Aims. In metal-on-polyethylene (MoP) total hip arthroplasty (THA), large metal femoral heads have been used to increase stability and reduce the risk of dislocation. The increased size of the femoral head can, however, lead to increased taper corrosion, with the release of metal ions and adverse reactions. The aim of this study was to investigate the relationship between the size of the femoral head and the levels of metal ions in the blood in these patients. Methods. A total of 96 patients were enrolled at two centres and randomized to undergo MoP THA using either a 32 mm metal head or a femoral head of between 36 mm and 44 mm in size, being the largest possible to fit the thinnest available polyethylene insert. The levels of metal ions and patient-reported outcome measures (Oxford Hip Score, University of California, Los Angeles Activity Scale) were recorded at two and five years postoperatively. Results. At five years, the median levels of chromium, cobalt, and titanium were 0.5 μg/l (interquartile range (IQR) 0.50 to 0.62), 0.24 μg/l (IQR 0.18 to 0.30), and 1.16 μg/l (IQR 1.0 to 1.68) for the 32 mm group, and 0.5 μg/l (IQR 0.5 to 0.54), 0.23 μg/l (IQR 0.17 to 0.39), and 1.30 μg/l (IQR 1 to 2.05) for the 36 mm to 44 mm group, with no significant difference between the groups (p = 0.825, p = 1.000, p = 0.558). There were increased levels of metal ions at two years postoperatively in seven patients in the 32 mm group, compared with four in the 36 mm to 44 mm group, and at five years postoperatively in six patients in the 32 mm group, compared with seven in the 36 mm to 44 mm group. There was no significant difference in either the OHS (p = 0.665) or UCLA (p = 0.831) scores between patients with or without an increased level of metal ions. Conclusion. In patients who underwent MoP THA, we found no differences in the levels of metal ions five years postoperatively between those with a femoral head of 32 mm and those with a femoral head of between 36 mm and 44 mm, and no corrosion-related revisions. As taper corrosion can start after five years, there remains a need for longer-term studies investigating the relationship between the size of the femoral head size and corrosion in patients undergoing MoP THA. Cite this article: Bone Joint J 2024;106-B(3 Supple A):31–37

Objectives. Mechanical wear and corrosion at the head-stem junction of total hip arthroplasties (THAs) (trunnionosis) have been implicated in their early revision, most commonly in metal-on-metal (MOM) hips. We can isolate the role of the head-stem junction as the predominant source of metal release by investigating non-MOM hips; this can help to identify clinically significant volumes of material loss and corrosion from these surfaces. Methods. In this study we examined a series of 94 retrieved metal-on-polyethylene (MOP) hips for evidence of corrosion and material loss at the taper junction using a well published visual grading method and an established roundness-measuring machine protocol. Hips were retrieved from 74 male and 20 female patients with a median age of 57 years (30 to 76) and a median time to revision of 215 months (2 to 324). The reasons for revision were loosening of both the acetabular component and the stem (n = 29), loosening of the acetabular component (n = 58) and infection (n = 7). No adverse tissue reactions were reported by the revision surgeons. Results. Evidence of corrosion was observed in 55% of hips. The median Goldberg taper corrosion score was 2 (1 to 4) and the annual rate of material loss at the taper was 0.084 mm. 3. /year (0 to 0.239). The median trunnion corrosion score was 1 (1 to 3). Conclusions. We have reported a level of trunnionosis for MOP hips with large-diameter heads that were revised for reasons other than trunnionosis, and therefore may be clinically insignificant. Cite this article: H. S. Hothi, D. Kendoff, C. Lausmann, J. Henckel, T. Gehrke, J. Skinner, A. Hart. Clinically insignificant trunnionosis in large-diameter metal-on-polyethylene total hip arthroplasty. Bone Joint Res 2017;6:52–56. DOI: 10.1302/2046-3758.61.BJR-2016-0150.R2

Objectives. Hips with metal-on-metal total hip arthroplasty (MoM THA) have a high rate of adverse local tissue reactions (ALTR), often associated with hypersensitivity reactions. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) measures tissue perfusion with the parameter Ktrans (volume transfer constant of contrast agent). Our purpose was 1) to evaluate the feasibility of DCE-MRI in patients with THA and 2) to compare DCE-MRI in patients with MoM bearings with metal-on-polyethylene (MoP) bearings, hypothesising that the perfusion index Ktrans in hips with MoM THA is higher than in hips with MoP THA. Methods. In this pilot study, 16 patients with primary THA were recruited (eight MoM, eight MoP). DCE-MRI of the hip was performed at 1.5 Tesla (T). For each patient, Ktrans was computed voxel-by-voxel in all tissue lateral to the bladder. The mean Ktrans for all voxels was then calculated. These values were compared with respect to implant type and gender, and further correlated with clinical parameters. Results. There was no significant difference between the two bearing types with both genders combined. However, dividing patients by THA bearing and gender, women with MoM bearings had the highest Ktrans values, exceeding those of women with MoP bearings (0.067 min. −1. versus 0.053 min. −1. ; p-value < 0.05) and men with MoM bearings (0.067 min. −1. versus 0.034 min. −1. ; p-value < 0.001). Considering only the men, patients with MoM bearings had lower Ktrans than those with MoP bearings (0.034 min. −1. versus 0.046 min. −1. ; p < 0.05). Conclusion. DCE-MRI is feasible to perform in tissues surrounding THA. Females with MoM THA show high Ktrans values in DCE-MRI, suggesting altered tissue perfusion kinematics which may reflect relatively greater inflammation. Cite this article: Dr P. E. Beaule. Perfusion MRI in hips with metal-on-metal and metal-on-polyethylene total hip arthroplasty: A pilot stud. Bone Joint Res 2016;5:73–79. DOI: 10.1302/2046-3758.53.2000572

Recently, corrosion at the head-neck junction in metal-on-polyethylene bearing total hip arthroplasty (THA) has been recognized as a cause of adverse local tissue reactions (ALTR). Serum metal levels have been advocated as a tool for the diagnosis of ALTR, however no prior studies have specifically examined their utility. The purpose of this study was to determine the optimal cut-off values for serum cobalt and chromium in diagnosing ALTR after metal-on-polyethylene bearing THA. We reviewed 447 consecutive patients with serum metal levels tested at our institution and identified 62 with a metal-on-polyethylene bearing who had axial imaging or underwent reoperation to confirm the presence or absence of ALTR. Receiver operating characteristic curves were produced to identify cut-off thresholds to optimize sensitivity and diagnostic test performance was characterized. 42 Of the 62 patients (66%) were positive for an ALTR. The best test for the diagnosis of ALTR was the serum cobalt level (area under the curve [AUC]=99%). A threshold cut-off of ≥ 1.0 ng/ml had a sensitivity of 100%, specificity of 90%, positive predictive value (PPV) of 96%, and negative predictive value (NPV) of 100%. Serum chromium levels were also diagnostic (AUC=87%). A threshold cut-off of ≥ 0.15 ng/ml had a sensitivity of 100%, specificity of 50%, PPV of 81%, and NPV of 100%. Finally, serum cobalt to chromium ratio was also helpful for diagnosis (AUC=90%). A threshold cut-off of 1.4 for the cobalt to chromium ratio offered a sensitivity of 93%, specificity of 70%, PPV of 87%, and NPV of 82%. Measurement of serum cobalt with a threshold value of 1.0 ng/ml in our experience is the best test for identifying the presence of ALTR in patients with a metal-on-polyethylene THA. Measurement of chromium and the ratio of cobalt to chromium are also of value

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

Introduction. Mechanically assisted crevice corrosion (MACC) in metal-on-polyethylene (MOP) total hip arthroplasty (THA) is of concern, but its prevalence, etiology and natural history are incompletely understood. Methods. From January 2003 to December 2012, 1356 consecutive THA surgeries using a titanium stem, cobalt chromium alloy femoral head, highly crosslinked polyethylene and a tantalum or titanium acetabular shell were performed. Patients were followed at 1 year, and 5 year intervals for surveillance, but also seen earlier if they had symptoms. Any patient with osteolysis or unexplained pain underwent exam, radiographs, CBC, ESR and CRP, as well as serum cobalt (Co) and chromium (Cr) level. MARS MRI was performed if the Co level was > 1 ppb. Results. Symptomatic MACC was present in 39/1356 patients (2.9%). Yearly MACC prevalence ranged from 0 % (0/139, 2005) to 9.9 % (16/162, 2009). 22/39 (56%) patients have undergone revision surgery, and 17/39 (44%) have opted for ongoing surveillance. Of the surveillance patients, serial serum metal ion levels appear to increase over time. Time of symptoms is correlated with tissue necrosis at time of revision. Conclusions. The prevalence of MACC in MOP hips is higher in this cross-sectional study than previously reported. The highest prevalence was found in 2009 with this vendor. Based on how common this finding is in symptomatic patients from 2009, we may consider asking asymptomatic patients to obtain baseline serum ion levels. The goal of our ongoing research is to understand how to avoid permanent soft tissue loss from adverse local tissue reactions caused by MACC

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.

INTRODUCTION

Component positioning of an artificial hip joint plays a key role in durability of implant. Despite the fact that a number of numerical, experimental and clinical studies have been carried out to investigate the effects of cup inclination on polyethylene wear, steep inclination has been reported to be associated with both high and low volumetric wear. Moreover, how cup anteversion affects wear and its interaction with inclination are still unclear. To address these knowledge gaps, in this study wear and contact mechanics of a hip joint under various cup positioning has been investigated by using FEA (Finite Element Analysis).

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.

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.

We present here a case of pseudotumor formation likely due to metal wear debris generated at the head-neck taper (trunnion) of the femoral stem and head components in a metal-on-highly cross-linked polyethylene (MOP) total hip arthroplasty. Over the last few years, this recently described diagnosis, trunnionosis, is being recognized and reported more frequently. This patient presented with a rather large (12 cm diameter) pseudotumor with accompanying loss of abductors and a pelvic discontinuity making reconstruction more challenging. We believe the psuedotumor in this patient developed from trunnionosis. This is an interesting case of aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) in a MOP total hip arthroplasty.

Aims

We have previously demonstrated raised cobalt and chromium levels in patients with larger diameter femoral heads, following metal-on-polyethylene uncemented total hip arthroplasty. Further data have been collected, to see whether these associations have altered with time and to determine the long-term implications for these patients and our practice.

Introduction

Taper corrosion at modular junctions can cause a spectrum of adverse local tissue reactions (ALTR) in the periprosthetic soft tissues in patients who have undergone total hip arthroplasty (THA). Because these reactions are usually painful, taper corrosion has become part of the differential diagnosis of hip pain following THA. However these destructive lesions may not always cause pain, and can occasionally result in other atypical presentations. The purpose of this study is to describe a cohort of patients presenting with late and recurrent instability following THA due to underlying ALTR and taper corrosion.

The aim of this study is to investigate whether MoM implants result in more chromosome aberrations and increased blood metal ions postoperatively whe compared to MoP implants.

MoM arthroplasties are being inserted in increasing numbers of younger patients due to the increased durability and reduced requirements for revision in these implants. Recent studies have raised many concerns over possible genotoxicity of MoM implants.

This is a prospective study of patients who have undergone elective total hip replacement, they were selected and then randomised into two groups. Group A received a MoP implant and group B received a MoM implant. Patients are reviewed pre-operatively (control group), at 3 months, 6 months, 1 year and 2 years post-operatively. On each occasion blood tests are taken to quantify metal ion levels (chromium, cobalt, titanium, nickel and vanadium) using HR-ICPMS method and chromosome aberrations in T lymphocytes using 24 colour fluorescent in situ hydridisation (FISH).

51 patients have been recruited to date, 23 of whom had MoP prosthesis and 28 a MoM. 47 of these had their 1 year follow-up with blood analysis and 38 have had 2 year follow up. There appeared to be a bedding period for both MoM and MoP groups, with an increase in metal ion release. The blood concentration of chromium, cobalt and titanium rise significantly in the MoM group at the 2 year stage. Chromosome aberrations occurred in both groups. Both the MoM and MoP groups showed increase frequency of aneuploidy aberrations and structural damage. The greatest increase in metal ion levels occurred at the 1 to 2 year interval corresponding to significant rise in chromosome aberrations.

Preliminary results of this study show that the levels of chromium, cobalt and titanium are significantly higher in the MoM group compared to the MoP group. This corresponds to increases in chromosome aberrations in the groups with increases in structural chromosome damage after two years.

Local and systemic concentrations of cobalt (Co) and chromium (Cr) ions may be elevated in patients with accelerated tribo-corrosion at prosthesis bearing surfaces and modular taper junctions. Previous studies by us and others have shown that exposure to these metals negatively affect the viability and function of osteoblasts and osteoclasts in vitro, with implications for bone health. More recently, we have observed an increase in total bone mineral density and reduced bone turnover (TRAP5b and osteocalcin) in patients with well-functioning metal-on-metal hip resurfacing (MOMHR). Here, we provide data to support the hypothesis that osteoclast differentiation and function is altered in this patient population, and that this effect is transferrable through their serum. Patients with well-functioning MOMHR (n=18) at median follow-up of 8 years were individually matched for gender, age and time-since-surgery to a low-exposure group consisting of patients with metal-on-polyethylene total hip arthroplasty (THA). The median circulating concentrations of Co and Cr for the MOMHR group were 2.53µg/L and 2.5µg/L respectively, compared to 0.02µg/L and 0.03µg/L for the THA group. Monocyte fraction of peripheral blood was isolated from these patients, seeded onto dentine wafers and differentiated into osteoclasts using media supplemented with RANKL and M-CSF (osteoclastogenic media, OM). Cultures were monitored for the onset of resorption, following which they were treated with OM, autologous serum or serum from the other individual within the matched MOMHR - THA pair, all supplemented with RANKL and M-CSF. At the end of the culture, cells were TRAP stained and quantified for total osteoclast number, number of resorbing osteoclasts and percentage resorption using the CellD Software Package (Olympus, Southend-on-Sea, U.K.). For cells differentiated in osteoclastogenic media, the resorbing ability of osteoclasts derived from MOMHR patients was reduced by 30% (P=0.046) compared to THA. Correlation analyses showed that chronic exposure to Co and Cr trends towards negative association with resorption ability of these osteoclasts (r = −0.3, P=0.06). Furthermore, the resorbing ability of osteoclasts generated from MOMHR patients and differentiated in autologous serum was reduced 33% (p < 0 .0001), whilst matched THA serum caused a smaller reduction of 14% (p < 0 .01). When cells derived from THA patients were differentiated in autologous serum, the resorbing ability of osteoclasts was similarly reduced by 35% (p < 0 .0001), whilst the matched MOMHR serum also caused a reduction of 21% (p < 0 .0001). Reduced osteoclastogenic response of precursor cells from patients with higher circulating Co and Cr suggests an inherent change in their potential to differentiate into functional osteoclasts. The data also suggests that functional response of mature osteoclasts generated from patient precursor cells are dependent on the prior systemic metal concentrations and the presence of higher circulating CoCr in patients with MOMHR. These effects are modest, but may explain the subtle increase in systemic bone mineral density and decreased bone turnover observed in patients after 8 years exposure compared to age, sex, and exposure-time matched patients who received a conventional THA

Uncemented metal-on-polyethylene total hip arthroplasties (THAs) have had a modular cobalt-chrome alloy head since their introduction in the early 1980's. Retrieval analysis studies and case reports in the early 1990's first reported corrosion between the femoral stem trunnion (usually titanium alloy) and cobalt-chrome alloy femoral head. However, then this condition seemed to disappear for about two decades? There are now numerous recent case series of this problem after metal-on-polyethylene THA, with a single taper or dual taper modular femoral component. Metal ion elevation, corrosion debris, and effusion are caused by mechanically assisted crevice corrosion (MACC). These patients present with diffuse hip pain, simulating trochanteric bursitis, iliopsoas tendinitis, or even deep infection. Trunnion corrosion, with adverse local tissue reaction, is a diagnosis of exclusion, after infection, loosening, or fracture. The initial lab tests recommended are: ESR, CRP, and serum cobalt and chromium ions. With a metal-on-polyethylene THA, a cobalt level > 1ppb is abnormal. Plain radiographs are usually negative, but may show calcar osteolysis or acetabular erosion or cyst. MARS MRI may be the best imaging study to confirm the diagnosis. Hip aspiration for culture and cell-count may be necessary. The operative treatment is empiric, with debridement, and head exchange with a ceramic head-titanium sleeve (or oxidised zirconium head) placed on the cleaned trunnion. The femoral component may have to be removed if there is “whole trunnion failure”. This usually relieves the symptoms, but the complication rate of this procedure may be high

Tribocorrosion at the head–neck taper interface – so-called ‘taperosis’ – may be a source of metal ions and particulate debris in metal-on-polyethylene total hip arthroplasty (THA). We examined the effect of femoral head length on fretting and corrosion in retrieved head–neck tapers in vivo for a minimum of two years (mean 8.7 years; 2.6 to 15.9). A total of 56 femoral heads ranging from 28 mm to 3 mm to 28 mm + 8 mm, and 17 femoral stems featuring a single taper design were included in the study. Fretting and corrosion were scored in three horizontally oriented concentric zones of each taper by stereomicroscopy. Head length was observed to affect fretting (p = 0.03), with 28 mm + 8 mm femoral heads showing greater total fretting scores than all other head lengths. The central zone of the femoral head bore taper was subject to increased fretting damage (p = 0.01), regardless of head length or stem offset. High-offset femoral stems were associated with greater total fretting of the bore taper (p = 0.04). Increased fretting damage is seen with longer head lengths and high-offset femoral stems, and occurs within a central concentric zone of the femoral head bore taper. Further investigation is required to determine the effect of increased head size, and variations in head–neck taper design. Cite this article: Bone Joint J 2015; 97-B:911–16

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

Ceramic-on-ceramic bearings provide a solution to the osteolysis seen with traditional metal-on-polyethylene bearings. Sporadic reports of ceramic breakage and squeaking concern some surgeons and this bearing combination can show in vivo signs of edge loading wear which was not predicted from in vitro studies. Taper damage or debris in the taper between the ceramic and metal may lead to breakage of either a ceramic head or insert. Fastidious surgical technique may help to minimise the risk of ceramic breakage. Squeaking is usually a benign complication, most frequently occurring when the hip is fully flexed. Rarely, it can occur with each step of walking when it can be sufficiently troublesome to require revision surgery. The etiology of squeaking is multifactorial origin. Taller, heavier and younger patients with higher activity levels are more prone to hips that squeak. Cup version and inclination are also relevant factors. Fifty-five ceramic bearings revised at our center were collected over 12 years. Median time to revision was 2.7 years. Forty-six (84%) cases had edge loading wear. The median femoral head wear volume overall was 0.2mm. 3. /yr, for anterosuperior edge loading was 2.0mm. 3. /yr, and the median volumetric wear rate for posterior edge loading was 0.15mm. 3. /yr (p=0.005). Osteolysis following metal-on-polyethylene total hip arthroplasty (THA) is well reported. Earlier generation ceramic-on-ceramic bearings did produce some osteolysis, but in flawed implants. As 3rd and now 4th generation ceramic THAs come into mid- and long-term service, the orthopaedic community has begun to see reports of high survival rates and very low incidence of osteolysis in these bearings. The technique used by radiologists for identifying the nature of lesions on Computed Tomography (CT) scan is the Hounsfield score which will identify the density of the tissue within the lucent area. Commonly the radiologist will have no access to previous imaging, especially pre-operative imaging if a long time has elapsed. With such a low incidence of osteolysis in this patient group, what, then, should a surgeon do on receiving a CT report on a ceramic-on-ceramic THA, which states there is osteolysis? This retrospective review aims to determine the accuracy of CT in identifying true osteolysis in a cohort of long-term 3rd generation ceramic-on-ceramic uncemented hip arthroplasties in our department. Methods. Pelvic CT scans were performed on the first 27 patients from a cohort of 301 patients undergoing 15-year review with 3rd generation alumina-alumina cementless THAs. The average follow-up was 15 years (15–17). The CT scans were reviewed against pre-operative and post-operative radiographs and reviewed by a second musculoskeletal specialist radiologist. Results. Eleven of the CT scans were reported to show acetabular osteolysis, two reported osteolysis or possible pre-existing cyst and one reported a definitive pre-existing cyst. After review of previous imaging including pre-operative radiographs, eleven of the thirteen patients initially reported to have osteolysis were found to have pre-existing cysts or geodes in the same size and position as the reported osteolysis, and a further patient had spot-welds with stress-shielding. One patient with evidence of true osteolysis awaits aspiration or biopsy to determine if he has evidence of ceramic wear or metallosis. Conclusions. Reports of osteolysis on CT should be interpreted with care in modern ceramic-on-ceramic THA to prevent unnecessary revision. Further imaging and investigations may be necessary to exclude other conditions such as geodes, or stress shielding which are frequently confused with osteolysis on CT scans

Background and aim. Arthroplasty registries and consecutive series indicate significantly worse results of conventional metal-on-polyethylene total hip arthroplasty (THA) in patients younger than 50 years compared to older patients, with inferior clinical outcomes and 10-year survivorship ranging between 70 and 90%. At our institution, patients under 50 needing a THA receive either a metal-on-metal hip resurfacing (MoMHRA) or a ceramic-on-ceramic (CoC)THA. In order to evaluate the outcome of these options at minimum 10 years, we conducted a retrospective review of all MoMHRA and CoCTHA with more than 10 years follow-up implanted in patients under 50. Methods. From a single surgeon patients’ prospective database, we identified all consecutive THA performed before May 2005 in patients under 50. All patients are contacted by phone and asked to present for a clinical exam and patient reported outcome questionnaires, standard radiographs and metal ion measurements unless the hip arthroplasty has been revised. Complications and reasons for revision are noted. Kaplan-Meier survivorship is analysed for the whole cohort and sub-analysis is performed by type hip arthroplasty, gender, diagnosis and component size. Results. We identified 773 hip arthroplasties in 684 patients under 50 years performed by a single surgeon between 1997 and May 2005. There are 626 MoMHRA, all Birmingham Hip Resurfacings (BHR) in 561 patients (65 bilateral BHR), 135 CoCTHA in 111 patients (24 bilateral CoC) and 12 Metasul MoMTHA in 12 patients. In the BHR group, there are 392 males (70%) (42 bilateral) and 169 females (30%) (23 bilateral). Mean age at surgery was 40.8 years (median 42 years; range 16–50 years). In 33 cases, a BHR dysplasia cup was used (23 in females). Mean follow-up is 11.5 years (median 11 years; range 10–17 years). In the Metasul MoMTHA, there are 8 males and 4 females. Mean age at surgery was 40.4 years (range 20–50 years). All THA were non-cemented and head size was 28mm in all cases. Mean follow-up is 16.8 years (median 17.5 years; range 12–19 years). In the CoCTHA group, there are 71 males (64%) (17 bilateral) and 40 females (36%) (7 bilateral). Mean age at surgery was 38.2 years (median 39 years; range 16–50 years). In 21 cases, the CoCTHA was a revision of a former hip replacement: 15 THA revisions and 6 hip resurfacing revisions. Three types non-cemented acetabular components were used and 7 types femoral stems (5 non-cemented; 2 cemented). Ceramic heads and inlays were Biolox forte in 128 cases and Biolox delta in 7. Head size was 28mm in 125, 32mm in 7 and 36mm in 3. Mean follow-up is 14.9 years (median 15 years; range 10–18 years). Discussion. Patients under 50 needing a hip arthroplasty often present with more complex anatomic abnormalities or bone damage as in congenital dysplasia, avascular necrosis, traumatic osteoarthritis or rheumatic diseases. Besides, the worse results with conventional THA in young patients may be related to a higher activity level. We present the outcome and survivorship of MoMHRA and CoCTHA in patients under 50 at more than 10 years postop