The prosthetic sock monitor prototype is mounted on the anterior lateral surface of the socket with Velcro straps. The reader antenna (dashed line) is contained within the box in this prototype. Image courtesy of the Journal of Rehabilitation Research & Development.
One of the challenges prosthetists face when helping their prosthetics patients solve residual limb volume-management issues is that information about the patient’s prosthetic sock use outside of the clinic is limited to verbal input from the patient. Particularly for people with cognitive issues, an accurate account of how many and which socks were worn each morning and afternoon over a period of days or weeks is difficult to create. A technical report published in the Journal of Rehabilitation Research & Development (Vol. 49 No. 8, 2012) describes a prototype device developed by researchers at the University of Washington, Seattle, that uses radio frequency identification (RFID) technology to continuously monitor prosthetic sock use. With improvements, the technology described in the report may help practitioners by providing this information, including timing and consistency of daily sock-ply changes.
The long-term goal is the development of a small, unobtrusive instrument that a clinician mounts on the patient’s prosthesis to record sock use continuously between clinical visits.
According to the report, passive RFID tags were taped to prosthetic socks worn by subjects with transtibial limb loss, and a high-frequency RFID reader and antenna were placed in a portable unit mounted to the outside of the prosthetic socket. Bench testing showed the device to have a maximum read range between 5.6cm and 12.7cm, depending on the RFID tag used. Testing in a laboratory setting on three participants showed that the device correctly monitored sock presence during sitting, standing, and walking activity when one or two socks were worn but was less reliable when more socks were used.
While the efforts described in the report demonstrate that a sock monitor based on RFID technology is possible, the researchers said that challenges remain. Accurate detection was sensitive to orientation of the tag relative to the reader, presence of carbon fiber in the prosthetic socket, pistoning of the limb in the socket, and overlap among the tags. The researchers said that use of ultra-high-frequency RFID may be more effective. In addition, the design described in the report operates for ten hours of continuous use, so a longer-lasting power source would need to be incorporated to allow for extended monitoring.
In addition to providing clinical data to practitioners, the researchers said there is potential for the prosthetic sock monitor to be extended into a feedback device to alert a patient when a prosthetic sock needs to be added or removed, or to help patients with diabetes-related foot issues monitor sock use.
Editor’s note: This story was adapted from materials provided by the Journal of Rehabilitation Research & Development.
