Thesis
A study of the interface stresses in trans-tibial sockets : a comparison of PTB and hydrocast sockets
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2005
- Thesis identifier
- T11257
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- The concept of loading “pressure tolerant” areas and relieving load from “pressure sensitive” areas of a below knee stump as applied by a Patellar Tendon Bearing (PTB) socket, was based on logical biomechanical principles. (Radcliffe and Foort, 1961) Inconsistencies during rectification of the PTB cast remain a source of error during production of a socket. Kristinsson (1992) described the use of the Icelandic Roll on Silicone Socket (ICEROSS) (or silicone liner). During this casting process, placing a container over the stump allows the air around the stump to be pressurized and thus the cast is formed. Kristinsson (1993) claimed that in most cases, the concept of load transfer to areas such as the patellar tendon, medial flare and condyles of the tibia is ineffective and uncomfortable. His belief is that the most effective socket is one that relies on “hydrostatic principles” for transfer of load. The current study presents a method of producing a socket called ‘Hydrocasting,’ which was originally introduced by Murdoch (1965) as the ‘Dundee socket’. The concept behind the ‘Hydrocast socket,’ whereby water is used as a medium to apply uniform pressure around the stump whilst the applied plaster bandage sets, results in a mould of the stump suitable for socket production with minimal or no subsequent cast rectification. The major difference between the conventional PTB socket and the hydrocast socket is that the hydrostatic cast is minimally rectified or not rectified at all. The aim of this study was to investigate the interface pressure distribution between the residual limb and the prosthetic socket of ten trans-tibial amputees and the principal objectives were (a) to design and develop transducers which would enable simultaneous dynamic measurement of pressure and shear stresses, (b) to determine the variation in pattern of pressure distribution associated with various positions of the patellar tendon bar indent in a trans-tibial socket and (c) to measure stump/socket interface pressure and shear stresses for the PTB and hydrocast socket designs. Two new custom made transducers, in addition to two previously described transducers, for the measurement of stump/socket interface stresses were designed and developed. The transducers, constructed using electrical resistance strain gauge technology, are capable of measuring normal and shear stress simultaneously when mounted on a prosthetic socket. One design of transducer allows the measurement of normal and shear stress to be undertaken, and the other design, in addition, allows the sensing surface at the patellar tendon to be translated by, up to, 10 mm from the neutral position for the purpose of examining the effect of patellar tendon bar indentation on the pressure distribution at the interface. Subjective feedback from all participants indicated that when tendon bar was in the relief position this was preferred. The position of the patellar tendon bar had no significant effect on the pressure distribution around the socket indicating that it is an unnecessary feature, which, is proposed, may be eliminated during manufacture of a trans-tibial socket. The hydrocast socket compared to PTB socket shows a more even distribution of pressure in the socket and the values for pressures and shear stresses are lower. Subjective feedback from all participants also favoured the hydrocast socket. It is believed that lower, more evenly distributed pressure enhances the comfort of the prosthesis user.
- Advisor / supervisor
- Spence, William D.
- Solomonidis, S.E.
- Resource Type
- DOI
- EThOS ID
- uk.bl.ethos.417425
- Funder
Relations
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