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  • 1. Affatato, S.
    et al.
    Leardini, W.
    Jedenmalm, Anneli
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ruggeri, O.
    Toni, A.
    Larger diameter bearings reduce wear in metal-on-metal hip implants2007In: Clinical Orthopaedics and Related Research, ISSN 0009-921X, E-ISSN 1528-1132, no 456, p. 153-158Article in journal (Refereed)
    Abstract [en]

    Metal-on-metal hip arthroplasty has the longest clinical history of all total arthroplasties. We asked whether large diameter femoral heads would result in less wear than those with small diameters. We also asked if there is a threshold diameter that ensures good wear behavior. We tested three batches of cast high-carbon cobalt-chromium-molybdenum hip implants (28 mm, 36 min, and 54 min diameters) in a hip simulator for 5 million cycles. We used bovine serum as lubricant and weighed the samples at regular intervals during testing. The 28-mm configuration had almost twice the wear of the 54-mm configuration, but we observed no difference between the 36-mm and the 54-mm configurations. The similarity in the wear performances of the larger configurations supports the presence of a threshold diameter that ensures good wear behavior.

  • 2. Dolan, R. T.
    et al.
    Penny, S.
    Kelly, C. M.
    Brennan, D. J.
    Rexhepaj, E.
    Jirstrom, K.
    Ponten, F.
    Uhlén, Mathias
    KTH, School of Biotechnology (BIO), Proteomics.
    Gallagher, W. M.
    Kell, M. R.
    Development of immunohistochemical surrogates for prediction of breast cancer patient outcome via high-throughput antibody generation and validation using tissue microarray technology2011In: British Journal of Surgery, ISSN 0007-1323, E-ISSN 1365-2168, Vol. 98, p. 28-28Article in journal (Refereed)
  • 3. Erhart, P.
    et al.
    Hyhlik-Dürr, A.
    Geisbüsch, P.
    Kotelis, D.
    Müller-Eschner, M.
    Gasser, Thomas Christian
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    von Tengg-Kobligk, H.
    Böckler, D.
    Finite Element Analysis in Asymptomatic, Symptomatic, and Ruptured Abdominal Aortic Aneurysms: In Search of New Rupture Risk Predictors2015In: European Journal of Vascular and Endovascular Surgery, ISSN 1078-5884, E-ISSN 1532-2165, Vol. 49, no 3, p. 239-245Article in journal (Refereed)
    Abstract [en]

    Objectives: To compare biomechanical rupture risk parameters of asymptomatic, symptomatic and ruptured abdominal aortic aneurysms (AAA) using finite element analysis (FEA). Study design: Retrospective biomechanical single center analysis of asymptomatic, symptomatic, and ruptured AAAs. Comparison of biomechanical parameters from FEA. Materials and methods: From 2011 to 2013 computed tomography angiography (CTA) data from 30 asymptomatic, 15 symptomatic, and 15 ruptured AAAs were collected consecutively. FEA was performed according to the successive steps of AAA vessel reconstruction, segmentation and finite element computation. Biomechanical parameters Peak Wall Rupture Risk Index (PWRI), Peak Wall Stress (PWS), and Rupture Risk Equivalent Diameter (RRED) were compared among the three subgroups. Results: PWRI differentiated between asymptomatic and symptomatic AAAs (p < .0004) better than PWS (p < .1453). PWRI-dependent RRED was higher in the symptomatic subgroup compared with the asymptomatic subgroup (p < .0004). Maximum AAA external diameters were comparable between the two groups (p < .1355). Ruptured AAAs showed the highest values for external diameter, total intraluminal thrombus volume, PWS, RRED, and PWRI compared with asymptomatic and symptomatic AAAs. In contrast with symptomatic and ruptured AAAs, none of the asymptomatic patients had a PWRI value >1.0. This threshold value might identify patients at imminent risk of rupture: Conclusions: From different FEA derived parameter, PWRI distinguishes most precisely between asymptomatic and symptomatic AAAs. If elevated, this value may represent a negative prognostic factor for asymptomatic AAAs.

  • 4.
    Forsell, Caroline
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    Björck, Hanna M.
    Eriksson, Per
    Franco-Cereceda, Anders
    Gasser, T. Christian
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    Biomechanical Properties of the Thoracic Aneurysmal Wall: Differences Between Bicuspid Aortic Valve and Tricuspid Aortic Valve Patients2014In: Annals of Thoracic Surgery, ISSN 0003-4975, E-ISSN 1552-6259, Vol. 98, no 1, p. 65-71Article in journal (Refereed)
    Abstract [en]

    Background. The prevalence for thoracic aortic aneurysms (TAAs) is significantly increased in patients with a bicuspid aortic valve (BAV) compared with patients who have a normal tricuspid aortic valve (TAV). TAA rupture is a life-threatening event, and biomechanics-based simulations of the aorta may help to disentangle the molecular mechanism behind its development and progression. The present study used polarized microscopy and macroscopic in vitro tensile testing to explore collagen organization and mechanical properties of TAA wall specimens from BAV and TAV patients. Methods. Circumferential sections of aneurysmal aortic tissue from BAV and TAV patients were obtained during elective operations. The distribution of collagen orientation was captured by a Bingham distribution, and finite element models were used to estimate constitutive model parameters from experimental load-displacement curves. Results. Collagen orientation was almost identical in BAV and TAV patients, with a highest probability of alignment along the circumferential direction. The strength was almost two times higher in BAV samples (0.834 MPa) than in TAV samples (0.443 MPa; p < 0.001). The collagen-related stiffness (C-f) was significantly increased in BAV compared with TAV patients (C-f = 7.45 MPa vs 3.40 MPa; p = 0.003), whereas the elastin-related stiffness was similar in both groups. A trend toward a decreased wall thickness was seen in BAV patients (p = 0.058). Conclusions. The aneurysmal aortas of BAV patients show a higher macroscopic strength, mainly due to an increased collagen-related stiffness, compared with TAV patients. The increased wall stiffness in BAV patients may contribute to the higher prevalence for TAAs in this group.

  • 5.
    Höybye, Charlotte
    et al.
    Departments of Endocrinology and Diabetology, Otorhinolaryngology and Head and Neck Surgery, and Neurosurgery, Karolinska Hospital, Stockholm.
    Grenbäck, Eva
    Departments of Endocrinology and Diabetology, Otorhinolaryngology and Head and Neck Surgery, and Neurosurgery, Karolinska Hospital, Stockholm.
    Thorén, Marja
    Departments of Endocrinology and Diabetology, Otorhinolaryngology and Head and Neck Surgery, and Neurosurgery, Karolinska Hospital, Stockholm.
    Hulting, Anna-Lena
    Departments of Endocrinology and Diabetology, Otorhinolaryngology and Head and Neck Surgery, and Neurosurgery, Karolinska Hospital, Stockholm.
    Lundblad, Lars
    Departments of Endocrinology and Diabetology, Otorhinolaryngology and Head and Neck Surgery, and Neurosurgery, Karolinska Hospital, Stockholm.
    Änggård, Anders
    von Holst, Hans
    Transsphenoidal surgery in Cushing disease: 10 years of experience in 34 consecutive cases2004In: Journal of Neurosurgery, ISSN 0022-3085, E-ISSN 1933-0693, Vol. 100, p. 634-638Article in journal (Refereed)
    Abstract [en]

    Object. Cushing disease is a rare disorder. Because of their small size the adrenocorticotropic hormone (ACTH)—producing tumors are often not detectable on neuroimaging studies. To obtain a cure with transsphenoidal surgery (TSS) may therefore be difficult. In this report the authors present 10 years of experience in the treatment of patients with Cushing disease who were followed up with the same protocol and treated by the same surgeon.

    Methods. Thirty-four patients, 26 of them female and eight of them male (mean age 40 years, range 13–74 years) were studied. All had obvious clinical signs and symptoms of Cushing syndrome. Magnetic resonance (MR) imaging was performed in all patients, and inferior petrosal sinus (IPS) sampling was done in 14.

    In 12 patients MR imaging indicated a pituitary tumor; 10 were microadenomas and two were macroadenomas. In six patients with no visible tumor, the results of IPS sampling supported the diagnosis. All patients underwent TSS; the mean follow-up duration was 6 ± 0.5 years. Selective adenomectomy was performed in 32 and hemihypophysectomy in the other two patients. A cure was obtained in 31 patients (91%) after one TSS and in two more patients after further TSS; one patient was not cured despite two TSSs and one underwent bilateral adrenalectomy. Disease recurrence was seen in two patients after 3 years, and they were successfully treated with stereotactic gamma knife surgery. Half of the patients had an ACTH deficiency postoperatively, whereas one third had other pituitary hormone insufficiencies. There were no serious complications attributable to the surgical intervention.

    Conclusions. Transsphenoidal surgery with selective adenomectomy is an effective and safe treatment for Cushing disease. In the patients presented in this study, the surgical outcome seemed to depend on careful preoperative evaluation and the surgeon's experience. For optimal results in this rare disease the authors therefore suggest that the endocrinological, radiological, and surgical procedures be coordinated in a specialized center.

  • 6.
    Jedenmalm, Anneli
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. Lund University, Sweden.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Green, Douglas D.
    Loma Linda University, Orthopaedic Research Center.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Clarke, Ian C.
    Loma Linda University, Orthopaedic Research Center.
    Stark, Andreas
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Zeleznik, Michael P.
    Saya Systems Inc., Salt Lake City, UT, USA.
    Olivecrona, Henrik
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Validation of a 3D CT method for measurement of linear wear of acetabular cups: A hip simulator study2011In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 82, no 1, p. 35-41Article in journal (Refereed)
    Abstract [en]

    Material and methods Ultra-high molecular weight polyethylene cups with a titanium mesh molded on the outside were subjected to wear using a hip simulator. Before and after wear, they were (1) imaged with a CT scanner using a phantom model device, (2) measured using a coordinate measurement machine (CMM), and (3) weighed. CMM was used as the reference method for measurement of femoral head penetration into the cup and for comparison with CT, and gravimetric measurements were used as a reference for both CT and CMM. Femoral head penetration and wear vector angle were studied. The head diameters were also measured with both CMM and CT. The repeatability of the method proposed was evaluated with two repeated measurements using different positions of the phantom in the CT scanner. Results The accuracy of the 3D CT method for evaluation of linear wear was 0.51 mm and the repeatability was 0.39 mm. Repeatability for wear vector angle was 17 degrees A degrees. Interpretation This study of metal-meshed hip-simulated acetabular cups shows that CT has the capacity for reliable measurement of linear wear of acetabular cups at a clinically relevant level of accuracy.

  • 7. Liljeqvist, Moritz Lindquist
    et al.
    Hultgren, Rebecka
    Siika, Antti
    Gasser, T. Christian
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Roy, Joy
    Gender, smoking, body size, and aneurysm geometry influence the biomechanical rupture risk of abdominal aortic aneurysms as estimated by finite element analysis2017In: Journal of Vascular Surgery, ISSN 0741-5214, E-ISSN 1097-6809, Vol. 65, no 4, p. 1014-1021Article in journal (Refereed)
    Abstract [en]

    Objective: Finite element analysis (FEA) has been suggested to be superior to maximal diameter measurements in predicting rupture of abdominal aortic aneurysms (AAAs). Our objective was to investigate to what extent previously described rupture risk factors were associated with FEA-estimated rupture risk. Methods: One hundred forty-six patients with an asymptomatic AAA of a 40-to 60-mm diameter were retrospectively identified and consecutively included. The patients' computed tomography angiograms were analyzed by FEA without (neutral) and with (specific) input of patient-specific mean arterial pressure (MAP), gender, family history, and age. The maximal wall stress/wall strength ratio was described as a rupture risk equivalent diameter (RRED), which translated this ratio into an average aneurysm diameter of corresponding rupture risk. Results: In multivariate linear regression, RREDneutral increased with female gender (3.7 mm; 95% confidence interval [CI], 0.13-7.3) and correlated with patient height (0.27 mm/cm; 95% CI, 0.11-0.43) and body surface area (BSA, 16 mm/m(2); 95% CI, 8.3-24) and inversely with body mass index (BMI,-0.40 mm/kg m(-2); 95% CI, -0.75 to -0.054) in a wall stress-dependent manner. Wall stress-adjusted RREDneutral was raised if the patient was currently smoking (1.1 mm; 95% CI, 0.21-1.9). Age, MAP, family history, and patient weight were unrelated to RREDneutral. In specific FEA, RREDspecific increased with female gender, MAP, family history positive for AAA, height, and BSA, whereas it was inversely related to BMI. All results were independent of aneurysm diameter. Peak wall stress and RRED correlated with aneurysm diameter and lumen volume. Conclusions: Female gender, current smoking, increased patient height and BSA, and low BMI were found to increase the mechanical rupture risk of AAAs. Previously described rupture risk factors may in part be explained by patient characteristic-dependent variations in aneurysm biomechanics.

  • 8. Lundberg, J.
    et al.
    Razuvaev, A.
    Isaksson, B.
    Agustsson, T.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Holmin, S.
    Liver parenchyma access and lesion marker via the endovascular route2015In: Journal of Surgical Research, ISSN 0022-4804, E-ISSN 1095-8673, Vol. 195, no 2, p. 488-494Article in journal (Refereed)
    Abstract [en]

    Background Neoadjuvant chemotherapeutic regimens for metastatic colorectal cancer are now so effective that they can cause "vanishing" lesions. With new advances such as local ablation, intra-arterial treatments in bolus with pumps or with beads, and isolation of hepatic perfusion, the need for a working channel to the liver may be warranted, ideally reducing the risk of spreading neoplastic cells. Materials and methods The endovascular trans-vessel wall Extroducer device makes it possible to gain direct access to the liver parenchyma. The distal tip is then detached, to act as both a marker and a securing plug in the vessel defect. We used ex vivo and in vivo tests to evaluate the device as a working channel for local administration of substances to the parenchyma and as a marker for detection with both transabdominal and intraoperative ultrasonography. Results We could deploy the Extroducer device without any hemorrhagic or thromboembolic complications in vivo, and we were able to detect all markers ex vivo and in vivo using both transabdominal and intraoperative ultrasonography. Furthermore, we found that it is possible to administer substances to the liver parenchyma using the catheter. Conclusions The trans-vessel wall technique can be used to establish a working channel to the liver parenchyma for administration of any substance, such as chemotherapeutic agents or cells. The detached device can also be used as a marker for ultrasound-guided partial liver resection in "vanishing lesions." The technique should have a low risk of seeding of neoplastic cells. This study in large animals forms a strong basis for translation to clinical studies.

  • 9. Lundberg, J.
    et al.
    Stone-Elander, S.
    Zhang, X. -M
    Korsgren, O.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy.
    Holmin, S.
    Endovascular Method for Transplantation of Insulin-Producing Cells to the Pancreas Parenchyma in Swine2014In: American Journal of Transplantation, ISSN 1600-6135, E-ISSN 1600-6143, Vol. 14, no 3, p. 694-700Article in journal (Refereed)
    Abstract [en]

    Insulin-producing cells are transplanted by portal vein injection as an alternative to pancreas transplantation in both clinical and preclinical trials. Two of the main limitations of portal vein transplantation are the prompt activation of the innate immunity and concomitant loss of islets and a small but significant risk of portal vein thrombosis. Furthermore, to mimic physiological release, the insulin-producing cells should instead be located in the pancreas. The trans-vessel wall approach is an endovascular method for penetrating the vessel wall from the inside. In essence, a working channel is established to the parenchyma of organs that are difficult to access by percutaneous technique. In this experiment, we accessed the extra-vascular pancreatic parenchyma in swine by microendovascular technique and injected methylene blue, contrast fluids and insulin-producing cells without acute adverse events. Further, we evaluated the procedure itself by a 1-year angiographical follow-up, without adverse events. This study shows that the novel approach utilizing endovascular minimal invasiveness coupled to accurate trans-vessel wall placement of an injection in the pancreatic parenchyma with insulin-producing cells is possible. In clinical practice, the potential benefits compared to portal vein cell transplantation should significantly improve endocrine function of the graft and potentially reduce adverse events. This study presents one-year follow-up safety data on the microendovascular trans-vessel wall technique and shows that the technique can be used to transplant insulin-producing cells to the swine pancreas parenchyma.

  • 10.
    Martufi, Giampaolo
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
    Auer, Martin
    Roy, Joy
    Swedenborg, Jesper
    Sakalihasan, Natzi
    Panuccio, Giuseppe
    Gasser, T. Christian
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Biomechanics.
    Multidimensional growth measurements of abdominal aortic aneurysms2013In: Journal of Vascular Surgery, ISSN 0741-5214, E-ISSN 1097-6809, Vol. 58, no 3, p. 748-755Article in journal (Refereed)
    Abstract [en]

    Background: Monitoring the expansion of abdominal aortic aneurysms (AAAs) is critical to avoid aneurysm rupture in surveillance programs, for instance. However, measuring the change of the maximum diameter over time can only provide limited information about AAA expansion. Specifically, regions of fast diameter growth may be missed, axial growth cannot be quantified, and shape changes of potential interest for decisions related to endovascular aneurysm repair cannot be captured. Methods: This study used multiple centerline-based diameter measurements between the renal arteries and the aortic bifurcation to quantify AAA growth in 51 patients from computed tomography angiography (CTA) data. Criteria for inclusion were at least 1 year of patient follow-up and the availability of at least two sufficiently high-resolution CTA scans that allowed an accurate three-dimensional reconstruction. Consequently, 124 CTA scans were systematically analyzed by using A4clinics diagnostic software (VASCOPS GmbH, Graz, Austria), and aneurysm growth was monitored at 100 cross-sections perpendicular to the centerline. Results: Monitoring diameter development over the entire aneurysm revealed the sites of the fastest diameter growth, quantified the axial growth, and showed the evolution of the neck morphology over time. Monitoring the development of an aneurysm's maximum diameter or its volume over time can assess the mean diameter growth (r = 0.69, r = 0.77) but not the maximum diameter growth (r = 0.43, r = 0.34). The diameter growth measured at the site of maximum expansion was similar to 16%/y, almost four times larger than the mean diameter expansion of 4.4%/y. The sites at which the maximum diameter growth was recorded did not coincide with the position of the maximum baseline diameter (rho = 0.12; P = .31). The overall aneurysm sac length increased from 84 to 89 mm during the follow-up (P < .001), which relates to the median longitudinal growth of 3.5%/y. The neck length shortened, on average, by 6.2% per year and was accompanied by a slight increase in neck angulation. Conclusions: Neither maximum diameter nor volume measurements over time are able to measure the fastest diameter growth of the aneurysm sac. Consequently, expansion-related wall weakening might be inappropriately reflected by this type of surveillance data. In contrast, localized spots of fast diameter growth can be detected through multiple centerline-based diameter measurements over the entire aneurysm sac. This information might further reinforce the quality of aneurysm surveillance programs.

  • 11.
    Mihaescu, Mihai
    et al.
    Aerospace Engineering, University of Cincinnati.
    Murugappan, Shanmugam
    Otolargyngology, Head and Neck Surgery, University of Cincinnati-Medical Center.
    Gutmark, Ephraim
    Aerospace Engineering, University of Cincinnati.
    Donnelly, Lane
    Cincinnati Children's Hospital.
    Kalra, Maninder
    Cincinnati Children's Hospital.
    Computational Modeling of Upper Airway Before and After Adenotonsillectomy for Obstructive Sleep Apnea2008In: The Laryngoscope, ISSN 0023-852X, E-ISSN 1531-4995, Vol. 118, no 2, p. 360-362Article in journal (Refereed)
    Abstract [en]

    Adenotonsillectomy, the first-line surgical treatment for obstructive sleep apnea (OSA) in children, is successful in only 50% of obese children. Computational fluid dynamics tools, which have been applied to differentiate OSA patients from those without OSA based on the airway flow characteristics, can be potentially used to identify patients likely to benefit from surgical intervention. We present computational modeling of the upper airway before and after adenotonsillectomy in an obese female adolescent with OSA. The subject underwent upper airway imaging on a 1.5 Tesla magnetic resonance imaging (MRI) scanner, and three-dimensional airway models were constructed using airway boundary coordinates from cross-sectional MRI scans. Our results using computational simulations indicate that, in an obese child, the resolution of OSA after adenotonsillectomy is associated with changes in flow characteristics that result in decreased pressure differentials across the airway walls and thus lower compressive forces that predispose to airway collapse. Application of such findings to an obese child seeking surgical treatment for OSA can potentially lead to selection of the surgical procedure most likely to result in OSA resolution. Effective intervention for OSA in this high-risk group will result in reduction in morbidity and the public health concerns associated with OSA.

  • 12.
    Mihaescu, Mihai
    et al.
    Aerospace Engineering, University of Cincinnati.
    Mylavarapu, Goutham
    Aerospace Engineering, University of Cincinnati.
    Gutmark, Ephraim
    Aerospace Engineering, University of Cincinnati.
    Powell, Nelson
    Stanford University School of Medicine.
    Large Eddy Simulation of the pharyngeal airflow associated with Obstructive Sleep Apnea Syndrome at pre and post-surgical treatment2011In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 44, no 12, p. 2221-2228Article in journal (Refereed)
    Abstract [en]

    Obstructive Sleep Apnea Syndrome (OSAS) is the most common sleep-disordered breathing medical condition and a potentially life-threatening affliction. Not all the surgical or non-surgical OSAS therapies are successful for each patient, also in part because the primary factors involved in the etiology of this disorder are not completely understood. Thus, there is a need for improving both diagnostic and treatment modalities associated with OSAS. A verified and validated (in terms of mean velocity and pressure fields) Large Eddy Simulation approach is used to characterize the abnormal pharyngeal airflow associated with severe OSAS and its interaction with the airway wall in a subject who underwent surgical treatment. The analysis of the unsteady flow at pre- and post-treatment is used to illustrate the airflow dynamics in the airway associated with OSAS and to reveal as well, the changes in the flow variables after the treatment. At pre-treatment, large airflow velocity and wall shear stress values were found at the obstruction site in all cases. Downstream of obstruction, flow separation generated flow recirculation regions and enhanced the turbulence production in the jet-like shear layers. The interaction between the generated vortical structures and the pharyngeal airway wall induced large fluctuations in the pressure forces acting on the pharyngeal wall. After the surgery, the flow field instabilities vanished and both airway resistance and wall shear stress values were significantly reduced.

  • 13. Moore, Alastair J.
    et al.
    Cetti, Edward
    Haj-Yahia, Saleem
    Carby, Martin
    Bjoerling, Gunilla
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Shah, Pallav
    Goldstraw, Peter
    Moxham, John
    Jordan, Simon
    Polkey, Michael I.
    Unilateral Extrapulmonary Airway Bypass in Advanced Emphysema2010In: Annals of Thoracic Surgery, ISSN 0003-4975, E-ISSN 1552-6259, Vol. 89, no 3, p. 899-906E2Article in journal (Refereed)
    Abstract [en]

    Background. Gas trapping in emphysema results in resting and dynamic hyperinflation. We tested the hypothesis that a direct connection between the lung parenchyma and the atmosphere could increase expiratory flow and thereby potentially improve dyspnea through the relief of gas trapping. Methods. Ex vivo we studied 7 emphysematous lungs and 3 fibrotic lungs (as controls) and measured expiratory flow before and after airway bypass insertion during a forced maneuver in an artificial thorax. Pilot studies were conducted in vivo in 6 patients with advanced emphysema using a size 9 endotracheal tube as a bypass surgically placed through the chest wall into the upper lobe. Results. In the ex vivo emphysematous lungs the volume expelled during a forced expiratory maneuver increased from 169 to 235 mL (p < 0.05). In the in vivo group 4 patients retained the bypass tube for 3 months or more; total lung capacity was reduced, and the forced expiratory volume in 1 second increased by 23% (mean percent predicted at baseline versus 3 months, 24.4% versus 29.5%). Conclusions. An extrapulmonary airway bypass increases expiratory flow in emphysema. This may be a useful approach in hyperinflated patients with homogeneous emphysema. (Ann Thorac Surg 2010;89:899-906)

  • 14.
    Mylavarapu, Goutham
    et al.
    Aerospace Engineering, University of Cincinnati.
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Papatziamos, Georgios
    Karolinska Hospital.
    Gutmark, Ephraim
    Aerospace Engineering, University of Cincinnati.
    Planning human upper airway surgery using Computational Fluid Dynamics2013In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 46, no 12, p. 1979-1986Article in journal (Refereed)
    Abstract [en]

    The study advances the idea of using computational fluid dynamics in the process of planning surgical treatment modalities for patients with obstructive airway disorders. It is hypothesized that the a priori knowledge of the functional outcome of surgical intervention on the flow and airway resistance can guide the surgeon in choosing an effective surgical strategy. Computed tomography images spanning the respiratory tract of an adult patient with a combined glottic and subglottic stenosis are used to reconstruct three-dimensional geometrical models of the airway. Computational fluid dynamics is used to obtain airway flow patterns during inspiration and expiration in these models. Numerical predictions about flow velocity, pressure distribution on the airway lumen, wall shear stress, and airway resistance are obtained so that the relevance of each individual stenotic level is quantified. Four different virtual surgeries in different combinations are assessed in order to remedy the constricted airway. The virtual surgery based airway models are evaluated by comparisons with the pre-treatment flow modeling results. The predicted numerical data revealed that the removal of the constriction at the level of the vocal folds will have the most significant effect on the airway resistance. The flow simulations offer a quantitative method of evaluating the airway resistance in patients with combined glottic and subglottic stenoses. Predictions of airway resistances and other numerical calculations from different virtual surgeries give additional inputs for the surgeon, in deciding the most appropriate surgery on a case-by-case basis.

  • 15. Pedersen, T. O.
    et al.
    Xing, Z.
    Finne-Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hellem, S.
    Mustafa, K.
    Hyperbaric oxygen stimulates vascularization and bone formation in rat calvarial defects2013In: International Journal of Oral and Maxillofacial Surgery, ISSN 0901-5027, E-ISSN 1399-0020, Vol. 42, no 7, p. 907-914Article in journal (Refereed)
    Abstract [en]

    Hyperbaric oxygen (HBO) therapy is used to treat or prevent tissue necrosis in patients undergoing irradiation. Many such patients require reconstructive surgery, but little is known of the effects of HBO on bone vascularization and regeneration. In this study, copolymer poly(L-lactide-co-1,5-dioxepan-2-one) (poly(LLA-co-DXO)) scaffolds were implanted into critical-sized calvarial defects in Wistar rats. The animals were randomly allotted to hyperbaric or normobaric oxygen groups. The treatment group received five sessions weekly for 90 min at increased atmospheric pressure, for up to 4 weeks. Samples were retrieved at weeks 2 and 8, i.e. after a total of 10 and 20 sessions, respectively. The samples were analyzed by real-time reverse transcriptase polymerase chain reaction (RT-PCR) and histology at week 2, and radiographically and histologically at week 8. At week 2, defects treated with HBO exhibited greater numbers of cells positive for the endothelial marker CD31, up-regulated gene expression of osteogenic markers, and down-regulated expression of pro-inflammatory cytokines. At week 8, radiographic examination revealed that calvarial defects subjected to HBO exhibited a higher percentage of radiopacities than normobaric controls, and histological examination disclosed enhanced bone healing. These results confirmed that HBO treatment was effective in stimulating vascularization and bone formation in rat calvarial defects.

  • 16. Polzer, S.
    et al.
    Gasser, T. Christian
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Swedenborg, J.
    Bursa, J.
    The Impact of Intraluminal Thrombus Failure on the Mechanical Stress in the Wall of Abdominal Aortic Aneurysms2011In: European Journal of Vascular and Endovascular Surgery, ISSN 1078-5884, E-ISSN 1532-2165, Vol. 41, no 4, p. 467-473Article in journal (Refereed)
    Abstract [en]

    Objectives: The role of the intraluminal thrombus (ILT) in abdominal aortic aneurysm (AAA) rupture is controversial, and it is still not clear if an ILT increases or decreases AAA rupture risk. Specifically, signs of bleeding in the ILT are considered to increase AAA rupture risk. to further explore this hypothesis, intact AAAs (n = 4) with clear signs of fissures in the ILT, identified by computed tomography angiography (CTA) were investigated. Methods: Two different cases of ILT fissuring were investigated, where (1) ILT fissures were extracted directly from the CTA data and (2) a hypothetical fissure was introduced in the otherwise-intact ILT tissue. Wall stress distributions were predicted based on detailed Finite Element (FE) models. Results: ILT fissures extracted from CTA data locally increase the mechanical stress in the underlying wall by up to 30%. The largest impact on wall stress was observed if the ILT crack reaches the aneurysm wall, or if it involves large parts of the ILT. By contrast, a concentric failure in the medial ILT, which does not reach the aneurysm wall, has almost no impact on wall stress distribution. Hypothetical ILT fissures that connect the lumen with the wall cause a twofold increase of the stress in the underlying wall. Conclusions: ILT fissures increase the stress in the underlying wall, whereas regions other than that remain unaffected. If ILT fissures reach the wall or involve large parts of the ILT, the resulting increase in wall stress could possibly cause AAA rupture.

  • 17. Rosen, A.
    et al.
    Eliassi, S.
    Fors, U.
    Sallnäs Pysander, Eva Lotta
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    Forsslund, J.
    Sejersen, R.
    Lund, B.
    A computerised third molar surgery simulator - results of supervision by different professionals2014In: European journal of dental education, ISSN 1396-5883, E-ISSN 1600-0579, Vol. 18, no 2, p. 86-90Article in journal (Refereed)
    Abstract [en]

    The purpose of the study was to investigate which supervisory approach afforded the most efficient learning method for undergraduate students in oral and maxillofacial surgery (OMS) using a computerised third molar surgery simulator. Fifth year dental students participated voluntarily in a randomised experimental study using the simulator. The amount of time required and the number of trials used by each student were evaluated as a measure of skills development. Students had the opportunity to practise the procedure until no further visible improvements were achieved. The study assessed four different types of supervision to guide the students. The first group was where they were supported by a teacher/specialist in OMS, the second by a teaching assistant, the third group practised without any supervision and the fourth received help from a simulator technician/engineer. A protocol describing assessment criteria was designed for this purpose, and a questionnaire was completed by all participating students after the study. The average number of attempts required to virtually remove a third molar tooth in the simulator was 1.44 times for the group supervised by an OMS teacher; 1.5 times for those supervised by a teaching assistant; 2.8 times for those who had no supervision; and 3.6 times when support was provided only by a simulator technician. The results showed that the most efficient experience of the students was when they were helped by an OMS teacher or a teaching assistant. In a time and cost-effective perspective, supervision by a teaching assistant for a third molar surgery simulator would be the optimal choice.

  • 18.
    Skeppholm, Martin
    et al.
    Stockholm Spine Center, Löwenströmska Sjukhuset.
    Svedmark, Per
    Karolinska Institutet at Karolinska University Hospital Solna.
    Noz, Marilyn E.
    New York University.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Olivecrona, Henrik
    Olerud, Claes
    Department of Orthopedic Surgery, Uppsala University Hospital.
    Evaluation of mobility and stability in the Discover artificial disc: an in vivo motion study using high-accuracy 3D CT data2015In: Journal of Eurosurgery : Spine, ISSN 1547-5654, E-ISSN 1547-5646, Vol. 23, no 3, p. 383-389Article in journal (Refereed)
    Abstract [en]

    OBJECT Artificial disc replacement (ADR) devices are unlike implants used in cervical fusion in that they are continuously exposed to stress not only within the implant site but also at their site of attachment to the adjacent vertebra. An imaging technique with higher accuracy than plain radiography and with the possibility of 3D visualization would provide more detailed information about the motion quality and stability of the implant in relation to the vertebrae. Such high-accuracy studies have previously been conducted with radiostereometric analysis (RSA), which requires implantation of tantalum markers in the adjacent vertebrae. The aim of this study was to evaluate in vivo motion and stability of implanted artificial discs. A noninvasive analysis was performed with CT, with an accuracy higher than that of plain radiographs and almost as high as RSA in cervical spine. METHODS Twenty-eight patients with ADR were included from a larger cohort of a randomized controlled trial comparing treatment of cervical radiculopathy with ADR or anterior cervical decompression and fusion. Surgical levels included C4-7; 18 patients had 1-level surgery and 10 patients had 2-level surgery. Follow-up time ranged from 19 to 50 months, with an average of 40 months. Two CT volumes of the cervical spine, 1 in flexion and 1 in extension, were obtained in each patient and then spatially registered using a customized imaging tool, previously used and validated for the cervical spine. Motion between the components in the artificial disc, as well as motion between the components and adjacent vertebrae, were calculated in 3 planes. Intraclass correlation (ICC) between independent observers and repeatability of the method were also calculated. RESULTS Intrinsic motion, expressed as degrees in rotation and millimeters in translation, was detectable in a majority of the ADRs. In the sagittal plane, in which the flexion/extension was performed, sagittal rotation ranged between 0.2 and 15.8 and translation between 0.0 and 5.5 mm. Eight percent of the ADRs were classified as unstable, as motion between at least 1 of the components and the adjacent vertebra was detected. Five percent were classified as ankylotic, with no detectable motion, and another 8% showed very limited motion due to heterotopic ossification. Repeatability for the motion in the sagittal plane was calculated to be 1.300 for rotation and 1.29 mm for translation (95% confidence level), ICC 0.99 and 0.84, respectively. All 3 patients with unstable devices had undergone 1-level ADRs at C5-6. They all underwent revision surgery due to increased neck pain, and instability was established during the surgery. CONCLUSIONS The majority of the artificial discs in this study showed intrinsic mobility several years after implantation and were also shown to be properly attached. Implant instability was detected in 8% of patients and, as all of these patients underwent revision surgery due to increasing neck pain, this might be a more serious problem than heterotopic bone formation.

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