Aims. The aims of this study were to determine if an increasing serum cobalt (Co) and/or chromium (Cr) concentration is correlated with a decreasing Harris Hip Score (HHS) and Hip disability and Osteoarthritis Outcome Score (HOOS) in patients who received the Articular Surface Replacement (ASR) hip resurfacing arthroplasty (HRA), and to evaluate the ten-year revision rate and show if sex, inclination angle, and Co level influenced the revision rate. Methods. A total of 62 patients with an ASR-HRA were included and monitored yearly postoperatively. At follow-up, serum Co and Cr levels were measured and the HHS and the HOOS were scored. In addition, preoperative patient and implant variables and the need for revision surgery were recorded. We used a linear mixed model to relate the serum Co and Cr levels to different patient-reported outcome measures (PROMs). For the survival analyses we used the Kaplan-Meier and Cox regression model. Results. We found that an increase of one part per billion (ppb) in serum Co and Cr levels correlated significantly with worsening of the HHS in the following year. This significant correlation was also true for the HOOS-Pain and HOOS-quality of life sub scores. The overall ten-year survival rate in our cohort was 65% (95% confidence interval (CI) 52.5 to 77.6). Cox regression analysis showed a significant hazard ratio (HR) of 1.08 (95% CI 1.01 to 1.15; p = 0.028) for serum Co level. No significance was found with sex or inclination angle. Conclusion. This study shows that increasing serum Co and Cr levels measured in patients with an ASR-HRA are predictive for deterioration in HHS and HOOS subscales in the following year. Increasing serum Co and Cr should forewarn both surgeon and patient that there is a heightened risk of failure. Continued and regular review of patients with an ASR-HRA implant by measurement of serum Co/Cr levels and PROMs remains essential. Cite this article: Bone Joint J 2023;105-B(7):775–782

Recently, some smart media devices including portable accelerometers have been used to measure objective physical activity (OPA) after total hip arthroplasty (THA). The aim of this study was to longitudinally assess OPA changes in patients who underwent THA using a compact triaxial accelerometer and to investigate the impact of this recovery process on patient-reported outcomes. This prospective cohort study involved 163 consecutive patients who had unilateral osteoarthritis of the hip and were followed up for 12 months after THA. There were 132 women and 31 men with average age of 66 years. OPA was measured using a compact triaxial accelerometer preoperatively and at 1, 3, 6, and 12 months postoperatively. This study investigated the recovery process of OPA in four patient groups classified by the median of age and preoperative activity levels (younger and higher activity (YH), younger and lower activity (YL), older and higher activity (OH), and older and lower activity (OL)), and examined its impact on patient-reported outcomes, including forgotten joint score-12 (FJS-12). The target period for regaining preoperative activity levels was approximately 3 months for patients with lower preoperative activity, and about 6 months for those with higher preoperative activity. The OPA at 12 months postoperatively was higher in the patients with higher preoperative activity levels than in those with lower preoperative activity levels. In patients with higher preoperative activity levels, FJS-12 scores significantly increased between 6 and 12 months postoperatively (p=0.018). FJS-12 at 12 months postoperatively was best in YH (81.7±18.9), followed by YL (73.5±22.9), OH (73.2±17.4), and OL (66.3±21.8). Differences in the recovery process of postoperative activity levels impacted the duration required for improvement in FJS-12 scores. These results can serve as indicators for setting activity goals in patients undergoing THA

Aims. Osteoporosis is common in total hip arthroplasty (THA) patients. It plays a substantial factor in the surgery’s outcome, and previous studies have revealed that pharmacological treatment for osteoporosis influences implant survival rate. The purpose of this study was to examine the prevalence of and treatment rates for osteoporosis prior to THA, and to explore differences in osteoporosis-related biomarkers between patients treated and untreated for osteoporosis. Methods. This single-centre retrospective study included 398 hip joints of patients who underwent THA. Using medical records, we examined preoperative bone mineral density measures of the hip and lumbar spine using dual energy X-ray absorptiometry (DXA) scans and the medications used to treat osteoporosis at the time of admission. We also assessed the following osteoporosis-related biomarkers: tartrate-resistant acid phosphatase 5b (TRACP-5b); total procollagen type 1 amino-terminal propeptide (total P1NP); intact parathyroid hormone; and homocysteine. Results. The prevalence of DXA-proven hip osteoporosis (T-score ≤ -2.5) among THA patients was 8.8% (35 of 398). The spinal osteoporosis prevalence rate was 4.5% (18 of 398), and 244 patients (61.3%; 244 of 398) had osteopenia (-2.5 < T-score ≤ -1) or osteoporosis of either the hip or spine. The rate of pharmacological osteoporosis treatment was 22.1% (88 of 398). TRACP-5b was significantly lower in the osteoporosis-treated group than in the untreated group (p < 0.001). Conclusion. Osteoporosis is common in patients undergoing THA, but the diagnosis and treatment for osteoporosis were insufficient. The lower TRACP-5b levels in the osteoporosis-treated group — that is, osteoclast suppression — may contribute to the reduction of the postoperative revision rate after THA. Cite this article: Bone Joint Res 2022;11(12):873–880

Background. The impact of a patient's activity level following total hip arthroplasty (THA) remains controversial, with some concerned about increased polyethylene wear, aseptic loosening and revisions. The purpose of this study is to report on implant survivorship and outcomes of high activity patients compared to low activity patients after THA with current polyethylene. Methods. A retrospective review identified 2002 patients (2532 hip) that underwent a primary THA with vitamin E infused highly crosslinked polyethylene liner and 2-year minimum follow-up or revision. Patients were divided in two groups based on their University of California Los Angeles (UCLA) activity level: Low activity (LA) (UCLA ≤5) and high activity (HA) (UCLA ≥ 6). Outcomes included Harris Hip Score, UCLA activity score, complications and reoperations. Multivariate nominal regression analysis was performed to evaluate the significance of postoperative activity level on survivorship while controlling for age, gender, preoperative pain, HHS and body mass index (BMI). Results. Mean follow-up was 4.5 years (range, 0.3 to 9.9 years). The LA group had significantly more female patients, were older, higher BMI and lower HHS pre-operatively (all with p<0.001). HA group had significantly higher improvements in HHS (p<0.001) and UCLA activity score (p<0.001). Aseptic revisions were performed in 2.1% of the LA group and in 0.4% hips of the HA group (p<0.001). Multivariate regression analysis found that a higher postoperative activity level remained a significant factor for improved aseptic survivorship with an OR of 4.9 (95% CI, 1.1 to 21.2, p=0.03). The aseptic 5-year survivorship was 99.6% for the HA group and 98% for the LA group (p<0.001). Conclusions. Higher activity level after primary THA did not increase the risk for midterm aseptic or all cause failure. Patient activity level after THA may not need to be limited with modern polyethylene

Total Hip Arthroplasty (THA) surgery is a physical and cognitive challenge for surgeons. Data on stress levels, cognitive and physical load of orthopaedic surgeons, as well as ergonomic impact, are limited. With and without the use of an automated impaction device, operational efficiency and the surgeon's ergonomic, mental, and physical load was investigated. In a total of thirty THA procedures, a standard manual technique was compared with an automated impaction device. Three computerized cognitive tasks (Simon, pattern comparison, and pursuit rotor) and five physical tests (isometric wall-sit, plank-to-fatigue, handgrip, supra-postural task, and shoulder endurance) were used to assess psychophysiological load of the surgeon. Surgeon's cortisol concentration was evaluated from saliva samples. Postural risk was assessed by Rapid Upper Limb Assessment (RULA) and Rapid Entire Body Assessment (REBA). Efficiency was assessed by timing surgical steps and instrumentation flow. Cognitive performances after automated impaction showed faster response times and lower error rates with a greater time-on-target (+1.5 s) and a lower mouse deviation from target (−1.7 pixels). Manual impaction showed higher physical exhaustion in the isometric wall-sit test (10.6% vs. 22.9%), plank-to-fatigue (2.2% vs. 43.8%), the number of taps in the supra-postural task (−0.7% vs. −7.7%), handgrip force production in the dominant (−6.7% vs. −12.7%) and contralateral hand (+4.7% vs. +7.7%), and in shoulder endurance (−15s vs. −56s). An increase of 38.2% in salivary cortisol concentration between the midday (1.31 nmol/l) and afternoon session (1.81 nmol/l) was observed with manual impaction. After using automated impaction, salivary cortisol concentration decreased (−51.2%). Manual broaching time was on average 6′20’’ versus 7’3’’ with automated impaction. RULA of manual impaction scored 6 for cup impaction and 5 for femoral broaching, versus 3 and 3 for automated impaction, respectively. REBA of manual impaction scored 9 for cup impaction and 5 for femoral broaching, versus 4 and 3 for automated impaction, respectively. Automated impaction lowers surgeons’ cognitive and physical fatigue and leads to reduced stress and improved ergonomics without loss of surgical efficiency

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. Methods. Patients from our previous study who underwent Trident-Accolade primary total hip arthroplasties using a metal-on-polyethylene bearing in 2009 were reviewed. Patients were invited to have their cobalt and chromium levels retested, and were provided an Oxford Hip Score. Serum ion levels were then compared between groups (28 mm, 36 mm, and 40 mm heads) and over time. Results. Metal ion levels were repeated in 33 patients. When comparing the results of serum metal ion levels over time, regardless of head size, there was a significant increase in both cobalt and chromium levels (p < 0.001). Two patients with larger head sizes had undergone revision arthroplasty with evidence of trunnion damage at surgery. Two patients within the 40 mm subgroup had metal ion levels above the MHRA (Medicines and Healthcare Products Regulatory Agency) threshold for detailed investigation. The increase in cobalt and chromium, when comparing the 36 mm and 40 mm groups with those of the 28 mm group, was not significant (36 mm vs 28 mm; p = 0.092/p = 0.191; 40 mm vs 28 mm; p = 0.200/p = 0.091, respectively). There was no difference, between femoral head sizes, when comparing outcome as measured by the Oxford Hip Score. Conclusion. This study shows an increase in cobalt and chromium levels over time for all modular femoral head sizes in patients with metal-on-polyethylene bearings, with two patients demonstrating ion levels above the MHRA threshold for failure, and a further two patients requiring revision surgery. These results may have clinical implications regarding longer term follow-up of patients and future implant choice, particularly among younger patients. Cite this article: Bone Joint J 2020;102-B(7):832–837

Aims. Modular dual-mobility constructs reduce the risk of dislocation after revision total hip arthroplasty (THA). However, questions about metal ions from the cobalt-chromium (CoCr) liner persist, and are particularly germane to patients being revised for adverse local tissue reactions (ALTR) to metal. We determined the early- to mid-term serum Co and Cr levels after modular dual-mobility components were used in revision and complex primary THAs, and specifically included patients revised for ALTR. Patients and Methods. Serum Co and Cr levels were measured prospectively in 24 patients with a modular dual-mobility construct and a ceramic femoral head. Patients with CoCr heads or contralateral THAs with CoCr heads were excluded. The mean age was 63 years (35 to 83), with 13 patients (54%) being female. The mean follow-up was four years (2 to 7). Indications for modular dual-mobility were prosthetic joint infection treated with two-stage exchange and subsequent reimplantation (n = 8), ALTR revision (n = 7), complex primary THA (n = 7), recurrent instability (n = 1), and periprosthetic femoral fracture (n = 1). The mean preoperative Co and Cr in patients revised for an ALTR were 29.7 μg/l (2 to 146) and 21.5 μg/l (1 to 113), respectively. Results. Mean Co and Cr levels were 0.30 μg/l and 0.76 μg/l, respectively, at the most recent follow-up. No patient had a Co level ≥ 1 μg/l. Only one patient had a Cr level ≥ 1 μg/l. That patient’s Cr level was 12 μg/l at 57 months after revision THA for ALTR (and decreased ten-fold from a preoperative Cr of 113 μg/l). Conclusion. At a mean of four years, no patient with a modular dual-mobility construct and ceramic femoral head had elevated Co levels, including seven patients revised specifically for ALTR. While further studies are required, we support the selective use of a modular dual-mobility construct in revision and complex primary THAs for patients at high risk for instability. Cite this article: Bone Joint J 2019;101-B(6 Supple B):57–61

Aims. The aim of this study was to evaluate blood metal ion levels, leucocyte profiles, and serum cytokines in patients with a total hip arthroplasty (THA) involving modular dual-mobility components. Patients and Methods. A total of 39 patients were recruited, with clinical follow-up of up to two years. Outcome was assessed using the Harris Hip Score (HHS, the 12-Item Short-Form Health Survey (SF-12), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and a visual analogue scale (VAS) for pain. Blood concentrations of cobalt (Co), chromium (Cr), and serum cytokines were measured. Subpopulations of leucocytes were analyzed by flow cytometry. Results. The clinical performance was good. Blood Co levels (ref 1.0 µg/l) were mildly elevated in seven patients at three months, and two patients at two years’ follow-up. The preoperative Cr levels were normal except for one patient with a detectable Cr (1.2 µg/l). Cr levels were detectable in three patients at three months, two patients at one year, and three patients at two years’ follow-up. No patients had symptoms suggestive of failure. Although flow cytometry showed constant circulating leucocyte profiles, there was a significant reduction of serum interleukin (IL)-4, IL-5, and interferon gamma (IFNγ) postoperatively compared with the preoperative levels (p < 0.05). Conclusion. These results suggest that THA using modular dual-mobility components is safe. This allows an opportunity to use a large femoral head and a thick polyethylene bearing surface, which is especially useful in revision procedures or high-risk situations when added stability is required. Cite this article: Bone Joint J 2019;101-B:1035–1041

Accurate placement of the acetabular component is essential in Total Hip Arthroplasty (THA). The purpose of this study is to determine if an analog spirit level can improve the surgeon's ability to achieve acetabular inclination within the “safe-zone” of 30 to 50 degrees. We reviewed 167 primary THAs performed by a single surgeon over 14 months. Procedures were performed at two facilities, an inpatient hospital where a spirit level was utilized and an ambulatory facility where it was not. We excluded 47 patients with a BMI>40, age>68 or a surgical indication other than osteoarthritis who were not candidates for the ambulatory center. Cup inclination angles were measured from de-identified plain radiographs by two blinded investigators not involved in the index procedures. The effect of level usage on inclination angle was determined using multivariate regression analysis. The mean inclination angle for the 68 hips performed with the level was 42.9 degrees (95% CI: 41.7–44.0) compared to 46.5 degrees (95% CI: 45.2–47.7) for the 52 hips without it (p<.001). Regression analysis demonstrated a 9.1% difference in cup inclination due to the level (p<.001), and THAs performed without the level were 3 times more likely to result in inclinations > 50 degrees (OR 2.8, p=.036). The two investigators' measurements demonstrated a correlation of 0.95 (95% CI: 0.93–0.97). Use of a simple spirit level resulted in a significant reduction in the number of outliers compared to the freehand technique. The spirit level may be a simple and inexpensive tool to improve acetabular component abduction angles

Aims. The purpose of this study was to compare two different types of metal-on-metal (MoM) bearing for total hip arthroplasty (THA): one with a large femoral head (38 mm to 52 mm) and the other with a conventional femoral head (28 mm or 32 mm). We compared clinical outcome, blood metal ion levels, and the incidence of pseudotumour in the two groups. Patients and Methods. Between December 2009 and December 2011, 62 patients underwent MoM THA with a large femoral head (Magnum group) and 57 patients an MoM THA with a conventional femoral head (conventional group). Clinical outcome was assessed using the Harris Hip score, University of California, Los Angeles (UCLA) activity score and EuroQol-5D (EQ-5D). Blood metal ion levels were measured and MRI scans were analyzed at a minimum of five years postoperatively. Results. No acetabular component was implanted with more than 50° of inclination in either group. The Harris Hip Score, UCLA activity score, and EQ-5D improved postoperatively in both groups; no significant clinical differences were noted between the groups. The blood cobalt ion levels in the conventional group continued to rise postoperatively to five years while reaching a plateau at two years postoperatively in the Magnum group. At five years, the mean cobalt ion level of 1.16 μg/l (. sd. 1.32) in the Magnum group was significantly lower than the 3.77 μg/l (. sd. 9.80) seen in the conventional group (p = 0.0015). The incidence of moderate to severe pseudotumour was 4.7% in the Magnum group and 20.6% in the conventional group. There were no dislocations in the Magnum group and two in the conventional group. One patient in the Magnum group underwent revision for pseudotumour at 4.7 years postoperatively. Conclusion. At five years, a well-positioned large head MoM THA has a significantly lower level of metal ion release and a lower incidence of moderate to severe pseudotumour than a MoM bearing of conventional size. Cite this article: Bone Joint J 2018;100-B:1018–24

This study investigates the use of the Metabolic Equivalent of Task (MET) score in a hip arthroplasty population and its ability to capture additional benefit beyond the maximum Oxford Hip Score (OHS). OHS, EuroQol-5D index (EQ-5D), and the MET were prospectively recorded in 221 primary hip arthroplasty procedures pre-operatively and at 1-year. The distribution was examined reporting the presence of ceiling & floor effects. Validity was assessed correlating the MET with the other scores using Spearman's rank and determining responsiveness using the standardised response mean (SRM). A subgroup of 93 patients scoring 48/48 on the OHS were analysed by age group, sex, BMI and pre-operative MET using the other two metrics to determine if differences could be established despite all scoring identically on the OHS. 117 total hip and 104 hip resurfacing arthroplasty operations were included. Mean age was 59.4 ± 11.3. Post-operatively the OHS and EQ-5D demonstrate significant negatively skewed distributions with ceiling effects of 41% and 53%, respectively. The MET was normally distributed post-operatively with no ceiling effect. Weak-moderate but statistically significant correlations were found between the MET and the other two metrics both pre & post-operatively. Responsiveness was excellent, SRM for OHS: 2.01, EQ-5D: 1.06 and MET: 1.17. In the 48/48 scoring subgroup, no differences were found comparing groups with the EQ-5D, however significantly higher MET scores were demonstrated for patients aged <60 (12.7 vs 10.6, p=0.008), male patients (12.5 vs 10.8, p=0.024) and those with pre-operative MET scores >6 (12.6 vs 11.0, p=0.040). The MET is normally distributed in patients following hip arthroplasty, recording levels of activity which are undetectable using the OHS. As a simple, valid activity metric, it should be considered in addition to conventional PROMs in order to capture the entire benefit experienced following hip arthroplasty

Aims. Despite declining frequency of blood transfusion and electrolyte supplementation following total joint arthroplasty, postoperative blood analyses are still routinely ordered for these patients. This study aimed to determine the rate of blood transfusion and electrolyte restoration in arthroplasty patients treated with a perioperative blood conservation protocol and to identify risk factors that would predict the need for transfusion and electrolyte supplementation. Patients and Methods. Patients undergoing primary total joint arthroplasty of the hip or knee between July 2016 and February 2017 at a single institution were included in the study. Standard preoperative and postoperative laboratory data were collected and reviewed retrospectively. A uniform blood conservation programme was implemented for all patients. Need for blood transfusion or potassium supplementation was determined through a coordinated decision by the care team. Rates of transfusion and supplementation were observed, and patient risk factors were noted. Results. The overall rate of blood transfusion was 1.06% in the study population of 1132 total joint arthroplasties performed in 1023 patients. Of the 12 patients requiring transfusion, 11 were female, ten occurred in patients undergoing total hip arthroplasty, and all 12 patients had a preoperative haemoglobin level less than 130 g/l. Operative duration and surgical blood loss were significantly greater in those patients requiring blood transfusion. Nearly all patients requiring transfusion had a history of, or risk factors for, cardiovascular disease. Potassium supplementation was required in 15.5% of the study cohort; 72% of these patients receiving potassium presented with a potassium level less than 4 mmol/l during preoperative testing, while the remaining 28% had a past medical history of either significant anaemia, cardiopulmonary, cardiovascular, or renal diseases that had required substantial medical management. Conclusion. A consistent blood-conserving perioperative strategy effectively minimized need for blood transfusion in total joint arthroplasty patients below previously reported rates in the literature. We suggest that postoperative full blood counts and basic metabolic panels should not routinely be ordered in these patients unless their preoperative haemoglobin and potassium is below 130 g/dl or 4 mmol/l respectively, and they have medical comorbidities

Metal-on-metal hip bearings are being implanted into younger patients. The consequence of elevated levels of potentially carcinogenic metal ions is therefore a cause for concern. We have determined the levels of cobalt (Co), chromium (Cr), titanium (Ti) and vanadium (Va) in the urine and whole blood of patients who had had metal-on-metal and metal-on-polyethylene articulations in situ for more than 30 years. We compared these with each other and with the levels for a control group of subjects. We found significantly elevated levels of whole blood Ti, Va and urinary Cr in all arthroplasty groups. The whole blood and urine levels of Co were grossly elevated, by a factor of 50 and 300 times respectively in patients with loose metal-on-metal articulations when compared with the control group. Stable metal-on-metal articulations showed much lower levels. Elevated levels of whole blood or urinary Co may be useful in identifying metal-on-metal articulations which are loose

We report serum metal ion level data in patients with unilateral and bilateral hip resurfacing over a ten-year period. In these patients there is an increase in both cobalt and chromium levels above the accepted reference ranges during the first 18 months after operation. Metal ion levels remain elevated, but decline slowly for up to five years. However, the levels then appear to start rising again in some patients up to the ten-year mark. There was no significant difference in cobalt or chromium levels between men and women. These findings appear to differ from much of the current literature. The clinical significance of a raised metal ion level remains under investigation

Aims. To determine whether there is any association between glomerular filtration rate (GFR) and blood cobalt (Co) and chromium (Cr) levels in patients with metal-on-metal (MoM) hip arthroplasty. Patients and Methods. We identified 179 patients with a unilateral 36 mm diameter head as part of a stemmed Summit-Pinnacle MoM hip arthroplasty. GFR was calculated using the Modification of Diet in Renal Disease formula. Results. Normal renal function (GFR ≥ 90 ml/min/1.73 m. 2. ) was seen in 74 patients. Mild renal insufficiency (GFR 60 to 89 ml/min/1.73 m. 2. ) was seen in 90 patients and moderate renal insufficiency (GFR 30 to 59 ml/min/1.73 m. 2. ) in 15. There was no statistical difference in Co and Cr levels between patients with normal renal function and those with mild or moderate renal insufficiency. No correlation was seen between creatinine and blood metal ion levels or between GFR and blood metal ion levels. Linear regression analysis did not show any association between Co and Cr levels and GFR. Conclusion. We did not find any association between GFR and blood metal ion levels. Consequently, the accumulation of Co and Cr in blood due to renal insufficiency does not seem to be a major risk in patients with mild or moderate renal insufficiency. Cite this article Bone Joint J 2017;99-B:1147–52

Objectives. Alarm over the reported high failure rates for metal-on-metal (MoM) hip implants as well as their potential for locally aggressive Adverse Reactions to Metal Debris (ARMDs) has prompted government agencies, internationally, to recommend the monitoring of patients with MoM hip implants. Some have advised that a blood ion level >7 µg/L indicates potential for ARMDs. We report a systematic review and meta-analysis of the performance of metal ion testing for ARMDs. Methods. We searched MEDLINE and EMBASE to identify articles from which it was possible to reconstruct a 2 × 2 table. Two readers independently reviewed all articles and extracted data using explicit criteria. We computed a summary receiver operating curve using a Bayesian random-effects hierarchical model. Results. Our literature search returned 575 unique articles; only six met inclusion criteria defined a priori. The discriminative capacity of ion tests was homogeneous across studies but that there was substantial cut-point heterogeneity. Our best estimate of the “true” area under curve (AUC) for metal ion testing is 0.615, with a 95% credible interval of 0.480 to 0.735, thus we can state that the probability that metal ion testing is actually clinically useful with an AUC ≥ 0.75 is 1.7%. Conclusion. Metal ion levels are not useful as a screening test for identifying high risk patients because ion testing will either lead to a large burden of false positive patients, or otherwise marginally modify the pre-test probability. With the availability of more accurate non-invasive tests, we did not find any evidence for using blood ion levels to diagnose symptomatic patients. Cite this article: M. Pahuta, J. M. Smolders, J. L. van Susante, J. Peck, P. R. Kim, P. E. Beaule. Blood metal ion levels are not a useful test for adverse reactions to metal debris: a systematic review and meta-analysis. Bone Joint Res 2016;5:379–386. DOI: 10.1302/2046-3758.59.BJR-2016-0027.R1

In a randomised study, 28 patients with a mean age of 62.2 years (32 to 81) with osteoarthritis or avascular necrosis of the hip received either a ceramic-on-ceramic or a metal-on-metal total hip replacement. Apart from the liners the acetabular and femoral components were made of Ti-Al-Nb alloy. The serum aluminium and cobalt levels were measured before, and at one year after surgery. The 15 patients in the ceramic-on-ceramic group had a median pre-operative aluminium level of 1.3 μg/l (0.25 to 8.4) and a cobalt level below the detection limit. At one year the aluminium level was 1.1 μg/l (0.25 to 2.3) and the cobalt level was 0.4 μg/l (0.15 to 0.7). The 13 patients in the metal-on-metal group had a median pre-operative aluminium level of 1.9 μg/l (0.25 to 4.4) and a cobalt level below the detection limit. At one year the median aluminium level was 0.9 μg/l (0.25 to 3.9) whereas the cobalt level was 1.4 μg/l (0.5 to 10.5). This increase in the cobalt level at one year was significant (p < 0.001). Our findings indicate that ceramic-on-ceramic bearings do not cause elevated levels of serum aluminium in the first post-operative year

We retrospectively analysed concentrations of chromium and cobalt ions in samples of synovial fluid and whole blood taken from a group of 92 patients with failed current-generation metal-on-metal hip replacements. We applied acid oxidative digestion to our trace metal analysis protocol, which found significantly higher levels of metal ion concentrations in blood and synovial fluid than a non-digestive method. Patients were subcategorised by mode of failure as either ‘unexplained pain’ or ‘defined causes’. Using this classification, chromium and cobalt ion levels were present over a wider range in synovial fluid and not as strongly correlated with blood ion levels as previously reported. There was no significant difference between metal ion concentrations and manufacturer of the implant, nor femoral head size below or above 50 mm. There was a moderately positive correlation between metal ion levels and acetabular component inclination angle as measured on three-dimensional CT imaging. Our results suggest that acid digestion of samples of synovial fluid samples is necessary to determine metal ion concentrations accurately so that meaningful comparisons can be made between studies

Metal-on-metal bearings for total hip replacement (THR) are becoming increasingly popular. Improved wear characteristics mean that these articulations are being inserted into younger patients in the form of THR and resurfacing procedures. This has led to concerns regarding potential carcinogenicity because of the increased exposure to metal ions that the procedure brings. We have studied the serum cobalt and chromium concentrations in patients who had primary, well-fixed Ring metal-on-metal THRs for more than 30 years. The levels of cobalt and chromium were elevated by five and three times, respectively compared with those in our reference groups. Metal-on-metal articulations appear to be the source of metal ions throughout the life of the prosthesis. In three patients who had undergone revision of a previous metal-on-metal THR to a metal-on-polyethylene replacement the levels of metal ions were within the normal range. The elevations of cobalt and chromium ions seen in our study were comparable with those in patients with modern metal-on-metal THRs

Wear of metal-on-metal bearings causes elevated levels of cobalt and chromium in blood and body fluids. Metal-on-metal bearings have two distinct wear phases. In the early phase, the wear rate is high. Later, it decreases and the bearing enters a steady-state phase. It is expected that as the wear rates decline, the level of cobalt detected in plasma will also decrease. We studied the baseline and exercise-related cobalt rise in 21 patients (13 men and eight women) with a mean age of 54 years (38 to 80) who had undergone successful hip resurfacing at a mean of 44 months (10 to 96) earlier. Our results showed that circulating baseline cobalt levels were not significantly correlated with the time since implantation (r = 0.08, p = 0.650). By contrast, the exercise-related cobalt rise was directly correlated with the inclination angle of the acetabular component (r = 0.47, p = 0.032) and inversely correlated with the time since implantation (r = −0.5, p = 0.020). Inclination of the acetabular component should be kept less than 40° to decrease the production of wear debris