Clinical Outcome of Lower Trapezius Muscle Transfer in Birth Brachial Plexus Palsy.

Background: Birth brachial plexus palsy (BBPP) can severely impair shoulder function by restricting external rotation and abduction, often leading to posterior subluxation or dislocation. Progressive shoulder dysplasia, a secondary condition of BBPP, further exacerbates functional disability by limiting shoulder function. Several techniques have been developed to address these challenges, including microsurgery, muscle transfer, and bony procedures. Recent reports on lower trapezius muscle transfer to the infraspinatus footprint demonstrate promising results in restoring shoulder biomechanics in adults. In this study, we aimed to treat patients younger than 7 years with BBPP through lower trapezius muscle transfer without allograft support.

Patients and methods: Between 2014 and 2018, 15 patients with BBPP and impaired shoulder external rotation and/or abduction (mean age, 22 months; range: 10 to 41 months) underwent lower trapezius muscle transfer surgery at our institution. A glenoid osteotomy was performed in patients without concentric joints, followed by the transfer of the lower trapezius muscle to the footprint of the infraspinatus. Patients were followed for an average of 25 months (range: 14 to 46 months). Outcomes assessed included shoulder external rotation, shoulder abduction, hand-to-mouth, hand-to-back, hand-to-neck, and Mallet scores.

Results: Significant improvements were observed in hand-to-mouth, hand-to-neck, global shoulder abduction, global shoulder external rotation, and total Mallet scores (P < 0.01). A nonsignificant decrease in hand-to-back was noted (P > 0.05). Both shoulder external rotation and abduction increased significantly (P < 0.01). No complications were reported after the muscle transfer procedure.

Discussion: Lower trapezius muscle transfer to the infraspinatus footprint markedly improves shoulder external rotation and abduction in children younger than 7 years without adverse effects on daily activities. This procedure is an effective treatment option for patients who present outside the optimal window for nerve transfer.

Level of evidence: Level IV; Case Series; Treatment Study.