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Objectives/hypothesis: To investigate the pattern of intensity levels in images generated by the two most commonly used rigid endoscopes angulations in sinus surgery: 0° and 30°., Methods: An enclosed light box containing an optical square grid, under endoscope illumination set just below saturation level, was used for measuring light distribution levels across test images. Endoscopes with 0° and 30° angulations were tested at 10 mm from the grid, typical for sinus surgery. The grid was set perpendicular to the axis of the shaft of the endoscope. The grayscale light intensity (GLI) levels (0 = black, 255 = white) in each of the grid squares were quantified from the digitized images., Results: Light intensity was highly non-uniform for both endoscopes. The brightest area of the field of view was at the center for the 0° endoscope and at about 20% of the image diameter proximally from the center for the 30° endoscope. For the 0° endoscope with a maximum value of about 230 GLI (90% of white saturation) at the center the minimum value was about 100 GLI at the periphery. The 30° endoscope with a similar maximum GLI value of 226 had a minimum of under 50 GLI at the most distant periphery, too dark for clear grid line definition., Conclusion: There are wide variations in light intensity across the image circle and much reduced illumination of the field edge. Surgeons should be aware of this fact so that accommodation can be made when surgical manipulation is performed away from the center of the endoscope field. This is especially relevant in angled cavities such as the frontal sinus recess, where the degree of angulation necessitates "edge of field" surgery., Competing Interests: The authors declare no conflicts of interest., (© 2021 The Authors. Laryngoscope Investigative Otolaryngology published by Wiley Periodicals LLC on behalf of The Triological Society.)

Background: This study was undertaken to introduce and establish the value of the Dundee Endoscopic Psychomotor Otolaryngology Surgery Trainer (DEPOST) as a customisable, objective real-time scoring system for trainee assessment. The construct validity of the system was assessed by comparing the performance of experienced otolaryngologists with that of otolaryngology trainees, junior doctors and medical students., Methods: Forty two subjects (13 Consultants, 8 senior trainees, 13 junior trainees and 8 junior doctors/medical students) completed a single test on DEPOST. The test involved using a 30° rigid endoscope and a probe with position sensor, to identify a series of lights in a complex 3-dimensional model. The system scored subjects for time, success rate, and economy of movement (distance travelled). An analysis of variance and correlation analysis were used for the data analysis, with statistical significance set at 0.05., Results: Increasing experience led to significantly improved performance with the DEPOST (p < 0.01). Senior trainees' results were significantly better than those of consultant otolaryngologists in success rate and time (p < 0.05 & p < 0.05). Consultants were the most efficient in their movement (p = 0.051) CONCLUSIONS: The system provides an accurate and customisable assessment of endoscopic skill in otolaryngologists. The DEPOST system has construct validity, with master surgeons and senior trainees completing the tasks more accurately without sacrificing execution time, success rate or efficiency of movement.

This paper presents a finite element study of a temporomandibular joint (TMJ) prosthesis in which the mandibular component sits on the condyle after removal of only the diseased articular surface and minimal amount of condylar bone. The condylar support prosthesis (CSP) is customised to fit the patient and allows a large part of the joint force to be transmitted through the condyle to the ramus, rather than relying only on transfer of the load by the screws that fix the prosthesis to the ramus. The 3-dimensional structural finite element analysis compared a design of CSP with a standard commercial prosthesis and one that was modified to fit the ramus, to relate the findings to the different designs and geometrical features. The models simulated an incisal bite under high loading. In the CSP and in its fixation screws, the stresses were much lower than those in the other 2 prostheses and the bone strains were at physiological levels. The CSP gives a more physiological form of load transfer than is possible without the condylar contact, and considerably reduces the amount of strain on the bone around the screws., (Copyright © 2015 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

Background: Glare from surgical instruments and tissue surfaces often occurs during endoscopic procedures and can be disturbing to the operator. The brightness level of the light source can be reduced, but at the expense of overall image clarity, so alternative solutions are needed for removing glare. Digital image-processing methods offer the opportunity to lessen or eliminate glare by reducing the intensity of the affected parts of the image. This study investigated a new automated method for glare reduction that uses two different intensity thresholds as a basis for applying glare reduction processes and it also reduces unpleasant artifacts at the glare region boundaries., Methods: The new glare-reduction method was compared with a previous method. Three variants of each method, each with different color biases in the glare regions, were applied to a 20-s surgical recording containing substantial amounts of glare. The six versions and the original recording were evaluated subjectively by a group of 10 experienced surgeons using a paired-comparisons method, in which each version was compared for preference with all the other versions., Results: The new double-threshold intensity-subtraction method scored significantly higher than the previously developed glare-reduction method (p < 0.05). It also scored higher than the original (unprocessed) version, but not significantly. The color bias was important, with combinations of pink and grey performing better than yellow tints., Conclusions: The findings show the new method to be a significant improvement in automatic glare reduction compared with earlier methods. The method is not computationally demanding, so it can in the future be evaluated clinically in high-definition endoscopic imaging systems and developed further in this environment.

Soft actuators based on Ionic Polymer-Metal Composites (IPMCs) are of considerable interest for applications in biomedical devices and robotics. In this work, thin commercial and thick laboratory-prepared Nafion membranes were made into model IPMC actuator devices by incorporation of Pt electrode layers. In extensive electromechanical tests the maximum average tip displacement and maximum force generated were recorded. The effect of amplitude and frequency of the applied voltage on both displacement and force was examined as were the effects of the origin of the Nafion membrane, the Pt loading, the structure of the electrode and the presence or absence of an Au overlayer. The cast samples generated much smaller displacements but much larger forces than the commercial Nafion samples. For all samples, displacement and force increased with increasing applied voltage, with increased number of Pt plating cycles and when an Au overlayer was present but decreased with increasing applied voltage frequency. Waveform analysis of applied voltage, current and force was performed by considering the capacitive nature of the IPMC actuators.

Greater understanding of the surgeon's task and skills are required to improve surgical technique and the effectiveness of training. Currently, neither the objective measurement of osteotomy forces during endoscopic sinus surgery (ESS) nor the validity of the properties of cadaver materials, are well documented. Measurement was performed of peak axial osteotomy force during ESS. A comparison was made of results with previously published cadaver data to validate the force properties of cadaver models. A prospective, consecutive cohort of 25 patients was compared with data from 15 cadaver heads. A modified Storz sinus curette measured osteotomy force from uncinate, bulla ethmoidalis, and ground lamella. Independent variables were osteotomy site, age, gender, indication for surgery, and side. Corresponding cadaver data were analyzed for the independent variables of osteotomy site, side, and gender and then compared with the live patient data. Mean osteotomy force in live patients was 9.6 N (95% CI, 8.9-10.4 N). Mean osteotomy force in the cadaver heads was 6.4 N (95% CI, 5.7-7.0 N). Ethmoid osteotomy of live patients required 3.2 N (95% CI, 2.1-4.3 N) more force than the cadaver heads (p = 0.0001). This relationship was statistically significant at the bulla ethmoidalis (p = 0.002) and the ground lamella (p = 0.0001) but not at the uncinate (p = 0.068). Osteotomy in female live subjects required 1.6 N (95% CI, 0.1-3.1 N) more force than male live subjects (p = 0.03). Cadaver tissue may underestimate the mean osteotomy force required in osteotomy of living ethmoid sinus lamellae by a factor of 1.5 times. Caution may be required in extrapolating force estimates from cadaver tissue to those required in living patients.

Doped diamond-like carbon (DLC) coatings offer potential antifouling surfaces against microbial and protein attachment. In particular, stainless steel surgical instruments are subject to tissue protein and resilient prion protein attachment, making decontamination methods used in sterile service departments ineffective, potentially increasing the risk of iatrogenic Creutzfeldt-Jakob disease during surgical procedures. This study examined the adsorption of proteins and prion-associated amyloid to doped DLC surfaces and the efficacy of commercial cleaning chemistries applied to these spiked surfaces, compared to titanium nitride coating and stainless steel. Surfaces inoculated with ME7-infected brain homogenate were visualised using SYPRO Ruby/Thioflavin T staining and modified epi-fluorescence microscopy before and after cleaning. Reduced protein and prion amyloid contamination was observed on the modified surfaces and subsequent decontamination efficacy improved. This highlights the potential for a new generation of coatings for surgical instruments to reduce the risk of iatrogenic CJD infection.

Both physical and chemical crosslinking methods have been shown to be effective in improving the biological stability and mechanical properties of porous collagen scaffolds. However, the wetting of the collagen fibril surface by a culture medium is reduced and it is difficult for the medium to diffuse into the 3D structure of a porous collagen scaffold. This article reports a strategy for the surface processing of crosslinked collagen scaffolds by an integrated ultraviolet/ozone perfuse processing technique. Ultraviolet/ozone perfuse processing improved surface wettability for both the exterior and interior surfaces of the porous 3D collagen scaffold. This leads to a significant improvement in the scaffolds ability to take up water without compromising the bulk biological stability and mechanical properties. In vitro evaluation using mesenchymal stem cell demonstrated that surface processing enhanced cell colonization of the scaffolds, cells could migrate deep into the structure of the scaffolds, and significantly higher levels of cell proliferation were achieved. In contrast, the cells were unable to migrate deep into the scaffolds, and most of the cells that survived were observed only in the top seeding layer resulting in a low level of cell activity in the unprocessed scaffolds.

Diamond-like carbon (DLC) films, especially modified DLC films with doped elements as biomaterials for medical devices have been attracting great interest. In this article, the bacterial adhesion behavior on DLC films, Si-doped DLC films, and stainless steel 316L was investigated with Pseudomonas aeruginosa ATCC 33347, which frequently causes medical device-associated infections. This was done under laminar flow conditions in a flow chamber at 37 degrees C. The contact angles of the coatings and the biofilm were measured. Polar liquids of distilled water and ethylene glycol, and apolar liquid of diiodomethane were used as a probe for surface free energy calculations. The electron donor component gamma(-) of surface energy of Si-doped DLC films increased with increasing the silicon content in the DLC films. The experimental results showed that the surface energy of the coatings and the interaction energy between the coatings and bacteria in water had significant influences on bacterial adhesion. The extended DLVO theory was used to explain the adhesion behavior.

The continuous wavelet transform (CWT) is an effective tool when the emphasis is on the analysis of non-stationary signals and on localization and characterization of singularities in signals. We have used the B-spline based CWT, the Lipschitz Exponent (LE) and measures derived from it to detect and quantify the singularity characteristics of biomedical signals. In this article, a real-time implementation of a B-spline based CWT on a digital signal processor is presented, with the aim of providing quantitative information about the signal to a clinician as it is being recorded. A recursive algorithm implementation was shown to be too slow for real-time implementation so a parallel algorithm was considered. The use of a parallel algorithm involves redundancy in calculations at the boundary points. An optimization of numerical computation to remove redundancy in calculation was carried out. A formula has been derived to give an exact operation count for any integer scale m and any B-spline of order n (for the case where n is odd) to calculate the CWT for both the original and the optimized parallel methods. Experimental results show that the optimized method is 20-28% faster than the original method. As an example of applying this optimized method, a real-time implementation of the CWT with LE postprocessing has been achieved for an EMG Interference Pattern signal sampled at 50 kHz.

The influence of surrounding electrolyte type and concentration on the contact angle of hydrophobic diiodomethane on silicon-doped diamond-like carbon (DLC) coatings was examined to provide insight into how the presence of electrolytes in the solution influences adhesion of hydrophobic material to doped DLC surfaces. There was a small but statistically significant increase of contact angle with increasing electrolyte concentration over the range from 0 to approximately 0.01 M, after which the contact angle was virtually unaffected by further increase in the concentration of electrolyte. It was shown that CaCl(2) has a stronger influence on the change of the contact angle than NaCl, and that an increase in Si content in the DLC coatings increased the change in the contact angle of diiodomethane for all types of electrolyte. These observations suggest that the adhesion to the Si-doped DLC surfaces is reduced by addition of the electrolytes to the surrounding solvent. This could be explained by increased ion adsorption on the DLC surface with increase in silicon doping, causing the surfaces to be more hydrophilic.

Protein-repellent diamond coatings have great potential value for surface coatings on implants and surgical instruments. The design of these coatings relies on a fundamental understanding of the intermolecular interactions involved in the adhesion of proteins to surfaces. To get insight into these interactions, adhesion energies of glycine to pure and Si and N-doped (111) diamond surfaces represented as clusters were calculated in the gas phase, using density functional theory (DFT) at the B3LYP/6-31G* level. The computed adhesion energies indicated that adhesion of glycine to diamond surface may be modified by introducing additional elements into the surface. The adhesion was also found to induce considerable change in the conformation of glycine when compared with the lowest-energy conformer of the free molecule. In the Si and N-substituted diamond clusters, notable changes in the structures involving the substituents atoms when compared with smaller parent molecules, such as 1-methyl-1-silaadamantane and 1-azaadamantane, were detected. Adhesion free energy differences were estimated for a series of representative peptides (hydrophobic Phe-Gly-Phe, amphiphilic Arg-Gly-Phe, and hydrophilic Arg-Gly-Arg) to a (111) diamond surface substituted with different amounts of N, Si, or F, using molecular dynamics simulations in an explicit water environment employing a Dreiding force field. The calculations were in agreement with the DFT results in that adsorption of the studied peptides to diamond surface is influenced by introducing additional elements to the surface. It has been shown that, in general, substitution will enhance electrostatic interactions between a surface and surrounding water, leading to a weaker adhesion of the studied peptides.

The high incidence of infections caused by the use of implanted biomedical devices, including catheters, bone fracture fixation pins and heart valves, etc. has a severe impact on human health and health care costs. Diamond-like carbon (DLC) films as biomaterial for medical devices have been attracting great interest due to their excellent properties such as low friction and chemical inertness. It has been demonstrated that the properties of DLC films can be further improved by the addition of selective elements into DLC films. In this paper Si- and N-doped DLC coatings with various silicon and nitrogen contents on 316 stainless steel substrates were prepared by a magnetron sputtering technique. Bacterial adhesion to the modified DLC coatings was evaluated with Pseudomonas aeruginosa (ATCC 33347) which frequently cause medical device infections. The results showed that the addition of N or Si in DLC coatings had a significant influence on bacterial adhesion. In general the modified DLC coatings with N or Si performed better than the pure DLC coatings in inhibiting bacterial adhesion. The bacterial adhesion mechanism on the modified DLC coatings was explained with thermodynamic theory.

Clinical electromyography (EMG) interference pattern (IP) signals can reveal more diagnostic information than their constituents, the motor unit action potentials (MUAPs). Singularities and irregular structures typically characterize the mathematically defined content of information in signals. In this paper, a wavelet transform method is used to detect and quantify the singularity characteristics of EMG IP signals using the Lipschitz exponent (LE) and measures derived from it. The performance of the method is assessed in terms of its ability to discriminate healthy, myopathic and neuropathic subjects and how it compares with traditionally used Turns Analysis (TA) methods and a method recently developed by the authors, interscale wavelet maximum (ISWM). Highly significant intergroup differences were found using the LE method. Most of the singularity measures have a performance similar to that of ISWM and considerably better than that of TA. Some measures such as the ratio of the mean LE value to the number of singular points in the signal have considerably superior performance to both methods. These findings add weight to the view that wavelet analysis methods offer an effective way forward in the quantitative analysis of EMG IP signal to assist the clinician in the diagnosis of neuromuscular disorders.

Diamond-like carbon (DLC) and tetrahedral amorphous carbon (ta-C) have attracted much attention recently for biomedical and antifouling applications due to their excellent biocompatibility and inherent nonstick properties. It has been demonstrated that the solid surface free energy is a dominant factor in cellular or fouling adhesion. However, few data for the surface free energy of DLC and ta-C coatings at temperatures in the range 37-95 degrees C are available. In this study DLC and ta-C coatings on stainless steel 304 sheets were prepared using an unbalanced magnetron sputtering system and a filtered cathodic vacuum arc system, respectively. The contact angles of water, diiodomethane and ethylene glycol on the coated surfaces at temperatures in the range 20-95 degrees C were measured using a Dataphysics OCA-20 contact angle analyzer. The surface free energy of the coatings and their components (e.g., dispersion, polar or acid/base portions) were calculated using various methods. The experimental results showed that the total surface free energy and dispersive surface free energy of the ta-C coatings, DLC coatings, stainless steel 304 and titanium decreased with increasing surface temperature, while the acid-base SFE component increased with increasing temperature.

Both platelet aggregation and white blood cell aggregation are involved in pathological processes such as thrombosis, atherosclerosis and chronic inflammation. People in older age groups are likely to suffer from cardiovascular diseases and may have increased white cell and platelet aggregation which could contribute to this increased risk. This study aimed to compare white cell and platelet aggregation between different age and gender groups. Whole blood white cell aggregation and platelet aggregation were carried out on healthy volunteers using cytometric techniques. It was found that both white cell and platelet aggregation in the elderly group (white cell aggregation median value, 0.08; range, 0.02-0.14; platelet aggregation median value, 0.32; range, 0.1-0.39) were significantly higher (P = 0.017 for white cell aggregation, P = 0.007 for platelet aggregation) than in the younger group (white cell aggregation median value, 0.05; range, 0.01-0.14; platelet aggregation median value, 0.18; range, 0.07-0.36). No significant differences were found between the gender groups.

A method has been developed, interscale wavelet maximum (ISWM), for characterising the electromyogram (EMG) interference pattern to assist in the diagnosis of neuromuscular disease. EMG signals are decomposed with the redundant dyadic wavelet transform and wavelet maxima (WM) are found. Thresholding methods are applied to remove WM due to noise and background activity. An efficient fine-to-coarse algorithm identifies the WM tree structure for the motor unit action potential rising edges. The WM for each tree are summed at each scale; the largest value is the ISWM. Highly significant differences in ISWM values have been found between healthy, myopathic, and neuropathic subjects that could make the technique a useful diagnostic tool.

Displacement-frequency characteristics of the stapes footplate were measured in five human temporal bones before and after draining the vestibule. Measurements were made in the 0.125-8 kHz range at 80 dB input sound pressure level, using a laser Doppler vibrometer. A circuit model was also used to predict stapes displacement. The temporal bone studies show a slight decrease in stapes footplate displacement at low frequency, and little change above 1 kHz. The displacement change is not as great as that found by other investigators or predicted by the model. There is little difference in stapes motion in temporal bones when the inner ear is intact or drained.

Stress shielding of the femur is known to be a principal factor in aseptic loosening of hip replacements. This paper considers the use of a hollow stemmed hip implant for reducing the effects of stress shielding, while maintaining acceptably low levels of stress in the cement. Using finite element modelling, the stresses in the proximal femur using different shapes of hollow stem were compared with those produced using comparable sizes of solid stem with different values of elastic modulus. A reduction in stress shielding could be achieved with a hollow stem. A cylindrical hollow stem design was then optimised in order to control the maximum allowable stress in the cement, the minimum allowable stresses in the bone, and a combination of the two. The resulting stems achieved an increase in proximal bone stress of about 15% for the first case and 32% for a model using high strength cement, compared with solid stems of the same nominal outside diameter. The gains of these theoretically optimised designs dropped off rapidly further down the stem. Linearly tapered hollow stems reached a 22% gain, which could be a good compromise between acceptable cement stresses and ease of manufacture.

We have developed a prototype middle-ear hearing implant which uses a multilayer piezoelectric actuator. In this series of experiments the actuator was attached to the medial wall of the attic so that it makes contact with the body of the incus. Initial in vitro evaluation has been carried out using a laser vibrometer (Polytec CLV) to measure stapes velocity. Stapes displacement is calculated by mathematical integration. The device used in this way is particularly effective at transmitting high frequency sound to the stapes. When switched off the actuator impairs the transmission of sound to the ossicular chain at low frequencies, but this effect is only 7 dB at most. The stapes displacements resulting from the action of the implant have a linear relationship with the voltages used to drive the system. The high capacitance of the present actuator means that its power requirements are higher than that of other comparable devices. An optimal method of coupling the device to the incus has yet to be identified.

The principal physiological function of platelets is to promote haemostasis but they also contribute to thrombosis and atherogenesis. Platelet volume is a marker and possibly a determinant of platelet function in that large platelets are more active than normal sized platelets. Mean platelet volume (MPV), a measure of platelet size, reflects changes in either the level of platelet stimulation or the rate of platelet production. For these reasons, we have developed a sensitive instrument to measure platelet volume, which we believe is more reliable and specific than previously used instruments. It is based on a computer-interfaced Coulter Thrombocytometer and a pulse analyser including a high-speed baseline restorer. We have developed a reproducible method to assay MPV and from the histogram derived the median (MED) and the skewness (SK) values. We have looked at the effects of anticoagulant used and time elapse prior to assay. A normal range has been established for MPV which correlates directly with MED and inversely with SK. The MPV decreases with age but there is no difference between genders. We have demonstrated a negative correlation between whole blood platelet number and MPV and MED, and a direct relationship with the SK of the histogram of the platelet volume.

Objective: To develop and validate a computerised algorithm for the interpretation of the characteristics of fetal heart rate monitoring in labour., Design: Prospective observational study., Setting: Labour ward in a tertiary hospital., Sample: Intrapartum cardiotocograms from 24 pregnancies., Methods: A computerised algorithm was developed to assess the fetal heart baseline rate, variability, the number of accelerations and the number of decelerations. Twenty five minute segments of cardiotocograms were interpreted by the algorithm and also by seven expert reviewers independently. The reviewers were unaware of the outcome of labour. The reliability of the characteristics of cardiotocography and the validity of the computerised algorithm were assessed using the intraclass correlation coefficient and weighted kappa statistic for continuous and ordinal variables respectively., Results: The inter rater reliability of the baseline fetal heart rate and the number and type of decelerations was good (intraclass correlation coefficient 0.93, 0.93 and 0.79, respectively). The reliability of baseline variability (kappa = 0.27) and accelerations (intraclass correlation coefficient = 0.27) was poor. The computerised algorithm had good agreement with the reviewers for the baseline fetal heart rate (intraclass correlation coefficient 0.91 to 0.98) and the number of decelerations (intraclass correlation coefficient 0.82 to 0.91), but was less valid as regards the number of late decelerations (intraclass correlation coefficient 0.68 to 0.85) and the number of accelerations (intraclass correlation coefficient 0.06 to 0.80), and was invalid as regards baseline variability (kappa 0.00 to 0.34)., Conclusions: The high level of validity of the computerised algorithm for the estimation of the baseline fetal heart rate and the number of decelerations justifies its further technical development.

An anatomically shaped incus replica prosthesis has been designed to reconstruct the ossicular chain. A series of in vitro studies on human temporal bones evaluated the acoustic performance of this prosthesis and compared it with a Causse partial ossicular replacement prosthesis (PORP). Pure tones in the frequency range 0. 125-8 kHz stimulated the tympanic membrane at sound pressure levels of 80, 90 and 100 dB. Measurements of the stapes footplate velocity were made with a laser interferometer. The acoustic function of the ossicular chain reconstructed with the incus replica prosthesis was found to be within 10 dB of that of the original intact ossicular chain, when both the upper and lower joints of the implant were rigidly fixed in place. It was shown that a rigid mechanical contact between the ossicular prosthesis and ossicles is a prerequisite for effective sound transmission. The anatomically shaped incus prosthesis gave a 15-dB improvement on the PORP at frequencies below 1.5 kHz.

To ascertain whether patients with Colles' fracture should be investigated for osteoporosis and the risk of future fractures, we measured the bone mineral density of the distal radius of the other arm in 31 women patients and compared the results with those of a control group of 289 normal women. We divided the patients into two groups, those younger than 66 years and those older. In 25 patients we found values for bone mineral density which were lower than one standard deviation below the mean value for their age. Younger patients had a deficit greater than that expected for their ages. We believe that women with Colles' fracture should be evaluated routinely for osteoporosis, particularly if they are under 66 years of age.

Silicone elastomers have been used as implants in orthopaedics for replacements of small joints such as the metacarpophalangeal joint. A series of experiments was conducted an axially tensioned silicone elastomer tendon spacer samples to determine whether there is a relationship between stress in the material and image intensity. With increasing load, reduced image intensities were observed using spin echo (SE), gradient echo (GE) and magnetic resonance imaging (MRI) snapshot techniques. MR attenuation was accentuated in the GE experiment. The T1 and T2 snapshot images were dim and showed a low signal-to-noise ratio, so analysis was limited. Changes in magnetic susceptibility are suggested as the mechanism causing reduced image intensity, due to the more pronounced attenuation in the GE image. An alternative mechanism is the alteration of crystallinity during loading, whereby molecular realignment modifies nuclear relaxation. The changes in spin lattice (T1) and spin spin (T2) relaxation times, which would support this, were not, however, satisfactorily demonstrated.

Accurate measurement of the height of individual pulses in a signal that is a.c.-coupled is dependent upon correcting a changing baseline to a constant value. A new fast baseline restorer, using internally triggered gated feedback with gain, has been designed and a version optimized for Gaussian-shaped pulses. Performance is dependent on the magnitudes of both the forward and the feedback gains. The design presented can achieve a 0.5% accuracy in pulse height for a minimum pulse width of 2.5 microseconds or for 5 microseconds overlapping pulses as long as the overlap is less than 50%. Typical applications for the baseline restorer include blood cell volume measurement systems, scintillation counters and radiation spectroscopy.

A preliminary study was conducted to analyze trabecular patterns in digitized wrist radiographic images from 68 patients (31 males and 37 females), aged from 7 to 93 years. The fast Fourier transform was used to perform the spectral analysis of the distal radius. Three indices were defined to permit quantification of the cancellous structure in terms of the spacing and orientation of bone trabeculae (periodicity): a spectral trabecular index, a longitudinal trabecular index, and a transverse trabecular index. The spectral trabecular index reflects the periodicity of the trabeculae (spacing and orientation), while the other 2 selectively reflect the periodicity of longitudinally and transversely oriented ones. The ratio of the longitudinal and transverse trabecular indices was also studied. The shape of the high magnitude frequencies in the spectrum was crosslike for all patients, implying a preferentially orthogonal 2-dimensional structure for the cancellous bone in the distal end of the radius. The variation of the defined trabecular bone indices with age corresponded with the formation of bone through infancy and adolescence, reaching a peak in adulthood and gradual loss thereafter. This quantification detects structural changes that occur with aging and may therefore be useful in the study of osteoporosis.

This paper investigates the performance of artificial neural networks for analysing and classifying EMG signals from healthy subjects and patients with myopathic and neuropathic disorders. EMG interference patterns (IP) were recorded under maximum voluntary contraction from the right biceps of a total of 50 subjects. Parameters were obtained from the signals using recognized quantification techniques including turns analysis, small segments analysis and frequency analysis. Supervised networks examined were an improved backpropagation network (IBPN), a radial basis network (RBN), and a learning vector quantization network (INQ). Supervised networks using different combinations of parameters from turns analysis and small segments analysis gave diagnostic yields of 60-80%. Combinations using frequency analysis parameters produced similar results. The performance of unsupervised Self-Organising Feature Maps (SOFM) was generally lower than that of the supervised networks. Including personal data (sex and age) did not improve the overall performance.

A comparison of the fixation strength was made for the Steinmann, Denham, and the Apex commercial bone pins, which have different drilling end geometry and self-tapping thread design. Additional tests were made to assess the effects of pre-drilling with an orthopaedic twist drill bit prior to pin insertion. Peak pull-out force and pin displacement were measured for these pins inserted into the distal metaphysis of human cadaveric tibiae. The quality of thread reproduction in the bone resulting from the cutting process was assessed from thread profiles of negative moulds cast into the threaded holes. The Apex pins had similar pull-out forces to the Denham pins, despite their smaller diameter. Values for both pins were significantly greater than those for the Steinmann pin. The thread profiles showed that the Denham pin caused substantial damage to the cortical bone and formed poor quality threads in the cancellous bone. The Apex pin formed a better thread, which was improved further by the use of a pre-drilled pilot hole., (Copyright © 1994. Published by Elsevier Ltd.)

Objectives: The purpose of this study was to evaluate the potential of nuclear magnetic resonance microimaging (NMRM) for investigating the depth of cure for visible light curing of dental composite materials., Methods: Cylindrical composite specimens were light-cured within the NMRM instrument for predetermined times. Vertical slice, mid-resolution, spin-echo images were acquired using a Bruker AM300WB instrument with a Bruker microimaging attachment. Images were digitized and intensity profiles generated using deuterium oxide/water as a reference intensity. Separate specimens were made to obtain Vickers microhardness values as a function of depth to compare an established method for determining depth of cure with NMRM., Results: A difference in NMR image intensity between uncured and cured composite resin has been detected. Values for integrated intensities were obtained at 150 microns intervals over the mid-fifth of the total image width. An abrupt transition was not seen at the cure front which advances with cumulative exposure time. NMRM produced similar data trends to microhardness measurement., Significance: NMRM produces three-dimensional images of "mobile" hydrogen nuclei to a resolution of 10(-5) mm3. It is non-invasive, non-destructive and able to selectively image protons in different chemical environments. It can be used to investigate depth of cure for light curing materials, but must be regarded as a research technique and not one for routine measurement. Refinement is necessary, possible, and in progress to improve resolution from the present 10(-2) mm3 towards the limit, and to reduce noise.

The purpose of this study was to devise a method for the tensile testing of the organic component of demineralised bone. It was hoped that the method could be applied to determine whether an observed reduction in the strength of bone in copper-deficient rats could be attributed to a reduction in the cross-linking of collagen. Tensile testing of a fully demineralised specimen proved impossible to perform because of the difficulty in gripping the material, which tended to slide out of its holding clamps. The technique devised involved the demineralisation of only the diaphysis of the bone, leaving the bone ends intact. This enabled the bone to be gripped firmly at both ends in an Instron tensile testing machine. Elongation under loading of the demineralised diaphysis was measured by the Instron and a video recording was made of the elongation of the central portion. The strain was found to be uniform. Tensile strength was found to correlate with copper levels in the liver (r = 0.54, p < 0.05), although no significant differences were found between the strength, the stiffness, or the strain to failure for bone from the copper-deficient animals and bone from the normal controls. The test method itself should be useful in other studies in which the tensile properties of the organic phase of bone need to be measured.

The difficulty of achieving good distal contact between a cementless hip endoprosthesis and the femur is well established. This finite element study investigates the effect on the stress distribution within the femur due to varying lengths of distal gap. Three-dimensional anatomical models of two different sized femurs were generated, based upon computer tomograph scans of two cadaveric specimens. A further six models were derived from each original model, with distal gaps varying from 10 to 60 mm in length. The resulting stress distributions within these were compared to the uniform contact models. The extent to which femoral geometry was an influencing factor on the stress distribution within the bone was also studied. Lack of distal contact with the prosthesis was found not to affect the proximal stress distribution within the femur, for distal gap lengths of up to 60 mm. In the region of no distal contact, the stress within the femur was at normal physiological levels associated with the applied loading and boundary conditions. The femoral geometry was found to have little influence on the stress distribution within the cortical bone. Although localized variations were noted, both femurs exhibited the same general stress distribution pattern.

Copper, through its role as cofactor for lysyl oxidase, is essential for intra- and inter-molecular cross-links in collagen. Copper deficiency, in man and in animals, is associated with bone fragility ascribed to defective cross-links. To assess bone strength in copper-deficient animals, we designed a sensitive torsion-testing apparatus according to biomechanical considerations. Femora from 7 copper-deficient rats and from their pair-fed controls were tested in torsional loading until fracture. Significant decreases in the maximal sustained torque (t = 2.93, p < 0.05), in the ultimate angular deformation (t = 2.52, p < 0.05) and in the toughness (t = 2.88, p < 0.05) were demonstrated. In a complementary study, it was shown that the ash weight and the calcium content of the femora from the copper-deficient animals did not differ from those of the controls. It was likely, therefore, that the impaired mechanical strength was related to defects in the collagen component of bone.

The holding strengths of AO screws in the calcaneus were tested with a view to incorporating them into a new design of ankle prosthesis aimed at reducing the incidence of loosening. Comparative studies were performed to determine the optimal type and number of screws and their optimal location and thread length. Pull-out tests with 4.5-mm cortical and 6.5-mm cancellous screws were performed on screws inserted into the posterior and middle facets of the calcaneus, these being the two most suitable places for screw fixation. The cancellous screws showed much higher holding strength than the cortical screws. There is room for only a single screw in each facet. The results indicated that a screw of 16-mm thread length should be inserted into the middle facet and a screw of 60-mm thread length into and through the posterior facet. The high holding strengths suggest that screw fixation could be a viable alternative to commonly used methods for anchoring the lower prosthetic component. Further tests are to be conducted which simulate the different types of loads occurring during gait and other activities. These will allow decisions to be made about the benefits of the proposed screw fixation method. This work is part of a long-term project which aims to produce a new ankle prosthesis that does not suffer the problems of loosening associated with present current designs. A strong screw fixation of the talar component may help to improve stability. The results show that a good fixation into the calcaneus can be achieved, and suggest that further work based on this approach is worthwhile., (Copyright © 1992. Published by Elsevier Ltd.)

The attendant operated wheelchair is propelled by applying forces to handles at the rear of the chair. There are no published data to justify the design of pushing handles on existing wheelchairs. In Dundee, studies of pushing have been conducted in order to obtain subjective preferences for location and design of handles and an understanding of biomechanical factors associated with wheelchair pushing. Preferred positions for handles have been found to be in the region of 0.75 of shoulder height, 1.14 times shoulder width although deviations of +/- 5% in these values are still rated as acceptable. The preferred positions do not correspond to minimum levels of resultant force or with lowest levels of moment in any of the upper body joints. Moments occurring at the lower back are not substantially affected by handle position. The biomechanical analysis so far has not revealed why some handle positions are more comfortable for pushing than others. Further study, involving calculation of resultant moments (rather than just sagittal plane moments) at these joints and at the lower body joints, is a next step in attempting to find the indicators of discomfort. Transferring a patient from or to a wheelchair can be a difficult operation with risks of accidents to the patient through falling and risks to the attendant of strain, particularly to the back. Current footrests on wheelchairs are a major source of the problems during transfer. A new approach to footrest design is described which solves these difficulties by using a footrest that lowers onto the floor. This has other attractive features such as providing good stability and restraint of the chair during transfer.(ABSTRACT TRUNCATED AT 250 WORDS)

Transferring a patient to or from a hospital wheelchair can be a difficult operation, with some risk to the patient and to the attendant. Studies are described in which the footrests of hospital wheelchairs are assessed and improved in order to reduce the problems of patient transfer. Four different types of footrest were fitted to hospital ward chairs and three types to transit chairs; these were assessed and compared by hospital ward staff and porters respectively. Based on the findings of these trials, a new type of footrest was designed for use on both types of chair. The new footrest lowers down to the ground and is operated by a footlever.

The turning resistance and rolling resistance of a range of wheelchair wheels up to 200 mm in diameter were measured on three types of indoor surface. Rolling resistance values were found by measuring deceleration on a flat surface and also by direct measurement on a treadmill. The horizontal forces required to push the front wheels of a wheelchair over small step obstacles were also found. Measurements were made for a variety of front wheels and the relationship between the horizontal force, step height, load, and type compressibility was investigated.