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Biomedical subjects

Tim Lueth

Publications and source records attributed to Tim Lueth.

6 recordsLinked to original sources
PubMed2005

A spine frame for intra-operative fixation to increase accuracy in spinal navigation and robotics.

OBJECTIVE: Intra-operative movements due to mechanical ventilation or manipulations are a limiting factor for accurate spinal navigation or robotic-assisted spinal surgery. The purpose of this study was to assess the accuracy of an intra-operative spinal fixation device in an experimental setup. MATERIALS AND METHODS: We developed a fixation device, attached to the operating table, that combines soft tissue retraction with spinal process fixation. Using a lumbar spine cadaver, tightness of fixation was evaluated using two measurement systems. Accuracy measurements using changes in spatial co-ordinates of implanted reference markers were performed in three segments, following different manipulations of the spine. In addition, for intra-operative movements of the spine during mechanical ventilation, the range of motion was determined in 10 patients during lumbar interbody fusion. RESULTS: The spine frame was easy to use and did not restrict screw insertion. Mean deviations of the markers' in all segments were measured at between 0.35 and 0.8 mm, following pedicle screw insertion and lateral traction. Intra-operative range of motion of the spine was measured with a mean value of 8.7 +/- 3.3 mm. CONCLUSION: Using our spine frame, a rigid fixation following manipulation of the spine was demonstrated. By overcoming the intra-operative movement-dependent inaccuracy, safety in navigated spine surgery and robotic-assisted procedures might be improved.

Analysis of Variance↗
PubMed2002

A system for simulation and monitoring of robot-assisted and navigation-assisted surgical interventions. (Part 1).

Location monitoring systems for surgical applications are getting more and more common in clinical daily life. Navigation treatment systems are also a form of a location monitoring system. These systems always consist of an optical, US-, electromagnetic or mechanical navigation system. If two or more navigation systems are combined or one navigations system is combined with a robot system the kinematic model of the entire system consists of closed kinematic loops. In this paper, an approach is presented to gain more information from the closed kinematic chains instead of breaking the kinematic loops.

Biomechanical Phenomena↗
PubMed2002

A new approach for modelling kinematic dependencies for monitoring locations of objects in closed kinematic chains. (Part 2).

Location monitoring systems for surgical applications are getting more and more common in clinical daily life. Navigation treatment systems are also a form of a location monitoring system. These systems always consist of an optical, US-, electromagnetic or mechanical navigation system. If two or more navigation systems are combined or one navigations system is combined with a robot system the kinematic model of the entire system consists of closed kinematic loops. In this paper, an approach is presented to gain more information from the closed kinematic chains instead of breaking the kinematic loops. This is the second part of [1].

Algorithms↗
PubMedDate not supplied

Application of stereolithography for scaffold fabrication for tissue engineered heart valves.

A crucial factor in tissue engineering of heart valves is the functional and physiologic scaffold design. In our current experiment, we describe a new fabrication technique for heart valve scaffolds, derived from x-ray computed tomography data linked to the rapid prototyping technique of stereolithography. To recreate the complex anatomic structure of a human pulmonary and aortic homograft, we have used stereolithographic models derived from x-ray computed tomography and specific software (CP, Aachen, Germany). These stereolithographic models were used to generate biocompatible and biodegradable heart valve scaffolds by a thermal processing technique. The scaffold forming polymer was a thermoplastic elastomer, a poly-4-hydroxybutyrate (P4HB) and a polyhydroxyoctanoate (PHOH) (Tepha, Inc., Cambridge, MA). We fabricated one human aortic root scaffold and one pulmonary heart valve scaffold. Analysis of the heart valve included functional testing in a pulsatile bioreactor under subphysiological and supraphysiological flow and pressure conditions. Using stereolithography, we were able to fabricate plastic models with accurate anatomy of a human valvular homograft. Moreover, we fabricated heart valve scaffolds with a physiologic valve design, which included the sinus of Valsalva, and that resembled our reconstructed aortic root and pulmonary valve. One advantage of P4HB and PHOH was the ability to mold a complete trileaflet heart valve scaffold from a stereolithographic model without the need for suturing. The heart valves were tested in a pulsatile bioreactor, and it was noted that the leaflets opened and closed synchronously under subphysiological and supraphysiological flow conditions. Our preliminary results suggest that the reproduction of complex anatomic structures by rapid prototyping techniques may be useful to fabricate custom made polymeric scaffolds for the tissue engineering of heart valves.

Bioprosthesis↗
PubMedDate not supplied

Robot-assisted placement of craniofacial implants.

PURPOSE: The purpose of this study was to improve and accelerate the rehabilitation process for patients with severe ear microtia with an implant-anchored auricular prosthesis. A medically approved robot system was used to place the craniofacial implants and a new process was developed for preoperative fabrication of the prosthesis using a rapid prototyping technique. MATERIALS AND METHODS: Preoperatively, after computerized tomography, the implant positions were determined in a planning tool according to bone availability and esthetic considerations. Intraoperatively, the robot showed the surgeon the planned implant positions and guided the placement procedure. RESULTS: The accuracy measurements showed that with this robot system, absolute implant position accuracy of approximately -0.5 +/- 0.4 mm, a relative accuracy between the implants of approximately 0.2 +/- 0.5 mm, and a deviation from the parallel position of approximately 0.6 +/- 0.5 degrees were achieved. Thirty implants were placed in 13 patients with robot assistance with no intraoperative injuries. DISCUSSION: This technique made it possible to apply the preoperatively fabricated auricular prosthesis directly after surgery. CONCLUSION: From this experience it can be concluded that the robot system and the new manufacturing concept for anaplastology can be applied advantageously in other areas of the head as well.

Adolescent↗