Supracondylar fractures of the humerus: the role of dynamic factors in prevention of deformity.

In a retrospective survey of eighty-two children with supracondylar fractures of the humerus, forty were found to have sufficient clinical and roentgenographic data to classify the fractures as varus or valgus, and to determine the carrying angles at end result. The initial displacement (varus or valgus) of the distal fragment correlated with the final carrying angle, but the use of internal fixation, the adequacy of reduction achieved and the duration of traction or immobilization did not. The sixteen varus supracondylar fractures immobilized with the forearm in supination had a mean varus deformity of about 16 degrees, whereas the eight immobilized in pronation had a varus deformity of only 3 degrees. The findings in the few valgus fractures suggested that the valgus angulation was less at follow-up if they had been immobilized in supination. Dissection of eight cadaver limbs and electromyographic studies of one normal limb suggested that the position of the forearm affects the result by altering muscle tension.