Review Question - QID 265

Articulated dynamic-response prostheses have replaced SACH prostheses as the standard foot. Alterations in the design of the keel have provided additional benefits such as increased inversion and eversion. A shortened keel articulated dynamic-response foot would be best for this patient by providing increased motion, stability, and allow negotiation of uneven surfaces.

Romo and Duane authored a review article describing the various prostheses as well as pros and cons associated with each. They state the articulated dynamic prosthesis incorporates axial joints to provide articulation rather than solely relying on keel deformation to provide dorsiflexion in the stance phase of gait. Once the patient has reached the end of range of motion allowed by the articulation, the keel may deform with a spring-like dynamic response. The keel deforms under load, becoming a spring and allowing dorsiflexion to provide a springlike response for push-off. Most dynamic-response feet have a flexible keel. These characteristics make a flexible keel articulated dynamic-response prosthesis ideal for accommodating uneven surfaces. The addition of a sagittal split keel allows for more inversion and eversion allowing even better navigation of uneven terrain.

Illustration A is an example of a lengthened keel nonarticulated dynamic-response foot. Illustration B is an example of a shortened keel nonarticulated dynamic-response foot. Illustration C is an example of a SACH foot prosthesis. Illustration D is an example of a shortened keel articulated dynamic response-foot with a sagittal split.
(Romo and Duane; Specialized Prostheses for Activities, Clinical Orthopaedics and Related Research: April 1999)

Incorrect Answers:
Answer 1: A single axis foot only allows for dorsilexion and plantar flexion, and has poor cosmesis and durability.
Answers 2 & 3: A nonarticulated dynamic response foot provides a spring-like effect but does not provide adequate inversion/eversion to efficiently manage uneven terrain.
Answer 5: A lengthened keel articulated dynamic-response foot is indicated for very high level demand athletes whereas a shortened keel is indicated for moderate level ambulators and outdoor activities such as hiking.