Technical Note: An Alignment Alternative for Spring Lite and Flex Feet

Jeffrey S. Lutz, C.P.O.

The advantages that carbon fiber shank/ foot systems have over conventional prosthetic feet have been discussed at great length since their introduction. Today it is generally accepted that the Spring Lite and Flex Feet can benefit almost all amputees, regardless of their activity level.

Prosthetists working with these feet have watched these systems evolve into dependable, cosmetic and extremely functional alternatives to more conventional prosthetic fittings. There are presently several ways to align the systems, including a customized Flex Foot fixture and Otto Bock endoskeletal components that can be adapted to either system. These alignment fixtures do work; however, both are somewhat limited in the alignment possibilities that the prosthetist can achieve without rebonding the socket and zeroing out the particular alignment instrument. We were forced to do this several times at our facility.

The protocol for an alignment fixture to be used with these systems is as follows:

Medial-Lateral adjustment (not incremental)
Anterior-Posterior adjustment (not incremental)
Rotation (wide range)
Flexion-Extension (wide range)
Adduction-Abduction (wide range)
Ability to be removed in transfer for weight savings

The alignment device that our facility is using is the Staros-Gardner unit, manufactured by USMC (part #P12-400-OOO). This device provides all the above criteria and has withstood the test of time as a reliable alignment tool.

The bottom portion of the Staros-Gardner unit is pre-drilled and tapped for the same Otto Bock bolt pattern that both the FlexFoot and Spring-Lite systems use. The Staros-Gardner is bolted directly to the top of the attachment plate supplied with the foot.

The below-knee socket is then bench aligned on the foot, using a 1" wood block on top of the Staros-Gardner unit that has been recessed to accept the socket approximately 5/8". It is important that the wood block be secured with #8 wood screws in all of the holes provided.

The entire alignment system (including recessed wood block) will occupy approximately 1-3/8", therefore, when ordering the foot, 1-3/8" should be subtracted from the overall length of the shank.

The dynamic alignment is done according to the foot manufacturer's guidelines and accepted prosthetic practice. Using this technique, the alignment potential is virtually unlimited, and the prosthetist has the ability to "go a little farther than needed" in each plane to ensure that the best possible alignment has been achieved.

The prosthesis is then transferred, replacing the Staros-Gardner unit with a cut-down Otto Bock wood block (part #5R1), and the socket is foamed in place.

The finished prosthesis is at the patient's optimal alignment and its weight is minimal.

Jeffrey S. Lutz, C.P.O., is with I.E. Hanger, Inc., 417 Evangeline Twy., NE, Lafayette, LA 70501.