Retrospective Analysis of Shoulder Subluxation Diagnosed via Ultrasound Screening in Infants with Brachial Plexus Injuries

Background and/or Objectives: Brachial plexus birth palsy (BPBP) frequently leads to secondary shoulder subluxation and glenohumeral dysplasia that can cause additional functional limitations. The current literature varies widely in reported prevalence of shoulder subluxation from 6-56% in infants with BPBP, in part owing to lack of standardized protocols for screening.

Design: Retrospective cohort study

Setting : Tertiary children’s hospital

Participants : 114 infants with birth brachial plexus injuries referred to a multidisciplinary brachial plexus clinic between 2011-2023 with persistent neurological deficits beyond neurapraxic injuries.

Interventions: Screening shoulder ultrasounds were performed at 3 months and 6 months of age unless they otherwise received early intervention (botox and casting). Shoulder subluxation was defined as alpha angle > 30 degrees as measured on ultrasound.

Main Outcome Measures: Percentage of patients with shoulder subluxation, Active Movement Score external rotation, passive shoulder range of motion in external rotation

Results: On initial screening at 3 months, 86% (98 patients) had shoulder subluxation. Fifty-nine percent (67 patients) had alpha angles > 40 degrees, which is the institutional indication for intervention. There was a statistically significant correlation between alpha angle and both Active Movement Scale score for external rotation (r= -.33, 95%CI= -.48, -.15) and passive range of motion in external rotation (PROM-ER) (r= -.49, 95%CI = -.61, -.33). Of the patients with normal PROM-ER, 79% had shoulder subluxation. Sixty-nine patients received ultrasound screening at 6 months, of which 74% had evidence of shoulder subluxation.

Conclusions: The prevalence of shoulder subluxation can be determined as early as 3 months of age and is much higher than previously reported in the literature. The majority of patients with subluxation have no clinical correlations on exam. Early ultrasound screening and subsequent treatment of musculoskeletal imbalance may be important to facilitate limb movement for eventual functional re-innervation.