The Human Foot and Ankle

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Introduction

The human foot and ankle are composed of 26 bones, 33 joints, and more than a hundred muscles, tendons and ligaments. These components work together to provide the body with support, balance and mobility. The foot acts as a “rigid lever and mobile adapter” (Amstrong [Prosthetic feet], 2010). The human foot must be capable of withstanding the body’s weight and functions as a shock absorber (Swierzewski, 2007; NYU, 1990). The prosthetic foot needs to be capable of mimicking the missing natural foot, to make for the most efficient gait pattern. When due to disease, accident or developmental malformation a natural foot is absent a prosthetic foot is used to mimic the missing limb in an attempt to create the most efficient gait pattern. The prosthetist must choose from numerous types of prosthetic feet, depending upon the patient’s physical condition and life-style needs (Swierzewski, 2007).

Gait Cycle

The human gait cycle is comprised of multiple sequential steps. It begins with the heel of the foot contacting the ground and ends when that same foot contacts the ground again (Perry, 1992). The period of the gait cycle that the foot is on the ground is called the stance phase. The period when the foot is in the air is called the swing phase. The phases of the gait cycle are initial contact (IC), loading response (LR), mid-stance (MSt), terminal stance (TSt), pre-swing (PSw), initial swing (ISw), mid-swing (MSw) and terminal swing (TSw). There are three primary functions of the gait cycle, which are weight acceptance, single limb support, and limb advancement. Weight acceptance occurs during initial contact and loading response. During these phases, the limb is stabilized to prevent falling and the foot fun...

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...activities. The main disadvantage of this foot is that it costs more than other feet, and can only be used by patients at the K3 level or above (Lusardi & Nielsen, 2007).

Manufactures

There are several different manufactures of prosthetic feet such as Ossur, Ottobock, Ohio Willow Wood, and SPS. Most companies specialize in adult feet though there are some manufactures such as Ossur that have a special pediatric line. On the companies’ websites, feet are organized based on K level and further categorized based upon male or female. Prosthetic feet come in different lengths in centimeters and left or right. They also are grouped by weight of the patient that can safely use the foot. Some feet come in different skin colors and others have a space between the big toe and second toe to accommodate the user who wants to wear flip-flops or shoes with toe straps.

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