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Biomedical subjects

Michael Weber

Publications and source records attributed to Michael Weber.

At least 73 records · Page 4Linked to original sources
PubMed2003

Surface pretreatments for medical application of adhesion.

Medical implants and prostheses (artificial hips, tendono- and ligament plasties) usually are multi-component systems that may be machined from one of three material classes: metals, plastics and ceramics. Typically, the body-sided bonding element is bone. The purpose of this contribution is to describe developments carried out to optimize the techniques, connecting prosthesis to bone, to be joined by an adhesive bone cement at their interface. Although bonding of organic polymers to inorganic or organic surfaces and to bone has a long history, there remains a serious obstacle in realizing long-term high-bonding strengths in the in vivo body environment of ever present high humidity. Therefore, different pretreatments, individually adapted to the actual combination of materials, are needed to assure long term adhesive strength and stability against hydrolysis. This pretreatment for metal alloys may be silica layering; for PE-plastics, a specific plasma activation; and for bone, amphiphilic layering systems such that the hydrophilic properties of bone become better adapted to the hydrophobic properties of the bone cement. Amphiphilic layering systems are related to those developed in dentistry for dentine bonding. Specific pretreatment can significantly increase bond strengths, particularly after long term immersion in water under conditions similar to those in the human body. The bond strength between bone and plastic for example can be increased by a factor approaching 50 (pealing work increasing from 30 N/m to 1500 N/m). This review article summarizes the multi-disciplined subject of adhesion and adhesives, considering the technology involved in the formation and mechanical performance of adhesives joints inside the human body.

Animals↗
PubMed2003

[Increased myocardial blood flow after spinal cord stimulation in patients with refractory angina pectoris].

BACKGROUND: In spite of great progresses in surgical and catheter interventional techniques there is an increasing number of patients with coronary heart disease not suitable for these conventional treatment strategies. THERAPY: A recent review of the Study Group on the treatment of refractory angina pectoris of the European Society of Cardiology (ESC) recommends spinal cord stimulation (SCS) as first-line therapy. SCS is a well-known and often used therapy for refractory angina in other European countries but not in Germany. The present studies show that SCS is an efficient therapy. By reduction of angina symptoms and a consecutive increase of exercise capacity, the patients experience a great improvement in quality of life. In addition, recent data of our own study suggest a significant decrease in myocardial ischemia in patients under SCS. This might be a direct effect of SCS or due to a better collateralization because of the improved exercise capacity. CONCLUSION: In agreement with the study group of the ESC, we would recommend SCS as first-line therapy for refractory angina pectoris. As a matter of course, conventional treatment strategies should not be replaced by SCS. Hence, a strict evaluation before implanting a SCS device is indispensable.

Aged↗
PubMed2003

Antibiotic therapy after acute myocardial infarction: a prospective randomized study.

BACKGROUND: Infection with Chlamydia pneumoniae is suspected to contribute to the pathogenesis of human atherosclerosis. We investigated whether treatment with the macrolide antibiotic roxithromycin would reduce mortality or morbidity in patients with an acute myocardial infarction. METHODS AND RESULTS: Eight hundred seventy-two patients with an acute myocardial infarction (AMI) were randomly assigned to receive double-blind treatment with either 300 mg roxithromycin or placebo daily for 6 weeks. Primary end point was total mortality during 12-month follow-up. Four hundred thirty-three patients were treated with roxithromycin and 439 with placebo. With the exception of a higher proportion of patients suffering an anterior wall AMI (48.1% in the roxithromycin group versus 40.2% in the placebo group; P=0.027) and a lower prevalence of chronic obstructive pulmonary disease in the roxithromycin group (3.5% versus 6.9%, P=0.028), baseline characteristics, reperfusion therapy, and medical treatment were well balanced between the two groups. More patients in the roxithromycin group interrupted their study medication before completion of at least 4 weeks of treatment (78 of 433 [18%] versus 48 of 439 [11%]; P=0.003; odds ratio, 1.8; 95% CI, 1.2 to 2.6). Follow-up at 12 months was achieved in 868 of 872 (99.5%) patients. Total mortality at 12 months was 6.5% (28 of 431) in the roxithromycin group compared with 6.0% (26 of 437) in the placebo group (odds ratio, 1.1; 95% CI, 0.6 to 1.9; P=0.739). There were also no differences in the secondary combined end points at 12 months. CONCLUSIONS: Treatment of AMI patients with roxithromycin did not reduce event rates during 12 months of follow-up. Therefore, our findings do not support the routine use of antibiotic treatment with a macrolide in patients with AMI.

Aged↗
PubMed2003

VALUE trial: Long-term blood pressure trends in 13,449 patients with hypertension and high cardiovascular risk.

BACKGROUND: The Valsartan Antihypertensive Long-term Use Evaluation (VALUE) study compares cardiovascular outcomes in 15,314 eligible patients from 31 countries randomized to valsartan or amlodipine-based treatment. METHODS: The blood pressure (BP) trends are analyzed in 13,449 of VALUE study patients who had baseline BP and 24 months BP and treatment data. RESULTS: In a cohort of 12,570 patients, baseline 24 and 30 months BP, but not 30 months treatment data, were available. Of 13,449 patients, 92% (N = 12,398) received antihypertensive therapy at baseline. The baseline BP was 153.5/86.9 mm Hg in treated compared to 168.1.8/95.3 mm Hg in 1051 untreated patients. After 6 months both groups had indistinguishable BP values. At 12 months the BP decreased to 141.2/82.9 mm Hg (P <.0001 for systolic BP and diastolic BP versus baseline), at 24 months to 139.1/80 mm Hg (P <.0001 v 12 months), and to 138/79 mm Hg at 30 months (P <.0001 v 24 months). The systolic BP control (<140 mm Hg) at 30 months increased from 21.9% at baseline to 62.2%, the diastolic BP (< 90 mm Hg) from 54.2% to 90.2% and the combined control (<140 and <90 mm Hg) from 18.9% to 60.5%. At 24 months 85.8% of patients were on protocol drugs: monotherapy = 39.7%, added hydrochlorothiazide = 26.6%, add-on drugs = 15.1%, and protocol drugs in nonstandard doses = 4.3%. CONCLUSIONS: The achieved BP control exceeds values reported in most published large-scale trials. The VALUE study is executed in regular clinical settings and 92% of the patients received antihypertensive drugs at baseline. When an explicit BP goal is set, and a treatment algorithm is provided, the physicians can achieve better control rates than in their regular practice.

Algorithms↗
PubMed2003

Healing of osteochondral grafts in an ovine model under the influence of bFGF.

PURPOSE: The well-recognized limitations in cartilage healing have lead to the development of a number of resurfacing techniques for defects of joint surfaces. Autologous grafting has developed into 1 of the preferred methods of treatment for focal osteochondral lesions, although basic research on this topic remains sparse. TYPE OF STUDY: In an animal study, questions regarding the healing of osteochondral transplants under the influence of basic fibroblast growth factor (bFGF) were addressed. METHODS: Two osteochondral autologous transplantations (OAT), 1 in the weight-bearing surface of each femoral condyle, were performed on the ovine knee using a standard operative protocol. One of the grafts was bathed in phosphate buffered sulfate (PBS) containing 50 microgram of recombinant human bFGF (rh-bFGF) directly before implantation. Two groups consisting of 10 sheep each were evaluated after 3 and 6 months, respectively. RESULTS: During the evaluation of the specimens, neither osteophytes nor synovial changes were observed. Macroscopically, the superficial border of the transplanted osteochondral plug could easily be outlined at both time periods, even though the cartilage interface of the rh-bFGF specimens was less demarcated. Radiographically, a solid osteointegration of the graft could already be documented at 3 months in the control group. In contrast, integration of the chondral surface of the OAT was not seen macroscopically or microscopically at any point. A firm physical interdigitation of the reconstructed joint surface could not be demonstrated in either of the 2 groups. The augmentation with rh-bFGF stimulated the osseous ingrowth, but was not able to improve chondral healing. CONCLUSIONS: The lack of integration of the cartilaginous portion of the transplanted plugs into the reconstructed joint surface, even following augmentation with bFGF, leads to questions regarding the long-term survival of the joint itself.

Animals↗
PubMed2003

The telmisartan programme of research tO show Telmisartan End-organ proteCTION (PROTECTION) programme.

Angiotensin-II receptor blockers (ARBs) have been shown to provide stroke, cardiac and renal protection in high-risk hypertensive patients. Telmisartan is a powerful and selective ARB that provides sustained blood pressure reduction for a full 24 h after a single dose and continues to protect against circadian blood pressure surges in the critical early morning hours. The objective of the Programme of Research tO show Telmisartan End-organ proteCTION (PROTECTION) is to measure the end-organ protective effects of telmisartan in patients at high risk of renal, cardiac and vascular damage. An extensive series of clinical trials is being conducted to compare telmisartan with valsartan, losartan, amlodipine and ramipril in patients at increased risk of end-organ damage. Nine clinical studies will examine the effects of telmisartan in about 5000 hypertensive patients with isolated systolic hypertension, type 2 diabetes, obesity, left ventricular hypertrophy or renal disease. All of the studies will be conducted using state-of-the-art technology, including such techniques as ambulatory blood pressure monitoring and magnetic resonance imaging. This programme will also investigate the effects of an ARB on key surrogate markers of organ tissue damage. This series of trials will characterize the end-organ protective effects of telmisartan in hypertensive patient populations at high risk of clinical events.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2003

Detection of monitoring materials on bedside chest radiographs with the most recent generation of storage phosphor plates: dose increase does not improve detection performance.

PURPOSE: To evaluate the performance of the most recent generation of storage phosphor plates for the detection of low-contrast catheter material on bedside chest radiographs. MATERIALS AND METHODS: In 10 patients in the intensive care unit, bedside chest radiographs were obtained with a 400-speed conventional screen-film system and with storage phosphor plates with exposure levels comparable to a 200-, 400-, or 800-speed conventional system. The chest radiograph was divided into 20 regions, 60% of which were superimposed with low-contrast catheter fragments. Six observers independently assessed the presence of catheter fragments by using a receiver operating characteristic (ROC) methodology. RESULTS: Detection performance (mean area under the ROC curve [Az]) with the storage phosphor plates was significantly superior to that with the screen-film system (Az = 0.76) at all three dose levels (Az = 0.88, 0.87, and 0.83 for 200-, 400-, and 800-speed doses, respectively; P <.05). Increasing the dose to a 200-speed system did not significantly increase detection performance compared with that with the 400-speed digital radiographs (Az = 0.88 vs 0.87). Dose reduction to 800 speed significantly deteriorated the detection performance (Az = 0.83) compared with that with the 400- and 200-speed digital radiographs, respectively. CONCLUSION: The most recent generation of storage phosphor plates is superior to a 400-speed screen-film system for the detection of catheter material, even at an exposure level of 800 speed.

Adult↗
PubMed2003

Impact of ambient light and window settings on the detectability of catheters on soft-copy display of chest radiographs at bedside.

OBJECTIVE: The aim of this study was to evaluate how ambient light and interactive adjustment of density and contrast affect the detection of catheter fragments when interpreting bedside chest radiographs on soft-copy displays. MATERIALS AND METHODS: A total of 131 catheter fragments were superimposed over 10 bedside chest radiographs obtained with storage phosphor technology. Images were displayed on a clinical intensive care unit viewing station (color cathode-ray tube monitor, 21 inch [53 cm], 1280 x 1024 matrix) and were independently evaluated by five radiologists. The number of catheter fragments per image varied between 12 and 14, with an approximately equal distribution in high- and low-absorption areas. Detectability of catheter fragments was assessed under subdued and bright ambient light conditions with and without interactive adjustment of window width and level. RESULTS: Under subdued light, the detection rate of catheter fragments was significantly higher than under bright light (51.8% vs 56.6%, p < 0.05). Interactive window setting adjustment significantly increased the detection rate from 52.5% to 60.8% (p < 0.05) under subdued light and from 47.9% to 55.6% (p < 0.05) under bright light. With adjustment of window settings, the difference between the detection rates under subdued light (60.8%) and under bright light (55.6%) did not reach statistical significance. CONCLUSION: Detection of catheters on soft-copy display is significantly decreased by bright ambient light, an effect that can be largely compensated for by means of interactive adjustment of window settings.

Analysis of Variance↗
PubMed2003

Prospective evaluation of early abciximab and primary percutaneous intervention for patients with ST elevation myocardial infarction complicated by cardiogenic shock: results of the REO-SHOCK trial.

OBJECTIVE: Patients with acute myocardial infarction complicated by cardiogenic shock have a high mortality despite the use of early reperfusion therapies with thrombolysis or percutaneous coronary intervention (PCI). Therefore, there is still need to evaluate therapy strategies in these patients. DESIGN: The REO-SHOCK trial was a prospective, non-randomized study, aimed at evaluation of a routine strategy of early abciximab and PCI in a high-risk group of acute ST elevation myocardial infarction (STEMI) patients with cardiogenic shock. RESULTS: Patients (n = 40) planned for coronary angioplasty or stenting received abciximab (0.25 mg/kg bolus followed by 0.125 mg/kg/minute over 12 hours), heparin and aspirin. The intervention was successful in 92.5% of the patients and achieved Thrombolysis In Myocardial Infarction (TIMI) grade 3 patency in 32 patients (80%). The primary endpoint, total mortality after 30 days, was observed in 42.5% (17/40), and was significantly different between patients aged > 75 years and patients aged 75 years (91% versus 24%, respectively; p < 0.001). Major bleeding occurred in 2 patients (5%), but stroke occurred in none. CONCLUSION: A strategy of abciximab with primary PCI in high-risk patients with cardiogenic shock is safe, associated with a high procedural success rate and seems to improve outcomes in patients < 75 years old.

Abciximab↗
PubMed2002

Electromechanical mapping for determination of myocardial contractility and viability. A comparison with echocardiography, myocardial single-photon emission computed tomography, and positron emission tomography.

OBJECTIVE: The purpose of this study was to validate electromechanical viability parameters with combined myocardial perfusion and metabolic imaging and echocardiography. BACKGROUND: The NOGA System is a catheter-based, non-fluoroscopic, three-dimensional endocardial mapping system. This unique technique allows accurate simultaneous assessment of both local electrical activity and regional contractility. METHODS: The results of NOGA, myocardial single-photon emission computed tomography (SPECT), positron emission tomography, and echocardiography in 51 patients with coronary artery disease and a pathologic SPECT study were transcribed in a nine-segment bull's-eye projection and compared. The local shortening of normally contracting segments, as shown by echocardiography, was 9.2 +/- 5.1%, which decreased to 6.6 +/- 5.0% and 4.1 +/- 5.2% in hypokinetic and akinetic segments. The highest unipolar voltage (11.2 +/- 5.0 mV) and local shortening (8.2 +/- 5.0%) characterized normally perfused segments. Fixed perfusion defects with normal or limited 18-fluoro-2-deoxy-D-glucose uptake indicating viability had a significantly higher unipolar voltage than did scar tissue (7.25 +/- 2.7 vs. 5.0 +/- 3.1 mV, p = 0.029). CONCLUSION: Electromechanical parameters sufficiently defined the viability state of the myocardium and showed good concordance with the findings by nuclear perfusion and metabolism imaging and echocardiography. The NOGA technique provides all the relevant information immediately after coronary angiography and enables the physician to proceed with therapy in the same setting.

Aged↗
PubMed2002

MRA of the lower extremities in patients with pulmonary embolism using a blood pool contrast agent: initial experience.

PURPOSE: To evaluate the feasibility of blood pool contrast-enhanced magnetic resonance angiography (MRA) to visualize the arterial and venous vessel tree and to detect deep venous thrombosis (DVT) of the lower extremities. MATERIALS AND METHODS: Nine consecutive patients with pulmonary embolism (mean age = 46 +/- 9) were randomized to various doses of NC100150 (between 0.75 and 6 mg of Fe/kg of body weight). A T1-weighted (T1W) 3D gradient recalled echo (GRE) sequence (TE = 2.0 msec, TR = 5.0 msec) was used. Two observers blinded to the dose of contrast agent assessed image quality, contrast attenuation, and appearance of thrombi. RESULTS: Qualitative assessment of overall MRA image quality and semiquantitative vessel scoring revealed good to excellent delineation of venous and arterial vessel segments independent of the dose of NC100150. However, quantitative region of interest analysis revealed a significantly higher signal-to-noise ratio (SNR) in the high-dose group than in the mid- and low-dose groups of NC100150 (P < 0.01). Between dose groups, the SNR was independent of vessel type (artery or vein) and vessel segment localization (proximal or distal). All seven venous thrombi (mean length = 7.2 +/- 0.95 cm) were characterized by a very low signal intensity (SI), which was only 16.6 +/- 7% of the SI in adjacent venous segments (P < 0.0001). CONCLUSION: High-quality MR angiograms of the lower extremities can be obtained using low concentrations of NC100150 in combination with a strong T1W 3D GRE sequence. The obvious delineation of venous thrombi suggests that this technique may be potentially used as a noninvasive "one-stop shopping" tool in the evaluation of thromboembolic disease.

Adult↗
PubMed2002

Clinical applications of arterial stiffness: therapeutics and pharmacology.

This short review describes the effects of drugs and nonpharmacologic treatments on large artery stiffness in clinical trials. Arterial stiffness is generally accepted as a predictive factor for cardiovascular morbidity and mortality. The drug-induced reduction in arterial stiffness may parallel the reduction in cardiovascular work. This review summarizes the discussion of a task force that worked on the therapeutic aspects during a Consensus Conference on the 'Clinical applications of arterial stiffness," held in Paris on June 17, 2000. The effects of drugs on arterial stiffness are detailed in patients with hypertension, heart failure, and other arterial diseases. Other issues are raised, including the reversibility of arterial changes following pharmacologic treatment, and the possibility for nonpharmacologic treatment to be effective on arterial stiffness. Directions for future therapeutic trials are suggested.

Arteries↗
PubMed2002

Pathophysiologic and therapeutic importance of tissue ACE: a consensus report.

Angiotensin-converting enzyme (ACE) activation and the de novo production of angiotensin II contribute to cardiovascular disease through direct pathological tissue effects, including vascular remodeling and inflammation, as well as indirect action on nitric oxide bioavailability and its consequences. The endothelium plays a pivotal role in both vascular function and structure; thus, the predominant localization of ACE to the endothelium has implications for the pathobiology of vascular disease, such as coronary artery disease. Numerous experimental studies and clinical trials support the emerging realization that tissue ACE is a vital therapeutic target, and that its inhibition may restore endothelial function or prevent endothelial dysfunction. These effects exceed those attributable to blood pressure reduction alone; hence, ACE inhibitors may exert an important part of their effects through direct tissue action. Pharmacologic studies show that while ACE inhibitors may differ according to their binding affinity for tissue ACE the clinical significance remains to be determined.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2002

Tibio-calcaneo-naviculo-cuboidale arthrodesis: 6 patients followed for 1-8 years.

As a salvage procedure for patients with irreparable damage to the peritalar anatomy, we used a new method, the Ilizarov ring fixator, to stabilize a tibio-calcaneo-naviculo-cuboideal (TCNC) arthrodesis after resecting the talus in 6 patients with an average follow-up of 3 years. The tibia was lengthened by callus distraction, mean 6 (3.5-10) cm. Patients with exacerbation of a chronic talar osteomyelitis, symptomatic posttraumatic changes, and those with extremely unstable club feet and talar deformity preventing an adequate reduction of the joint, were successfully treated with the TCNC-fusion. The method permits early weight bearing, while providing stability and compression of the fusion, thereby avoiding further loss of bone stock.

Adult↗
PubMed2002

Neurovascular calcaneo-cutaneus pedicle graft for stump capping in congenital pseudarthrosis of the tibia: preliminary report of a new technique.

The operative treatment of congenital pseudarthrosis of the tibia, especially when associated with neurofibromatosis type I (Recklinghausen's disease), often leads to failure. Frequently, regardless of the type of deformity, multiple operative procedures end in the amputation of the affected limb. Soft tissue coverage of the amputation stump may confront the surgeon with new problems. Secondary perforation of the soft tissue envelope of the stump owing to terminal overgrowth is not a rare complication. A new technique of stump capping is demonstrated in a 10-year-old boy and a 14-year old girl, both with congenital pseudarthrosis of the tibia of the right leg and neurofibromatosis. During this procedure, a radical resection of the pseudarthrotic tissue is performed although all neurovascular structures supplying the calcaneus are carefully maintained (Arteria, vena et nervus tibialis posterior et peronealis). Subsequently, the tibia and fibula are inserted into the calcaneus. This construct is stabilized with two crossed Kirschner wires. Afterwards, the skin of the lower limb and the hindfoot are sutured together covering the neurovascular bundles, which are arranged in a loop-like fashion. The documented active range of motion was similar to that of the unaffected knee joint. Twelve weeks after operation in both patients, full weight bearing was achieved with a lower-leg prosthesis. This new procedure leads to a durable, full weight-bearing stump with complete sensitive innervation without the risk of future soft tissue perforation caused by the growing bone. The stump fits with an end-bearing lower-leg prosthesis.

Adolescent↗
PubMed2002

A new knee arthroplasty versus Brown procedure in congenital total absence of the tibia: a preliminary report.

The rates of successful knee arthroplasties according, for example, to Brown in patients with congenital total absence of the tibia are disappointing. A new form of knee arthroplasty is demonstrated in a 15-month-old infant with a congenital total absence of the tibia. With the help of two crossed capsular flaps and a Z-plasty of the quadriceps tendon, the patella is transposed under the femoral condyles to function as a tibial plateau. The proximal fibula is fused centrally to the external, cortical surface of the patella. A mini-ringfixator construction is used to stabilize the components, although permitting mobilization of the knee arthroplasty in the immediate postoperative period. This new type of knee arthroplasty offers distinct advantages compared with the previously published procedures.

Arthroplasty, Replacement, Knee↗
PubMed2002

Malleolus externus plasty for joint reconstruction in fibular aplasia: preliminary report of a new technique.

The instability of the upper and the lower ankle joint represents a serious problem in patients with fibular aplasia. None of the previous techniques demonstrated at least sufficient results. In this report we present a new technique of malleolus externus plasty applied in a 5 1/2-year-old boy with fibular aplasia (type II according to Coventry and Johnson or type Ib according to Achtermann and Kalamchi) with a 6 cm length deficiency of the lower leg and 1 cm of the upper leg. Furthermore, he showed a tibial antecurvation deformity of 20 degrees, a fourth ray foot with adduction deformity of the hindfoot, cutane syndactyly D 2-4, and a hallux varus. This new technique works on the following principle. A triangular iliac crest transplant is implanted with an apophysis and the annexing fascia glutealis, including the osseous part of the transplant, in the lateral distal tibia in a way that the growing apophyseal part lays distally covering the lateral talus. Gluteal fascia annexed to the apophysis was used for the reconstruction of a lateral tendon. Using a ring fixator the transplant is fixed and coincidentally the lower leg lengthened and the axis corrected. The axis deformity and the leg-length deficiency of 7 cm were equalized. The fixator could be removed after 6 months. Radiologically, an entire integration of the iliac crest transplant was found. Magnetic resonance imaging showed it had sufficient circulation. The reexamination 2.5 years later demonstrated a simultaneous growth of the malleolus externus and the distal tibia and stable ankle joints with sufficient mobility and full weight-bearing capability. For support of the foot the boy uses ready-made shoes with curved arch supports. In conclusion, using this new technique an individually adapted lateral malleolus with growth-potential can be constructed that stabilizes the foot and the ankle joints. Thus, reluxations of the foot specifically in relation to lengthening of lower legs can be avoided with concurrent preservation of the range of movement of the ankle joint.

Ankle Joint↗