Compared with an energy-storing and energy-returning prosthetic device, a powered prosthetic device demonstrated significantly greater ankle range of motion and power generation, while the uniarticular function of the powered prosthesis may cause proximal joint asymmetries as well as the introduction of additional asymmetries, according to recent study results.

“Prosthetic devices are designed to enable individuals with amputations to successfully return to functional and recreational activities. Many of these devices, particularly those for individuals with transtibial amputations, do not fully mimic the physiologic function of unimpaired limitations,” the researchers wrote. “A prosthetic device capable of providing powered plantarflexion was recently commercially released. The purpose of this investigation was to determine whether providing powered plantarflexion normalizes lower extremity gait kinematics and kinetics, improves physical performance and increases user satisfaction in individuals with transtibial amputation.”

BiOM vs. ESR prosthetic device

To compare the PowerFoot BiOM prosthesis and an energy-storing and energy-returning (ESR) prosthesis, researchers assessed young individuals with traumatic transtibial amputation and compared them with matched controls with no history of musculoskeletal or neurologic impairment. Main outcome measures included gait mechanics, physical performance and user satisfaction.

Researchers found that the powered prosthesis ankle range of motion (ROM) was significantly larger vs. the ESR limb. However, according to study results, both devices demonstrated significantly less ankle ROM compared with the control and intact limbs. The ESR prosthesis also generated approximately 40% less peak ankle power at preswing, whereas the powered prosthesis generated significantly greater peak ankle power than control and ESR limbs. Consequently, the powered limb absorbed twice the peak knee power observed in the control and intact limbs, according to researchers. Compared with the intact limb, the BiOM peak hip power generation was approximately 45% greater at preswing.

According to the researchers, “small and nonsignificant differences between the BiOM and ESR conditions were observed in the physical performance measures. The lack of statistical differences may, however, reflect the physical fitness of our population rather than any device specific influence.”

Overall, although both BiOM and ESR prostheses showed similar physical performance scores, Prosthetic Preference Questionnaire responses indicated that amputees preferred the BiOM. Researchers believe that the addition of plantarflexion power and its perceived effect on physical function is the reason for BiOM preference in this amputee population, according to anecdotal participant feedback.

Study limitations

The researchers reported several study limitations. First, the researchers observed military personnel with transtibial amputation who had received months of intensive rehabilitation, which made them more likely than a civilian amputee to adapt to the loss of a limb. Therefore, the findings of the study may not be applicable to the general population. No formal training protocols have been established since the initial clinical release of the PowerFoot BiOM prosthesis. According to the researchers, although participants received initial training during the fitting process, additional intensive device-specific training may be necessary to fully utilize BiOM functionality.

Interindividual variability was possibly increased because participants wore different ESR prostheses. However, this variety of ESR devices increases external validity.

Finally, the researchers believe that including electromyography analysis, as well as metabolic and effort analysis could be useful in overall observations.

“The addition of electromyography analysis could be used to better characterize the compensatory strategies observed. Likewise, metabolic and effort analysis of physical performance may be useful in identifying changes not captured by standard biomechanical techniques,” the researchers concluded. — by Casey Murphy

For more information:
Ferris AE. Arch Phys Med Rehabil. 2012;93:1911-1918.

Disclosure: The researchers had no relevant financial disclosures.

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