The effect of short arm cast length on forearm rotation

To compare ranges of active forearm pronation and supination with subjects wearing short arm casts of different lengths.

Forty right-handed healthy volunteers (20 men and 20 women) with an average age of 39 years (range, 26-58 y) were recruited. A goniometer with a circular plate and a handle connected to the scale indicator was used to measure forearm pronation and supination without a cast and with 3 different lengths of short arm cast. All casts extended from just proximal to the volar and dorsal aspects of metacarpophalangeal joints, and continued to either 2.5 cm distal to elbow flexion crease or 5 cm distal to the elbow flexion crease, or to the proximal one-third position between the wrist flexion crease and the elbow flexion crease.

Compared with no immobilization, the longest of the 3 constructs reduced active forearm rotation by 62%, whereas the cast to 5 cm from the elbow flexion crease reduced rotation to 50%, and the cast to the proximal one third of the way between the wrist and elbow flexion crease reduced rotation by 32%. Active forearm rotation was significantly dependent on cast length, and reductions in active forearm rotation were positively correlated with cast length.

Limitation of active forearm rotation by a short arm cast is positively correlated with cast length.

When a short arm cast is used to limit wrist motion and forearm rotation, it is better to extend it proximally but not to impinge on the antecubital fossa, where skin breakdown may occur.