Brachial Plexus Birth Palsy-Associated Shoulder Deformity: A Rat Model Study

Purpose: Although recovery occurs in the majority of cases of brachial plexus birth palsy (BPBP), long-term shoulder disability is relatively common. The aim of this study was to establish an animal model to study BPBP-associated shoulder deformities. Methods: A right-side C5, C6 root neurotomy was performed under the surgical microscope in 5-day-old Sprague-Dawley rats (N = 9). The contralateral side served as a control. The development of shoulder deformity and range of motion loss were followed longitudinally. Animals were killed 4 months after surgery. Both shoulders were harvested, decalcified, and transected in the axial plane for glenoid version measurement and shoulder histology. Results: All animals developed shoulder internal rotation contracture within 4 weeks after the C5, C6 neurotomy. The average shoulder external rotation loss was 52° ± 7, 59° ± 10, and 82° ± 11 in comparison with the control side 1, 2, and 4 months after neurotomy, respectively. Glenoid version changed from 2° ± 2 of retroversion (left side) to 8° ± 3 of anteversion. Five shoulders were subluxated clinically with a pseudoglenoid formation observed radiographically. Histologic study demonstrated marked glenoid and humeral head deformities. Conclusions: This neonatal rat model clearly demonstrated typical shoulder deformities similar to that resulting from Erb's palsy. This model can be useful in studying BPBP-associated shoulder deformities.