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Biomedical subjects

R Marmulla

Publications and source records attributed to R Marmulla.

11 recordsLinked to original sources
PubMed2000

[Traumatology. Mandibular fractures excluding condylar fractures].

Functionally stable fixation via bicortical osteosynthesis on the one hand, and monocortical non-compression osteosynthesis on the other, are still two competing concepts in treating mandibular fractures. A survey of the literature shows that complicated fractures with severe dislocation of the fragments have the lowest rate of complications after functionally stable fixation, whereas non-complicated fractures without significant dislocation in the distal part of the mandible can be treated successfully via monocortical non-compressive osteosynthesis as well. It seems that pre- and intraoperative parameters can be helpful in describing the character of a mandibular fracture in order to give a differential indication between the two therapeutical concepts. The consideration of only seven parameters, as the mandibular fracture score does, provides many combinations of describing a fracture, so that former studies with their small number of patients make only a rather inaccurate differential indication possible. As long as there is no prospective multi-center study giving a guideline to classify mandibular fractures, the rigid internal fixation via functionally stable osteosynthesis should be preferred in all cases which are not "clear, easy to handle" fractures.

Fracture Fixation, Internal↗
PubMed1999

[New possibilities of temporomandibular joint registration during orthodontic operations].

Repositioning osteotomies in a Le Fort I fashion can affect the position of the TMJ, which cannot be viewed directly during surgery. Using the computer-assisted navigation system SSN (Surgical Segment Navigator), the intraoperative position of the TMJ can be checked and unintentional malpositions can be detected. Positioning of the maxilla after Le Fort I osteotomy was carried out in a conventional fashion. Afterwards, the position of the maxilla was corrected in the same patients using the SSN. In this way, the precision of conventional and SSN-guided positioning of the maxilla and its effect on the TMJ has been compared.

Cephalometry↗
PubMed1999

Surgical planning of computer-assisted repositioning osteotomies.

Repositioning osteotomies are frequently used in orthopedic surgery and traumatology to correct malpositions. Computed tomography (CT), stereolithographic models, and x-rays are used in planning. However, the precision achieved in the planning phase is usually not translated to patients. The Surgical Segment Navigator (SSN) is a navigation system that allows computer-assisted correction of malpositions. It consists of an infrared positioning device, two dynamic reference frames (DRF), an infrared pointer, and an infrared camera. All data are displayed numerically and graphically on the monitor of the SSN workstation. The Laboratory Unit for Computer-Assisted Surgery (LUCAS) is used for planning surgery in the laboratory. LUCAS requires only a native CT scan. A preparatory operation to implant bone markers that will be visible in x-rays and a further planning CT scan showing the bone markers, which were necessary with previous systems, are not required for the LUCAS and SSN system. This significantly reduces the radiation exposure of the patient and the costs of surgical planning. Measuring anatomical landmarks in the surgical site, which is time-consuming and reduces accuracy, is not required with the SSN system because the position of the infrared transmitters is known during surgical planning on the LUCAS workstation. This makes the surgical approach faster and much more precise. The surgical planning data are transferred to the surgical site using a data file and an individual surface pattern that fits the surface of the navigated bone segment. The data file is exported from the LUCAS-workstation to the SSN workstation. The planned spatial displacement of the infrared transmitters is saved in this file. The individual surface pattern carries the infrared transmitters. This pattern is the mechanical interface between infrared transmitters and navigated bone segment. The individual surface pattern can be polymerized directly on a small stereolithographic model of the navigated bone segment. The surface pattern can also be generated as negative form from a CT data set using a computer-assisted design/manufacture system. In summary, LUCAS and SSN allow for the computer-assisted correction of malpositions and positioning of artificial joints and implants. In principle, the systems can be used in all fields of surgery.

Biomechanical Phenomena↗
PubMed1998

[Intraoperative precision of mechanical, electromagnetic, infrared and laser-guided navigation systems in computer-assisted surgery].

Intraoperative precision in computer-assisted surgery depends on the characteristics of a navigation system, the precision of correlation between object and data set, the position, number and fixation of landmarks, and the parameters of the data set. The characteristics of a navigation system, in particular the immanent precision, can be detected by the use of the geometric model and navigation analyzer developed at the University of Regensburg with the support of Carl Zeiss, Germany. The precision of five navigation systems of different types and technology was measured: Viewing Wand (ISG, mechanical system), the SMN microscope (Carl Zeiss, infrared system with laser autofocus), the MKM system (Carl Zeiss, robot platform with laser autofocus) and the STP pointer (Leibinger, infrared system). The immanent precision of these systems ranges from 0.1 to 2.0 mm. An electromagnetic system (3-Space Digitizer, Polhemus) was compared; this produces serious spherical deviations of 10.0 to 20.0 mm in the presence of metal, surgical and rotating instruments, and circuits. The application of these different systems for craniomaxillofacial surgery is discussed.

Computer Systems↗
PubMed1998

[Comparative accuracy assessment between a mechanical (viewing wand) and a laser-controlled microscopic positioning system using a geometric test model].

The precision of a new laser-guided navigation system (the "MKM") was compared with the "Viewing Wand" mechanical navigation system. We describe the inherent deviations in each positioning system as well as errors caused by data acquisition and referencing between the CT data set used for navigation and the original object. Two thousand individual measurements were performed on geometric test models scanned by CT. The technical accuracy of the mechanical navigation system varied between 0.48 mm in the most favorable area of the working field and 1.8 mm in the more inaccurate areas. For the laser-guided system a precision of 0.27 mm was found for all areas of the working field. After referencing between the CT data set and the original object, the error of measurement increased in both navigation systems: i.e., 0.83 mm for the Viewing Wand and 0.49 mm for the MKM system.

Equipment Design↗
PubMed1998

Computer-assisted bone segment navigation.

Computer-assisted bone segment navigation is defined as the precise 3-D positioning of geometrically mapped and mathematically described skeletal segments. These bone segments are osteotomized, fractured or prefabricated according to a surgical plan. The high-precision positioning should have an accuracy of 1 mm or better. Segment navigation should be prepared with plain computed tomography (CT) without the implantation of registration markers before CT in order to reduce the number of CTs and operations. The Surgical Segment Navigator (SSN) was developed at the University of Regensburg with the support of Carl Zeiss. This is the first system to meet these criteria. The SSN is based on an infrared positioning device which is connected to a Hewlett Packard LD Pro Workstation. Infrared transmitters are connected to individual templates which are fixed to the bone segment by osteosynthesis screws. Intraoperative correlation between surgical planning and surgical site is achieved by use of a surface-pattern of the bone segment which fits equally well to the laboratory model and the conditions encountered in the patient. The concept of the SSN was submitted by Carl Zeiss as German Patent DE 19747427 A1 in 1997. The SSN system presented here has already been applied clinically and its precision has been evaluated by bone segment navigation in human cadavers.

Bone and Bones↗
PubMed1998

[A new computer-aided surgical approach for reconstruction of the orbit].

BACKGROUND: Complex posttraumatic malpositions of the orbital walls require repositioning osteotomy. Computer tomography, stereolithography models and tele-X-rays are used in planning. However, the precision achieved in the planning phase could not so far be translated to patients (1). The Surgical Segment Navigator SSN is the first highly precise computer-assisted system to transfer laboratory planning data concerning the repositioning osteotomy of orbital walls to a surgical site. MATERIALS AND METHODS: The SSN is based on infrared technology such as the Surgical Tool Navigator STN and the Surgical Microscope Navigator SMN manufactured by Carl Zeiss. Laboratory planning data are transferred to the surgical site by measurements with infrared transmitters which are checked by an infrared camera. RESULTS: A surgical planning can be carried out exactly using the Surgical Segment Navigator. Moreover, the SSN displays hidden levels of an extensive bone segment which are not visible via a bicoronary approach (e.g. orbital floor and facial wall of the maxillary sinus) clearly on monitor and helps to navigate the complete segment. CONCLUSIONS: The Surgical Segment Navigator is the first computer-assisted system for highly precise repositioning osteotomy of the orbital walls.

Female↗
PubMed1998

[Precision control of the position of the bone segments during surgical navigation].

The Surgical Segment Navigator (SSN) which has been developed together with Carl Zeiss at the department for craniomaxillofacial surgery at the University of Regensburg, is the first system for highly precise positioning of bone segments. Before clinical application, the precision of the SSN was evaluated by navigation of cadaver bone segments which is presented in this paper. The SSN tracks intraoperatively bone segments and displays the osteotomied segments on a monitor of the SSN-workstation. All movements are documented and saved within a computer file. Thus, the SSN makes the quality assurance of intraoperative positioning of bone segments possible.

Cadaver↗
PubMed1997

Inherent precision of mechanical, infrared and laser-guided navigation systems for computer-assisted surgery.

This investigation detects the inherent precision of four navigation systems, of different structural type, for computer-assisted surgery, ranging from 0.1 to 1.8 mm: the Viewing Wand with a mechanical arm, and three new systems, the SMN microscope and STP pointer with infrared technology and the MKM system with laser autofocus. For this purpose, a new standard to detect separately the inherent deviations of navigation systems from the deviations caused by acquisition of CT data sets, is introduced. The measurements are performed within a complete three-dimensional room, consisting of three orthogonal planes of a geometric model. The method introduced is valid for regular measurements of the inherent precision of navigation systems for quality assurance in order to prevent intraoperative failure caused by insufficient potentiometers, infrared transmitters or receivers.

Computer Systems↗
PubMed1997

[Precision of computer-assisted systems in profile reconstructive interventions on the face].

In this investigation we compared the precision of different computer-aided systems for positioning osteotomized segments to reconstruct craniofacial asymmetries. The accuracy of a mechanical navigation system, a laser-guided navigation system and the precision of templates moulded on stereolithographic models are compared, using measurements on geometrical objects, anatomical specimens and clinical application. The precision of a mechanical navigation system is 0.5 mm, and a laser-guided system 0.3 mm. The accuracy of a computer and template guided application is 1 mm.

Data Collection↗