A Novel Measurement Device for Volume Management in Lower Limb Amputees: A Technical Note

Abstract

Many amputees suffer from irritation and wounds as a result of poor residual limb volume management. Reasons contributing to failure to maintain volume properly include peripheral neuropathy, cognitive impairment, and social/cultural issues. Amputees commonly use socks of various thicknesses to account for diurnal limb volume loss. However, data relating to sock compliance is lacking due to an absence of a reliable way to collect usage data. A device was fabricated utilizing wireless RFID and socket-limb interface force detection technology to track sock usage and activity of an amputee. Pilot data was collected through both in-lab and out-of-lab protocols. The collected data showed encouraging results tracking interface force data, however accurate sock data collection was difficult. Suggested solutions include designing a more effective antenna and using the interface force data to detect limb presence to start a tag accumulator algorithm. Clinical applications for the Sock Monitor include intervention through alerting the amputee of a need for a sock change before tissue damage occurs and evidence for prosthetists to justify insurance reimbursement for components and socket replacements. The next step is to use a new prototype with better hardware and firmware to collect real-world usage data from a large group of amputees. A predictive model will be made and implemented to determine if intervention in sock usage improves comfort and limb tissue health.

Keywords: RFID; monitoring; prosthetics.

Fig. 1.

Disassembled view of components posed for documentation, FSR and antenna wires not shown. Quarter is shown for size comparison.

Fig. 2.

Block diagram of Sock Monitor system.

Fig. 3.

Sock Monitor mounted to transtibial prosthesis before wrapping applied to pylon and sensor box.

Fig. 4.

Subject 1 FSR data from in-lab testing.

Fig. 5.

Subject 1 Sock usage from in-lab testing.