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Biomedical subjects

R Schön

Publications and source records attributed to R Schön.

At least 19 recordsLinked to original sources
PubMed2006

Topographical CT-data analysis of the human orbital floor.

The aim of this study was to evaluate the topographical anatomy of the human orbital floor for the production of prefabricated implants on the basis of computer tomography data. A database of 279 CT scans of Caucasian patients without traumatic deformation of the midface was analysed. 3D-image segmentation of the midfacial skeleton was performed using a computer-assisted protocol. A virtual plane (50 x 50 mm (2)) was constructed using defined landmarks above the orbital floor. An automated procedure was used to measure the distance between the orbital floor and the constructed plane at 400 distinct points. A mathematical algorithm was used to analyse the data, and to calculate a map of the orbital floor. Statistical analysis of the data revealed that orbital floor topography could be classified as distinct clusters. There were 12 variations of orbital floor anatomy: three unique patterns of the orbital floor for the right orbit and three corresponding patterns for the left side, all of which varied between the sexes. The 12 patterns were constructed with a statistical confidence interval of 1.36+/-0.6mm.

Adult↗
PubMed2006

Individually preformed titanium mesh implants for a true-to-original repair of orbital fractures.

The purpose of this investigation is to present the results using preoperatively-formed titanium mesh implants for a true-to-original primary repair of extensive orbital floor and medial wall fractures. Individually preformed implants were used to repair extensive orbital floor injuries in 19 patients at the University Hospital, Freiburg. The form of the orbital floor and walls was analysed by preoperative diagnostic CT scan data. The form of the virtual reconstructed orbit was transformed into a model of the orbital cavity by a template machine. Postoperative imaging by or CT scan verified the exact 3D reconstruction of the orbital cavity 'true to original'. None of the patients demonstrated diplopia or enophthalmos postoperatively. Using individually preformed titanium mesh implants, the accuracy of the 3D orbital reconstruction was within a range of 1mm. The reconstruction using preformed implants proved to be less time consuming, more precise and less invasive, compared to 'free hand' efforts, for the repair of orbital injuries using titanium mesh and calvarial grafts.

Biocompatible Materials↗
PubMed2005

A congenital teratoma with a cleft palate: report of a case.

Teratomas are benign tumors containing cells from ectodermal, mesodermal and endodermal layers. They occur in about 1 in every 4000 births and most commonly in the sacrococcygeal region, followed by the ovaries. Congenital epignathus teratomas are rare embryological neoplasms localised in the region of head and neck. An epignathus is found in approximately 1:35,000 to 1:200,000 live births. This accounts for 2-9% of all teratomas. Size and location of the neoplasm in the oronasopharynx is variable. Teratomas are partly undiagnosed at the time of birth. They may exist with an intracranial extension or as small polyps. Large epignathi can lead to difficult management during and after birth. The case of a newborn girl with a combination of an epignathus and a cleft palate is described. The epignathus presented as a huge mass extending out of the mouth of the infant girl. On the day of birth debulking of the extraoral portion of the tumor, followed by intraoral exstirpation, was performed. The results of the histologic examination indicated a congenital epignathus. Six months later a recurrence was found.

Cleft Palate↗
PubMed2005

[Computer assisted methods in reconstructive and function-preserving orbital surgery. New capabilities of computer assisted preoperative surgical planning (CAPP) and computer assisted surgery (CAS)].

BACKGROUND: Orbital reconstruction after tumor or trauma makes high demands on the surgeon when restoring the optic axis and cosmetic features. Computer-assisted preoperative planning surgery (CAPP) and computer-assisted surgery (CAS) allow calculation of the form of the orbital cavity to be reconstructed preoperatively as well as the process of its realization intraoperatively. METHODS: We developed new planning software methods for this surgical procedure. For validation the deviation of accuracy was assessed between the virtual and the real model in eight patients with surgical reconstruction of the orbit. RESULTS: The check of accuracy of the reconstructions compared to the planning of the surgery by fusion of preoperative and postoperative data resulted in a mean deviation of 1.74 mm. The volumetric measurements presented a mean deviation of 0.2 cm(3) with an accuracy of >99%. The accuracy of linear measurements with the techniques of image fusion of the "feature-based" method was 0.38 mm and thus close to the technical threshold of effective data accuracy of 0.35 mm. The enophthalmus could be assessed more objectively with this method compared to using the Hertel index. CONCLUSIONS: CAPP and CAS are helpful in reconstructive orbital surgery to verify the position of the optic axis and the cosmetic result intraoperatively.

Adult↗
PubMed2005

[Primary pulmonary rhabdomyosarcoma as a rare differential diagnosis of small cell lung cancer].

Primary pulmonary rhabdomyosarcoma is a rare entity and the histological differential diagnosis can be difficult. We report on a 43-year old female patient, smoker (25 pack-years), in whom a large solitary brain metastasis was diagnosed and enucleated. Histological examination revealed a typical small cell carcinoma and histological examination of biopsies obtained from a tumor in the left upper lobe of the lung was compatible with a small cell carcinoma. Despite chemotherapy there was a progressive tumor growth. Bronchial biopsies again showed a small cell tumor, although immunohistochemistry proved it to be a pleomorphic rhabdomyosarcoma. Due to the progressive tumor growth with necrosis and superinfection and a lack of further metastases lobectomy of the left upper lobe was performed, complicated by postoperative pleural empyema, limiting the possibilities of adjuvant therapy. Early relapse occurred with pleural, pulmonary, chest wall and spinal metastases. Laminectomy and extirpation of the spinal metastases, local radiotherapy and chemotherapy with iphosphamide and doxorubicine led to partial remission and clinical improvement for few months only. The patient died from metastatic primary rhabdomyosarcoma of the lung. This rare tumor mimicked small cell lung cancer. Appraisal of the atypical clinical course and a close dialogue between pathologists and clinicians enabled the correct diagnosis.

Adult↗
PubMed2003

Early antithrombotic prophylaxis with low molecular weight heparin in neurosurgery.

BACKGROUND: Despite the high risk of venous thromboembolic events (VTE) in neuro-surgical patients, heparin prophylaxis has not been routinely established due to concern about bleeding complications. After initiating early low molecular weight heparin (LMWH) prophylaxis, we reviewed our patients in order to examine the viability of this practice. METHOD: Over a 3 year period, the records of patients admitted for elective neuro-surgery (ES), head injury (HI) or spontaneous intracranial haemorrhage (ICH) were analysed. Prophylaxis was performed with certoparin (3000 U anti-factor Xa s.c.) on the evening before ES and within 24 hours after surgery or admission whenever a CT did not show a progressive haematoma. Contraindications for LMWH were prothrombin time <70%, partial thrombo-plastin time >40 s, platelet count <100.000/ml, and platelet aggregation test sum <60%. The incidence of bleeding complications, VTE, and resulting morbidity/mortality was assessed. FINDINGS: 294 patients were admitted for ES, 344 for HI, and 302 for ICH. 155 of these were excluded because of contraindications. Intracranial bleeding was recorded in 1.5% (ES 1.1%, HI 3.5%, ICH 0%) and operative revision was performed in 1.1% (ES 0.7%, HI 2.8%) of patients. One case of moderate disability and no mortality occurred. The incidence of VTE and pulmonary embolism was documented in 0.2% and 0.1% of patients, with no associated mortality. No heparin induced thrombocytopenia was observed. INTERPRETATION: In neurosurgical patients, antithrombotic prophylaxis with certoparin was determined to be safe and efficacious when contraindications are carefully considered and a 12-hour time interval before and after surgery was guaranteed. This retrospective analysis should encourage a prospective trial of early LMWH prophylaxis.

Adult↗
PubMed2003

Swallowing and speech function after intraoral soft tissue reconstruction with lateral upper arm free flap and radial forearm free flap.

Swallowing, speech, and morbidity were assessed postoperatively in 25 patients, 18 of whom had had intraoral defects reconstructed by lateral upper arm free flaps (LUFF) and 7 by radial forearm free flaps (RFFF). Video fluoroscopy was used to assess swallowing, the Freiburger audiometric test to assess speech; and measurement of arm circumference to assess donor site morbidity. A questionnaire was used to evaluate swallowing, speech, and donor site morbidity subjectively. The degree of impairment in swallowing depended on the site of resection. Anterior and posterior resections affected swallowing more than lateral resections. Anterior resection and the use of LUFFs reduced intelligibility. There was no significant difference in impairment between LUFF and RFFF. We conclude that the LUFFs are superior to RFFFs because they can be closed primary and the incidence of donor site morbidity is slight.

Adult↗
PubMed2003

Evaluation of swallowing function after intraoral soft tissue reconstruction with microvascular free flaps.

This study assessed swallowing function after tumour resection and reconstruction utilizing free vascularized flap closures in patients with oral cancer. Swallowing function was evaluated postoperatively in 23 patients (21 men and 2 women) who had undergone reconstruction with either a lateral upper arm free flap (LUFF, n=16) or a radial forearm free flap (RFFF, n=7). Videofluoroscopy was used to assess tongue mobility and abnormalities of swallowing function. All patients who underwent reconstruction with LUFF or RFFF free flaps had decreased tongue mobility, except for the tip of the tongue. Patients who underwent anterior or posterior resection had greater decreases in tongue mobility than those who underwent medial resection. Swallowing impairment was similar in patients with LUFFs and those with RFFFs. Anterior resection of the oral cavity had a significant negative effect on swallowing function. Silent aspiration occurred in five patients. In conclusion the resection site affected swallowing function, but the type of flap did not, in patients with oral carcinoma, who underwent tumour resection with reconstruction

Adult↗
PubMed2002

[Extraoral and intraoral endoscopically assisted management of collum fractures].

AIM OF THE STUDY: Using limited extraoral and transoral incisions for an endoscopically assisted open reduction of condylar mandible fractures, the risk of facial nerve damage and extensive visible scars can be reduced. PATIENTS AND METHODS: The endoscopically assisted treatment of 17 consecutive patients with fractures of the condyle was performed from April 1998 to December 1999. Of the 17 patients, 14 had additional mandibular fractures, and 11 of the condylar fractures were dislocated. Of the 17 patients, 9 were treated by submandibular and 8 by transoral approach. Adequate anatomic reduction was achieved by the submandibular and transoral approaches using an endoscopically assisted technique. APPROACHES: In four patients angulated drills and screwdrivers facilitated the transoral treatment of condylar fractures. Transbuccal stab incisions and the use of trocars were not needed in these four patients. The transoral approach proved to be a reliable surgical approach for fractures of the mandibular condyle even when dislocation with lateral override was present. The extraoral approach was used for severely dislocated fractures such as fractures with medial override or comminution.

Adult↗
PubMed2002

[Color duplex ultrasound in monitoring vascularized fibula transplants].

BACKGROUND: For the successful management of vascularized free fibular bone grafts, the early detection of vascular complications is important. When vascular complications are suspected without a reliable monitoring of the graft perfusion, revision surgery often proved to be unnecessary. Color duplex sonography for the postoperative monitoring of free fibular bone grafts without a skin island is demonstrated. MATERIAL AND METHODS: The quantitative and qualitative monitoring of the perfusion of microvascular anastomosis and the transplanted tissues using color duplex sonography with a 7.5-Mhz scanner (Elegra, Siemens, Germany) for the postoperative monitoring of 12 free fibular bone grafts was performed. Using color duplex sonography, the perfusion of the vascular pedicle and the free fibular bone grafts was demonstrated in all 12 free fibular bone grafts. In three patients vascular complications and failure of the bone grafts were suspected due to postoperative complications next to free fibular bone grafts such as abscess formation, wound dehiscence, and disturbances of wound healing. Using color duplex sonography, adequate perfusion of the vascular pedicle and the transplanted tissue was demonstrated and therefore revision surgery not indicated. DISCUSSION: Color duplex sonography is a reliable, noninvasive, and inexpensive method for the postoperative monitoring of free fibular bone grafts.

Ameloblastoma↗
PubMed2002

Endoscopy-assisted open treatment of condylar fractures of the mandible: extraoral vs intraoral approach.

By using an endoscopy assisted extraoral and transoral approach for open reduction of condylar mandible fractures with limited incisions, the risk of facial nerve damage and extensive visible scars can be reduced. The endoscopy-assisted treatment of 17 consecutive patients with fractures of the condyle was performed from April 1998 to December 1999. Of the 17 patients, 13 presented with additional mandibular fractures. Nine of the 17 patients were treated by a submandibular approach and eight by a transoral approach. Adequate anatomic reduction was achieved by the submandibular and transoral approach using an endoscopy-assisted technique. The transoral approach proved to be a reliable surgical approach for fractures of the mandibular condyle, even when dislocation with lateral override was present. In four patients, angulated drills and screwdrivers facilitated the transoral treatment of condylar fractures. Transbuccal stab incisions and the use of trochars were not needed in these four patients. The extraoral approach was indicated for severely dislocated fractures such as fractures with medial override or comminution.

Adult↗
PubMed2001

Mandibular fractures in Townsville, Australia: incidence, aetiology and treatment using the 2.0 AO/ASIF miniplate system.

In 1995 a total of 114 patients presented with 154 mandibular fractures at the Townsville General Hospital, Australia. Fifty-eight (51%) were white, 50 (44%) aboriginal, and six (5%) of other or unknown race. One-hundred-and-twenty-four of the fractures (81%) occurred in male and 30 (19%) in female patients. Most fractures (n= 128, 83%) resulted from fights. The rest being a result of road traffic accidents (10%), falls (3%), accidents caused by falling objects (3%) and sport accidents (2%). The mandibular angle (n= 66, 43%) and the symphyseal area (n= 40, 26%) were the most common fracture sites. Combined fractures were found in 30% patients (26%). Of all angle fractures, 97% were related to third molars. One-hundred-and-five patients had open reduction by an intraoral approach and stabilization by 2.0 AO/ASIF titanium miniplates and nine closed reduction. Complications included temporary sensory deficit of the mental nerve (3%), minor malocclusion (2%) and infection or dehiscence (5%). We conclude that osteosynthesis of mandibular fractures by the 2.0 AO/ASIF titanium miniplate system is reliable.

Accidents↗
PubMed2001

In vitro comparison of the two hard-hard articulations for total hip replacements.

Polyethylene particle disease is one of the major causes of late aseptic loosening of total hip replacement. Two hard-hard articulations (alumina-on-alumina and metal-on-metal) have been developed in Europe as an alternative to the ultra-high molecular weight polyethylene (UHMWPE) articulations. Even though these hard-hard articulations are on the market and numerous reports have been published about them, only a very limited number of studies allowing a direct in vitro comparison of the two articulations have been published so far. This paper compares in vitro these two types of articulation (alumina-on-alumina and metal-on-metal), which have been tested with a hip simulator for their tribological behaviour using exactly the same experimental methodology. This comparison shows that these two types of hard-hard articulation have very similar abrasive wear behaviour with four main features: 1. A running-in wear period (1 x 10(6) cycles) gives a cumulative wear of about 20 microns with head diameters of 28 mm. 2. After the running-in wear, there is a stabilization of the linear wear behaviour with a low linear wear rate/10(6) cycles for both types of articulation. 3. The volumetric wear rate of both articulations (< 2.0 mm3/year for head diameters of 28 mm) is significantly lower than that observed for metal-on-polyethylene or ceramic-on-polyethylene articulations having the same head diameter. 4. Abrasive wear is readily apparent (indicating a mixed lubrication regime) with both types of articulation. The extremely low wear performance of these articulations is confirmed and they constitute a low-wear alternative to the UHMWPE articulations currently used.

Arthroplasty, Replacement, Hip↗
PubMed2001

Non-protein bound dienogest in serum and salivary dienogest in women taking the oral contraceptives Certostat and Valette.

Dienogest (17 alpha-cyanomethyl-17-hydroxy-4,9-estradien-3-one) is the progestagen component of the oral contraceptives Certostat and Valette. In contrast to other 19-norsteroid progestagens like levonorgestrel, norethisterone, gestodene and 3-ketodesogestrel, dienogest does not bind to sexual hormone binding globulin (SHBG). The absent binding to SHBG results in a high portion of free, non-protein bound dienogest in serum. In female volunteers taking the oral contraceptives Certostat and Trisiston, the part of non-protein bound dienogest and levonorgestrel, respectively, in serum was determined by the method of centrifugal ultrafiltration. The portion of free dienogest was found to be 9.55 +/- 0.95% (m +/- SD, n = 13) of total serum dienogest. Free levonorgestrel constituted 0.97 +/- 0.14% (n = 12) of total serum levonorgestrel. In an investigation with 47 female volunteers taking Certostat, serum total dienogest was quantified by a specific radioimmunoassay and free dienogest in serum by centrifugal ultrafiltration. In the serum samples with dienogest concentrations in the range of 4.1-57.7 ng/ml, the part of free, non-protein bound dienogest was found to be 8.90 +/- 0.54% of serum total dienogest. There is a high correlation between serum total dienogest and free dienogest (r = 0.989). In another investigation with 20 female volunteers taking the contraceptive Valette, serum total dienogest and salivary dienogest were quantified by radioimmunoassay and free dienogest in serum by centrifugal ultrafiltration. In the serum samples with dienogest concentrations in the range of 7.5-50.6 ng/ml, the part of free, non-protein bound dienogest was 8.78 +/- 0.77% of serum total dienogest. Salivary dienogest constituted 7.99 +/- 0.94% of serum total dienogest showing a high correlation with serum free dienogest (r = 0.953) and serum total dienogest (r = 0.958). The high portion of non-protein bound compound in serum is a characteristic pharmacokinetic feature of dienogest.

Adult↗
PubMed1999

[Therapy refractory idiopathic thrombocytopenia. Contraindication for dental surgery interventions].

Hemorrhagic diathesis represents a high risk for oral surgery. In clinical practice various kinds of diathetic diseases are seen that are of plasmatic, vascular, thrombocytic and hypertensive origin. Usually these patients will be primarily referred to the hospital as high-risk cases. Therefore, a broad spectrum of diagnostic and therapeutic interdisciplinary methods are available, so that as a rule it is possible to obtain a clear picture of the severity of the bleeding tendency. We represent a case of a 58-year-old woman who had decayed teeth with chronic periodontal and periapical lesions, who could not be treated by oral surgery because of refractory idiopathic thrombocytopenic purpura (ITP) with 1000 platelets/microliters. The patient's history showed that various hematologic concepts had been tried, including splenectomy, but all had failed entirely. After therapy with steroids, immunosuppressive and cytostatic agents, and even after administering immunoglobulins and substitution with platelets, the count did not increase; thus, an absolute contraindication for all kinds of surgery was declared. This rare example indicates that unmanagable bleeding diseases still exist that should be known by dentists and oral surgeons to prevent making deleterious therapeutic decisions.

Contraindications↗
PubMed1999

Kinematic MR imaging in surgical management of cervical disc disease, spondylosis and spondylotic myelopathy.

PURPOSE: To estimate the clinical value and influence of kinematic MR imaging in patients with degenerative diseases of the cervical spine. MATERIAL AND METHODS: Eighty-one patients were examined with a 1.5 T whole body magnet using a positioning device. Cervical disc disease was classified according to clinical and radiographic findings into 4 stages: stage I=cervical disc disease (n=13); stage II=spondylosis (n=42); stage III=spondylosis with restricted motion (n=11); and stage IV=cervical spondylotic myelopathy (n=15). Findings on kinematic MR images were compared to those on flexion and extension radiographs, myelography, CT-myelography and static MR imaging. Furthermore, the influence of kinematic MR imaging on surgical management and intra-operative patient positioning was determined. RESULTS: Additional information obtained by kinematic MR imaging changed the therapeutic management in 7 of 11 (64%) patients with stage III disease, and in 13 of 15 (87%) patients with stage IV disease. Instead of an anterior approach, a posterior surgical approach was chosen in 3 of 11 patients (27%) with stage III disease and in 6 of 15 patients (40%) with stage IV disease. Hyperextension of the neck was avoided intra-operatively in 4 patients (27%) with cervical spondylotic myelopathy, and in 1 patient with stage II (2%) and in 1 patient with stage III (9%) disease. Kinematic MR imaging provided additional information in all patients with stages III and IV disease except in 1 patient with stage III disease, when compared to flexion and extension radiographs, myelography, CT-myelography and static MR examination. CONCLUSION: Kinematic MR imaging adds additional information when compared to conventional imaging methods in patients with advanced stages of degenerative disease of the cervical spine.

Cervical Vertebrae↗
PubMed1999

Management of vein of Galen malformations. A review based on five neurosurgically treated cases and literature reports.

The high morbidity and mortality associated with the management of vein of Galen aneurysmal malformations (VGAM) continues to pose a tremendous challenge to the neurosurgeon as well as to the attending interventional radiologist. Since 1985, five patients with VGAM have been referred to the neurosurgical unit of the University of Cologne, two neonates, one infant and two adults. Four patients underwent direct operation and two patients received a shunt. The treatment was performed without mortality. A review of the literature reflects no substantial difference between neurosurgical treatment during the last 15 years (mortality 10%) and endovascular treatment (best series mortality 6%).

Adult↗