Microcomputed tomography characterization of shoulder osseous deformity after brachial plexus birth palsy: a rat model study.
BACKGROUND
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.


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
Department of Orthopaedic Surgery, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA. zli@wfubmc.edu
Zhongyu
Z
Li
Jonathan
J
Barnwell
Josh
J
Tan
L Andrew
LA
Koman
Beth P
BP
Smith
D000818:Animals; D000831:Animals, Newborn; D001720:Birth Injuries / Q000000981:diagnostic imaging* / Q000503:physiopathology; D020516:Brachial Plexus Neuropathies / Q000000981:diagnostic imaging* / Q000503:physiopathology; D004195:Disease Models, Animal; D016916:Joint Deformities, Acquired / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000000981:diagnostic imaging*; D055114:X-Ray Microtomography