA as part of a prospective randomized study on large diameter bearing surfaces. We recruited 47 subjects, 19 males, 28 females (35–75 yrs). Specific exclusions included presence of metal implants in the body and industrial exposure to metals. Results. Results were available for 46 patients. Four patients (9%) demonstrated hypersensitivity to Cobalt and none to Chromium or Molybdenum. Two were female and two male. The result was weakly positive in three patients and strongly positive in one female. Conclusion. Hypersensitivity in patients without prior exposure to Cobalt, Chromium and Molybdenum is low. The relevance of a positive hypersensitivity test and implications on the choice of bearings is a subject that requires further research. NO DISCLOSURES

Background. The failure and subsequent withdrawal of the ASR device in both its resurfacing and THR form has been well documented. The National Joint Registry report of 2010 quoted figures of 12–13% failure at five years. Adverse reaction to metal debris (ARMD) is a poorly understood condition and patients developing severe metal reactions may go unrecognised for sometime. Patients and Methods. In 2004 a single surgeons prospective study of the ASR bearing surface was undertaken. We present the ARMD failure rates of the ASR resurfacing and ASR THR systems. The diagnosis of ARMD was made by the senior author and was based on clinical history, examination, ultrasound findings, metal ion analysis of blood and joint fluid, operative findings and histopathological analysis of tissues retrieved at revision. Mean follow up was 52 months (24–81) and 70 patients were beyond 6 years of the procedure at the time of writing. Kaplan Meier survival analysis was carried out firstly with joints designated “failure” if the patient had undergone revision surgery or if the patient had been listed. A second survival analysis was carried out with a failure defined as a serum cobalt > 7µg/L. Full explant analysis was carried out for retrieved prostheses. Results. There were 505 ASR patients in total. 657 metal ion samples were available at the time of writing (152 repeats). Survival analysis using revision/listed as end point (at 6 years):. ASR resurfacing: 26.1% failure. ASR THR: 55.5% failure. Survival using ion analysis (at 5 years):. ASR resurfacing: 50.1% failure. ASR THR: 66.5% failure. The median (range) volumetric wear rate of failed prosthesis was 8.23mm. 3. /year (0.51–95.5). Conclusion. A number of design flaws in the ASR has led to excessive wear of the bearing & taper leading to catastrophic failure secondary to ARMD

Introduction. Modular femoral necks have shown promising clinical results in total hip arthroplasty (THA) to optimize offset, rotation, and leg length. Given the wide variety of proximal femoral morphology, fine-tuning these kinematic parameters can help decrease femoroacetabular impingement, decrease wear rates and help prevent dislocations. Yet, additional implant junctions introduce additional mechanisms of failure. We present two patients who developed an abnormal soft tissue reaction consistent with a metal hypersensitivity reaction at a modular femoral neck/stem junction requiring revision arthroplasty. Methods. Two patients underwent THA for primary osteoarthritis with the same series of components: 50 mm shell, a 36 mm highly-crosslinked polyethylene liner, uncemented titanium alloy modular stem with a 130 degree Cobalt Chromium (CoCr) modular femoral neck, and 36 mm CoCr head with a +5-mm offset. Patient 1 was a 63 year-old female who had an uneventful post-operative course but presented seven months later with progressive pain in the left hip. Patient 2 was an 80 year-old female who did well post-operatively, but presented with limp and persistent pain at 10 months post-op. An initial evaluation of a painful THA to rule out aseptic loosening, infection, mal-positioning, loosening and osteolysis included radiographs, lab work (CBC, ESR, CRP, Cobalt & Chromium levels) and Metal Artifact Reduction Sequence (MARS) MRI. Results. Elevated ion levels (Table 1) and Metal Artifact Reduction Sequence (MARS) MRI were consistent with an abnormal soft tissue reaction. A histological analysis of operative specimens displayed extensive necrosis and lymphocytosis, consistent with the diagnosis of metal hypersensitivity reactions (MHSR). Both patients underwent debridement and revision femoral arthroplasty with non-modular counterparts of the original femoral implant and have been asymptomatic post-operatively at greater than 1 year follow-up. Discussion. MHSR reactions are primarily described in the setting of metal on metal articulations of the head and acetabulum in THA and hip resurfacing. These reactions have not been reported at the modular neck/stem junction. Although modular necks show promise in THA, the advantages of increased component modularity must be carefully weighed against the risks of mechanical wear and subsequent MHSR and/or component failure

Introduction. In recent years, an increasing number of reports related to adverse reactions to metal debris (ARMD) following metal-on-metal (MOM) total hip arthroplasty (THA) have been published. Some patients who experience ARMD require revision surgery. Objectives. In this study, we aimed to evaluate the mid-term results of MOM THA. Methods. We retrospectively reviewed all patients who underwent THA at JCHO Saitama medical center from January 2007 to December 2010. A metal liner and metal femoral head were used in 37 of 214 cases (17%). This sub-group comprised 2 men and 35 women (mean age at surgery, 63.5 years; range, 39–79 years). The original disease is 28 osteoarthritis, 5 osteonecrosis, 3 rheumatoid arthritis and 1 rapidly destructive hip coxarthropathy. We investigated the system type, size (cup, femoral head, and stem), and cup position (anteversion and inclination). Moreover, we used imaging (radiography and computed tomography [CT] or magnetic resonance imaging [MR]) to assess for aseptic loosening, metal hypersensitivity reactions, and pseudotumor formation. Results. Six women with osteoarthritis experienced significant localized soft tissue reactions, and underwent revision. The average duration to revision was 41months(range, 28–63). Of these, 4 patients had received the PINNACLE cup system (Depuy; 4/14, 28.6%) and 2 had received the M2a-Taper cup system (BIOMET; 2/23, 8.7%). The femoral head sizes of the PINNACLE system used was 36 mm, and the femoral head sizes of the M2q-Taper systems used were 28mm and 32mm. Four patients had no signs or symptoms, 1 patient complained of anterior thigh dullness and 1 patient had a dislocation. The average cup anteversion was 15.7 degrees (range, 10–19 degrees) and the average inclination was 49.2 degrees (range, 43–57 degrees). Conclusions. MOM THA was associated with a higher incidence of revision. The majority of cases that required revision had no severe signs or symptoms. Therefore, all cases of MOM THA should be assessed periodically using CT or MRI