Device to monitor sock use in people using prosthetic limbs: Technical report

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Device to monitor sock use in people using
prosthetic limbs Technical report

• Joan E. Sanders, PhD Revathi Murthy, MSE John
  C. Cagle, BSE Katheryn J. Allyn, CPO Reid H.
  Phillips, BSE Brian P. Otis, PhD

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• Aim
• Describe design, results, and recommendations for
  further development of small, unobtrusive
  instrument that clinician mounts on patients
  prosthesis to record sock use between clinical
  visits.
• Relevance
• People with limb loss commonly add or remove
  socks to accommodate changes in residual limb
  size throughout day.
• Practitioner typically has only limited sock-use
  infor-mation (patient self-report) from which to
  optimize prescription.

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Methods

• Passive radio frequency identification (RFID)
  tags taped to prosthetic socks and tag reader
  mounted on external socket surface.
• Testing
• Bench
• Unobstructed detection distance, detection in
  presence of socket materials and human tissue.
• Subject
• Fitting and activity tests with 3 participants
  with unilateral transtibial amputation.

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Results

• Bench testing
• Tag detection independent of sock material or
  thickness for up to at least 1 cm thickness.
• All 4 tags detected using polymer socket but only
  2 using carbon fiber socket.
• Results very sensitive to slight position changes
  of test materials relative to antenna.
• Material (carbon fiber, fleshy and bony human
  tissues) influenced number of tags detected.
• Subject testing
• System recognized socks well with 1 or 2 socks,
  moderately well with 3, poorly with 4.
• Grass, gravel, and inclines did not distort
  performance.

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Conclusion

• RFID technology can effectively monitor sock use
  with prosthetic limbs.
• While high-frequency RFID detected sock presence,
  ultra-high-frequency RFID may be more effective.
• Clinical investigations must determine whether
  and how sock use data help practitioners diagnose
  patients status and needs in order to create
  effective prosthesis prescription.
• Potentially, sock monitor can become clinical
  feedback device to alert patient when sock needs
  to be added or removed.