Powered Prosthetic Device Improved Ankle Power in Patients With Transtibial Amputations

In patients with transtibial amputation, a powered prosthetic device successfully restored ankle power during stair ascent and demonstrated significantly greater ankle range of motion and power generation. However, it did not reduce the use of hip strategy while ascending stairs and increased compensatory strategies at proximal joints, according to the results of two recent studies.

Stair ascent kinematics, kinetics

Jennifer M. Aldridge, MS, of the department of orthopaedics and rehabilitation at the Center for the Intrepid at Brooke Army Medical Center, and colleagues enrolled 11 participants with transtibial amputation (TTA) in two stair ascent gait analysis sessions, first using energy storing and returning (ESR) prosthetic feet and then using the PowerFoot BiOM. Researchers also collected data from 11 height, weight and gender matched control participants with no current pain or history of major lower extremity injury. Lower extremity peak kinematic and kinetic values were calculated at a self-selected and controlled cadence of 80 steps per minute.

Study results showed an increase in prosthetic limb peak ankle plantarflexion and push-up power when patients used the BiOM. Peak ankle power was not significantly different between patients using the BiOM and the control patients; however, according to study results, the peak ankle plantarflexion was significantly lower than control participants. In both the BiOM and ESR conditions, researchers observed limb asymmetries, including greater prosthetic limb hip flexion and power during stance, and decreased prosthetic limb knee power during stance.

“Device specific training may be necessary to obtain the desired changes associated with added ankle motion and power. Although participants in this study used the device for many weeks as part of their daily activities, recent studies in other patient populations suggest more focused gait retraining may be required to overcome ingrained compensatory gait patterns,” the researchers wrote. “Changes in gait mechanics have been observed when training individuals with amputation using real-time feedback, suggesting gait can be rapidly modified if appropriate feedback is selected. Future research should focus on the development and implementation of device specific training programs to facilitate effective implementation of novel technologies to improve stair ascent.”

BiOM, ESR during walking

In another study, Aldridge and colleagues enrolled 11 participants with unilateral TTA and control patients with no history of musculoskeletal or neurologic impairment. Participants with TTA were prescribed to wear an ESR for a minimum of 2 months before testing. Researchers assessed participants using their prescribed ESR and again with the BiOM after approximately 3 weeks to determine if normalization of gait kinematics and kinetics occurred compared with non-amputee controls. Main outcome measures included gait mechanics, physical performance and user satisfaction.

“As the first commercially available microprocessor device capable of providing powered plantarflexion, the PowerFoot BiOM was compared with commonly prescribed ESR, the contralateral intact limb and non-amputee controls,” the researchers wrote. “We hypothesized that the addition of powered plantarflexion would normalize gait kinematics and kinetics, improve physical performance and increase user satisfaction in individuals with TTA.”

Whereas both the ESR and BiOM demonstrated significantly less ankle range of motion than the control patients and intact limb, the BiOM provided a significantly larger range of motion that that of the ESR limb, according to study results.

The ESR limb generated approximately 40% less peak ankle power at pre-swing vs. the control and intact limbs. However, the BiOM generated significantly greater ankle power, and patients absorbed twice the peak knee power observed in the control and intact limbs. The BiOM generated 45% greater peak hip power at pre-swing compared with the intact limb, and walking velocity increased with the BiOM compared with the ESR and control group. Although researchers found that physical performance measures were not significantly different between the ESR and the BiOM, patients reported a preference for the BiOM over the ESR. — by Casey Murphy

Aldridge JM. Gait & Posture. 2012;36:291-295.
Ferris AE. Arch Phys Med Rehabil. 2012;doi:10.1016/j.apmr.2012.06.009.

Disclosure: Aldridge has no relevant financial disclosures.

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