• Strong donor muscles (latissimus dorsi and teres major) on Active Movement Scale (AMS) for infant assessment

• Active shoulder abduction ≥ 60° on AMS

• Well-maintained passive range of motion (PROM) of the shoulder

• Impairment of bimanual overhead activities

• Good hand function on AMS

• Figure 1 demonstrates preoperative shoulder range of motion in a child with brachial plexus birth palsy in active abduction (Fig. 1A) and active external rotation in 90° of abduction (Fig. 1B). Figure 2 shows postoperative active abduction (Fig. 2A) and active external rotation in 90° of abduction (Fig. 2B) in the same child.

• If supination contracture is developing, biceps rerouting may be performed during the same surgery as ERTT.

• If wrist extension is weak, active finger extension is adequate, and a suitable donor muscle is available (brachioradialis or flexor carpi ulnaris), wrist extension transfer may be performed during the same surgery as ERTT.

• All ages: passive shoulder external rotation with scapula stabilized and arm at side and in 90° of shoulder abduction

• Infants: ultrasonography or MRI

• Under age 3 years: MRI

• Over age 3 years: anteroposterior and axillary radiographs or computed tomography

• The nerve and the posterior humeral circumflex artery are exposed in the quadrangular space when the latissimus dorsi and teres major are detached.

• In addition, the tendon transfer passes through the deltoid-triceps interval, and care should be taken to develop the opening in this interval proximal to where the axillary nerve enters the posterior deltoid.