M. Beek - Academia.edu (original) (raw)
Papers by M. Beek
Journal of Dental Research, 2001
The cartilaginous intra-articular disc of the human temporomandibular joint shows clear anteropos... more The cartilaginous intra-articular disc of the human temporomandibular joint shows clear anteroposterior variations in its morphology. However, anteroposterior variations in its tissue behavior have not been investigated thoroughly. To test the hypothesis that the mechanical properties of fresh human temporomandibular joint discs vary in anteroposterior direction, we performed dynamic indentation tests at three anteroposteriorly different locations. The disc showed strong viscoelastic behavior dependent on the amplitude and frequency of the indentation, the location, and time. The resistance against deformations and the shock absorbing capabilities were larger in the intermediate zone than in regions located more anteriorly and posteriorly. Because several studies have predicted that the intermediate zone is the predominantly loaded region of the disc, it can be concluded that the topological variations in its tissue behavior enable the disc to combine the functions of load distribut...
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2007
The general framework and experimental validation of a novel navigation system designed for shoul... more The general framework and experimental validation of a novel navigation system designed for shoulder arthroscopy are presented. The system was designed to improve the surgeon's perception of the three-dimensional space within the human shoulder. Prior to surgery, a surface model of the shoulder was created from computed tomography images. Intraoperatively optically tracked arthroscopic instruments were calibrated. The surface model was then registered to the patient using tracked freehand ultrasound images taken from predefined landmark regions on the scapula. Three-dimensional models of the surgical instruments were displayed, in real time, relative to the surface model in a user interface. Laboratory experiments revealed only small registration and calibration errors, with minimal time needed to complete the intraoperative tasks.
Journal of Dental Research, 2001
While the movability of the human temporomandibular joint is great, the strains and stresses in t... more While the movability of the human temporomandibular joint is great, the strains and stresses in the cartilaginous structures might largely depend on the position of the mandible with respect to the skull. This hypothesis was investigated by means of static three-dimensional finite element simulations involving different habitual condylar positions. Furthermore, the influence of several model parameters was examined by sensitivity analyses. The results indicated that the disc moved together with the condyle in the anterior direction without the presence of ligaments and the lateral pterygoid muscle. By adapting its shape to the changing geometry of the articular surfaces, the disc prevented small contact areas and thus local peak loading. In a jaw-closed configuration, the influence of 30° variations of the loading direction was negligible. The load distribution capability of the disc appeared to be proportional to its elasticity and was enhanced by the fibrocartilage layers on the a...
Introduction Shoulder arthroscopic surgery is a commonly used technique for visualization, diagno... more Introduction Shoulder arthroscopic surgery is a commonly used technique for visualization, diagnosis and treatment of complications and injuries of the shoulder joint. The treatment is minimally invasive and preferable over open surgery due to significantly shorter recovery and healing time. However, due to the limited arthroscopic view and severe workspace constraints imposed on the surgeon, the procedure requires high skills and experience especially when blood or inflammation blocks the field of view of the arthroscope. Therefore, a novel volumetric image-guided system was developed. This system displays surgical tools relative to the anatomy of the patient during surgery and guides surgeons towards their targeted anatomy. Tonet and co-workers have previously developed a prototype navigation system for the arthroscopic surgery of the knee in which the positions of surgical instruments are tracked in real-time by an optoelectronic localizer [1]. In this navigation system, the surg...
Disclaimer/Complaints regulations If you believe that digital publication of certain material inf... more Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.
While the movability of the human temporomandibular joint is great, the strains and stresses in t... more While the movability of the human temporomandibular joint is great, the strains and stresses in the cartilaginous structures might largely depend on the position of the mandible with respect to the skull. This hypothesis was investigated by means of static three-dimensional finite element simulations involving different habitual condylar positions. Furthermore, the influence of several model parameters was examined by sensitivity analyses. The results indicated that the disc moved together with the condyle in the anterior direction without the presence of ligaments and the lateral pterygoid muscle. By adapting its shape to the changing geometry of the articular surfaces, the disc prevented small contact areas and thus local peak loading. In a jaw-closed configuration, the influence of 30° variations of the loading direction was negligible. The load distribution capability of the disc appeared to be proportional to its elasticity and was enhanced by the fibrocartilage layers on the articular surfaces.
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2007
The general framework and experimental validation of a novel navigation system designed for shoul... more The general framework and experimental validation of a novel navigation system designed for shoulder arthroscopy are presented. The system was designed to improve the surgeon's perception of the three-dimensional space within the human shoulder. Prior to surgery, a surface model of the shoulder was created from computed tomography images. Intraoperatively, optically tracked arthroscopic instruments were calibrated. The surface model was then registered to the patient using tracked freehand ultrasound images taken from predefined landmark regions on the scapula. Three-dimensional models of the surgical instruments were displayed, in real time, relative to the surface model in a user interface. Laboratory experiments revealed only small registration and calibration errors, with minimal time needed to complete the intraoperative tasks.
Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention, 2006
This paper reports on pilot laboratory experiments with a recently proposed surgical procedure fo... more This paper reports on pilot laboratory experiments with a recently proposed surgical procedure for percutaneous screw insertion into fractured scaphoid bones using ultrasound guidance. The experiments were intended to determine the operator variability of the procedure and its performance in comparison with a traditional pinning procedure using fluoroscopy. In the proposed procedure, a three-dimensional surface model is created from pre-operative computed tomography images and intra-operatively registered to the patient using ultrasound images. A graphical interface that communicates with an optical camera tracking the surgical tools, guides the surgeon during the procedure in real time. The results of the experiments revealed non-significant differences between operators for the error in the entry location of the drill hole (p=0.90); however, significant differences for the exit location (p<0.05). Comparison with the traditional pinning procedure shows that the outcome of the re...
ABSTRACT This paper presents a novel graphical user interface developed for a navigation system f... more ABSTRACT This paper presents a novel graphical user interface developed for a navigation system for ultrasound-guided computer-assisted shoulder arthroscopic surgery. The envisioned purpose of the interface is to assist the surgeon in determining the position and orientation of the arthroscopic camera and other surgical tools within the anatomy of the patient. The user interface features real time position tracking of the arthroscopic instruments with an optical tracking system, and visualization of their graphical representations relative to a three-dimensional shoulder surface model of the patient, created from computed tomography images. In addition, the developed graphical interface facilitates fast and user-friendly intra-operative calibration of the arthroscope and the arthroscopic burr, capture and segmentation of ultrasound images, and intra-operative registration. A pilot study simulating the computer-aided shoulder arthroscopic procedure on a shoulder phantom demonstrated the speed, efficiency and ease-of-use of the system.
ABSTRACT This paper presents a novel ultrasound-guided computer system for arthroscopic surgery o... more ABSTRACT This paper presents a novel ultrasound-guided computer system for arthroscopic surgery of the shoulder joint. Intraoperatively, the system tracks and displays the surgical instruments, such as arthroscope and arthroscopic burrs, relative to the anatomy of the patient. The purpose of this system is to improve the surgeon's perception of the three-dimensional space within the anatomy of the patient in which the instruments are manipulated and to provide guidance towards the targeted anatomy. Pre-operatively, computed tomography images of the patient are acquired to construct virtual threedimensional surface models of the shoulder bone structure. Intra-operatively, live ultrasound images of pre-selected regions of the shoulder are captured using an ultrasound probe whose three-dimensional position is tracked by an optical camera. These images are used to register the surface model to the anatomy of the patient in the operating room. An initial alignment is obtained by matching at least three points manually selected on the model to their corresponding points identified on the ultrasound images. The registration is then improved with an iterative closest point or a sequential least squares estimation technique. In the present study the registration results of these techniques are compared. After the registration, surgical instruments are displayed relative to the surface model of the patient on a graphical screen visible to the surgeon. Results of laboratory experiments on a shoulder phantom indicate acceptable registration results and sufficiently fast overall system performance to be applicable in the operating room.
alexandria.tue.nl
Page 1. EXPERIMENTEN MET EN MQDELLIEWING VAN DE RATTENDYNAMOMETER Afstudeer-verslag, nr 95.18 1 M... more Page 1. EXPERIMENTEN MET EN MQDELLIEWING VAN DE RATTENDYNAMOMETER Afstudeer-verslag, nr 95.18 1 Maarten Beek Begeleiders: PHM B ovendeerd MR Drost Afstudeerhoogleraar: JD Janssen Eindhoven, december 1995. Page 2. Page 3. INHOUD ...
Computer aided surgery : official journal of the International Society for Computer Aided Surgery, 2014
This study presents and evaluates a semi-automated algorithm for quantifying malalignment in comp... more This study presents and evaluates a semi-automated algorithm for quantifying malalignment in complex femoral shaft fractures from a single intraoperative cone-beam CT (CBCT) image of the fractured limb. CBCT images were acquired of complex comminuted diaphyseal fractures created in 9 cadaveric femora (27 cases). Scans were segmented using intensity-based thresholding, yielding image stacks of the proximal, distal and comminuted bone. Semi-deformable and rigid affine registrations to an intact femur atlas (synthetic or cadaveric-based) were performed to transform the distal fragment to its neutral alignment. Leg length was calculated from the volume of bone within the comminution fragment. The transformations were compared to the physical input malalignments. Using the synthetic atlas, translations were within 1.71 ± 1.08 mm (medial/lateral) and 2.24 ± 2.11 mm (anterior/posterior). The varus/valgus, flexion/extension and periaxial rotation errors were 3.45 ± 2.6°, 1.86 ± 1.5° and 3.4...
Lecture Notes in Computer Science, 2004
Three-dimensional (3-d) surface models of human carpal bones obtained from Computed Tomography (C... more Three-dimensional (3-d) surface models of human carpal bones obtained from Computed Tomography (CT) were used to investigate their kinematic behavior throughout the entire physiological range of motion of the human wrist joint. The 3-d motion of the bones was visualized graphically by the finite helical axis (FHA) and smooth animations. It was found that extension mainly occurs in the radial-carpal
Journal of dental research, 2001
While the movability of the human temporomandibular joint is great, the strains and stresses in t... more While the movability of the human temporomandibular joint is great, the strains and stresses in the cartilaginous structures might largely depend on the position of the mandible with respect to the skull. This hypothesis was investigated by means of static three-dimensional finite element simulations involving different habitual condylar positions. Furthermore, the influence of several model parameters was examined by sensitivity analyses. The results indicated that the disc moved together with the condyle in the anterior direction without the presence of ligaments and the lateral pterygoid muscle. By adapting its shape to the changing geometry of the articular surfaces, the disc prevented small contact areas and thus local peak loading. In a jaw-closed configuration, the influence of 30 degrees variations of the loading direction was negligible. The load distribution capability of the disc appeared to be proportional to its elasticity and was enhanced by the fibrocartilage layers o...
Computer assisted surgical interventions and research in joint kinematics rely heavily on the acc... more Computer assisted surgical interventions and research in joint kinematics rely heavily on the accurate registration of three-dimensional bone surface models reconstructed from various imaging technologies. Anomalous results were seen in a kinematic study of carpal bones using a principal axes alignment approach for the registration. The study was repeated using an iterative closest point algorithm, which is more accurate, but also more demanding to apply. The principal axes method showed errors between 0.35 mm and 0.49 mm for the scaphoid, and between 0.40 mm and 1.22 mm for the pisiform. The iterative closest point method produced errors of less than 0.4 mm. These results show that while the principal axes method approached the accuracy of the iterative closest point algorithm in asymmetrical bones, there were more pronounced errors in bones with some symmetry. Principal axes registration for carpal bones should be avoided.
A new procedure for percutaneous screw insertion in the scaphoid is proposed. The procedure invol... more A new procedure for percutaneous screw insertion in the scaphoid is proposed. The procedure involves pre-surgery planning using computed tomography imaging and intra-operative guidance using three-dimensional ultrasound. Preoperatively, the desired screw location and orientation is chosen on a three-dimensional surface model generated from computed tomography images. During the surgery, ultrasound images are captured from the targeted anatomy of the patient using an ultrasound probe that is tracked with a Certus optical camera. The tracked probe enables the registration of the surface model and the surgical plan to the patient in the operating room. The surgical drill, used by the surgeon for screw insertion, is also tracked with the optical camera. A graphical user interface has been developed to display the surface model, the surgical plan and the drill in real-time. By means of this interface, the surgeon is guided during the screw insertion procedure. Our experiments on scaphoid phantoms demonstrate that the accuracy of the proposed procedure is potentially of the same order as an open reduction and screw fixation surgery. The advantages of this new procedure are a reduced risk of infections and minimal soft tissue damage due to its percutaneous nature. The procedure also reduces the exposure to ionizing radiation for patients and operating room staff due to the employment of ultrasound imaging instead of fluoroscopy.
Medical Image Analysis, 2008
A new technique for percutaneous fixation of non-displaced scaphoid fractures is described. The t... more A new technique for percutaneous fixation of non-displaced scaphoid fractures is described. The technique used pre-operative planning from computed tomography images, registration to intra-operatively acquired three-dimensional ultrasound images, and intra-operative guidance using an optical tracking system. Two stand-alone software applications were developed. The first one was used to determine the surgical plan pre-operatively and the second one was used to guide the surgeon during screw insertion. Laboratory validation of the technique included measurements of the inter-operator and intra-operator variability in the outcome of scaphoid fixation using the proposed procedure, and also included comparison of the performance of this procedure with the conventional percutaneous fixation technique using fluoroscopy. The results showed that the tight accuracy requirements of percutaneous scaphoid fixation were met and that the consistency was superior to the conventional technique.
Journal of Biomechanics, 2009
A novel computational model of the wrist that predicts carpal bone motion was developed in order ... more A novel computational model of the wrist that predicts carpal bone motion was developed in order to investigate the complex kinematics of the human wrist.
Journal of Dental Research, 2001
The cartilaginous intra-articular disc of the human temporomandibular joint shows clear anteropos... more The cartilaginous intra-articular disc of the human temporomandibular joint shows clear anteroposterior variations in its morphology. However, anteroposterior variations in its tissue behavior have not been investigated thoroughly. To test the hypothesis that the mechanical properties of fresh human temporomandibular joint discs vary in anteroposterior direction, we performed dynamic indentation tests at three anteroposteriorly different locations. The disc showed strong viscoelastic behavior dependent on the amplitude and frequency of the indentation, the location, and time. The resistance against deformations and the shock absorbing capabilities were larger in the intermediate zone than in regions located more anteriorly and posteriorly. Because several studies have predicted that the intermediate zone is the predominantly loaded region of the disc, it can be concluded that the topological variations in its tissue behavior enable the disc to combine the functions of load distribut...
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2007
The general framework and experimental validation of a novel navigation system designed for shoul... more The general framework and experimental validation of a novel navigation system designed for shoulder arthroscopy are presented. The system was designed to improve the surgeon's perception of the three-dimensional space within the human shoulder. Prior to surgery, a surface model of the shoulder was created from computed tomography images. Intraoperatively optically tracked arthroscopic instruments were calibrated. The surface model was then registered to the patient using tracked freehand ultrasound images taken from predefined landmark regions on the scapula. Three-dimensional models of the surgical instruments were displayed, in real time, relative to the surface model in a user interface. Laboratory experiments revealed only small registration and calibration errors, with minimal time needed to complete the intraoperative tasks.
Journal of Dental Research, 2001
While the movability of the human temporomandibular joint is great, the strains and stresses in t... more While the movability of the human temporomandibular joint is great, the strains and stresses in the cartilaginous structures might largely depend on the position of the mandible with respect to the skull. This hypothesis was investigated by means of static three-dimensional finite element simulations involving different habitual condylar positions. Furthermore, the influence of several model parameters was examined by sensitivity analyses. The results indicated that the disc moved together with the condyle in the anterior direction without the presence of ligaments and the lateral pterygoid muscle. By adapting its shape to the changing geometry of the articular surfaces, the disc prevented small contact areas and thus local peak loading. In a jaw-closed configuration, the influence of 30° variations of the loading direction was negligible. The load distribution capability of the disc appeared to be proportional to its elasticity and was enhanced by the fibrocartilage layers on the a...
Introduction Shoulder arthroscopic surgery is a commonly used technique for visualization, diagno... more Introduction Shoulder arthroscopic surgery is a commonly used technique for visualization, diagnosis and treatment of complications and injuries of the shoulder joint. The treatment is minimally invasive and preferable over open surgery due to significantly shorter recovery and healing time. However, due to the limited arthroscopic view and severe workspace constraints imposed on the surgeon, the procedure requires high skills and experience especially when blood or inflammation blocks the field of view of the arthroscope. Therefore, a novel volumetric image-guided system was developed. This system displays surgical tools relative to the anatomy of the patient during surgery and guides surgeons towards their targeted anatomy. Tonet and co-workers have previously developed a prototype navigation system for the arthroscopic surgery of the knee in which the positions of surgical instruments are tracked in real-time by an optoelectronic localizer [1]. In this navigation system, the surg...
Disclaimer/Complaints regulations If you believe that digital publication of certain material inf... more Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.
While the movability of the human temporomandibular joint is great, the strains and stresses in t... more While the movability of the human temporomandibular joint is great, the strains and stresses in the cartilaginous structures might largely depend on the position of the mandible with respect to the skull. This hypothesis was investigated by means of static three-dimensional finite element simulations involving different habitual condylar positions. Furthermore, the influence of several model parameters was examined by sensitivity analyses. The results indicated that the disc moved together with the condyle in the anterior direction without the presence of ligaments and the lateral pterygoid muscle. By adapting its shape to the changing geometry of the articular surfaces, the disc prevented small contact areas and thus local peak loading. In a jaw-closed configuration, the influence of 30° variations of the loading direction was negligible. The load distribution capability of the disc appeared to be proportional to its elasticity and was enhanced by the fibrocartilage layers on the articular surfaces.
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2007
The general framework and experimental validation of a novel navigation system designed for shoul... more The general framework and experimental validation of a novel navigation system designed for shoulder arthroscopy are presented. The system was designed to improve the surgeon's perception of the three-dimensional space within the human shoulder. Prior to surgery, a surface model of the shoulder was created from computed tomography images. Intraoperatively, optically tracked arthroscopic instruments were calibrated. The surface model was then registered to the patient using tracked freehand ultrasound images taken from predefined landmark regions on the scapula. Three-dimensional models of the surgical instruments were displayed, in real time, relative to the surface model in a user interface. Laboratory experiments revealed only small registration and calibration errors, with minimal time needed to complete the intraoperative tasks.
Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention, 2006
This paper reports on pilot laboratory experiments with a recently proposed surgical procedure fo... more This paper reports on pilot laboratory experiments with a recently proposed surgical procedure for percutaneous screw insertion into fractured scaphoid bones using ultrasound guidance. The experiments were intended to determine the operator variability of the procedure and its performance in comparison with a traditional pinning procedure using fluoroscopy. In the proposed procedure, a three-dimensional surface model is created from pre-operative computed tomography images and intra-operatively registered to the patient using ultrasound images. A graphical interface that communicates with an optical camera tracking the surgical tools, guides the surgeon during the procedure in real time. The results of the experiments revealed non-significant differences between operators for the error in the entry location of the drill hole (p=0.90); however, significant differences for the exit location (p<0.05). Comparison with the traditional pinning procedure shows that the outcome of the re...
ABSTRACT This paper presents a novel graphical user interface developed for a navigation system f... more ABSTRACT This paper presents a novel graphical user interface developed for a navigation system for ultrasound-guided computer-assisted shoulder arthroscopic surgery. The envisioned purpose of the interface is to assist the surgeon in determining the position and orientation of the arthroscopic camera and other surgical tools within the anatomy of the patient. The user interface features real time position tracking of the arthroscopic instruments with an optical tracking system, and visualization of their graphical representations relative to a three-dimensional shoulder surface model of the patient, created from computed tomography images. In addition, the developed graphical interface facilitates fast and user-friendly intra-operative calibration of the arthroscope and the arthroscopic burr, capture and segmentation of ultrasound images, and intra-operative registration. A pilot study simulating the computer-aided shoulder arthroscopic procedure on a shoulder phantom demonstrated the speed, efficiency and ease-of-use of the system.
ABSTRACT This paper presents a novel ultrasound-guided computer system for arthroscopic surgery o... more ABSTRACT This paper presents a novel ultrasound-guided computer system for arthroscopic surgery of the shoulder joint. Intraoperatively, the system tracks and displays the surgical instruments, such as arthroscope and arthroscopic burrs, relative to the anatomy of the patient. The purpose of this system is to improve the surgeon's perception of the three-dimensional space within the anatomy of the patient in which the instruments are manipulated and to provide guidance towards the targeted anatomy. Pre-operatively, computed tomography images of the patient are acquired to construct virtual threedimensional surface models of the shoulder bone structure. Intra-operatively, live ultrasound images of pre-selected regions of the shoulder are captured using an ultrasound probe whose three-dimensional position is tracked by an optical camera. These images are used to register the surface model to the anatomy of the patient in the operating room. An initial alignment is obtained by matching at least three points manually selected on the model to their corresponding points identified on the ultrasound images. The registration is then improved with an iterative closest point or a sequential least squares estimation technique. In the present study the registration results of these techniques are compared. After the registration, surgical instruments are displayed relative to the surface model of the patient on a graphical screen visible to the surgeon. Results of laboratory experiments on a shoulder phantom indicate acceptable registration results and sufficiently fast overall system performance to be applicable in the operating room.
alexandria.tue.nl
Page 1. EXPERIMENTEN MET EN MQDELLIEWING VAN DE RATTENDYNAMOMETER Afstudeer-verslag, nr 95.18 1 M... more Page 1. EXPERIMENTEN MET EN MQDELLIEWING VAN DE RATTENDYNAMOMETER Afstudeer-verslag, nr 95.18 1 Maarten Beek Begeleiders: PHM B ovendeerd MR Drost Afstudeerhoogleraar: JD Janssen Eindhoven, december 1995. Page 2. Page 3. INHOUD ...
Computer aided surgery : official journal of the International Society for Computer Aided Surgery, 2014
This study presents and evaluates a semi-automated algorithm for quantifying malalignment in comp... more This study presents and evaluates a semi-automated algorithm for quantifying malalignment in complex femoral shaft fractures from a single intraoperative cone-beam CT (CBCT) image of the fractured limb. CBCT images were acquired of complex comminuted diaphyseal fractures created in 9 cadaveric femora (27 cases). Scans were segmented using intensity-based thresholding, yielding image stacks of the proximal, distal and comminuted bone. Semi-deformable and rigid affine registrations to an intact femur atlas (synthetic or cadaveric-based) were performed to transform the distal fragment to its neutral alignment. Leg length was calculated from the volume of bone within the comminution fragment. The transformations were compared to the physical input malalignments. Using the synthetic atlas, translations were within 1.71 ± 1.08 mm (medial/lateral) and 2.24 ± 2.11 mm (anterior/posterior). The varus/valgus, flexion/extension and periaxial rotation errors were 3.45 ± 2.6°, 1.86 ± 1.5° and 3.4...
Lecture Notes in Computer Science, 2004
Three-dimensional (3-d) surface models of human carpal bones obtained from Computed Tomography (C... more Three-dimensional (3-d) surface models of human carpal bones obtained from Computed Tomography (CT) were used to investigate their kinematic behavior throughout the entire physiological range of motion of the human wrist joint. The 3-d motion of the bones was visualized graphically by the finite helical axis (FHA) and smooth animations. It was found that extension mainly occurs in the radial-carpal
Journal of dental research, 2001
While the movability of the human temporomandibular joint is great, the strains and stresses in t... more While the movability of the human temporomandibular joint is great, the strains and stresses in the cartilaginous structures might largely depend on the position of the mandible with respect to the skull. This hypothesis was investigated by means of static three-dimensional finite element simulations involving different habitual condylar positions. Furthermore, the influence of several model parameters was examined by sensitivity analyses. The results indicated that the disc moved together with the condyle in the anterior direction without the presence of ligaments and the lateral pterygoid muscle. By adapting its shape to the changing geometry of the articular surfaces, the disc prevented small contact areas and thus local peak loading. In a jaw-closed configuration, the influence of 30 degrees variations of the loading direction was negligible. The load distribution capability of the disc appeared to be proportional to its elasticity and was enhanced by the fibrocartilage layers o...
Computer assisted surgical interventions and research in joint kinematics rely heavily on the acc... more Computer assisted surgical interventions and research in joint kinematics rely heavily on the accurate registration of three-dimensional bone surface models reconstructed from various imaging technologies. Anomalous results were seen in a kinematic study of carpal bones using a principal axes alignment approach for the registration. The study was repeated using an iterative closest point algorithm, which is more accurate, but also more demanding to apply. The principal axes method showed errors between 0.35 mm and 0.49 mm for the scaphoid, and between 0.40 mm and 1.22 mm for the pisiform. The iterative closest point method produced errors of less than 0.4 mm. These results show that while the principal axes method approached the accuracy of the iterative closest point algorithm in asymmetrical bones, there were more pronounced errors in bones with some symmetry. Principal axes registration for carpal bones should be avoided.
A new procedure for percutaneous screw insertion in the scaphoid is proposed. The procedure invol... more A new procedure for percutaneous screw insertion in the scaphoid is proposed. The procedure involves pre-surgery planning using computed tomography imaging and intra-operative guidance using three-dimensional ultrasound. Preoperatively, the desired screw location and orientation is chosen on a three-dimensional surface model generated from computed tomography images. During the surgery, ultrasound images are captured from the targeted anatomy of the patient using an ultrasound probe that is tracked with a Certus optical camera. The tracked probe enables the registration of the surface model and the surgical plan to the patient in the operating room. The surgical drill, used by the surgeon for screw insertion, is also tracked with the optical camera. A graphical user interface has been developed to display the surface model, the surgical plan and the drill in real-time. By means of this interface, the surgeon is guided during the screw insertion procedure. Our experiments on scaphoid phantoms demonstrate that the accuracy of the proposed procedure is potentially of the same order as an open reduction and screw fixation surgery. The advantages of this new procedure are a reduced risk of infections and minimal soft tissue damage due to its percutaneous nature. The procedure also reduces the exposure to ionizing radiation for patients and operating room staff due to the employment of ultrasound imaging instead of fluoroscopy.
Medical Image Analysis, 2008
A new technique for percutaneous fixation of non-displaced scaphoid fractures is described. The t... more A new technique for percutaneous fixation of non-displaced scaphoid fractures is described. The technique used pre-operative planning from computed tomography images, registration to intra-operatively acquired three-dimensional ultrasound images, and intra-operative guidance using an optical tracking system. Two stand-alone software applications were developed. The first one was used to determine the surgical plan pre-operatively and the second one was used to guide the surgeon during screw insertion. Laboratory validation of the technique included measurements of the inter-operator and intra-operator variability in the outcome of scaphoid fixation using the proposed procedure, and also included comparison of the performance of this procedure with the conventional percutaneous fixation technique using fluoroscopy. The results showed that the tight accuracy requirements of percutaneous scaphoid fixation were met and that the consistency was superior to the conventional technique.
Journal of Biomechanics, 2009
A novel computational model of the wrist that predicts carpal bone motion was developed in order ... more A novel computational model of the wrist that predicts carpal bone motion was developed in order to investigate the complex kinematics of the human wrist.