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K Huber

Publications and source records attributed to K Huber.

At least 55 records · Page 3Linked to original sources
PubMed2001

[Chlamydia antibody titers in patients with coronary disease: relations to age and clinical stage].

BACKGROUND AND AIM: Atherosclerosis and its clinical sequelae are responsible for the highest death rate in industrialized countries. Seroepidemiological, pathological and immunohistochemical studies have suggested a relation between Chlamydia pneumoniae infection and the development of coronary sclerosis. Aim of this study was to investigate the frequency distribution of Chlamydia pneumoniae antibody titers in patients with different clinical stages of coronary artery disease (CAD) and patients without CAD as well as a possible age dependence of antibody titers within the study groups. For this purpose, 522 consecutive patients of a cardiology ward were investigated, over a period of 10 months, for the presence of Chlamydia pneumoniae antibodies (IgG, IgA, IgM) using specific ELISA's. In general, there was no difference in the frequency of positive Chlamydia antibody titers between CAD patients and the control group. Only in the subgroup of unstable CAD-patients < 50 years a tendency of increased antibody titers was present. Patients with stable angina, unstable angina, or acute myocardial infarction exhibited no significant differences in the rate of infection between the different age groups (p < 0.117). In contrast, there was a significant increase in positive Chlamydia pneumoniae antibodies with increasing age in the control group (p = 0.002). The relatively high incidence of positive Chlamydia pneumoniae antibody titers in young CAD patients, which is associated with a loss of age-dependent increase of the antibody titers in the CAD group, might indicate a specific role of Chlamydia pneumoniae infections for the manifestation of premature CAD (before the age of 50). Due to the increased rate of Chlamydia pneumoniae infections with increasing age, the determination of Chlamydia pneumoniae antibody titers does not allow reliable conclusions on the infectious pathogenesis of CAD. Furthermore, our unability to demonstrate differences in antibody titers between CAD patients with stable angina, unstable angina, and acute myocardial infarction suggests that acute Chlamydia pneumoniae infections are not responsible for the development of acute coronary syndromes.

Age Factors↗
PubMed2001

Plasminogen activator inhibitor type-1 in cardiovascular disease. Status report 2001.

Plasminogen activator inhibitor type-1 (PAI-1) is known to contribute to thrombus formation and to the development and the clinical course of acute and chronic cardiovascular disease, as well as of other arterial and venous thromboembolic diseases. Recently, an important role of elevated pretreatment levels of PAI-1 for failure of thrombolytic therapy of acute myocardial infarction has been discussed. PAI-1 plasma levels depend on the one hand on gene regulation but are related on the other hand to known risk factors of atherosclerosis like insulin resistance, diabetes or hypertriglyceridemia, respectively. Furthermore, an activated renin-angiotensin-aldosterone system (RAAS) significantly contributes to the upregulation of PAI-1 concentration via a receptor-mediated mechanism. In accordance to the known mechanisms of regulation of PAI-1 plasma levels, the use of specific agents like antidiabetic drugs, fibrates, statins, ACE inhibitors and angiotensin II type-1 receptor-blockers may contribute to the downregulation of circulating PAI-1 and, therefore, increase the fibrinolytic capacity and consecutively counteract the thrombotic tendency. To further improve the efficacy of thrombolytic therapy, a PAI-1 resistant variant of t-PA, TNK-t-PA, has been developed and is now available for acute myocardial infarction.

Antifibrinolytic Agents↗
PubMed2001

Homocysteine plasma levels in young patients with coronary artery disease. Relation to history of acute myocardial infarction and anatomical extent of disease.

Although there is considerable epidemiologic evidence for a relationship between plasma homocysteine (Hcy) levels and cardiovascular disease, not all prospective studies have shown such a relationship. Furthermore, data concerning the role of hyperhomocysteinemia in patients with premature coronary artery disease (CAD) are rare. It was the aim of the study to investigate a possible association between Hcy plasma levels in young patients with the extent of CAD and the history of myocardial infarction (MI). A cohort of 94 patients was examined for conventional risk factors and the history of previous transmural MI. Furthermore, coronary angiography was performed to assess the anatomical extent of vessel disease. Plasma Hcy levels were measured by use of a commercial enzyme-linked immunosorbent assay. Only a history of previous MI was significantly associated with hyperhomocysteinemia. There was no relationship between elevated Hcy levels and the anatomical extent of vessel disease in patients with premature CAD. Our data may indicate that hyperhomocysteinemia represents an independent risk factor for acute coronary thrombosis rather than for the development of coronary sclerosis. Thereby, hyperhomocysteinemia may influence the clinical situation after plaque rupture not only by prothrombotic action but also by favouring endothelial dysfunction and vasospasm.

Adult↗
PubMed2001

Apolipoprotein E epsilon 4 is associated with rapid progression of multiple sclerosis.

OBJECTIVE: The apolipoprotein E (APOE) polymorphism is known to impact on various neurologic disorders and has differential effects on the immune system and on CNS repair. Previous findings concerning a possible modulation of the clinical course of MS have been inconsistent, however. METHODS: In a cross-sectional study, the authors investigated 374 patients with clinically definite MS and a disease duration of at least 3 years and related their clinical and demographic findings to the allelic polymorphism of the APOE gene. The genotype distribution of patients with MS was compared with a cohort of 389 asymptomatic, randomly selected elderly volunteers. RESULTS: The authors found no significant differences in the distribution of genotypes between patients with MS and controls. However, patients with MS with the epsilon4 allele (n = 85) had a significantly higher progression index of disability (0.46 +/- 0.4 versus 0.33 +/- 0.26; p < 0.004) and a worse ranked MS severity score (5.1 +/- 1.9 versus 5.7 +/- 1.7; p = 0.05) than their non-epsilon4 counterparts, despite significantly more frequent long-term immunotherapy in epsilon4 carriers (74% versus 58%; p < 0.007). The annual relapse rate in epsilon4 carriers (0.87 +/- 0.56) was significantly higher than in patients with MS without an epsilon4 allele (0.71 +/- 0.47; p = 0.03). CONCLUSIONS: These results suggest no effect of the APOE genotype on susceptibility to MS, but indicate an association of the APOE epsilon4 allele with a more severe course of the disease.

Adult↗
PubMed2001

PAI-I 4G/5G polymorphism and sudden cardiac death in patients with coronary artery disease.

UNLABELLED: The 4G/5G polymorphism of the plasminogen activator inhibitor type I (PAI-I) gene is involved in coronary artery disease (CAD), with the highest risk in 4G/4G homozygotes. The role of PAI-I polymorphism in patients suffering from CAD and history of sudden cardiac death (SCD) has not been addressed yet. We studied the frequency distribution of the PAI-I gene to test the hypothesis that the 4G/4G genotype favors myocardial ischemia and, even in the absence of acute infarction, promotes SCD in patients with CAD. METHODS: The PAI-I 4G/5G genotypes and PAI-I antigen plasma levels were determined in 97 patients with CAD and a history of SCD treated with an implantable cardioverter defibrillator (ICD) (defibrillator group) comparing to 113 patients with CAD but no history of SCD (control group). RESULTS: The defibrillator group consisted of significantly more 4G/4G homozygotes and higher PAI-I levels than the control group (44% vs. 24%, 173+/-41 vs. 144+/-49 ng/ml; P<.01). The carriers of 4G allele had a significantly higher risk for SCD (odds ratio (OR) 1.9) with the highest risk in the 4G/4G genotype (OR 3.6, P<.01). CONCLUSION: These results suggest that the PAI-I 4G/4G genotype is associated with SCD in patients suffering from CAD.

Aged↗
PubMed2001

[Optimal platelet inhibition therapy in unstable angina pectoris and after coronary interventions].

ASPIRIN AND HEPARIN: In several studies aspirin has been found to be very effective in unstable angina pectoris reducing fatal and non-fatal myocardial infarction by 50-70%. Unfortunately the optimal dose of aspirin is still an open question. Whereas heparin alone shows only a weak effectiveness the combination of aspirin and heparin is superior to aspirin alone and is still the basis of antithrombotic therapy in unstable angina. TICLOPIDINE AND CLOPIDOGREL: Experience with thienopyridine derivatives in unstable angina is limited. Ticlopidine has been found to be superior to aspirin alone. Data with the combination of clopidogrel and aspirin should be available soon. THERAPEUTIC RECOMMENDATION AFTER CORONARY INTERVENTION: Both, ticlopidine and clopidogrel have been found to be very effective in preventing coronary-stent thrombosis when combined with aspirin. Meanwhile ticlopidine has been widely substituted by clopidogrel due to the better safety profile of the latter one. 75 mg clopidogrel daily combined with aspirin is recommended for at least 4 weeks after coronary stenting.

Angina, Unstable↗
PubMed2001

[Low molecular weight heparins in acute coronary syndrome].

BACKGROUND: Low molecular weight heparins (LMWH) have gained an increased role in the treatment of acute coronary syndrome within the last years. Compared to unfractionated heparins LMWH are user-friendly (high bioavailability after subcutaneous application, no needed routine control of plasma efficacy). RESULTS OF STUDIES: International trials have demonstrated a comparable (dalteparin, nadroparin) or even higher (enoxaparin) efficacy of LMWH compared to unfractionated heparin in the treatment of patients with unstable angina or non-Q-wave infarction. The use of LMWH has thereby been accompanied by a low rate of side effects. Enoxaparin appears to have the highest efficacy compared with other LMWH in the acute phase of disease, but confirming "head-to head" studies with different LMWH are lacking. A significant higher efficacy of a prolonged treatment with LMWH compared to placebo has been shown in one study (FRISC-2) in unstable patients who were not treated by coronary intervention in the early phase of disease. This lasted for about 60 days but was associated with a higher risk of bleeding. FUTURE ASPECTS: Currently, prospective clinical trials investigate the efficacy of combined use of LMWH with thrombolytics, GPIIb/IIIa blockers and the optimal dosage of LMWH during coronary interventions.

Acute Disease↗
PubMed2001

Soluble selectins in the pulmonary and systemic circulation in acute cardiogenic and non-cardiogenic pulmonary failure.

OBJECTIVE: Pulmonary endothelial activation caused by high pulmonary capillary pressures may be involved in the pathogenesis of cardiogenic pulmonary edema (CPE). We studied soluble selectins and soluble ICAM-1 as markers of cell activation in the systemic and pulmonary circulation of patients with respiratory failure (RF) due to CPE (RFCPE) as compared to patients with RF due to pulmonary infection (RFPI). SETTING: Cardiovascular Intensive Care Unit at a university hospital. PATIENTS: Twenty patients with RFCPE, 20 patients with RFPI and 17 critically ill patients without RF. INTERVENTIONS: Blood samples were obtained from the arterial and the pulmonary capillary circulation and sE-, sL-, and sP-selectin as well as sICAM-1 were determined. To distinguish between systemic and pulmonary endothelial activation, transpulmonary gradients (concentrationarterial blood - concentrationpulmonary capillary blood) were calculated. RESULTS: Systemic concentration of sL-selectin was lower in patients with RFCPE and RFPI than in patients without RF (RFCPE: 719.0 +/- 243.9 ng/ml, RFPI: 528.5 +/- 220.8 ng/ml, no RF: 882.4 +/- 222.6 ng/ml; P < 0.001). Systemic concentrations of ICAM-1, sE- and sP-selectin were not significantly different between the three groups. Transpulmonary gradients in sE- and sL-selectin were predominantly negative in patients with RFCPE (-3.2 +/- 7.8 ng/ml and -55.4 +/- 116.1 ng/ml, respectively) and RFPI (-2.3 +/- 5.8 ng/ml and -17.6 +/- 40.3 ng/ml, respectively) but were predominantly positive in patients without RF (11.6 +/- 7.2 ng/ml and 66.6 +/- 69.6 ng/ml, respectively), which suggests trapping of sE- and sL-selectin in the pulmonary circulation in the majority of patients with RFPI as well as in the majority of patients with RFCPE. CONCLUSION: Pulmonary endothelial activation occurs during both RFCPE and RFPI. This adds evidence that, besides hydrostatic mechanisms, cell activation occurs during CPE.

Acute Disease↗
PubMed2001

Neurochemically distinct myenteric neurone populations containing calbindin have specific distribution patterns around the circumference of the gastric corpus.

We recently described calbindin immunoreactivity in the myenteric plexus of the guinea-pig stomach. To study the neurochemical coding of calbindin D28 k (CALB)-containing myenteric neurones, the presence of calretinin (CALRET), choline acetyltransferase (ChAT), enkephalin (ENK), neuropeptide Y, serotonin (5-HT), somatostatin (SOM) and substance P(SP) was investigated immunohistochemically in colchicine-treated preparations. Nitric oxide synthase-containing neurones were detected by NADPH-diaphorase histochemistry. In addition, we investigated the neurone distribution patterns around the gastric corpus. Most CALB neurones were ChAT positive. ChAT/CALB neurones were either CALRET (ca 75%) or 5-HT positive and most contained in addition SP and/or ENK. All 5-HT neurones contained CALB. CALB labelled on average 2.3, 4.8 and 7.5 neurones per ganglion at the lesser curvature, in the central region and the greater curvature, respectively, which indicated a preferential localisation at the greater curvature. Compared to the total number of myenteric neurones, the proportion of CALB neurones increased significantly from the lesser curvature (6%) towards the greater curvature (18%). This shift, although observed for most ChAT/CALB-positive populations, was most prominent for the ChAT/CALB/CALRET/SP/ENK-encoded neurones. SOM-positive and ChAT-only encoded neurones were preferentially located at the lesser curvature. The remaining ten neurochemically defined populations did not exhibit an uneven distribution. The colocalisation of CALB with CALRET or 5-HT is specific for myenteric neurones in the stomach and represents one significant difference to the neurochemical code of CALB neurones in the guinea-pig intestine. The functional significance of the unevenness of neurone distribution along the circumference of the gastric corpus remains to be studied.

Animals↗
PubMed2001

Plasminogen activator inhibitor type-1 (part two): role for failure of thrombolytic therapy. PAI-1 resistance as a potential benefit for new fibrinolytic agents.

Rapid and sustained reperfusion of an occluded coronary artery is the goal of thrombolytic therapy in acute myocardial infarction. However, the clot-dissolving efficacy of fibrinolytic agents such as tissue-type plasminogen activator (t-PA) is limited, in vivo, in part by the action of plasminogen activator inhibitor type-1 (PAI-1). A new generation of fibrinolytic agents has been genetically engineered to have greater resistance to PAI-1 inhibition. This article reviews the pathophysiologic role of PAI-1 in failure of thrombolytic therapy and describes the advantages that PAI-1-resistance may confer upon fibrinolytic agents such as TNK-t-PA, the new fibrinolytic agent with the most powerful PAI-1 resistance.

Animals↗
PubMed2001

Plasminogen activator inhibitor type-1 (part one): basic mechanisms, regulation, and role for thromboembolic disease.

Plasminogen activator inhibitor type-1 (PAI-1) is a rapid inhibitor of tissue plasminogen activator (tPA) in circulation. Evidence suggests that the PAI-1 concentration is responsible for the regulation of the endogenous fibrinolytic system through its tPA/PAI-1 interactions. Accordingly, increased levels of PAI-1 have emerged as a masker for an increased thrombolic risk. This article represents a status report of mechanism of action, regulation of plasma levels, as well as the role of PAI-1 in arterial and venous thromboembolic disease.

Animals↗
PubMed2001

In-vitro assessment of a registration protocol for image guided implant dentistry.

In this study a computer aided navigation technique for accurate positioning of oral implants was assessed. An optical tracking system with specially designed tools for monitoring the position of surgical instruments relative to the patient was used to register 5 partially or completely edentulous jaw models. Besides the accuracy of the tracking system, the precision of localizing a specific position on 3-dimensional preoperative imagery is governed by the registration algorithm which conveys the coordinate system of the preoperative computed tomography (CT) scan to the actual patient position. Two different point-to-point registration algorithms were compared for their suitability for this application. The accuracy was determined separately for the localization error of the position measurement hardware (fiducial localization error-FLE) and the error as reported by the registration algorithm (fiducial registration error-FRE). The overall error of the navigation procedure was determined as the localization error of additional landmarks (steel spheres, 0.5 mm diameter) after registration (target registration error-TRE). Images of the jaw models were obtained using a high resolution CT scan (1.5 mm slice thickness, 1 mm table feed, incremental scanning, 120 kV, 150 mAs, 512 x 512 matrix, FOV 120 mm). The accuracy of the position measurement probes was 0.69 +/- 0.15 mm (FLE). Using 3 implanted fiducial markers, FRE was 0.71 +/- 0.12 mm on average and 1.00 +/- 0.13 mm maximum. TRE was found to be 1.23 +/- 0.28 mm average and 1.87 +/- 0.47 mm maximum. Increasing the number of fiducial markers to a total of 5 did not significantly improve precision. Furthermore it was found that a registration algorithm based on solving an eigenvalue problem is the superior approach for point-to-point matching in terms of mathematical stability. The experimental results indicate that positioning accuracy of oral implants may benefit from computer aided intraoperative navigation. The accuracy achieved compares well to the resolution of the CT scan used. Further development of point-to-point/point-to-surface registration methods and tracking hardware has the potential to improve the precision of the method even further. Our system has potential to reduce the intraoperative risk of causing damage to critical anatomic structures, to minimize the efforts in prosthetic modelling, and to simplify the task of transferring preoperative planning data precisely to the operating room in general.

Algorithms↗
PubMed2001

Homozygosity for the C-->T polymorphism at nucleotide 46 in the 5' untranslated region of the factor XII gene protects from development of acute coronary syndrome.

Recently, a C-->T polymorphism at nucleotide 46 in the 5'-untranslated region of the factor XII (FXII) gene was shown to be associated with lower levels of FXII. To study the impact of this polymorphism on the development of an acute coronary syndrome (ACS), we compared 303 patients with ACS and 227 patients with stable coronary artery disease (CAD). In the latter group, 54.2% of individuals carried wild-type FXII:46C, 37.9% were heterozygous FXII:C46T and 7.9% were homozygous for FXII:46T. In contrast, in the ACS group (n = 303), 54.1% were wild-type FXII:46C, 42.6% were heterozygous FXII:C46T and only 3.3% carried the homozygous FXII:46T genotype. The 2.5-fold lower prevalence of the FXII:46T genotype in patients with ACS could indicate a protective effect on the development of ACS (odds ratio = 0.4, 95% CI 0.1-0.9) in patients with pre-existing CAD.

5' Untranslated Regions↗
PubMed2001

No effect of vitamin D3 treatment on active calcium absorption across ruminal epithelium of sheep.

A significant contribution of the forestomachs in net calcium (Ca2+) absorption from the gastrointestinal tract has been postulated from in vivo and in vitro studies in different ruminant species. However, the potential role of vitamin D3 and its metabolites in controlling these mechanisms is still under discussion. It was therefore the aim of the present study to investigate the effectiveness of treatment with vitamin D3 in stimulating active Ca2+ absorption from sheep rumen. Four mature, non-lactating, non-pregnant sheep that had been treated 7 and 4 days before the Ca2+ flux rate measurements with intramuscular injections of 300000 IU of vitamin D3 each in aqueous solution were used. Two female and three male placebo-treated sheep served as controls. To characterize the effects of vitamin D3 application on plasma parameters the time courses of total calcium, inorganic phosphate, calcitriol and intact parathyroid hormone (iPTH) were recorded. In vitro studies of unidirectional Ca2+ flux rates across isolated, intact rumen wall epithelia were carried out by applying the Ussing-chamber technique. Western blot analysis and reverse transcriptase-polymerase chain reaction analysis (RT-PCR) were applied to identify vitamin D receptors (VDR) in ruminal and jejunal tissues. In addition, Western blot analysis for qualitative examination of epithelial calbindin D9k levels was carried out in these tissues. Total calcium and phosphate levels in plasma were not significantly affected treatment with vitamin whereas calcitriol concentrations significantly increased by about 130 and 63% after the first and second application, respectively. In contrast, iPTH tended to decrease by about 60% indicating regulatory effects of calcitriol on systemic Ca homeostasis. The Ca2+ flux rate measurements in Ussing-chambers revealed significant net Ca2+ absorption indicating the contribution of active mechanisms for Ca2+ transport in rumen epithelia. This, however, was not significantly affected by increased calcitriol concentrations in plasma. Western blot analysis on the basis of a human recombinant VDR protein and RT-PCR clearly indicated the presence of VDR in ruminal and jejunal epithelia, but, in contrast to jejunum, this was not reflected by respective amounts of calbindin-D9k in ruminal tissues. The results suggest the absence of classical calbindin-D9k-mediated mechanisms for active Ca2+ transport in sheep rumen.

Absorption↗
PubMed2001

Plasminogen activator inhibitor type 1 and outcome after successful cardiopulmonary resuscitation.

OBJECTIVE: Patients after successful cardiopulmonary resuscitation have been shown to exhibit elevated plasma concentrations of plasminogen activator inhibitor (PAI) type 1, the main circulating antifibrinolytic protein. It has been suggested that elevations in PAI-1 contribute to cerebral no-reflow after successful cardiopulmonary resuscitation. We analyzed whether PAI-1 concentrations might predict cerebral outcome after cardiopulmonary resuscitation. DESIGN: Prospective, controlled study. SETTING: Intensive care unit at a university hospital. PATIENTS: Thirty-five patients after successful cardiopulmonary resuscitation and 35 control patients who were not critically ill. INTERVENTIONS: Blood sampling for determination of plasma concentrations of active and total PAI-1 antigen. MEASUREMENTS AND MAIN RESULTS: Plasma concentrations of total and active PAI-1 antigen on the second day after successful cardiopulmonary resuscitation were significantly higher in patients after cardiopulmonary resuscitation than in controls (p <.0001) and were unrelated to duration of cardiopulmonary resuscitation. Both active and total PAI-1 antigen were higher in patients who developed acute renal failure after cardiopulmonary resuscitation. Patients with an unfavorable cerebral outcome after cardiopulmonary resuscitation had higher total PAI-1 antigen concentrations compared with patients with good outcome after cardiopulmonary resuscitation (p =.026). We identified 180 ng/mL as the best cutoff value for total PAI-1 antigen with respect to cerebral outcome (chi-square 11.8, p =.001). In a logistic regression analysis, only systemic inflammatory response syndrome (p =.028), acute renal failure after cardiopulmonary resuscitation (p =.017), and cardiopulmonary resuscitation duration >15 mins (p =.042) were significantly and independently associated with cerebral outcome after cardiopulmonary resuscitation. Total PAI-1 antigen reached only borderline significance (p =.058) but nevertheless slightly improved the correct prediction of cerebral outcome after cardiopulmonary resuscitation. CONCLUSIONS: Acute renal failure after cardiopulmonary resuscitation, systemic inflammatory response syndrome, and cardiopulmonary resuscitation duration are better predictors of cerebral outcome after cardiopulmonary resuscitation than PAI-1 antigen, but determination of total PAI-1 antigen nevertheless might improve the early prediction of cerebral outcome after cardiopulmonary resuscitation. Whether elevated PAI-1 concentrations, possibly via prothrombogenic/antifibrinolytic effects, contribute causally to cerebral no-reflow and acute renal failure after cardiopulmonary resuscitation remains to be clarified.

Acute Kidney Injury↗
PubMed2001

Tonsillectomy with argon plasma coagulation (APC): evaluation of pain and hemorrhage.

OBJECTIVE: Argon plasma coagulation (APC) offers a new possibility for tonsillectomy (TE) because of its effective hemostasis and limited penetration depth of the coagulation zone. The APC dissector allows dissection and hemostasis in a one-step procedure. The aim of this prospective, randomized, single-blinded study was the evaluation of pain and hemorrhage of the "hot" argon-plasma-coagulation tonsillectomy (TE(APC)) compared with a conventional "cold" non-electrosurgery tonsillectomy (TE(Conv)). METHODS: Two hundred one consecutive patients undergoing tonsillectomy were included in a single-blinded, randomized, prospective study with stratification in two age groups. RESULTS: There was no statistical significant difference between TE(APC) and TE(Conv) in the intensity of postoperative pain and primary or secondary hemorrhage in both age groups. In the TE(APC) group, the mean duration of tonsillectomy was significantly reduced by more than 50% in both age groups (P <.01). The blood loss was 90% decreased in the TE(APC) compared with the TE(Conv) in both age groups (P <.01). CONCLUSIONS: The APC technique does not face the general problem of electrosurgery or thermal coagulation techniques in which the postoperative pain is often increased compared with conventional cold techniques. It offers an innovative new tonsillectomy method with significant reduced blood loss and surgical time.

Child↗
PubMed2001

Placement of endosteal implants in the zygoma after maxillectomy: a Cadaver study using surgical navigation.

Endosteal implants facilitate obturator prosthesis fixation in tumor patients after maxillectomy. Previous clinical studies have shown, however, that the survival of implants placed into available bone after maxillectomy is generally poor. Nevertheless, implants positioned optimally in residual zygomatic bone provide superior stability from a biomechanical point of view. In a pilot study, the authors assessed the precision of VISIT, a computer-aided surgical navigation system dedicated to the placement of endosteal implants in the maxillofacial area. Five cadaver specimens underwent hemimaxillectomy. The cadaver head was matched to a preoperative high-resolution computed tomograph by using implanted surgical microscrews as fiducial markers. The position of a surgical drill relative to the cadaver head was determined with an optical tracking system. Implants were placed into the zygomatic arch, where maximum bone volume was available. The results were assessed using tests for localization accuracy and postoperative computed tomographic scans of the cadaver specimens. The localization accuracy of landmarks on the bony skull was 0.6 +/- 0.3 mm (average +/- SD), as determined with a 5-df pointer probe; the localization accuracy of the tip of the implant burr was 1.7 +/- 0.4 mm. The accuracy of the implant position compared with the planned position was 1.3 +/- 0.8 mm for the external perforation of the zygoma and 1.7 +/-1.3 mm for the internal perforation. Eight of 10 implants were inserted with maximal contact to surrounding bone, and two implants were located unfavorably. Reliable placement of implants in this region is difficult to achieve. The technique described in this article may be very helpful in the management of patients after maxillary resection with poor support for obturator prostheses.

Cadaver↗