Rate-independent characteristics of an arthroscopically implantable force probe in the human achilles tendon

Gregory W. Hall, Jeff R. Crandall, David V. Carmines, Joseph E. Hale

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


The effect of loading rate on specimen calibration was investigated for an implantable force sensor of the two-point loading variety. This variety of sensor incorporates a strain gage to measure the compressive load applied to the sensor due to tensile loading in a soft tissue specimen. The Achilles tendon in each of four human cadaveric lower extremities was instrumented with a force sensor and then loaded in tension using a materials testing machine. Each specimen was tensile tested at three different displacement rates, 0.25, 2.5 and 12.7 cm s-1, corresponding with mean loading rates of 33.8, 513.2, and 2838.6 N s-1, respectively. A calibration curve relating the force sensor signal and applied tendon tension was generated for each specimen/displacement rate combination. For each specimen, calibration curves were compared by calculating an RMS error for the entire data set (ε(RMS) = 1.6% of the full toad value) and a coefficient of determination, R2, of a curve fit through all of the data (R2 = 99.6%). Over the range of rates tested, no measurable change in sensor sensitivity due to loading rate was observed. Hysteresis for all displacement rates was on the order of 2.4%.

Original languageEnglish (US)
Pages (from-to)203-207
Number of pages5
JournalJournal of Biomechanics
Issue number2
StatePublished - Feb 1 1999


  • Calibration
  • Force
  • Implant
  • Tendon
  • Transducer


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