Scapulothoracic and glenohumeral contributions to motion in children with brachial plexus birth palsy.
BACKGROUND
Brachial plexus birth palsy occurs in 0.4 to 4.6 of every 1000 live births, with residual shoulder dysfunction in approximately one third of cases. Clinical measures, such as the Mallet classification, provide no insight into the scapulothoracic and glenohumeral contributions to tested global shoulder movements. This study describes the scapulothoracic and glenohumeral components of shoulder motion during the modified Mallet test.


METHODS
Twelve children with Erb's palsy (C5-6) and 8 children with extended Erb's palsy (C5-7) were recruited. The unaffected limbs of 6 subjects were also tested. Locations of markers placed on the thorax, humerus, and scapula were recorded in a neutral position and each of the modified Mallet positions. Scapulothoracic, glenohumeral, and humerothoracic helical displacements and acromion process linear displacements were compared between groups.


RESULTS
The brachial plexus birth palsy groups exhibited significantly smaller glenohumeral displacements in all modified Mallet positions and significantly larger scapulothoracic displacements in the global external rotation and hand to mouth positions. Discriminant function analysis using only humerothoracic variables correctly classified 76.9% of subjects. Discriminant function analysis incorporating scapulothoracic, glenohumeral, and acromion process displacement variables produced accuracy of 92.6%.


CONCLUSIONS
Children with brachial plexus birth palsy demonstrated decreased glenohumeral contributions to achieve every modified Mallet position and increased scapulothoracic contribution in two positions compared with the unaffected group. Different scapulothoracic and glenohumeral strategies were identified between groups. Finally, scapulothoracic and glenohumeral components of shoulder motion are more specific than humerothoracic measures to diagnostic classification.
Biomechanics and Movement Science Program, University of Delaware, Newark, DE, USA. Electronic address: sarusso@udel.edu.
Stephanie A
SA
Russo
Upper Extremity Center of Excellence, Shriners Hospital for Children, Philadelphia, PA, USA; Department of Orthopaedic Surgery, Temple University, Philadelphia, PA, USA.
Scott H
SH
Kozin
Upper Extremity Center of Excellence, Shriners Hospital for Children, Philadelphia, PA, USA; Department of Orthopaedic Surgery, Temple University, Philadelphia, PA, USA.
Dan A
DA
Zlotolow
Biomechanics and Movement Science Program, University of Delaware, Newark, DE, USA.
Kristen F
KF
Thomas
Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA.
Robert L
RL
Hulbert
Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA.
Jeffrey M
JM
Mattson
Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA.
K Michael
KM
Rowley
Department of Kinesiology and Applied Physiology, University of Delaware, Newark, DE, USA.
James G
JG
Richards
D000174:Acromion / Q000503:physiopathology; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D020516:Brachial Plexus Neuropathies / Q000151:congenital* / Q000503:physiopathology* / Q000601:surgery; D002648:Child; D016002:Discriminant Analysis; D005260:Female; D006801:Humans; D006811:Humerus / Q000503:physiopathology; D008297:Male; D011187:Posture; D016059:Range of Motion, Articular; D012540:Scapula / Q000503:physiopathology; D012785:Shoulder Joint / Q000503:physiopathology* / Q000601:surgery; D016896:Treatment Outcome
Erb’s palsy; Scapulothoracic glenohumeral motion; brachial plexus palsy