The shift of segmental contribution ratio in patients with herniated disc during cervical lateral bending.

BACKGROUND: Abnormal intervertebral movements of spine have been reported to be associated with trauma and pathological conditions. The importance of objective spinal motion imaging assessment in the frontal plane was frequently underestimated. The clinical evaluation of the segmental motion contribution could be useful for detecting the motion pattern of individual vertebrae. Therefore the purpose of this study was to investigate the shift of segmental contribution ratio in patients with herniated disc during cervical lateral bending to provide additional insights to cervical biomechanics. METHODS: A total of 92 subjects (46 healthy adult subjects and 46 disc-herniated patients) were enrolled in this case-control study. The motion images during cervical lateral bending movements were digitized using a precise image protocol to analyze the intervertebral motion and contribution. RESULTS: Our results showed that the intervertebral angulation during cervical lateral bending for the C2/3 to C6/7 segments were 7.66°±2.37°, 8.37°±2.11°, 8.91°±3.22°, 7.19°±2.29°, 6.31°±2.11°, respectively for the healthy subjects. For the patients with herniated disc, the intervertebral angulation for the C2/3 to C6/7 segments were 6.87°±1.67°, 7.83°±1.79°, 7.73°±2.71°, 5.13°±2.05°, 4.80°±1.93°, respectively. There were significant angulation and translational differences between healthy subjects and the patients with herniated disc in the C5/6 and C6/7 segments (P=0.001-0.029). The segmental contributions of the individual vertebral segments were further analyzed. There was a significant increase in segmental contribution ratio of C3/4 (P=0.048), while a significant decrease in contribution ratio of C5/6 (P=0.037) was observed in the patients with herniated disc. Our results indicated that the segmental contribution shifted toward the middle cervical spine in the patients with herniated disc. CONCLUSIONS: The segmental contributions of cervical spine during lateral bending movement were first described based on the validated radiographic protocol. The detection of the shift of segmental contribution ratio could be helpful for the diagnosis the motion abnormality resulted from the disc or, facet pathologies, and arthritic changes of cervical spine.

Segmental percentage contributions of cervical spine during different motion ranges of flexion and extension.

STUDY DESIGN: A blind, repeated-measure design was employed in the study. OBJECTIVE: To quantitatively measure the percentage contribution of segmental angular motion during different motion ranges of cervical flexion-extension for clinical applications and better understanding of cervical biomechanics. SUMMARY OF BACKGROUND DATA: Restriction of cervical motion is a major symptom in patients suffering from neck injuries or pathologies. Although segmental angular motion alternation is a criterion for the detection of neck related impairments, the percentage contribution throughout cervical movements is not well understood. METHODS: A total of 384 image sequences during cervical flexion-extension obtained from 48 healthy adult subjects were analyzed with a precise image protocol using dynamic videofluoroscopic techniques. RESULTS: The middle cervical spines demonstrated significantly greater angular percentage contributions at C3/4 (29.89%) and C4/5 (37.14%) angles during the initial 1/3 flexion movement; whereas the lower cervical spines revealed statistically greater angular contributions (C5/6: 22.57% to 29.45%; C6/7: 28.80% to 37.42%) from the middle to final 1/3 ranges of flexion movement (P<0.001). With regard to cervical extension motion, the majority of segmental percentage contributions statistically shifted initially from C5/6 level (30.21%) to C4/5 (24.96%) and C5/6 (26.12%) levels, and finally to the C3/4 (27.55%) and C4/5 (29.77%) segments (P<0.001). CONCLUSIONS: The segmental percentage contributions in this study might imply that the cervical flexion movement initially relied more on the middle cervical segments and later on the lower ones, whereas a motion pattern trend from lower to middle segments was observed during cervical extension.

Comparison of the intervertebral disc spaces between axial and anterior lean cervical traction.

The insufficient investigations on the changes of spinal structures during traction prevent further exploring the possible therapeutic mechanism of cervical traction. A blind randomized crossover-design study was conducted to quantitatively compare the intervertebral disc spaces between axial and anterior lean cervical traction in sitting position. A total of 96 radiographic images from the baseline measurements, axial and anterior lean tractions in 32 asymptomatic subjects were digitized for further analysis. The intra- and inter-examiner reliabilities for measuring the intervertebral disc spaces were in good ranges (ICCs = 0.928-0.942). With the application of anterior lean traction, the statistical increases were detected both in anterior and in posterior disc spaces compared to the baseline (0.29 mm and 0.24 mm; both P < 0.01) and axial traction (0.16 mm and 0.35 mm; both P < 0.01). The greater intervertebral disc spaces obtained during anterior lean traction might be associated with the more even distribution of traction forces over the anterior and posterior neck structures. The neck extension moment through mandible that generally occurred in the axial traction could be counteracted by the downward force of head weight during anterior lean traction. This study quantitatively demonstrated that anterior lean traction in sitting position provided more intervertebral disc space enlargements in both anterior and posterior aspects than axial traction did. These findings may serve as a therapeutic reference when cervical traction is suggested.

The quantitative measurements of the intervertebral angulation and translation during cervical flexion and extension.

The insufficient exploration of intervertebral translation during flexion and extension prevents the further understanding of the cervical biomechanics and treating the cervical related dysfunction. The objective of this study was to quantitatively measure the continuous intervertebral translation of healthy cervical spine during flexion and extension by videofluoroscopic technique. A total of 1,120 image sequences were analyzed for 56 healthy adult subjects by a precise image protocol during cervical flexion and extension. O: ur results showed there were no statistical angular differences among five spinal levels in either flexion or extension, except for the comparison between C2/3 (13.5 degrees) and C4/5 (22.6 degrees) angles. During cervical flexion, the smallest anterior translations were 0.7 mm at C2/3 level, followed by 0.9 mm at C6/7, 1.0 mm at C3/4, 1.1 mm at C5/6, and the largest 1.2 mm at C4/5 levels. The significantly greater translations were measured in the posterior direction at C3/4 (1.1 mm, P = 0.037), C4/5 (1.3 mm, P = 0.039), and C5/6 (1.2 mm, P = 0.005) levels than in the anterior one. The relatively fluctuant and small average posterior translation fashion at C6/7 level (0.4 mm) possibly originated from the variations in the direction of translation during cervical extension among subjects. Normalization with respect to the widths of individual vertebrae showed the total translation percentages relative to the adjacent vertebrae were 9.5, 13.7, 16.6, 15.0, and 8.6% for C2/3 to C6/7 levels, respectively, and appeared to be within the clinical-accepted ranges of translation in cervical spine. The intervertebral translations of cervical spine during flexion and extension movements were first described in quality and quantity based on the validated radiographic protocol. This analysis of the continuous intervertebral translations may be further employed to diagnose translation abnormalities like hypomobility or hypermobility and to monitor the treatment effect on cervical spines.