An MRI study on the relations between muscle atrophy, shoulder function and glenohumeral deformity in shoulders of children with obstetric brachial plexus injury

Table 1 Measurement of active shoulder function according to Mallet.

Functional parameter	Class 1	Class 2	Class 3	Class 4	Class 5
Abduction	None	<30°	30°–90°	>90°	Normal
External rotation	None	<0°	0°–20°	>20°	Normal
Hand to neck	None	Not possible	Difficult	Easy	Normal
Hand to back	None	Not possible	S1	Th12	Normal
Hand to mouth	None	Marked trumpet sign*	Partial trumpet sign*	<40° abduction	Normal

Normal function in every dimension is five points, absent function 1 point [10].
*Trumpet sign is abduction of the shoulder with simultaneous flexion of the elbow.