Biomedical subjects

R Ewers

Publications and source records attributed to R Ewers.

At least 37 records · Page 2Linked to original sources

PubMed2000

[Telenavigation and expert consultation using a stereotaxic surgical videoserver].

The exponential increase of medical information creates a need for new methods in the visualization of medical imaging modalities for diagnosis and therapy. In this sense, visualization includes the display of medical image data and image-guided stereotaxic navigation as well as the advice of an expert. The Artma Virtual Patient System enables a remote expert to observe the surgical procedure via the Internet and interactively modify the interoperative visualization from the remote location. The expert in the remote location receives the planning data almost in real time over TCP/IP from a stereotaxic videoserver. In addition to live video streaming, stereotaxic navigation data are sent over the network as rigid body coordinates. The expert modifies the surgical simulation on the remote computer and the modified operating plan is sent back to the operating site. By teleconsulting, the composite images and overlapping graphics--instruments, target structures, landmarks, contour--can be seen in affiliated clinics with the possibility of interactive graphical assistance. With this image fusion technology the knowledge of a remote expert is included in virtual data structures and visualized by the overlay with live video data (augmented reality) in real time during surgery.

Humans↗

PubMed2000

Application of the buccal fat pad in oral reconstruction.

PURPOSE: This report evaluates the use of the buccal fat pad in reconstruction of defects of the hard and soft palate. PATIENTS AND METHODS: Twenty-nine patients with different indications (oroantral fistula, tumor of the hard and soft palate, posterior fistula in cleft patients, covering of bone transplants in augmentation procedure) were treated with a pedicled buccal fat pad without lining. The maximum reconstructed defect was 5.5 x 4 cm. RESULTS: All inserted fat grafts healed well without any aesthetic disturbances. The surface of the fat converted to normal mucosa. CONCLUSIONS: Use of the buccal fat pad is a safe and easy method to reconstruct defects in the posterior maxilla and soft palate. Good vascularization, ease of access, and minimal donor site morbidity make it a reliable soft tissue graft.

Adipose Tissue↗

PubMed2000

Guided bone regeneration with titanium membranes: a clinical study.

Guided bone regeneration using barrier membranes is useful in bone augmentation. Because the commonly used polytetrafluoroethylene (PTFE, Gore-Tex (R), WL Gore, Flagstaff, AZ, USA) membranes or resorbable membranes tend to collapse, more stable membranes are desirable. A titanium membrane (FRIOS(R) BoneShield, Friatec, Mannheim, Germany) was evaluated in a clinical study of 52 patients. Most of them had particulate bone grafts or phycogene hydroxyapatite (Algipore(R), Friatec, Mannheim, Germany) or both stabilized with titanium membranes. In 78 procedures, 23 membranes (29%) became exposed, but only seven of these (9%) led to failure of the graft with a considerable loss of augmented material. The time interval between operation and possibly exposure was responsible for the result. Early exposures (within a few weeks) led to poor formation of new bone within the grafts, whereas if exposure was later, results were as good as in procedures in which the membranes did not become exposed.

Adult↗

PubMed2000

The L-shaped osteotomy for vertical callus distraction in the molar region of the mandible: a technical note.

The following report refers to a well described surgical procedure using a prototype vertical distractor developed in Cologne in cooperation with Martin Medizintechnik GmbH. The surgical technique has been refined by an L-shaped osteotomy stabilized posteriorly by a miniplate to limit the amount of callus regeneration in the molar region where no increase in vertical height is required. The surgical technique with its advantages and one complication is described as used in four patients undergoing six distraction treatments.

Adult↗

PubMed2000

MRI-based stereolithographic models of the temporomandibular joint: technical innovation.

A new technique of manufacturing dual-colour stereolithographic models of hard and soft tissues of the temporomandibular joint (TMJ) is presented. Sagittal T1/PD weighted magnetic resonance (MR) images of joints with and without disc displacement were obtained in the closed and open mouth positions. Individual interactive contour identification of bony structures and the articular disc followed by binary interpolation provided the data for the generation of acrylic TMJ models. Three dimensional in vivo visualization of the articular disc in relation to bony structures in the closed and open mouth positions allows a new perception of normal and pathological TMJ anatomy.

Acrylic Resins↗

PubMed2000

Transcaruncular approach for reconstruction of medial orbital wall fracture.

Medial orbital wall fractures can cause horizontal diplopia and enophthalmos. Therefore, reconstruction of displaced medial wall fractures should be considered. We used a transcaruncular approach in five male patients to reconstruct the medial orbital wall after acute injuries and also as a secondary procedure for enophthalmos correction. Four of these patients had a concomitant orbital floor fracture. The incision was made in the caruncule and extended in the conjunctiva superior and inferior into the fornices for 10-12 mm. The tissue was bluntly dissected in an anteroposterior direction. The periosteum was incised dorsal of the posterior lacrimal crest and after elevation of the periosteum, the fractured orbital wall was visible. Transplants up to a height of 2 cm could be inserted for reconstruction of the medial orbital wall. In the cases of acute trauma, the medial wall was reconstructed using a resorbable polydioxanone plate. Cortical bone was used for the reconstruction of late enophthalmos. No postoperative complications were found. The transcaruncular approach gave a rapid entry to the fractured medial orbital wall without a visible scar.

Adult↗

PubMed1999

[Distraction osteogenesis with a fully implantable system. Experimental study].

Distraction osteogenesis using external or intraoral devices is an established method for lengthening the human mandible. In this preliminary study on sheep, a completely implanted device for mandibular lengthening is presented. After osteotomy of the mandible, the electromechanical device was fixed to the mandible and the power and control unit were inserted subcutaneously in the neck region. After a healing period of 5 days, the device was activated magnetically and allowed calibrated distraction steps of 0.04 mm/h, achieving a total of 1.0 mm per day. With this method, it was possible to lengthen the mandible automatically over a period of 14 days without transmucosal activation. In our study, this newly designed internal device was successfully used for distraction osteogenesis, and a maximum mandibular lengthening of 13.6 mm was achieved. Further research is necessary to achieve progression to human clinical application in the near future.

Animals↗

PubMed1999

[Horse shoe Le Fort I osteotomy. Surgical technique for reconstruction of the extremely atrophied maxilla].

Twenty-three patients with class VI atrophy of the maxilla were treated with horseshoe Le Fort I osteotomy. In ten patients, simultaneous placement of the implants was carried out, and in 12 the implantation was done in a second procedure 6-9 months later. A total of 178 implants were placed, and 15 were lost. In one patient, five implants were lost due to an oronasal fistula, leading to loss of part of the bone graft. The implant survival rate for all the implants was 89.0-88.2% in the one-step procedure and 90.0% in the two-step procedure. There was no difference between the one-step and the two-step procedure with respect to the peri-implant soft tissues in follow-up of least 2 years after implantation. We favor the two-step procedure because it allows more precise positioning of implants.

Adult↗

PubMed1999

[Minimally invasive sinus lift. Limits and possibilities in the atrophic maxilla].

The minimal invasive sinus lift is a procedure done by osteotome technique via a crestal approach in contrast to the sinus elevation via lateral osteotomy to achieve adequate bone-height for setting of implants. The purpose of this anatomical and clinical study was to evaluate by endoscopic control if the minimal sinus lift is practicable by a residual bone height of less than 8 mm without mucosal damage. An endoscopic controlled sinus lift was done on 10 fresh cadavers. The original bone height was 3-6 mm in the lateral maxilla. The sinus mucosa was elevated by an osteotome at least up to 10 mm. A sinus augmentation was performed with a bone substitute material (Algipore) over the implant bed. There was no tear visible on endoscopic control. Finally, the maxilla was removed and the mucosa inspected. No laceration of the mucosa was found in any case. The clinical study included 7 patients. 5 Patients had bone condensation, augmentation of bone and implantation of 13 mm implants in a one stage procedure. The originally bone height was between 6-8 mm in all patients. One of the five patients did show a small perforation of the mucosa during mucosal elevation at one implant-bed. The implant was inserted and an endoscopic control after 6 weeks showed regular mucosa. 2 patients received augmentation only at a primary bone height of only 3-5 mm. A post-operative CT-scan showed that the bone height was augmented to a total height of 13-16 mm. As a result of our study a sufficient bone height can be achieved by the minimal invasive sinus lift procedure. The advantage of this crestal approach is the protection of the intraosseous vessels in the maxilla and less postoperative morbidity. As a disadvantage, the insertion of bone material limited only to the area surrounding the implant bed, might be discussed.

Aged↗

PubMed1999

Clinical experience with interactive teleconsultation and teleassistance in craniomaxillofacial surgical procedures.

PURPOSE: The objective of this study was to evaluate the clinical value and feasibility of surgical telenavigation and teleassistance technology in the field of craniomaxillofacial surgery. MATERIALS AND METHODS: The technology is based on the principles of augmented reality environment technology and remote stereotactic visualization. A consultant surgeon in a remote location receives video, audio, and stereotactic navigation data from the operation site almost in real-time and, using a head-mounted display, is emerged in the surgical augmented reality environment. By telepresence or teleconsultation, the composite images and superimposed graphics (instruments, target structures, landmarks, contours) can be seen and discussed in connected clinics with the possibility of interactive manipulation and assistance. RESULTS: Interactive teleassistance was used in 27 cases of various types craniomaxillofacial surgery. The principles of computer-aided telenavigation were applied successfully. Technical problems in 6 cases did not cause a breakdown of overall system performance. CONCLUSION: Teleconsultation with remote experts is a useful tool, although some shortcomings exist. The financial and personal effort involved is considerable.

Computer Graphics↗

PubMed1999

Positioning of dental implants using computer-aided navigation and an optical tracking system: case report and presentation of a new method.

A navigation system for computer-aided surgery (Virtual Patient System, VPS) has been described in previous studies for different indications in oral and maxillofacial surgery. The aim of the system is the intraoperative transfer of preoperative planning on radiographs or CT scans on the patient, in real-time, and independent of the position of the patient's head. Until now an electromagnetic tracking system has been used for intra-operative position measurement. For placement of dental implants, the electromagnetic tracking system is not suitable since the motor of the implant drill leads to a considerable distortion of the magnetic field, thus direct visualization of drilling the implant socket was not possible. To overcome this problem, an optical tracking system which is not disturbed by conductive materials was integrated in the VPS system. The first patient operated on with this system had a posttraumatic loss of the upper incisors; three implants have been placed according to the prosthetic axis previously planned on radiographs and CT scans. The experience gained in this intervention led to the conclusion that computer-aided surgery provides a valuable tool in implant dentistry.

Adult↗

PubMed1999

Transoral miniplate osteosynthesis of condylar neck fractures.

OBJECTIVE: In a retrospective study, we reviewed a series of 55 consecutive patients with 57 fractures of the condylar neck that were treated with transoral miniplate osteosynthesis. STUDY DESIGN: Forty-one patients were included in a clinical follow-up study; the median length of study was 26.5 months (minimum, 7 months; maximum, 79 months). In a radiographic study, the positions of the condyle before open reduction, after open reduction, and more than 6 months postoperatively were evaluated in 3 radiographic planes. A statistical analysis was performed to determine factors that lead to secondary instability of the reduced condyle and to correlate the actual position of the condyle with clinical parameters collected in follow-up examinations. RESULTS: At the time of the follow-up examination, the median measurement of the mandibular openings was 48.3 +/- 8.0 mm (minimum, 32 mm; maximum, 66 mm). A deviation of 2 mm to the operated side when opening was observed in 7 patients. The median range of laterotrusion was 10.0 mm to the fracture side and 9. 0 mm to the opposite side. In 7 patients, radiographic follow-up more than 6 months postoperatively revealed a medial tilt of the proximal fragment of 15 to 40 degrees despite a good immediate postoperative position of the condyle. This may be attributed to bone resorption in the fracture gap, together with a bending instability observed when titanium miniplates with a thickness of 0. 9 mm were used. The position of the condyle at the follow-up examination did not correlate with clinical parameters. CONCLUSIONS: Transoral approach miniplate osteosynthesis of dislocated condylar neck fractures is indicated when visible scars in the head and neck region, which are encountered with other fixation techniques, must be avoided.

Adolescent↗

PubMed1999

Mandibular lengthening with an implanted motor-driven device: preliminary study in sheep.

Distraction osteogenesis with external or intraoral devices is an established method for lengthening human mandibles. In this preliminary study in three sheep a newly designed, fully implantable electromechanical device for mandibular lengthening was used. After osteotomy, the device was screw fixed to the mandible, and the power and control unit was inserted subcutaneously in the neck region. After a healing period of five days, the device was activated magnetically, allowing calibrated distraction steps of 0.04 mm/h, resulting in a total of 1.0 mm/day. Over a period of 14 days, a maximum mandibular lengthening of 13.6 mm could be achieved without transmucosal activation. Depending on stability of the screw fixation, membranous and/or cartilaginous bone formation was observed in the callus by radiological and histological evaluation. Further experimental research is ongoing to prove the clinical usefulness of this device.

Animals↗

PubMed1999

Computer-aided surgery in distraction osteogenesis of the maxilla and mandible.

When using unidirectional intraoral distraction devices, it is desirable to be able to determine the final position of the bone fragment after the distraction procedure. However, additional constraining forces from adjacent tissues render the prediction of the distraction direction difficult. We have utilised computer-aided surgery in three patients for intraoperative control of the distraction direction. In one cleft palate patient, suffering from maxillary hypoplasia and anterior open bite, a modified Le Fort I osteotomy and maxillary distraction was performed. Despite a ventrocaudal position of the distraction device, intraoperative computer visualisation showed an unfavourable caudal vector of distraction without any anterior movement. The final result confirmed the direction indicated by the computer. Maxillary advancement remained insufficient. In two patients suffering from mandibular hypoplasia, intraoperative assessment revealed a favourable direction of distraction. The distraction procedure led to a satisfactory result in both cases. Computer-aided surgery is helpful in assessing the vector of distraction intraoperatively, making the result of the distraction procedure more predictable and allowing instant correction by adequate reapplication of the device.

Adolescent↗

PubMed1999

Horseshoe Le Fort I osteotomy: an augmentation technique for the severely atrophied maxilla--an eight-year follow-up.

Twenty-three patients (19 female, 4 male; 37-69 years old; mean age, 52 years) underwent horseshoe Le Fort I osteotomy from 1989 to 1997; 178 iMZ implants were placed either simultaneously by horseshoe Le Fort I osteotomy (76 implants) or in a second operation 6-12 months later (102 implants). Removable overdentures were made. Twenty-two patients wear an implant-borne overdenture; 1 patient refused an additional operation for placing implants and received a conventional, mucosally supported, upper-jaw prosthesis. The anteroposterior relationship satisfactorily improved in all patients, allowing for class I occlusion. All patients were satisfied with the aesthetic results, denture retention, speech, and mastication. Nevertheless, we lost 8 implants in 1 patient. We placed 178 endosteal implants in 22 patients; 8 were lost in 1 patient, and 7 more implants have been lost in 5 patients.

Acute Disease↗

PubMed1999

Histomorphologic findings on human bone samples six months after bone augmentation of the maxillary sinus with Algipore.

Sinus grafting, a popular and standard treatment for maxillary atrophy, uses a variety of grafting materials. In this study, specimens obtained 6 months after sinus grafting with Algipore were evaluated under light microscopy and showed osseoformation, xenograft degradation, and bone ingrowth into particles. Osteoblastic cells were embedded in the intracorpuscular bone matrix, which indicated that xenograft particles are an osseoconductive scaffold and stimulate matrix deposition. Acute inflammatory responses after insertion of Algipore did not occur. Particles were degraded during physiologic bone remodeling, and newly formed bone gradually replaced resorbed biomaterial.

Bone Substitutes↗

PubMed1999

2D and 3D computer tomography and sinus graft analysis with various graft materials.

Sinus grafting has been a routine surgical procedure since the 1970s. Computer tomography (e.g., SIM/Plant) is available for planning and simulation, but it has not been used to control the success and the long-term results of the planned surgery. The aim of this work was to apply a prospective examination method to determine (a) the extent to which the success of sinus grafting can be followed through 2D (two-dimensional) and 3D (three-dimensional) CT (computer tomography) reconstruction, (b) when choosing this method is worthwhile, and (c) how to visualize incorporating and transforming various graft materials. Twelve patients received 21 sinus graftings, with immediate implantation. Four 2D and 3D CT reconstructions were performed: (1) preoperatively, (2) 1-2 weeks postoperatively, (3) before loading, and (4) 1 year after completing prosthodontic treatment. The sinus grafts were composed of a mixture of HTR Bioplant polymer and autograft, or from a mixture of Algipore (HA, hydroxyapatite) and autograft. In the bilateral cases, both sinus graft mixtures were used, one on each side. The posterior-anterior, the lateral, and the superior-inferior views provided the most useful information; the usefulness of serial images is very limited. Individual 2D and 3D CT reconstructions are proposed, however, in cases of extensive bone atrophy, if complications are expected, if complications arise during surgery, if healing is protracted, or if the documentation is important for other reasons. The long-term results of the two graft materials could be followed up extremely well. Both materials proved outstandingly suitable for sinus grafting.

Adult↗

PubMed1998

Fixation of zygomatic fractures with a new biodegradable copolymer osteosynthesis system. Preliminary results.

In a prospective study, a new biodegradable osteosynthesis material for the facial skeleton has been used in 27 patients with zygomatic fractures. In the six-month follow-up period, the first ten patients showed clinically and radiologically uneventful healing of bone. There were no implant-related complications. The main advantages of the new material are its malleability when heated, enabling fast adaptation to the bone surface, and the avoidance of a second operation for implant removal.

Absorbable Implants↗