Clinical Perspectives on the Prescription of Prosthetic Foot-Ankle Mechanisms

Donald Shurr, CPO, PT

Determining foot-ankle components to be prescribed for the amputee is a process that involves numerous people and varies from location to location. The decision-making group may include the patient and his or her family, a surgeon, physiatrist, physical therapist, occupational therapist, engineer, nurse, and a bursar, who acts on behalf of the involved payer. This bursar may be educated about prosthetic components, or may be working from contract prices or fiscal caps.

In this variable context, the medical team is then responsible for recommending and providing the most appropriate prosthetic components for each amputee. This is generally based on the known and available information including the amputee's needs, goals, and desires. This process calls upon the best knowledge, experience, bias, and value each team member can contribute.

Theoretically, the decision about the entire device, including the foot and ankle mechanism, should be influenced by the best and most current published literature. It is for this reason that the SSC has asked the question, "Does a correlation exist between the available scientific measurements and the actual clinical methods used to recommend footankle systems for specific amputees?"

The intuitive answer (based on the author's own 35 years of working in this area and a review of the literature) is that very little clear correlation exists.

To gain further insight into how practitioners tend to recommend components, the author surveyed 11 ABC-Certified Prosthetists from a variety of backgrounds. These included a director of a prosthetic education program, a biomedical engineer, clinicians with 35–45 years of clinical experience, a prosthetist-researcher, and a practitioner who was also a bilateral amputee. Practitioners were asked independently to list 10 considerations they considered most critical when recommending a foot-ankle mechanism for their patients. The author then grouped these responses from the most commonly cited considerations to the least. (Numbers in parentheses indicate how many practitioners listed a criterion among their "top ten.")

Patient weight (7)
Stated activity goals (6)
Potential level of activity (6)
K level (6)
Length of residuum (5)
Occupation (4)
Cosmesis (4)
Prosthetist experience (3)
Motivation of patient (3)
Compatibility with other components (3)
Weight of foot (3)
Contralateral limb condition (2)
Durability of foot (2)
Muscle-limb strength (2)

Factors receiving one response each included physical endurance, type of prosthetic knee, heel height, discount program, ease of maintenance, informed patient preference, medical history, amputation cause, walking speed, and findings from the physical examination.

Given that 25 different responses were offered, this informal and admittedly anecdotal survey suggests that there was very limited agreement from one practitioner to another about primary influences on the selection of foot-ankle mechanisms. It is also interesting to note that none of the 11 practitioners mentioned that his or her decision-making process was influenced by any specific evidence-based publication or text related to prosthetic foot-ankle studies.

Any correlation between scientific study and the decisionmaking process is not at all clear. However, a review of the literature reveals that many of the concepts that practitioners in the author's informal survey used to recommend feet, are in fact reflected-although not ranked in the same order of significance-by scientific literature.

The decision-making points drawn from this author's summary of practitioners' "top ten" lists are recognizable in many studies. For example, during the subjective feedback phase of their work related to energy-storing feet, Nielsen et al.¹ identified both walking speed and stability as significant issues. They found walking downhill to be easier with a solid ankle cushioned heel (SACH) foot. Torburn et al.² found amputee speed and cosmesis were key reasons amputees preferred certain feet. Postema et al.^3,4 reported no clear preference based on age for energy storage and return (ESAR) feet over conventional feet. But he also noted the conventional foot (SACH) resulted in greater fatigue at faster walking speeds when compared to the ESAR foot. Menard and Murray⁵ reported that walking speed and endurance were better using the ESAR foot, but descending stairs was worse. Murray et al.⁶ reported results of a patient questionnaire naming recreation and endurance as key patient concerns in foot selection. Descending stairs was reported to be easier with the ESAR foot, a finding different from Neilsen et al.¹ Mizuno et al.⁷ reported that the floor reaction forces are influenced by the physical characteristics of the prosthetic foot; the length of the residual limb, the muscle strength of the lower limb, and the time since amputation. In this study the nonaxial (ESAR) feet (Safe II and Seattle Light) were preferred by those patients (transtibial) older than 50 years.

The relevant literature concludes that for whatever reason or reasons, amputees and prosthetists seem to prefer the ESAR foot to the conventional SACH foot. Although descriptive, perceptive, and yes, some evidence from scientific measurement exists, it seems that most practicing prosthetists do not rely strongly or uniformly upon this information when recommending feet for their patients in their practices. More questions than answers remain. As for the question regarding research and how it relates to clinical decision making, perhaps it can be said that some reciprocal influence, rather than a correlation, exists.

Correspondence to: Donald Shurr, CPO, PT, American Prosthetics, Inc., 3828 Cedar Drive NE, North Liberty, IA 52317–9213; e-mail: .

DONALD SHURR, CPO, PT, is affiliated with American Prosthetics, North Liberty, Iowa.

References:

Nielsen DH, Shurr DG, Golden JC, Meier K. Comparison of energy cost and gait efficiency during ambulation in below-knee amputees using different prosthetic feet. J Prosthet Orthot 1988; 1:24–31.
Toburn L, Powers CM, Guiterrez R, Perry J. Energy expenditure during ambulation in dysvascular and traumatic below-knee amputees: a comparison of five prosthetic feet. J Rehabil Res Dev 1995;32:111–119.
Postema K, Hermens HJ, de Vries J, et al. Energy storage and release of prosthetic feet. Part 1: Biomechanical analysis related to user benefits. Prosthet Orthot Int 1997;21:17–27.
Postema K, Hermens HJ, de Vries J, et al. Energy storage and release of prosthetic feet. Part 2: Subjective ratings of 2 energystoring and 2 conventional feet, user choice of foot and deciding factor. Prosthet Orthot Int 1997;21:28–34.
Menard MR, Murray DD. Subjective and objective analysis of an energy-storing prosthetic foot. J Prosthet Orthot 1989;1: 220–230.
Murray DD, Hartvikson WJ, Anton H, et al. With a spring in one's step. Clin Prosthet Orthot 1988;12:128–135.
Mizuno N, Aoyama T, Nakajima A, et al. Functional evaluation by gait analysis of various ankle-foot assemblies used by below-knee amputees. Prosthet Orthot Int 1992;16:174–182.