Measuring neck nerve strain: An experimental investigation

Tara L. Johnson, Vanessa LaPointe, Artin A. Shoukas, Edith D. Gurewitsch, Robert H. Allen

Research output: Chapter in Book/Report/Conference proceedingConference contribution


We sought to determine the effects of head rotation, lateral neck flexion, and traction force on brachial plexus (BP) nerve strain, specifically at C5-C6 (Erb's point), and C7, C8, and T1 roots in a multi-"filament" 3D model of the fetal BP. Using our constructed simulator and a tailored data acquisition system, strain readings were recorded and accurate to within <2%. Using our model and a position-sensing system, controlled loads and deformations were applied to a fetal head attached to a flexible spine. For each simulation, we measured BP strain at Erb's point, and C7, C8, and T1 roots. Increasing total traction force increases strain in the upper and middle nerves (Erb's point, C7, and C8). Lateral neck flexion produces the most strain (up to 25.4±6.6% in Erb's point with 4.5 kg (10 lbs) of traction), with concomitant head rotation magnifying strain levels by up to a factor of 1.7. Increasing head rotation and lateral neck flexion increases the strain in the lower nerve roots more than in the upper roots, in general, upper nerves undergo double the strain of lower nerves. Direct axial traction has the least effect, with 4.5 kg of traction producing a peak strain of 3.6±2.5% at Erb's point. BP strain can be reduced at Erb's point, C7, and C8 by maintaining neutral alignment between the head and trunk prior to applying traction, which should be minimized.

Original languageEnglish (US)
Title of host publicationProceedings of the 2nd Frontiers in Biomedical Devices Conference 2007
Number of pages2
StatePublished - Nov 23 2007
Externally publishedYes
Event2nd Frontiers in Biomedical Devices Conference 2007 - Irvine, CA, United States
Duration: Jun 7 2007Jun 8 2007

Publication series

NameProceedings of the 2nd Frontiers in Biomedical Devices Conference 2007


Other2nd Frontiers in Biomedical Devices Conference 2007
Country/TerritoryUnited States
CityIrvine, CA


  • Brachial plexus
  • Mechanical model
  • Nerve strain

ASJC Scopus subject areas

  • Biomedical Engineering


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