Interface load analysis for computer-aided design of below-knee prosthetic sockets

A finite-element analysis is made for the compression of soft tissues of the residual lower limb contained in a prosthetic socket. The analysis is relevant to static loading during stance in a patellar-tendon-bearing, below-knee design of socket. Values of Young's modulus are obtained experimentally for use in the model. One of the main objectives is to study the sensitivity of the loading to these values and also to other assumed conditions. Using direct pressure at the limb/socket interface and vertical stiffness as indicators, changes in material properties, socket alignment and socket rectification are investigated; assumptions about the frictional characteristic at the interface are seen to be critical in determination of load distribution. This type of analysis may provide the next stage of refinement for computer-aided socket design systems.

Method for in-shoe shear stress measurement

A methodology is described for use of a shear transducer, based on a magneto-resistive principle, to measure stresses under the plantar surface of the foot in-shoe during walking. Particular attention is paid to a projected application for study of diabetic plantar ulceration and its management by footwear. The transducer has a disc construction, approximately 4 mm thick by 16 mm diameter, and measures two orthogonal axes of shear simultaneously; this disc is mounted into an inlay that can be inserted into any stock orthopaedic shoe of the type commonly prescribed for diabetic foot problems. The transducer is located in the metatarsal head region of the inlay; exact placement of the transducer is determined by reference to the direct pressure distribution, the common method of palpation shown to be imprecise. Pilot trials on normal subjects are presented to evaluate the method.

Technical evaluation of a CAD system for orthopaedic shoe-upper design

Computer aided design is now employed routinely in the volume shoe trade. New styles are developed on a three-dimensional image of the last followed by automated pattern generation and engineering. It is suggested that such systems could be useful in the orthopaedic footwear industry although the different requirements for these bespoke products need careful consideration. A clinical trial has been conducted on the Shoemaster (Clarks Shoes) upper design system both to assess its technical capabilities and to consider its role in improvement of service and cosmetic appearance. This particular system works throughout on a three-dimensional representation of the shoe last, which offers particular advantages for integration with shape capture and reproduction. The report concentrates on the technical evaluation to assess (a) its ability to work with unusual last shapes dictated by medical requirements and (b) its potential for integration into a complete computer system for design of both shoe lasts and shoe uppers. The trial indicates that this particular system is promising in both respects.

Clinical trial of a computer-aided system for orthopaedic shoe upper design

A trial has been conducted to produce the uppers for orthopaedic shoes using an existing commercial computer-aided design system. The aims of the trial were to confirm that a CAD system developed for the volume shoe trade (Shoemaster from Clarks Shoes) could be used for the upper design of orthopaedic shoes and to assess the contribution of professional shoe design on cosmesis and acceptability of these shoes. A small number of adult diabetic patients and children with foot deformities were selected, all of who had previously been prescribed and issued with special shoes. The existing lasts for these patients were digitised, and new styles developed on the CAD system over a 3D image of the last. Pattern pieces were cut automatically and the uppers closed. Lasting was done as normal at the two collaborating orthopaedic companies and the shoes supplied to the patients. The CAD system proved successful in coping with orthopaedic last shapes and shoe requirements. Professional design produced fashionable and cosmetically-pleasing styles within the constraints imposed by the underlying medical conditions.

Changes in plantar surface shape induced by corrective forefoot eversion

An investigation is presented of the change in shape of the plantar surface of the foot when the forefoot is everted (prohated) from its natural unloaded orientation into a corrected position frequently used during shoe insert fabrication. Both free and corrected casts were made of 13 asymptomatic feet using established casting techniques. Digital scans capture each plantar surface shape into a computer where an analysis of the transverse slope of the plane is made at various longitudinal locations between midheel and metatarsal head regions. The profile of the slopes show results which are consistent with pronation about the midtarsal joint. These results may be useful as a first stage in establishing the appropriate shape corrections to be used in a computer-aided design system for shoe insert design.

Effect of hepatic vagotomy on postexercise substrate levels in food-restricted rats

The metabolic effects of a selective hepatic vagotomy (HV) were investigated at rest and immediately after a 50-min exercise period (26 m/min, 0% grade) in rats subjected to an overnight 50% food restriction. This dietary restriction reduced liver glycogen content to 50% of normal resting concentrations (2.2-2.8 g/100 g). No significant differences between HV and sham-operated rats were found in resting and exercising beta-hydroxybutyrate, glucose, glycerol, and insulin concentrations. Postexercise liver glycogen concentrations were reduced to approximately 1.0 g/100 g in both HV and sham-operated groups. This decrease was associated with significantly (P less than 0.01) lower postexercise glycogen levels in the soleus muscle of HV rats (2.6 times) along with higher plasma free fatty acid concentrations (P less than 0.01). These data provide evidence that HV combined with a progressive decrease in liver glycogen content may influence substrate regulation during exercise. They also support the concept of the existence of hepatic glucoreceptors responsive to a decrease in liver glycogen content.

Issues and themes in computer aided design for external prosthetics and orthotics

Computer aided design systems are finding use in prosthetics and orthotics in the production of customized components to match to and support body segments. Such systems consist essentially at present of shape measurement, computer manipulation of shape, and manufacture of the support surface or its mould. General themes of design philosophy, relationship of shape and pressure for body segments, representation and presentation of shape information by computer, surface adjustments, measurements and manufacturing geometry are considered. Aspects of existing systems are presented to highlight issues which may be the subject of future developments.

Allergy to castor bean. II. Identification of the major allergens in castor bean seeds

Castor bean proteins were separated and identified by isoelectric focusing and sodium dodecyl sulfate-polyacrylamide gel electrophoresis and blotted onto nitrocellulose paper. The capacity of the castor bean proteins to bind human IgE was probed with sera from castor bean-sensitive patients and radiolabeled anti-IgE. It proved difficult to identify allergens with isoelectric focusing. However, three allergens were identified when proteins were first separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis: the 2S storage albumin, the 11S crystalloid proteins, and a third protein doublet with molecular weights of 47 and 51 kd. Specific IgE antibody to the 2S storage albumin, measured by RAST, was detected in most (96%) castor bean-sensitive patients, confirming it as the major allergen. We would like to suggest that the 2S albumin be named Ric c I, that the crystalloid proteins be named Ric c II, and that the 47/51 kd doublet be named allergen 3.

Effect of selective hepatic vagotomy on plasma FFA levels in resting and exercising rats

Metabolic effects of a selective hepatic vagotomy (HV) were investigated in nonfasted (N) and 24-h fasted (F) rats, at rest and immediately after a 50-min exercise period (26 m/min, 0% grade). In nonfasted rats, no significant differences between HV and sham-operated (SHM) groups were found in blood substrates [free fatty acids (FFA) or glucose], insulin, and muscle glycogen levels, either at rest or after exercise. In F rats, liver glycogen was almost completely depleted at rest. This depletion was associated with a significantly (P less than 0.05) lower plasma FFA concentration at rest in HV compared with SHM rats (mean +/- SE, 0.57 +/- 0.04 vs. 0.83 +/- 0.1 mmol/l). No differences in FFA levels were observed between the same two groups after the exercise period. Exercise, however, resulted in a 2.5 times greater glycogen breakdown in the soleus muscle of HV compared with SHM rats. Hepatic vagotomy in the F condition was also associated with lower resting and exercising insulin concentrations. It is concluded that HV, when followed by a 24-h fast, may influence metabolic substrate regulation at rest and to a certain extent during exercise. These data support the concept of the existence of hepatic glucoreceptors responsive to a decrease in liver glycogen content.

Curve and surface representation by iterative B-spine fit to a data point set

The method of B-splines provides a very powerful way of representing curves and curved surfaces. The definition is ideally suited to applications in Computer Aided Design (CAD) where the designer is required to remodel the surface by reference to interactive graphics. This particular facility can be advantageous in CAD of body support surfaces, such as design of sockets of limb prostheses, shoe insoles, and custom seating. The B-spline surface is defined by a polygon of control points which in general do not lie on the surface, but which form a convex hull enclosing the surface. Each control point can be adjusted to remodel the surface locally. The resultant curves are well behaved. However, in these biomedical applications the original surface prior to modification is usually defined by a limited set of point measurements from the body segment in question. Thus there is a need initially to define a B-spline surface which interpolates this set of data points. In this paper, a computer-iterative method of fitting a B-spline surface to a given set of data points is outlined, and the technique is demonstrated for a curve. Extension to a surface is conceptually straightforward.

Foot pressure measurement: a review of clinical findings

In this review, a description of what is known about plantar pressure distribution in standing and in gait is followed by sections on clinical findings. Two major clinical areas are treated extensively, namely the diabetic foot and the foot in rheumatoid arthritis. Other applications, including the assessment of surgical procedures for orthopaedic corrections are also included. A large variety of different techniques for foot pressure measurement have been used; interpretation of the results has to be made on the basis of a firm understanding of the technique employed. Often, quantitative results from different pieces of apparatus are difficult to compare, indicating a need for accurate calibration and a standardized presentation. An up-to-date summary of pressure measurement systems reported over the past five years is included.

Bouncy knee in a semi-automatic knee lock prosthesis

The Bouncy Knee concept has previously proved of value when fitted to stabilised knee units of active amputees. The stance phase flex-extend action afforded by a Bouncy Knee increased the symmetry of gait and also gave better tolerance to slopes and uneven ground. A bouncy function has now been incorporated into a knee of the semi-automatic knee lock design in a pilot laboratory trial involving six patients. These less active patients did not show consistent changes in symmetry of gait, but demonstrated an improved ability to walk on slopes and increased their walking range. Subjective response was positive, as noted in the previous trials.

Foot loading in amputee stance

A survey has been carried out to establish information on foot loading in amputee stance. The parameters measured are percentage body weight and the positions of the centres of pressure under each foot. The data was collected in a clinical environment by the use of a Double Video Forceplate (DVF), a tool developed at the Bioengineering Centre. The objective of the survey is to provide background information for the use of the DVF in static alignment of lower-limb prostheses. Results are presented from a number of patients attending the Roehampton Walking Training School, and for a small group of patients attending the Bioengineering Centre for delivery of an experimental below-knee prosthesis. Scattergrams and averaged results provide normative data which can assist in interpretation of DVF displays during individual alignment.

Pedobarographic study of gait

The use of a pedobarograph for gait studies offer a rapid method to obtain instantaneous, two-dimensional images of foot-loading, which can be made available immediately to the clinician for qualitative inspection. The system can also produce quantitative results with a dynamic bandwidth sufficient for the study of most features of load transference. Although the linearity and resolution of force level may be inferior to that obtained by other methods, the spatial resolution is superior.

Sodium chloride equivalents, cryoscopic properties, and hemolytic effects of certain medicinals in aqueous solution. III: Supplemental values

A supplemental table of sodium chloride equivalents and freezing-point depressions at various concentrations for 44 different substances in aqueous solution is presented. Also given in the table is the isosmotic concentration of each material that can form such a solution. The degree of hemolysis of human erythrocytes was determined in 24 different isosmotic solutions, and the data are presented in a table to supplement the previously pub lished values. Eleven isosmotic solutions prevented hemolysis, and 13 others failed to prevent hemolysis.

Field dependence--independence, social--non-social play and sex differences in preschool children

The present study investigated the hypothesis that preschool children who spend more time in social play than in non-social play would be more field-dependent than their field-independent counterparts. Over-all the hypothesis was supported by the results. Although the social-non-social dimension appeared to account for most of the findings, correlations between individual play activities and field dependence suggested that this single dimension could not adequately account for all of the findings. The dimension of perceptual-motor demand required in some of the activities may have been involved as well. Discussion focused on the complexity of the play preference, cognitive findings, and on sex differences as well.