Shear Strain and Motion of the Subsynovial Connective Tissue and Median Nerve During Single-Digit Motion

Yuichi Yoshii, Chunfeng Zhao, Jacqueline Henderson, Kristin D. Zhao, Kai Nan An, Peter C. Amadio

Research output: Contribution to journalArticle

18 Scopus citations


Purpose: The objective of this study was to measure the relative motion of the middle finger flexor digitorum superficialis (FDS) tendon, its adjacent subsynovial connective tissue (SSCT), and the median nerve during single-digit motion within the carpal tunnel in human cadaver specimens and to estimate the relative motions of these structures in different wrist positions. Methods: Using fluoroscopy during simulated single-digit flexion, we measured the relative motion of the middle finger FDS tendon, SSCT, and median nerve within the carpal tunnel in 12 human cadavers. Measurements were obtained for 3 wrist positions: neutral, 60° flexion, and 60° extension. After testing with an intact carpal tunnel was completed, the flexor retinaculum was cut with a scalpel, and the same testing procedure was repeated for each wrist position. The relative motions of the tendon, SSCT, and median nerve were compared using a shear index, defined as the ratio of the difference in motion along the direction of tendon excursion between 2 tissues divided by tendon excursion, expressed as a percentage. Results: Both tendon-SSCT and tendon-nerve shear index were significantly higher in the 60° of wrist flexion and extension positions than in the neutral position. After division of the flexor retinaculum, the shear index in the 60° wrist extension position remained significantly different from that of the neutral position. Conclusions: We have found that the relative motion between a tendon and SSCT in the carpal tunnel is maximal at extremes of wrist motion. These positions may predispose the SSCT to shear injury.

Original languageEnglish (US)
Pages (from-to)65-73
Number of pages9
JournalJournal of Hand Surgery
Issue number1
StatePublished - Jan 1 2009



  • Carpal tunnel
  • fluoroscopy
  • human cadaver
  • median nerve
  • subsynovial connective tissue (SSCT)

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

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