Specific scapular kinematic patterns to differentiate two forms of dynamic scapular winging.

[thoracic outlet syndrome]

Dynamic scapular winging (DSW ) is a rare and misdiagnosed disorder causing considerable disability due to reduced scapular stability and abnormal motion . Two common causes are long thoracic nerve lesions resulting in serratus anterior muscle palsy and spinal accessory nerve lesions resulting in trapezius muscle palsy . The aim of this study was to analyse 3 D scapular kinematic patterns in patients with DSW due to long thoracic (LTNL ) or spinal accessory nerve lesions (SANL ).3 D scapular kinematics were assessed using a non invasive method involving an electromagnetic device during arm elevation in the frontal and sagittal planes in 9 patients (4 with SANL and 5 with LTNL ) with unilateral DSW confirmed by electrical evidence . Within subject affected-unaffected differences were measured and compared between pathological groups (Mann-Whitney ).Differences between affected and unaffected shoulders were significantly greater for scapular posterior tilt (at rest and 30 ° for sagittal arm elevation , at rest , 30 ° and 60 ° for frontal arm elevation ) in the LTNL compared to the SANL group . Differences between affected and unaffected shoulders were significantly greater for scapular protraction (at rest and 60 ° of sagittal arm elevation , at rest , 30 ° and 60 ° of frontal arm elevation ) and scapular lateral rotation at 60 ° for frontal arm elevation in the SANL compared to the LTNL group .These kinematic findings show two different scapular patterns that are specific to the neurological lesion . Moreover our kinematic data relate to specific clinical signs and the functional roles of the muscles involved .