Medical Library

[Screw-in Performance of Threaded Cups.]

INTRODUCTION: For threaded cups, cup diameter, the shape of the threads and the shape of the cup have a major influence on the screw-in performance. The designs of standard implants vary greatly, making it difficult to carry out comparative studies to provide clear-cut results on the effect of individual parameters on the insertion process. MATERIAL AND METHODS: 15 different prototype cups were manufactured for this study. Three sizes, three shapes and five thread designs were tested using artificial bone. Screw-in performance was measured with the slope of insertion torque before and after reaching the seating point, the torque at the seating point, the insertion angle and the change of slopes at the seating point. RESULTS: Modified trapezoid threads have the lowest insertion resistance and the clearest seating point as well as the most distinct change of slope at the seating point. Flat threads show lower insertion resistance and more increased slopes at the seating point than sharp threads. The slope of insertion torque before and at the seating point is higher for sharp threads in comparison to the other threads, the change of slop is however low. Larger cups show a higher insertion resistance. CONCLUSION: Screw-in performance is decisively influenced by the design of the threads. Modified trapezoid threads are the easiest to insert with excellent manual control, thus reducing the risk of intra-operative overturning. Flat threads also have a low screw-in resistance. Sharp threads have an unsatisfactory screw-in performance because the seating point cannot be \”felt\”.

Effenberger H, Bösl O, Witzel U, Linke B.

Orthopädische Universitätsklinik und Poliklinik Friedrichsheim, Frankfurt a. M.

[Complications after Hip Resurfacing using the ASR Prosthesis in Patients with Osteoarthritis.]

PURPOSE: The purpose of this study was to evaluate peri- and postoperative complications and the clinical/radiological results after hip resurfacing with the ASR prosthesis in patients with osteoarthritis. METHOD: A prospective cohort study was performed including all patients who received a hip resurfacing (ASRtrade mark prosthesis, DePuy, Motech, Warsaw, IN, USA) because of osteoarthritis between 1/2005 and 7/2006. 115 prostheses were performed in 110 patients (58 female, 52 male). In all patients a dorsal approach was used. The mean age was 57.82 years (range: 34 to 72 years) and the mean follow-up was after 12.5 months (range: 6 to 23 months). At the time of follow-up an X-ray (a. p. and axial) of the operated hip was performed in addition to the to standard clinical examination. To measure the functional outcome the Harris hip score was used. RESULTS: We observed postoperative complications in 18 patients. Three non-trauma-related femoral neck fractures were seen after a mean of 58 days (range: 41 to 70 days). One trauma-related femoral neck fracture was found after 7 months. Neural complications were found in two patients. In 8 patients a revision of the acetabular component was necessary. 3 dislocations could be managed without further revision. One revision was necessary because of a persisting seroma without infection. No infections or thromboembolic complications were seen. The mean Harris hip score developed from preoperative 59 points (range: 50 to 65 points) to postoperative 96 points (range: 85 to 100 points). CONCLUSIONS: Excellent early postoperative results can be reached by hip resurfacing. Special attention is necessary performing the correct positioning of the femoral and acetabular components. If notching is seen intraoperatively the operation should be switched and a large head prothesis should be implanted. Long-term results are still lacking.

Klein M, Scherger B, Bernd H, Ostermann PA.

Unfallchirurgische Klinik, Medizinische Hochschule Hannover.

[Risk management in hospitals: standard operating procedures in aviation as a model for structuring medical communication.]

AIM: The working conditions for medical staff in German hospitals with emergency units are characterised by stress peaks. In such moments mistakes are more likely to be made. Communication problems and misunderstandings caused by these settings are the most frequent causes for blunders, errors and mistakes. The aim is to show an easy way to reduce the incidence of these problems. METHOD: Within this prospectively randomised trial we compare the ability of 50 physicians to remember standardised information on patient\’s data passed on to them in a briefing. Half of the subjects used the so called 5-finger method as an easy means of memorising standardised information. The other 25 physicians memorised the patient\’s data in the usual way. In order to assess the information recalled by the subjects, all of them were asked to answer 15 questions on the data they had been given an hour earlier. RESULTS: The subjects who used the 5-finger method were able to give on average 9.88 (of 15) correct answers and thus remembered significantly (p = 0.031) more information than the members of the control group. CONCLUSION: Communication errors caused by homophony, ambiguity, anticipation and mental models are can be avoided in well-structured communication situations. The rules for such a type of communication can easily be learned and applied. Standardised communication has already proved to reduce the error rates in aviation. We conclude that it can be helpful to introduce standardised communication rules such as the 5-finger method in medical communication.

Schmidt C, Ramsauer B, Witzel K.

CRM Medical, Kitzbühel, Osterreich.

[Iatrogenic injuries - avoiding errors in orthopaedics and traumatology.]

Mosaicism, modules, and the evolution of birds: results from a bayesian approach to the study of morphological evolution using discrete character data.

The study of morphological evolution after the inferred origin of active flight homologous with that in Aves has historically been characterized by an emphasis on anatomically disjunct, mosaic patterns of change. Relatively few prior studies have used discrete morphological character data in a phylogenetic context to quantitatively investigate morphological evolution or mosaic evolution in particular. One such previously employed method, which used summed unambiguously optimized synapomorphies, has been the basis for proposing disassociated and sequential \”modernizing\” or \”fine-tuning\” of pectoral and then pelvic locomotor systems after the origin of flight (\”pectoral early-pelvic late\” hypothesis). We use one of the most inclusive phylogenetic data sets of basal birds to investigate properties of this method and to consider the application of a Bayesian phylogenetic approach. Bayes factor and statistical comparisons of branch length estimates were used to evaluate support for a mosaic pattern of character change and the specific pectoral early-pelvic late hypothesis. Partitions were defined a priori based on anatomical subregion (e.g., pelvic, pectoral) and were based on those hypothesized using the summed synapomorphy approach. We compare 80 models all implementing the M(k) model for morphological data but varying in the number of anatomical subregion partitions, the models for among-partition rate variation and among-character rate variation, as well as the branch length prior. Statistical analysis reveals that partitioning data by anatomical subregion, independently estimating branch lengths for partitioned data, and use of shared or per partition gamma-shaped among-character rate distribution significantly increases estimated model likelihoods. Simulation studies reveal that partitioned models where characters are randomly assigned perform significantly worse than both the observed model and the single-partition equal-rate model, suggesting that only partitioning by anatomical subregion increases model performance. The preference for models with partitions defined a priori by anatomical subregion is consistent with a disjunctive pattern of character change for the data set investigated and may have implications for parameterization of Bayesian analyses of morphological data more generally. Statistical tests of differences in estimated branch lengths from the pectoral and pelvic partitions do not support the specific pectoral early-pelvic late hypothesis proposed from the summed synapomorphy approach; however, results suggest limited support for some pectoral branch lengths being significantly longer only early at/after the origin of flight.

Clarke JA, Middleton KM.

Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Campus Box 8208, Raleigh, NC, USA.

Erratum.

Regio- and diastereo-selectivity of montmorillonite-catalyzed oligomerization of racemic adenosine 5\’-phosphorimidazolide.

Clay is a possible candidate for an effective catalyst in prebiotic chemical evolution of biomolecules. Montmorillonite was reported to effectively catalyze oligomerization of racemic adenosine 5\’-phosphorimidazolide (DL-ImpA). In the oligomerization reaction, considerable amounts of cyclic dimers as well as linear dimers were produced in the oligomerization reactions. To assess the regio- and diastereo-selectivities of the oligomerization reaction, the dimer products including cyclic dimers were completely identified by means of enzymatic degradation reactions of the products.

Urata H, Fujimori M, Aono C, Yamakawa T, Harada E, Akagi M.

Osaka University of Pharmaceutical Sciences, Osaka, Japan.

Synthesis of 3\’-acetamidoadenosine derivatives as potential a(3) adenosine receptor agonists.

On the basis of high binding affinity of 3\’-aminoadenosine derivatives 2b at the human A(3) adenosine receptor (AR), 3\’-acetamidoadenosine derivatives 3a-e were synthesized from 1,2:5,6-di-O-isopropylidene-D-glucose via stereoselective hydroboration as a key step. Although all synthesized compounds were totally devoid of binding affinity at the human A(3)AR, our results revealed that 3\’-position of adenosine can only be tolerated with small size of a hydrogen bonding donor like hydroxyl or amino group in the binding site of human A(3)AR.

Chun MW, Choi SW, Kang TK, Choi WJ, Kim HO, Gao ZG, Jacobson KA, Jeong LS.

College of Pharmacy, Seoul National University, Seoul, Korea.

De novo synthetic route to a combinatorial library of peptidyl nucleosides.

A stereoselective synthetic route has been developed for the combinatorial synthesis of a structurally unique class of C-4\’ side chain modified peptide-linked nucleosides. The synthetic strategy and approach involves initial synthesis of a strategically functionalized amino butenolide template, utilizing L-serine as a chiral starting material. Subsequent transformation of the above lactone to C4\’ aminoalkyl substituted nucleosides, followed by the peptidic coupling of the C4\’ side chain amine with various amino acids completed the syntheses of the target peptidyl nucleosides. Employing the above route, and utilizing a combination of easily available nucleobases (4) and amino acids (6) as the two diversity elements, synthesis of a 24-member combinatorial library of the title peptide-linked nucleosides has been accomplished.

Poon KW, Liang N, Datta A.

Department of Medicinal Chemistry, The University of Kansas, Lawrence, Kansas, USA.

ChipcheckII - Predicting Binding Curves for Multiple Analyte Strands on Small DNA Microarrays.

Incomplete binding, saturation, and cross-hybridization between partially complementary strands complicate the parallel detection of nucleic acids via DNA microarrays. Treating the competing equilibria governing binding to microarrays requires computational tools. We have developed the web-based program ChipCheckII that calculates total hybridization matrices for target strands interacting with probes on small DNA microarrays. The program can be used to compute the extent of cross-hybridization and other phenomena affecting fidelity of detection based on sequences, quantities of strands, and hybridization conditions as inputs. Enthalpy and entropy of duplex formation are generated locally with UNAfold, including those for complexes that are partially matched. Simulated binding versus temperature curves for portions of a commercial genome chip demonstrate the extent to which cross-hybridization can complicate DNA detection. ChipCheckII is expected to aid nucleic acid chemists in developing high fidelity DNA microarrays.

Siegmund K, Ahlborn C, Richert C.

Institute for Organic Chemistry, University of Karlsruhe, Karlsruhe, Germany.