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Biomedical subjects

D Rohner

Publications and source records attributed to D Rohner.

12 recordsLinked to original sources
PubMed2002

[Endoscopically assisted Le Fort 1 osteotomy: a study in human cadaver heads].

METHODS AND RESULTS: Endoscopically assisted Le Fort 1-osteotomy was performed in a cadaver study with six human skulls. Vertical incisions were used to approach the maxilla using the endoscope. The bone cuts could be carried out with a 4-mm osteotome preserving the buccal mucosa. The downfracture of the maxilla was accomplished without damaging the descending palatal arteries, which could be verified endoscopically. Rigid fixation was performed using 1.5-mm titanium plates (Synthes, Mathys AG, Bettlach, Switzerland) and self-drilling screws. DISCUSSION: This cadaver study showed that the Le Fort 1 osteotomy could be carried out through limited approaches using endoscopic techniques and self-drilling fixation tools. Further experimental work and improvements will help to introduce this technique into clinical application.

Bone Plates↗
PubMed2002

[Individually CAD-CAM technique designed, bioresorbable 3-dimensional polycaprolactone framework for experimental reconstruction of craniofacial defects in the pig].

METHODS: Twenty orbital defects (2 x 2 cm) were created in ten adult Yorkshire pigs. Two software products (Velocity and Mimix) were evaluated with regard to image processing, three-dimensional reconstruction, and fabrication of individually shaped polycaprolactone (PCL) scaffolds to reconstruct these defects. Four different techniques were tested for the reconstruction: group 1 = no reconstruction, group 2 = polylactide sheet, group 3 = PCL scaffold, group 4 = bone marrow-coated PCL scaffold. The pigs were sacrificed at 3 months. RESULTS: In group 1 soft tissue scar formation could be found, but without any new bone. Group 2 showed a thick fibrous capsule around the PLLA sheet, whereas at the border zone of the defect signs of new bone formation could be detected. In group 3 the PCL scaffolds were filled with fibrous tissue and some areas that showed new bone formation (6.4% of the area of the defect). In group 4 the new bone formation (17.8% of the area of the defect) was significantly higher in quantity than in group 3. CONCLUSION: The PCL scaffold coated with bone marrow seems to be a material that effectively provides osteoinduction with formation of new bone. Long-term results at 12 months are still pending.

Absorbable Implants↗
PubMed2001

[Long-term follow-up of 37 patients with retrofixation of the temporomandibular joint disk 1987-1995].

Between January 1986 and December 1995 64 patients with anterior disc displacement were operated on, the technique being disc retrofixation. Follow-up of 37 patients was possible. Successful treatment was determined using the following criteria: one single operation, the clinical examination and the patient's opinion. The operative treatment was considered as unsuccessful if the patient had to undergo more than one operation or if, postoperatively, the clinical symptoms remained unchanged or even increased. 6 out of 37 patients were operated on twice or three times, another four patients postoperatively complained of unchanged or increased clinical symptoms. Using these criteria, disc retrofixation was ineffective in 30%. Using the correct anatomic position as an additional criterion of effective treatment, unsuccessful retrofixation would be even more than 30%. As a consequence we no longer recommend this technique.

Adolescent↗
PubMed2001

Endoscopically assisted Le Fort I osteotomy.

OBJECTIVES: A new technique of the Le Fort I osteotomy using endoscopic techniques through limited approaches has been evaluated. PATIENTS: This technique was first carried out successfully in a study on six cadavers. Thereafter we performed endoscopically assisted Le Fort l osteotomy in two patients. METHODS: Four vertical incisions were used in the vestibule (paranasally and posteriorly) as approaches. The endoscope allowed direct visualization of the osteotomy of the maxilla including the pterygomaxillary junction. The osteotomies could be accomplished with a straight 4 mm osteotome for medial and lateral antral walls and nasal septum and a curved osteotome for the pterygomaxillary junction. RESULTS: The procedures were successful. The descending palatal arteries could be preserved in all cases as a result of endoscopic control. Rigid fixation of the downfractured maxillae was carried out using self-drilling titanium screws and plates. CONCLUSION: Endoscopic visualization allowed safe osteotomy of the medial antral wall preserving the descending palatal artery in all cases and hence less bleeding. Postoperative oedema and swelling in the two clinical cases was definitely reduced when compared with the conventional technique. The time needed for these first two clinical cases was approximately 1 h 30 min, i.e., about 30 min more than with the open technique. Further experience and experimental work, and refinements in technique will help to improve this procedure in its clinical application.

Adult↗
PubMed2001

Repair of composite zygomatico-maxillary defects with free bone grafts and free vascularized tissue transfer.

INTRODUCTION: Three-dimensional repair of the zygomatico-maxillary defect calls for an elaborate technique to achieve facial symmetry and correct globe position. We present a technique, which combines the use of a free vascularized soft tissue flap and free bone grafts for repair of composite zygomatico-maxillary defects. PATIENTS: Three patients that underwent radical resection of the maxilla and the zygoma have undergone facial reconstruction using this technique. The mean follow up was 9 months. METHODS: The key points of this technique are: (1) precise reconstruction of the zygomatico-maxillary complex including the orbit; (2) creation of a skeletal framework for canthopexy and suspension of the free flap; (3) repair of through-and-through soft tissue defects with a folded musculocutaneous free flap; and (4) simultaneous harvesting and reconstruction using two surgical teams to reduce the duration of surgery. RESULTS: Reconstruction of the zygomatico-maxillary complex could be successfully accomplished in a single surgical procedure. CONCLUSION: This paper presents a method of repairing zygomatico-maxillary defects with free bone grafts and vascularized soft tissue. However, this concept has yet to be reviewed in the long term.

Aged↗
PubMed2000

[New possibilities for reconstructing extensive jaw defects with prefabricated microvascular fibula transplants and ITI implants].

The reconstruction of extensive jaw defects is frequently only possible with microvascular bone flaps. Here we are presenting an operative technique using prefabricated fibular flaps and osseointegrated implants. In a first operation, the fibula is prepared with implants, split skin graft, and a nonresorbable membrane. The jaw defect is reconstructed 6 weeks later and can be treated directly with a prosthesis thanks to osseointegrated implants. The technique is described with reference to 5 patients already operated according to this technique and the initial findings are evaluated.

Adult↗
PubMed1997

Fluoroaluminate induces pertussis toxin-sensitive protein phosphorylation: differences in MC3T3-E1 osteoblastic and NIH3T3 fibroblastic cells.

Fluoride is an acknowledged bone-forming agent that may act through stimulation of osteoblast proliferation. Fluoride's action on osteoblasts and bone is potentiated by aluminum, which can form a complex with fluoride (fluoroaluminate) and activate heterotrimeric G proteins. Here we examined signaling pathways activated by fluoroaluminate in MC3T3-E1 osteoblastic and in NIH3T3 fibroblastic cells. In MC3T3-E1 cells, fluoroaluminate induced a decrease in cAMP levels and an increase in MAP and p70 S6 kinase phosphorylations. These responses were partially or completely prevented by pertussis toxin, an inhibitor of G alpha i proteins. In NIH3T3 cells, fluoroaluminate induced weaker tyrosine and MAP kinase phosphorylations. Fluoroaluminate, but not PDGF, induced a long-lasting tyrosine phosphorylation of a 130 kDa protein only in MC3T3-E1 cells. The expression of G alpha i2, but not of G alpha s and G alpha q/11 proteins was about 10-fold higher in MC3T3-E1 cells. Thus, different signaling in osteoblastic and fibroblastic cells may be due to differential expression of G alpha i proteins and tyrosine kinase substrates and could underlie fluoride's pharmacological action in bone.

3T3 Cells↗
PubMed1996

Differences in binding of PI 3-kinase to the src-homology domains 2 and 3 of p56 lck and p59 fyn tyrosine kinases.

Two T cell-specific src-family tyrosine kinases, p56 lck (lck) and p59 fyn (fyn), are implicated in regulating PI 3-kinase activity in response to interleukin-2 (IL-2), a cytokine that induces T cell proliferation. The src- homology domains 3 (SH3) of src-family kinases can directly interact with the PI 3-kinase regulatory subunit p85 and this may be a mechanism to regulate PI 3-kinase activity. In order to understand the mode of PI 3-kinase activation by the IL-2 receptor, we examined the association of PI 3-kinase to SH2 and SH3 domains of lck and fyn in IL-2-dependent kit 225 cells. The fyn SH3 domain bound more PI 3-kinase and its p85 subunit than the lck SH3 domain, while the lck SH2 domain bound more PI 3-kinase than the fyn SH2 domain. None of these interactions were regulated by IL-2. Low binding of PI 3-kinase to the lck SH3 domain was not observed in IL-2-independent Jurkat T cells. Thus, SH3 and SH2 domains of lck and fyn bound different amounts of PI 3-kinase, a feature that was dependent on a T cell type, but was not influenced by IL-2.

Amino Acid Sequence↗
PubMed1989

Catheter ablation of ventricular tachycardia using defibrillator pulses: electrophysiological findings and long-term results.

Catheter ablation of ventricular tachycardia (VT) was attempted in 24 patients (mean age 49 +/- 15.1 years) with a history of recurrent sustained VT resistant to previous antiarrhythmic drug therapy. 14 patients (58.3%) had also failed to respond to long-term administration of amiodarone alone and in combination with class I antiarrhythmic drugs. Endocardial catheter mapping during induced or spontaneous VT and/or pacemapping were performed to identify the site of origin of VT. Direct-current high-energy anodal shocks were delivered from a conventional cardioverter with stored energies of 100, 200 or 400 J via the distal electrode of conventional catheters. A total of 139 shocks was delivered during the ablation procedure. One patient died from wall perforation. Within 1 week of ablation, nine patients developed spontaneous recurrences of monomorphic sustained VT, identical to the clinical VT, and one patient developed a VT with a new morphology. In addition, four patients had a recurrence of their clinical VT after several weeks. In seven of 14 patients with spontaneous recurrences after the first ablation procedure and in three patients in whom VT was again inducible at the end of the first week, a second ablation procedure was performed. One patient with inducible VT after the first and second ablation sessions was given a third ablation procedure, and was discharged from hospital on anti-arrhythmic drugs which were successful despite being previously ineffective. After a mean follow-up period of 14.1 +/- 9.1 months, there were no spontaneous recurrences of sustained VT in 17 patients (71%) (nine without antiarrhythmic drugs and eight on antiarrhythmic drugs). In the remaining patients, incessant non-sustained VT (n = 2) or recurrent sustained VT (n = 2) occurred, and two patients died suddenly (at 2 and 21 months). There was no correlation between catheter mapping data or the results of pre-discharge electrophysiological study and clinical outcome during long-term follow-up. Complications related to catheter ablation included pulmonary oedema, cardiac tamponade, femoral artery occlusion, multiple episodes of ventricular tachycardia/fibrillation and thrombus formation, each in one patient (major complications; n = 7,29.1%), as well as transient third degree AV block, transient right or left bundle branch block, transient marked ST elevation or transient atrial tachycardia (minor complications; n = 8, 33.3%). The results suggest that catheter ablation might become an effective procedure for the non-pharmacological treatment of sustained VT.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1985

[Somatosensory evoked potentials (SEP) by isoflurane and enflurane in cardiosurgical interventions].

In the order to gain further insight into the sensory nervous pathways during enflurane- and isoflurane anaesthesia, two different concentrations (1 and 2 vol.%) of the anaesthetics were given to patients during extracorporeal circulation in normothermia and normocarbia, while somatosensory-evoked potentials (SEP) were recorded. As SEP-changes either reflect a change in functional integrity of the sensory nervous pathways (amplitude suppression) and a change in the speed of conduction (latency changes), the central effects of the volatile anaesthetics could be more fully evaluated. Isoflurane as well as enflurane induced a concentration-related change in latency especially of the late N100-component. However, in contrast to isoflurane administration the isomer enflurane in the high concentration range (2 vol.%) induced an increase of amplitudes of the early N20 and late N100-peak. Such an increase in amplitudes is interpreted as a disinhibition of medullary inhibitory centres, a possible premonitory sign of epileptogenic cortical activity, which already had been observed by various investigators.

Afferent Pathways↗