@article{VisscherWyssSinghetal., author = {Visscher, Rosa and Wyss, C. and Singh, Navrag B. and Taylor, William R. and Dendorfer, Sebastian and Rutz, E. and Brunner, Reinald}, title = {Influence of TAL-TATS surgery on energy production of Tricepts Surae - A musculoskeletal modeling evaluation}, series = {Gait \& Posture}, volume = {81}, journal = {Gait \& Posture}, number = {Suppl. 1}, publisher = {Elsevier}, doi = {10.1016/j.gaitpost.2020.08.090}, pages = {381 -- 382}, language = {en} } @article{VoellnerWeberWeberetal., author = {V{\"o}llner, Florian and Weber, Tim A. and Weber, Markus and Renkawitz, Tobias and Dendorfer, Sebastian and Grifka, Joachim and Craiovan, Benjamin}, title = {A simple method for determining ligament stiffness during total knee arthroplasty in vivo}, series = {Scientific Reports}, volume = {9}, journal = {Scientific Reports}, publisher = {Nature}, doi = {10.1038/s41598-019-41732-x}, pages = {1 -- 8}, abstract = {A key requirement in both native knee joints and total knee arthroplasty is a stable capsular ligament complex. However, knee stability is highly individual and ranges from clinically loose to tight. So far, hardly any in vivo data on the intrinsic mechanical of the knee are available. This study investigated if stiffness of the native ligament complex may be determined in vivo using a standard knee balancer. Measurements were obtained with a commercially available knee balancer, which was initially calibrated in vitro. 5 patients underwent reconstruction of the force-displacement curves of the ligament complex. Stiffness of the medial and lateral compartments were calculated to measure the stability of the capsular ligament complex. All force-displacement curves consisted of a non-linear section at the beginning and of a linear section from about 80 N onwards. The medial compartment showed values of 28.4 ± 1.2 N/mm for minimum stiffness and of 39.9 ± 1.1 N/mm for maximum stiffness; the respective values for the lateral compartment were 19.9 ± 0.9 N/mm and 46.6 ± 0.8 N/mm. A commercially available knee balancer may be calibrated for measuring stiffness of knee ligament complex in vivo, which may contribute to a better understanding of the intrinsic mechanical behaviour of knee joints.}, subject = {Biomechanische Analyse}, language = {en} } @article{WagnerKranzKrenkeletal., author = {Wagner, Maria Stella and Kranz, Michael and Krenkel, Lars and Pointner, Daniel and Foltan, Maik and Lubnow, Matthias and Lehle, Karla}, title = {Computer based visualization of clot structures in extracorporeal membrane oxygenation and histological clot investigations for understanding thrombosis in membrane lungs}, series = {Frontiers in Medicine}, journal = {Frontiers in Medicine}, number = {11}, editor = {Becatti, Matteo}, publisher = {Frontiers}, doi = {10.3389/fmed.2024.1416319}, abstract = {Extracorporeal membrane oxygenation (ECMO) was established as a treatment for severe cardiac or respiratory disease. Intra-device clot formation is a common risk. This is based on complex coagulation phenomena which are not yet sufficiently understood. The objective was the development and validation of a methodology to capture the key properties of clots deposed in membrane lungs (MLs), such as clot size, distribution, burden, and composition. One end-oftherapy PLS ML was examined. Clot detection was performed using multidetector computed tomography (MDCT), microcomputed tomography (μCT), and photography of fiber mats (fiber mat imaging, FMI). Histological staining was conducted for von Willebrand factor (vWF), platelets (CD42b, CD62P), fibrin, and nucleated cells (4′, 6-diamidino-2-phenylindole, DAPI). The three imaging methods showed similar clot distribution inside the ML. Independent of the imaging method, clot loading was detected predominantly in the inlet chamber of the ML. The μCT had the highest accuracy. However, it was more expensive and time consuming than MDCT or FMI. The MDCT detected the clots with low scanning time. Due to its lower resolution, it only showed clotted areas but not the exact shape of clot structures. FMI represented the simplest variant, requiring little effort and resources. FMI allowed clot localization and calculation of clot volume. Histological evaluation indicated omnipresent immunological deposits throughout the ML. Visually clot-free areas were covered with leukocytes and platelets forming platelet-leukocyte aggregates (PLAs). Cells were embedded in vWF cobwebs, while vWF fibers were negligible. In conclusion, the presented methodology allowed adequate clot identification and histological classification of possible thrombosis markers such as PLAs.}, language = {en} } @misc{WagnerKrenkelDoenitzetal., author = {Wagner, Thomas and Krenkel, Lars and D{\"o}nitz, Christian and Brawanski, Alexander}, title = {Influence of CFD Strategy on WSS and OSI Determination for Intracranial Aneurysm Rupture Assessment}, series = {25th Congress of the European Society of Biomechanics, July 7-10, 2019, Vienna, Austria}, journal = {25th Congress of the European Society of Biomechanics, July 7-10, 2019, Vienna, Austria}, language = {en} } @article{WeberMerleNawabietal., author = {Weber, Markus and Merle, Christian and Nawabi, Danyal H. and Dendorfer, Sebastian and Grifka, Joachim and Renkawitz, Tobias}, title = {Inaccurate offset restoration in total hip arthroplasty results in reduced range of motion}, series = {Scientific Reports}, volume = {10}, journal = {Scientific Reports}, number = {13208}, publisher = {Nature}, doi = {10.1038/s41598-020-70059-1}, pages = {9}, abstract = {Offset restoration in total hip arthroplasty (THA) is associated with postoperative range of motion (ROM) and gait kinematics. We aimed to research into the impact of high offset (HO) and standard stems on postoperative ROM. 121 patients received cementless THA through a minimally-invasive anterolateral approach. A 360° hip ROM analysis software calculated impingement-free hip movement based on postoperative 3D-CTs compared to ROM values necessary for activities of daily living (ADL). The same model was then run a second time after changing the stem geometry between standard and HO configuration with the implants in the same position. HO stems showed higher ROM for all directions between 4.6 and 8.9° (p < 0.001) compared with standard stems but with high interindividual variability. In the subgroup with HO stems for intraoperative offset restoration, the increase in ROM was even higher for all ROM directions with values between 6.1 and 14.4° (p < 0.001) compared to offset underrestoration with standard stems. Avoiding offset underrestoration resulted in a higher amount of patients of over 20\% for each ROM direction that fulfilled the criteria for ADL (p < 0.001). In contrast, in patients with standard stems for offset restoration ROM did increase but not clinically relevant by offset overcorrection for all directions between 3.1 and 6.1° (p < 0.001). Offset overcorrection by replacing standard with HO stems improved ROM for ADL in a low number of patients below 10\% (p > 0.03). Patient-individual restoration of offset is crucial for free ROM in THA. Both over and underrestoration of offset should be avoided.}, language = {en} } @article{WeberSuessJerabeketal., author = {Weber, Markus and Suess, Franz and Jerabek, Seth and Meyer, Matthias and Grifka, Joachim and Renkawitz, Tobias and Dendorfer, Sebastian}, title = {Kinematic pelvic tilt during gait alters functional cup position in total hip arthroplasty}, series = {Journal of Orthopaedic Research}, volume = {40}, journal = {Journal of Orthopaedic Research}, number = {4}, publisher = {Wiley}, issn = {1554-527X}, doi = {10.1002/jor.25106}, pages = {846 -- 853}, abstract = {Static pelvic tilt impacts functional cup position in total hip arthroplasty (THA). In the current study we investigated the effect of kinematic pelvic changes on cup position. In the course of a prospective controlled trial postoperative 3D-computed tomography (CT) and gait analysis before and 6 and 12 months after THA were obtained in 60 patients. Kinematic pelvic motion during gait was measured using Anybody Modeling System. By fusion with 3D-CT, the impact of kinematic pelvic tilt alterations on cup anteversion and inclination was calculated. Furthermore, risk factors correlating with high pelvic mobility were evaluated. During gait a high pelvic range of motion up to 15.6° exceeding 5° in 61.7\% (37/60) of patients before THA was found. After surgery, the pelvis tilted posteriorly by a mean of 4.0 ± 6.6° (p < .001). The pelvic anteflexion led to a mean decrease of -1.9 ± 2.2° (p < .001) for cup inclination and -15.1 ± 6.1° (p < .001) for anteversion in relation to the anterior pelvic plane (APP). Kinematic pelvic changes resulted in a further change up to 2.3° for inclination and up to 12.3° for anteversion. In relation to the preoperative situation differences in postoperative cup position ranged from -4.4 to 4.6° for inclination and from -7.8 to 17.9° for anteversion, respectively. Female sex (p < .001) and normal body weight (p < .001) correlated with high alterations in pelvic tilt. Kinematic pelvic changes highly impact cup anteversion in THA. Surgeons using the APP as reference should aim for a higher anteversion of about 15° due to the functional anteflexion of the pelvis during gait.}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{WeberWeberWoerneretal., author = {Weber, Markus and Weber, Tim A. and Woerner, Michael and Craiovan, Benjamin and Worlicek, Michael and Winkler, Sebastian and Grifka, Joachim and Renkawitz, Tobias}, title = {The impact of standard combined anteversion definitions on gait and clinical outcome within one year after total hip arthroplasty}, series = {International Orthopaedics}, volume = {39}, journal = {International Orthopaedics}, number = {12}, doi = {10.1007/s00264-015-2777-8}, pages = {2323 -- 2333}, abstract = {Different target areas within the concept of combined cup and stem anteversion have been published for total hip arthroplasty (THA). We asked whether component positioning according to eight standard combined anteversion rules is associated with (1) more physiological gait patterns, (2) higher improvement of gait variables and (3) better clinical outcome after THA.In a prospective clinical study, 60 patients received cementless THA through an anterolateral MIS approach in a lateral decubitus position. Six weeks postoperatively, implant position was analysed using 3D-CT by an independent external institute. Preoperatively, six and 12 months postoperatively range of motion, normalized walking speed and hip flexion symmetry index were measured using 3D motion-capture gait analysis. Patient-related outcome measures (HHS, HOOS, EQ-5D) were obtained by an observer blinded to 3D-CT results. Eight combined anteversion definitions and Lewinnek's "safe zone" were evaluated regarding their impact on gait patterns and clinical outcome.Combined cup and stem anteversion according to standard combined anteversion definitions as well as cup placement within Lewinnek's "safe zone" did not influence range of motion, normalized walking speed and/or hip flexion symmetry index six and 12 months after THA. Similarly, increase of gait parameters within the first year after THA was comparable between all eight combined anteversion rules. Clinical outcome measures like HHS, HOOS and EQ-5D did not show any benefit for either of the combined anteversion definitions.Standard combined cup and stem anteversion rules do not improve postoperative outcome as measured by gait analysis and clinical scores within one year after THA.}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{WeberDendorferBulstraetal., author = {Weber, Tim A. and Dendorfer, Sebastian and Bulstra, Sjoerd K. and Grifka, Joachim and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {Gait six month and one-year after computer assisted Femur First THR vs. conventional THR. Results of a patient- and observer- blinded randomized controlled trial}, series = {Gait \& Posture}, volume = {vol. 49}, journal = {Gait \& Posture}, doi = {10.1016/j.gaitpost.2016.06.035}, pages = {418 -- 425}, abstract = {A prospective randomized controlled trial is presented that is used to compare gait performance between the computer assisted Femur First (CAS FF) operation method and conventional THR (CON). 60 patients underwent a 3D gait analysis of the lower extremity at pre-operative, 6 months post-operative and twelve months post-operative. Detailed verification experiments were facilitated to ensure the quality of data as well as to avoid over-interpreting of the data. The results confirm a similar data-quality as reported in the literature. Walking speed, range of motion and symmetry thereof improved over the follow-up period, without significant differences between the groups. While all parameters do significantly increase over the follow-up period for both groups, there were no significant differences between them at any given time-point. Patients undergoing CAS FF showed a trend to improved hip flexion angle indicating a possible long-term benefit.}, language = {en} } @inproceedings{WeberDendorferDullienetal., author = {Weber, Tim A. and Dendorfer, Sebastian and Dullien, Silvia and Grifka, Joachim and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {Measuring functional outcome after total hip replacement with subject-specific hip joint loading}, series = {Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine}, volume = {226}, booktitle = {Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine}, number = {12}, doi = {10.1177/0954411912447728}, pages = {939 -- 946}, abstract = {Total hip replacement is an often-performed orthopedic surgical procedure; the amount of procedures undertaken will increase since our life expectancy is growing. In order to optimize function, hip biomechanics should be restored to as near normal as possible. The goal of this pilot study was to determine whether or not it is feasible to compute the vectorial hip reaction force pathways on the head of the prosthesis and the force angles relative to the cup of the prosthesis that occur during gait in total hip replacement patients, serving as an objective measurement of the functional outcome following hip replacement. A three-dimensional gait analysis, measuring ground reaction forces and kinematics, was performed. The data retrieved from the gait analysis was used as the input for the musculoskeletal model to compute vectorial joint reaction forces for data processing. To evaluate the position and orientation of the joint reaction forces, the force path, as well as the force angles for the operated and non-operated joint, has been calculated during the stance phase of the specific leg. The force path for subject 2 on the non-operated side is only located in the posterior-lateral quarter, as is the force path for subject 1. In contrast to this subject, the force path for subject 2 at the operated hip joint can be found only within the anterior quarter of the head of the implant, where it is nearly equally distributed in the medio-lateral half of the prosthesis head. The force-inclination angles on the cup of subject 1, with respect to the plane of the socket face, indicates that the force vector is mainly positioned in the same quadrant when compared with subject 2 (in a cup-fixed coordinate system). The force-anteversion angle behaves similarly to the force-inclination angle, even when the effects are not as pronounced. The proposed methods in this article are aiming to define two functional outcomes of total hip replacement that are related to wear and rim loading. It is accepted that wear is not only a function of time, but a function of use. Owing to the methods listed in this article, we are able to determine a) the applied force and b) the sliding distance (force pathway) in a subject-specific manner. The computed hip-reaction force angles and the distance to the rim cup are a measurement for cup or rim loading, and occurs in the so-called safe-zones. This method may well give us insight into the biomechanical situation during gait, after receiving total hip replacement, that we need to fully understand the mechanisms acting on a hip joint and to prove a possible increase of functional outcome after receiving total hip replacement.}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{WeberDendorferGrifkaetal., author = {Weber, Tim A. and Dendorfer, Sebastian and Grifka, Joachim and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {Does Computer-Assisted Femur First THR Improve Musculoskeletal Loading Conditions?}, series = {BioMed Research International}, volume = {2015}, journal = {BioMed Research International}, editor = {Takagi, Michiaki}, doi = {10.1155/2015/625317}, pages = {ID 625317}, abstract = {We have developed a novel, computer-assisted operation method for minimal-invasive total hip replacement (THR) following the concept of "femur first/combined anteversion," which incorporates various aspects of performing a functional optimization of the prosthetic stem and cup position (CAS FF). The purpose of this study is to assess whether the hip joint reaction forces and patient's gait parameters are being improved by CAS FF in relation to conventional THR (CON). We enrolled 60 patients (28 CAS FF/32 CON) and invited them for gait analysis at three time points (preoperatively, postop six months, and postop 12 months). Data retrieved from gait analysis was processed using patient-specific musculoskeletal models. The target parameters were hip reaction force magnitude (hrf), symmetries, and orientation with respect to the cup. Hrf in the CAS FF group were closer to a young healthy normal. Phase-shift symmetry showed an increase in the CAS FF group. Hrf orientation in the CAS FF group was closer to optimum, though no edge or rim-loading occurred in the CON group as well. The CAS FF group showed an improved hrf orientation in an early stage and a trend to an improved long-term outcome.}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @article{WeberAlMunajjedVerkerkeetal., author = {Weber, Tim and Al-Munajjed, Amir Andreas and Verkerke, Gijsbertus Jacob and Dendorfer, Sebastian and Renkawitz, Tobias}, title = {Influence of minimally invasive total hip replacement on hip reaction forces and their orientations}, series = {Journal of Orthopaedic Research}, volume = {32}, journal = {Journal of Orthopaedic Research}, number = {12}, doi = {10.1002/jor.22710}, pages = {1680 -- 1687}, abstract = {Minimally invasive surgery (MIS) is becoming increasingly popular. Supporters claim that the main advantages of MIS total hip replacement (THR) are less pain and a faster rehabilitation and recovery. Critics claim that safety and efficacy of MIS are yet to be determined. We focused on a biomechanical comparison between surgical standard and MIS approaches for THR during the early recovery of patients. A validated, parameterized musculoskeletal model was set to perform a squat of a 50th percentile healthy European male. A bilateral motion was chosen to investigate effects on the contralateral side. Surgical approaches were simulated by excluding the incised muscles from the computations. Resulting hip reaction forces and their symmetry and orientation were analyzed. MIS THR seemed less influential on the symmetry index of hip reaction forces between the operated and nonoperated leg when compared to the standard lateral approach. Hip reaction forces at peak loads of the standard transgluteal approach were 24\% higher on the contralateral side when compared to MIS approaches. Our results suggest that MIS THR contributes to a greater symmetry of hip reaction forces in absolute value as well as force-orientation following THR.}, subject = {H{\"u}ftgelenkprothese}, language = {en} } @inproceedings{WeberDendorferBulstraetal., author = {Weber, Tim and Dendorfer, Sebastian and Bulstra, Sjoerd K. and Grifka, Joachim and Verkerke, Gijsbertus Jacob and Renkawitz, Tim}, title = {Navigated Femur First Total Hip Arthroplasty leads to improved Biomechanical Outcome after surgery}, series = {ORS annual meeting, Las Vegas, USA, 2015}, booktitle = {ORS annual meeting, Las Vegas, USA, 2015}, language = {en} } @inproceedings{WeberDendorferBulstraetal., author = {Weber, Tim and Dendorfer, Sebastian and Bulstra, Sjoerd K. and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {Biomechanical Outcome after computer-assisted vs. Conventional THR}, series = {ANSYS Conference \& 32th CADFEM Users' Meeting 2014, 04.-06. Juni, N{\"u}rnberg}, booktitle = {ANSYS Conference \& 32th CADFEM Users' Meeting 2014, 04.-06. Juni, N{\"u}rnberg}, language = {en} } @inproceedings{WeberDendorferBulstraetal., author = {Weber, Tim and Dendorfer, Sebastian and Bulstra, Sjoerd K. and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {Musculoskeletal modeling for orthopedic surgery - Applications and chances}, series = {Orthopedics meets Engineering, Regensburg, 2015}, booktitle = {Orthopedics meets Engineering, Regensburg, 2015}, language = {en} } @inproceedings{WeberDendorferGrifkaetal., author = {Weber, Tim and Dendorfer, Sebastian and Grifka, Joachim and Weber, Markus and W{\"o}rner, Michael and Dullien, Silvia and Verkerke, Gijsbertus Jacob and Renkawitz, Tobias}, title = {Verbessert die computerassistierte Femur First Operationstechnik f{\"u}r die H{\"u}ftendoprothetik den muskuloskelettalen Lastfall auf das H{\"u}ftgelenk?}, series = {DKOU 2015, Deutscher Kongress f{\"u}r Orthop{\"a}die und Unfallchirurgie 2015}, booktitle = {DKOU 2015, Deutscher Kongress f{\"u}r Orthop{\"a}die und Unfallchirurgie 2015}, language = {de} } @inproceedings{WeberDendorferRenkawitzetal., author = {Weber, Tim and Dendorfer, Sebastian and Renkawitz, Tobias and Dullien, Silvia and Grifka, Joachim}, title = {Clinical gait analysis combined with musculoskeletal modelling - coding a new generation of evaluation instruments}, series = {Deutsche Gesellschaft f{\"u}r Biomechanik, Murnau, 2011}, booktitle = {Deutsche Gesellschaft f{\"u}r Biomechanik, Murnau, 2011}, language = {en} } @article{WeberDullienGrifkaetal., author = {Weber, Tim and Dullien, Silvia and Grifka, Joachim and Renkawitz, Tobias and Dendorfer, Sebastian}, title = {Validation of a Motion Capture Laboratory and a new marker-placement protcol for clinical applications}, series = {Gait \& Posture}, volume = {38}, journal = {Gait \& Posture}, number = {Suppl. 1}, doi = {10.1016/j.gaitpost.2013.07.229}, pages = {113 -- 114}, language = {en} } @inproceedings{WeberDullienPutzeretal., author = {Weber, Tim and Dullien, Silvia and Putzer, Michael and Dendorfer, Sebastian and Renkawitz, Tobias}, title = {Biomechanical outcome after computer-assisted vs. conventional THR - study concept and preliminary gait analysis results}, series = {GAMMA Workshop, Hannover, 2012}, booktitle = {GAMMA Workshop, Hannover, 2012}, language = {en} } @inproceedings{WeberRenkawitzBulstraetal., author = {Weber, Tim and Renkawitz, Tobias and Bulstra, Sjoerd K. and Grifka, Joachim and Verkerke, Gijsbertus Jacob and Dendorfer, Sebastian}, title = {Biomechanics of computer-assisted vs. conventional THR after one year follow up}, series = {XXV Congress of the International Society of Biomechanics, Glasgow, UK, 12th-16th July 2015}, booktitle = {XXV Congress of the International Society of Biomechanics, Glasgow, UK, 12th-16th July 2015}, language = {en} } @inproceedings{WeberRenkawitzGrifkaetal., author = {Weber, Tim and Renkawitz, Tobias and Grifka, Joachim and Bulstra, Sjoerd K. and Verkerke, Gijsbertus Jacob and Dendorfer, Sebastian}, title = {The musculoskeletal load scenario of computer-assisted Femur-First THR up to one year after surgery}, series = {VI International Conference on Computational Bioengineering, Barcelona, Sept. 2015}, booktitle = {VI International Conference on Computational Bioengineering, Barcelona, Sept. 2015}, language = {en} }