@article{AkbariShandizBoulosSavarssonetal.2017, author = {Akbari Shandiz, Mohsen and Boulos, Paul and S{\ae}varsson, Stefan and Ramm, Heiko and Fu, Chun Kit and Miller, Stephen and Zachow, Stefan and Anglin, Carolyn}, title = {Changes in Knee Shape and Geometry Resulting from Total Knee Arthroplasty}, series = {Journal of Engineering in Medicine}, volume = {232}, journal = {Journal of Engineering in Medicine}, number = {1}, doi = {10.1177/0954411917743274}, pages = {67 -- 79}, year = {2017}, abstract = {Changes in knee shape and geometry resulting from total knee arthroplasty can affect patients in numerous important ways: pain, function, stability, range of motion, and kinematics. Quantitative data concerning these changes have not been previously available, to our knowledge, yet are essential to understand individual experiences of total knee arthroplasty and thereby improve outcomes for all patients. The limiting factor has been the challenge of accurately measuring these changes. Our study objective was to develop a conceptual framework and analysis method to investigate changes in knee shape and geometry, and prospectively apply it to a sample total knee arthroplasty population. Using clinically available computed tomography and radiography imaging systems, the three-dimensional knee shape and geometry of nine patients (eight varus and one valgus) were compared before and after total knee arthroplasty. All patients had largely good outcomes after their total knee arthroplasty. Knee shape changed both visually and numerically. On average, the distal condyles were slightly higher medially and lower laterally (range: +4.5 mm to -4.4 mm), the posterior condyles extended farther out medially but not laterally (range: +1.8 to -6.4 mm), patellofemoral distance increased throughout flexion by 1.8-3.5 mm, and patellar thickness alone increased by 2.9 mm (range: 0.7-5.2 mm). External femoral rotation differed preop and postop. Joint line distance, taking cartilage into account, changed by +0.7 to -1.5 mm on average throughout flexion. Important differences in shape and geometry were seen between pre-total knee arthroplasty and post-total knee arthroplasty knees. While this is qualitatively known, this is the first study to report it quantitatively, an important precursor to identifying the reasons for the poor outcome of some patients. Using the developed protocol and visualization techniques to compare patients with good versus poor clinical outcomes could lead to changes in implant design, implant selection, component positioning, and surgical technique. Recommendations based on this sample population are provided. Intraoperative and postoperative feedback could ultimately improve patient satisfaction.}, language = {en} } @article{SaevarssonSharmaAmirietal.2012, author = {Saevarsson, Stefan and Sharma, Gulshan and Amiri, Shahram and Montgomery, Sigrun and Ramm, Heiko and Lichti, Derek and Lieck, Robert and Zachow, Stefan and Anglin, Carolyn}, title = {Radiological method for measuring patellofemoral tracking and tibiofemoral kinematics before and after total knee replacement}, series = {Bone and Joint Research}, volume = {1}, journal = {Bone and Joint Research}, number = {10}, doi = {10.1302/2046-3758.110.2000117}, pages = {263 -- 271}, year = {2012}, language = {en} } @misc{SharmaHoSaevarssonetal.2012, author = {Sharma, Gulshan and Ho, Karen and Saevarsson, Stefan and Ramm, Heiko and Lieck, Robert and Zachow, Stefan and Anglin, Carolyn}, title = {Knee Pose and Geometry Pre- and Post-Total Knee Arthroplasty Using Computed Tomography}, series = {58th Annual Meeting of the Orthopaedic Research Society (ORS)}, journal = {58th Annual Meeting of the Orthopaedic Research Society (ORS)}, address = {San Francisco, CA}, year = {2012}, language = {en} } @misc{SharmaSaevarssonAmirietal.2012, author = {Sharma, Gulshan and Saevarsson, Stefan and Amiri, Shahram and Montgomery, Sigrun and Ramm, Heiko and Lichti, Derek and Zachow, Stefan and Anglin, Carolyn}, title = {Sequential-Biplane Radiography for Measuring Pre and Post Total Knee Arthroplasty Kinematics}, series = {58th Annual Meeting of the Orthopaedic Research Society (ORS)}, journal = {58th Annual Meeting of the Orthopaedic Research Society (ORS)}, address = {San Francisco, CA}, year = {2012}, language = {en} } @inproceedings{StefanGulshanSigrunetal.2012, author = {Stefan, Saevarsson and Gulshan, Sharma and Sigrun, Montgomery and Karen, Ho and Ramm, Heiko and Lieck, Robert and Zachow, Stefan and Hutchison, Carol and Jason, Werle and Carolyn, Anglin}, title = {Kinematic Comparison Between Gender Specific and Traditional Femoral Implants}, series = {67th Canadian Orthopaedic Association (COA) Annual Meeting}, booktitle = {67th Canadian Orthopaedic Association (COA) Annual Meeting}, year = {2012}, language = {en} } @article{HoSaevarssonRammetal.2012, author = {Ho, Karen and Saevarsson, Stefan and Ramm, Heiko and Lieck, Robert and Zachow, Stefan and Sharma, Gulshan and Rex, Erica and Amiri, Shahram and Wu, Barnabas and Leumann, Andre and Anglin, Carolyn}, title = {Computed tomography analysis of knee pose and geometry before and after total knee arthroplasty}, series = {Journal of biomechanics}, volume = {45}, journal = {Journal of biomechanics}, number = {13}, doi = {10.1016/j.jbiomech.2012.06.004}, pages = {2215 -- 21}, year = {2012}, language = {en} } @article{HildebrandtGoubergritsHepptetal.2013, author = {Hildebrandt, Thomas and Goubergrits, Leonid and Heppt, Werner and Bessler, Stefan and Zachow, Stefan}, title = {Evaluation of the Intranasal Flow Field through Computational Fluid Dynamics (CFD)}, series = {Journal of Facial and Plastic Surgery}, volume = {29}, journal = {Journal of Facial and Plastic Surgery}, number = {2}, publisher = {Thieme}, doi = {10.1055/s-0033-1341591}, pages = {93 -- 98}, year = {2013}, language = {en} } @article{SaevarssonSharmaRammetal.2013, author = {Saevarsson, Stefan and Sharma, Gulshan and Ramm, Heiko and Lieck, Robert and Hutchison, Carol and Werle, Jason and Montgomery, Sigrun and Romeo, Carolina and Zachow, Stefan and Anglin, Carolyn}, title = {Kinematic Differences Between Gender Specific And Traditional Knee Implants}, series = {The Journal of Arthroplasty}, volume = {28}, journal = {The Journal of Arthroplasty}, number = {9}, doi = {10.1016/j.arth.2013.01.021}, pages = {1543 -- 1550}, year = {2013}, language = {en} } @phdthesis{Zachow, author = {Zachow, Stefan}, title = {Computergest{\"u}tzte 3D Osteotomieplanung in der Mund-Kiefer-Gesichtschirurgie unter Ber{\"u}cksichtigung der r{\"a}umlichen Weichgewebeanordnung}, isbn = {3899631986}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10432}, abstract = {In der Arbeit wird die computergest{\"u}tzte Planung von chirurgisch gesetzten Knochenfrakturen bzw. Knochenschnitten (sogenannten Osteotomien) an dreidimensionalen, computergrafischen Sch{\"a}delmodellen, sowie die Umpositionierung separierter kn{\"o}cherner Segmente im Kontext der rekonstruktiven MKG-Chirurgie behandelt. Durch die 3D Modellierung und Visualisierung anatomischer Strukturen, sowie der 3D Osteotomie- und Umstellungsplanung unter Einbeziehung der resultierenden Weichgewebedeformation wird den Chirurgen ein Werkzeug an die Hand gegeben, mit dem eine Therapieplanung am Computer durchgef{\"u}hrt und diese in Hinblick auf Funktion und {\"A}sthetik bewertet werden kann. Unterschiedliche Strategien k{\"o}nnen dabei erprobt und in ihrer Auswirkung erfasst werden. Dazu wird ein methodischer Ansatz vorgestellt, der zum einen die chirurgische Planung im Vergleich zu existierenden Ans{\"a}tzen deutlich verbessert und zum anderen eine robuste Weichgewebeprognose, durch den Einsatz geeigneter Planungsmodelle und eines physikalisch basierten Weichgewebemodells unter Nutzung numerischer L{\"o}sungsverfahren in die Planung integriert. Die Visualisierung der Planungsergebnisse erlaubt sowohl eine anschauliche und {\"u}berzeugende, pr{\"a}operative Patientenaufkl{\"a}rung, als auch die Demonstration m{\"o}glicher Vorgehensweisen und deren Auswirkungen f{\"u}r die chirurgische Ausbildung. Ferner erg{\"a}nzen die Planungsdaten die Falldokumentation und liefern einen Beitrag zur Qualit{\"a}tssicherung. Die Arbeit ist in sieben Kapitel gegliedert und wie folgt strukturiert: Zuerst wird die medizinische Aufgabenstellung bei der chirurgischen Rekonstruktion von Knochenfehlbildungen und -fehlstellungen in der kraniofazialen Chirurgie sowie die daraus resultierenden Anforderungen an die Therapieplanung beschrieben. Anschließend folgt ein umfassender {\"U}berblick {\"u}ber entsprechende Vorarbeiten zur computergest{\"u}tzten Planung knochenverlagernder Operationen und eine kritische Bestandsaufnahme der noch vorhandenen Defizite. Nach der Vorstellung des eigenen Planungsansatzes wird die Generierung individueller, qualitativ hochwertiger 3D Planungsmodelle aus tomografischen Bilddaten beschrieben, die den Anforderungen an eine intuitive, 3D Planung von Umstellungsosteotomien entsprechen und eine Simulation der daraus resultierenden Weichgewebedeformation mittels der Finite-Elemente Methode (FEM) erm{\"o}glichen. Die Methoden der 3D Schnittplanung an computergrafischen Modellen werden analysiert und eine 3D Osteotomieplanung an polygonalen Sch{\"a}delmodellen entwickelt, die es erm{\"o}glicht, intuitiv durch Definition von Schnittlinien am 3D Knochenmodell, eine den chirurgischen Anforderungen entsprechende Schnittplanung unter Ber{\"u}cksichtigung von Risikostrukturen durchzuf{\"u}hren. Separierte Knochensegmente lassen sich im Anschluss interaktiv umpositionieren und die resultierende Gesamtanordnung hinsichtlich einer funktionellen Rehabilitation bewerten. Aufgrund des in dieser Arbeit gew{\"a}hlten, physikalisch basierten Modellierungsansatzes kann unter Ber{\"u}cksichtigung des gesamten Weichgewebevolumens aus der Knochenverlagerung direkt die resultierende Gesichtsform berechnet werden. Dies wird anhand von 13 exemplarischen Fallstudien anschaulich demonstriert, wobei die Prognosequalit{\"a}t mittels postoperativer Fotografien und postoperativer CT-Daten {\"u}berpr{\"u}ft und belegt wird. Die Arbeit wird mit einem Ausblick auf erweiterte Modellierungsans{\"a}tze und einem Konzept f{\"u}r eine integrierte, klinisch einsetzbare Planungsumgebung abgeschlossen.}, language = {de} } @misc{ZachowZilskeHege, author = {Zachow, Stefan and Zilske, Michael and Hege, Hans-Christian}, title = {3D reconstruction of individual anatomy from medical image data: Segmentation and geometry processing}, issn = {1438-0064}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-10440}, number = {07-41}, abstract = {For medical diagnosis, visualization, and model-based therapy planning three-dimensional geometric reconstructions of individual anatomical structures are often indispensable. Computer-assisted, model-based planning procedures typically cover specific modifications of "virtual anatomy" as well as numeric simulations of associated phenomena, like e.g. mechanical loads, fluid dynamics, or diffusion processes, in order to evaluate a potential therapeutic outcome. Since internal anatomical structures cannot be measured optically or mechanically in vivo, three-dimensional reconstruction of tomographic image data remains the method of choice. In this work the process chain of individual anatomy reconstruction is described which consists of segmentation of medical image data, geometrical reconstruction of all relevant tissue interfaces, up to the generation of geometric approximations (boundary surfaces and volumetric meshes) of three-dimensional anatomy being suited for finite element analysis. All results presented herein are generated with amira ® - a highly interactive software system for 3D data analysis, visualization and geometry reconstruction.}, language = {en} }