Background: The prevalence and risk factors for recurrent
instability and functional impairment following a primary glenohumeral
dislocation remain poorly defined in younger patients. We performed a
prospective cohort study to evaluate these outcomes. We also aimed to produce
guidelines for the design of future clinical trials, assessing the efficacy of
interventions designed to improve the outcome after a primary dislocation.
Methods: We performed a prospective cohort study of 252 patients
ranging from fifteen to thirty-five years old who sustained an anterior
glenohumeral dislocation and were treated with sling immobilization, followed
by a physical therapy program. Patients received regular clinical follow-up to
assess whether recurrent instability had developed. Functional assessments
were made and were compared for two subgroups: those who had not had
instability develop and those who had received operative stabilization to
treat recurrent instability.
Results: On survival analysis, instability developed in 55.7% of the
shoulders within the first two years after the primary dislocation and
increased to 66.8% by the fifth year. The younger male patients were most at
risk of instability, and 86.7% of all of the patients known to have recurrent
instability had this complication develop within the first two years. A small
but measurable degree of functional impairment was present at two years after
the initial dislocation in most patients. Sample-size calculations revealed
that a relatively small number of patients with a primary dislocation would be
required in future clinical trials examining the effects of interventions
designed to reduce the prevalence of recurrent instability and improve the
Conclusions: Recurrent instability and deficits of shoulder function
are common after primary nonoperative treatment of an anterior shoulder
dislocation. There is substantial variation in the risk of instability, with
younger males having the highest risk and females having a much lower risk.
Future clinical trials to evaluate primary interventions should evaluate the
prevalence of recurrent instability and functional deficits, with use of an
assessment tool specifically for shoulder instability, during the first two
years after the initial dislocation.
Level of Evidence: Prognostic Level I. See Instructions
to Authors for a complete description of levels of evidence.