Design and Evaluation of a Prototype Manually Locking AK Prosthetic Knee for Children
RANDALL N. ALLARD AND DONALD R. CUMMINGS, CP
Young children and particularly those with bilateral above knee amputations attempting to adapt to their first prosthetic knee can benefit from a locking feature.
Availability of functional knee components for children is minimal. Often prosthetic knees for larger children must be downsized and result in a less than anatomically pleasing prosthetic limb. Most commercially available locking knees use an external cable which crosses the knee joint and is sometimes difficult to operate through clothing.
Primary design parameters established by the Research and Prosthetics departments included a prosthetic knee that was smaller than available sizes, lockable through clothing without tools, gait varied by a frictional adjustment and exoskeletal with the same or less labor effort used to fabricate conventional prosthetic limbs.
An aluminum single axis knee was designed two inches wide and two and half inches tall. The prototype can be locked by hyperextending the limb and pushing a button. A friction adjustment is accessible in the finished prosthesis and the limb exhibits greater than ninety degrees of flexion. The knee can be aligned in any reasonable orientation with straps and anchors securing it to a carbon fiber reinforced exoskeletal frame. The finished limb is cosmetically appealing and has a knee cap that resists pinching and tearing of clothes during flexion. To date, a five year old child with bilateral knee disarticulations has been fitted with the prototypes and is progressing well.
Texas Scottish Rite Hospital for Crippled Children, 2222 Welborn Street, Dallas, TX 75219