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Shoulder posture and median nerve sliding.

Julius A, Lees R, Dilley A, Lynn B - BMC Musculoskelet Disord (2004)

Bottom Line: Neither moving the head forward or trunk flexion caused significant movement of the median nerve.There was a 60% reduction in nerve movement in the arm during contralateral neck side flexion when the shoulder was protracted compared to scapulothoracic neutral.However, shoulder protraction may place the median nerve at risk of injury, since nerve movement is reduced through the shoulder region when the shoulder is protracted and other joints are moved.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology, University College London, UK. AJulius@hhnt.org

ABSTRACT

Background: Patients with upper limb pain often have a slumped sitting position and poor shoulder posture. Pain could be due to poor posture causing mechanical changes (stretch; local pressure) that in turn affect the function of major limb nerves (e.g. median nerve). This study examines (1) whether the individual components of slumped sitting (forward head position, trunk flexion and shoulder protraction) cause median nerve stretch and (2) whether shoulder protraction restricts normal nerve movements.

Methods: Longitudinal nerve movement was measured using frame-by-frame cross-correlation analysis from high frequency ultrasound images during individual components of slumped sitting. The effects of protraction on nerve movement through the shoulder region were investigated by examining nerve movement in the arm in response to contralateral neck side flexion.

Results: Neither moving the head forward or trunk flexion caused significant movement of the median nerve. In contrast, 4.3 mm of movement, adding 0.7% strain, occurred in the forearm during shoulder protraction. A delay in movement at the start of protraction and straightening of the nerve trunk provided evidence of unloading with the shoulder flexed and elbow extended and the scapulothoracic joint in neutral. There was a 60% reduction in nerve movement in the arm during contralateral neck side flexion when the shoulder was protracted compared to scapulothoracic neutral.

Conclusion: Slumped sitting is unlikely to increase nerve strain sufficient to cause changes to nerve function. However, shoulder protraction may place the median nerve at risk of injury, since nerve movement is reduced through the shoulder region when the shoulder is protracted and other joints are moved. Both altered nerve dynamics in response to moving other joints and local changes to blood supply may adversely affect nerve function and increase the risk of developing upper quadrant pain.

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Individual nerve excursion values at sites in the upper arm and forearm for thirteen subjects produced by protraction. Each point is the average of three individual trials. Distance along the arm has been expressed as percentage of total distance from C6 spinous process to the tip of the index finger. A regression line has been fitted to the data.
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Figure 2: Individual nerve excursion values at sites in the upper arm and forearm for thirteen subjects produced by protraction. Each point is the average of three individual trials. Distance along the arm has been expressed as percentage of total distance from C6 spinous process to the tip of the index finger. A regression line has been fitted to the data.

Mentions: In 13 subjects the median nerve moved in a proximal direction during shoulder protraction with more movement at proximal locations (mean in forearm = 3.5 mm (SEM, 0.3), mean in upper arm = 5.9 mm (SEM, 0.6)) (figure 2 [see additional file 1 for ultrasound sequence of median nerve sliding in the forearm]). The mean extent of scapular anterior translation was 38.3 mm (SD, 13). The additional strain on the median nerve was 0.7% (SEM, 0.3), given by the slope of the regression of nerve movement against distance along the arm (Figure 2).


Shoulder posture and median nerve sliding.

Julius A, Lees R, Dilley A, Lynn B - BMC Musculoskelet Disord (2004)

Individual nerve excursion values at sites in the upper arm and forearm for thirteen subjects produced by protraction. Each point is the average of three individual trials. Distance along the arm has been expressed as percentage of total distance from C6 spinous process to the tip of the index finger. A regression line has been fitted to the data.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC503391&req=5

Figure 2: Individual nerve excursion values at sites in the upper arm and forearm for thirteen subjects produced by protraction. Each point is the average of three individual trials. Distance along the arm has been expressed as percentage of total distance from C6 spinous process to the tip of the index finger. A regression line has been fitted to the data.
Mentions: In 13 subjects the median nerve moved in a proximal direction during shoulder protraction with more movement at proximal locations (mean in forearm = 3.5 mm (SEM, 0.3), mean in upper arm = 5.9 mm (SEM, 0.6)) (figure 2 [see additional file 1 for ultrasound sequence of median nerve sliding in the forearm]). The mean extent of scapular anterior translation was 38.3 mm (SD, 13). The additional strain on the median nerve was 0.7% (SEM, 0.3), given by the slope of the regression of nerve movement against distance along the arm (Figure 2).

Bottom Line: Neither moving the head forward or trunk flexion caused significant movement of the median nerve.There was a 60% reduction in nerve movement in the arm during contralateral neck side flexion when the shoulder was protracted compared to scapulothoracic neutral.However, shoulder protraction may place the median nerve at risk of injury, since nerve movement is reduced through the shoulder region when the shoulder is protracted and other joints are moved.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology, University College London, UK. AJulius@hhnt.org

ABSTRACT

Background: Patients with upper limb pain often have a slumped sitting position and poor shoulder posture. Pain could be due to poor posture causing mechanical changes (stretch; local pressure) that in turn affect the function of major limb nerves (e.g. median nerve). This study examines (1) whether the individual components of slumped sitting (forward head position, trunk flexion and shoulder protraction) cause median nerve stretch and (2) whether shoulder protraction restricts normal nerve movements.

Methods: Longitudinal nerve movement was measured using frame-by-frame cross-correlation analysis from high frequency ultrasound images during individual components of slumped sitting. The effects of protraction on nerve movement through the shoulder region were investigated by examining nerve movement in the arm in response to contralateral neck side flexion.

Results: Neither moving the head forward or trunk flexion caused significant movement of the median nerve. In contrast, 4.3 mm of movement, adding 0.7% strain, occurred in the forearm during shoulder protraction. A delay in movement at the start of protraction and straightening of the nerve trunk provided evidence of unloading with the shoulder flexed and elbow extended and the scapulothoracic joint in neutral. There was a 60% reduction in nerve movement in the arm during contralateral neck side flexion when the shoulder was protracted compared to scapulothoracic neutral.

Conclusion: Slumped sitting is unlikely to increase nerve strain sufficient to cause changes to nerve function. However, shoulder protraction may place the median nerve at risk of injury, since nerve movement is reduced through the shoulder region when the shoulder is protracted and other joints are moved. Both altered nerve dynamics in response to moving other joints and local changes to blood supply may adversely affect nerve function and increase the risk of developing upper quadrant pain.

Show MeSH
Related in: MedlinePlus