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Jürgen Hoffmann

Publications and source records attributed to Jürgen Hoffmann.

12 recordsLinked to original sources
PubMed2005

Validation of 3D-laser surface registration for image-guided cranio-maxillofacial surgery.

AIM: Image-data-based navigation plays an important role during surgical treatment in anatomically complex areas. Conventional patient-to-image registration techniques on the basis of skin and bone markers require expensive and time-consuming logistic support. A new markerless, high-resolution laser surface scan technique for patient registration has been tested in experimental and clinical settings. METHODS: In a phantom study, a skull model was registered with laser scanning and marker-based algorithms. The registration procedure was repeated 25 times in each group. The values for the root mean-square error were calculated as a measure of the deviation of the forecast position from the actual position and the target difference. In a clinical setting, 21 consecutive patients who presented with cranio-maxillofacial disorders were scheduled for navigational surgery using laser surface scanning for patient-to-image registration. Here the accuracy was determined by anatomical landmark localization. RESULTS: In the experimental study, a root mean-square error of 1.3+/-0.14 mm, and a mean target deviation of 2.08+/-0.49 mm were found for laser scanning. In contrast, a root mean-square error of 0.38+/-0.01 mm and a mean target deviation of 0.99+/-0.15 mm were found for marker registration. The differences were statistically significant (p<0.005). A strong correlation between the root mean-square error and the target deviation was found for laser (r=0.96) and marker registration (r=0.95). During the 21 clinical procedures, the overall accuracy of laser scan registration determined by the root mean-square error was 1.21+/-0.34 mm, and the mean clinical precision was 1.8+/-0.5 mm. CONCLUSIONS: Three-dimensional laser surface registration offers an interesting approach for selected image-guided procedures in cranio-maxillofacial surgery.

Face↗
PubMed2005

Cleft palate fistula closure with a mucosal prelaminated lateral upper arm flap.

BACKGROUND: Recurrent cleft palate fistula is a challenge for maxillofacial surgeons. In severe cases, microvascular tissue transfer is necessary to treat these patients successfully. METHODS: A 23-year-old man with cleft lip and palate, previously treated elsewhere, presented with a 2-cm defect in the posterior hard palate. A tongue flap had already been performed. It was decided to close the persistent fistula with a lateral upper-arm flap. In a first-step operation, a free graft of buccal mucosa was fixed to the lateral upper arm subcutaneously and covered with an alloplastic sheet. After 11 weeks, the prelaminated flap was harvested and transferred to the palate. RESULTS: Integration of the buccal mucosa to the upper arm was uneventful. On harvesting the flap, we found a smooth, thin, and continuous fasciomucosal flap with a mucosa surface of 4 x 4 cm. Healing of the microvascular flap in its recipient site was regular. The fistula was closed successfully. CONCLUSIONS: To the authors' knowledge, this is the first report of a lateral upper-arm flap prelaminated with autologous mucosa. By prelamination, it is possible to circumvent the disadvantage of extraoral skin within the oral cavity and to cover mucosal defects with mucosa, especially in elective procedures, such as cleft cases.

Adult↗
PubMed2005

Accuracy of navigation-guided socket drilling before implant installation compared to the conventional free-hand method in a synthetic edentulous lower jaw model.

In this study, the three-dimensional (3D) accuracy of navigation-guided (NG) socket drilling before implant installation was compared to the conventional free-hand (CF) method in a synthetic edentulous lower jaw model. The drillings were performed by two surgeons with different years of working experience. The inter-individual outcome was assessed. NG drillings were performed using an optical computerized tomography (CT)-based navigation system. CF drillings were performed using a surgical template. The coordinates of the drilled sockets were determined on the basis of CT scans. A total of n=224 drillings was evaluated. Inter-individual differences in terms of the surgeons' years of work experience were without statistical significance. The mean deviation of the CF drilled sockets (n=112) on the vestibulo-oral and mesio-distal direction was 11.2+/-5.6 degrees (range: 4.1-25.3 degrees ). With respect to the NG drilled sockets (n=112), the mean deviation was 4.2+/-1.8 degrees (range: 2.3-11.5). The mean distance to the mandibular canal was 1.1+/-0.6 mm (range: 0.1-2.3 mm) for CF-drilled sockets and 0.7+/-0.5 mm (range: 0.1-1.8 mm) for NG drilled sockets. The differences between the two methods were highly significant (P<0.01). A potential benefit from image-data-based navigation in implant surgery is discussed against the background of cost-effectiveness.

Analysis of Variance↗
PubMed2005

Evaluation of dental injury following endotracheal intubation using the Periotest technique.

The hazards of damage to teeth and their periodontal attachment during tracheal intubation are well known. Dental trauma represents the commonest single reason for complaints against anesthesiologists. In order to predict the possible risk of perianesthetic iatrogenic tooth luxation we evaluated the use of a measuring method (Periotest technique), being well established for the diagnosis of periodontal disease. In 120 patients undergoing elective surgery, we compared the amount of tooth mobility before and after general anesthesia to different scores assessing the difficulty of tracheal intubation. Furthermore, the level of work experience of the intubating anesthetist was compared with the degree of postoperative tooth mobility. Changes of periodontal attachment could not be detected by the Periotest technique. The Periotest technique does not seem to have the ability to detect early periodontal changes associated with endotracheal intubation.

Adolescent↗
PubMed2004

Ossifying fibroma of the skull: interactive image-guided minimally invasive localization and resection.

Ossifying fibroma is a benign fibro-osseous tumor commonly affecting the craniofacial bones. It is considered to be a locally aggressive and quickly expansible bone lesion. Because of its aggressive nature and high recurrence rate, early detection and complete surgical removal are essential. Usually, these lesions are excised extensively by craniectomy, and bone loss is reconstructed by cranioplasty using acrylic resin or titanium implants. Alternatively, in the management of skull-ossifying fibroma, an image-guided technique using surgical navigation may provide precise information about localization, enabling complete removal, thereby operating with minimal exposure and within narrow resection borders and avoiding significant bone deformity. A 39-year-old male patient with a history of renal cell carcinoma was admitted to our hospital because a radionuclide scintigraphic bone scan revealed increased uptake in a small area located at the left lateral skull bone. The high-resolution computed tomography scan showed that the lesion was located inside the diploe, destroying the inner table of the calvarium. The patient underwent minimally invasive bone lesion removal using an interactive image-guided approach. Complete resection of the neoplastic lesion was achieved. The histopathological examination revealed an ossifying fibroma. The postoperative course was uneventful, and the patient was discharged 3 days after intervention. To date, there has been no evidence of local recurrence. Interactive multimodal planning and intraoperative image guidance offer an interesting approach for biopsy and minimally invasive removal of small ossifying fibroma lesions of the skull, especially in less accessible locations.

Adult↗
PubMed2004

Temporary intermaxillary fixation using individualized acrylic splints permits image-data-based surgery of the lower jaw and oropharynx.

OBJECTIVES/HYPOTHESIS: Image-data-based surgical navigation is used as a helpful device in the operating room to localize critical structures with a high degree of accuracy. It also enables physicians to plan therapeutic performance. Because it relies on preoperatively acquired computed tomography (CT) or magnetic resonance imaging (MRI) data, there is restricted access for navigation of surgical instruments in areas that show motion uncorrelated with radiologic data. Thus, in the case of moveable structures, for example the lower jaw, navigational procedures could not yet be applied. STUDY DESIGN: We introduce a new technique using individualized intermaxillary splints that fix the mandible in a reproducible aboccluded position at the time of image-data acquisition and surgery. METHODS: Different manufacturing processes were investigated. The feasibility of uni- and bilateral intermaxillary splints was studied under clinical conditions in four patients during different procedures in the mandibular and oropharyngeal regions. RESULTS: The manufacturing of the splints showed was easily performed in a short time. With bilateral fixation, there was a high anatomic target precision of 1.6 to 2.3 mm. CONCLUSIONS: The use of bilateral intermaxillary splints that fix the patient's mandible in a reproducible aboccluded position permits an image-data-based navigated surgical approach to the oropharyngeal and mandibular regions.

Humans↗
PubMed2003

Central resorption in an iliac crest transplant with microvascular anastomosis--report of 2 cases.

INTRODUCTION: The microvascular iliac crest flap is preferred for repair of segmental mandibular defects. Its viability and constant size are regarded as a great advantage for oral rehabilitation. PATIENTS: Two patients with oral cancer and recurrent keratocyst underwent mandibular reconstruction with an iliac crest transplant. Wound healing was uneventful. RESULTS: Several years after reconstruction we noticed complete absence of cancellous bone in the transplants. The cortical aspect consisted of vital bone. CONCLUSION: Secondary to changes in the blood supply after tissue transfer, microvascular bone transplants may develop complete medullary resorption. Substitution of this central bone is variable and may not happen at all.

Anastomosis, Surgical↗
PubMed2003

Survival rate of IMZ implants: a prospective 10-year analysis.

PURPOSE: The purpose of this study was to determine the success of IMZ implants after prosthodontic rehabilitation. PATIENTS AND METHODS: A prospective study analysis was made of the treatment results for 541 patients after the insertion of a total of 1,250 IMZ implants at 2 practicing dentists' offices over a period of 13 years. The most frequent treatment situations were insertion in the totally edentulous lower jaw (44.1%) and in a distal edentulous region (37.6%). The statistical survival rate assessment was made using Kaplan-Meier survival analysis. The results were compared with the cumulative survival rates for all implants during a period of 10 years. RESULTS: At 5 years after insertion, 96.0% of all implants were in situ and noninflamed; after 10 years, the survival rate was 82.4%. For both the upper and the lower jaw, better results were recorded in the posterior part of the jaw than in the anterior part. CONCLUSIONS: The IMZ implant system showed a good 10-year-survival rate.

Adult↗
PubMed2002

[IMZ implants in the treatment of the shortened dental arch in the upper and lower jaws].

The aim of this study was to evaluate the long-term prognosis after insertion of 510 IMZ-implants in case of free-end situations of the upper and lower jaw and prosthodontic restoration. We examined 222 patients prospectively who were treated in a dental practice because of uni- or bilateral free-end situation between 1984 and 1996. Affected and crowned teeth which were neighbouring the implant-based suprastructure, were blocked with these by use of bridge-restorations or attachments. In all the other cases purely implant-based bridge or single-tooth restorations were inserted. Clinical parameters as for example the peri-implant tissue reaction, sulcus depths as well as implant mobility and radiological findings were documented and evaluated statistically. In case of pure implant-based suprastructures we found six implant losses (1.2%), whereas in case of combined tooth-implant-based prosthodontic restorations 20 losses (3.9%) were found.

Adult↗
PubMedDate not supplied

Navigation-assisted sclerotherapy of orbital venolymphatic malformation: a new guidance technique for percutaneous treatment of low-flow vascular malformations.

Percutaneous sclerotherapy of orbital low-flow vascular malformations requires precise procedural guidance. For the treatment of a patient with an orbital venolymphatic malformation, we sought to optimize guidance by combining navigation assistance for needle placement with intralesional contrast medium injection for assessment of venous drainage. By using a surgical navigation system (Vector Vision, BrainLAB, Munich, Germany), multiplanar target lesion visualization was performed after fusion of CT and MR imaging data, which allowed precise puncture planning.

Adult↗
PubMedDate not supplied

Accuracy assessment of image-guided implant surgery: an experimental study.

PURPOSE: To accurately accomplish the drilling of an implant socket, the use of image-guided navigation has become an option. The aim of this study was to evaluate the 3-dimensional (3D) accuracy of navigation-guided drilled holes. MATERIALS AND METHODS: Laboratory accuracy measurements were obtained on an acrylic resin model with standardized target holes drilled by a computerized numerical control machine. The model was scanned by a multislice computerized tomography scanner and registered with fiducial marker-based algorithms. Navigated drillings were performed using an optical navigation system based on passive marker technology. Coordinates of drilled holes were determined by a 3D-digitizer probe, and accuracy was assessed for all 5 degrees of freedom using a computer-aided design system (Pro/Engineer). RESULTS: A total of 240 drillings were evaluated. Mean registration error was 0.86 mm (SD 0.25 mm). Target point deviation between preplanned and actual drill starting point was 0.95 mm (SD 0.25 mm). The deviation in terms of full length was 0.97 mm (SD 0.34 mm), and mean angular deviation on the coronal and sagittal planes was 1.35 degrees (SD 0.42 degrees). DISCUSSION: The accuracy of image-guided navigation depends on imaging modalities, patient-to-image registration procedures, and instrument tracking. The technical accuracy and the navigation procedure, as evaluated in the study presented, seem to be of minor influence. CONCLUSION: The data obtained by this in vitro study demonstrate that the accuracy of navigation-based drilling may be sufficient for clinical practice, particularly in terms of the transferability of preplanned trajectories. However, in vivo clinical trials need to be performed to evaluate the clinical accuracy and treatment quality of navigation-guided interventions.

Acrylic Resins↗