A Descriptive Study Investigating the Feasibility and Selectivity of Current Perception Threshold in the Objective Assessment of Post-operative Sub-acute Knee Pain

Abstract

[Purpose] The aim of this study was to investigate the feasibility of using the current perception threshold (CPT), in a comparison with the visual analog scale (VAS), to assess its selectivity in assessing the excitability of Aβ, Aδ and C fibers in subjects with sub-acute post-operative pain who were being treated with conventional transcutaneous electrical nerve stimulation (TENS). [Subjects and Methods] A total of 17 subjects (mean age of 29.2 ±10.8 years) participated in this study. For all subjects, the study commenced on the fifth post-operative day and continued for the next five consecutive days following a descriptive time-series design. Both CPT and VAS were measured for all subjects on all five days following 15 minutes rest with the TENS output intensity set at zero on the baseline days (Days 1, 3, 5), and after 15 minutes TENS stimulation on the intervention days (Days 2 and 4). [Results] The results demonstrate that CPT was able to selectively assess the excitability of the Aβ and Aδ fibers. However, the selectivity of CPT in assessing the C fibers could not be verified in this study. [Conclusion] The various limitations of the time series design used in this study suggest the need to verify some of these results in a different experimental design in future studies.