Socket Design Research Articles

Method for the design and analysis of a non-linear anisotropic lower limb prosthetic socket

A simplified computer-based structural analysis procedure has been developed for evaluating the stresses in a lower limb prosthetic socket when subjected to external loads. This technique has been tested by studying a simple linear axisymmetric shell subjected to uniform loads. It was found that the stress and strain distributions obtained are close to those determined by a finite element technique. The method that has been proposed involves an incremental procedure, which can be used to analyse the behaviour of a prosthetic socket of irregular shape made from non-linear anisotropic materials. By employing the proposed procedure to study an example, in which a simplified lower limb prosthetic socket is subject to internal pressure and frictional forces, the effects of the material non-linearity have been found to be significant.

STUDY INTO MECHANICAL PROPERTIES AND DESIGN METHOD OF LARGE CABLE SOCKETS

The mechanical properties of large sockets in which cable terminals are secured with zinc-copper alloy were studied and a design method for this type of socket was proposed. When sockets for large cables are designed by applying the conventional design method, one inevitable consequence is insufficient wall thickness, which leads to large deformations of the socket itself under the cable breaking load. Since the mechanical properties of a large socket are different from those of small one, the conventional design method is inapplicable to such a socket. The new design method studied in this work introduces the concept of rigidity for ultimate strength into large socket design.

A reference shape library for computer aided socket design in above-knee prostheses.

A Reference Library of socket shapes for an Above-Knee Computer Aided Socket Design (CASD) System has been created. This library forms part of a more general CASD System (Dean & Saunders, 1985; Novicov & Foort, 1982). It consists of a matrix of reference shapes representing above-knee socket characteristics and is based upon skeletal structure, residuum length and tissue mass. A set of 27 biomechanical reference shapes in the form of male plaster casts were produced by a combination of CNC milling and traditional artisan techniques. Each reference shape was digitized to obtain its cylindrical coordinates. Cross-sectional areas and tissue distributions within each shape and between the shapes were analyzed, modified and then stored numerically within the computer for further implementation of the CASD System for the above-knee amputees. The creation and the analysis of the reference shape data is described.

Prosthetics, orthotics, and assistive devices. 3. Prosthetics.

This self-directed learning module highlights new advances in prosthetics. It is part of the chapter on prosthetics, orthotics, and assistive devices for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation. This section contains information regarding conventional and myoelectric upper limb prosthetics, above-knee (AK) socket designs and materials, and foot and ankle systems. New advances that are covered in this section include the narrow medial-lateral AK socket, the flexible AK socket, and new prosthetic foot and ankle systems. Proper understanding and clinical application of this technology is essential for the optimal prosthetic rehabilitation of the amputee.

Automated Fabrication of Mobility Aids: Clinical Demonstration of the UCL Computer Aided Socket Design System

1Research Prosthetist with Prosthetics Research Study, 720 Broadway, Seattle, Washington 98122; (206) 328-3116 2Director and Principal Investigator of Prosthetics Research Study in Seattle

Isometric and isokinetic hip abductor strength in persons with above-knee amputations.

Recently introduced prosthetic socket designs for the above-knee amputee (AKA) feature a narrow medial-lateral dimension and emphasize maintenance of the residual limb in full physiologic adduction. Quantitative data on the effect of frontal plane limb position on the isometric hip abductor strength of ten otherwise healthy AKAs were obtained in the standing position. Residual limb isometric and isokinetic abductor strength was also measured and compared with that of the intact limb and with that of ten healthy age-, sex-, and height-matched control subjects using an identical technique. The testing hardware consisted of a modified Cybex II Isokinetic Dynamometer with a custom-made pelvis and trunk stabilizing device. Anthropometric measurements were taken. Results showed an essentially linear increase in residual limb abduction strength with progressive adduction from 30 degrees abduction to 16 degrees adduction. The average increase in abduction torque was .97% (range .29 to 1.5) of the peak neutral position strength per degree of change in femur angle when corrected for the effect of gravity. Similar strength increases with adduction of the femur were found for intact and control limbs. Mean residual limb isometric abduction torque measured 30% less than the intact limb value (p = .0018). The difference between the intact and the control limb mean isometric abduction torques was less than 1%. Isokinetic testing was technically more difficult than isometric testing but revealed similar weakness of the residual limb abductors when compared to the intact and control limbs.

Socket design and cement pressurisation in the Charnley low-friction arthroplasty.

An experimental evaluation was made of the efficacy of an unflanged cup, an ogee-flanged cup and the Exeter pressuriser in the pressurisation of acetabular cement. Only a very modest injection pressure could be generated through an unflanged socket and even this was readily lost as the socket "bottomed out". The ogee-flanged socket gave a consistently high injection pressure which could be maintained throughout the process of polymerisation. The Exeter pressuriser gave marginally better results. Of the two cements tested, Palacos with gentamicin showed better intrusion than CMW Type 1 cement, but it also allowed greater extrusion once pressure was released. The importance of maintaining a continuous pressure on the cement throughout polymerisation is emphasised.

生存率分析法によるＪｕｄｅｔセメントレス人工関節の分析

Judet cementless hip prostheses were performed at the Yamaguchi Central Hospital in 167 hips during the period from 1976 to 1987. Revision surgery was undertaken for socket loosening in nine patients, stem breakages in three. Statistical analysis was performed using the general Wilcoxon test, and the prosthesis survival was estimated using a nonparametric estimation of survival. Total hip arthroplasty may fail by a variety of mechanisms. Failure may be related to prosthetic design, and setting angle of inserted socket. Setting angle of the socket was clssified into three groups. Setting angle was less than 45 degrees in group 1, from 45 to 60 degrees in group 2, and more than 60 degrees in group 3. There was no significant difference in prosthesis survival probabilities among three groups. Robert Judet made socket design better in 1980. There was significantly improved (P<0.001) prosthesis survival in the new type in comparison to the old type. It was suggested that improve of the socket was significant.

Prescription of above-knee and below-knee prostheses.

New developments in socket design, materials and fabrication are briefly reviewed. A series of charts is presented which summarize the below-knee and above-knee prescription procedures followed at the Veterans Administration Prosthetics Center.

Results of the pilot phase of a clinical evaluation of computer aided design of trans-tibial prosthesis sockets.

This study served as a pilot to develop the methodology for a larger number of clinical trials. Ten trans-tibial amputees compared sockets made by conventional methods with sockets made using computer aided socket design (CASD). Prosthetists, paired for experience, fitted each subject with one prosthesis using each method. A preferred socket was selected by the subject on the basis of comfort without knowledge of the method by which the socket was designed. Prosthetists also evaluated the sockets. Three subjects preferred sockets built using CASD and one subject preferred the conventional socket only slightly more than the CASD socket. Six subjects clearly preferred the conventional fitting.

Socket design and manufacturing technique for through-knee stumps.

This paper describes a socket design and manufacturing technique for through-knee stumps, based on 14 years experience with 290 prostheses. The bulbous shape of the stump and its full end-bearing quality requires a socket which has very little resemblance to above-knee sockets. The requirements of the through-knee socket are listed and the manufacturing technique is described and illustrated in detail. Emphasis is put on the quality of the negative plaster mould. The socket is manufactured according to the double wall technique commonly used in below-knee sockets. It provides a maximum of comfort and cosmesis without extra costs.

Theoretical analyses of rock socketed piles : Donald, I B; Sloan, S W; Chiu, H K Proc International Conference on Structural Foundations on Rock, Sydney, 7–9 May 1980, P303–316. Publ Rotterdam: A A Balkema, 1980

Theoretical analyses of pile socket behaviour have been used to illustrate the effects of various assumptions frequently made in socket design. The most important assumption is that of the nature of pore water drainage during loading, and phi = 0 behaviour is significantly different from c - phi or c-phi joint behaviour. Elastic solutions have been extended for a new design method, and expanded to include the important two layer case. Some computational difficulties remain, particularly regarding stresses at the pile extremities, and further work - including non linear elastic analyses for economy and more accurate parameter modelling - is in progress. Correct simulation of joint behaviour is also a complex laboratory and computational problem, but interim results are promising. In spite of these difficulties, it should be added that the programme has been used with great success in aiding decision making for a wide range of practical problems, including piles in layered rocks with weak zones beneath the base, piles in thin, jointed rock layers overlying clay and field tests for rock parameter determination.

A New Socket Design for the Dysplastic Acetabulum in Total Hip Replacement

A special socket was designed by holography for total hip replacement for the treatment of the dysplastic acetabulum and correction of the deformation pattern. Excellent clinical results of 12 cases demonstrate that the special socket design provides good stability as well as favorable redistribution of mechanical forces about the hip joint.

Preliminary Evaluation of DIP/Socket Connection Reliability

The availability and recent use of large-scale integration and field programmable memory dual in-line packages (DIP's) has resulted in increased use of DIP sockets and also increased need for reliability data on DIP/socket connections. This experimental study was implemented to explore the reliability of various DIP/socket combinations in terms of contact resistance performance after being subjected to various environmental tests. The parameters explored were 1) DIP lead material and finishes, 2) socket contact finishes and configurations, and 3) insertion levels of 1, 5, and 15 insertions of the DIP's into the sockets. Three different Dip/socket interfaces were studied: Au/Au, Au/solder, and solder/solder. These were distributed over 20 combinations of 5 DIP's and 4 sockets. Thermal aging, temperature cycling, temperature cycling with high humidity, an industrial atmosphere test, and a control group were the 5 environments used. Although the tests are not complete, the major preliminary conclusions are as follows. 1) High contact resistance at the DIP/socket interface is a significant failure mode for DIPs that are socketed. Proper choice of DIP lead and socket finishes and socket design can reduce the probability of this type failure. 2) The gold/gold contact is the best DIP/socket combination tested. 3) Thick gold plating is superior to thin gold plating. 4) The gold/solder contacts are generally unacceptable. 5) The solder/solder contact did not perform well in the study and its use is not recommended. 6) Increasing the number of insertions of the DIP into the socket generally cause increased contact resistance as environmental tests progress.

Socket design for the above-knee amputee.

Socket design for the above-knee amputee.

Postoperative Dislocation After Charnley Low-Friction Arthroplasty

The dislocation rate after the Charnley arthroplasty with the 22 mm diameter femoral head was 0.8% in 3,820 arthroplasties performed before 1971. Over this era the annual rate ranged from 0.5% to 1.4% without any apparent explanation. Following the routine use of a low position for the socket in the acetabulum and the Long Posterior Wall design of socket, the dislocation rate fell to 0.4% over 4,706 arthroplasties and the annual dislocation rate over 4 years ranged between 0.5% and 0.2%.

Friction and end bearing tests on bedrock for high capacity socket design. Technical note

Friction and end bearing tests on bedrock for high capacity socket design. Technical note

Postoperative Dislocation in the Charnley and Brunswik Total Hip Arthroplasty

An analysis of 351 total hip arthroplasties according to the method and design of Charnley and 194 Brunswik snap-fit deepened socket design failed to show any significant difference in the incidence of dislocation. Neither were the angulation of the acetabular prosthesis in the anteroposterior projection, time after operation, experience of the surgeon and displacement of the greater trochanter significantly related to dislocation. The variables of significance were anatomical superior-inferior position of the acetabular prosthesis and possibly the number of previous operations on the hip joint.

Friction and end bearing tests on bedrock for high capacity socket design: Reply

Rock sockets are used to transfer axial loads to bedrock by a combination of periferal contact bond and end bearing. The load distribution with embedded depth in relation to rock properties actually measured is discussed. Case histories are presented.The results of full scale and bearing and friction tests carried out on various rock types are given. A relation between the unconfined compression strength of rock and the developed concrete to rock bond value is reported.

Friction and end bearing tests on bedrock for high capacity socket design: Discussion

Friction and end bearing tests on bedrock for high capacity socket design: Discussion