An increase in metal ion levels is seen after implantation of all MoM hip prosthesis due to release from the surface directly, more so during articulation and corrosion of the bearing surfaces. The bearing surfaces in MoM prosthesis consist of cobalt, chromium and molybdenum. Several case-reports of cobalt toxicity due to a MoM prosthesis have been published in the last decade. Cobalt intoxication may lead to a variety of symptoms: neuro-ocular toxicity (tinnitus, vertigo, deafness, blindness, convulsions, headaches and peripheral neuropathy), cardiotoxicity and thyroid toxicity. Nausea, anorexia and unexplained weight loss have been described. Systemic effects from metal ions even with well functioning implants or with ion concentrations lower than those associated with known adverse effects may exist and warrant investigation. The aim of this study is to investigate self-reported systemic complaints in association with cobalt ion concentrations in patients with any type of MoM hip prosthesis. A cohort study was conducted. Patients with both unilateral and bilateral, resurfacing and large head metal on metal total hip arthroplasties were included for the current study. Blood metal ion concentrations (cobalt and chromium) were measured by inductively coupled plasma mass spectrometry (ICP-MS). Based on the known cobalt toxicity symptoms of case-reports and toxicology reports a new non-validated questionnaire was developed. questions were subdivided in general questions/symptoms, vestibular symptoms, neurological symptoms, emotional health and cardio- and thyroid toxicity symptoms. Independent samples T test, Fishers Exact Test and Pearsons (R) correlation were used. Analysis was performed on two groups; a low cobalt ion concentration group and a high cobalt ion concentration group A total of 62 patients, 36 (58%) men and 26 (42%) women, were included with a mean age at surgery of 60.8 ± 9.3 years (41.6 – 78.1) and a mean follow up of 6.3 ± 1.4years (3.7 – 9.6). In these patients a total of 71 prosthesis were implanted: 53 unilateral and 9 bilateral. Of these, 44 were resurfacing and 27 large head metal on metal (LHMoM) total hip arthroplasties. Mean cobalt and chromium ion concentrations were 104 ± 141 nmol/L (9 – 833) and 95 ± 130nmol/L (6 – 592), respectively. Based on the different thresholds (120 – 170 or 220 nmol/L) the low cobalt ion concentration group consisted of 44 (71%), 51 (82%) or 55 (89%) subjects respectively. No differences were found in general characteristics, independently of the threshold. The composite score of vestibular symptoms (vision, hearing, tinnitus, dizziness) was significantly higher (p < .050) in all high cobalt ion concentrations groups, independent of the threshold value This study aimed to detect a trend in self-reported systemic complaints in patients with metal-on-metal hip arthroplasty due to raised cobalt ion concentrations. Vestibular symptoms were more common in high cobalt ion concentration groups independent of the three threshold levels tested. The upper limit of acceptable cobalt ion concentrations remains uncertain. With regards to proactively inquired, self-reported symptoms the threshold where effects may be present could be lower than values currently applied in clinical follow-up. It is unknown what exposure to elevated metal ion concentrations for a longer period of time causes with aging subjects. Further research with a larger cohort and a more standardized questionnaire is necessary to detect previously undiscovered or under-reported effects

The biological reaction in metallosis and pseudotumor generation after metal on metal total hip arthroplasty or corroding metal implants remains unsettled. Clinically, still lethal cases appear with massive bone loss and metal ions are suspected to be responsible for this inflammatory reaction, solid metal wear particles instead are usually not observed in the common literature. The aim of this study was to compare the biological reactions of metal ions and metal wear particles in a murine in vivo model. Metal ions (CoCr), metal particles (CoCr), polyethylene particles (UHMWPE) and phosphate buffered saline (PBS) were injected into the left knee joint of female BALB/c mice. 7 days after injection, the microcirculation was observed using intravital fluorescence microscopy, followed by euthanasia of the animals. After the assessment of the knee diameter, the knees underwent histological evaluations of the synovial layer. Throughout all recorded data, CoCr particles caused higher inflammatory reactions compared to metal ions and UHMWPE particles. The mice treated with the solid particles showed enlarged knee diameters, more intensive leukocyte–endothelial cell interactions and an elevated functional capillary density. Pseudotumor-like tissue formations in the synovial layer of the mice were only seen after the exposition to solid CoCr particles. Even if the focus of several national guidelines concerning metallosis and pseudotumor generation is on metal ions, the present data reveal that solid CoCr particles have the strongest inflammatory activity compared with metal ions and UHMWPE particles in vivo

Introduction. Failure of metal on metal (MOM) total hip arthroplasty (THA) and resurfacing arthroplasty (HRA) due to development of adverse local tissue reaction (ALTRs) is a significant problem. The prevalence of ALTRs in asymptomatic MOM arthroplasty patients is highly variable. The purpose of this prospective, longitudinal study was to: 1) determine MRI ALTR prevalence in patients with HRA; 2) determine if patients with HRA have a greater rate of MRI ALTRs compared to control patients with ceramic on poly (COP) THA; and 3) evaluate changes in patient reported outcomes between these implant designs. Methods. Following IRB approval with informed consent, self-reported asymptomatic primary COP and HRA patients greater than one year post arthroplasty were evaluated with 4 annual (TP1–4) MRIs using a standardized protocol and serum ion level testing. Morphologic and susceptibility reduced images were acquired for each hip and evaluated for synovial thickness, volume, capsule dehiscence and the presence of ALTR. Patient reported outcomes were evaluated by Hip Disability and Osteoarthritis Outcome Scores (HOOS). Analyses were performed to detect differences of synovial thickness and volume, and HOOS subgroups between and within bearing surfaces at each time point and over time, and to compare the time to and the risk of developing MRI ALTR. Analyses were adjusted for age, gender, and length of implantation. Results. 86 hips were evaluated at the initial time point (TP1): HRA, n=41, age=58±8 y.o., 34/7 (M/F); COP, n=45, age=65±9 y.o., 22/23 (M/F). The mean synovial volume of the subjects was similar at TP1, and the synovial volume in HRA subjects increased significantly from TP1 to TP4 (mean volume difference=9 cm3, p=0.031) while COP subjects displayed a minimal increase from TP1 to TP4 (mean volume difference =0.3 cm3, p=0.9). The synovial volume in HRA subjects tended to be larger and with greater variability than COP subjects at TP4 (HRA=15±58 cm3; COP=6 ±10 cm3, p=0.3). By TP4, MRI ALTRs developed in 13/41 HRA subjects (mean time to ALTR=1.5 yr) compared to 2/25 COP subjects (mean time to ALTR=2.0 yr), p=0.001. While risk of MRI ALTRs in HRA subjects was 9.9 times the risk in COP subjects (p=0.07), 68% of HRA subjects did not have an MRI ALTR present. Significant differences of [Co] and [Cr] in HRA subjects with MRI ALTR present were not detected at 2/4 time points and 1/4 time points, respectively, and there were no significant differences in ion levels in the COP group. The HOOS sub-scores of Pain and Activity of Daily Living scores of HRA subjects were similar to COP subjects, and HRA subjects had better Sporting Ability than COP subjects at all time points. HRA subjects had higher Symptoms at TP1 (p=0.016) but both cohorts had high scores (HRA=92.3/100; COP=87.7/100). Initially dehiscent posterior capsules of HRA subjects (9%) tended not to resolve (10/11, 91%), while dehiscent COP subjects (15%) had greater resolution (6/22, 27%). The presence of osteolysis was limited (HRA: 6/41; COP: 3/45; p=0.101). Conclusion. A greater synovial volume and higher rate of MRI ALTRs was found in HRA subjects, while the patient symptomatology via HOOS remained slightly better in HRA subjects than COP subjects, suggesting a poor association between MRI ALTRs and symptoms. The presence of posterior decompression of the posterior capsule into the bursa alone was not necessarily indicative of an ALTR, and is likely a normal postoperative finding. The inconsistent findings of the serum ion level testing further supports MRI as a non-invasive imaging modality capable of assessing peri-prosthetic soft tissue complications, and should be considered as part of the routine patient follow up to allow early detection and monitoring of ALTRs

Adverse reaction to metal debris (ARMD) is well recognised as a complication of large head metal on metal total hip replacement (THR) leading to pain, bone and tissue loss and the need for revision surgery. An emerging problem of trunnionosis in metal on polyethylene total hip replacements leading to ARMD has been reported in a few cases. Increased metal ion levels have been reported in THR's with a titanium stem and a cobalt chrome head such as the Accolade-Trident THR (Stryker). We present 3 cases of ARMD with Accloade-Trident THR's with 36mm cobalt chrome head and a polyethylene liner. Metal ion levels were elevated in all three patients (cobalt 10.3 – 161nmol/l). Intraoperative tissue samples were negative for infection and inflammatory markers were normal. Abnormal fluid collections were seen in all three cases and bone loss was severe in one patient leading to a proximal femoral replacement. Histology demonstrated either a non-specific inflammatory reaction in a case which presented early or a granulomatous reaction in a more advanced case suggesting a local foreign body reaction. All patients had improved symptoms post-operatively. 1 patient who had staged bilateral Accolade-Trident THR's required revision of both THR's. ARMD in metal on polyethylene THR's with a titanium stem represents a potential emerging problem. Further studies are required to assess whether these occurrences are rare or represent the tip of an iceberg

Background. Fretting corrosion at the junction of the modular head neck interface in total hip arthroplasty is an area of substantial clinical interest. This fretting corrosion has been associated with adverse patient outcomes, including soft tissue damage around the hip joint. A number of implant characteristics have been identified as risk factors. However, much of the literature has been based on metal on metal total hip arthroplasty or subjective scoring of retrieved implants. The purpose of this study was to isolate specific implant variables and assess for material loss in retrieved implants with a metal on polyethylene bearing surface. Methods. All 28mm and 32 mm femoral heads from a 12/14 mm taper for a single implant design implanted for greater than 2 years were obtained from our institutional implant retrieval laboratory. This included n = 56 of the 28 mm heads (−3: n = 10, +0: n = 24, +4: n = 13, and +8: n = 9), and n = 23 of the 32 mm heads (−3: n = 2, +0: n = 8, +4: n = 1, and +8: n = 6). There were no differences between groups for age, gender, BMI, or implantation time. A coordinate measuring machine was used to acquire axial scans within each head, and the resulting point clouds were analyzed with a custom Matlab program. Maximum linear wear depth (MLWD) was calculated as the maximum difference between the material loss and as-machined surface. Differences in MLWD for head length, head diameter, stem material, and stem offset were determined. Results. Within the 28 mm head diameter group, there was no difference (p = 0.65) in MLWD between head lengths (−3: 4.0 ± 1.7 µm, +0: 10.4 ± 15.2 µm, +4: 4.4 ± 1.7 µm, +8: 4.3 ± 1.8 µm). There was no difference (p = 0.12) between the 28 mm (6.7 ± 10.9 µm) and 32 mm (5.5 ± 6.2 µm) head diameters. There was also no difference (p = 0.97) between titanium (7.3 ± 11.4 µm) or cobalt-chromium (5.9 ± 5.6 µm) stems, and no difference (p = 0.20) between regular (7.0 ± 10.0 µm) or high-offset (5.7 ± 8.0 µm) stems. Discussion. The development of fretting corrosion at the head neck junction of metal on polyethylene total hip replacements is of substantial clinical importance. In a single taper design, head diameter, head length, stem material and stem offset were all not found to be contributory to magnitude of wear depth. This is in contrast to current literature, which is controversial regarding the role of head diameter, but head length is thought to be contributory. However, as this study using precise tools does not illustrate these proposed biomechanic factors of fretting corrosion, other factors influencing tribocorrosion such as trunnion surface finish, flexural rigidity, interface geometry and biochemical factors may need to be considered

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.

Background. Large head metal on metal total hip arthroplasty MOM THA have been consistently shown substantial improvement in wear performance compared with metal on polyethylene articulations. Large diameter femoral heads theoretically can reduce dislocation risk by increasing range of motion before impingement, increasing prosthetic jump distance. However, early failure associated with adverse local tissue reactions (ALTRs) to metal debris is an emerging problem after MOM THA. The purpose of this study was to evaluate mid-term results of MOM THA. Materials and Methods. Twenty-five patients, 28 hips were included in this study. The average age of the patients at the time of surgery was 66.9 years. Three patients were men and 22 were women. MOM THAs were performed using 28 PINNACLE Cup system (DepPuy) (C-STEM: 23, S-ROM: 5) with posterior approach and head size of 36mm. Twenty-five primary THAs due to osteoarthritis in 22 cases and rheumatoid arthritis (RA) in one, and two revisions due to recurrent dislocation THA patients, were performed. The average follow up was 56.7 months. Evaluation items are JOA score, cup anteversion /lateral opening angle, and complications. Indication of the system were applied for patients with high risk of dislocation such as recurrent dislocation in primary and/or THAs, posterior pelvic tilt, elderly, RA and mental disorders. Results. The average JOA score improved from 48.3 (range: 26–77) preoperatively to 88.3 (range: 55–100) postoperatively. The average cup anteversion was 21.7 degrees (range: 2–38) and average lateral opening was 45.5 degrees (range: 37–60). Three patients (12%) developed dislocation. Two patients (8%) required reoperations from the deep infection. One female patient (4%) remained hip pain and was suspected pseudotumor / ALTR, which was confirmed by computed tomography and magnetic resonance imaging. Conclusion. Large femoral head MOM THA was useful for patients with recurrent dislocation in revision THA. However, three patients developed dislocation in primary THAs (12% of primary cases), which suggested that the more accurate placement of the acetabular cup is important even in the large diameter cup. Although only one case (4%) revealed ALTR, however, continuous careful follow-up would be necessary in the MOM system

Metal on metal total hip arthroplasty (MoM THA) provides the potential improvement in articular wear. However, several adverse events including pseudotumor had been reported. Magnetic resonance imaging (MRI) was considered to be the proposal tool for detection of pseudotumor after MoM THA. In this study, we performed the screening of pseudotumor after MoM THA using the MRI. We studied 43 patients with M2a Magnum® (Biomet) and 34 patients with M2a Taper® (Biomet) of MoM THA from December 2009 to December 2011 with follow-up of 2.5 years (2.0–4.0 years) after surgery. MRI assessments were performed at a mean of 2.1 years postoperatively. Pseudotumor findings were graded using Anderson classification (Skeletal Radiol, 2011: 40; 303). Age, sex, height, weight, Harris Hip Score, EQ5D satisfaction score, UCLA activity score, and blood metal ion levels were evaluated. The prevalence of pseudotumor was 27.2%; 56 normal (Type A), 13 mild (C1), 8 moderate (C2) and none were graded severe (C3). Weight and BMI in the mild group was significantly higher than those in normal. There was no significant difference in age, sex and height among these groups. With regard to Harris Hip score, pain and ROM score in moderate group was significantly lower than that in normal and mild group. EQ5D satisfaction score and UCLA activity score showed not significant differences among groups. 3.01±3.32 μg/L of blood cobalt ion levels in the moderate groups was significantly higher than 0.97±0.64 μg/L in normal group. Blood cobalt ion levels of 1 mild and 2 moderate were over the threshold of 7 μg/L. These patients were implanted with M2a Taper, not M2a Magnum. 14% of the prevalence in the patients with M2a Magnum was significantly lower than 41% in the patients with M2a Taper. No revision surgeries were required. The patients with no pseudotumor did not show the increase of blood metal ion. Contrarily, several patients showed the increase of blood metal ion in case of detecting pseudotumor. MRI assessments were useful for screening of pseudotumor after MoM THA and blood metal ion should be investigated for patients with mild and moderate pseudotumor in MoM THA

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

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. Metal on metal hip arthroplasty continues to be controversial. Emerging evidence suggests that there are multiple modes of failure, and that the results of revision surgery are influenced by host and implant factors. Methods. This study compares a single surgeon series of hip resurfacings (Birmingham Hip Resurfacing {BHR}) and large diameter metal on metal total hip replacements (LDMOMTHR). Primary outcome measures included survival rates, failure secondary to histologically identified Adverse Reaction to Metal Debris (ARMD), and patient reported outcome measures (Oxford Hip Score {OHS}) following revision. Between 1999 and 2005, 458 BHR and 175 LDMOMTHR were performed. At latest review 43 BHR's (9.4%) and 28 LDMOMTHR's (14%) have been revised. Results. Failure secondary to ARMD was significantly greater in LDMOMTHR compared to BHR failures (89% and 16% respectively). Histology demonstrated a higher Aseptic Lymphocytic Vascular and Associated Lesions (ALVAL) score in the LDMOMTHR failures than the BHR failures (8.6 LDMOMTHR, 6.3 BHR). Patient reported outcomes were better following revision for failed BHR compared to LDMOMTHR. There was no difference between the revision cohorts for cup inclination, metal ion levels and gender. Failure of the BHR has predominantly been due to those causes unique to resurfacing such as avascular necrosis and fracture. In our series, aggressive ALVAL was unusual and clinical outcome following revision was superior compared to LDMOMTHR failures. The likely mechanisms that are responsible for the differences in outcome and the clinical implications will be discussed

Background

Revision surgery for failed metal-on-metal (MOM) total hip arthroplasty (THA) or hip resurfacing (HR) has been a challenge. Previous studies have reported high failure and complication rates, including dislocation, infection, aseptic loosening and lower patient satisfaction. Options for revision depend on the integrity and stability of the femoral and acetabular components. When both components fail, full revision is required; however, when the acetabular component remains well fixed and oriented, only the isolated femoral component revision can be performed. Dual mobility components can be utilized to match the size to the inner diameter of the metal cup. With the dual mobility implant, the morbidity and complications associated with cup revision are avoided while maintaining a natural femoral head size and potentially increasing range of motion and stability postoperatively compared to standard THA.

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:. Large diameter metal on metal total hip arthroplasty (MOM THA) have shorter lengths of implantation due to increased failure caused by wear either at the articulating surface as well as the taper-trunnion interface. Taper-trunnion wear may be worse in large diameter MOM THA due the increased torque at the taper-trunnion interface. However little has been done to understand how differences in taper-trunnion geometry and trunnion engagement effects wear. The purpose of this study was to (1) measure the differences in taper geometry and trunnion engagement on the head-taper of 11/13, 12/14, and Type 1 taper designs and (2) to determine if taper geometry affects fretting, corrosion, and wear at the taper interface. Methods:. We identified 54 MOM THA primary revision implants with head diameters greater than 36 mm from our retrieval archive. Patients' charts were queried for demographic information and pre-revision radiographs were measured for cup inclination and cup anteversion. To measure taper geometry and wear the head tapers were imaged using Redlux©. The point clouds obtained from this were analyzed in Geomagic©. Taper angles and contact length where the trunnion engaged with the female taper of the head-tapers were measured. The diameter of the taper at the most distal visual area of trunnion engagement was also measured. Best fit cones were fit to the unworn regions to approximate the pristine surface. Differences between the raw data and the unworn surface were measured and volumetric wear rates were calculated. Fretting and corrosion of the head-taper was graded using the Goldberg Scoring. Results:. Geometric differences were found between the three designs with the Type 1 being the narrowest with an average taper angle of 3.97 ± 0.09° and an average distal diameter of 12.42 ± 0.35 mm; 11/13 was the second narrowest with a taper angle of 5.97 ± 0.03° and a distal diameter of 13.13 ± 0.27 mm. The widest taper was 12/14 with a taper angle of 5.58 ± 0.21° and a distal diameter of 13.91 ± 0.35 mm. Contact lengths were greatest for 11/13 tapers, 18.96 ± 1.51 mm, then 12/14, 13.31 ± 3.46 mm and least for Type 1, 11.98 ± 4.44 mm (Table 1). Differences in geometry did not significantly affect volumetric wear rate or corrosion but did affect fretting. Type 1 tapers had significantly lower fretting scores (2.9 ± 1.5, p < 0.05) than 12/14 tapers (5.0 ± 1.6) and 11/13 tapers (6.4 ± 2.1). Discussion:. We were able to measure determine geometric differences between three common taper designs which may affect taper damage. Tapers which are narrower and have less contact length (i.e. Type 1) had less head-taper fretting than those which are wider and have longer contact lengths. This may be a function of less surface of the trunnion contacting the head taper interface. While we could not demonstrate any differneces in trunnion wear rates among taper types, volumetric wear and corrosion may be independent of taper geometries

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

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

There has been much discussion and controversy in the media recently regarding metal toxicity following large head metal on metal (MoM) total hip replacement (THR). Patients have been reported as having hugely elevated levels of metal ions with, at times, devastating systemic, neurolgical and/or orthopaedic sequelae. However, no direct correlation between metal ion level and severity of metallosis has yet been defined. Normative levels of metal ions in well functioning, non Cobalt-Chrome hips have also not been defined to date. The Exeter total hip replacement contains no Cobalt-Chrome (Co-Cr) as it is made entirely from stainless steel. However, small levels of these metals may be present in the modular head of the prosthesis, and their effect on metal ion levels in the well functioning patient has not been investigated. We proposed to define the “normal” levels of metal ions detected by blood test in 20 well functioning patients at a minimum 1 year post primary Exeter total hip replacement, where the patient had had only one joint replaced. Presently, accepted normal levels of blood Chromium are 10–100 nmol/L and plasma Cobalt are 0–20 nmol/L. The UK Modern Humanities Research Association (MHRA) has suggested that levels of either Cobalt or Chromium above 7 ppb (equivalent to 135 nmol/L for Chromium and 120 nmol/L for Cobalt) may be significant. Below this level it is indicated that significant soft tissue reaction and tissue damage is less likely and the risk of implant failure is reduced. Hips were a mixture of cemented and hybrid procedures performed by two experienced orthopaedic consultants. Seventy percent were female, with a mixture of head sizes used. In our cohort, there were no cases where the blood Chromium levels were above the normal range, and in more than 70% of cases, levels were below recordable levels. There were also no cases of elevated plasma Cobalt levels, and in 35% of cases, levels were negligible. We conclude that the implantation with an Exeter total hip replacement does not lead to elevation of blood metal ion levels

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

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

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