Dynamic Cervical Radiographs in Patients with Hirayama Disease: An Unneglectable Factor on the Choice of Surgery Options.

OBJECTIVE

To evaluate the cervical spine alignment and range of motion (ROM) of neck flexion in patients with Hirayama disease.

METHODS

Fifty male patients were included, with dynamic radiographs and magnetic resonance imaging (MRI) analyzed retrospectively. The Cobb angles for the entire cervical spine (C2-C7) and each level (C2/3-C6/7) were measured, and the neck flexion ROM was defined as the neutral Cobb angle minus the flexion Cobb angle. Paired t tests and Wilcoxon signed-rank tests were used to compare the Cobb angles and ROM between radiographs and MRI.

RESULTS

The neutral and flexion Cobb angles decreased from C2/3 to C5/6 but increased at C6/7 on radiographs and MRI. The neutral Cobb angle of C2-C7 from radiographs was significantly larger than that seen on MRI (5.27° vs. -3.26°; P < 0.0001). Neck flexion ROM seen with MRI tended to be lower than those of corresponding levels on radiographs. The ROM of C2-C7, C3/4, and C6/7 on radiographs was significantly larger than that seen with MRI (37.86° vs. 26.59°, P < 0.0001; 7.46° vs. 5.10°, P = 0.0071; and 10.45° vs. 7.03°, P = 0.0023, respectively). For the lower cervical levels, the largest and second largest ROM were seen in C5/6 and C6/7 on the radiographs but C5/6 and C4/5 on MRI.

CONCLUSIONS

The cervical spine alignment and neck flexion ROM in Hirayama disease differed between radiographs and MRI. Both imaging techniques should be examined comprehensively when planning an operation.