Development of a Neonatal Rat Model for Brachial Plexus Birth Injury.

Studying brachial plexus birth injuries (BPBI) has been challenging due to heterogeneous clinical presentations and limited reliable animal models. To that end, we have developed a surgical protocol that reproducibly induces a pan-plexal neonatal brachial plexus injury in 5-day-old Sprague-Dawley rat pups. In this article, step-by-step instructions are provided for approaching the brachial plexus in a rat pup. The technique was performed on 15 Sprague Dawley rat pups. Using a dorsal approach under operative microscopy, a 5 mm dorsal incision was made starting at the base of the skull towards the level of C7-T1 vertebral transition. Blunt dissection is carried down to the trapezius muscle, followed by dissection through the underlying rhomboid and levator scapulae muscles. After identifying anatomical landmarks such as the spine and the scapula, the superior angle of the scapula was gently retracted to visualize the brachial plexus. The brachial plexus was localized and cauterized, evidenced by observable twitches in the upper extremity. To prevent nerve regeneration, a small block of an absorbable gelatin sponge was placed between the proximal and distal ends of the injured nerves. This procedure was successfully performed on all 15 rat pups with 87% survival. Postoperative and at sacrifice, all surviving rats demonstrated complete pan-plexal injuries, validating this model as effective and reproducible for research in brachial plexus birth injuries.