John Fergason

Energy storage and return prostheses: does patient perception correlate with biomechanical analysis?

The development and prescription of energy storage and return prosthetic feet in favor of conventional feet is largely based upon prosthetist and amputee experience. Regretfully, the comparative biomechanical analysis of energy storage and return and conventional prosthetic feet is rarely a motivation to either the technical development or clinical prescription of such devices. The development and prescription of prosthetic feet without supportive scientific evidence is likely due to the conflicting or non-significant results often presented in the scientific literature. Despite the sizeable history of comparative prosthetic literature and continued analysis of prosthetic components, the link between clinical experience and scientific evidence remains largely unexplored.A review of the comparative analysis literature evaluating energy storage and return and conventional prosthetic feet is presented to illustrate consistencies between the perceptive assessments and the objective biomechanical data. Results suggest that while experimental methodologies may limit the statistical significance of objective gait analysis results, consistent trends in temporal, kinetic, and kinematic parameters correlate well with perceptive impressions of these feet. These correlations provide insight to subtle changes in gait parameters that are deemed neither clinically nor statistically significant, yet are perceived by amputees to affect their preference for and performance of prosthetic feet during locomotion. Acknowledging and targeting areas of perceptive significance will help researchers develop more structured protocols for energy storage and return prosthesis evaluation as well as provide clinicians with information needed to enhance the appropriateness of their clinical recommendations. Expanding test environments to measure activities of perceived improvement such as high-velocity motions, stair ascent/descent, and uneven ground locomotion will provide a more appropriate assessment of the conditions for which energy storage and return prosthetic feet were designed. Concentrating research to specific test populations by age or amputation etiologies can overcome statistical limitations imposed by small study samples. Finally, directing research toward the areas of gait adaptation, heel performance, and the temporal release of energy in energy storage and return feet may reinforce the selection and utilization of advanced prosthetic components. These enhancements to current biomechanical analyses may serve to reduce the boundaries of perceptive significance and provide clinicians, designers, and researchers with the supportive data needed to prescribe, design, and evaluate energy storage and return prosthetic feet.

Comparison of satisfaction with current prosthetic care in veterans and servicemembers from Vietnam and OIF/OEF conflicts with major traumatic limb loss

Prosthetic care is a vital aspect of healthcare and rehabilitation for veterans and servicemembers with major traumatic limb loss. Our survey queried 581 veterans and servicemembers with limb loss from the Vietnam and Operation Iraqi Freedom (OIF)/Operation Enduring Freedom (OEF) conflicts. Among survey participants, 78.2% from the Vietnam conflict and 90.5% from the OIF/OEF conflict currently use prosthetic devices. In Vietnam respondents, 78% received prosthetic care from private sources, 16% from Department of Veterans Affairs (VA) prosthetic laboratories, 0.9% from Department of Defense (DOD), and 5% from multiple sources. In OIF/OEF respondents, 42% received prosthetic care from private sources, 9% percent from VA, 39% from DOD, and 10% from multiple sources. Participants identified their satisfaction with current prosthetic devices and prosthetic services. Reports of pain, sweating, skin irritation, and problems with socket fit continue to be significant issues for participants from both conflicts regardless of level of amputation or site of service. In those with upper-limb loss who used myoelectric prostheses, minimal effect on prosthesis use and satisfaction was noted. Among lower-limb loss participants from both conflicts, notable differences existed in prosthesis satisfaction by source of care.

Shape and volume change in the transtibial residuum over the short term: preliminary investigation of six subjects.

A preliminary investigation was conducted to characterize the magnitude and distribution of volume change in transtibial residua at two time intervals: upon prosthesis removal and at 2 week intervals. Six adult male unilateral transtibial amputee subjects, between 0.75 and 40.0 years since amputation, were imaged 10 times over a 35-minute interval with a custom residual limb optical scanner. Volume changes and shape changes over time were assessed. Measurements were repeated 2 weeks later. Volume increase on socket removal for the six subjects ranged from 2.4% to 10.9% (median 6.0% +/- standard deviation 3.6%). Rate of volume increase was highest immediately upon socket removal and decreased with time (five subjects). In four subjects, 95% of the volume increase was reached within 8 minutes. No consistent proximal-to-distal differences were detected in limb cross-sectional area change over time. Limb volume differences 2 weeks apart ranged from -2.0% to 12.6% (0.6% +/- 5.5%) and were less in magnitude than those within a session over the 35-minute interval (five subjects). Multiple mechanisms of fluid movement may be responsible for short-term volume changes, with different relative magnitudes and rates in different amputees.

A noncontact sensor for measurement of distal residual-limb position during walking

A simple noncontact device was implemented for measuring the position of the distal residual limb relative to the prosthetic socket during ambulation. The device was a small and lightweight photoelectric sensor positioned within a frame mounted immediately beneath the socket. Calibration tests showed that the sensor had a displacement range of 60.0 mm. The root-mean-square error for all sources of error considered (different reflective surfaces, peak-to-peak signal noise, drift, nonlinearity, different surface tilt angles, surface curvature, and wetness [simulating sweating]) was <1.95% full-scale output. We used the sensor in a preliminary study on a unilateral, transtibial amputee with diabetes to assess pistoning during ambulation. Results showed an average 41.7 mm proximal displacement during swing phase relative to stance phase. When the subject was walking on a flat surface, pistoning was significantly less (p = 0.000) with a supracondylar strap compared with no supracondylar strap, although the difference was not substantial (0.8 mm). A 5 min rest period caused the limb to displace proximally in the socket approximately 4.8 mm during subsequent walking trials, possibly reflecting limb enlargement and thus a more proximal position in the socket after the rest period. The device can potentially be used in prosthetics research for evaluating clinical features that may affect limb position and pistoning and thus fit.

Testing of elastomeric liners used in limb prosthetics: classification of 15 products by mechanical performance.

The mechanical properties of 15 elastomeric liner products used in limb prosthetics were evaluated under compressive, frictional, shear, and tensile loading conditions. All testing was conducted at load levels comparable to interface stress measurements reported on transtibial amputee subjects. For each test configuration, materials were classified into four groups based on the shapes of their response curves. For the 15 liners tested, there were 10 unique classification sets, indicating a wide range of unique materials. In general, silicone gel liners classified within the same groups thus were quite similar to each other. They were of lower compressive, shear, and tensile stiffness than the silicone elastomer products, consistent with their lightly cross-linked, high-fluid content structures. Silicone elastomer products better spanned the response groups than the gel liners, demonstrating a wide range of compressive, shear, and tensile stiffness values. Against a skin-like material, a urethane liner had the highest coefficient of friction of any liner tested, although coefficients of friction values for most of the materials were higher than interface shear:pressure ratios measured on amputee subjects using Pelite liners. The elastomeric liner material property data and response groupings provided here can potentially be useful to prosthetic fitting by providing quantitative information on similarities and differences among products.

Effects of fluid insert volume changes on socket pressures and shear stresses: case studies from two trans-tibial amputee subjects.

Fluid inserts potentially help to overcome prosthetic fit problems resulting from stump volume change. The purpose of this investigation was to add fluid to fluid inserts positioned on the inner socket walls of trans-tibial prostheses and to assess their influence on socket stresses. Pressures and shear stresses were measured at 13 sites on the sockets of two trans-tibial amputee subjects while they ambulated at their self-selected walking speeds. Stresses at the transducer sites generally increased with greater fluid addition and, interestingly, both subjects found relatively high fluid insert volumes most comfortable. The magnitudes of stress change were larger than those resulting from alignment, cadence, and componentry changes as reported in the literature. Possible explanations for why subjects found settings that induced higher measured socket stresses more comfortable than those that induced lower measured stresses include: A reduced shear: pressure ratio; the short duration of the study; and reduced stresses at sites not monitored with transducers.

Interface pressure and shear stress changes with amputee weight loss: Case studies from two trans-tibial amputee subjects

Interface pressures and shear stresses were measured at monthly intervals on two trans-tibial amputee subjects who lost more than 12% of their body weight over the course of the study. For one subject interface pressures and shear stresses during the weight-acceptance phase of gait decreased over the study interval at all 13 sites monitored, while the other subject experienced increased pressures distally but decreased pressures proximally. Subjects’ stumps appeared to atrophy over the study interval, increasing distal end and patellar tendon loading, but not increasing interface shear stresses at other locations. Adding socks at the end of the study did not return interface pressures to first session values at all sites. It is expected that local stump shape changes occurred, causing a non-uniform change in interface stress patterns.

Custom design in lower limb prosthetics for athletic activity.

In summary, the prosthetist is the best source of information with regard to the fast-changing lower extremity prosthetics technology for sports. The needs and desires of the amputee should be outlined and balanced with the cost of the desired components and design. In many cases, one carefully designed prosthesis can serve in dual roles for everyday ambulation and certain athletic activities. In other cases, the amputee is limited severely by a prosthesis that is not designed for a specific activity. Using a prosthesis for activities that it was not designed to accommodate can cause physical injury to the amputee as well as structural failure of the device. A properly designed and fitted prosthesis can open a whole new world of activity to the amputee and helps him or her to reach the desired a vocational goals.

Prosthetic Management of the Burn Amputation

Amputations as a result of thermal or electrical burns present a unique challenge that requires a coordinated effort by the rehabilitation team. Complications of surface and deep tissue injury require adjustment to the more standard approaches to prosthetic provision. Accommodations for the complications of joint contracture, skin adhesions, sensation compromise, skin grafts, and muscle flaps must be made by the treating clinicians. Differences in the treatment timelines, socket designs, material options, and component choices are discussed to familiarize the team for optimization of function in this difficult treatment scenario.

Contemporary Students: Learning Styles and Teaching Strategies

Adult learners and career change students are increasingly common in prosthetic and orthotic education. This may be attributed to the relative obscurity of the profession within the allied health arena. Potential students are often introduced to the field through personal experience. The student may know someone in need of services, have obtained services themselves, have had professional or personal contact with a prosthetist-orthotist, or have had other casual circumstances with someone involved in prosthetics or orthotics. (J Prosthet Orthot. 2002;14:71–74.) KEY INDEXING TERMS: Adult learner, prosthetic and orthotic education, web based resources, learning styles, teaching