Alignment of the above-knee prosthesis.

Alignment will be discussed in terms of what happens as a result of specified changes in the relative positions of the prosthetic components. As a person walks on his prosthesis the conditions which predominate at various stages can be identified: (a) the conditions of no-load, or swing phase, (b) the conditions under which there is full loading or stance phase, (c) the capacity to control the prosthesis easily or voluntary control (d) the conditions under which little or no control can be exerted. Alignment will be considered with these conditions in mind in the hope that visualization of what is happening as you work toward optimizing comfort, saving energy and normalizing the appearance of gait will be made easier. As you watch the amputee walk, everything happens at great speed, and there is need for some sort of anchorpoints for your observations. You depend on motions—motions en masse, motions between the prosthesis and the wearer, motions between the prosthetic parts. You may however, develop the habit of feeling the effects of what you see as forces. As I watch a person walk with the view to changing his alignment I imagine how the prosthesis or its parts would bend if they could, and how they would want to move to modify this tendency if they could.From this I get clues as to what changes to make. I have boiled it down to just a few things which I consider for change: 1. Length of the prosthesis. 2. Foot position—front, back, inward, outward. 3. Foot angle—toe up, toe down, toe in, toe out. The stump is considered as the datum or reference system to which the position of parts is referred. As for knee pivot position, (4) I think of this only in terms of the internal or external angulation of the axis from right angles to the line of progression. The forward or backward position has influence, but the prosthetist can easily pre-set this position with respect to the stump and leave refinement of stability to the positioning and angulation of the foot. Similarly, inversion and eversion relate more to cosmesis than function and can be neglected except in that sense. Let us consider the effects of the changes we can make to the length, position and angle of the various parts; and as we do so, let us use the motions for clues while we sense these as forces …