The biological significance of cobalt-chromium wear particles from metal-on-metal hip replacements may be different to the effects of the constituent metal ions in solution. Bacteria may be able to discriminate between particulate and ionic forms of these metals because of a transmembrane nickel/cobalt-permease. It is not known whether wear particles are bacteriocidal. We compared the doubling time of coagulase negative staphylococcus, Staphylococcus aureus and methicillin resistant S. aureus when cultured in either wear particles from a metal-on-metal hip simulator, wear particles from a metal-on-polyethylene hip simulator, metal ions in solution or a control. Doubling time halved in metal-on-metal (p = 0.003) and metal-on-polyethylene (p = 0.131) particulate debris compared with the control. Bacterial nickel/cobalt-transporters allow metal ions but not wear particles to cross bacterial membranes. This may be useful for testing the biological characteristics of different wear debris. This experiment also shows that metal-on-metal hip wear debris is not bacteriocidal

Aims. The treatment of patients with allergies to metal in total joint arthroplasty is an ongoing debate. Possibilities include the use of hypoallergenic prostheses, as well as the use of standard cobalt-chromium (CoCr) alloy. This non-designer study was performed to evaluate the clinical outcome and survival rates of unicondylar knee arthroplasty (UKA) using a standard CoCr alloy in patients reporting signs of a hypersensitivity to metal. Patients and Methods. A consecutive series of patients suitable for UKA were screened for symptoms of metal hypersensitivity by use of a questionnaire. A total of 82 patients out of 1737 patients suitable for medial UKA reporting cutaneous metal hypersensitivity to cobalt, chromium, or nickel were included into this study and prospectively evaluated to determine the functional outcome, possible signs of hypersensitivity, and short-term survivorship at a minimum follow-up of 1.5 years. Results. At a mean follow-up of three years (1.5 to 5.7), no local or systemic symptoms of hypersensitivity to metal were observed. One patient underwent revision surgery to a bicondylar prosthesis due to a tibial periprosthetic fracture resulting in a survival rate of 98.8% (95% confidence interval (CI) 91.7 to 99.8; number at risk, 28) at three years with the endpoint of revision for any reason and a survival rate of 97.6% (95% CI 90.6 to 99.3; number at risk, 29) for the endpoint of all reoperations. Clinical outcome was good to excellent with a mean Oxford Knee Score of 42.5 (. sd. 2.5; 37 to 48). Conclusion. This study is the first demonstrating clinical results and survival analysis of UKA using a CoCr alloy in patients with a history of metal hypersensitivity. Functional outcome and survivorship are on a high-level equivalent to those reported for UKA in patients without a history of metal hypersensitivity. No serious local or systemic symptoms of metal hypersensitivity could be detected, and no revision surgery was performed due to an adverse reaction to metal ions

Some of the component metals of the alloys used for total joint prostheses are toxic and dissolve in the body fluids. It is important to establish how toxic these metals are and to assess the risk of localised tissue necrosis around the prostheses. This has been investigated by incubating primary monolayer cultures of human synovial fibroblasts with various preparations of metals for periods up to 18 days. Morphological changes were evident after exposure to cobalt chloride at a concentration of 50 nanomoles per millilitre and to nickel chloride at 200 nanomoles per millilitre. Chromic chloride, ammonium molybdate and ferric chloride produced no changes up to 500 nanomoles per millilitre. Cultures exposed to particulate pure metals were poisoned by cobalt and vanadium but were not affected under the same conditions by nickel, chromium, molybdenum, titanium or aluminium. Particulate cobalt and vanadium were probably toxic due to their relatively high solubility (four and one micromoles per millilitre respectively after seven days incubation). Particulate nickel also dissolved (three nanomoles per millilitre after seven days) but not in sufficient quantities to be toxic. It appears, therefore, that potentially the most harmful components are cobalt from cobalt-chromium alloy, nickel from stainless steel, and vanadium from titanium alloy. As far as can be estimated, the only combination of materials which is likely to give rise to toxic levels of metal under clinical conditions, is cobalt-chromium alloy articulating against itself to produce relatively high levels of cobalt

Future devices will be more reliable, although more versatile and complex. They will require less attention and maintenance, but more skill when maintenance or repair is necessary. They will require less training of the patient before he can use them successfully and will be more immediately responsive to his wishes, giving smooth, integrated movements, varying with the intensity and direction of his effort.

1. The various methods of powering orthoses are described.

2. The details of control systems are given.

3. The applications of these systems are described.

We have assessed the influence of somatisation on the outcome of treatment in 81 patients with chronic low back pain.

All, irrespective of whether treatment was surgical or conservative, had a significantly better (p < 0.001) health-related quality of life at follow-up on all but one scale of the SF-36. Lower health-related quality of life at follow-up correlated significantly with a higher tendency to somatise before treatment and at follow-up. A logistic regression analysis yielded two factors which predicted the outcome; somatisation (p < 0.001) and ‘doctor shopping’ (the number of physicians consulted before the present inpatient treatment, p < 0.001). These factors accurately distinguished between patients with good and those with poor outcomes in 82%. Patients with somatisation and ‘doctor shopping’ were at a higher risk for a poor outcome. The results show the relevance of somatisation in the outcome of treatment in patients with low back pain.

This is part of a larger study designed to investigate the action of particulate metals of orthopaedic interest on tissues. Damaging effects were determined by cytological examination and the assay of two enzymes. Lactic dehydrogenase (LDH) if released into the supernatant indicates a damaged cell membrane; decreased intracellular levels of glucose-6-phosphate dehydrogenase (G6PD) indicates a lowered phagocytic capacity of the cells. Soluble and wear products around implanted prostheses could facilitate late infections by impairing local reactions to bacteria. Particulate cobalt, nickel and cobalt-chromium alloy were found to damage the cells and to cause LDH release. G6PD was found to have a lower activity in the cells exposed to these materials. In contrast, titanium, chromium and molybdenum were well tolerated by macrophages and had no effect on the distribution and activity of either enzyme. The solubility of these metals in the culture medium was also measured

Wear debris was extracted from 21 worn hip and knee replacements. Its mutagenic effects were tested on human cells in tissue culture using the micronucleus assay and fluorescent in situ hybridisation. The extracted wear debris increased the level of micronuclei in a linear dose-dependent manner but with a tenfold difference between samples. The concentration of titanium +/− vanadium and aluminium within the wear debris was linearly related both to the level of centromere-positive micronuclei in tissue culture, indicating an aneuploid event, and to the level of aneuploidy in vivo in peripheral blood lymphocytes. The concentration of cobalt and chromium +/− nickel and molybdenum in the wear debris correlated with the total index of micronuclei in tissue culture, both centromere-positive and centromere-negative i.e. both chromosomal breakage and aneuploidy events. The results show that wear debris can damage chromosomes in a dose-dependent manner which is specific to the type of metal. The results from studies in vitro correlate with those in vivo and suggest that the wear debris from a worn implant is at least partly responsible for the chromosomal damage which is seen in vivo

1. Experiments using radio-isotope techniques show that whenever an orthopaedic appliance is inserted into the body tiny fragments of the instruments used to handle it become detached and welded on to the surface of the buried metal. 2. There is evidence that these particles of non-passive tool-metal may cause a small but continuing dissolution of the stainless metal to which they are attached, and that this dissolution, although too small to be detected as visible corrosion, may produce an adverse tissue reaction. 3. In samples of human tissue taken from sites adjacent to buried metal the greatest level of tissue reaction and the highest concentration of iron were found near those parts of the appliances that had been handled with the tools and received the greatest amount of transferred metal. 4. Spectroscopic analyses of similar samples confirmed that the concentration of metal in the tissues surrounding a buried appliance correlates closely with the distribution on its surface of transferred tool metal. Particularly high concentrations of chromium, nickel, and cobalt were found near regions where the transfer had been heavy. The dissolution was not limited to the non-passive foreign metal; the stainless appliance was also dissolved in those regions. 5. The influence of the manner of handling the tools on the amount and distribution of transfer has been studied, and suggestions are made whereby the transfer might be reduced

Aims

It has previously been shown that higher-volume hospitals have better outcomes following revision total knee arthroplasty (rTKA). We were unable to identify any studies which investigated the effect of surgeon volume on the outcome of rTKA. We sought to investigate whether patients of high-volume (HV) rTKA surgeons have better outcomes following this procedure compared with those of low-volume (LV) surgeons.

Aims

Porous metaphyseal cones can be used for fixation in revision total knee arthroplasty (rTKA) and complex TKAs. This metaphyseal fixation has led to some surgeons using shorter cemented stems instead of diaphyseal engaging cementless stems with a potential benefit of ease of obtaining proper alignment without being beholden to the diaphysis. The purpose of this study was to evaluate short term clinical and radiographic outcomes of a series of TKA cases performed using 3D-printed metaphyseal cones.

Aims

A limited number of investigations with conflicting results have described perivascular lymphocytic infiltration (PVLI) in the setting of total knee arthroplasty (TKA). The purpose of this study was to determine if PVLI found in TKAs at the time of aseptic revision surgery was associated with worse clinical outcomes and survivorship.

Aims

This study aimed to determine if macrophages can attach and directly affect the oxide layers of 316L stainless steel, titanium alloy (Ti6Al4V), and cobalt-chromium-molybdenum alloy (CoCrMo) by releasing components of these alloys.

Aims

Our intention was to investigate if the highly porous biological fixation surfaces of a new 3D-printed total knee arthroplasty (TKA) achieved adequate fixation of the tibial and patellar components to the underlying bone.

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.

Abnormal wear of cobalt-containing metal-on-metal joints is associated with inflammatory pseudotumours. Cobalt ions activate human toll-like receptor 4 (TLR4), which normally responds to bacterial lipopolysaccharide (LPS) in sepsis. Activation of TLR4 by LPS increases the expression of chemokines IL-8 and CXCL10, which recruit leukocytes and activated T-cells, respectively. This study was designed to determine whether cobalt induces a similar inflammatory response to LPS by promoting the expression of IL-8 and CXCL10. A human monocytic cell line, derived from acute monocytic leukaemia, was treated with cobalt ions and expression of IL-8 and CXCL10 measured at mRNA and protein levels. Cobalt-treated macrophages showed a 60-fold increase in IL-8 mRNA, and an eightfold increase in production of the mature chemokine (both p < 0.001); expression of the CXCL10 gene and protein was also significantly increased by cobalt (both p < 0.001). Experiments were also performed in the presence of CLI-095, a TLR4-specific antagonist which abrogated the cobalt-mediated increase in IL-8 and CXCL10 expression.

These findings suggest that cobalt ions induce inflammation similar to that observed during sepsis by the simultaneous activation of two TLR4-mediated signalling pathways. These pathways result in increased production of IL-8 and CXCL10, and may be implicated in pseudotumour formation following metal-on-metal replacement.

Cite this article: Bone Joint J 2014; 96-B:1172–7.

We prospectively assessed the efficacy of a ceramic-on-metal (CoM) hip bearing with uncemented acetabular and femoral components in which cobalt­–chrome acetabular liners and alumina ceramic heads were used.

The cohort comprised 94 total hip replacements (THRs) in 83 patients (38 women and 45 men) with a mean age of 58 years (42 to 70). Minimum follow-up was two years. All patients had pre- and post-operative assessment using the Western Ontario and McMaster Universities osteoarthritis index (WOMAC), Oxford hip score and Short-Form 12 scores. All showed a statistically significant improvement from three months post-operatively onwards (all p < 0.001).

After two years whole blood metal ion levels were measured and chromosomal analysis was performed. The levels of all metal ions were elevated except vanadium. Levels of chromium, cobalt, molybdenum and titanium were significantly higher in patients who underwent bilateral THR compared with those undergoing unilateral THR (p < 0.001). Chromosomal analysis demonstrated both structural and aneuploidy mutations. There were significantly more breaks and losses than in the normal population (p < 0.001). There was no significant difference in chromosomal aberration between those undergoing unilateral and bilateral procedures (all analyses p ≥ 0.62).

The use of a CoM THR is effective clinically in the short-term, with no concerns, but the significance of high metal ion levels and chromosomal aberrations in the long-term remains unclear.

Cite this article: Bone Joint J 2013;95-B:1040–44.

Peri-articular soft-tissue masses or ‘pseudotumours’ can occur after large-diameter metal-on-metal (MoM) resurfacing of the hip and conventional total hip replacement (THR). Our aim was to assess the incidence of pseudotumour formation and to identify risk factors for their formation in a prospective cohort study.

A total of 119 patients who underwent 120 MoM THRs with large-diameter femoral heads between January 2005 and November 2007 were included in the study. Outcome scores, serum metal ion levels, radiographs and CT scans were obtained. Patients with symptoms or an identified pseudotumour were offered MRI and an ultrasound-guided biopsy.

There were 108 patients (109 hips) eligible for evaluation by CT scan at a mean follow-up of 3.6 years (2.5 to 4.5); 42 patients (39%) were diagnosed with a pseudotumour. The hips of 13 patients (12%) were revised to a polyethylene acetabular component with small-diameter metal head. Patients with elevated serum metal ion levels had a four times increased risk of developing a pseudotumour.

This study shows a substantially higher incidence of pseudotumour formation and subsequent revisions in patients with MoM THRs than previously reported. Because most revision cases were identified only after an intensive screening protocol, we recommend close monitoring of patients with MoM THR.

The use of large-diameter metal-on-metal (MoM) components in total hip arthroplasty (THA) is associated with an increased risk of early failure due to adverse local tissue reaction to metal debris (ARMD) in response to the release of metal ions from the bearing couple and/or head-neck taper corrosion. The aim of this paper was to present a review of the incidence and natural history of ARMD and the forms of treatment, with a focus on the need for and extent of resection or debulking of the pseudotumour. An illustrative case report is presented of a patient with an intra-pelvic pseudotumour associated with a large diameter MoM THA, which was treated successfully with revision of the bearing surface to a dual mobility couple and retention of the well-fixed acetabular and femoral components. The pseudotumour was left in situ. Resolution of the intra-pelvic mass and normalisation of metal ion levels was observed seven months post-operatively.

Cite this article: Bone Joint J 2016;98-B:736–40.

We report 17 patients (20 hips) in whom metal-on-metal resurfacing had been performed and who presented with various symptoms and a soft-tissue mass which we termed a pseudotumour. Each patient underwent plain radiography and in some, CT, MRI and ultrasonography were also performed. In addition, histological examination of available samples was undertaken.

All the patients were women and their presentation was variable. The most common symptom was discomfort in the region of the hip. Other symptoms included spontaneous dislocation, nerve palsy, a noticeable mass or a rash. The common histological features were extensive necrosis and lymphocytic infiltration. To date, 13 of the 20 hips have required revision to a conventional hip replacement. Two are awaiting revision.

We estimate that approximately 1% of patients who have a metal-on-metal resurfacing develop a pseudotumour within five years. The cause is unknown and is probably multifactorial. There may be a toxic reaction to an excess of particulate metal wear debris or a hypersensitivity reaction to a normal amount of metal debris. We are concerned that with time the incidence of these pseudotumours may increase. Further investigation is required to define their cause.