Biomedical subjects

C Wimmer

Publications and source records attributed to C Wimmer.

At least 19 recordsLinked to original sources

PubMed2005

Partial photoionization cross sections and angular distributions for double excitation of helium up to the N = 13 threshold.

Partial photoionization cross sections sigmaN(Egamma) and photoelectron angular distributions betaN(Egamma) were measured for the final ionic states He+ (N > 4) in the region between the N = 8 and N = 13 thresholds (Egamma > 78.155 eV) using the cold target recoil ion momentum spectroscopy technique (COLTRIMS). Comparison of the experimental data with two independent sets of theoretical predictions reveals disagreement for the branching ratios to the various HeN(+) states. The angular distributions just below the double ionization threshold suggest an excitation process for highly excited N states similar to the Wannier mechanism for double ionization.

Journal Article↗

PubMed2004

Experimental observation of interatomic coulombic decay in neon dimers.

Recently Cederbaum et al. [Phys. Rev. Lett. 79, 4778 (1997)]] predicted a new decay channel of excited atoms and molecules termed interatomic Coulombic decay (ICD). In ICD the deexcitation energy is transferred via virtual photon exchange to a neighboring atom, which releases it by electron emission. We report on an experimental observation of ICD in 2s ionized neon dimers. The process is unambiguously identified by detecting the energy of two Ne1+ fragments and the ICD electron in coincidence, yielding a clean, background free experimental spectral distribution of the ICD electrons.

Journal Article↗

PubMed2004

Comparison of conventional versus minimally invasive extraperitoneal approach for anterior lumbar interbody fusion.

The purpose of the study was to compare conventional versus minimally invasive extraperitoneal approach for anterior lumbar interbody fusion (ALIF). Fifty-six consecutive patients with spondylolisthesis, lumbar instability, or failed back syndrome were treated with ALIF between 1991 and 2001. The patients were retrospectively evaluated and divided in two groups: Group 1, consisting 33 patients, was treated with ALIF using the conventional retroperitoneal approach, and Group 2, consisting of 23 patients, was operated with the minimally invasive muscle-splitting approach for ALIF. The groups were comparable as regards age, indication of fusion, and diagnosis. All patients in both groups had fusion with autologous iliac crest grafts and posterior instrumentation with posterolateral fusion in the same sitting. Clinical evaluation was done by two questionnaires: the North American Spine Society (NASS) Lumbar Spine Outcome Assessment Instrument and the Nottingham Health Profile (NHP). Fusion rate was evaluated radiologically. Mean clinical follow-up was 5.5 years. There was no statistical difference in the occurrence of complications with both approaches nor with the fusion rates of 92% in group 1 and 84% in group 2 respectively. The minimally invasive extraperitoneal approach for ALIF was associated with significantly less intraoperative blood loss, operation time, and length of the skin incision. In addition, this approach showed significant improvement in postoperative back pain in comparison to the conventional approach for ALIF.

Adult↗

PubMed2004

Infection of a total hip arthroplasty with Prevotella loeschii.

Infection is a serious complication of total hip replacement. It has been proposed that 6% of all infections after total hip arthroplasty may be of dental origin through hematogenous spread. However, no conclusive evidence that the mouth is a definitive source for infection of a total hip replacement has been reported. In the current case, Prevotella loeschii, a pigmented bacteroides species was identified in a total hip replacement. Prevotella loeschii is an organism which exclusively inhabits the dental region. Hematogenous spread of Prevotella loeschii may occur after penetration of the mucosal barrier in cases of endodontic or periodontic lesions, pericoronitis, or complications of tooth extraction. The involvement of Prevotella loescheii in an infection in a patient who had a total hip arthroplasty is strong evidence for the mechanism of a hematogenous infection from a dental source.

Adult↗

PubMed2003

Contamination during removal of cement in revision hip arthroplasty. A cadaver study using ultrasound and high-speed cutters.

Instruments used in surgery which rotate or vibrate at a high frequency can produce potentially contaminated aerosols. Such tools are in use in cemented hip revision arthroplasties. We aimed to measure the extent of the environmental and body contamination caused by an ultrasound device and a high-speed cutter. On a human cadaver we carried out a complete surgical procedure including draping and simulated blood flow contaminated with Staphylococcus aureus (ATCC 12600). After cemented total hip arthroplasty, we undertook repeated extractions of cement using either an ultrasound device or a high-speed cutter. Surveillance cultures detected any environmental and body contamination of the surgical team. Environmental contamination was present in an area of 6 x 8 m for both devices. The concentration of contamination was lower for the ultrasound device. Both the ultrasound and the high-speed cutter contaminated all members of the surgical team. The devices tested produced aerosols which covered the whole operating theatre and all personnel present during the procedure. In contaminated and infected patients, infectious agents may be present in these aerosols. We therefore recommend the introduction of effective measures to control infection and thorough disinfection of the operating theatre after such procedures.

Aerosols↗

PubMed2002

[Surgical treatment of idiopathic scoliosis and juvenile kyphosis].

Indication for operative treatment of idiopathic scoliosis and juvenile kyphosis is mainly cosmetic. There is also a higher incidence of pain in scoliosis patients, and reduced pulmonary function in severe deformity, especially in severe deformities present at the age of 5 years (early onset). Scoliotic curves of less than 30 degrees will not progress in adults, whereas curves of 50-75 degrees will further progress a mean of 25 degrees during 40 years. Progression in adults with juvenile kyphosis is not well documented. Operative treatment aims to stop progression, to control spinal growth, or to perform correction and fusion by spinal instrumentation and bone grafts. These goals can be achieved either by an anterior, a posterior, or a combined approach. Correction principles are compression, distraction, derotation and translation. The forces applied by correction are transferred by fixation devices (pedicle screws, anterior screws, hooks, sublaminar wires) to the spine. The higher correction forces are, the higher is the correction achieved, but also the risk of fracture and torn out implants. Mobilisation reduces rigidity and allows to achieve a better correction with equal forces. The best mobilisation techniques are disc excision, facet joint removal, and techniques to mobilise the thorax.

Adult↗

PubMed2002

Retrograde injection of a nutrient vein with cement in cemented total hip arthroplasty.

An 80-year-old woman received a cemented total hip arthroplasty. The surgery was performed without intraoperative complications. Postoperative radiographs and a computed tomography scan revealed a nutrient vein perforating the femur, which was retrogradely filled with cement. An abdominal and thoracic computed tomography scan showed no further dissemination of cement.

Aged↗

PubMed2001

Environmental and body contamination through aerosols produced by high-speed cutters in lumbar spine surgery.

STUDY DESIGN: A cadaver study to evaluate contamination in the operating room through the use of a high-speed bone cutter. OBJECTIVES: To determine the grade of contamination of animate and inanimate objects through an aerosol intraoperatively, produced by a high-speed cutter during lumbar laminectomy. SUMMARY OF BACKGROUND: In spinal surgery, high-speed cutters are used that produce an aerosol consisting of a mixture of irrigation solution, blood, and tissue debris. Such aerosols can be contaminated with potential pathogens. The surgical personnel and the environment are therefore exposed to a contamination risk. METHODS: Laminectomies at three points (L2-L4) were performed on a human cadaver using a high-speed cutting device. The aerosol produced by the irrigation solution was contaminated with Staphylococcus aureus ATCC 12600. To detect the contamination of the environment and of the surgical team, surveillance cultures were used. RESULTS: By air sampling, staphylococci were detected in the operating room at an extension of 5 by 7 m. The surgical team showed extensive face and body contamination with S. aureus. Despite protection by a barrier drape, similar contamination was observed on both the cadaver's head and the anesthesiologist. CONCLUSIONS: The use of high-speed cutters in spinal surgery produces an aerosol that can be contaminated with blood-borne pathogens from infected patients. This aerosol is spread over the whole surgical room and contaminates the room and all personnel present. It is therefore critical to ensure that effective infection control measures are performed, not only by the surgeons but by everyone present in the operating room. The room itself must be sufficiently disinfected after such procedures.

Aerosols↗

PubMed2001

Molecular mass, stoichiometry, and assembly of 20 S particles.

N-Ethylmaleimide-sensitive factor (NSF), soluble NSF attachment proteins (SNAPs), and SNAP receptor (neuronal SNARE) complexes form 20 S particles with a mass of 788 +/- 122 kDa as judged by scanning transmission electron microscopy. A single NSF hexamer and three alpha SNAP monomers reside within a 20 S particle as determined by quantitative amino acid analysis. In order to study the binding of alpha SNAP and NSF in solution, to define their binding domains, and to specify the role of oligomerization in their interaction, we fused domains of alpha SNAP and NSF to oligomerization modules derived from thrombospondin-1, a trimer, and cartilage oligomeric matrix protein, a pentamer, respectively. Binding studies with these fusion proteins reproduced the interaction of alpha SNAP and NSF N domains in the absence of the hexamerization domain of NSF (D2). Trimeric alpha SNAP (or its C-terminal half) is sufficient to recruit NSF even in the absence of SNARE complexes. Furthermore, pentameric NSF N domains are able to bind alpha SNAP in complex with SNAREs, whereas monomeric N domains do not. Our results demonstrate that the oligomerization of both NSF N domains and alpha SNAP provides a critical driving force for their interaction and the assembly of 20 S particles.

Amino Acid Sequence↗

PubMed2001

Sequential involvement of p115, SNAREs, and Rab proteins in intra-Golgi protein transport.

Delivery of transport vesicles to their receptor compartment involves tethering, priming, and fusion. Soluble NSF attachment protein-alpha (alphaSNAP) mediates the disruption of SNAREs by N-ethylmaleimide sensitive factor (NSF) and was employed to determine the hierarchy of proteins responsible for intra-Golgi protein transport. The N-terminal 23 amino acids of alphaSNAP are necessary for SNARE binding. The antibody 2F10 recognizes this SNARE interaction domain of alphaSNAP and inhibits intra-Golgi protein transport reversibly. This antibody was applied to modify the transport assay to determine the protein requirements relative to the action of alphaSNAP and NSF. We found that 1) p115 acts independently of alphaSNAP and NSF, 2) SNAREs are required after tethering and interact selectively after activation by alphaSNAP and NSF, and 3) Rab proteins act after SNARE activation and before fusion.

Amino Acid Sequence↗

PubMed2001

Multisegmental pneumatocysts of the lumbar spine mimic osteolytic lesions.

Circumscribed radiolucencies within the vertebral bones can be due to a variety of changes including benign and malignant tumours or tumour-like lesions. Radiolucencies due to degenerative intraosseous pneumatocyst are very uncommon but have to be taken into the differential diagnosis in well-circumscribed lytic lesions of the vertebral bodies. We describe the first case of multisegmental pneumatocysts in the lumbar spine mimicking osteolytic lesions. On computed tomography, the air-equivalent attenuation values of the lesions and the close vicinity to the degenerated vertebral endplates with vacuum phenomenon led to the correct diagnosis.

Aged↗

PubMed2001

Aerosols produced by high-speed cutters in cervical spine surgery: extent of environmental contamination.

High-speed cutters are used in the surgery of the cervical spine. Such high-speed devices can produce an aerosol cloud. As a patient can be a reservoir for pathogens, with aerosol-borne paths of transmission, such an aerosol has to be seen as a potential risk of infection for health care professionals present during the surgery and for patients if micro-organisms are transferred through the medical personnel. The study was performed in order to measure the extension of environmental and body contamination through contaminated aerosols produced by a high-speed cutter. Three laminectomies (C4-C6) were performed on an intact human cadaver with a high-speed 0.6-mm ball cutter. A complete surgical setup was arranged, including surgical draping and a barrier drape to the anesthesiologist's workplace. Body and environmental contamination was detected by the use of surveillance cultures. The irrigation solution was artificially contaminated with Staphylococcus aureus ATCC 12600. Following the surgery, staphylococci were detected in the operating room at an extension of 5x7 m. Everybody showed extensive face and body contamination with Staphylococcus aureus. The study showed that the use of high-speed cutters in surgery of the cervical spine produces an aerosol cloud that is spread over the whole surgical room and contaminates the theater and all personnel present. Such aerosols can be contaminated with pathogens if the patient was infected or colonized. Therefore, sufficient protective measures have to be recommended for everyone present in the operating room during such surgeries. In addition, efficient disinfection of the room and all mobile equipment is necessary after each surgery involving high-speed cutting devices.

Aerosols↗

PubMed2001

[A patient with acoustic neuroma--The reason for the functional disorder of his inner ear?].

BACKGROUND: Acoustic neuroma is one of the classic causes of retrocochlear hearing disorders. Auditory brainstem response (ABR) testing with a sensitivity of about 90 % in the diagnosis of acoustic neuroma plays an important role as a screening method. CASE REPORT: A patient suffering from an acute, unilateral sensorineural hearing loss with tinnitus recovered for a short period of time after being treated with low density lipoprotein (LDL-) apheresis improving hemorheology. Surprisingly, the reason for the sudden hearing loss was a tumor in the cerebellopontine angle with a maximum diameter of 2 cm, which was detected by magnetic resonance imaging (MRI). Auditory brainstem response testing (ABR), audiovestibular tests and other standard tests were negative concerning this diagnosis. There was no previous evidence for an acoustic neuroma in all investigations of cochlear disfunction except MRI. CONCLUSIONS: The acoustic neuroma caused a compression of the labyrinthine artery in the inner auditory canal resulting in an acute unilateral hearing loss with tinnitus. Low Density Lipoprotein-apheresis was able to achieve a short term improvement of blood supply to the inner ear. Thus the compression of the labyrinthine artery caused by an acoustic neuroma could be compensated for the duration of about one week. Within this time the effect of LDL-apheresis decreased more and more. After a sudden unilateral hearing loss an acoustic neuroma must be ruled out even if the retrocochlear testing by ABR primarily shows no prolonged interpeak latency.

Adult↗

PubMed2001

Excessive heat generation during cutting of cement in the Robodoc hip-revision procedure.

The ROBODOC system is a promising new method for removing cement with high-speed milling. Heat is generated during the milling process. This study was designed to measure temperatures in the cutting area, and to assess the risk of heat injury and the effectiveness of irrigation. We measured temperatures at the bone-cement cutting area in three experimental settings, two involving the proximal area comprising a cement mantle, and one the distal cement plug beneath the prosthesis. Without cooling facilities, a mean temperature of 94 degrees C was measured in proximal areas. However, this could effectively be reduced below 70 degrees C with irrigation. In the area of the distal cement plug, we measured a mean temperature of 172 degrees C without irrigation. In this area, the integrated irrigation system with an additional high-flow irrigation system could not guarantee cooling to an acceptable temperature of below 70 degrees C since the irrigation stream was impeded by the cutter in the narrow cavity. We need an integrated irrigation device that guarantees continuous cooling at the cutting interface in front of the cutter.

Arthroplasty, Replacement, Hip↗

PubMed2001

Treatment of idiopathic scoliosis with CD-instrumentation: lumbar pedicle screws versus laminar hooks in 66 patients.

We studied whether the pedicle screw is better than laminar hooks for fixation of the lumbar spine in the treatment of idiopathic scoliosis. 66 consecutive patients with idiopathic scoliosis (King I and II) were studied retrospectively. Group S included 33 patients (25 females) treated with pedicle screws. Their mean age at operation was 17 (13-54) years. Group H included 33 patients (30 females) treated exclusively with hooks. Their mean age at operation was 16 (1140) years. The preoperative mean angles of the thoracic curve in group S was 66 (42.115) degrees, and in group H 65 (42-121) degrees. The lumbar curve averaged 46 (20-85) degrees in group H and 53 (33-86) degrees in group S. All patients were fused only posteriorly with Cotrel-Dubousset instrumentation and an autogenic bone graft. The mean follow-up time was 4 (2-7) years. Mean correction of the thoracic curve was 45% in group S and 50% in group H. The lumbar curve was corrected by 50% in group S and 51% in group H. Loss of correction of the thoracic curve occurred in 5% in group S and 6% in group H and of the lumbar curve in 3% in group S and 10% in group H (p = 0.04). Group S better maintained the correction of the lateral tilt of the uninstrumented segment adjacent to the fusion (p = 0.04). Derotation, according to Perdriolle, in the distal segment adjacent to the fusion was 6% in group S and 2% in group H. We found no difference between correction of the thoracic and lumbar curves using pedicle screws and laminar hooks in the lumbar spine. Pedicle screws better maintained the correction of the lumbar curve and the lateral tilt in the distal segment adjacent to fusion.

Adolescent↗

PubMed2001

Knee pain caused by a fiducial marker in the medial femoral condyle: a clinical and anatomic study of 20 cases.

After 2-pin-based ROBODOC hip arthroplasty procedures, 10 of 18 patients reported persistent severe pain at the site of pin implantation in the medial femoral condyle. In a cadaver study, we found that the infrapatellar branch of the saphenous nerve, the saphenous nerve and the anterior cutaneous branches of the femoral nerve had been injured by the pins. At least one of these nerves was injured in 11 of the 20 specimens examined. Our findings indicate that the knee-pain may be partly caused by injuries to these nerves.

Aged↗

PubMed2001

Radiographic assessment in total knee arthroplasty.

Sixty-five total knee arthroplasties were evaluated by the Knee Society Radiological Evaluation System which was developed to encourage uniform reporting of the results of total knee arthroplasty. All patients were examined by three independent experienced radiologists 8.9 years after surgery (range, 3-16 years) to analyze the interobserver variability. For measurement of angles, high interobserver correlation was calculated for the prosthetic component angles and the femorotibial shaft angle. The comparison of the means indicated no significant differences except for the femorotibial shaft angle. For measurement of radiolucent lines, interobserver correlation was low for all components. The differences of the means were significantly different for all components. The results of interobserver variability of the patellar evaluation revealed high interobserver correlation for the patellar angle and for patellar subluxation and dislocation evaluation. For assessment of patellar mediolateral and superoinferior displacement, a low interobserver correlation was found. For radiographic assessment of total knee arthroplasty, the measurement of angles, including alpha, beta, femorotibial shaft angle, sagittal femoral and tibial component angle, patellar angle, and patellar subluxation and dislocation evaluation are recommended. The method of assessing radiolucent lines should be reconsidered.

Aged↗

PubMed2001

Contamination risk of the surgical team through ROBODOC's high-speed cutter.

During cutting of the femoral cavity in the ROBODOC procedure, an aerosol cloud of irrigation fluid, blood, and tissue debris was seen. This cloud potentially is contaminated with bacterial and viral vectors, which is an infection risk for the surgical team. A flat and a ball cutter were tested in four standard situations macroscopically with a colored solution. In a second experiment, the cutter was exposed to a fluid contaminated with Staphylococcus aureus, and bacterial room contamination was detected using standard cultures. The aerosol cloud was seen in a 6 x 3.6-m area. Extension and concentration varied, depending on the irrigation situation. ROBODOC's high-speed cutter produces an aerosol cloud in an area in which all members of the surgical team are affected. Sufficient protection is necessary for everyone in the operating room.

Equipment Contamination↗