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K Weise

Publications and source records attributed to K Weise.

At least 19 recordsLinked to original sources
PubMed2006

Bayesian decision threshold, detection limit and confidence limits in ionising-radiation measurement.

Based on Bayesian statistics and the Bayesian theory of measurement uncertainty, characteristic limits such as the decision threshold, detection limit and limits of a confidence interval can be calculated taking into account all sources of uncertainty. This approach consists of the complete evaluation of a measurement according to the ISO Guide to the Expression of Uncertainty in Measurement (GUM) and the successive determination of the characteristic limits by using the standard uncertainty obtained from the evaluation. This procedure is elaborated here for several particular models of evaluation. It is, however, so general that it allows for a large variety of applications to similar measurements. It is proposed for the revision of those parts of DIN 25482 and ISO 11929 that are still based on conventional statistics and, therefore, do not allow to take completely into account all the components of measurement uncertainty in the calculation of the characteristic limits.

Algorithms↗
PubMed2006

[Risk profiling of postoperative complications in 17,644 total knee replacements].

AIM: Postoperative complications following primary total knee replacement performed between 2000 and 2002 were assessed to determine perioperative patient- and procedure-related risks associated with the procedure. METHODS: For this analysis, the data collected during postoperative hospitalization for 17,644 total knee arthroplasties were assessed. The analysis included two steps. First, using logistic regression, we identified and quantified significant risk factors for the occurrence of general postoperative complications. Second, univariate analysis was utilized to qualitatively and quantitatively analyze the influence of these significant risk factors on the occurrence of major complications (hematoma, cardiovascular complication, deep venous thrombosis, pulmonary embolism, joint infection, and pneumonia). RESULTS: General postoperative complications were reported in 11.3%. Major postoperative complications occurred in 7.2% with hematoma in 2.9%, cardiovascular complications in 1.8%, deep venous thrombosis in 1.2%, pulmonary embolism in 0.2%, joint infection in 0.8%, and pneumonia in 0.3%. Patient-related risk factors such as age, surgery time, gender, high ASA classification as well as procedure-related risk factors such as allogeneic blood transfusions and lateral release significantly increased the rate of postoperative complications. Males were more prone to hematoma, joint infection, and pneumonia in the immediate postoperative course than females, who were more in danger of developing deep venous thrombosis. Allogeneic blood transfusions increased the risk for postoperative hematoma, infection, and cardiovascular complication. Regional anesthesia was shown to decrease the risk for the occurrence of postoperative deep venous thrombosis and pulmonary embolism. CONCLUSIONS: Postoperative complications in total knee replacement are increased in males and elder patients. Increased time of surgery and allogeneic blood transfusions also represent important risk factors for postoperative complications following primary total knee replacement.

Age Factors↗
PubMed2006

[CT-based assessment score after ventral spondylodesis for thoracolumbar spine fracture].

BACKGROUND: Dorsoventral stabilization is a common procedure to treat thoracolumbar spine fractures. Especially in respect of the evaluation of alternative procedures to autogenous bone graft, a standardized evaluation score for ventral spondylodesis is necessary. PATIENTS AND METHODS: In a group of 44 patients a follow-up CT scan was evaluated with a standardized scoring system by four different independent evaluators (a trauma surgeon, an orthopedic surgeon, and two radiologists). The score is based on the morphologic classification of the region between graft and vertebral body. It allows a classification of the spondylodesis as sufficient, partial, and not sufficient. RESULTS: The statistical evaluation of the classification of the different evaluators shows very good interobserver agreement in monosegmental fusion and good agreement in bisegmental fusion. CONCLUSION: The demonstrated score is easy to handle, does not need special equipment for CT scans, and shows good interobserver agreement in the classification of spinal fusion after ventral spondylodesis for thoracolumbar spine fracture.

Adolescent↗
PubMed2006

[Cartilage repair in the knee joint].

Full thickness defects of the articular cartilage in the knee joint have lower regenerative properties compared to chondral lesions of the ankle. In order to avoid early osteoarthritis, symptomatic articular cartilage defects in younger patients should undergo biological reconstruction as early as possible. There are different surgical procedures available to achieve a biological resurfacing of the articular joint line. Numerous animal experiments and clinical studies have shown that early biological reconstruction of circumscribed cartilage defects in the knee is superior to a conservative or delayed operative treatment. This effect refers not only to the defect healing but also to the elimination of changes following secondary osteoarthritis. The different surgical procedures can be differentiated concerning the various indications and the final outcome. Additional malalignment, meniscus tears, and/or ligament instabilities should be treated simultaneously together with the cartilage resurfacing. The mid- and long-term results of the different current techniques are promising, but further modifications and improvements are needed.

Arthroplasty↗
PubMed2006

[Value of three-dimensional ultrasound and MRI in meniscal lesions].

BACKGROUND: The aim of this prospective study was the evaluation of preoperative three-dimensional ultrasound in detecting meniscal lesions compared to preoperative MRI. METHODS: A total of 34 patients with clinical signs of meniscal lesions were examined preoperatively (11.7 MHz linear transducer) using the 3-D technique. Before ultrasound, MRI was performed, the results of which were unknown to the ultrasound examiner. The basis of the MRI result was the radiologist's written report. Arthroscopically the meniscal situation was noted and taken as reference. RESULTS: At arthroscopy there were 10 lateral meniscal lesions at different locations and 47 medial meniscal lesions at different locations. The sensitivity (0.5-0.78) and specificity (0.75-0.95) of both imaging methods were overall comparable. CONCLUSION: Ultrasound with the three-dimensional technique and high-resolution transducer in the hands of an experienced operator gives results comparable to the MRI interpretation by a general radiologist in detecting meniscal lesions.

Adolescent↗
PubMed2006

Acute musculoskeletal infection: comparison of different methods for intraoperative bacterial identification.

PURPOSE OF THE STUDY: Various techniques are used for detection of pathogens in musculoskeletal infection. These methods differ with respect to reliability and ease of handling. A prospective study was performed to evaluate the efficacy of three intraoperative techniques. MATERIAL AND METHODS: In 20 cases (18 patients) with clinically confirmed acute musculoskeletal infections, intraoperative collected swab samples, tissue samples and fluid samples injected into standard blood culture vials were used for microbiological diagnosis. Identification of bacteria, time necessary for detection and ease of handling during surgery was evaluated. RESULTS: In 19 cases bacterial growth was demonstrated using either intraoperative swabs or blood culture technique (95% sensitivity), whereas 18 tissue biopsies were positive (90% sensitivity. 27 bacterial species were isolated. In 18 instances for the swab technique, 14 instances for the tissue biopsy and 4 operations for the blood culture vials, ease of handling was rated as excellent. DISCUSSION: The study demonstrated differences between the three tested methods with respect to ease of handling. With respect to the number of detected organisms and time for their detection there are no significant differences. These last findings are in contrast to of the results of other authors. The reason for this could be that during operative dissection an accurate and specific collection of specimens from the acute deep infected soft tissues and bones independent from the type of surgical procedure is possible. Therefore, even with the swab method a high amount of microorganisms can be recovered. Especially for intraarticular infections, fluid samples injected into standard blood vials is a practical method for the surgeon. In acute musculoskeletal infections other than joint infections, there is less benefit for the blood culture vials. CONCLUSION: Intraoperative swab technique yields valid results comparable to other techniques and is an accurate technique for detection of pathogens from acute musculoskeletal infections. Key words: implant, infections, bacteriological techniques, comparative study.

Acute Disease↗
PubMed2005

Fractures of the distal tibia treated with closed reduction and minimally invasive plating.

INTRODUCTION: The treatment of fractures of the distal tibia can be problematical because of the thin soft-tissue covering. Bridging slide-insertion plate osteosynthesis is performed by indirect, axially correct reduction of the fracture and stabilization without opening the soft tissue at the fracture site. Stripping of the periosteum is thus avoided, the fragments remain integrated into the soft tissue, and healing occurs spontaneously by way of callus formation. MATERIALS AND METHODS: Seventy-one patients treated by slide-insertion plate osteosynthesis were followed up over at least 2 years. As would be expected in this anatomical region, the proportion of C fractures and fractures with concomitant soft-tissue damage was high. The majority of patients were treated by application of an external fixator on the day of the accident; the definitive osteosynthesis with the slide-insertion plate was performed at a later date after healing of the soft tissues. RESULTS: In 68 patients, fracture healing was achieved within 2 years. In 80% of the cases, the final X-ray follow-up showed no or tolerable axis deviations (<5 degrees) in the varus/valgus plane or in the recurvation/antecurvation plane. A deviation >10 degrees requiring a correcting osteotomy was found in only 1 patient. Postoperative complications were rare occurrences. Five patients required an additional cancellous bone graft to deal with inadequate bone healing. System-related complications (instability, malalignment) due to intraoperative technical errors only had to be corrected in revision operations in 2 patients. CONCLUSION: Closed reduction and minimally invasive plating offers the combined advantages of minimal soft-tissue damage with stable fracture fixation.

Adult↗
PubMed2005

[Significance and technique of autologous chondrocyte transplantation].

The bad risk for an early onset of osteoarthritis in the knee increases with the size of a cartilage defect. A collateral meniscus- or ligament-tear will enforce this hazard in addition. In order to avoid such a development, relevant full-thickness cartilage defects should be reconstructed biologically and attendant meniscus- or ligament-tears as well as varus- or valgus deformities should be treated. A number of studies, including some prospective-randomized trials, have shown that autologous chondrocyte transplantation (ACT) is the most reliable procedure for a surgical treatment of full-thickness cartilage defects larger than 4 cm (2) in adults. One disadvantage of ACT is the extensive approach to the joint and often a hypertrophy of the repair tissue. To solve these problems, some different biomaterials for a matrix-assisted ACT have been developed. The scaffold we use has a covering membrane upside and a collagen-sponge carrying the chondrocytes. By means of special surgical instruments a minimally invasive implantation is possible, reducing the side-effects of an extensive approach. Animal studies showed the regeneration of a hyaline cartilage using our described system. However, results of current clinical studies with the different scaffolds must be awaited before an universal application of matrix-assisted ACT can be recommended.

Adult↗
PubMed2005

Primary stability of various forms of osteosynthesis in the treatment of fractures of the proximal tibia.

The treatment of fractures of the proximal tibia is complex and makes great demands on the implants used. Our study aimed to identify what levels of primary stability could be achieved with various forms of osteosynthesis in the treatment of diaphyseal fractures of the proximal tibia. Pairs of human tibiae were investigated. An unstable fracture was simulated by creating a defect at the metaphyseal-diaphyseal junction. Six implants were tested in a uniaxial testing device (Instron) using the quasi-static and displacement-controlled modes and the force-displacement curve was recorded. The movements of each fragment and of the implant were recorded video-optically (MacReflex, Qualysis). Axial deviations were evaluated at 300 N. The results show that the nailing systems tolerated the highest forces. The lowest axial deviations in varus and valgus were also found for the nailing systems; the highest axial deviations were recorded for the buttress plate and the less invasive stabilising system (LISS). In terms of rotational displacement the LISS was better than the buttress plate. In summary, it was found that higher loads were better tolerated by centrally placed load carriers than by eccentrically placed ones. In the case of the latter, it appears advantageous to use additive procedures for medial buttressing in the early phase.

Biomechanical Phenomena↗
PubMed2004

Surface acoustic waves for the characterization of BN-coated fibres observed by Brillouin light scattering.

The observation of acoustic phonons located at the surface of uncoated fibres or guided in thin films deposited on fibres by Brillouin light scattering spectroscopy (BLS) is reported. The BLS technique is non-destructive and non-intrusive and is well applicable to non-planar sample geometries. Investigations were carried out on bundles of commercially available carbon fibres, in which a single fibre was 5 microm in diameter. With regard to the detected surface acoustic excitations, each fibre can be considered as an infinite halfspace owing to the large ratio of fibre diameter to wavelength. The shear modulus, which is highly relevant for the intended technical application, was determined by measurement of the Rayleigh mode phase velocity of the uncoated fibres. These fibre bundles were coated with boron nitride (BN) in a continuously driven thermal chemical vapour deposition (CVD) process using trimethyl borate and ammonia as precursors. In comparison to carbon, BN is expected to improve the mechanical properties of fibre-reinforced composites such as fracture toughness at high temperatures. The measured velocity dispersion of the Rayleigh mode of this film-on-substrate system permitted the comparison of the shear stiffness of the carbon fibre and of the BN film material. The results evidence the desired effect of a distinct stiffness reduction of the coated fibre relative to the uncoated fibre in the near-surface region. Additional information can be obtained on the homogeneity of the deposition across the whole fibre bundle.

Journal Article↗
PubMed2004

[Direct CT-arthrography versus direct MR-arthrography in chronic shoulder instability: comparison of modalities after the introduction of multidetector-CT technology].

PURPOSE: To evaluate the diagnostic accuracy of direct multidetector CT arthrography (CTA) and direct MR arthrography (MRA) in patients suffering from chronic shoulder instability. MATERIALS AND METHODS: Twenty-nine patients suffering from chronic shoulder instability were included into a prospective study. In all cases, the indication for direct CTA and arthroscopy was set by the orthopedic surgeon. Prior to the imaging procedures, 10 to 20 ml of a special combination of contrast media (including saline, Isovist(R) and Magnevist(R) in a relation of 125 : 125 : 1) was injected into the joint under sterile conditions. First, CTA was performed with a multidetector CT, with images reconstructed in the axial, semi-coronal and semi-sagittal planes. Thereafter, MRA was performed. Axial images were obtained using a T1-weighted, fat-saturated spin echo sequence and semi-coronal images using a T1-weighted FLASH-3D GRE sequence. The results of CTA and MTA were compared with results obtained from arthroscopy or arthrotomy. RESULTS: MRA was superior to CTA in the detection of labral lesions. The sensitivity of MRA was 96 % and the specificity 96 %, compared to a sensitivity of 76 % (p < 0.05) and specificity of 92 % for CTA. Both methods showed the same effectiveness concerning the assessment of capsule distension (sensitivity for both techniques: 91 %). CONCLUSIONS: MRA seems to be superior to CTA in the diagnostic workup of chronic shoulder instability even when using a multidetector CT technique.

Adolescent↗
PubMed2003

Comparative investigations of structure and properties of BCN coatings deposited by thermal and plasma-enhanced CVD.

Hard BCN films were deposited by chemical vapour deposition (CVD) on Si(100) substrates. TCVD (thermal activated) and PECVD (GD or RF microwave plasma-activated, respectively) were used. The films were analysed with respect to chemical state, composition, morphology and microstructure, oxidation behaviour and hardness. Wavelength dispersive X-ray spectroscopy (EPMA), infrared spectroscopy (IR), transmission electron microscopy (TEM), differential thermal analysis (DTA) and hardness evaluation were employed for film characterization. A correlation between deposition parameters and film composition, structure and hardness could be proved in every CVD process. Parallels between TCVD and PECVD films emerged in the case of chemical composition and the correlation between carbon content and hardness values. Considerable differences exist with regard to the microstructure, especially the texture of the films. Moreover in TCVD films the carbon is preferentially incorporated between the BN basal planes, whereas in PECVD films it is incorporated preferentially in as well as between the BN basal planes.

Journal Article↗
PubMed2003

[Distinctive features of the os naviculare pseudarthrosis vs the os naviculare accessorius].

We report on two cases in which the differential diagnosis between an os tibiale externum (os naviculare accessorius) and a post-traumatic pseudarthrosis of the os naviculare was subject to discussion.Both patients had suffered an acute trauma in the region of the middle foot and showed identical clinical symptoms. Conventional X-ray did not allow a definite classification of the diagnosis either.However, this was possible in both cases by virtue of typical signs evidenced by computed tomography and magnetic resonance imaging.

Adult↗
PubMed2003

[Cemented versus uncemented hip replacement--rational decision making using the BiCONTACT total hip system].

The BiCONTACT femoral stem has been developed as a modular system which is suitable for both cemented and uncemented implantation. A highly standardized procedure using an identical set of instruments for both modes of fixation ensures bone preservation. Primary stability is achieved by special design parameters. The cementless implants are coated proximally, thus facilitating osteointegration and proximal load transfer. Cemented stems provide an identical design but a smooth surface and are anchored by a homogenous cement mantle. The BiCONTACT stem is in use in the BG Trauma Center Tuebingen since 14 years and a consecutive series of 250 cases (series A) with uncemented implantation and of 250 cases (series B) with cemented implantation has been analyzed in two different prospective follow-up studies. Long-term survival after 11 years was 97.1 % (95 % confidence limits: 93.8 %-98.7 %) for series A, the follow-up rate was 99.2 %. For series B, the follow up-rate was also 99.2 %, survival estimate after 11 years was 97.5 % (95 % CI: 94.2 %-99.0 %).

Adult↗
PubMed2003

Long-term results with the BiCONTACT system--aspects to investigate and to learn from.

The BiCONTACT femoral stem for cementless fixation is being used without any technical modification after 15 years. The long-term results should be evaluated in this study. A consecutive series was continuously monitored in a prospective follow-up study. A survival analysis was performed, clinical results were rated according to the Harris score. There were 236 patients with 250 total hip replacements (THR); mean age at time of implantation was 58.2 years. Indications for THR included osteoarthritis (62.4%), dysplasia (16.8%), trauma (8.4%) and femoral-head necrosis (16.8%). Average time of follow-up evaluation was 8.9 years (range 7.4-10.7 years). At follow-up, 27 patients had died and two could not be located. Seven patients were revised--two for infection, one for recurrent dislocation, two for component undersizing with rapid subsidence, and one for aseptic loosening of a varus-malaligned stem; one radiologically well-fixed stem had been revised during acetabular revision. Survival estimate showed an overall survival rate of 97.1% after 11 years (confidence limits: 98.7% upper and 93.6% lower). Radiologically, tiny reactive lines (< 2 mm) were present in the distal zones of the femoral shaft, but no radiolucencies could be found in the proximal anchoring zone. Migration analysis with Ein-Bild-Röntgen-analyse/femoral component analysis (EBRA/FCA) demonstrated a very small amount of migration: in 31.0%, the overall migration was between 0.5 and 1 mm after 120 months; 8.5% had an absolute amount of subsidence exceeding 2 mm after 120 months (one case more than 3 mm). Mean subsidence was 0.2 mm after 3 months and 6 months, 0.3 mm after 12 months, and reached 0.5 mm after 10 years. An initial small amount of subsidence could be detected in 45.1%, and 15.5% had a late onset of subsidence. Continuous sinking could be found in 12.7%, while 26.8% had irregular patterns of migration. Clinical results were somewhat compromised by a higher-than-average rate of cup loosening (uncoated threaded cup). The average Harris hip score at follow-up was 84.3 points. Interestingly, no femoral osteolysis could be detected, even in cases with severe acetabular osteolyses, indicating sealing of the stem interface by tight osseointegration of the proximally-coated stem.

Arthroplasty, Replacement, Hip↗
PubMed2002

[Good long term results with a cemented straight femoral shaft prosthesis made of titanium].

A higher-than-average rate of aseptic loosening has been postulated to be associated with the combination of a titanium stem and bone cement. In this prospective follow-up study we therefore investigated our first consecutive series of 250 implantations of a cemented femoral shaft prosthesis made of titanium alloy (BiCONTACT((R)), Aesculap, Tuttlingen, Germany). Average time of follow-up evaluation was 9.7 years (range 8.7-10.3 years). At follow-up, mean patient age was 81 years; 89 patients with 93 hips have deceased and two could not be located. Follow-up rate was 98.7% for the patients still alive at time of follow-up evaluation. Five patients have been revised, two for infection and one for aseptic loosening of a varus-malaligned stem; two radiologically well-fixed stems had been revised during acetabular revision. Survival estimate showed a calculated cumulative survival rate of 97.5% after 11 years [confidence limits: 99.0% (upper) and 94.1% (lower)]. The average Harris hip score at time of follow-up was 82.25 points.Radiologically, signs of loosening could be detected in 3 stems: in one case varus malalignement deteriorated with time and in 2 cases osteolyses developed together with significant polyethylene wear. All 3 patients experienced only mild pain and revision had not been indicated so far. In conclusion, the long-term follow-up results with this cemented titanium femoral component are encouraging and are comparable to other successful cemented femoral components in primary total hip arthroplasty. No increased risk for aseptical loosening was associated to the combination of titanium and cement in this specific stem. Design parameters seem to play an important role in the development of aseptic loosening in cemented titanium stems.

Adult↗