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H Niederdellmann

Publications and source records attributed to H Niederdellmann.

At least 19 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

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↗
PubMed1999

Prediction of soft tissue profiles in orthodontic surgery with the Dentofacial Planner.

Since the early 1990s, there have been continuous improvements in the software available for planning orthognathic surgery. This study investigates the precision of profile prediction by version 1.51 of the Dentofacial Planner (DFP). Orthognathic operations in 40 patients with different types of dysgnathia were evaluated. The preoperative and postoperative lateral cephalograms were analyzed in the DFP. The computer profiles were simulated on the basis of the skeletal alterations of the jaws observed postoperatively. The predicted soft tissue profiles were compared with the postoperative profile lines and evaluated statistically. The quality of the soft tissue prediction varied from one profile region to another. Significant differences were shown in various operation categories. Appreciable prediction errors were observed in the lip region. In particular, the upper lip revealed inadequate protrusion in bimaxillary operations. The smallest number of significant errors was found in single-jaw operations on the mandible. Significant features were not shown in the chin prediction profile, especially caudal to the superior labiomental furrow. The DFP version tested in the investigation shows some improvements in the convenience of the application compared to the previous versions. The profile prognosis is satisfactory, even in complicated bimaxillary operations. Results continue to be unsatisfactory in the lip profile prognosis. Further development of the software is necessary.

Computer Graphics↗
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

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

[Immunocytochemical venous blood studies in patients with manifest oral cavity carcinomas, oral precancerous conditions, benign tumors and in chronic alcoholic patients].

In a prospective pilot study we investigated the percentage of immunocompetent cells in the peripheral blood in 146 patients (lymphocytes, leucocytes, monocytes, T cells, B cells, NK cells, T-helper cells, T-suppressor cells, ratio T-helper/T-suppressor cells, activated T cells HLA-DR) by flow cytometry. The immunologic parameters were derived from patients with oral and oropharyngeal squamous cell carcinomas, precancerous lesions and benign tumours and from a group of heavy smokers and alcoholics. Carcinoma patients (n = 46) were compared with risk groups and a reference group consisting of patients with inflammatory disease. Within the collective of carcinoma patients we measured the immune status before and after chemo-, radio- and operative therapy. We also analysed the immune parameters in relation to clinical and histomorphological parameters (TNM status, grading). The univariate analysis of monocytes showed significant relationships between on the one hand carcinoma patients and on the other alcoholics and those with benign tumours and precancerous lesions. In precancerous lesions NK cells were significantly increased compared with alcoholics and the reference group. A significant decrease in B cells in carcinoma patients may show incipient insufficiency of the humoral immunity. The immune parameters showed a different reaction depending on therapy. After irradiation we found a significant increase of T-suppressor cytotoxic cells and decreases in B and T-helper cells. Chemotherapy showed an increase in T and T-helper cells and a decrease in B cells. Surgical therapy alone yielded an increase in B cells. The comparison of all pre- and posttherapeutic parameters showed significant changes only in activated T cells HLA-DR. We found no correlation between prognostic clinico-pathological factors and immune parameters. No changes were found in a multivariate analysis.

Alcoholism↗
PubMed1997

Conservative or radical treatment of keratocysts: a retrospective review.

The paper reports our experience in the treatment of keratocysts and make recommendations for treatment in the form of a retrospective study. Thirty-eight patients with 52 keratocysts out of a total of 318 patients with 351 odontogenic cysts who presented between 1984 and 1992 were analysed. Outcome was measured by recurrence and there were three recurrences (6%) which compares favourably with published reports in which figures of up to 62% have been quoted. Based on the experience of others as well as our own series we recommend that small cysts near the alveolar process should be treated by simple excision, but large invasive cysts near the base of the skull should be treated by radical resection leaving a margin of normal tissue around the specimen. If any variables are discovered that can reliably indicate prognosis we may be able to revise these recommendations.

Adolescent↗
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

Pigmented peripheral nerve sheath tumor of the oral cavity with expression of AP-2 beta and c-RET: a case report.

Pigmented peripheral nerve sheath tumor of the oral cavity is a rare lesion and may be difficult to distinguish clinically from true melanocytic tumors. We report a case of pigmented peripheral nerve sheath tumor with a high degree of melanocytic differentiation and describe its histologic and ultrastructural features. Immunohistochemistry and polymerase chain reaction findings support the neural crest origin of the tumor. The clinical course of our case indicates that local recurrence may be a significant problem in pigmented peripheral nerve sheath tumor.

Adult↗
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↗
PubMed1996

[Single lag screw osteosynthesis for management of mandibular angle fractures].

80 patients with 83 fractures of the mandibular angle were treated by lag screw fixation. The screws were placed through a transoral incision with transbuccal trochar instrumentation. No maxillomandibular fixation was used. Complications occurred in 12 fractures (14%), of which 5 (6%) required secondary surgical intervention. In all cases bony union was achieved 6 months postoperatively. Indications and advantages of the technique are discussed.

Adult↗
PubMed1995

Long-term results after primary restoration of the orbital floor.

It has been possible to follow-up 74 (54%) of the 137 patients who were treated for orbital floor fractures in our clinic between 1988 and 1992. The minimum observation time was 12 months. The results of the orbital reconstruction were analysed on the basis of the postoperative findings and the advantages of access via a central lower lid incision and the use of allogenic dura mater, were evaluated on the basis of the functional results. The biocompatibility, stability and ready availability of allogenic dura mater all support its use in orbital floor restoration. Nevertheless, the potential problems of CJD transmission are discussed.

Adolescent↗
PubMed1995

Comparative study of results of electronic axiography with results of magnetic resonance imaging including MRI-assisted splint therapy.

The most common temporomandibular joint disturbance is the internal derangement. Its prevalence has been shown to be as high as 28%. The purpose of this study was on one hand to compare the diagnostic efficiency of an electronic axiographic system with magnetic resonance imaging, and, on the other hand to evaluate the results of MRI-assisted treatment monitoring of occlusal splint therapy. The results of this survey clearly show that in evaluation of temporomandibular joint disorders, electronic axiography and magnetic resonance imaging should be used in conjunction with one another to increase the accuracy of positive and differentiated diagnoses. The medical concept of disc recapture involving the use of occlusal splints seems to be merely a clinical term which is not necessarily hinged on anatomical intraarticular changes.

Adult↗
PubMed1995

[Involvement of the trigeminal nerve in fractures of the face].

It is an anatomical particularity of the trigeminal nerve that his three main branches evolve in its peripheral section via a relatively long passage up to an osseous canal. We have tried to provide, apart from a quantitative and qualitative analysis of the lesions of the trigeminal nerve in case of facial fractures, a statement as to their topography in order to enable prognosis as to such lesions. For the study, we used the data of 328 patients with a total of 468 fractures. All patients were asked to provide detailed information about any pre- and postoperative loss of sensibility in the area of the trigeminal nerve. The analysis of the research results allowed indeed for a quantitative statement, not a qualitative one, however. We were able to establish an interrelationship between the topography and a persistent lesion of the nerve for the maxilla and the mandible.

Cranial Nerve Diseases↗
PubMed1995

High-resolution SPECT of the temporomandibular joint in chronic craniofacial pain disorders: a pilot study.

Chronic craniofacial pain disorders commonly cause physicians diagnostic difficulties. The purpose of this study was, on one hand, to detect pathological focuses of the craniofacial skeleton using a new system of high-resolution single photon emission computertomography (SPECT), and on the other hand, to compare the results with those obtained via high-field magnetic resonance imaging (MRI) as far as temporomandibular joint affections are concerned. SPECT can be regarded as a supplementary diagnostic mean for patients displaying the symptoms of chronic craniofacial pain disorders, especially in cases where clinical and paraclinical investigations do not coïncide or which are refractory to treatment, not least to differentiate between somatic and psychogenic causes, respectively.

Adult↗