FM127: Systemic metal ion levels in patients with modular neck total hip arthroplasties: a prospective cohort study

There is increasing evidence that modular neck stems are prone to corrosion-related complications. Recent studies showed elevated metal ions levels and occasional pseudotumor formation in patients with such implants. The purpose of this study was to compare systemic metal-ion levels in patients after primary THA with modular neck stems to those of patients after non-modular implants. To our knowledge, this is the first cohort study including a control group, THA without CoCr heads and dry-assembled neck-stem connections. Methods: 50 patients after THA at a minimum follow-up of 1 year have been selected for the study. Patients with multiple prosthesis or other implants have been deselected. All received a cementless SPS stem from Symbios (Ti6Al4V). 40 patients have the modular neck (CoCr) version and 10 a monobloc version. All bearings were either ceramic-ceramic or ceramic-polyethylene to minimize other sources of CoCr ion release. In the modular group, the neck was chosen pre-operatively based on a 3D planning, allowing for a dry assembly of the stem and neck on the back table before implantation. A plasma system coupled to mass spectrometry was used for a complete elementary quantification in blood and serum separately. Clinical outcome was measured using the Oxford Hip Score. Results : Complete data sets of 29 patients (24 in the modular neck-group (10male, mean age 63y, 35-84y) and 5 in the monobloc-group (3 male, 69 y, 51-83y) are available to date. Mean Co blood levels were .95 ug/L (.14-12.4) in the modular group vs .27 ug/L (.10-.73) in the monobloc group (p=.2). Respective values for Cr were significantly higher in the modular group (.99 g/L; range .75-1.21) compared to those in the monobloc group (.74 g/L ;.62-.86; p=.001). No significant difference was found when comparing serum levels. 5/24 patients had Co levels above 1 g/L (12/24 for Cr), which is by some considered as a relevant elevation. The maximum Co level was measured in an asymptomatic patient. The Oxford Hip Scores were similar in both groups. Conclusion: Cr levels were significantly elevated in the modular neck group compared to those in the monobloc group. 1/24 patients with a modular prosthesis exhibited Co levels, which are beyond the threshold accepted even for metal-on-metal bearing couples. These results have contributed to our decision to abandon the use of modular neck stems. Routine follow-up including annual measurements of systemic CoCr concentrations should be considered.

Improved diagnosis of periprosthetic joint infection by multiplex PCR of sonication fluid from removed implants.

The microbiological diagnosis of periprosthetic joint infection (PJI) is crucial for successful antimicrobial treatment. Cultures have limited sensitivity, especially in patients receiving antibiotics. We evaluated the value of multiplex PCR for detection of microbial DNA in sonication fluid from removed orthopedic prostheses. Cases of PJI in which the prosthesis (or part of it) was removed were prospectively included. The removed implant was sonicated, and the resulting sonication fluid was cultured and subjected to multiplex PCR. Of 37 PJI cases (17 hip prostheses, 14 knee prostheses, 4 shoulder prostheses, 1 elbow prosthesis, and 1 ankle prosthesis), pathogens were identified in periprosthetic tissue in 24 (65%) cases, in sonication fluid in 23 (62%) cases, and by multiplex PCR in 29 (78%) cases. The pathogen was detected in 5 cases in sonication fluid only (Propionibacterium acnes in all cases; none of these patients had previously received antibiotics) and in 11 cases by multiplex PCR only (all of these patients had previously received antibiotics). After exclusion of 8 cases caused by P. acnes or Corynebacterium species, which cannot be detected due to the absence of specific primers in the PCR kit, sonication cultures were positive in 17 cases and multiplex PCR sonication cultures were positive in 29 cases (59% versus 100%, respectively; P < 0.01). Among 19 cases (51%) receiving antibiotics, multiplex PCR was positive in all 19 (100%), whereas sonication cultures grew the organism in 8 (42%) (P < 0.01). Multiplex PCR of sonication fluid is a promising test for diagnosis of PJI, particularly in patients who previously received antibiotics. With modified primer sets, multiplex PCR has the potential for further improvement of the diagnosis of PJI.

Anévrismes complexes de l'aorte abdominale: la chirurgie ouverte est-elle obsolète [The complex aortic abdominal aneurysm: is open surgery old fashion?].

Open surgery is still the main treatment of complex abdominal aortic aneurysm. Nevertheless, this approach is associated with major complications and high mortality rate. Therefore the fenestrated endograft has been used to treat the juxtarenal aneurysms. Unfortunately, no randomised controlled study is available to assess the efficacy of such devices. Moreover, the costs are still prohibitive to generalise this approach. Alternative treatments such as chimney or sandwich technique are being evaluated in order to avoid theses disadvantages. The aim of this paper is to present the endovascular approach to treat juxtarenal aneurysm and to emphasize that this option should be used only by highly specialized vascular centres.

Hemodialysis for cefepime intoxication: A case report

Introduction: We report a case of cefepime intoxication with acute severe neurologic symptoms, which was treated by temporary hemodialysis. Patients (or Materials) and Methods: Cefepime 2 g BID for endovascular prosthesis infection was prescribed to a frail, chronically ill 88-year-old woman with a serum creatinine of 199 μmol/L and an estimated creatinine clearance of 13 mL/min (Cockroft formula). Two days later, she was transferred to a neurocritical care unit because of acute aphasia, myoclonic jerks, and delirium with a Glasgow coma scale score of 12/15. The following day, in the absence of other causes, cefepime intoxication was hypothesized, and cefepime was withdrawn after a total of 7 doses = 14 g. Over the next 24 hours, two 3-hour hemodialysis (HD) sessions were performed under cefepime concentration monitoring. Results: Cefepime plasma levels were measured by liquid chromatography/ mass spectrometry. There is no validated reference range, but a study (Chapuis T et al, Critical Care, 2010) found a 50% risk of neurotoxicity with residual levels > 15 mg/L. In our patient, levels were 83.3 mg/L 10 hours after last dose, 24.1 mg/L immediately after the first HD session, 13.4 mg/L immediately before the second HD session, and 2.5 mg/L immediately after the second HD session. The patient made a full clinical recovery over the next 48 hours. The 70% to 80% fall in plasmatic levels observed during each HD session is in accordance with literature data (Schmaldienst S et al, Eur J Clin Pharmacol, 2000, and Manyor LM et al, Pharmacotherapy, 2008). According to kinetic simulation, cefepime dropped at a concentration < 15 mg/L 15 hours earlier with HD than it would have without. Conclusion: Neuropsychiatric adverse effects of beta-lactam antibiotics can be easily overlooked by clinicians. One should be especially cautious with their use in very old and frail patients in whom plasma creatinine poorly estimates renal function and cognitive impairment is highly prevalent. Temporary hemodialysis effectively clears cefepime, but its role in hastening clinical recovery may be limited.

Evaluation of peripheral arterial bypass grafts with multi-detector row CT angiography: comparison with duplex US and digital subtraction angiography.

PURPOSE: To assess the technical feasibility of multi-detector row computed tomographic (CT) angiography in the assessment of peripheral arterial bypass grafts and to evaluate its accuracy and reliability in the detection of graft-related complications, including graft stenosis, aneurysmal changes, and arteriovenous fistulas. MATERIALS AND METHODS: Four-channel multi-detector row CT angiography was performed in 65 consecutive patients with 85 peripheral arterial bypass grafts. Each bypass graft was divided into three segments (proximal anastomosis, course of the graft body, and distal anastomosis), resulting in 255 segments. Two readers evaluated all CT angiograms with regard to image quality and the presence of bypass graft-related abnormalities, including graft stenosis, aneurysmal changes, and arteriovenous fistulas. The results were compared with McNemar test with Bonferroni correction. CT attenuation values were recorded at five different locations from the inflow artery to the outflow artery of the bypass graft. These findings were compared with the findings at duplex ultrasonography (US) in 65 patients and the findings at conventional digital subtraction angiography (DSA) in 27. RESULTS: Image quality was rated as good or excellent in 250 (98%) and in 252 (99%) of 255 bypass segments, respectively. There was excellent agreement both between readers and between CT angiography and duplex US in the detection of graft stenosis, aneurysmal changes, and arteriovenous fistulas (kappa = 0.86-0.99). CT angiography and duplex US were compared with conventional DSA, and there was no statistically significant difference (P >.25) in sensitivity or specificity between CT angiography and duplex US for both readers for detection of hemodynamically significant bypass stenosis or occlusion, aneurysmal changes, or arteriovenous fistulas. Mean CT attenuation values ranged from 232 HU in the inflow artery to 281 HU in the outflow artery of the bypass graft. CONCLUSION: Multi-detector row CT angiography may be an accurate and reliable technique after duplex US in the assessment of peripheral arterial bypass grafts and detection of graft-related complications, including stenosis, aneurysmal changes, and arteriovenous fistulas.

Factors predisposing to dislocation after primary total hip arthroplasty: a multivariate analysis.

We conducted this study to determine the relative influence of various mechanical and patient-related factors on the incidence of dislocation after primary total hip asthroplasty (THA). Of 2,023 THAs, 21 patients who had at least 1 dislocation were compared with a control group of 21 patients without dislocation, matched for age, gender, pathology, and year of surgery. Implant positioning, seniority of the surgeon, American Society of Anesthesiologists (ASA) score, and diminished motor coordination were recorded. Data analysis included univariate and multivariate methods. The dislocation risk was 6.9 times higher if total anteversion was not between 40 degrees and 60 degrees and 10 times higher in patients with high ASA scores. Surgeons should pay attention to total anteversion (cup and stem) of THA. The ASA score should be part of the preoperative assessment of the dislocation risk.

A spatially explicit life cycle inventory of the global textile chain

Life cycle analyses (LCA) approaches require adaptation to reflect the increasing delocalization of production to emerging countries. This work addresses this challenge by establishing a country-level, spatially explicit life cycle inventory (LCI). This study comprises three separate dimensions. The first dimension is spatial: processes and emissions are allocated to the country in which they take place and modeled to take into account local factors. Emerging economies China and India are the location of production, the consumption occurs in Germany, an Organisation for Economic Cooperation and Development country. The second dimension is the product level: we consider two distinct textile garments, a cotton T-shirt and a polyester jacket, in order to highlight potential differences in the production and use phases. The third dimension is the inventory composition: we track CO2, SO2, NO (x), and particulates, four major atmospheric pollutants, as well as energy use. This third dimension enriches the analysis of the spatial differentiation (first dimension) and distinct products (second dimension). We describe the textile production and use processes and define a functional unit for a garment. We then model important processes using a hierarchy of preferential data sources. We place special emphasis on the modeling of the principal local energy processes: electricity and transport in emerging countries. The spatially explicit inventory is disaggregated by country of location of the emissions and analyzed according to the dimensions of the study: location, product, and pollutant. The inventory shows striking differences between the two products considered as well as between the different pollutants considered. For the T-shirt, over 70% of the energy use and CO2 emissions occur in the consuming country, whereas for the jacket, more than 70% occur in the producing country. This reversal of proportions is due to differences in the use phase of the garments. For SO2, in contrast, over two thirds of the emissions occur in the country of production for both T-shirt and jacket. The difference in emission patterns between CO2 and SO2 is due to local electricity processes, justifying our emphasis on local energy infrastructure. The complexity of considering differences in location, product, and pollutant is rewarded by a much richer understanding of a global production-consumption chain. The inclusion of two different products in the LCI highlights the importance of the definition of a product's functional unit in the analysis and implications of results. Several use-phase scenarios demonstrate the importance of consumer behavior over equipment efficiency. The spatial emission patterns of the different pollutants allow us to understand the role of various energy infrastructure elements. The emission patterns furthermore inform the debate on the Environmental Kuznets Curve, which applies only to pollutants which can be easily filtered and does not take into account the effects of production displacement. We also discuss the appropriateness and limitations of applying the LCA methodology in a global context, especially in developing countries. Our spatial LCI method yields important insights in the quantity and pattern of emissions due to different product life cycle stages, dependent on the local technology, emphasizing the importance of consumer behavior. From a life cycle perspective, consumer education promoting air-drying and cool washing is more important than efficient appliances. Spatial LCI with country-specific data is a promising method, necessary for the challenges of globalized production-consumption chains. We recommend inventory reporting of final energy forms, such as electricity, and modular LCA databases, which would allow the easy modification of underlying energy infrastructure.

Comparison of an EMG-based and a stress-based method to predict shoulder muscle forces.

The estimation of muscle forces in musculoskeletal shoulder models is still controversial. Two different methods are widely used to solve the indeterminacy of the system: electromyography (EMG)-based methods and stress-based methods. The goal of this work was to evaluate the influence of these two methods on the prediction of muscle forces, glenohumeral load and joint stability after total shoulder arthroplasty. An EMG-based and a stress-based method were implemented into the same musculoskeletal shoulder model. The model replicated the glenohumeral joint after total shoulder arthroplasty. It contained the scapula, the humerus, the joint prosthesis, the rotator cuff muscles supraspinatus, subscapularis and infraspinatus and the middle, anterior and posterior deltoid muscles. A movement of abduction was simulated in the plane of the scapula. The EMG-based method replicated muscular activity of experimentally measured EMG. The stress-based method minimised a cost function based on muscle stresses. We compared muscle forces, joint reaction force, articular contact pressure and translation of the humeral head. The stress-based method predicted a lower force of the rotator cuff muscles. This was partly counter-balanced by a higher force of the middle part of the deltoid muscle. As a consequence, the stress-based method predicted a lower joint load (16% reduced) and a higher superior-inferior translation of the humeral head (increased by 1.2 mm). The EMG-based method has the advantage of replicating the observed cocontraction of stabilising muscles of the rotator cuff. This method is, however, limited to available EMG measurements. The stress-based method has thus an advantage of flexibility, but may overestimate glenohumeral subluxation.

Prevention and management of potential adverse events during transapical aortic valve replacement.

BACKGROUND AND AIM OF THE STUDY: Transapical transcatheter aortic valve replacement (TAVR) is a new minimally invasive technique with a known risk of unexpected intra-procedural complications. Nevertheless, the clinical results are good and the limited amount of procedural adverse events confirms the usefulness of a synergistic surgical/anesthesiological management in case of unexpected emergencies. METHODS: A review was made of the authors' four-year database and other available literature to identify major and minor intra-procedural complications occurring during transapical TAVR procedures. All implants were performed under general anesthesia with a balloon-expandable Edwards Sapien stent-valve, and followed international guidelines on indications and techniques. RESULTS: Procedural success rates ranged between 94% and 100%. Life-threatening apical bleeding occurred very rarely (0-5%), and its incidence decreased after the first series of implants. Stent-valve embolization was also rare, with a global incidence ranging from 0-2%, with evidence of improvement after the learning curve. Rates of valve malpositioning ranged from 0% to < 3%, whereas the risk of coronary obstruction ranged from 0% to 3.5%. Aortic root rupture and dissection were dramatic events reported in 0-2% of transapical cases. Stent-valve malfunction was rarely reported (1-2%), whereas the valve-in-valve bailout procedure for malpositioning, malfunctioning or severe paravalvular leak was reported in about 1.0-3.5% of cases. Sudden hemodynamic management and bailout procedures such as valve-in-valve rescue or cannulation for cardiopulmonary bypass were more effective when planned during the preoperative phase. CONCLUSION: Despite attempts to avoid pitfalls, complications during transapical aortic valve procedures still occur. Preoperative strategic planning, including hemodynamic status management, alternative cannulation sites and bailout procedures, are highly recommended, particularly during the learning curve of this technique.

Screening fo osteoporosis in elderly patients admitted to post-acute rehabilitation.

Background: Screening for osteoporosis is important in older patients admitted to post-acute rehabilitation. However, DXA measurement is sometimes difficult to perform because of difficulties in positioning the patient and artefacts (osteoarthritis, prosthesis). The objectives were to determine the prevalence of unknown clinical osteoporosis in rehab patients and to determine new strategies for identifying clinical osteoporosis in this population. Method: Over a 9-months period, patients consecutively admitted to post-acute rehabilitation were included in th stdy. Patients with osteoporosis diagnosis, and those with terminal illness or severe physical limitations were excluded. Patients underwent Bone Mineral Density (BMD) by DXA and Vertebral Fracture Assessment (VFA). Clinical osteoporosis was defined as BMD ≤-2.5 SD at any site (lumbar spine, femoral neck, total hip or distal radius), ≥1 vertebral fracture, ≥1 hip fracture, or another fragility fracture and BMD ≤-2 SD. Results: Overall, 102 (17.0%) of the 600 patients admitted to rehab refused to participate in the study or were unable to consent. Among the 498 remaining patients, 99 (19.9%) were excluded because of already known diagnosis of osteoporosis, 101 (20.3%) were excluded because of terminal illness, severe physical limitations, and 45 (9.0%) because of inability to perform DXA during the stay (death, hospital transfer). Overall, 253 patients were assessed with DXA and VFA (166 women, mean age 83±7 years, mean BMI 27±6 kg/m2, and 87 men, mean age 82±6 yrs, mean BMI 27±5 kg/m2). Of these, 70% had history of fall during the last 6 months and 9.1% had hip fracture history. Prevalence of osteoporotic vertebral fracture was 36% in women and 32% in men. Overall, 152 (60.1%) patients had clinical osteoporosis (women: 67%; men: 46%) according to above criteria. Hip fracture history and vertebral fracture assessment identified correctly 105 (69.1%) of these 152 patients. Conclusion: A high prevalence of osteoporosis was observed in this population of rehab patients. Osteoporosis status should be systematically assessed in these patients at high fall risk, at least with careful history of hip fracture and an assessment for vertebral fractures with spine X-ray.

The use of external mesh reinforcement to reduce intimal hyperplasia and preserve the structure of human saphenous veins.

The saphenous vein is the conduit of choice in bypass graft procedures. Haemodynamic factors play a major role in the development of intimal hyperplasia (IH), and subsequent bypass failure. To evaluate the potential protective effect of external reinforcement on such a failure, we developed an ex vivo model for the perfusion of segments of human saphenous veins under arterial shear stress. In veins submitted to pulsatile high pressure (mean pressure at 100 mmHg) for 3 or 7 days, the use of an external macroporous polyester mesh 1) prevented the dilatation of the vessel, 2) decreased the development of IH, 3) reduced the apoptosis of smooth muscle cells, and the subsequent fibrosis of the media layer, 4) prevented the remodelling of extracellular matrix through the up-regulation of matrix metalloproteinases (MMP-2, MMP-9) and plasminogen activator type I. The data show that, in an experimental ex vivo setting, an external scaffold decreases IH and maintains the integrity of veins exposed to arterial pressure, via increase in shear stress and decrease wall tension, that likely contribute to trigger selective molecular and cellular changes.

Soft tissue artifact assessment during treadmill walking in subjects with total knee arthroplasty.

Accurate measurement of knee kinematics during functional activities suffers mainly from soft tissue artifact (STA): the combination of local surface deformations and rigid movement of markers relative to the underlying bone (also called rigid STA movement: RSTAM). This study proposes to assess RSTAM on the thigh, shank, and knee joint and to observe possible features between subjects. Nineteen subjects with knee arthroplasty were asked to walk on a treadmill while a biplane fluoroscopic system (X-rays) and a stereophotogrammetric system (skin markers) recorded their knee movement. The RSTAM was defined as the rigid movement of the cluster of skin markers relative to the prosthesis. The results showed that RSTAM amplitude represents approximately 80-100% of the STA. The vertical axis of the anatomical frame of the femur was influenced the most by RSTAM. Combined with tibial error, internal/external rotation angle and distraction-compression were the knee kinematics parameters most affected by RSTAM during the gait cycle, with average rms values of 3.8° and 11.1 mm. This study highlighted higher RSTAM during the swing phase particularly in the thigh segment and suggests new features for RSTAM such as the particular shape of some RSTAM waveforms and the absence of RSTAM in certain kinematics during the gait phases. The comparison of coefficient of multiple correlations showed some similarities of RSTAM between subjects, while some correlations were found with gait speed and BMI. These new insights could potentially allow the development of new methods of compensation to avoid STA.

In-hospital and 1-year mortality in patients undergoing early surgery for prosthetic valve endocarditis.

IMPORTANCE: There are limited prospective, controlled data evaluating survival in patients receiving early surgery vs medical therapy for prosthetic valve endocarditis (PVE). OBJECTIVE: To determine the in-hospital and 1-year mortality in patients with PVE who undergo valve replacement during index hospitalization compared with patients who receive medical therapy alone, after controlling for survival and treatment selection bias. DESIGN, SETTING, AND PARTICIPANTS: Participants were enrolled between June 2000 and December 2006 in the International Collaboration on Endocarditis-Prospective Cohort Study (ICE-PCS), a prospective, multinational, observational cohort of patients with infective endocarditis. Patients hospitalized with definite right- or left-sided PVE were included in the analysis. We evaluated the effect of treatment assignment on mortality, after adjusting for biases using a Cox proportional hazards model that included inverse probability of treatment weighting and surgery as a time-dependent covariate. The cohort was stratified by probability (propensity) for surgery, and outcomes were compared between the treatment groups within each stratum. INTERVENTIONS: Valve replacement during index hospitalization (early surgery) vs medical therapy. MAIN OUTCOMES AND MEASURES: In-hospital and 1-year mortality. RESULTS: Of the 1025 patients with PVE, 490 patients (47.8%) underwent early surgery and 535 individuals (52.2%) received medical therapy alone. Compared with medical therapy, early surgery was associated with lower in-hospital mortality in the unadjusted analysis and after controlling for treatment selection bias (in-hospital mortality: hazard ratio [HR], 0.44 [95% CI, 0.38-0.52] and lower 1-year mortality: HR, 0.57 [95% CI, 0.49-0.67]). The lower mortality associated with surgery did not persist after adjustment for survivor bias (in-hospital mortality: HR, 0.90 [95% CI, 0.76-1.07] and 1-year mortality: HR, 1.04 [95% CI, 0.89-1.23]). Subgroup analysis indicated a lower in-hospital mortality with early surgery in the highest surgical propensity quintile (21.2% vs 37.5%; P = .03). At 1-year follow-up, the reduced mortality with surgery was observed in the fourth (24.8% vs 42.9%; P = .007) and fifth (27.9% vs 50.0%; P = .007) quintiles of surgical propensity. CONCLUSIONS AND RELEVANCE: Prosthetic valve endocarditis remains associated with a high 1-year mortality rate. After adjustment for differences in clinical characteristics and survival bias, early valve replacement was not associated with lower mortality compared with medical therapy in the overall cohort. Further studies are needed to define the effect and timing of surgery in patients with PVE who have indications for surgery.

A systematic review of the surgical treatment of large incisional hernia.

PURPOSE: Incisional hernia (IH) is one of the most frequent postoperative complications. Of all patients undergoing IH repair, a vast amount have a hernia which can be defined as a large incisional hernia (LIH). The aim of this study is to identify the preferred technique for LIH repair. METHODS: A systematic review of the literature was performed and studies describing patients with IH with a diameter of 10 cm or a surface of 100 cm2 or more were included. Recurrence hazards per year were calculated for all techniques using a generalized linear model. RESULTS: Fifty-five articles were included, containing 3,945 LIH repairs. Mesh reinforced techniques displayed better recurrence rates and hazards than techniques without mesh reinforcement. Of all the mesh techniques, sublay repair, sandwich technique with sublay mesh and aponeuroplasty with intraperitoneal mesh displayed the best results (recurrence rates of <3.6%, recurrence hazard <0.5% per year). Wound complications were frequent and most often seen after complex LIH repair. CONCLUSIONS: The use of mesh during LIH repair displayed the best recurrence rates and hazards. If possible mesh in sublay position should be used in cases of LIH repair.