Change in shoulder external rotation strength and motion after lower trapezius transfer to the infraspinatus in children with obstetric brachial plexus palsy.

Purpose: Quantifying changes in shoulder external rotation range of motion and strength after lower trapezius transfer in children with obstetric brachial plexus palsy (OBPP).

Methods: This prospective study included five children with sequelae of OBPP, with a mean age of 6.4 years (range: 4-12 years) who underwent lower trapezius tendon transfer to restore active external rotation (ER) of the shoulder. Pre-operatively and at a 12-month follow-up assessment, we analyzed the passive and active shoulder ER, the modified Mallet score, and the shoulder rotator muscles strength using an isokinetic device.

Results: Clinical parameters improved significantly after trapezius transfer pre-operative passive ER from -8° (range: -20-0°) to 37° (range: 15-50°) (p = 0.035), the modified Mallet score from 13 (range: 10-15) to 18 (range: 17-19) (p = 0.035). Strength testing revealed improved ER muscle strength in all five cases; the mean Peak Torque increased from 1.95 to 4.46 N·m, albeit non-significantly (p = 0.062). Two patients exhibited a winged scapula post-operatively.

Conclusion: Lower trapezius transfer seems encouraging to restore shoulder external rotation in OBPP children but with non-significant strength improvement.

Trial Registration: 18/07/31/5783, December 22, 2018.