Brachial plexus birth palsy-associated shoulder deformity: a rat model study.

Abstract

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. 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. All animals developed shoulder internal rotation contracture within 4 weeks after the C5, C6 neurotomy. The average shoulder external rotation loss was 52 degrees +/- 7, 59 degrees +/- 10, and 82 degrees +/- 11 in comparison with the control side 1, 2, and 4 months after neurotomy, respectively. Glenoid version changed from 2 degrees +/- 2 of retroversion (left side) to 8 degrees +/- 3 of anteversion. Five shoulders were subluxated clinically with a pseudoglenoid formation observed radiographically. Histologic study demonstrated marked glenoid and humeral head deformities. 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.