10 Questions You Should to Know about sach foot
The SACH (Solid-Ankle Cushion-Heel) Foot
Anthony Staros
Summary
On May 24, the Committee on Prosthetics Research and Development of the National Academy of Sciences recommended approval for the production models of the SACH Foot for adult male amputees. Plate A shows one of these newly accepted prosthetic components, which eliminates the need for a prosthetic-ankle joint.
With its acceptance, tentative manufacturing specifications and finalized instructions for installation and adjustment of the SACH Foot were released. A pre-shaped oversize foot is now being manufactured under detailed specifications. The installation and adjustment instructions describe sizing, ordering criteria, final shaping, and assembly of the SACH Foot to prostheses.
Introduction
The basic functional principles of the SACH Foot are well-established within prosthetic technology. Numerous foot designs have been in existence for some time. However, rigorous development and evaluation conducted within the Federal Government's Artificial Limb Program have led to the creation of a generally acceptable manufactured design—the SACH Foot for adult male amputees. Although its design appears straightforward, it delivers many of the essential functions required of prostheses. Faulty construction or incorrect shaping and installation can limit function and lead to premature structural failure. The Artificial Limb Program therefore recommends detailed manufacturing specifications and precise installation instructions. Adherence to these specifications by manufacturers and instructions by prosthetists promises a consistent, reliable product from the SACH Foot.
Development of the SACH Foot
A. A. Marks patented an artificial foot in which no ankle joint was employed, relying instead on rubber layers to provide necessary flexibility for toe action, especially during toe-off. The core was crafted from wood or another suitable material to enable a smooth "rocker" action during walking.
In another patent, G. E. and W. L. Marks described a similar design integrating an inelastic core alongside a rubber heel, which included a spring to enhance functionality.
Designers noted that the foot provides superior actions under pressure, greatly enhancing wear comfort and functionality. They also noted the potential use of softer materials for improved comfort and noise reduction, which proved beneficial in various limbs shops internationally.
J. Foort and C. W. Radcliffe from the University of California (Berkeley) created the initial prototypes of the modern SACH Foot, focusing on lightweight and durable materials to improve performance and mitigate structural issues noted in previous designs.
Some Advantages of the SACH Foot
The absence of mechanical articulation in the prosthetic foot-ankle area mitigates maintenance concerns associated with frictional wear such as noises and instability. Additionally, design flaws in traditional rubber bumpers have often resulted in repeated adjustments and inconveniences for patients. By directly assembling the SACH Foot to the prosthetic shank, these issues are resolved while ensuring essential foot-ankle functions.
At heel contact, the cushion absorbs shock effectively, mimicking ankle action. Weight transitions smoothly from heel to toe as the amputee walks, while the internal core of the SACH Foot facilitates this rollover action. Importantly, the design minimizes energy expenditure during ambulation, especially on inclines.
Specifications of the SACH Foot
Tentative specifications have been developed for the SACH Foot's manufacture, requiring preshaped oversize designs. It must be shaped appropriately to avoid adverse functional impacts from shoe constraints. The heel cushion, toe section, and arch area require careful shaping for optimal fit. Prosthetists will acquire SACH Feet manufactured according to specified patterns, which will assist in the final modifications necessary for shoe fitting.
The manufacturing specifications also outline heel cushion compression properties and overall dimensional requirements. Regular testing ensures adherence to quality standards, allowing for early corrective actions to avoid broader issues.
I. Functional Characteristics
The SACH Foot is designed to deliver shock absorption and mimics normal ankle action without requiring an articulated joint. Its functionality arises from a cushioning wedge and a keel shaped for rocker action. This design approach eliminates common discomforts experienced with conventional articulated feet.
During ambulation, the heel cushion compresses, allowing smooth transitions that mirror natural gait patterns while promoting even weight distribution.
II. Sizing and Ordering Specifications
SACH Feet are available in oversize blanks across specific shoe-size ranges. Each size range maintains a standard keel size, with variations in heel cushion stiffness to cater to individual preferences. This overlap aids in adjusting for height differences among amputees.
III. Shaping
Careful shaping of the SACH Foot is critical, influencing both function and appearance. Attention should be specifically directed at the heel cushion, the arch's surfaces, and the toe section. Minor contour alterations may be necessary for fit, but the lower contour of the heel must remain unchanged.
IV. Installation
The SACH Foot attaches to a wooden shank using a 3/8" steel carriage bolt embedded in the keel. An allowance for extra length is necessary due to material compression under load. Post-adjustments, the foot is adhered in place.
V. Adjustments
Two types of adjustments are available: changes in heel cushion stiffness and thickness. These play crucial roles in ensuring optimal performance and comfort. Careful evaluation is necessary to manage heel elevation and aspire to maintain an effective compression state of the heel cushion for each amputee.
The company is the world’s best sach foot supplier. We are your one-stop shop for all needs. Our staff are highly specialized and will help you find the product you need.