This study evaluated the prevalence of posterior shoulder subluxation or dislocation in infants with obstetrical brachial plexus palsy prior to the age of one. One hundred thirty-four consecutive infants with neonatal brachial plexus palsy were evaluated over a two-year period at the Texas Scottish Rite Hospital for Children in Dallas. Monthly examinations were performed. Patients identified with abnormal physical findings were then evaluated with an ultrasound. Eleven (8%) of the 134 infants had evidence of a posterior shoulder dislocation. The mean age at the time of diagnosis was 6 months (range, 3-10 months). The clinical signs associated with posterior dislocation included asymmetry of skin folds of the axilla or the proximal aspect of the arm, apparent shortening of the humerus, a palpable asymmetric fullness in the posterior region of the shoulder, a palpable click during shoulder manipulation, or a rapid loss of passive external rotation between monthly examinations. There was no correlation between the occurrence of dislocation and the type of initial neurologic deficit.
This study confirmed an earlier age of potential posterior subluxation or dislocation in patients with an obstetrical brachial plexus palsy that did not correlate with the level of recovery or neurologic dysfunction. Although this study did not examine all patients with an ultrasound to confirm that the clinical findings outlined above truly were specific to posterior subluxation or dislocation, there clearly was an association with the clinical and ultrasound findings. The authors report the advantages of ultrasound to be free of ionizing radiation without the need for sedation and allowing for dynamic assessment of reduction of the shoulder as well as the degree of instability. Ultrasound, however, is more user dependant with less ability for the reconstructive surgeon to evaluate the level of dysplasia and also has less ability to grade the level of dysplasia compared to MRI or CT. This article provides an excellent review of the clinical, radiographic and ultrasonographic findings associated with obstetrical brachial plexus palsy.
Journal of Bone and Joint Surgery