Purpose of Study:. To look at the difference in metal ion levels using Ceramic on Metal (COM) and Metal on Metal (MOM) bearings in Total Hip Replacements, comparing the results between well placed and poorly placed cups. Methods:. Metal ion levels using the ICP-MS method of assay have been studied as part of a prospective randomised trial between 4 different bearing combinations. The ion levels have been raised in the COM and MOM bearings. Metal ions are not raised in the Ceramic on Ceramic (COC) and Ceramic on X linked Poly(COP) bearings, showing that no other material in the study prosthesis aside from the bearing surfaces contribute to raised ion levels. Cup inclination and cup anteversion has been measured in all patients. Results:. At 3 year follow-up the Cobalt and Chrome levels are significantly lower with the COM bearing than the MOM bearing when both well and poorly placed cups are included, and seem to be returning to normal pre-operative levels. Taking cups put in in Lewinnik's safe zones, then the Chrome levels are similar between the two bearings, but the Cobalt levels remain raised in the MOM bearing. Conclusion:. Cobalt and Chrome levels are significantly lower in COM bearings than MOM bearings when cups are not placed in the ideal position. This represents an added advantage in the use of COM bearings as compared to MOM bearings

Introduction. It is well-known that wear debris generated by metal-on-metal hip replacements leads to aseptic loosening. This process starts in the local tissue where an inflammatory reaction is induced, followed by an periprosthetic osteolysis. MOM bearings generate particles as well as ions. The influence of both in human bodies is still the subject of debate. For instance hypersensitivity and high blood metal ion levels are under discussion for systemic reactions or pseudotumors around the hip replacement as a local reaction. The exact biopathologic mechanism is still unknown. The aim of this study was to investigate the impact of local injected metal ions and metal particles. Material and Methods. We used an established murine inflammation model with Balb/c mice and generated three groups. Group PBS (control group, n=10) got an injection of 50µl 0.1 vol% PBS-suspension, Group MI (Metal-ion, n=10) got an injection of 50µl metal ion suspension at a concentration of 200µg/l and Group MP (Metal-particles, n=10) got an injection of 50µl 0.1 vol% metal particle suspension each in the left knee. After incubation for 7 days the mice were euthanized and the extraction of the left knee ensued. Followed by immunhistochemical treatment with markers of inflammation that implied TNFα, IL-6, IL-1β, CD 45, CD 68, CD 3, we counted the positive cells in the synovial layer in the left knees by light microscopy, subdivided into visual fields 200× magnified. The statistical analysis was done with Kruskal-Wallis test and a post hoc Bonferroni correction. Results. The Group with metal particles showed significantly elevated inflammatory markers (TNFα, IL-6, IL-1β, CD 68, CD 45) compared to all other groups. Interestingly, CD 3 as a marker for T-lymphocytes showed no increased levels in all groups. The metal ion group showed significant elevated CD 45 expressions compared to the control group. Conclusion. The results clearly demonstrate that especially metal wear particles lead to an intensive inflammatory reaction. The tissue formations in the metal particle group show an osseous destructive behavior in previously demonstrated results, comparable to pseudotumors. But, in this study, the expression of the immunohistological markers CD 3, CD 45 and CD 68 indicate that the tissue consists of leucocytes and macrophages, whereas lymphocytes could not be detected. This might be due to an acute inflammatory reaction, whereas the adaptive immune response by T-lymphocytes seems not (yet) to be activated. Overall it must be stated that solid metal wear particles are responsible for local inflammatory reactions, whereas it is still unknown whether wear particles corrode in vivo and release a potentially high level of locally toxic metal ions

Introduction:. The clinical significance of serum metal ion levels alone in patients with stemmed MoM hip arthroplasty remains uncertain. This study aims to measure the metal ion levels in patients with unilateral and bilateral hip arthroplasty to see whether or not the patients with bilateral hips have higher metal ions. Patients and Methods. All the patients with bilateral MoM hip arthroplasty were identified from the research database. These patients were then matched with those in a similar age group who had a unilateral hip arthroplasty, but same University of California Los Angeles (UCLA) activity score. The UCLA activity scores along with other hip scores have been previously gathered for all the patients. Both sets of patients then had measurement of serum cobalt and chromium levels. The results were analyzed and compared. Results:. There were a total of 53 patients with bilateral hips and 53 matched patients with unilateral hips. The average serum Cobalt and Chromium levels were 34 nmol/L (range <10–76) and 23 nmol/L (range <10–104) respectively in the bilateral group; and 14 nmol/L (range <10–45) and 21 nmol/L (range <10–57) in the unilateral group. Given that the MHRA (UK) threshold levels deemed clinically significant are 120 nmol/L and 135 nmol/L for Cobalt and Chromium respectively; the results obtained here are not clinically significant. Conclusions:. One would normally expect, with mathematical reasoning, a patient with bilateral hip arthroplasty to have higher serum metal ion levels than a patient with unilateral arthroplasty. However, this study goes to show that it is not the case

Introduction. Cemented stems have shown 90–100% survivorship when coupled with polyethylene acetabular component. This study aims to compare cemented stem behaviour in combination with large metal on metal (MOM) vs. metal on poly (MOP) bearings. Patients and Methods. 100 patients were recruited into a single centre RCT (we required 40 in each group for power .90 to confirm stem subsidence of >0.5mm at 2 years; p< 0.05). Recruits were randomized to MOP (28mm) or MOM femoral heads with CPCS cemented femoral stem. Assessments included X-rays (AP pelvis), Harris Hip Scores, blood metal ion levels and patient questionnaires (WOMAC, SF-36, satisfaction questionnaire). Evaluations were done pre-operatively and 3, 12 and 24 months post operatively; blood metal ion measures at 1 year. Results. There were 50 patients in each arm of study matched for age (64 ± 8.5) and BMI (29.04 ±5.5). There was no difference in femoral stem subsidence at 2 years 1.34 (±1.3) and 1.4 (±1.2) mm for MOM and MOP respectively (p=0.88). There was significant improvement in HHS from pre-op to 3 months: 41 to 87 for MOM and 44 to 86 for MOP (p=0.00). This was maintained with no difference between groups at 2 years (p=0.74). Similar pattern was seen for WOMAC and SF-36 scores for both groups at 2 years (p>0.05). Increased blood Cobalt and Chromium levels were observed in 17% and 0% for MOM and MOP group. MOM group reported better patient satisfaction for overall (91% vs. 79%), pain relief (82% vs 66%) and improvement in ADL activities (94% vs.70%) at 2 years. Conclusions. There were no significant differences between groups for stem behavior, clinical and patient reported outcomes. Despite higher patient satisfaction reported by MOM patients, increased metal ion levels had raised concerns regarding the use of MOM bearings with cemented stems for primary THR

Introduction. The aim of this study is to report the results of Revision hip arthroplasty using large diameter, metal on metal bearing implants- minimum 2 year follow up. Methods. A single centre retrospective study was performed of 22 consecutive patients who underwent acetabular revision surgery using metal on metal bearing implants between 2004 and 2007. Birmingham hip resurfacing (BHR) cup was used in all patients - monoblock, uncemented, without additional screws in 16 cases and cemented within reinforcement or reconstruction ring in 6 cases. Femoral revisions were carried out as necessary. Results. There were 16 men and 6 women with a mean age of 71 years (51-83). Revision surgery was performed for aseptic loosening in 10, infected primary hip arthroplasty in 8, infected Hemiarthroplasty in 1 and Peri-prosthetic fracture with loosening in 3 patients. A 2-stage revision was performed for all infected hips. One patient died and the remaining 21 patients had clinical and radiological assessment at a mean 35 months (24-60). The mean Harris hip score was 75 (23-98) with 50% good to excellent results. Only 1 patient had further revision to a proximal femoral replacement and constrained cup in 2 stages for recurrent infection at 24 months. There were 2 recurrent infections (both revised for septic loosening) and 1 non-union of trochanteric osteotomy. There were no dislocations in the group. No radiological loosening of implants or metal ion complications have been seen at last follow up. Conclusions. We believe this is the first reported series on the use of large diameter metal on metal bearing surfaces for revision hip arthroplasty. Our series shows satisfactory short to medium term results in this complex group of patients with no component loosenings, despite monoblock cups and no dislocations

Background. Previous studies have suggested that the modular junction of metal on metal (MoM) total hip replacements (THR) is an important source of metallic debris. Methods. We carried out a prospective study using custom techniques to analyse one of the largest collections of failed contemporary MoM devices in the world. All explants from patients who had suffered adverse reactions to metal debris (ARMD) were included in this study. These explants included: 82 36mm THRs, and 147 resurfacing head THRs and 140 resurfacing arthroplasties from several manufactures. Volumetric wear analysis of the bearing surfaces and taper junctions was carried out using a coordinate measuring machine. The relationships between total metallic loss and metal ion concentrations and the macroscopic and histological tissue appearance of THR patients were compared to those in resurfacing patients. Mann Whitney test for non-parametric data was used to assess significant differences between groups. Results. Resurfacing explants retrieved from patients who had suffered ARMD were found to have significantly higher median rates of volumetric wear than the THRs (10.16 versus 2.25mm. 3. /yr (p < 0.001)). Total volumetric material loss from taper junctions ranged from 0.01 to 21.55mm. 3. When volumetric taper wear was combined with bearing surface wear in the THR patients this total rate of material loss was still significantly less than in the resurfacing patients 2.52 versus 10.16mm. 3. /yr (p < 0.001)). Despite this, macroscopic tissue destruction and extent of ALVAL infiltration was found to be significantly greater in the THR patients. Conclusion. Taper debris appears to more readily stimulate a destructive immune cascade than debris from primary bearing surfaces. This cascade can culminate in catastrophic tissue necrosis when blood metal ion concentrations appear normal. MHRA guidance should distinguish clearly between MOM THRs and resurfacings

Purpose of the study:. Recent literature raised concern on the adverse effects, incidence of pseudo tumours and raised blood and urine Chromium and Cobalt levels in patients with a metal on metal articulation. The purpose of this study was to follow up a cohort of patients that received a metal on metal total hip replacement with minimum follow up of ten years and to compare the results with the literature. Methods:. All the available patients that underwent metal on metal total hip replacements during 1999 to 2000 with a minimum follow up of 10 years were clinically examined and evaluated with the Harris Hip Score; X-rays; Full Blood Count; CRP; LFT; U, K & E; blood and urine Chromium and Cobalt levels and Ultrasonic examination of the hip. The ultrasound was done by an independent experienced ultrasonographist in each case to exclude pseudo tumours or fluid collections. The patients were clinically examined to try and find any adverse effects of the metal on metal articulation. Results:. We found one patient that had a revision of the femoral component for a peri-prosthetic fracture retaining the metal on metal articulation that subsequently developed loosening and a pseudo tumour. The remaining patients had excellent Harris Hip Scores and their implants showed no osteolysis or radiological signs of loosening. Conclusion:. Despite the recent concern we obtained good results after ten year follow up with metal on metal prosthesis. However we do recommend careful selection of patients, detailed attention to surgical technique and close follow up when considering metal on metal articulation. Patients should be counselled about the possibility of tissue reaction to the bearing surface and possible future revision surgery

Fracture of the acetabulum can lead to degenerative arthritis of the hip, avascular necrosis of the femoral head, or both. Total hip arthroplasty is a common form of surgical treatment when significant joint changes and pain are present. Ten patients with fracture acetabulum were treated in this study using metal on metal total hip arthoplasty. The initial fracture was posterior wall fracture in one patient, posterior column fracture in one patient, transverse fracture in 2 patients, fracture dislocation in 3 patients and fracture posterior wall and column in 3 patients. The indications of arthroplasty were secondry osteoarthritis after internal fixation or after conservative management or collapse of the femoral head. Arthroplasty was done after an average period of 1.8 years (range from 1 to 4 years). After a follow up period ranged from 3 to 7 years with a mean of 4.6 years, the Harris hip score was improved from a mean of 51 (range 20 to 65) to a mean of 92.5 (range 90 to 95). Infection occurred in one case and two stages revision was done. Another case developed loosening of the acetabular component and was revised using cementless cup fixed with screws and bone graft. Metal on metal THR after acetabular fracture are relatively uncomplicated and lead to a good outcome despite the difficulties faced during the procedure

Metal on metal total hip arthroplasty provides the potential improvement in articular wear and the use of large-diameter femoral heads following the prospect for reduction in the risk of dislocation. The purpose of this study was to compare the clinical and radiographic outcomes as well as serum metal ion level between the two different component designs with small and large femoral heads in metal on metal total hip arthroplasty. We studied 39 patients with large head (Magnum®, Biomet; cup size minus 6 mm) and 37 patients with small head (M2a taper®, Biomet; 28 or 32 mm head) of metal on metal total hip arthroplasty between December 2009 to October 2011 with follow-up of 2.1 years (1.0–3.3 years) after surgery. Harris Hip Score, UCLA activity score, EQ-5D, radiographic assessment, and serum cobalt and chromium ion levels were evaluated. Harris Hip Score, UCLA activity score, and EQ-5D were improved after surgery in small and large head groups, however, no significant differences were observed between both groups. Cup inclination was below 50 degree in all prosthesis. No loosening and no osteolysis were observed. Cobalt and chromium ion was not detected before surgery; however, metal ion levels of both groups were increased after surgery in time dependent manner. There was no significant difference between two groups at one year after surgery. One patient in each group showed the increase of cobalt ion level over 7 ppb (15.4 ppb, 12.9 ppb) without any clinical symptom including pain. Cup inclination was 29 degree in both patients and cup anteversion was 38 and 41 degree, respectively. There was no significant difference of ion levels between both groups. No dislocation was observed in large head group while one dislocation occurred in small head group. No patients required the revision surgery. This metal on metal component, especially with large femoral heads, showed the good clinical results at the maximum follow up of 3.3 year after surgery. However, the ion level of two patients increased over 7 ppb and longer follow-up will be needed

Introduction. To report the short to medium term results of acetabular reconstruction using reinforcement/reconstruction ring, morcellised femoral head allograft and cemented metal on metal cup. Methods. Single centre retrospective study of 6 consecutive patients who underwent acetabular reconstruction for revision hip surgery. The acetabulum was reconstructed using morcellised femoral head allograft and reinforcement or reconstruction ring fixed with screws. The Birmingham cup – designed for cementless fixation, was cemented into the ring in all cases. The uncemented Echelon stem with metal on metal modular head was used for reconstructing the femur. Data from our previous in-vitro study had shown good pull out strength of a cemented Birmingham cup. Results. There were 2 men and 4 women with a mean age of 75 years(57-83). Revision was performed for aseptic loosening in 2, septic loosening in 2 and peri-prosthetic fracture with loosening in 2 patients. All patients were reviewed clinically and radiographically at a mean of 36 months follow-up(range 24 - 42 months). Revision was not necessary in any patient for failure of acetabular or femoral fixation. However, 1 patient had revision to a proximal femoral replacement and constrained cup for recurrent infection and osteomyelitis at 24 months. This patient was excluded from the final analysis. The mean Harris hip score at last follow up was 79(range 70-89). Radiographic analysis revealed good graft incorporation and no signs of loosening or cup/ring migration. No dislocations or metal ion problems were recorded in this series. Conclusions. To the best our knowledge, this is the first series using cemented metal on metal cups within a reinforcement/reconstruction ring for revision hip arthroplasty. Excellent cemented fixation of the cup, manufactured for cementless fixation, was obtained at surgery with no evidence of loosening, and no dislocations at minimum 24 months follow up

ZrN-multilayer coating is clinically well established in total knee arthroplasty [1-3] and has demonstrated significant reduction in polyethylene wear and metal ion release [4,5]. The goal of our study was to analyze the biotribological behaviour of the ZrN-multilayer coating on a polished cobalt-chromium cemented hip stem. CoCr28Mo6 alloy hip stems with ZrN-multilayer coating (CoreHip®AS) were tested versus an un-coated version. In a worst-case-scenario the stems with ceramic heads have been tested in bovine serum in a severe cement interface debonding condition under a cyclic load of 3,875 N for 15 million cycles. After 1, 3, 5, 10 & 15 million cycles the surface texture was analysed by scanning-electron-microscopy (SEM) and energy-dispersive x-ray (EDX). Metal ion concentration of Co,Cr,Mo was measured by inductively coupled plasma mass spectroscopy (ICP-MS) after each test interval. Based on SEM/EDX analysis, it has been demonstrated that the ZrN-multilayer coating keeps his integrity over 15 million cycles of severe stem cemented interface debonding without any exposure of the CoCr28Mo6 substrate. The ZrN-multilayer coated polished cobalt-chromium cemented hip stem has shown a reduction of Co & Cr metal ion release by two orders of a magnitude, even under severe stem debonding and high interface micro-motion conditions. ZrN-multilayer coating on polished cobalt-chromium cemented hip stems might be a suitable option for further minimisation of Co & Cr metal ion release in total hip arthroplasty. Clinical evidence has to be proven during the next years

Orthopaedic cobalt chromium particles and ions can induce indirect DNA damage and chromosome aberrations in human cells on the other side of a cellular barrier in tissue culture. This occurs by intercellular signalling across the barrier. We now show that the threshold for this effect depends on the metal form and the particle composition. Ionic cobalt and chromium induced single strand breaks at concentrations equivalent to those found in the blood of patients with well functioning metal on metal hip prostheses. However, they only caused double strand breaks if the chromium was present as chromium (VI), and did not induce chromosome aberrations. Nanoparticles of cobalt chromium alloy caused DNA double strand breaks and chromosome aberrations, of which the majority were tetraploidy. Ceramic nanoparticles induced only single strand breaks and/or alkaline labile sites when indirectly exposed to human fibroblasts. The assessment of reproductive risk from maternal exposure to biomaterials, especially those liberated by orthopaedic implants, is not yet possible with epidemiology. Whilst the barrier model used here differs from the in vivo situation in several respects, it may be useful as a framework to evaluate biomaterial induced damage across physiological barriers

Medical and Health care products Regulatory Agency (MHRA) released an alert in 2010 regarding metal on metal (MoM) bearings in hip arthroplasty owing to soft tissue reactions to Metal debris. Following this, we adopted a targeted screening protocol to review patients with this bearing couple. 218 Patients (252 hips), mean age 53.2 (25–71) years were assessed clinically using Oxford hip score (OHS) and X-ray examination. The mean follow up was 44.5 (12–71) months. Patients were considered at higher risk (118 patients/133 hips) if they had deterioration of OHS (50 hips), Small sized heads <50mm (114 hips), acetabular inclination >500 (37 hips), neck thinning (17 hips). These patients (107/118), (120/133 hips) were further investigated through measuring metal ion levels and magnetic resonance imaging (MRI). The mean blood levels of cobalt and chromium in this group were 6.7, 8.62 ug/L respectively. Metal ions increased significantly with high acetabular inclination angles (p=0.01, 0.004 respectively), but was not affected by the size of the head (p=0.13). MRI showed periprosthetic lesions around 28 hips (26 fluid collections, 2 pseudotumours). The screening protocol detected all patients who subsequently required elective revision. We believe that this protocol was beneficial in detecting problematic MoM hip replacements

In a cross sectional cohort study three different metal on metal total hip systems were assessed. Two monoblock acetabular designs; the Durom socket (Zimmer, Warsaw, In) and the Birmingham socket (Smith and Nephew, Memphis, TN), and one modular metal on metal total hip system (Pinnacle, Depuy Orthopaedics, Warsaw, In) in patients who have received these implants in the our region. 56 patients were recruited in total. All patients were assessed clinically, radiologically and biochemically. Whole blood Cobalt, Chromium and titanium levels were tested. The median head size used in the Birmingham group was 52mm (Range 44mm to 56mm), and in the Durom group, 48mm (Range 42 to 54mm). The median head size used in the modular Pinnacle group was 40mm (Range 36–44mm). The blood metal ions levels in the larger non modular acetabular sockets were significantly raised compared to the Pinnacle group. For Co 1.95 µg/l and 2.70 µg/l in the Durom and Birmingham groups respectively compared to only 0.52 µg/l in the Pinnacle group (P< 0.001). Mean Cr levels were the same for the two monoblock systems, 1.9 µg/l compared to the Pinnacle sockets 1.2 µg/l (P< 0.001). Our study clearly demonstrates that there is a significant difference in metal ion levels in patients following a monobloc large head arthroplasty system compared to a smaller modular metal on metal hip arthroplasty. The smaller head size appears to produce less metal ions whilst at the same time a 36mm–44mm head size is large enough to increase hip stability and range of movement as well as decreasing the risk of impingement. In our practice we are no longer using this design and the safest strategy, when considering metal on metal bearings, is to use a modular, smaller head system such as the Pinnacle

The poor outcome of large head metal on metal total hip replacements (LHMOMTHR) in the absence of abnormal wear at the articulating surfaces has focussed attention on the trunnion / taper interface. The RedLux ultra-precision 3D form profiler provides a novel indirect optical method to detect small changes in the form and surface finish of the head taper as well as a quantitative assessment of wear volume. This study aimed to assess and compare qualitatively the tapers from well functioning small diameter, with poorly functioning LHMOMTHR's using the above technique. Method. 3 groups of retrieval tapers were analysed (Group 1: 28 mm CoCr heads from well functioning MOMTHRs (n=5); Group 2: Large diameter CoCr heads from LHMOMTHRs revised for failure secondary to adverse reaction to metal debris (n=5); Gp 3 (control): 28 mm heads from well functioning metal on Polyethylene (MOP) THRs; n=3). Clinical data on the retrievals was collated. The Redlux profiling of modular head tapers involves a non direct method whereby an imprint of the inside surface of a modular head is taken, and this is subsequently scanned by an optical non contact sensor using dedicated equipment [1]. The wear was also measured on the bearing surface [1]. RedLux profiling of the tapers produced a taper angle and 3D surface maps. The taper angles obtained with the Redlux method were compared to those obtained using CMM measurement on 3 parts. The Redlux profiling, including imprints, was also repeated 3 times to gauge potential errors. Results. There was no difference in mean 12/14 taper angles between groups. There was no difference in volumetric and linear wear at the bearing surface between groups. Only the LHMOMs showed transfer of pattern from the stem to the internal head taper, with clear demarcation of the contact and damaged area between head taper and stem trunnion (see figure 1 – interpretation of head taper surface features demonstrated using Redlux optical imaging). 3D surface mapping demonstrated wear patterns compatible with motion or deformations between taper and trunnion in the LHMOM group. These appearances were not seen in tapers from small diameter MOM and MOP THRs (see Figure 2). Discussion. Differences in appearance of the taper surface between poorly functioning LHMOMTHRs and well functioning MOP or MOM small diameter devices highlight an area of concern and potential contributor to the mode of early failure. Further work is required to fully qualify the Redlux method capabilities, and to understand the origin of the damage seen on those tapers, and the possible partial contribution of damage caused during retrieval

This paper presents an ongoing review of the use of a wedge-shaped porous metal augments in the shoulder to address glenoid retroversion as part of anatomical total shoulder arthroplasty (aTSA). Seventy-five shoulders in 66 patients (23 women and 43 men, aged 42 to 85 years) with Walch grade B2 or C glenoids underwent porous metal glenoid augment (PMGA) insertion as part of aTSA. Patients received either a 15º or 30º PMGA wedge (secured by screws to the native glenoid) to correct excessive glenoid retroversion before a standard glenoid component was implanted using bone cement. Neither patient-specific guides nor navigation were used. Patients were prospectively assessed using shoulder functional assessments (Oxford Shoulder Score [OSS], American Shoulder and Elbow Standardized Shoulder Assessment Form [ASES], visual analogue scale [VAS] pain scores and forward elevation [FE]) preoperatively, at three, six, and 12 months, and yearly thereafter, with similar radiological surveillance. Forty-nine consecutive series shoulders had a follow-up of greater than 24 months, with a median follow-up of 48 months (range: 24–87 months). Median outcome scores improved for OSS (21 to 44), ASES (24 to 92), VAS (7 to 0), and FE (90º to 140º). Four patients died, but no others were lost to follow-up. Apart from one infection at 18 months postoperatively and one minor peg perforation, there were no complications, hardware failures, implant displacements, significant lucency or posterior re-subluxations. Radiographs showed good incorporation of the wedge augment with correction of glenoid retroversion from median 22º (13º to 46º) to 4º. All but four glenoids were corrected to within the target range (less than 10º retroversion). The porous metal wedge-shaped augments effectively addressed posterior glenoid deficiency as part of aTSA for rotator cuff intact osteoarthritis, producing satisfactory clinical outcomes with no signs of impending future failure

A concern of metal on metal hip resurfacing arthroplasty is long term exposure to Cobalt (Co) and Chromium (CR) wear debris from the bearing. This study compares whole blood metal ion levels from patients drawn at one-year following Birmingham Hip Resurfacing (BHR) to levels taken at a minimum 10-year follow-up. A retrospective chart review was conducted to identify all patients who underwent a BHR for osteoarthritis with a minimum 10-year follow-up. Whole blood metal ion levels were drawn at final follow-up in June 2019. These results were compared to values from patients with one-year metal ion levels. Of the 211 patients who received a BHR, 71 patients (54 males and 17 females) had long term metal ion levels assessed (mean follow-up 12.7 +/− 1.4 years). The mean Co and Cr levels for patients with unilateral BHRs (43 males and 13 females) were 3.12 ± 6.31 ug/L and 2.62 ± 2.69 ug/L, respectively, and 2.78 ± 1.02 ug/L and 1.83 ± 0.65 ug/L for patients with bilateral BHRs (11 males and 4 females). Thirty-five patients (27 male and 8 female) had metal-ion levels tested at one-year postoperatively. The mean changes in Co and Cr levels were 2.29 ug/l (p = 0.0919) and 0.57 (p = 0.1612), respectively, at one year compared to long-term. These changes were not statistically significant. This study reveals that whole blood metal ion levels do not change significantly when comparing one-year and ten-year Co and Cr levels. These ion levels appear to reach a steady state at one year. Our results also suggest that regular metal-ion testing as per current Medicines and Healthcare products Regulatory Agency (MHRA) guidelines may be impractical for asymptomatic patients. Metal-ion levels, in and of themselves, may in fact possess little utility in determining the risk of failure and should be paired with radiographic and clinical findings to determine the need for revision

Purpose. To evaluate the radiological changes after metal on metal resurfacing arthroplasty. Materials and Methods. Between December 1998 and August 2004, 166 hips in 150 patients who underwent metal resurfacing arthroplasty and followed up more than 4 years. Their mean age at the time of operation was 37.3 years(range, 15–68 years) and mean period of follow-up was 6.1 years(range, 48–95 months). The cause of arthroplasty included 115 avascular necrosis, 43 osteoarthritis, 7 ankylosing spondylitis, 1 haemophilic arthropathy. All patients had anteroposterior, translateral radiographs of the hip made preoperatively and each follow-up visit, and we analyzed radiographic findings such as radiolucencies or impingement signs around implant, neck narrowing and heterotopic ossification. Results. There was a no significant difference between preoperative and postoperative Harris hip score and range of motion. The mean stem-shaft angle was 137.4°, and 55.4% were ranged 130° to 140°. The mean inclination of acetabular component was 44.9°. There were no radiolucent lines or osteolytic lesion around the acetabular components, but 3 hips showed radiolucency around the head-neck junction(1.8%) and 4 hips showed radiolucent line around the stem (2.4%). 12 hips had impingement signs around the head-neck junction (7.2%), and 2 cases showed neck narrowing (1.2%). 3 cases had some heterotopic ossification (1.8%). In 12 cases with impingement signs, the stem-shaft angle and inclination of acetabular component were lower than control group. Pseudotumor was not found in this cohort. Conclusions. This study demonstrates no serious radiological problems till the midterm follow-up after resurfacing arthroplasty, but osteolytic lesion such as radiolucent line around head-neck junction, neck narrowing can be a potential cause of failure in future. Even though the radiolucent line around stem of femoral component revealed no subjective symptom yet, it suggests the micromotion of femoral component which can lead to femoral component loosening. The most common radiological findings, impingement signs, seem not to have clinical significance

Metal ion levels are used to track the performance of metal containing bearings in hip replacement patients. Changes in whole blood metal ion levels are indicators of wear rates in these bearings. Normal metal ion levels are variable, and range widely. Changes in these “non-bearing” levels over a period of time may influence the monitoring of these bearings. Methods. As part of a prospective randomised trial of different bearing surfaces, whole blood metal ion levels were monitored. This included four cohorts of patients, namely ceramic-on-ceramic (CoC), ceramic-on-polyethylene (CoP), ceramic-on-ceramic (CoC) and ceramic-on-metal (CoM). Serial whole blood metal ion levels in the non-metal bearings, namely CoC and CoP, were analyzed. Results. There was no consistency in these whole blood metal ion levels. Intra-patient variations in these levels over a period of time could not be due to bearing-produced metal ions as these were all metal free, and thus not the source of any endogenous ions. These intra-patient variations may reflect changes in exogenous exposure to these metal ions, fluctuations in these patient's metabolic functions or production of metal ions from non-bearing prosthetic sources. Conclusion. This finding of variations of “normal” intra-patient whole blood metal ions highlights the importance of determining a patient's average baseline levels, particularly when these are used to determine changes in these levels when part of a protocol to monitor the performance of metal containing hip replacement bearings

INTRODUCTION. The risk of dislocation in large diameter metal on metal hip replacement is significantly lower than in standard THR. This is due to the increased primary arc, increased jump distance and possibly a suction effect. Our unit has performed over 1500 of these cases with an overall revision rate of <1%. We report a case series of dislocations in 5 large diameter metal on metal hips undertaken at our unit. METHOD. All cases were reduced closed and investigated for cause of dislocation. Radiological investigation included plain film radiographs and CT to exclude component mal-position and MRI to document soft tissue deficiency. Metal ion levels were measured and microbiological investigation was undertaken. RESULTS. In all cases component positioning was acceptable. Metal ion levels were significantly elevated with levels comparable to published work. MRI showed significant soft tissue defects in all patients. At revision all were found to have necrotic areas associated with a large turbid effusion. Histology confirmed metal related inflammatory change and microbiology specimens confirmed the absence of infection. DISCUSSION. The local detrimental effects of metal debris are well documented. We believe this is the first series with a proven link between these soft tissue problems and dislocation. Every case of large diameter metal on metal hip in our unit that has dislocated has been proven to be associated with metallosis and has required revision