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Microcomputed Tomography Characterization of Shoulder Osseous Deformity After Brachial Plexus Birth Palsy: A Rat Model Study
Zhongyu Li, MD, PhD1; Jonathan Barnwell, MD1; Josh Tan, MS1; L. Andrew Koman, MD1; Beth P. Smith, PhD1
1 Department of Orthopaedic Surgery, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157. E-mail address for Z. Li: zli@wfubmc.edu
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Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from the American Foundation for Surgery of the Hand. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

Investigation performed at the Department of Orthopaedic Surgery, Wake Forest University School of Medicine, Winston-Salem, North Carolina

Copyright © 2010 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2010 Nov 03;92(15):2583-2588. doi: 10.2106/JBJS.I.01660
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Shoulder deformities are common secondary sequelae associated with brachial plexus birth palsy. The aim of the present study was to characterize three-dimensional glenohumeral deformity associated with brachial plexus birth palsy with use of microcomputed tomography scanning in a recently developed animal model.


Brachial plexus birth palsy was produced by a right-sided neurotomy of the C5 and C6 nerve roots in seven five-day-old Sprague-Dawley rats. Microcomputed tomography scanning was performed when the rats were four months of age. Glenoid size, version, and inclination; humeral head size; and acromion-glenoid distance were measured. Normal shoulders of age-matched rats (n = 9) served as controls. Statistical analysis was performed with use of the unpaired two-tailed Student t test.


There were significant increases in glenoid retroversion (—7.6° ± 4.9° compared with 3.6° ± 2.1°; p = 0.038) and glenoid inclination (38.7° ± 7.3° compared with 11.2° ± 1.9°; p = 0.015) in the shoulders with simulated brachial plexus birth palsy in comparison with the normal, control shoulders. The glenohumeral joints were more medialized in the joints with simulated brachial plexus birth palsy as reflected by the acromion-glenoid distance measurement; however, the difference was not significant (3.20 ± 0.51 compared with 2.40 ± 0.18 mm; p = 0.12). Although the mean humeral head height and width measurements, on the average, were smaller in the brachial plexus birth palsy shoulders as compared with the normal, control shoulders, only the measurement of humeral head height was significantly different between the two groups (4.25 ± 2.02 compared with 4.97 ± 0.11 mm [p = 0.008] and 3.56 ± 0.27 compared with 4.19 ± 0.17 mm [p = 0.056], respectively).


In this animal model, rats with simulated brachial plexus birth palsy developed gross architectural joint distortion characterized by increased glenoid retroversion and inclination. In addition, humeral heads tended to be smaller four months after simulated brachial plexus birth palsy.

Clinical Relevance: 

Combined with the microcomputed tomography technique, this animal model may provide a useful means of studying the natural history of shoulder deformity associated with brachial plexus birth palsy.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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