Background: Glenoid dysplasia and posterior shoulder subluxation
with resultant shoulder stiffness is a well-recognized complication in infants
with neonatal brachial plexus palsy. It is generally considered to be the
result of a slowly progressive glenohumeral deformation secondary to muscle
imbalance, physeal trauma, or both. Recent publications about infantile
posterior shoulder dislocation have suggested that the onset of dysplasia
occurs at an earlier age than has been previously recognized. The prevalence
of early dislocation in infants with this disorder has not been previously
reported, to our knowledge.
Methods: We studied 134 consecutive infants with neonatal brachial
plexus palsy who were seen at our institution over a period of two years. All
infants were examined at monthly intervals to assess neurological recovery and
the status of the upper extremity until recovery occurred or a treatment plan
was established. The type of brachial plexus involvement was classified.
Specific clinical signs associated with subluxation and dislocation were
recorded. These included asymmetry of skin folds of the axilla or the proximal
aspect of the arm, apparent shortening of the humeral segment, a palpable
asymmetric fullness in the posterior region of the shoulder, or a palpable
click during shoulder manipulation. The infants who were identified as having
these clinical signs were evaluated with ultrasonographic imaging studies.
Results: Eleven (8%) of the 134 infants had a posterior shoulder
dislocation. The mean age at the time of diagnosis was six months (range,
three to ten months). There was no correlation between the occurrence of
dislocation and the type of initial neurological deficit. A rapid loss of
passive external rotation between monthly examinations indicated a posterior
Conclusions: Posterior shoulder dislocation can occur earlier
(before the age of one year) and more rapidly in infants with neonatal
brachial plexus palsy than has been appreciated previously. As with
developmental dysplasia of the hip, a high index of suspicion, recognition of
clinical signs, and the use of ultrasonography will allow the diagnosis to be
established. Following early diagnosis, attention should be focused on
improving the stability and congruency of the shoulder joint.
Level of Evidence: Prognostic study, Level I-1
(prospective study). See Instructions to Authors for a complete description of
levels of evidence.