Lower Extremity (LE) Technology

We encourage individuals who have experienced limb loss to contact us so we can put you in
touch with others in your situation for individualized counseling. Superior Orthotics and Prosthetics offers exclusive "Free Prosthetic Evaluation Clinics"

Suspension

Anatomical - A type of suspension where the anatomical shape present can be utilized for socket suspension as in ankle disarticulations with a bulbous end or with unique congenitial anomalous residual limbs.

Knee Sleeve - A rubber or other equivalent material, where the knee sleeve is rolled onto the socket first and then after donning the socket, is rolled over the individuals thigh. This is primarily used as an auxillary suspension.

Suction - Atmospheric pressure creates negative pressure on the residual limb inside of the socket to maintain the socket on the limb. This suspension is generally utilized on natural residual limbs where size has stabilized allowing for a long-term socket fit.

Supra Condular Strap - A simple system that utilizes a strap secured to the side of the socket that then buckles snuggly over the proximal portion of the femoral condyles. Waist Belt/Fork Strap - An easy to use system where safety and security are a priority. This system is more bulky and uncomfortable than others, but it offers the benefits of a secure fit with simple donning and doffing and low maintenance requirements.

Mechanical - This system utilizes a roll-on liner ofvarious materials with a pin onthe end of the liner that is placed into a locking mechanism at the distal end of the socket. This system provides enhanced cushioning for the limb and excellent sensory feedback. The drawbacks of the system are increased maintenance for appropriate hygiene, not filed serviceability, and increased learning demands for the user.

Joints/Corset - This type of suspension is quite bulky and is often only indicated for use when necessary. Indications for use are excessive knee instability or residual limb skin that is unable to tolerate applied forces and additional area is necessary over which to distribute forces.

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Socket

PTB - (Patella-tendon Bearing) Design principles include placing pressure on
pressure-tolerant regions of the limb and relieving pressure on pressure-sensitive regions of the limb.

TSB - (Total Surface Bearing) Design principles suggest that forces may be applied over the entire limb, with the magnitudes varying according to the entire limb, with the magnitudes varying according to the anatomy and tissuetype. Most current socket-systems are designed utilizing principles of both PTB and TSB theory and fundamentals, creating a hybrid socket.

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Sach - (Solid ankle cushioned heel) This type is the most frequently prescribed prosthetic feet in the country. This foot is lightweight, durable, and cosmetically enhanced. The foot offers Shock absorption through heel wedge durometer and is low maintenance with excellent stability.

SAF - (Single-axis feet) This foot is generally indicated for Trans-tibila amputees with knee pathology and for increased knee stability for trans-femoral amputees. The stability comes from the graded movement compliance on the sagital plane to plantar flexion and dorsi flexion.

 

MAF - (multi-axis feet) This foot offers accomadation to uneven surfaces for increased stability. The foot requires more maintenance and is generally heavier due to increased parts.

ESF - (Energy storing feet) These feet utilize some type of flexible keel and/or heel that deflects when force is applied, storing energy, and as force is removed units returns to form essentially propelling the limb forward, enhancing limb progression.

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Knee Units

Manual Lock - This knee design has a button or lever that can be activated to lock the knee unit in full extension so that the knee does not bend during any portion of gait. This design is indicated when safety is the ultimate priority. Individuals who have very weak residual limb muscles, limited cognition, and individuals who are missing both lower extremities may utilize a manual lock knee on one side to be able to relax with long periods of sustained activities from a standing position

Single-Axis- The geometric design provides one axis of rotation upon which knee movement occurs. This design is structurally superior and is the lowest maintenance design

Polycentric- This knee design utilizes a complex geometric construction, including multiple linkages, to provide increased mechanical stability and more accurately mimic true anatomic knee range of motion. The prosthetic knee joint movement occurs along multiple axes of rotation.

Swing Phase Controls- This refers to the mechanism provided by the knee unit to regulate the swing phase of gait. The swing phase of the gait cycle when the limb is not contacting the ground. The most common control mechanisms include friction, pneumatics, hydraulics, and microprocessors. The swing phase controls may be implemented with any geometric design of the knee unit.

Friction Knee Control- A series of bushings and pads are adjusted to provide a set level of resistance to the swing portion of gait. Friction control is fixed and constant once set. This type of control is indicated for individuals who will only ambulate at a fixed cadence or one speed.


Pneumatic Knee Control- This control utilizes air pressure contained within a cylinder that can be adjusted with a valve. The control is proportional to the force and velocity of the load applied to the system. This system allows for variable amounts of resistance to gait so that it is responsive to allow for control of gait at different speeds. Due to the inherent limitations of the amount of force that can be generated by air pressure, this system is indicated for variable cadence walkers in the slow to medium speeds and less aggressive ambulators in general.
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Hydraulic Knee Control- This system utilizes a self-contained, adjustable hydraulic unit to regulate the swing phase of the gait cycle. This unit functions in a similar manner to a hydraulic cylinder on a doorway. The unit provides resistance proportional to the speed, force, and direction of the load applied to it. The unit is indicated for individuals with slow to fast cadence tempos and a more aggressive pattern of ambulation.

Microprocessor Knee Control - This system implements a microprocessor inside of the knee unit which constantly monitors the forces placed on the knee joint and the velocity of the movement of the prosthesis in space. This control may be combined with pneumatics or hydraulics, as the microprocessor regulates the prosthesis controls by continuously adjusting the hydraulic or pneumatic swing phase controls. The microprocessor automatically adjusts the air or hydraulic pressure as needed to provide appropriate stability. This is, by far, the superior method of knee unit control, but due to the high costs associated with these knee units it is infrequently utilized, even when it may be appropriate

WASC - (weight-activated stance control) This type of knee system utilized a friction brake system enhanced stance phase stability. When wieght is applied to the prosthesis force is applied to a brake bushing which stabilizes the knee and prevents further knee movement.