Biomedical subjects

M Wehmöller

Publications and source records attributed to M Wehmöller.

23 records · Page 2Linked to original sources

PubMed1997

[CAD/CAM (computer-aided design/computer-aided manufacturing) titanium implants for cranial and craniofacial defect reconstruction].

The reconstruction of craniofacial bone defects with intraoperatively modeled prosthesis restricts the choice of material and its biocompatibility and the prediction of the esthetic result. A prolonged duration of the surgical procedure and an increased stress on the patient are consequences. In contrast, modern industrial CAD/CAM-systems allow the prefabrication of titanium prosthesis: An individual computer-based 3D model of the bony defect is generated after acquisition, transfer and evaluation of helical CT data. Basing on these data the individual prosthesis-shape is designed using freeform surfaces geometries and fabricated by a numerically controlled milling machine. The conical margins of this prosthesis-geometry are generated by the borders of the defect with a minimal gap of 0.25 mm, and the surface contours by considering the non-affected neighbouring contours with a constant thickness of 1.5 mm. Individual osteosynthesis-microplates for fixation are integrated in design and manufacturing if screw-holes cannot be integrated in the thin margins of the implants. The radiological and clinical results of 17 patients after reconstruction of craniofacial bone defects with CAD/CAM titanium implants were good. Complications were not observed.

Adolescent↗

PubMed1995

CAD by processing of computed tomography data and CAM of individually designed prostheses.

In the past an economic fabrication of individual prostheses used in reconstructive cranio-maxillo-facial surgery was not possible due to technical deficiencies. Now, through the consistent use of the most modern computer-based techniques developed in the field of industrial engineering, these costs can be reduced to an economic level. Mathematical freeform surfaces models are first created from helical computed tomography data. These serve as the basis for an efficient and idealized construction of prostheses geometries, and provide control-data for a computerized numerical control-fabrication. In 4 clinical cases this new processing technique has successfully been utilized in the fabrication of individually designed prostheses for the reconstruction of skull defects. The range of opportunities offered is reflected not only in the great variety of possible geometric details, but also in the fact that the prostheses may be manufactured--partly using indirect impression-taking techniques--from 3 different biocompatible materials so far and other applications are likely to turn up.

Computer Simulation↗

PubMed1995

Prefabricated prostheses for the reconstruction of skull defects.

Cranioplasties using intraoperatively modeled prostheses may fail to create harmonic contours with long-term stability. In contrast, preoperative modeling would allow more sophisticated planning of the contour and better preparation of the implant material, if a sufficiently precise model of the defect-site was available. In this respect, computer aided design and manufacturing (CAD/CAM)-techniques based on helical computed tomography (CT) data are successfully used for the prefabrication of prostheses: An individual computer-based 3-dimensional model of the bony defect is generated after acquisition, transfer and evaluation of the CT data; from this freeform surfaces geometry an individual and "idealized" prosthesis-geometry is derived and fabricated by a numerically controlled milling machine using modern industrial CAD/CAM-systems and design software. The margins of this prosthesis-geometry are generated by the borders of the defect and the surface by considering the non-affected neighbouring contours. Cranioplasties in cases of large postsurgical skull defects are presented as the first clinical applications of this new method, which also allows the use of titanium and fabrication of integrated fixation-devices.

Computer Simulation↗

PubMed1995

Reconstruction of craniofacial bone defects with individual alloplastic implants based on CAD/CAM-manipulated CT-data.

Reconstruction of craniofacial bone defects by intraoperative modelling of autogenous or alloplastic materials may cause undesirable results concerning the implant shape or the long-term maintenance of this shape. Furthermore, the use of alloplastic materials to be modelled intraoperatively may result in an inflammatory tissue response. Therefore the question is raised whether CAD/CAM-techniques may be used for the pre-operative geometric modelling of the implant based on helical computed tomography data. A numerically based 3-dimensional model of the skull defect serves as the basis for a freeform-surfaces design of the implant shape, position and thickness, using modelling tools and programmes developed for industrial CAD/CAM. The precise and individual fit of the implant results from generating its margins by the borders of the defect, whereas the implant surface is generated by the geometry of the non-affected neighbouring bone contours. The implant data run a numerically controlled milling machine to fabricate the individual implant. The reconstruction of post-traumatic defects of the forehead, of post-surgical temporal defects after intracranial haemorrhage, and of a parieto-occipital defect due to ablative tumour surgery are presented as the first clinical experiences of this new method.

Adolescent↗

PubMedDate not supplied

Growth and transplantation of a custom vascularised bone graft in a man.

BACKGROUND: A major goal of research in bone transplantation is the ability to avoid creation of secondary bone defects. We aimed to repair an extended mandibular discontinuity defect by growth of a custom bone transplant inside the latissimus dorsi muscle of an adult male patient. METHODS: Three-dimensional computed tomography (CT) scanning and computer-aided design techniques were used to produce an ideal virtual replacement for the mandibular defect. These data were used to create a titanium mesh cage that was filled with bone mineral blocks and infiltrated with 7 mg recombinant human bone morphogenetic protein 7 and 20 mL of the patient's bone marrow. Thus prepared, the transplant was implanted into the latissimus dorsi muscle and 7 weeks later transplanted as a free bone-muscle flap to repair the mandibular defect. FINDINGS: In-vivo skeletal scintigraphy showed bone remodelling and mineralisation inside the mandibular transplant both before and after transplantation. CT provided radiological evidence of new bone formation. Postoperatively, the patient had an improved degree of mastication and was satisfied with the aesthetic outcome of the procedure. INTERPRETATION: Heterotopic bone induction to form a mandibular replacement inside the latissimus dorsi muscle in a human being is possible. This technique allows for a lower operative burden compared with conventional techniques by avoiding creation of a secondary bone defect. It also provides a good three-dimensional outcome.

Activin Receptors, Type I↗