Introduction: Ultrasound is routinely used by rehabilitation specialists to establish differential diagnosis of the residuum’s neuromusculoskeletal issues experienced by former and active Service Members suffering from limb loss1. Ultrasound offers real-time, non-ionizing, unspecialised facility assessment. Conventional imaging modalities record a qualitative static image. More fundamental signal/data display modalities such as the raw radio-frequency signal and A-mode are rarely utilised, although offer specialised opportunities, particularly for quantitative tissue characterisation, when the subject is mobile, and when several anatomical locations need to be synchronously assessed.

Our aim is to develop a wearable ultrasound biosensor system that provides real-time assessment of various anatomical compartment dimensions within a post-amputation residual lower limb of former and active Service Members, termed Dynamic Anatomical Ultrasonography (DAU).

Methods and results: The Olympus Omniscan MX is a highly-portable and rugged ultrasound instrument aimed primarily at the industrial sector. It incorporates the facility to connect up to eight individual single-element ultrasound transducers.

A custom pseudo prosthetic socket was created for an asymptomatic subject, to which were attached two 1 MHz, 19 mm diameter ultrasound transducers, as shown in Fig. 1A. Ultrasound signal data was recorded for a defined measurement period of 10 seconds as the subject repeatedly lifted and lowered their thigh. Utilising the semi-automated time-gate signal detection facility, the depth of the femur bone surface was recorded, shown in Fig. 1B.

Discussion/future directions: We have demonstrated the ability to monitor motions of the femur; of particular note is that measurements were obtained through the socket and silicone liner in addition to the overlying soft tissues. It is hypothesised that knowledge of the dynamic behaviour of the various tissue compartments will improve our understanding of the biomechanics associated with the residual limb of individuals suffering from limb loss and, furthermore, facilitate the fitting and development of bionics prostheses for former and active Service Members2.

Our long-term aim is to investigate whether a combination of ultrasound and mechanical load biomarker data, fed into a ‘Digital Twin’ computational simulation will improve socket design, restore mobility, facilitate return to active duty, and, ultimately, enhance users’ quality of life.

Acknowledgements: This work was supported by the FY19 Defense Medical Research and Development Program through the Joint Program Committee 8 / Clinical and Rehabilitative Medicine Research Program Restoring Warfighters with Neuromusculoskeletal Injuries Research Award (RESTORE) under Award No. W81XWH2110215-DM190659. Opinions, interpretations, conclusions and recommendations are those of the author and are not necessarily endorsed by the FY19 Defense Medical Research and Development Program.