Functional considerations in the fitting of above-knee prostheses.

IN THE fitting of any artificial limb, the goal of the prosthetist is simply to restore to the amputee the ability to perform everyday activities in an easy, natural, and comfortable manner. The basic requirements are therefore three in number—comfort, function, and appearance, the latter embracing both cosmetic appearance and appearance in use. Unless a prosthesis is reasonably comfortable, the amputee will be unable to wear it. Unless it performs the necessary functions with reasonable ease and dexterity, the amputee is not apt to find the device very useful. Unless it is reasonably acceptable cosmetically, and unless it can be operated in a natural manner, the limb is likely to be disagreeable both to the wearer and to his friends and associates. But this seemingly simple set of requirements is vastly complicated by the fact that the three are all mutually interrelated. That is to say, the degree of satisfaction attained in one condition is influenced greatly by the situation prevailing with respect to the other two. Cosmetic appearance, for example, is necessarily limited by details of mechanism, and vice versa. No matter how elaborate a prosthetic device may be, it cannot be made to function properly unless it can be manipulated with ease and without discomfort. And conversely, no device can be comfortable in use unless its functional characteristics are properly integrated with the residual biomechanics of the wearer. Any change aimed at improvement in one condition unavoidably affects the other two—sometimes favorably, sometimes unfavorably. In the lower extremity, cosmesis presents no serious problem. Since it is comparatively easy to fashion an artificial leg to an external shape and appearance more or less like that of its normal counterpart, and since in both sexes the lower extremity may be concealed beneath some sort of clothing, the actual cosmetic properties of a lower-extremity prosthesis amount to refinements to be added after all other requirements have been met. More critical in the lower extremity are comfort, function, and appearance in use. The leg prosthesis is in almost constant service, and it must provide both adequate support and a natural-appearing gait with as modest consumption of energy as possible. In fitting an above-knee limb, therefore, correct practices based on established biomechanical principles are mandatory if success is to be had. Because during all activities the suctionsocket above-knee leg (3,4,19) is controlled by the amputee through the use of remaining hip musculature, every effort must be made to ensure that these muscles are used to the fullest possible extent without causing discomfort. The intent here is to present the basic concepts that apply to the fitting of all