JBJS, (Br) Reaches New Heights!
The Journal of Bone and Joint Surgery, British Volume is pleased to announce that its Impact Factor now stands at 2.196.
The 2008 Impact Factor shows an increase for the 5th year running, and puts JBJS (Br) into the top 10 journals in the Orthopaedics category. In addition, JBJS (Br) is pleased to announce that its 5-year Impact Factor stands at 2.837 and its cited half-life is >10.0 years.
The Impact Factor is a part of Journal Citation Reports© from Thomson Reuters that help to measure and evaluate research influence at journal and category level, you can find out more about them here.
New tests for the investigation of patients with painful metal-on-metal resurfacing arthroplasties
This paper investigates 26 patients with painful metal-on-metal resurfacing arthroplasties and describes three tests for the investigation of the phenomenon. The tests are metal artefact-reduction MRI, 3-D CT measurement of the position of the component and inductively-coupled plasma mass spectrometry.
Current techniques for assessing patients with painful MOM hips are the same as for painful non-MOM hips, however, this research demonstrates that hip resurfacing appears to have specific modes of failure which are not detectable using these methods. Therefore, the authors investigated the use of metal artefact-reduction MRI, 3-D CT measurement of the position on the component and inductively-coupled plasma mass spectrometry analysis of cobalt and chromium levels in the whole blood.
As an aseptic lymphocyte-dominated vasculitis-lesion can be a possible cause of unexplained pain in a MOM hip the 26 patients were tested with MRI and 16 hips showed periprosthetic lesions, with 14 collections of fluid and two soft tissue masses. The diagnosis of aseptic lymphocyte-dominated vasculitis-lesion can only be made from tissue samples, usually collected during revision. Therefore, because the lesions were seen in both men and women and in symptomatic and asymptomatic hips the significance of this finding is unclear.
It has also been suggested that unexplained hip pain is associated with high levels of metal ions in the blood so the levels of cobalt and chromium may be biomarkers of early failure. In the patients tested, the levels of blood metal ions tended to be higher in painful compared to well-functioning metal-on-metal hips. Specifically the level of cobalt were significantly greater, suggesting that painful hip resurfacings have greater wear rates. However, the levels of chromium were barely raised in patients with unilateral MOM hips and therefore analysis of blood metals ions as a screening test for painful MOM is likely to be sensitive but not specific.
The 3-D CT scans showed that the median inclination of the acetabular component was 55° and its positioning was outside the Lewinnk safe zone in 13 of 16 cases. The position of the component may influence the risk of failure of a MOM hip because suboptimal acetabular version may cause impingement, and inclination angles of greater than 50° may cause high rates of wear.
The authors protocol for the painful MOM hip demonstrated a high probability of periprosthetic masses on metal artefact reduction sequences, a higher blood metal level than in the well-functioning MOM hip and a position of the component outside the Lewinnek safe zone. Taken together, these observations may help to determine causes of failure, indicate the most appropriate treatment and aid the choice of prosthesis if replacing the contralateral hip.
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Reducing Blood Loss after THR
Post-operative anaemia is a recognised complication of total hip replacement and can increase the length of hospital stay, delay rehabilitation and is poorly tolerated by patients with vascular disease. Current practice sees homologous blood transfusion commonly used to correct blood loss, however, it is associated with risk of infection, viral transmission, fluid overload and high cost. Thus various blood-conserving techniques are also used to reduce the need for homologous blood transfusion, of these fibrinolytic inhibitors, such as tranexamic acid have been shown to be cost-effective in reducing blood loss in surgery.
However, the efficacy of tranexamic acid in THR remains uncertain and therefore this study investigated the effect of a standardised intravenous bolus dose of 1g of tranexamic acid, given at the induction of anaesthesia in patients undergoing THR and tested the potential prothrombotic effect by undertaking routine venography. In all, 36 patients received 1g of tranexamic acid and 37 no tranexamic acid, with blood loss measured directly per-operatively and indirectly post-operatively.
The tranexamic acid group required fewer transfusions and had no increased incidence of deep-vein thrombosis. The tranexamic acid was shown to reduce both early post-operative blood loss and total blood loss, but not the intra-operative blood loss. The reduction in early post-operative blood loss was more marked in women and this result was dose related. Therefore, the authors conclude that 'the administration of a standardised pre-operative 1g of tranexamic acid was cost-effective in reducing the blood loss and transfusion requirements after total hip replacement, especially in women'.
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MOM, Metal Ions and Lymphopenia
Metal-on-metal hip replacement and resurfacing have become the most commonly used type of procedure in the United Kingdom for patients who are < 60 years of age with osteoarthritis. Therefore, this research consisted of a cross-sectional study with analysis of demographic, clinical and laboratory characteristics of patients who had undergone metal-on-metal hip resurfacing, ceramic-on-ceramic and metal-on-polyethylene hip replacement to assess whether there was a relationship between MOM replacements and circulating metal ions in the blood, and absolute numbers of circulating lymphocytes.
There were 164 patients in the study, of which 106 had MOM hips, all were aged < 65 years and had pre-operative diagnosis of osteoarthritis and no pre-existing immunological disorders. Patients were excluded if their replacement had taken place less than six months previously, thereby avoiding the high-wearing, bedding-in phase. Blood samples were taken using a plastic needle cannula to avoid metal contamination.
The results showed that 'there were significant differences in the levels of metal ions in the whole blood and in the absolute lymphocyte counts'. A group of 10 patients of the 106 from the MOM group had circulating levels of chromium greater than 5 parts per billion. Therefore, the authors conclude that 'patients with MOM hips had reduced peripheral blood counts of T-lymphocytes in particular and B-lymphocytes when compared with control subjects with hip replacements which did not produce metal wear debris'. Although the effect of reduced lymphocytes is unknown, there has been a link between high levels of cobalt and chromium and DNA damage of lymphocytes and the authors recommend that long-term studies need to be conducted to determine whether the moderate lymphopenia associated with MOM hip replacements is detrimental or even beneficial to longevity of the replacement.
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The Anatomical Graduated Component Total Knee Replacement
This study examined the 20-year follow-up of the cemented Anatomical Graduated Component total knee replacement carried out between 1983 and 2004. The results showed that the overall survival rate at 20 years was 97.8% with revision of the tibial or femoral component as the endpoint. The survival rate at 20 years of the tibial component was 98.3% and the femoral component was 99.4%. None of the 36 implants at the 20 year follow-up had been revised for polyethylene wear or osteolysis, which may be a reflection of the use of a non-modular, compression-moulded polyethylene implant, since other studies have found polyethylene wear to be a leading cause of failure leading to revision.
Therefore, the authors attribute the success of the Anatomical Graduated Component total knee replacement to its relatively unconstrained articular geometry and the durability of a non-modular metal-backed tibial component with compression-moulded polyethylene.
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Fragility Fractures and Osteoporosis
Low energy fractures of the proximal humerus indicate osteoporosis and it is important to direct treatment in order to prevent further fractures. Therefore, in this study the authors collected data from 79 patients with fractures of the proximal humerus in order to determine if current guidelines on measurement of bone mineral density at the hip and lumbar spine were adequate to stratify the risk and to guide the treatment of osteoporosis.
The World Health Organisation defines osteoporosis by comparing the bone mineral density with that of a gender-matched, healthy young adult reference population. A T-score in women of less than -2.5 at any one of three skeletal sites, the femur, the lumbar spine or the distal radius is the WHO 'gold standard' for diagnosing osteoporosis. However, the most common clinical method for assessing the BMD is dual-energy x-ray absorbtiometry of the central skeleton taken at the hip and lumbar spine. Therefore, the authors decided to analyse the sensitivity of these sites and the distal radius in diagnosing osteoporosis in accordance with WHO criteria.
The results show that 'there is a wide variation in the BMD when measured at different skeletal sites' and that when considering injuries to the upper limb, the BMD measured at the distal radius may represent the risk of osteoporotic humeral fractures better than that measured at the axial skeleton or lower limbs. This is because the distal radius has a large proportion of cancellous bone which is affected to a greater extent by age-related changes in the BMD. Therefore, the authors conclude that 'measurement of the BMD at the hip and lumbar spine, if used alone, may underestimate the risk of osteoporosis in the upper limb' and that measurement of the BMD at the radius should not be omitted when osteoporosis is being investigated.
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Oral Rivaroxaban as Prevention for Symptomatic Venous Thromboembolism
In this study data from three studies comparing the new oral anticoagulant rivaroxaban against enoxaparin injected subcutaneously was assessed and conclusions drawn about effectiveness of both types of treatment.
Rivaroxaban was started six to eight hours after surgery, whereas enoxaparin was injected the previous evening and then at six to eight hours following wound closure. Thereafter, both were administered every 24 hours in a double-dummy fashion: all patients received either placebo injections or placebo tablets.
The results showed that of 9581 patients in the study across 487 centres in 38 countries rivaroxaban significantly reduced the incidence of symptomatic venous thromoembolism compared with enoxaparin (0.4% and 0.8% respectively) without an increase in the risk of major bleeding in patients undergoing elective hip and knee replacement surgery.
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Aspirin as a Prophylaxis for Fatal Pulmonary Embolism
A study published today provides results which challenge the current NICE guidelines (set in April 2007) relating to the use of low-molecular weight heparin (LMWH) rather than aspirin as a thromboprophylaxis following orthopaedic surgery.
Currently the guidance states that LMWH is preferable to aspirin and partly is based on two assumptions that the report's authors wished to test: that chemical and/or mechanical prophylaxis will reduce these complications and that orthopaedic operations, in particular elective hip and knee replacements, are high-risk.
The study analysed over 4,000 patients undergoing primary joint replacement, the majority of whom received aspirin only as a chemical prophylaxis. The overall death rate was 0.31% and the rate of fatal pulmonary embolism was 0.07%, while the overall mortality rate in the general population for gender and age matched controls was 50% more than those undergoing surgery.
Therefore, the report's authors conclude that 'it does seem unlikely that the adoption of LMWH could produce any further significant reduction on observed mortality in this patient group'. In addition, 'the fatal pulmonary embolism rate (0.07%) suggests that this is a rare event even after elective total joint replacement if aspirin is given', meaning that aspirin is an effective thromprophylaxis for patients after orthopaedic surgery.
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Early Failure of Knee Replacements
This study investigated a series of Kinemax knee replacements where the survival rate was only 75% at nine years, compared with previously recorded rates of 96% over ten years and tried to ascertain the reason for the significantly lower survival rate.
The authors discovered that on revision 'the most striking feature was polyethylene wear' on the implant and therefore undertook to have the removed implants independently anaylsed for abnormalities.
The findings of scanning the implants using electron microscopy were type 2 fusion defects in the polyethylene, indicating incomplete boundary fusion. Therefore, the authors 'consider that the failure of the Kinemax implants in our cohort was due to material failure of the UHMWPE, probably at the time of manufacture, exacerbated by post-manufacturing oxidation'.
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