Biomedical subjects

Hannes Bleuler

Publications and source records attributed to Hannes Bleuler.

6 recordsLinked to original sources

PubMed2006

Ligament balancing in TKA: evaluation of a force-sensing device and the influence of patellar eversion and ligament release.

Ligament balancing in total knee arthroplasty may have an important influence on joint stability and prosthesis lifetime. In order to provide quantitative information and assistance during ligament balancing, a device that intraoperatively measures knee joint forces and moments was developed. Its performance and surgical advantages were evaluated on six cadaver specimens mounted on a knee joint loading apparatus allowing unconstrained knee motion as well as compression and varus-valgus loading. Four different experiments were performed on each specimen. (1) Knee joints were axially loaded. Comparison between applied and measured compressive forces demonstrated the accuracy and reliability of in situ measurements (1.8N). (2) Assessment of knee stability based on condyle contact forces or varus-valgus moments were compared to the current surgical method (difference of varus-valgus loads causing condyle lift-off). The force-based approach was equivalent to the surgical method while the moment-based, which is considered optimal, showed a tendency of lateral imbalance. (3) To estimate the importance of keeping the patella in its anatomical position during imbalance assessment, the effect of patellar eversion on the mediolateral distribution of tibiofemoral contact forces was measured. One fourth of the contact force induced by the patellar load was shifted to the lateral compartment. (4) The effect of minor and major medial collateral ligament releases was biomechanically quantified. On average, the medial contact force was reduced by 20% and 46%, respectively. Large variation among specimens reflected the difficulty of ligament release and the need for intraoperative force monitoring. This series of experiments thus demonstrated the device's potential to improve ligament balancing and survivorship of total knee arthroplasty.

Aged↗

PubMed2006

Highly-realistic, immersive training environment for hysteroscopy.

The primary driving application of our current research is the development of a generic surgical training simulator for hysteroscopy. A key target is to go beyond rehearsal of basic manipulative skills, and enable training of procedural skills like decision making and problem solving. In this respect, the sense of presence plays an important role in the achievable training effect. To enable user immersion into the training environment, the surrounding and interaction metaphors should be the same as during the real intervention. To this end, we replicated an OR in our lab, provided standard hysteroscopic tools for interaction, and generate a new virtual scene for every session. In this setting, the training starts, as soon as the trainees enter the OR, and ends when they leave the room.

Competency-Based Education↗

PubMed2006

A haptic device for guide wire in interventional radiology procedures.

Interventional Radiology (IR) is a minimally invasive procedure where thin tubular instruments, guide wires and catheters, are steered through the patient's vascular system under X-ray imaging. In order to perform these procedures, a radiologist has to be trained to master hand-eye coordination, instrument manipulation and procedure protocols. The existing simulation systems all have major drawbacks: the use of modified instruments, unrealistic insertion lengths, high inertia of the haptic device that creates a noticeably degraded dynamic behavior or excessive friction that is not properly compensated for. In this paper we propose a quality training environment dedicated to IR. The system is composed of a virtual reality (VR) simulation of the patient's anatomy linked to a robotic interface providing haptic force feedback. This paper focuses on the requirements, design and prototyping of a specific haptic interface for guide wires.

Catheterization↗

PubMed2005

Development of a force amplitude- and location-sensing device designed to improve the ligament balancing procedure in TKA.

To improve the ligament balancing procedure during total knee arthroplasty a force-sensing device to intraoperatively measure knee joint forces and moments has been developed. It consists of two sensitive plates, one for each condyle, a tibial base plate and a set of spaces to adapt the device thickness to the patient-specific tibiofemoral gap. Each sensitive plate is equipped with three deformable bridges instrumented with thick-film piezoresistive sensors, which allow accurate measurements of the amplitude and location of the tibiofemoral contact forces. The net varus-valgus moment is then computed to characterize the ligamentous imbalance. The developed device has a measurement range of 0-500 N and an intrinsic accuracy of 0.5% full scale. Experimental trials on a plastic knee joint model and on a cadaver specimen demonstrated the proper function of the device in situ. The results obtained indicated that the novel force-sensing device has an appropriate range of measurement and a strong potential to offer useful quantitative information and effective assistance during the ligament balancing procedure in total knee arthroplasty.

Arthroplasty, Replacement, Knee↗

PubMed2005

Real-time haptic interface for VR colonoscopy simulation.

Colonoscopy is an endoscopic medical procedure where the colon of the patient is examined. This minimally invasive technique is performed with a colonoscope, a long tube with an integrated imaging device at its tip. The doctors performing these procedures require high skills in multiple domains such as hand-eye coordination, visualization, safety and ease at guiding flexible endoscopes. The importance of training colonoscopy procedures rises with the growth of variety of colon diseases. In order to safely train surgeons to these procedures, a computer-assisted haptic simulator is proposed. This paper describes both the haptic hardware interface and virtual reality software that compose the training system. A high friction belt is used to render the required forces and to insure the absence of slippage. A differential drive actuated with two DC motors enables to set the system into translation and rotation. A virtual reality environment has been developed to provide real-time visualisation and force feedback.

Colonoscopy↗

PubMed2005

A real-time haptic interface for interventional radiology procedures.

Interventional Radiology (IR) is a minimally-invasive surgery technique (MIS) where guidewires and catheters are steered in the vascular system under X-ray imaging. In order to perform these procedures, a radiologist has to be correctly trained to master hand-eye coordination, instrument manipulation and procedure protocols. This paper proposes a computer-assisted training environment dedicated to IR. The system is composed of a virtual reality (VR) simulation of the anatomy of the patient linked to a robotic interface providing haptic force feedback.The paper focuses on the requirements, design and prototyping of a specific part of the haptic interface dedicated to catheters. Translational tracking and force feedback on the catheter is provided by two cylinders forming a friction drive arrangement. The whole friction can be set in rotation with an additional motor providing torque feedback. A force and a torque sensor are integrated in the cylinders for direct measurement on the catheter enabling disturbance cancellation with a close-loop force control strategy.

Humans↗