Diaphragmatic contraction is controlled by phrenic nerve which consists of anterior rami of
3rd- 5th cervical nerve roots. Usually, It can't be evaluated from history taking and
physical examination. Thus the diaphragmatic elevation on chest radiograph is assumed to
identify the phrenic nerve dysfunction. Normally, the right diaphragm is higher than the left
side about 1.5 ± 0.9 centimeters or 0.5 ± 0.3 time of vertebral height. Although there are
several methods to determine the diaphragmatic elevation from previous studies, the accuracy,
reliability, intra and inter-observer variation are problem.
Neurotization is the effective procedure to restore upper extremity function in root avulsion
type. Phrenic nerve is one of the common donor nerves which used for this procedure. But
sometimes, concomitant injury of this nerve can occur. Therefore, the investigators
established "Diaphragmatic height index (DHI)" from chest radiograph to use as the diagnostic
test for phrenic nerve dysfunction.