In metal-on-polyethylene (MoP) THA large femoral metal heads are designed to increase stability and to reduce dislocation risk. The increased head size could lead to increased taper corrosion with the release of metal ions and adverse reactions. Using blood ion measurements, we aimed to investigate the association between femoral head size and metal-ion release after MoP THA. 96 patients were enrolled at two centers and randomized to receive either a 32-mm metal head or a 36–44 mm metal head (the largest possible fitting the thinnest available polyethylene insert). Blood metal ions and PROMs (OHS, UCLA) were measured at two- and five-year follow-ups. Both 2- and 5-year median chrome, cobalt, and titanium levels were below taper corrosion indicative ion levels. At 5 years, median chrome, cobalt, and titanium levels were 0.5 μg/L (0.50–0.62), 0.24 μg/L (0.18–0.30), and 1.16 μg/L (1.0–1.68) for the 32-mm group, and 0.5 μg/L (0.5–0.54), 0.23 μg/L (0.17–0.39), and 1.30 μg/L (1–2.05) for the 36–44 mm group, with no difference between groups (p=0.825, p=1.000, p=0.558). At 2 years, 7 (32-mm) versus 4 (36–44-mm) patients had elevated ions. At 5 years, 6 (32-mm) versus 7 (36–44-mm) patients had elevated ions. There was no difference in either OHS (p=0.665) or UCLA (p=0.831) between patients with or without elevated blood metal ions. 5 years after the insertion of MoP THAs, we found no differences in the blood metal ion levels between 32 mm heads and 36–44 mm heads and no corrosion-related revisions. As taper corrosion can debut after 5 years, there is still a need for long-term follow-up studies on the association between head size and corrosion in MoP THA

Aims. There are limited published data detailing the volumetric material loss from tapers of conventional metal-on-polyethylene (MoP) total hip arthroplasties (THAs). Our aim was to address this by comparing the taper wear rates measured in an explanted cohort of the widely used Exeter THA with those measured in a group of metal-on-metal (MoM) THAs. Patients and Methods. We examined an existing retrieval database to identify all Exeter V40 and Universal MoP THAs. Volumetric wear analysis of the taper surfaces was conducted using previously validated methodology. These values were compared with those obtained from a series of MoM THAs using non-parametric statistical methodology. A number of patient and device variables were accounted for using multiple regression modelling. Results. A total of 95 Exeter MoP and 249 MoM THAs were examined. The median volumetric loss from the MoM cohort was over four times larger than that from the MoP cohort (1.01 mm. 3. vs 0.23 mm. 3. , p < 0.001), despite a significantly shorter median period in vivo for the MoM group (48 months vs 90 months, p < 0.001). Multiple regression modelling indicated that the dominant variables leading to greater female taper material loss were bearing diameter (p < 0.001), larger female taper angles (p < 0.001), and male titanium stem tapers (p < 0.001). Conclusion. Consistent with the long-term clinical success of the device, the volumetric material loss from Exeter femoral head tapers was, in general, small compared with that from larger-diameter MoM head tapers. Cite this article: Bone Joint J 2018;100-B:1310–9

Objectives. T-cells are considered to play an important role in the inflammatory response causing arthroplasty failure. The study objectives were to investigate the composition and distribution of CD4+ T-cell phenotypes in the peripheral blood (PB) and synovial fluid (SF) of patients undergoing revision surgery for failed metal-on-metal (MoM) and metal-on-polyethylene (MoP) hip arthroplasties, and in patients awaiting total hip arthroplasty. Methods. In this prospective case-control study, PB and SF were obtained from 22 patients (23 hips) undergoing revision of MoM (n = 14) and MoP (n = 9) hip arthroplasties, with eight controls provided from primary hip osteoarthritis cases awaiting arthroplasty. Lymphocyte subtypes in samples were analysed using flow cytometry. Results. The percentages of CD4+ T-cell subtypes in PB were not different between groups. The CD4+ T-cells in the SF of MoM hips showed a completely different distribution of phenotypes compared with that found in the PB in the same patients, including significantly decreased CD4+ T-central memory cells (p < 0.05) and increased T-effector memory cells (p < 0.0001) in the SF. Inducible co-stimulator (ICOS) was the only co-stimulatory molecule with different expression on CD4+ CD28+ cells between groups. In PB, ICOS expression was increased in MoM (p < 0.001) and MoP (p < 0.05) cases compared with the controls. In SF, ICOS expression was increased in MoM hips compared with MoP hips (p < 0.05). Conclusions. Increased expression of ICOS on CD4+ T-cells in PB and SF of patients with failed arthroplasties suggests that these cells are activated and involved in generating immune responses. Variations in ICOS expression between MoM and MoP hips may indicate different modes of arthroplasty failure. Cite this article: Professor P. A. Revell. Increased expression of inducible co-stimulator on CD4+ T-cells in the peripheral blood and synovial fluid of patients with failed hip arthroplasties. Bone Joint Res 2016;5:52–60. doi: 10.1302/2046-3758.52.2000574

We compared the incidence of pseudotumours after large head metal-on-metal (MoM) total hip arthroplasty (THA) with that after conventional metal-on-polyethylene (MoP) THA and assessed the predisposing factors to pseudotumour formation. . From a previous randomised controlled trial which compared large head (38 mm to 60 mm) cementless MoM THA with conventional head (28 mm) cementless MoP THA, 93 patients (96 THAs: 41 MoM (21 males, 20 females, mean age of 64 years, standard deviation (. sd. ) 4) and 55 MoP (25 males, 30 females, mean age of 65 years, . sd. 5) were recruited after a mean follow-up of 50 months (36 to 64). . The incidence of pseudotumours, measured using a standardised CT protocol was 22 (53.7%) after MoM THA and 12 (21.8%) after MoP THA. Women with a MoM THA were more likely to develop a pseudotumour than those with a MoP THA (15 vs 7, odds ratio (OR) = 13.4, p < 0.001). There was a similar incidence of pseudotumours in men with MoM THAs and those with MoP THAs (7 vs 5, OR = 2.1, p = 0.30). Elevated cobalt levels (≥ 5 microgram/L) were only associated with pseudotumours in women with a MoM THA. There was no difference in mean Oxford and Harris hip scores between patients with a pseudotumour and those without. . Contrary to popular belief, pseudotumours occur frequently around MoP THAs. Women with a MoM THA and an elevated cobalt level are at greatest risk. In this study, pseudotumours had no effect on the functional outcome after either large head MoM or conventional MoP THA. Cite this article: Bone Joint J 2015;97-B:1481–7

Background. Adverse local tissue reactions (ALTR) in metal-on-polyethylene (MoP) total hip arthroplasty (THA) with head-neck taper corrosion is likely to be multifactorial involving implant and patient factors. However, there is a paucity of clinical data on implant parameters as predisposing factors in MoP head-neck taper corrosion. The aim of this study was to identify any potential implant factors associated with failed MoP THA due to head-neck taper corrosion. Methods. A total of 67 MoP THA patients in two groups was investigated: 1) ALTR (n=38) on MARS MRI and 2) non-ALTR (n=29) on MARS MRI. All patients had highly cross-linked polyethylene liners with cobalt-chromium femoral heads with a single head-neck modularity. Parameters compared between groups included: acetabular component orientation, femoral neck shaft angle, radiographic measurement of medial and vertical femoral offsets, limb length discrepancy, component size, femoral head offset, implant type, femoral stem alloy and taper design. Results. The occurrence of ALTR was associated with increased femoral head offset (non-ALTR vs. ALTR, 0.5 ± 3.7 vs. 4.1 ± 3.6, p = 0.008), increased radiographic femoral stem offset (35.9 ± 7.4 mm vs 40.7 ± 7.1mm, p = 0.018), and the use of TMZF alloy stems (p = 0.051). The presence of ALTR was significantly associated with higher cobalt (9.1 µg/L vs. 0.4µg/L, p=0.001) and chromium (2.6µg/L vs. 0.4µg/L). A significant correlation was identified between the serum cobalt level and the femoral stem offset (R=0.375, p=0.009). Conclusions. Although the occurrence of head-neck taper corrosion in MoP THA is likely to be an interplay between implant and patient factors, the results of this study identified increased femoral head and stem offset and the use of TMZF alloy stems as risk factors associated with clinically relevant ALTR due to head-neck taper corrosion in MoP THA patients. The study provides evidenced-based information in risk stratification of symptomatic MoP THA patients for head-neck taper corrosion. For any tables or figures, please contact the authors directly

Aims. Fretting and corrosion at the modular head/neck junction, known as trunnionosis, in total hip arthroplasty (THA) is a cause of adverse reaction to metal debris (ARMD). We describe the outcome of revision of metal-on-polyethylene (MoP) THA for ARMD due to trunnionosis with emphasis on the risk of major complications. Patients and Methods. A total of 36 patients with a MoP THA who underwent revision for ARMD due to trunnionosis were identified. Three were excluded as their revision had been to another metal head. The remaining 33 were revised to a ceramic head with a titanium sleeve. We describe the presentation, revision findings, and risk of complications in these patients. Results. The patients presented with pain, swelling, stiffness, or instability and an inflammatory mass was confirmed radiologically. Macroscopic material deposition on the trunnion was seen in all patients, associated with ARMD. Following revision, six (18.2%) dislocated, requiring further revision in four. Three (9.1%) developed a deep infection and six (18.2%) had significant persistent pain without an obvious cause. One developed a femoral artery thrombosis after excision of an iliofemoral pseudotumor, requiring a thrombectomy. Conclusion. The risk of serious complications following revision MoP THA for ARMD associated with trunnionosis is high. In the presence of extensive tissue damage, a constrained liner or dual mobility construct is recommended in these patients. Cite this article: Bone Joint J 2018;100-B:720–4

We questioned about bearing surface and infection in two populations of patients who had bilateral THA with different bearings performed in the same hospital by the same surgical team from the year 1981 to the year 2010 (mean followup 15 years; 7 to 35). 1) first population (mean age 32 years): 325 patients (650 hips) with sickle cell disease (SCD) with two different bearing on each side. 116 patients had Metal on PE (MoP) on one side and Ceramic on PE (CoP) on the contralateral; 106 patients had (CoP) and Ceramic on Ceramic (CoC); 103 patients had MoP and CoC. 2) matched control population (same age, same period) of 820 patients without co-morbidities: 354 patients had MoP and CoP; 237 had CoP and CoC; 229 had MoP and CoC. Among the 2290 hips, 3 early (less than 12 months) unilateral infections (2 in the controls, 1 in the SCD), and 59 late unilateral infections: 23 (1.4%) in 1640 THAs control, versus 36 (5.5%) in the SCD 650 THAs (P < 0.0001) during the observation period of 35 years. In control group with the Kaplan-Meier analysis, increase infections over time but different (p=0.02) for each bearing surfaces, respectively from 0% at one year to 0.4% revision (2 cases) at most recent follow-up for 466 CoC hips, from 0% to 1.1% (7 cases) for 591 CoP hips, and from 0.3% to 2.4% (14 cases) for 583 MoP hips. In sickle cell disease group MoP hips had higher risk of infection (26 among 219) when compared with CoP (9 among 222; p=0.002), and CoC (1 among 209 hips; p=0.0004); with increase over time from 1% at one year to 4% with CoP, and from 1% to 11.8% with MoP. When contralateral hip of same patient is control, PE components are more prone to infection than those involving ceramic-on-ceramic

Objectives. To quantify and compare peri-acetabular bone mineral density (BMD) between a monoblock acetabular component using a metal-on-metal (MoM) bearing and a modular titanium shell with a polyethylene (PE) insert. The secondary outcome was to measure patient-reported clinical function. Methods. A total of 50 patients (25 per group) were randomised to MoM or metal-on-polyethlene (MoP). There were 27 women (11 MoM) and 23 men (14 MoM) with a mean age of 61.6 years (47.7 to 73.2). Measurements of peri-prosthetic acetabular and contralateral hip (covariate) BMD were performed at baseline and at one and two years’ follow-up. The Western Ontario and McMaster Universities osteoarthritis index (WOMAC), University of California, Los Angeles (UCLA) activity score, Harris hip score, and RAND-36 were also completed at these intervals. Results. At two years, only zone 1 showed a loss in BMD (-2.5%) in MoM group compared with a gain in the MoP group (+2.2%). Zone 2 showed loss in both groups (-2.2% for MoM; -3.9% for MoP) and zones 3 and 4 a gain in both groups (+0.1% for MoM; +3.3% for MoP). No other between-group differences were detected. When adjusting for BMD of the contralateral hip, no differences in BMD were observed. The only significant differences in functional scores at two years were higher UCLA activity (7.3 (. sd. 1.2) vs 6.1 (. sd. 1.5); p = 0.01) and RAND-36 physical function (82.1 (. sd. 13.0) vs 64.5 (. sd. 26.4); p = 0.02) for MoM bearings versus MoP. One revision was performed in the MoM group, for aseptic acetabular loosening at 11 months. Conclusions. When controlling for systemic BMD, there were no significant differences between MoM and MoP groups in peri-acetabular BMD. However, increasing reports of adverse tissue reactions with large head MoM THR have restricted the use of the monoblock acetabular component to resurfacing only

Aims. Many case reports and small studies have suggested that cobalt ions are a potential cause of cardiac complications, specifically cardiomyopathy, after metal-on-metal (MoM) total hip arthroplasty (THA). The impact of metal ions on the incidence of cardiac disease after MoM THA has not been evaluated in large studies. The aim of this study was to compare the rate of onset of new cardiac symptoms in patients who have undergone MoM THA with those who have undergone metal-on-polyethylene (MoP) THA. Patients and Methods. Data were extracted from the Standard Analytics Files database for patients who underwent MoM THA between 2005 and 2012. Bearing surface was selected using International Classification of Diseases ninth revision codes. Patients with a minimum five-year follow-up were selected. An age and gender-matched cohort of patients who underwent MoP THA served as a comparison group. New diagnoses of cardiac disease were collected during the follow-up period. Comorbidities and demographics were identified and routine descriptive statistics were used. Results. We identified 29 483 patients who underwent MoM THA and 24 175 matched patients who underwent MoP THA. Both groups had a mean Charlson comorbidity index score of 4. There were no statistically significant differences in 30 of 31 pre-existing comorbidities. Patients undergoing MoM THA had a slightly lower incidence of cardiac failure compared with those undergoing MoP THA at three years (6.60% versus 7.06%, odds ratio (OR) 0.93, 95% confidence interval (CI) 0.87 to 0.99) and four years (8.73% versus 9.49%, OR 0.91, 95% CI 0.86 to 0.97) postoperatively, with no difference in the incidence of new cardiac failure in between the groups at five years. There was no statistically significant difference in the incidence of arrhythmia, myocardial infarction and cardiomyopathy at any time between the two groups. Conclusion. MoM THA is not associated with cardiac complications. Initial reports may have represented individual instances of cardiac disease in patients with a failing MoM articulation rather than an emerging epidemiological trend. Cite this article: Bone Joint J 2018;100-B:28–32

Introduction. Adverse local tissue reactions (ALTR) can result in devastating soft tissue and osseous destruction, while potentially increasing the risk of concomitant periprosthetic joint infection (PJI). The aims of this study were to evaluate cobalt (Co) and chromium (Cr) levels generated in simulators from metal-on-polyethylene (MoP) and ceramic-on-polyethylene (CoP) constructs, and determine their impact on native tissues and PJI risk through evaluation of human adipose-derived mesenchymal stem cells (AMSCs) and Staphylococcus epidermidis isolates. Methods. Ten hip simulator constructs were assembled with 36-mm high-offset femoral heads, highly cross-linked polyethylene liners, and titanium stems. Five constructs used CoCr femoral heads and five used ceramic. Constructs were submerged in bovine serum (BS) and run for 1,000,000 cycles. Samples of BS were collected and evaluated for CoCr concentration. Various concentrations of CoCr were chosen for further assessment of cytotoxicity and growth impact on AMSCs and S. epidermidis and compared to inert SiO2. Results. After 1,000,000 cycles, mean MoP and CoP Co concentration was 2264 ng/mL and 0.6 ng/mL, respectively (p<0.001). Mean MoP and CoP Cr concentration was 217 ng/mL and 4.3 ng/mL, respectively (p<0.001). Mean MoP Co:Cr ratio was 10. Co nanoparticles were significantly more toxic to human AMSCs than control SiO2 in a dose-response manner (p<0.001). S. epidermidis growth was not significantly impacted by Co concentrations derived from the simulators. Conclusions. MoP constructs built in ideal conditions generated substantial CoCr debris, highlighting a baseline risk with these implants that may be exacerbated by host factors or imperfect surgical technique. Evaluation of impact on AMSCs suggests that debris levels produced under ideal conditions can be cytotoxic. Additionally, these concentrations did not potentiate or inhibit S. epidermidis growth, suggesting elevated PJI rates with ALTR may be related to other factors potentially associated with tissue necrosis. For any tables or figures, please contact the authors directly

Prosthetic joint infections (PJI) are a devastating consequence in total hip arthroplasties (THA) with both significant morbidity and sometimes mortality, posing a significant health economic burden. Studies, both clinical and in-vitro have suggested possible reduction in PJI with the use of ceramic bearings. We have investigated the relationship of ceramic-on-ceramic (CoC), ceramic-on-polyethylene (CoP) or metal-on-polyethylene (MoP) bearing surface in affecting outcome of revision surgery after primary THA using data collected from National Joint Registry for England and Wales, Northern Ireland and the Isle of Man between 2002 and 2016. We used a competing risk regression model to investigate predictors of each revision outcome, such as infection, dislocation, aseptic revision and all cause revisions. The results were adjusted for age, gender, ASA grade, BMI, indication for surgery, intraoperative complications and implant data. We identified 456,457 THA (228,786 MoP, 128,403 CoC and 99,268 CoP). In a multivariable model, the adjusted risk of revision for PJI was lower with CoC (OR-0.748, p<0.001) and CoP (OR-0.775, p<0.001) when compared to MoP bearing. Additionally there was also a significant reduction in the risk of all cause revision for CoC (OR-0.918, p=0.002) and CoP (0.806, p<0.001), bearings as compared with MoP. The protective effect of ceramic bearing was predominantly seen after two years of implantation with a significant (p<0.0001) reduction of revision for PJI in both CoC (by 42.8%) and CoP (by 41.3%) group. Similarly significant effect was seen for aseptic revision beyond two years and overall all cause revision rate beyond two years reduced by 21.6% for CoC and 27.1% for CoP (p<0.001). Within the limits of registry analysis, this study has demonstrated an association between the use of ceramic bearing and lower rates of revision for all cause revisions especially infection and aseptic loosening. This finding supports the use of ceramic bearings in THA

Introduction. Numerous studies have reported on clinically significant volumes of material loss and corrosion at the head-stem junction of metal-on-metal (MOM) hips; less is understood about metal-on-polyethylene (MOP) hips. We compared the effect of bearing type (MOM vs MOP) on taper material loss for a hip system of a single design (DePuy Pinnacle). Methods. We recruited retrieved MOM (n=30) and MOP (n=22) bearing hips that were consecutively received at our centre. We prospectively collected associated clinical and imaging data. We measured the severity of corrosion and volumes of material loss at each head taper surface and used multivariate statistical analysis to investigate differences between the two bearing types. Results. The median rate of material loss for the MOM and MOP groups was 0.81 mm. 3. /year (0.01–3.45) and 0.03 mm. 3. /year (0–1.07) respectively (p<0.001). 29 out of 30 MOM hips were revised for adverse metal reactions, compared with 1 out of 22 MOP hips. Discussion. MOP hips lost significantly less material from their taper junctions than MOM hips. We suggest that the metal-metal interaction at the bearing surface of MOM hips enhances the corrosive environment at the head-stem junction. Conclusion. Our results can reassure patients with MOP Pinnacle hips that they are unlikely to experience clinically significant problems related to material loss from the taper junction

Trunnionosis, due to mechanical wear and/or corrosion at the head stem taper junction, can occur in metal on polyethylene (MOP) hip implants. In some patients this results in severe soft tissue destruction or Adverse Reaction to Metal Debris (ARMD). The amount of material required to cause ARMD is unknown but analyses of retrieved hips may provide the answer to this clinically important question. We collected implants from 20 patients with failed hips with MOP bearings, revised due to ARMD. We collected clinical, imaging and blood test data. We graded the severity of taper corrosion (1 to 4), and quantified the volume of material loss from this junction. We compared our results with previous data collected for metal-on-metal (MOM) hips. The median time to revision of the MOP hips was 51.3 (23.1–56.4) months. All head tapers were moderately to severely corroded with a median corrosion score of 4. The median (range) of total material loss at the taper of the MOP hips was 3.9 mm. 3. (2.96 – 7.85 mm. 3. ) and the material loss rate was 1.4 mm. 3. / year (0.56 – 1.82). Comparison with MOM hips revealed no significant difference in taper material loss (p=0.7344) with a median rate of 0.81 mm. 3. / year (0.01–3.45). We are the first to quantify the volume of material loss at the head taper of hip implants with MOP bearings that were revised due to trunnionosis. This data indicates that a clinically significant dose of cobalt and chromium to induce ARMD is approximately 1.4 mm. 3. / year. We have identified a clinically significant volume of taper material loss in MOP hips

A total of 397 hips were randomised to receive Metasul metal-on-metal (MoM), metal-on-conventional polyethylene (MoP) or ceramic-on-polyethylene (CoP) bearings using a cemented triple-tapered polished femoral component (MS-30). There were 129 MoM hips in 123 patients (39 male and 84 female, mean age 63.3 years (40.7 to 72.9)), 137 MoP hips in 127 patients (39 male and 88 female, mean age 62.8 years (24.5 to 72.7)) and 131 CoP hips in 124 patients (51 male and 73 female, mean age 63.9 years (30.6 to 73.8)). All acetabular components were cemented Weber polyethylene components with the appropriate inlay for the MoM articulation. Clinical evaluation was undertaken using the Harris hip score (HHS) and radiological assessments were made at two, five and seven years. The HHS and radiological analysis were available for 341 hips after seven years. The MoM group had the lowest mean HHS (p = 0.124), a higher rate of revision (p < 0.001) and a higher incidence of radiolucent lines in unrevised hips (p < 0.001). In all, 12 revisions had been performed in 12 patients: eight in the MoM group (four for infection, four for aseptic loosening, three in the MoP group (one each of infection, dislocation and pain) and one in the CoP group (infection). Our findings reveal no advantage to the MoM bearing and identified a higher revision rate and a greater incidence of radiolucent lines than with the other articulations. We recommend that patients with a 28 mm Metasul MoM bearing be followed carefully. Cite this article: Bone Joint J 2013;95-B:881–6

The bearing surface is the critical element in determining the longevity of a total hip arthroplasty. Over the past decade problems associated with bearing surfaces and modular femoral tapers have had an impact on surgeon selection of both acetabular liners and modular femoral heads. The purpose of this study was to analyse THA bearing surface trends from 2007 through 2014 using a large national database. A retrospective review of the Nationwide Inpatient Sample (NIS) database was conducted from 2007 to 2014. All patients who underwent a primary THA were identified using International Classification of Diseases, 9th edition (ICD-9) procedure codes. Bearing surface data was extracted by identifying patients with ICD-9 procedure modifier codes. Patient and hospital characteristics were recorded for each patient. Descriptive statistics were employed to characterise bearing surface trends for the following bearing surfaces: metal on polyethylene (MoP); ceramic on polyethylene (CoP); ceramic on ceramic (CoC) and metal on metal (MoM). Univariate analysis was performed to identify differences between the bearing surface groups. During the study period, 2,460,640 primary THA discharges were identified, of which 1,059,825 (43.1%) had bearing surface data available for further analysis. The breakdown of the bearing surfaces used for these THAs were as follows: MoP − 49.1% (496,713); CoP − 29.1% (307,907); CoC − 4.2% (44,823); and MoM − 19.9% (210,381). MoM utilization peaked in 2008 with 51,033 cases representing 40.1% of THAs implanted that year. The usage steadily declined and by 2014 there were only 6,600 MoM cases representing only 4.0% of the THAs. From 2007 to 2014, the use of CoP bearing surfaces increased from 11,482 discharges (11.1% of cases) in 2007, to 83,300 discharges (50.8% of cases) in 2014. CoP utilization surpassed MoP in 2014. MoP accounted for 54.7% of discharges in 2011 and just 42.1% in 2014. During the study period, MoM bearing surface usage declined precipitously, while CoP surpassed MoP as the most prevalent bearing surface used in total hip arthroplasty patients. These changes in bearing surface usage over time were clearly influenced by concerns regarding high failure rates associated with MoM articulations and reports of taper corrosion associated with modular metal femoral heads

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

Introduction. The prevalence of adverse reactions to metal debris around metal-on-metal (MOM) hip replacements has been reported to range from 7 to 69%. Little has been published on MRI scans with conventional total hip bearing surfaces. This study aimed to establish the prevalence of soft tissue lesions associated with metal-on-polyethylene (MOP) and ceramic-on-ceramic (COC) bearings, compared to MOM prostheses. Patients/Materials & Methods. All Metal Artefact Reduction Sequence (MARS) MRI scans for MOM THRs performed at our unit from January 2009 to present were reviewed, identifying those with contralateral primary MOP or COC THRs included on the scan. These were compared to a previously analysed cohort of 281 MOM THRs. Scans were classified using the Modified Oxford Classification as ‘Normal’, ‘Trochanteric Fluid’, ‘Effusions’ or Adverse Reactions to Debris. Results. 72 MOP and 17 COC prostheses were identified. More abnormalities were seen with scans performed within 12 months of surgery; 7 of 11 having findings consistent with post-operative seromas. These 11 were therefore excluded from further analysis. A higher proportion of normal MRIs were seen in the conventional prostheses group (78% v 34%, p<0.001). Adverse reactions to debris were significantly more common in MOM prostheses (39% v 4%, p<0.001). Effusions were more common with MOM bearings (13% v 4%, p=0.028). There was no difference in the rates of trochanteric fluid (both groups 14%). Discussion. A much higher rate of clinically significant fluid collections were seen with MOM prostheses as a result of increased toxicity of metal debris versus polyethylene or ceramic. There was little difference between MOP and COC scans. Trochanteric fluid collections are more likely to represent bursitis than any problem with the bearing surface. Conclusion. These results provide a useful baseline for comparison of MOM MARS MRI scans, adding to our understanding of the unique failure patterns of MOM prostheses

Aims. We present a case series of ten metal-on-polyethylene total hip arthroplasties (MoP THAs) with delayed dislocation associated with unrecognised adverse local tissue reaction due to corrosion at the trunnion and pseudotumour formation. . Methods. The diagnosis was not suspected in nine of the ten patients (six female/four male; mean age 66 years), despite treatment in a specialist unit (mean time from index surgery to revision was 58 months, 36 to 84). It was identified at revision surgery and subsequently confirmed by histological examination of resected tissue. Pre-operative assessment and culture results ruled out infection. A variety of treatment strategies were used, including resection of the pseudotumour and efforts to avoid recurrent dislocation. . Results. The rate of complications was high and included three deep infections, two patients with recurrent dislocation, and one recurrent pseudotumour. . Conclusion. This series (mean follow-up of 76 months following index procedure and 19 months following revision THA) demonstrates that pseudotumour is an infrequent but important contributor to delayed instability following MoP THA. It is easy to overlook in the differential diagnosis, especially if the alignment of the components is less than optimal, leading to an assumption that malalignment is the cause of the dislocation. The instability is likely to be multifactorial and the revision surgery is complex. Take home message: Due to the high complication rate associated with revision in this cohort, the diagnosis should be borne in mind when counselling patients regarding the risks of revision surgery. . Cite this article: Bone Joint J 2016;98-B:187–93

Adverse reaction to wear and corrosion debris is a cause for concern in total hip arthroplasty (THA). Modular junctions are a potential source of such wear products and are associated with secondary pseudotumour formation. . We present a consecutive series of 17 patients treated at our unit for this complication following metal-on-highly cross-linked polyethylene (MoP) THA. We emphasise the risk of misdiagnosis as infection, and present the aggregate laboratory results and pathological findings in this series. The clinical presentation was pain, swelling or instability. Solid, cystic and mixed soft-tissue lesions were noted on imaging and confirmed intra-operatively. Corrosion at the head–neck junction was noted in all cases. No bacteria were isolated on multiple pre- and intra-operative samples yet the mean erythrocyte sedimentation rate was 49 (9 to 100) and C-reactive protein 32 (0.6 to 106) and stromal polymorphonuclear cell counts were noted in nine cases. . Adverse soft–tissue reactions can occur in MoP THA owing to corrosion products released from the head–neck junction. The diagnosis should be carefully considered when investigating pain after THA. This may avoid the misdiagnosis of periprosthetic infection with an unidentified organism and mitigate the unnecessary management of these cases with complete single- or two-stage exchange. Cite this article: Bone Joint J 2015;97-B:1024–1030

The long term biological effects of wear products following total hip arthroplasty (THA) are unclear. However, the indications for THA are expanding, with increasingly younger patients undergoing the procedure. This prospective, randomised study compared two groups of patients undergoing THA after being randomised to receive one of two different bearing surfaces: metal-on-polyethylene (MoP) n = 22 and metal-on-metal (MoM) n = 23. We investigated the relationship between three variables: bearing surface (MoP vs MoM), whole blood levels of chromium (Cr) and cobalt (Co) and chromosomal aberrations in peripheral lymphocyte pre-operatively and at one, two and five years post-surgery. Our results demonstrated significantly higher mean cobalt and chromium (Co and Cr) blood levels in the MoM group at all follow-up points following surgery (p < 0.01), but there were no significant differences in the chromosomal aberration indices between MoM and MoP at two or five years (two years: p = 0.56, p = 0.08, p = 0.91, p = 0.51 and five years: p = 0.086, p = 0.73, p = 0.06, p = 0.34) for translocations, breaks, loss and gain of chromosomes respectively. Regression analysis showed a strong linear relationship between Cr levels and the total chromosomal aberration indices in the MoM group (R. 2.  = 0.90016), but this was not as strong for Co (R. 2. = 0.68991). In the MoP group, the analysis revealed a poor relationship between Cr levels and the total chromosomal aberration indices (R. 2. = 0.23908) but a slightly stronger relationship for Co (R. 2. = 0.64292). Across both groups, Spearman’s correlation detected no overall association between Co and Cr levels and each of the studied chromosomal aberrations. There remains no clear indication which THA bearing couple is the most biocompatible, especially in young active patients. While THA continues to be very successful at alleviating pain and restoring function, the long-term biological implications of the procedure still require further scrutiny. Cite this article: Bone Joint J 2015;97-B:1183–91