Midlumbar lateral flexion stability measured in healthy volunteers by in vivo fluoroscopy.

STUDY DESIGN

Prospective fluoroscopic and electromyographic study of coronal plane lumbar spine motion in healthy male volunteers.

OBJECTIVES

Assess the intervertebral motion profiles in healthy volunteers for symmetry, regularity, and neutral zone laxity during passive recumbent lateral bending motion.

SUMMARY OF BACKGROUND DATA

Previous continuous in vivo motion studies of the lumbar spine have mainly been limited to active, weight-bearing, flexion-extension (sagittal plane) motion. No data are available for passive lateral bending or to indicate the motion profiles when muscle activity is minimized.

METHODS

Thirty asymptomatic male volunteers underwent video-fluoroscopy of their lumbar spines during passive, recumbent lumbar lateral bending through 80 degrees using a motor-driven motion table. Approximately 120 consecutive images of segments L2-L5 were captured, and the position of each vertebra was tracked throughout the sequence using automated frame-to-frame registration. Reference intervals for intervertebral motion parameters were calculated. Surface electromyography recordings of erector spinae were obtained in a similar group of volunteers using the same protocol without fluoroscopy to determine to what extent the motion was completely passive.

RESULTS

Correlations between intervertebral and lumbar motion were always positive in controls and asymmetry was less than 55% of intervertebral range. The upper reference interval for the slope of intervertebral rotation in the first 10 degrees of trunk motion did not exceed 0.46 for any level. Muscle electrical activity during the motion was very low. Examples from patient studies showed markedly different results.

CONCLUSION

These results suggest that reference limits from asymptomatic data for coronal plane passive recumbent intervertebral motion may be a useful resource for investigating the relationship between symptoms of chronic (nonspecific) low back pain and biomechanics and in the clinical assessment of patients and interventions that target the passive holding elements of the spine. Data pooling from multiple studies would be necessary to establish a complete database.