Effect of the Sup-ER orthosis on glenohumeral joint alignment in infants with brachial plexus birth injury under 3 months.

Abstract

Background: Infants with brachial plexus birth injury are at risk for posterior glenohumeral joint subluxation due to a complex interaction of impaired longitudinal muscle growth, contracture, and imbalanced forces at the shoulder. The Sup-ER orthosis was designed to position the infant's affected shoulder in external rotation and optimize joint congruency while nerve recovery occurs. Joint alignment in the orthosis has not been studied.

Purpose: To examine the immediate effect of the Sup-ER orthosis on glenohumeral joint alignment in infants with brachial plexus birth injury at the time of initial orthosis fitting.

Study design: Retrospective cross-sectional research study.

Methods: Glenohumeral joint alignment in and out of the Sup-ER orthosis was compared using ultrasound imaging. Alpha angles were recorded from medical records of infants treated with the Sup-ER orthosis between 5 and 10 weeks of age in one hospital-based brachial plexus program over an 11-year period. A reduced glenohumeral joint was defined by alpha angle ≤30 degrees.

Results: Twelve of 28 infants (43%) showed subluxation of the affected glenohumeral joint out of the Sup-ER orthosis, with alpha angles >30 degrees. No significant difference existed between the proportion of joints reduced in the Sup-ER orthosis compared to out of the orthosis (p = 0.56); OR = 1.16 (95%CI = 0.40-3.36). The median alpha angle in the Sup-ER orthosis was significantly lower than out of the orthosis (p = 0.004) with an effect size of 0.55.

Conclusions: A high proportion of infants treated with the Sup-ER orthosis showed glenohumeral joint subluxation at the time of orthosis fitting, despite the young age. The Sup-ER orthosis was not effective in fully reducing the joints in these infants, despite measurable improvements in joint position. Future research is needed to determine which attributes of the Sup-ER orthosis or characteristics of the infant shoulder contribute to orthosis effectiveness.