Development and early testing of a simple subcutaneous counterpulsation device.
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The intra-aortic balloon pump has been widely and successfully used as a treatment for cardiac dysfunction, but it only has short-term applications. To overcome this limitation, a superficial counterpulsation device (CPD) is being developed to provide extended counterpulsation support to promote myocardial recovery. The CPD is a valveless, monoport, pneumatically driven, 40-ml sac that is intended to be implanted in a pacemaker-type pocket in the subclavian fossa. The sac is designed to fill in systole and empty during diastole through an outflow graft anastomosed to the subclavian artery. A feasibility study was conducted to investigate acute hemodynamic responses to the CPD in eight calves with diminished cardiac function. The CPD augmented aortic diastolic pressure, reduced left ventricular peak systolic and aortic ejection pressures by up to 18%, and increased diastolic coronary flow by up to 21% and stroke volume by up to 12%. A cadaver fit study demonstrated that the human subclavian artery is a reasonable anastomosis site to consider and that the 40-ml CPD needs to be reduced in size to provide a better anatomical fit. The clinical attractiveness of this approach is that it may provide extended support through a subcutaneous surgical procedure. (+info)
Prosthetic management of a patient with Treacher Collins syndrome.
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Treacher Collins syndrome encompasses a group of closely related defects of the head and neck. It is a rare syndrome characterized by bilaterally symmetrical abnormalities derived from the first and second brachial arches and the nasal placode. It is an autosomal dominant disorder and its occurence ranges from 1 in 25,000 to 1 in 50,000 live births. The facial appearance of these patients can be improved by either surgical or prosthetic rehabilitation. In this case report we are presenting the features of a 13-year-old boy with Treacher Collins syndrome. A multidisplinary approach was followed in managing the situation. The various treatment options and the steps involved in making an auricular prosthesis are also discussed. (+info)
Prediction of valve prosthesis-patient mismatch prior to aortic valve replacement: which is the best method?
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BACKGROUND: To predict the occurrence of valve prosthesis-patient mismatch (VP-PM) after aortic valve replacement (AVR), the surgeon needs to estimate the postoperative effective orifice area index (EOAI). AIM: To compare different methods of predicting VP-PM. METHODS: The effective orifice area (EOA) of 383 patients who had undergone AVR between July 2000 and January 2005 with various aortic valve prostheses was obtained echocardiographically 6 months after the operation. We tested the efficacy of (1) EOAI calculated from the echo data obtained in our own laboratory, (2) indexed geometric orifice area, (3) EOAI estimated from charts provided by prosthesis manufacturers (which are based either on in vitro or on echo data) and (4) EOAI estimated from reference echo data published in the literature to predict VP-PM. RESULTS: Sensitivity and specificity to predict VP-PM were 53% and 83% (method 1), 80% and 53% (charts based on echo data, parts of method 3) and 71% and 67% (method 4) using reference data derived from echocardiographic examinations. The sensitivity of method 2 and of charts based on in vitro data (parts of method 3) to predict VP-PM was 0-17%. The incidence of severe VP-PM could be reduced from 8.7% to 0.8% after the introduction of the systematic estimation of the EOAI at the time of operation (p = 0.003, method 1). CONCLUSIONS: The best method of predicting VP-PM is the use of mean (SD) EOAs derived from echocardiographic examinations, whereas the use of in vitro data or the geometric orifice area is unreliable. After the surgeon's anticipation of VP-PM prior to AVR, the incidence of VP-PM could be reduced. (+info)
Synchronisation of tibial rotational alignment with femoral component in total knee arthroplasty.
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The rotational axis of the tibial component in total knee arthroplasty described by Insall is generally accepted, but rotational mismatch between the femoral and the tibial components can occur because the alignment of each component is determined separately. We developed a connecting instrument to synchronise the axis of the tibia to the axis of the femur. We compared the rotational axis of the tibial component using our method and medial one third of tibial tuberosity (Insall's reference) in 70 consecutive TKAs. The rotational axis of the tibial component from the femoro-tibial synchronisation was rotated internally 13.8 degrees +/- 5.8 degrees (range, 2 degrees - 24 degrees ) more than the axis of Insall's reference. Eighty three percent of patellae tracked centrally and the patellae tilt measured 2.2 degrees on average. More attention should be given to the rotational congruency between the femoro-tibial components, because the recent prosthetic design has more conforming articular surfaces. (+info)
Branched grafting for aortoiliac aneurysms.
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PURPOSE: To evaluate a novel approach to preserve pelvic perfusion during endovascular AAA repair in patients with common iliac aneurysms extending to the iliac bifurcation. MATERIALS AND METHODS: A multicenter prospective analysis of patients undergoing implantation of a branched endograft designed to perfuse the internal iliac artery was conducted. All patients enrolled were considered high risk for open surgical repair and presented with common iliac artery aneurysms greater than 20mm and anatomy amenable to implant the branched device. Preoperative high resolution spiral CT, and follow-up CT studies in addition to abdominal radiographs were obtained at discharge, 1, 6, 12, and 24 months. RESULTS: Between 2003 and 2006, 52 patients (53 internal iliacs) were implanted with an investigational device. Mean common iliac aneurysm maximal diameter was 38 mm. The branch graft was combined with a proximal standard bifurcated component (61%), a fenestrated or a visceral branch component (33%), an aortouni-iliac component (2%), and alone in 2 patients (4%, following prior aortobi-iliac repair). Technical success was achieved in 94% of patients. Within the first month, 6 (11%) internal iliac branches occluded. No occlusions were noted after 1 month. The mean follow-up was 14.2 months. Common iliac aneurysm shrinkage was noted in 42% and 81% of patients at 6 and 12 months. There were no rupture, aneurysm related deaths or conversions, but there were 7 deaths during follow-up. CONCLUSIONS: The placement of endovascular prostheses that maintain antegrade perfusion of one or both internal iliac arteries is feasible, and early results provide evidence for optimism with regard to safety and efficacy. (+info)
Poor accuracy of freehand cup positioning during total hip arthroplasty.
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Several studies have demonstrated a correlation between the acetabular cup position and the risk of dislocation, wear and range of motion after total hip arthroplasty. The present study was designed to evaluate the accuracy of the surgeon's estimated position of the cup after freehand placement in total hip replacement. Peroperative estimated abduction and anteversion of 200 acetabular components (placed by three orthopaedic surgeons and nine residents) were compared with measured outcomes (according to Pradhan) on postoperative radiographs. Cups were placed in 49.7 degrees (SD 6.7) of abduction and 16.0 degrees (SD 8.1) of anteversion. Estimation of placement was 46.3 degrees (SD 4.3) of abduction and 14.6 degrees (SD 5.9) of anteversion. Of more interest is the fact that for the orthopaedic surgeons the mean inaccuracy of estimation was 4.1 degrees (SD 3.9) for abduction and 5.2 degrees (SD 4.5) for anteversion and for their residents this was respectively, 6.3 degrees (SD 4.6) and 5.7 degrees (SD 5.0). Significant differences were found between orthopaedic surgeons and residents for inaccuracy of estimation for abduction, not for anteversion. Body mass index, sex, (un)cemented fixation and surgical approach (anterolateral or posterolateral) were not significant factors. Based upon the inaccuracy of estimation, the group's chance on future cup placement within Lewinnek's safe zone (5-25 degrees anteversion and 30-50 degrees abduction) is 82.7 and 85.2% for anteversion and abduction separately. When both parameters are combined, the chance of accurate placement is only 70.5%. The chance of placement of the acetabular component within 5 degrees of an intended position, for both abduction and anteversion is 21.5% this percentage decreases to just 2.9% when the tolerated error is 1 degrees . There is a tendency to underestimate both abduction and anteversion. Orthopaedic surgeons are superior to their residents in estimating abduction of the acetabular component. The results of this study indicate that freehand placement of the acetabular component is not a reliable method. (+info)
Impact of patient-prosthesis mismatch and aortic valve design on coronary flow reserve after aortic valve replacement.
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OBJECTIVES: This prospective-randomized study investigated the effect of aortic valve design and patient-prosthesis mismatch (PPM) on coronary flow reserve (CFR) after mechanical or biological aortic valve replacement (AVR) in patients with aortic stenosis (AS). BACKGROUND: Coronary flow reserve may be an important parameter of long-term survival after AVR in patients with AS. Reduced CFR may contribute to more cardiovascular events and greater rates of mortality. METHODS: A total of 48 patients undergoing AVR underwent magnetic resonance imaging for the measurement of coronary flow preoperatively, 5 days postoperatively, and at 6-month follow-up with measurement of CFR. Patients scheduled for mechanical AVR were randomized to a tilting disc or bileaflet prosthesis (n = 12 in each group). For biological AVR, patients were scheduled to receive a stented (n = 12) or stentless (n = 12) valve. Patients also underwent echocardiography with measurement of transvalvular pressure gradients and left ventricular mass regression. RESULTS: Postoperatively, coronary flow increased significantly in all groups (p < 0.001). Only stentless valves demonstrated a normal CFR (3.4 +/- 0.3 vs. 2.3 +/- 0.1 for stented biological valves, 2.1 +/- 0.2 for tilting disc, and 2.2 +/- 0.3 for bileaflet mechanical valves). Patient-prosthesis mismatch with an indexed effective orifice area <0.85 cm2/m2 led to decreased rates of CFR in the tilting disc, stentless, and stented groups. Pressure gradients were 14 +/- 3 mm Hg for tilting disc, 12 +/- 4 mm Hg for bileaflet, 19 +/- 6 mm Hg for stented, and 10 +/- 4 mm Hg for stentless valves. CONCLUSIONS: Normalization of CFR after AVR in patients with AS was observed only for stentless valves. Coronary flow reserve might explain the excellent long-term results for stentless valves. (Impact of Patient-Prosthesis Mismatch on Coronary Flow Reserve; http://www.clinicaltrials.gov/ct/show/NCT00310947?order=1; NCT00310947). (+info)
Hip resurfacing: why does it fail? Early results and critical analysis of our first 60 cases.
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Resurfacing replacement represents the most conservative solution available for total arthroplasty of the hip. However, despite the excellent results reported by highly experienced surgeons, a small but not insignificant body of literature has been published on the more controversial aspects of this approach, mainly those related to the biological and mechanical vulnerability of the retained epiphysis. We report here our evaluation of most of the variables inherent to this procedure (surgical exposure, implant design, technical steps). Based on our results, we conclude that the short-term outcome is strongly related to the surgical approach and the relationship between implant design and cementing technique. Even if posterior approaches are currently widely accepted for resurfacing replacement, the ability to preserve the medial circumflex artery has been questioned, and an alternative exposure has been proposed with good results (antero-lateral, lateral and digastric trochanteric osteotomy). Moreover, a minimally invasive posterior approach could increase the risks of vascular damage. Alternatively, inner implant geometry could affect the distribution of cement over the epiphysis when other variables (direct or indirect cementing technique, viscosity) are not properly selected. (+info)