Introduction and Aims: Polyethylene wear continues to be the most significant issue following total hip arthroplasty (THA), leading to the current increase in use of alternative bearing surfaces. We performed a prospective, randomised, blinded clinical trial comparing metal versus polyethylene bearing surfaces in patients receiving THA. Method: Forty-one patients were randomised to receive a metal (23) or a polyethylene (18) insert with identical femoral and acetabular components. Patients were evaluated pre-operatively at three, six, 12 months and annually thereafter, including an evaluation of erythrocyte and 24-hour urine cobalt, chromium and titanium metal ion levels, validated outcome measures (WOMAC, SF-12, Harris Hip Score) and radiographs. Results: No patients were lost to follow-up. One patient died of unrelated causes. At an average 4.4 (range 3.3–5.1) years follow-up there were no differences in any outcome measures or radiographic findings. Patients receiving metal liners had significantly elevated metal ion measurements. At the latest follow-up erythrocyte cobalt levels were seven times elevated (median 1.2μg/l (metal) Vs 0.18μg/l (poly), p< .001). Urine cobalt levels were 41 times elevated (median 11.9μg/day (metal) Vs 0.29μg/day (poly), p< .001) and urine chromium levels were 14 times elevated (median 4.9μg/day (metal) Vs 0.36μg/day (poly), p< .001). Erthrocyte chromium, titanium and urine titanium were not significantly different between groups. As well, contrary to previous reports, there was not a significant trend towards decreasing ion levels over time. Conclusion: In this prospective randomised blinded clinical trail comparing metal to polyethyle bearing surfaces, both cobalt and chromium ion levels were significantly elevated in the blood and urine of the patients randomised to receive the metal on metal THA

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

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

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

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

Summary. The M2a-38. tm. metal on metal total hip arthroplasty showed a high incidence of pseudotumors and an unexpected high revision rate in our thoroughly screened cross sectional cohort. Introduction. After the revival of the metal on metal (MoM) bearing in total hip arthroplasty (THA) at the beginning of this century, there are now serious questions about this type of bearing. The advantage of large head MoM bearing is the increase in range of motion and stability. In our institution the choice was made for 38 mm heads. During the last few years concerns have been raised about the relationship of MoM bearing and elevated serum cobalt and chromium ion levels, their local and systemic toxicological effects and the incidence of local tumorous masses (pseudotumors). Are these findings applicable for all MoM bearings or are there also product specific issues. We present the outcome of a cementless MoM THA using a 38mm head in a unique consecutive series of 377 THA who were performed in our institution. Patients and Methods. All 351 patients (377 THA) with a cementless MoM THA (M2a-38. tm. , Biomet Inc, Warsaw, IN, USA, and Taperloc® stem, Biomet UK, Bridgend) between 2008 and 2011 were evaluated. All patients were analyzed by a physical exam, serum levels of cobalt and chromium and an interview to determine if there were any complaints. An MRI of the hip was made if patients reported pain during physical activity, allergies to metals, serum cobalt or chromium ion levels ≥ 5 ppb or if the inclination of the acetabular component was more than 50 degrees. Nine patients deceased, three were lost to follow up and four already underwent a revision before the screening. We analyzed 361 hips with an average follow up of 30 (range 2–58) months. The average preoperative age was 63 years (41–88). Results. 219 patients with 235 THA (65%) reported no complaints. Median cobalt level in patients with complaints was 6.6 (0.2–173) ppb and in the group without complaints 3.7 (0.2–27.3) ppb. Median chromium level in patients with complaints was 5.0 (0.1–134) ppb and in the group without complaints 3.7 (0.2–27) ppb. On the 226 performed MRI scans, 56 pseudotumors were diagnosed and described using the Anderson classification (9 C1, 41 C2 and 5 C3). 71 hips had been revised after a mean follow of 30 months (range 0.2–50 months). Reasons for revision were because of pain, raised metal ions and a pseudotumor in 28; pain and raised metal ion levels in 15; aseptic loosening of the acetabular or femoral component in 11; raised metal ions and a pseudotumor in 7; combination of luxations, luxation feelings and fractures in 5; infections in 3 and for other reasons in 2. Conclusion. The short-term results of the THA with a 38mm head metal on metal articulation are higher compared with other MoM bearings. They show a revision rate of 7% and 10% in the Australian and England register. In other peer reviewed literature we find a revision rate between 0–13% after five years. We also observed a high incidence of elevated serum levels of metal ions, pseudotumors and an unexpected high early revision rate

One hundred fifty one total hip arthroplasty (THA) with metal on metal hip system of without cement were followed at a mean of 5. 5 years (range 2. 6 years to 7 years). Original diseases were 134 hip in 123 cases with osteoarthritis and 17 hips in 13 with rheumatoid arthritis. The average Harris hip score of before the operation was 45. 3 points and at the follow-up time the average score was 88. 5 points. Radiographic findings in the incidence of partial radiolucent line around the component: in the acetabular component, no radiolucent line was observed, in the femoral component, marginal lucent lines were 8. 6% (13 hips). Cortical hypertrophy was observed in high ratio of 27. 2%(41 hips). There was no loosening and tilt of component over 5 degrees observed in any patient. Postoperative dislocation of the hip was observed 9 hips (6. 0%). Cobalt concentrations and chromium concentration in the serum were measured in cases in metal on metal total hip, metal on poly arthroplasty and in controls without implants. Serum was assayed using graphite furnaces atomic absorption spectrophotometer. No patients were seen of elevation in serum cobalt and chromium concentrations. The authors conclude that THA with metal on metal system has presented excellent results for mid term follow-up in our hospital

Aims: A polyethylene free, metal on metal acetabular system (Hofer-Imhof cup; Lubrimet metal on metal articulation made of CoCr-forge alloy) was designed in an effort to improve total hip arthroplasty longevity. This study was undertaken to review the clinical performance of this implant and to determine if acetabular loosening or revision and wear and osteolysis were prevalent. The long term results (mean follow up period 110 months) are presented in this study. Methods: In this prospective, randomized study a minimum of 90 months follow up results involving the first 100 implanted metal liner total hip arthroplasties are presented. The mean follow up was 110 months. Between April 1995 and November 1996 ninety-eight patients (100 hips) had a total hip replacement consisting of a titanium cementless self reaming, parabolic cup, a cementless titanium stem and the Lubrimet® metal on metal articulation. Two acetabular and one femoral component had to be revised due to aseptic loosening without showing macroscopic evidence of metallosis and no histological evidence of excessive metal wear. One patient hat to be revised by a complete change of the total hip (acetabular component and stem) showing histologic evidence of a metal induced hyperergic immunologic reaction. One patient presented with a broken neck of the stem and had to be revised by stem exchange. As a none device related orthopedic complication one acetabular component required revision surgery due to a periprosthetic fracture. Conclusions: The long term results of the Hofer-Imhof Lubrimet®Metal-on-metal articulation are satisfying and so the system represented a viable alternative for total hip arthroplasty in younger higher demand patients in the past. Due to the possible development of a hyperergic immunologic reaction to the metal on metal articulation and the availibility of a ceramic on ceramic articulation we do not implant this liner anymore

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 coupling in total hip replacement has been widely used since many years. After the rebirth of resurfacing a new trend to use very large diameter metal-metal coupling with standard stem prostheses has been started. New prostheses, old and new problems. We analyze first failures with new large diameter metal on metal coupling. The analysis focused on seven early failures of large diameter metal-metal prostheses (two resurfacing and five cementless prosthesis with XL head) over the first series of 350 cases (100 resurfacing and 250 cementless) in the first year. Synovial fluid aspiration have been performed in all failed patients searching for metal ions and bacterial proliferation. Moreover, prosthetic component positioning was also studied as a possible primum movens of these failures. Some failed patients underwent epicutaneous patch test for skin reaction to metal. One resurface prosthesis failed as a result of an vascular necrosis and conseguent fracture of the femoral neck and revealed a moderate increment in metal ion concentration in blood and synovial fluid obtained at time of revision. One resurface prosthesis failed as a result of an infected metallosis with a huge intraabdominal mass and revealed a huge increment in metal ion concentration in blood, addominal and synovial fluid. This patient underwent a lumbotomy to evacuate the abdominal retroperitoenal mass before prosthesis removal for a two step procedure. Out of the five failures of metal on metal cementless prosthesis with XL head four were the result of aseptic loosening and one was the result of a low grade infection discovered at coltures after revision surgery. Three showed clear metallosis caused by wrong positioning (more than 50° of cup inclination). All of these three presented an articular noise and elevated blood and sinovial fluid metal ion concentration. The fourth patient with aseptic loosening had a good component positioning but demonstrated an epicutanous allergic reaction to Cobalt. Also one of the three patients with metallosis resulted allergic to Cobalt. The blood and sinovial metal ion values were always elevated but particularly high in patients with cup inclination over 50°. Large head metal on metal prostheses demonstrated a higher percentage of early failure in our experience. They are very sensible to positioning. Blood and sinovial metal ion determination helps to promptly diagnose a bad metal on metal prosthetic functioning. A more accurate analysis about the different metals available on the market and their resistance to edge wear should not be delayed any further

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

Purpose: A single blind prospective randomised controlled trial comparing the Metal-on-polyethylene articulation with the metal-on-metal articulation in THA.

Method: The clinical and radiological findings of the consecutive patients who were enrolled in the RCT at the participating centres were recorded prospectively. The clinical evaluation was performed with the Harris scoring system as well as the Oxford Hip Scoring Sheet. The computer randomised option was revealed to the operative surgeon only after the patient was anaesthetised, during the recruitment period (June 1998 to July 2004). Of the total of 378 patients, 2 died prior to the final review and 63 were lost to follow-up. The final study group contained 315 patients, with 159 patients in the metal-on-polyethylene group and 156 patients in the metal-on-metal group.

Results: The indication for the hip arthroplasty for majority (309 patients) was primary osteoarthritis. The average age at the time of the surgery was 68.2 years and the average duration of follow-up was 85 months (42–115). There was an improvement of the Oxford hip scores from an average of 37 per-operatively to 16 postoperatively. The Harris hip scores also improved from an average of 47.0 pre-operatively to 87.3 post-operatively. The patient groups were statistically similar with respect to age, sex and duration of follow-up, and the final outcome scores revealed no statistical difference between the two groups.

Conclusion: The clinical results obtained with the use of the articulation are comparable to those obtained by the metal-on-polyethylene articulation encouraging the use of this alternative bearing surface.

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

Ninety-four hips with a mean patient age 34.2 (range 15– 40) with a metal/metal surface arthroplasty (SA) were reviewed with 71% men and 14% with previous surgery. The Chandler risk index was calculated as well as the SA risk index (SARI). At a mean follow-up three years, three hips were converted at a mean of twenty-seven months (two to fifty), and ten patients had significant radiological changes. Mean SARI for the thirteen problematic hips versus remaining hips was significantly higher, 4.7 and 2.6, respectively (p=0.00). If SARI > 3 the relative risk of early problems is twelve times greater than if SARI ≤3. The purpose of this study was to evaluate the early outcome of a hybrid metal on metal surface arthroplasty of the hip in patients forty years and younger and identify potential risk factors. Surface Arthroplasty Risk Index can help identify patients who may be at increased risk of early failure following metal on metal surface arthroplasty. Proper patient selection and careful surgical technique may minimize early failures with the re-introduction of surface arthroplasty of the hip. Ninety-four hips mean age 34.2 (range 15– 40) with metal/metal surface arthroplasty (SA) were reviewed with 71% men and 14% with previous surgery. The Chandler risk index was calculated and SA risk index (SARI). Mean follow-up three years (range 2–5), three hips were converted at a mean of twenty-seven months (2–50), and ten patients had significant radiological changes. Mean SARI for these thirteen problematic hips versus remaining hips was significantly higher, 4.7 and 2.6, respectively (p=0.00). The mean angle between the prosthesis stem and femoral shaft in the problematic group was significantly smaller than the remaining hips (p=0.03): 133° and 139°, respectively. If SARI > 3 the relative risk of early problems is twelve times greater than if SARI ≤3

Metal on Metal bearings have functioned satisfactorily for up to 30 years without a full understanding of what shape the components were at the start, or as they were worn over time. Modern metrology methods can use elegant computer driven coordinate measuring machines in both manufacturing and retrieval analysis as most manufacturers and laboratories do. This method however is fl awed in its ability to look at the much higher levels of resolution required for analysing these bearings. A method has been developed which will analyse to the sub micron deviances from roundness that the subleties of manufacturing can achieve, and allows an analysis of wear of explanted implants. Both new and explanted Ring, McKee, Stanmore, Metasul and Resurfacing implants have demonstrated initial form variances that range from 1 to over 100 microns out of round. Roundness trace analysis has allowed linear wear on explanted implants to be measured from 0.5 to 150 microns. This represents combined head and cup linear annual wear rates from 2 to 65 microns per year. Metal heads and cups are not manufactured as round as has been believed. The average wear rates over time for different Metal on Metal systems is not the same

Retrospective analysis of 25 consecutive metal on metal proximal femoral replacements performed at our unit between 1965 and 1979. Methods. Patients were: clinically evaluated using the Modified Harris Hip and Enneking Scoring Systems and radiologically using the ISOLOS scoring system. The concentration of Cr, Co, Ti, Al, V, Mo & Ni in whole blood and urine was also measured by High-Resolution Inductively Coupled Mass Spectrometry and compared with controls and patients with other implants. Retrieved prostheses (in situ for in excess of 25 years) were analysed for roughness and wear using a Mitutoya form tracer and an electron microscope. Results. Thirteen patients have since died; nine from metastatic disease and four from other causes. Of the remainder, eleven (44%) are still alive, five still retaining metal on metal articulations and one has been lost to follow up. They have been in situ for an average of 32 years. The average modified Harris Hip score is 76 (53–93) and the average Enneking Score is 74 (63–90). In the retrieved prostheses the contact zones were found to be smoother (Ra 0.05?m), have fewer and smaller carbides together with evidence of ‘self-healing’ when compared to the original surface (Ra 0.32?m). Blood & urine levels of Co & Cr were significantly elevated. Co levels were exceptionally elevated in loose prostheses but levels quickly fell following revision. Conclusion. We have shown the potential longevity of metal on metal arthroplasty. The wear seen in retrieved specimens is low and we might expect to improve the fixation by reducing the torque with apical bearing and encouraging extra-cortical bone bridging with hydroxy-apatite coated collars. Elevated serum and urine Co levels may well predict a loose prosthesis and may be useful as a screening tool

Background: Metal on metal resurfacing of the hip is an attractive conservative treatment option for the younger, active arthritic patient. It has the advantages of bone preservation and the longevity of metal bearing surfaces. Concerns remain over the performance of these implants due to historical failure of similar devices. The possible longer-term survival of these implants can only be justified if the early results are as successful as conventional hip replacement. Patients & Methods: The clinical and radiological follow-up of our first 25 consecutive resurfacing patients is presented. The Birmingham Hip Resurfacing prosthesis (Midland Medical Technologies, Birmingham, UK) was used, and all procedures performed by the senior author (EHM). Clinical assessment was done using the modified Harris Hip Score, and functional outcomes measured using the Western Ontario and McMaster Universities Osteoarthritis index (WOMAC). Radiographs were examined for radioleucent lines, migration of components, osteolysis and heterotropic ossification. Results: 28 primary hip resurfacings in 25 patients were reviewed. The mean follow up period was 18 mts (12– 36mts). The mean age of patients at time of operation was 51yrs (37–64 yrs). Main indication for surgery was Osteoarthrosis. The mean Harris Hip Score improved from 44 preoperative, to 94.5 postoperative. The mean preoperative WOMAC score was 30 and the mean postoperative score 88.The average duration of hospital stay was 5 days, and the average operative blood loss 3g %. All patients in paid employment returned to work at an average of 8 weeks postoperatively, and majority of patients are able to participate in sports and recreational activities. There were no cases of dislocations, femoral neck fractures, avascular necrosis or osteolysis. Conclusion: Hip resurfacing using metal on metal hybrid fixed components, offers a viable treatment alternative in younger active patients. Early outcomes are at least comparable to total hip replacement in terms of pain relief and restoration of function. Despite the lack of long-term data, the relative absence of complications and the potential benefits justify its continued use. We believe the future is very promising for this procedure

Patients with DDH are known to be at risk of early degenerative changes to their hips. To date, no consensus exists as to the most appropriate management of this group, with many surgical options being associated with specific complications such as dislocation and early wear. In addition, modern resurfacing methods are considered by many to be contra-indicated in patients with DDH due to the technical difficulty of the procedure. This prospective study analyses a single surgeon series of known DDH hips that underwent metal on metal resurfacing from November 1999 to July 2004 inclusive. There were 31 resurfacings carried out on 28 patients (11 males, 17 females). The mean age of the study group at the time of surgery was 43.9+/−9.1 years. No patient was lost to follow up. Pre-operatively, 23 hips were classified as Crowe I (n=9), II (n=5), III (n=5) and IV (n=4). Patients were followed up to a mean of 46.4+/−18.1 months. The mean Harris Hip scores were 54.9+/−9.3 pre-operatively and 98.1+/−4.9 post-operatively (p< 0.001, Student’s t-test). Using the UCLA activity profile, the mean scores were 3.2+/−1.0 pre-operatively and 6.4+/−1.8 post-operatively (p< 0.001, Student’s t-test). Although the management of young patients with early degenerative changes secondary to DDH remains controversial, the results of this study suggest that not only is resurfacing technically possible even in advanced cases, it also offers excellent functional outcomes and should be considered in appropriate cases

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 on metal press-fit acetabular cups are the worst performing acetabular cup type with severe failure consequences compared to cups made from more inert materials such as polyethylene or ceramic. The cause of failure of these cup types is widely acknowledged to be multi-factorial, therefore creating a complex scenario for analysis through clinical studies. A factorial analysis has been carried out using an experimentally validated finite element analysis to investigate the relative influence of four input factors associated with acetabular cup implantation on output parameters indicating potential failure of the implantation. These input factors were: cup material stiffness; cup inclination; cup version; cup seating; and level of press-fit. The output parameter failure indicators were: wear; tensile strains in the underlying bone; bone remodelling; and cup-bone micromotions. The factorial analysis concluded that the most significant influence was that of cup inclination on wear, and the second most significant was the influence of the level of press-fit on bone remodelling at the acetabular rim. Significant influence was also observed between version angle and wear, and cup-seating and micro-motion. The results demonstrated the clear multi-factorial nature of implant failure and highlighted the importance of correct implant positioning and fit

Introduction: Disagreement exists in the literature as to whether hip resurfacing requires more acetabular reaming than uncemented hip replacement. Materials and Methods: Thirty-nine patients underwent total hip arthroplasty with a large metal on metal resurfacing acetabular cup and large metal head with a conventional uncemented femoral stem. Although there was no change in routine operative technique the femoral neck was measured (as if for resurfacing) before being cut. The size of the acetabular component actually inserted was compared with the smallest size which could have been used had a resurfacing been carried out for each patient. A two tailed paired t test was carried out. Results: We found that there was no difference in female patients but in men the actual cup used was 2.44mm smaller than the smallest possible resurfacing cup which equates to 6.39cm. 3. less bone (p < 0.0001). Discussion: By using paired samples we have reduced confounding factors and shown that a large metal on metal bearing on a conventional stem is more conservative of acetabular bone than hip resurfacing in male patients

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 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 small diameter with LHMOMTHR's. 3 groups of retrieval tapers were analysed (Group 1: 28mm CoCr heads from MOMTHRs (n=5); Group 2: Large diameter CoCr heads from LHMOMTHRs (n=5); Group 3: 28mm heads from metal on polyethylene (MOP) THRs; n=3). Clinical data on the retrievals was collated. Both bearing surfaces and head tapers were measured for wear using the Redlux profiling non contact measurement system. Measurements included taper angle and 3D surface maps. 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. 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. 3D surface mapping demonstrated wear patterns compatible with motion or deformations between taper and trunnion in the LHMOM group alone. Discussion: Differences in appearance of the taper surface between LHMOMTHRs and 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

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

In-vitro studies have shown that wear rates of the metal on metal (MOM) bearing hip prostheses decline once the bearing runs-in and the bearing subsequently enters a steady state wear phase. Baseline cobalt levels are thus expected to decline with time in patients. Several clinical studies have not found such a decline. Baseline cobalt levels are hence limited in their capacity to provide information on the wear performance of the bearing couple. We have demonstrated in a previous study that exercise causes a rise in plasma metal ion levels in patients with MOM bearing hip replacement. Would the exercise related cobalt rise be more sensitive to detect change in wear behaviour of the bearing couple? We tested the alternate hypothesis that exercise related rise in the plasma cobalt levels will correlate inversely with the duration of MOM implantation. Sixteen patients with three different well functioning MOM bearing hip replacement [two types of resurfacing (BHR, Cormet) and Metasul] were included into the study. Patients were divided in to two groups based on time since implantation, an early group of mean 18 months and a late group of mean 57 months. Plasma levels of cobalt were measured before (baseline) and after 1 hour of maximal exercise (peak). The difference between baseline and peak for each patient provided the exercise related cobalt rise. A significant increase in plasma cobalt levels of 13% was noticed after the exercise (p < 0.005). Baseline Cobalt levels in the late group (53nmol/l) were higher than early group (44nmol/l) but the difference was not significant (p=0.45). However, the mean exercise related Cobalt rise levels was lower in late group (3.5nmol/l) than the early group (6.5nmol/l). This lower rise in cobalt level in the late group precisely reflects on the steady state wear as seen in in-vitro tests. Baseline cobalt levels are limited in determining the in-vivo performance of the bearing couple. Exercise related rise in cobalt levels can differentiate the running in and steady state wear phases of metal on metal bearings and is thus a more accurate tool of assessing in-vivo wear performance of the bearing couple

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

The ‘first generation’ Metal on Metal bearing devices was typically produced from cast, high carbon CoCrMo alloy and was in the as-cast condition. They exhibited course, hard primary, and block carbides supported by a softer matrix material. This bi-phasic condition has been verified through reported literature and forensic scientific studies of ‘long-term survived’ retrieved ‘first generation’ devices. The as-cast microstructure of CoCrMo alloys possesses superior wear resistance to the microstructures formed following post cast thermal treatments. It has been well reported that the improvement of mechanical properties, such as tensile or fatigue strength, can be achieved through the thermal treatment of this alloy. Thermal treatments of this alloy have been found to alter its’ microstructure with a significant modification to the carbide phase morphology. The modifications vary with a tendency for a refinement of the carbide size through dissolution of the chromium and molybdenum through solid state solution. Through the examination of the wear patterns of retrieved devices and wear testing of this material in its’ various microstructural conditions, it has been shown that modifications to the carbide morphology, to achieve improved mechanical properties, reduces its’ bio-tribological properties/performance leading to a lower wear resistance. The as-cast carbide morphology is the most mechanically stable condition and with its’ volume fraction, reduces the potential for adhesive wear of the matrix through ‘matrix to matrix’ contact of the two opposing bearing surfaces. It has been reported that abrasive wear is the typical mechanism for metal on metal bearings due to the generation of ‘third body’ particles from carbide asperity tips fracturing during the initial ‘running-in’ period [typically 500k to 1M cycles]. After this stage the carbides become almost level with the surrounding softer matrix material with ‘third body’ scratches dominating the surface topography. Evidence of surface pitting on ‘first generation’ devices [McKee Farrar and Muller] and modern high carbon wrought devices [Metasul] has been attributed to adhesive/fatigue wear following surface-to-surface contact. Therefore, in microstructural conditions, where there is a reduced carbide volume fraction, or no carbides present, wear resistance is reduced. To test this hypothesis two wear tests have been carried out on CoCrMo samples produced from the same chemistry alloy, with varying microstructures, using Calowear [abrasive] and Pin on Dist [adhesive] tests. The as-cast microstructural condition was determined to have the lowest wear coefficient [k=mm3/Nm] in both tests, however statistical significance at 90% confidence interval was only confirmed in the Calowear Test. Examination of wear scars confirmed the mechanical stability of the as-cast carbide phase. It is noted, however that there are papers which have been published offering a divergence of opinion to this hypothesis and which have been considered by this author

Introduction: The wear particles produced from the metal-on-metal hip prosthesis causes measurable rise of metal ion levels in the patient’s body fluids. Wear of the bearing is directly related to its use. The goal of this study is to test two hypotheses. Firstly, that exercise causes increased wear particles in vivo which can cause immediate measurable rise in the serum metal ion levels. Secondly, that this rise in metal ion level is different for different types of bearings. Material and Methods: Eighteen participants were allocated to four different groups i.e. Birmingham Hip Resurfacing prosthesis group, Cormet 2000 resurfacing prosthesis group, Thrust plate prosthesis group (28mm metasul articulation) and group four with out any metal work. Blood samples were taken immediately before, immediately after and one hour after exercise. Plasma cobalt and chromium was determined using Inductively-Coupled-Plasma-Mass-Spectrometry and Dynamic-reaction-cell respectively with detection limit of 2nmol/l each. Results: The four patient groups were comparable. A significant increase (p< 0.005) in serum cobalt and chromium of 13% and 11% respectively, was noticed after the exercise. Rise of cobalt levels in patients with a resurfacing MOM was 8.5 times (BHR group) and 6.5 times (Cormet group) larger than in those with a Metasul (p=0.021 and p=0.047). Neither rise of metal levels nor baseline levels correlated with any other factor (p> 0.27). Discussion: Physiologic exercise causes immediate detectable rise in the serum metal ion levels. The increase is predominantly related to the size of the bearing surface. Exercise-related-cobalt-rise could be used to assess the tribology of the different metal on metal designs in vivo for future research

Aims: Measure serum chromium (SrCr) and cobalt (SrCo) and urine chromium (UCr) levels in patients with metal on metal surface arthroplasty of the hip. Methods: Ion levels were measured prospectively in 22 patients implanted with the Conserve Plusª (Wright Medical, TN) CoCr hip resurfacing. There were 15 males and 7 females with an average age of 49 years (range 28 Ð 62 yr). Serum and urine samples were collected using strict anti-contamination techniques pre-operatively and at 3, 6 and 12 months using graphite furnace atomic absorption spectrophotometry. Results: All postoperative metal levels were increased compared to their pre-operative levels. SrCr and SrCo values are at their highest at 3 months post operative and then begin to decrease. UrCr although elevated at 3 and 6 months postoperatively compared to the preop values, the levels continued to increase after the 6-month interval. These values are approximately 4-fold, 7-fold and 3-fold higher in SrCr, UrCr and SrCo, respectively, compared to the values seen in a group of patients with well functioning conventional metal (CoCr) on polyethylene total hips at 84 months postoperative measured by our group. Conclusions: The present levels are 2-fold lower in both SrCr and UrCr and 3-fold lower in SrCo than a group of patients with older generation surface arthroplasties reported previously by our group, suggesting improved manufacturing techniques and material properties have resulted in reduced component wear and generation of wear particles. 12 and 24 month data are currently being collected and analyzed

Introduction. We conducted independent wear analysis of retrieved metal on metal (MoM) hip components from around the world. All patients with resurfaced hips who developed adverse reactions to metal debris (ARMD) were found to have increased wear of the bearing surfaces. This was untrue in patients with large diameter (?36mm) MoM total hip replacements. This led us to search for other factors leading to ARMD. Methods. MoM THR explants retrieved from 78 patients suffering ARMD underwent full volumetric wear analysis of bearing surface and taper-junctions using coordinate measuring machine. Scanning electron microscopy (SEM) used to characterise material composition of specific areas. Results. 34 MoM THRs were found to have relatively low bearing surface wear (< 3mm. 3. /year). In each of these cases, material loss up to 60 microns wear depth was identified on the internal taper-junctions of femoral components. However, volumetric loss was rarely >5mm. 3. Similarly only 65% of metal ion levels of these patients were found to be greater than the MHRA guidance figure (7µg/L). Patterns of material loss at the tapers were consistent with antero-posterior force splaying open the taper-junction. This characteristic pattern was identified in number of commercially available devices (titanium and cobalt chromium stems). Soft tissue lesions were severe in patients found to have taper damage. Histology confirmed severe ALVAL with lymphoid neogenesis in majority cases, suggesting that wear debris from taper junctions may have greater potential to stimulate adverse immune response. Discussion. The results suggest that forces transmitted from large diameter hard-on-hard bearing surfaces are sufficient to cause mechanical damage to modular junctions with secondary localised corrosion. We urge caution in the use of these designs and recommend a re-evaluation of the stem head interface

The poor outcome of large head metal on metal total hip replacements (LHMOMTHR) in the absence of abnormal articulating surface wear 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 form and surface finish of the head taper as well as quantitative assessment of wear volume. This study aimed to assess and compare qualitatively tapers from small and large diameter MOMTHR's. Tapers from 3 retrieval groups were analysed. Group 1: 28mm CoCr heads from MOMTHRs (n=5); Group 2: Large diameter CoCr heads from LHMOMTHRs (n=5); Gp 3 (control): 28mm heads from metal on polyethylene (MOP) THRs; n=3). Clinical data on the retrievals was collated. RedLux profiling of tapers produced a taper angle and 3D surface maps. The taper angles were compared to those obtained using CMM measurements. There was no difference between groups in mean 12/14 taper angles or bearing surface volumetric and linear wear. Only LHMOMs showed transfer of pattern from stem trunnion to head taper, with clear demarcation of contact and damaged areas.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. 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

Introduction: Several studies have shown the presence of cobalt (Co) and chromium (Cr) ions in blood, urine, and organs of patients after THA using Co-Cr alloy-based implants. Even though it is well known that exposure to heavy metals may lead to significant alterations in human sperm morphology and motility, less is known on the effect of Co and Cr on semen parameters after metal on metal (MOM) hip replacement. Methods: Semen was collected form 10 patients between 41 and 49 years old (mean=45.9±3.0 years) by masturbation after 2–3 days of abstinence. The time of implantation varied from 1 to 9 years (mean=5.1±3.9 years). Samples were collected in a sterile container and examined within 1h after ejaculation for morphology, motility, and number of sperm cells following standard criteria. All patients were doing well at their follow-up visits (Harris Hip Score=94±4; UCLA activity a score=7±1) and no sign of osteolysis was observed on X-rays. Co and Cr concentrations were measured in both the seminal plasma and in the blood of patients by inductively coupled plasma-mass spectroscopy (ICP-MS). Results: results showed that the levels of Co in the seminal plasma and the blood of the patients were not statistically different. However, the level of Cr was significantly lower in the seminal plasma than in the blood of the patients. The ejaculate volume (2.1 ±0.6 ml), the sperm density (66±53 x 106), the total sperm count (151±75 x 106/ml), the pH (8), and the percentage of normal morphology (46±18%) were in the range of the WHO criteria for fertile population and also in the range of reference patients in the city of measurements. However, the viability was lower than that observed in a fertile population without prosthesis (41±19%). Conclusions: results of the present study strongly suggest that both Co and Cr ions crossover to the semen but that their concentrations were too low to significantly affect sperm parameters of young patients with MM prosthesis. Further longitudinal studies are however necessary to conclusively determine the effect of metal ions from MM prosthesis on sperm parameters

Introduction: Local problems of metal on metal (MOM) hip arthroplasty such as pseudotumours, neck thinning and osteolysis maybe related to concentrations of cobalt and chromium ions in the synovial fluid. There is little reported on these values. Our aim was to determine the range of metal ion levels in synovial fluid, and to investigate the relationship between these samples and simultaneous blood samples. Methods: Synovial fluid and whole blood samples were taken from 30 consecutive patients at the time of revision surgery for a painful MOM hip. Aspirated fluid was not visibly contaminated with blood. Impants were in situ for a mean period of 31 months. All had normal renal function. Samples were analysed using ICP mass spectrometry and compared with 10 samples from patients without implants. Results: The mean (and range) of synovial fluid metal ion levels were 1965 ug/l (30 to 13618) and 6265 ug/l (11 to 81630) for Cobalt and Chromium respectively. There was a good correlation between synovial and blood levels for both cobalt (R=0.65, p = 0.0001) and chromium (R = 0.59, p = 0.006). Discussion and Conclusion: Metal ions in synovial fluid from MOM hips are generated from wear of the bearing surfaces, the correlation with blood metal ion levels, shown in this study, suggest that blood levels may be used as surrogate marker for hip wear rate. Our range of synovial fluid metal ion levels may be useful for those conducting in vitro studies on the biocompatibility of MOM hips

This study reports the mid-term results of a large bearing uncemented metal on metal total hip replacement (MOMHTHR) matched series using the Synergy stem and Birmingham modular head in 36 hips (mean follow up 61 months). All patients underwent clinical, metal ion and MRI assessment. Wear analysis was performed on retrieved heads using Redlux non-contact optical profilometry. Seven patients (19%) have undergone revision surgery. All revisions had two or more of either symptoms, high metal ions or an MRI suggestive of an adverse reaction to metal debris (ARMD). There was no evidence of component malposition or impingement. Frank staining of tissues together with high volume dark brown fluid collections were found in all cases. All stems and cups were well fixed. In 4 cases pubic and ischial lysis (adjacent to the inferior fins) was observed. All 7 cases had radiological, intraoperative and histological evidence of ARMD (Figure 1). The failure cohort had significantly higher whole blood cobalt ion levels and OHS (p = 0.001), but no significant difference in cup size (p = 0.77), gender predominance, stem offset or cup position (p = 0.12). Sleeves had been used in all revision cases. Wear analysis (n = 4) demonstrated increased wear at the trunnion/sleeve interface in a distribution compatible with micromotion (Figure 2). There was normal wear at the articulating surface. This series further demonstrates unacceptable failure rates in LHMOMTHR in a series where a compatible stem for the BHR modular head was used. Use of a CoCr sleeve within a CoCr head taper appears to contribute to abnormal wear and therefore potential ARMD and subsequent failure

Introduction: The advantages of metal on metal bearings (MoM) include improved wear characteristics and lower dislocation rate. Metal sensitivity and Aseptic Lymphocyte Dominated Vasculitis Associated Lesion (ALVAL) reaction are becoming increasingly recognised. The BOA has recently issued a statement regarding MoM bearings. They suggested that any revisions for symptoms of pain and soft tissue reaction should be reported to the MHRA and histological specimens forwarded to the Stanmore Retrieval Centre. Methods and results: We report four patients (all females), who presented with late dislocation of a large diameter MoM bearing (three following total hip replacements and one following resurfacing). They all made good initial recovery with complete relief of pain. They developed pain around groin between one and two years following the surgery. Inflammatory markers were normal. MRI/Ultrasound scanning showed the presence of cystic lesions around the hip. They all presented with relatively late dislocation (26 months to six years). At exploration there was a large joint effusion with necrosis and detachment of the abductors. A characteristic finding was an avascular bare trochanter stripped free of any soft tissues. Histology showed a predominantly histiocytic response in keeping with the findings of Willert and Pandit. Discussion: In the absence of any obvious causes for dislocation, one should have a high index of suspicion for the possibility of metal hypersensitivity causing joint effusion, muscle necrosis and thereby leading to instability due to the progressive periosteal and soft tissue erosion. These patients should be considered for early revision of the bearing surface to prevent further damage to the muscle and bone. If the abductors are completely detached a more constrained type of bearing should be used to improve the stability. To the best of our knowledge this is the first report of this unusual complication following MoM bearings

This study reports the mid-term results of a large bearing hybrid metal on metal total hip replacement (MOMHTHR) in 199 hips (185 patients) with mean follow up of 62 months. Clinical, radiological, metal ion and retrieval analysis were performed. Seventeen patients (8.6%) had undergone revision, and a further fourteen are awaiting surgery (defined in combination as failures). Twenty one (68%) failures were females. All revisions and ten (71%) awaiting revision were symptomatic. Twenty four failures (86%) showed progressive radiological changes. Fourteen revision cases showed evidence of adverse reactions to metal debris (ARMD). The failure cohort had significantly higher whole blood cobalt ion levels (p=0.001), but no significant difference in cup size (p=0.77), inclination (p=0.38) or cup version (p=0.12) compared to the non revised cohort. Female gender was associated with increased risk of failure (p=0.04). Multifactorial analysis demonstrated isolated raised Co levels in the absence of symptoms or XR changes were not predictive of failure (p=0.675). However the presence of pain (p<0.001) and XR changes (p<0.001) in isolation were significant predictors of failure. Wear analysis (n=5) demonstrated increased wear at the trunnion/head interface (mean out of roundness measurements 34.5 microns (normal range 8–10 microns) with normal wear levels at the articulating surfaces. Macroscopically corrosion was evident at the proximal and distal stem surfaces. Cumulative survival rate, with revision for any reason was 92.4% (95%CI: 87.4–95.4) at 5 years. Including those awaiting surgery, the revision rate would be 15.1% with 89.6% (95% CI: 83.9–93.4). Cumulative survival at 5 years. This MOMHTHR series has demonstrated unacceptable high failure rates with evidence of high wear at the head/trunnion interface and passive corrosion to the stem surface. Female gender was an independent risk factor of failure. Metal ion levels remain a useful aspect of the investigation work up but in isolation are not predictive of failure

This study reports the mid-term results of a large bearing hybrid metal on metal total hip replacement (MOMHTHR) in 199 hips (185 patients) with mean follow up of 62 months. Clinical, radiological outcome, metal ion levels and retrieval analysis were performed. Seventeen patients (8.6%) had undergone revision, and a further fourteen are awaiting surgery (defined in combination as failures). Twenty one (68%) failures were females. All revisions and ten (71%) of those awaiting revision were symptomatic. Twenty four failures (86%) showed progressive radiological changes. Fourteen revision cases showed evidence of adverse reactions to metal debris (ARMD). The failure cohort had significantly higher whole blood cobalt ion levels (p=0.001), but no significant difference in cup size (p=0.77), inclination (p=0.38) or cup version (p=0.12) in comparison to the non revised cohort. Female gender was associated with an increased risk of failure (chi squared p=0.04). Multifactorial analysis demonstrated isolated raised Co levels in the absence of either symptoms or XR changes was not predictive of failure (p=0.675). However both the presence of pain (p<0.001) and XR changes (p<0.001) in isolation were both significant predictors of failure. Wear analysis (n=5) demonstrated increased wear at the trunnion/head interface (mean out of roundness measurements of 34.5 microns +/−13.3 (+/−2SD, normal range 8-10 microns) with normal levels of wear at the articulating surfaces. There was evidence of corrosion at the proximal and distal stem surfaces. The cumulative survival rate, with revision for any reason was 92.4% (95%CI: 87.4-95.4) at 5 years. Including those awaiting surgery, the revision rate would be 15.1% with cumulative survival at 5 years of 89.6% (95% CI: 83.9-93.4). This MOMHTHR series has demonstrated unacceptable high failure rates with evidence of high wear at the head/trunnion interface and passive corrosion to the stem surface. This raises concern with the use of large heads on conventional 12/14 tapers. Female gender was an independent risk factor of failure. Metal ion levels remain a useful aspect of the investigation work up but in isolation are not predictive of failure

In vivo and in vitro studies of ceramic on ceramic (COC) bearings have demonstrated that swing phase microseparation followed by the impact of the femoral head on the superior acetabular insert rim leads to accelerated wear. However, resultant wear remained low. The wear of ceramic on polyethylene (COP) and metal on metal (MOM) couples under swing phase microseparation is unknown, this study aimed to compare the wear of these total hip replacements under standard and microseparation conditions. A physiological hip simulator was used, loads and motions were applied to approximate in vivo conditions. Microseparation was achieved by displacing the femoral head inferiorly during swing phase, the head contacted the inferior cup rim and was laterally displaced. On heel strike the head contacted the superior cup rim prior to relocation. Components (as shown in table 1) were tested for 5 million cycles, at a frequency of 1 hertz in 25% (v/v) new born calf serum. Under standard conditions, wear of COC and MOM bearings was significantly lower than wear of COP couples. Under microseparation conditions the COC and MOM wear increased by 4 and 25 times respectively. Microseparation conditions reduced wear of COP couples by a factor of 4. Creep deformation and damage to the UHMWPE cup rim was observed, however, wear remained low. It is postulated that this reduction in polyethylene wear is due to the separation of the components in swing phase improving the entrapment of lubricant, hence wear is reduced via a squeeze film lubrication mechanism

Background: There is a paucity of published data with regard to the wear of failed metal on metal (MoM) resurfacing devices. Materials and Methods: MoM components retrieved from patients from two independent centres experiencing failure secondary to ARMD were analysed using a Mitutoyo Legex 322 coordinate measuring machine (CMM) which has an accuracy of 0.8 microns. Between 4000 – 6000 points were taken on each explant, dependent on the size of the bearing surface. Maximum wear depths and total volumetric wear were calculated. These values were compared to those from control samples retrieved following uncomplicated fractures/femoral collapse secondary to avascular necrosis (after calculating equivalent yearly wear rates). Results: 58 ARMD components were analysed. This included 22 36mm MoM THRs (DePuy Pinnacle), 28 DePuy ASRs and 8 Zimmer Duroms. There were 30 resurfacing fracture/avascular necrosis controls. Volumetric wear rates and maximum wear depths of ARMD resurfacing components were significantly greater than the resurfacing control group for both the ASR and Duroms (p< 0.05) however 2 ARMD components exhibited similar amounts of wear compared to controls. Wear rates of the ARMD THR group were significantly lower than the ARMD resurfacing group (p< 0.05). Conclusions: Increased articular wear is associated with an increased incidence of local adverse effects including tissue necrosis, joint effusions and fractures. However, there are a minority of patients who can develop tissue necrosis in the absence of accelerated wear, implying a spectrum of sensitivity This is reflected in the incidence of ARMD in the patient groups at the main study centre: > 5% in the ASR group and approx 1% in the THR group. We believe this indicates a failure of adequate lubrication and the resultant negative effects in larger bearing devices

Retrieval analysis offers a direct insight into in vivo wear mechanisms. However, the 3D measurement of wear patch characteristics on spherical highly reflective bearings has been difficult. An instrument based on an optical technique has been developed over the past 3 years. It is capable of scanning metallic head and cup in a single measurement, within minutes, at a resolution of 20 nm. From the cloud of 3D points obtained during scanning (typically 35,000 To 1,000,000), a 3D image of the measured part can be obtained. The associated computer program allows for sphericity, roughness, radius and local radius to be calculated, and surface maps of the 3D model can easily be plotted. Both head and cup of two failed MoM resurfacing devices, a wear simulator test couple and intact components were analysed using the new technique. A successful McKee Farrar head (20 years in vivo) was also scanned. Results were compared with traces obtained on a Mitutoyo RA 300 roundness machine (resolution 0.01 microns). 3D maps of the bearing surfaces of MoM devices were obtained. The maximum linear wear values on heads were 2.5 microns, 99 microns 53.5 microns and 298 microns for the simulator sample, the McKee Farrar head and the two failed resurfacing devices respectively. The corresponding maximum linear wear values on cups were 11 microns, 529 microns and 645 microns for the simulator sample and the two failed resurfacing devices respectively. These results were in good agreement with results obtained on the Mitutoyo machine. Contrary to other worn samples, the two latter cups showed that the cup had worn on the edge of the bearing surface. This resulted in an oval shaped wear patch on the head. For the McKee Farrar device and the simulator device, the wear patch was away from the edge and the outline of the wear patch was circular in shape. This novel technique has allowed for high resolution 3D mapping of the full bearing surfaces on successful McKee Farrar device and on more recent resurfacing devices. Further studies are required. However, the results suggest that component positioning is paramount to wear performance of metal on metal devices

The authors report their preliminary experience with a minimum of one year follow –up of hydroxyapatite coating as the means of fixation of the femoral head in hip resurfacing. Between Dec 2003 and Dec 2004, of the 23 cases performed by the senior author,22 were available for follow up,15 were women (68.2%) and 7 were men (31.8). The femoral and acetabular components of the uncemented version of the CORMET 2000(Corin,Cire ncester,UK) were used. The surgical approach was the Hardinge approach in all cases. Patients were assessed pre-operatively for pain and function,using the Harris Hip Score. Post operatively they were assessed in clinic with x rays at 6 weeks,6 months and annually thereafter. X rays were evaluated for pre and post op neck shaft angle,giving an indication of varus or valgus placement of the head prosthesis. The lateral view was assessed to reveal anterior or posterior tilting of the prosthesis. Neck thinning was evaluated by measuring the ratio of the metal cup and bony neck diameters at the cup neck junction, recorded post op and at one year. None of the femoral implants were placed in varus. Only one case had inferior notching, which had remodelled at one year. In the lateral view none of the cups showed a displacement of more than ten degrees in the AP direction. There were no stem lucencies or signs of femoral implant migration in any of the cases. None of our cases showed neck thinning (change in ratio greater than 10%). Uncemented femoral implant in a metal on metal resurfacing hip replacement appears to perform well and shows no catastrophic problems at the short term one year follow up. Longer follow up studies are necessary

The purpose of this study is to identify clinical and radiographic results of 78 uncemented total hip arthroplasties using Metasul. ®. metal on metal bearings with Wagner standard cup and proximal hydroxyapatite coated CLS stem. Mean age was 39 years and average follow-up period was 11.7 years. Mean Harris hip score had improved from 51.4 points preoperatively to 95.2 points finally. There were 2 hips with progressive osteolysis around the acetabular cup. Of them, one hip was revised due to loosening of the cup, and the other was observed because of patient’s refusal to revise. In histopathologic findings on osteolytic area, a lot of macrophage phagocytizing metal debris and perivascular lymphocyte infiltration were found. Immunohistochemical analysis suggested delayed metal hypersensitivity. Serum cobalt levels in hips with osteolysis were not higher than those in hips without osteolysis. Early osteolysis with sudden onset of groin pain in few hips remains a concern

The purpose of the present study was to analyze the-clinical and radiographic factors which determine the enduring fixation of metal on metal hybrid surface arthroplasty. The first 500 hips (in 436 patients) of a consecutive series of over 700 Conserve® plus were reviewed clinically and radiographically. The patients were 48.6 years-old in average, 74% were male and the dominant etiology was idiopathic osteoarthritis (64.6%). All femoral components were cemented but the femoral metaphyseal stem was cemented in 112 hips and press-fit in the remaining 388. Average follow-up was 4.8 years (range, 2.7 to 7.8 years). Eighteen hips were converted to a THR, 11 of them for aseptic loosening of the femoral component at an average follow-up of 40.5 months. Put in positives mention fx and loose incidence, survor ship details of loose and fx for other At last review, 14 hips presented metaphyseal stem radiolucencies and 16 hips (3.2%) showed a narrowing of the neck of 10% or more at the interface with the femoral component. None of the components with cemented stems showed femoral radiolucencies, neck narrowing, or were revised for aseptic loosening. Cementing the femoral stem significantly (p = 0.013) reduces the chances of early femoral failure or appearance of a metaphyseal stem radiolucency. Risk factors for loosening or radioluciences included cysts > 1 cm, small femoral head size, female gender, early cases (before improved acrylic fixation including femoral suctioning measures were instituted) and reduced stem shaft angle. Metal-on-metal surface arthroplasty provides a stable, bone conserving, low morbidity and wear resistant prosthetic solution well suited for young and highly active patients

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

Introduction. The biological pathways responsible for adverse reactions to metal debris (ARMD) are unknown. Necrotic and inflammatory changes in response to Co-Cr nanoparticles in periprosthetic tissues may involve both a cytotoxic response and a type IV delayed hypersensitivity response. Our aim was to establish whether differences in biological cascade activation exists in tissues of patients with end-stage OA compared to those with aseptic loosening of a metal on polyethylene (MoP) THR and those with ARMD from metal-on-metal (MoM) THR. Patients & Methods. A microarray experiment (Illumina HT12-v4) was performed to identify the range of differential gene expression between 24 patients across 3 phenotypes: Primary OA (n=8), revision for aseptic loosening of MoP THR (n=8) and ARMD associated with MoM THR (n=8). Results were validated using Taqman Low Density Array (TLDA) selecting the top 36 genes in terms of fold-change (FC)>2 and a significant difference (p<0.05) on ANOVA. Pathways of cellular interaction were explored using Ingenuity IPA software. Results. There is a similar pattern of gene expression between MoP and MoM phenotypes versus primary OA across 33,777 genes. One hundred and thirty significantly differentially expressed genes across 3 phenotypes were identified. Fifteen pathways were associated with differentially expressed genes between MoP and MoM phenotypes. TLDA demonstrated qualitative mirroring of the expression pattern observed in the microarray and consistency in the direction of change for individual genes. Discussion. There were no signature pathways in which multiple genes are differentially expressed such that inferences between the contributions of innate macrophage and adaptive T-cell responses can be made. TIMP3 & MMP12 were consistently identified in 15 pathways that were associated with differential gene expression between MoP and MoM phenotypes. Conclusion. Analyses of the expression of individual genes such as PRG4 (lubricin) have demonstrated patterns that may provide avenues for further research into biomarkers for periprosthetic osteolysis and ARMD

Using a femoral head from one manufacturer on the stem of another manufacturer poses the risk that the taper interface between the components do not contact correctly and the performance of the joint will be impaired. The cohorts in this study are a combination of modular Birmingham Hip Resurfacing (BHR) and Adept femoral heads on CPT stems. The study reviews the geometry of the taper interfaces to establish if the taper clearance angles was outside of the normal range for other taper interfaces. In addition the rates of material loss from the bearings and taper and a ranking of the stem damage were reviewed to determine if the levels of loss were above that seen for other similar joints.

The material loss analysis demonstrated that the rates or levels of loss from the bearings, taper and stem are no different to levels published for manufacturer matched joints and in many cases are lower. The results demonstrate that the taper clearance angles for the mixed manufacturer joints (BHR-CPT: 0.067 to −0.116, Adept-CPT: 0.101 to −0.056) were within the range of other studies and manufacturer matched clearances (0.134 to −0.149).

Using components from different manufacturers has not in this instance increased the level of material loss from the joints, when compared to other similar manufacturer matched joints.

On hundred and ninety unselected patients, mean age 62(SD12.8) were operated upon by one surgeon, using same approach. HSS improved from 33 to 75 post-operatively, the low figures reflecting a high percentage of Charnley C patients (71%). There was a 5% mortality rate from unrelated causes. Early complications included a 2.97% femoral fracture rate within 4–8 weeks of surgery (analysis showed no relation between implant position, BMI, age or Charnley classification, but there was correlation between high level of satisfaction and early weight bearing). There was one infection and one dislocation. Late complications included 3 periprosthetic fractures, 3 dislocations and 2 aseptic cup failures. However, 30% of patients developed groin pain, increasing stiffness and clunking at 1–2 years following surgery. These patients were investigated with an ultrasound scan. 28 patients (14%) had an effusion and were aspirated. Chrome and cobalt levels in synovial fluid, blood and urine were very high. 13 patients have been revised. 1 showed infection, 10 showed metal allergy and 2 a mixed picture of allergy and foreign body reaction. In our MOM database (762 hips including the current study) a total of 35 patients were revised for similar problems. Two distinct histological finding were observed. Metal allergy occurred independently of cup angle. The implants were well fixed; there was tissue necrosis and histological evidence of ALVAL. There was no infection or metalosis. FB reaction occurred more frequently when the cup was open. The Implants were loose; there was naked eye evidence of metalosis and metallic particles seen on light microscopy. We concluded that Birmingham/Freeman Hybrid had high complication rate without significant functional superiority, and other MoM devises shared similar complication. Both Metal allergy and FB reaction can occur in MOM THR. Ultra sound is a good screening tool in symptomatic patients

Introduction:

The awareness of MoM hips in the general public, one would expect, to be good, given the media coverage. This study aims to look at the perceptions and knowledge of patients who have already got a MoM arthroplasty.

Aim of the study: To evaluate the results of metal-on-metal resurfacing hip arthropalsty in young patients

Materials and Methods: Between February 2000 and December 2004, this operation was performed in 181 patients (205 hips) using the posterior approach. The main indications were osteoarthritis, osteonecrosis, hip dysplasia, post-traumatic arthritis, perthe’s disease and slipped capital femoral epiphysis. There were 142 males and 39 females aged 26 to 68 years (average 47.4 years). 136 patients had a minimum 3 year follow-up (range 1–5 years). Clinical and radiological evaluation was performed at 3 months, 1 year, 2 years and 5 years from time of surgery. All patients were scored using the Charnley’s modification of Merle d’Aubigne score preoperatively and at last follow-up. Radiological evaluation included grading acetabular and femoral zones for loosening, determining stem-shaft angle, hip ratio. The endpoint for outcome evaluation was revision which was two in this series. Survivourship analysis was performed by Kaplan-Meier analysis. The results in our patients were encouraging with most returning to sporting activities at an average of 12 months. 1 patient with bilateral hip resurfacing had evidence of osteolysis after surgery and had occasional hip pain until last follow-up. Complications like neck fracture, heterotrophic ossification were not seen in our series.

Conclusion: Early results of metal-on-metal resufacing arthroplasty in our series are encouraging. Continued follow-up and evaluation remains important to determine the long term results of this operation.

Introduction: Metal/metal total hip arthroplasties (THA) with improved qualities of the alloys and encouraging midterm clinical results are widely used. Hyperergic reactions have been observed in revision tissues in a series of failures. This study examined synovial fluids of patients with aseptic loosening of THA from metal/metal and ceramic/polyethylene endoprostheses or arthritis of the hip by analysis of various released cytokines. Materials and Methods: The aspirations of synovial fluids from 11 patients with arthritis of the hip, 6 THA revisions with ceramic polyethylene articulations, and 22 metal/metal articulations were retrieved. 15 of the 22 cases showed lymphocytic infiltration in the histologies. The aspirates were examined with a commercially available assay using a Multiplex Reader. The interleukins Il-1 beta, -2, -5, -6, -10, -12, -13, -15,-17 and IL-1 receptor antagonist (Il-1ra) were measured. Further G-CSF, GM-CSF, IFN gamma, MIP 1 beta, MIP alpha, MCP 1, and TNF alpha were assayed. Results: Samples from patients with aseptic loosenings showed increased Il-10 and MCP compared to osteoarthritis. TNF alpha, MIP alpha, and Il-1β were increased in metal/metal THA. Il-5, Il-12, Il-13 and Il-17 were only increased in patients with lymphocytic reactions, but not in ceramic/polyethylene articulations. GM-CSF, G-CSF, IFN gamma, Il-1ra Il-2, and Il-6 were only elevated in THA with lymphocytic reactions compared to metal/metal cases without. Diskussion: Aspirates from aseptic loosened THA are important diagnostic tools. The data showed a distinctly different cytokine profile joint fluids in aseptic loosenings of metal/metal THA vs. ceramic-UHMWPE articulations and fluids from osteoarthritis patients. The data may contribute to establish a cytokine profile to determine failures due to lymphocytic infiltrations before revision of metal/metal articulations