A novel pivot ankle/foot prosthesis reduces sound side loading and risk for osteoarthritis: a pragmatic randomized controlled trial

Changes in activities-specific balance confidence of active unilateral transtibial prosthesis users after provision of a self-aligning ankle foot

BACKGROUND

Self-aligning ankle feet have an increased range of motion and are marketed to improve compliance over uneven terrain and increase function and balance; however, much of the existing literature focuses on the biomechanical aspect of these prostheses as opposed to patient-reported measures.

OBJECTIVE

To compare activities-specific balance confidence (ABC), health-related quality of life (HR-QoL), perceived mobility, gait speed, and step length before and after provision of a self-aligning ankle foot in the active unilateral transtibial prosthesis user.

STUDY DESIGN

Retrospective analysis of prospectively collected data.

METHODS

Patient-reported and functional measures were captured for 85 users who were provided with a self-aligning ankle foot. Measures were recorded immediately before self-aligning ankle foot provision and again at 6 months afterward. The primary outcome was the ABC Score, along with the following secondary measures; HR-QoL using EQ-5D-5L Health Index Prosthetic Limb User Survey of Mobility and 10-meter timed walk test.

RESULTS

The median age of the cohort was 55.2 years old and 71% were males, with the majority having their transtibial amputation due to trauma. There was a statistically significant improvement in ABC from 76 to 86% (p < 0.001) with a medium effect size. There was no statistically significant improvement in HR-QoL (p = 0.051), Prosthetic Limb User Survey of Mobility (p = 0.043), time taken to walk 10 m (p = 0.15) and step length (p = 0.003).

CONCLUSIONS

Self aligning ankle feet increased ABC and step length with no detrimental effect on HR-QoL, perceived mobility or walking speed in those with a unilateral trans-tibial amputation.

Design and optimization of a new integrated hip and knee prosthesis structure

BACKGROUND

Conventional hip disarticulation prostheses (HDPs) are passive devices with separate joint structures, limiting amputees' ability to control and resulting in abnormal gait patterns. This study introduces a new HDP integrating the hip and knee joints for amputees' natural gait.

METHODS

The new HDP restores the physiological rotation center of the hip with a remote center of motion (RCM) structure, and simulates the knee motion with a four-bar structure. Nonlinear programming was employed to optimize the hip-knee joint structure. A hybrid multi-objective drive structure with a series-parallel connection was also designed to ensure motion synergy between the hip and knee joints. Finally, a prototype of the prosthesis was tested using the HDP test system.

RESULTS

The optimization results demonstrate that the new HDP accurately restores the rotation center of the femur in amputees, with the knee's instantaneous center of rotation (ICR) trajectory closely resembling that of the human knee (Pearson correlation coefficient is 0.999). The study shows that the new HDP achieves a motion reproduction accuracy of over 95% for the human hip joint at walking speeds above 1.5 km/h, 38% higher than conventional prosthesis. Similarly, at the same walking speed, the new HDP replicates the motion of the human knee at 82.89%, surpassing conventional prosthesis by 57.85%.

CONCLUSIONS

The new HDP restores symmetry and replicates synergistic movement in amputees' lower limbs, exhibiting superior movement characteristics compared to conventional prostheses. This innovative HDP has the potential to enhance the quality of life for amputees.