Variance in the measurement of sagittal lumbar spine range of motion among examiners, subjects, and instruments.

STUDY DESIGN: Repeated measurements were made of lumbar sagittal range of motion by 14 examiners using three different measurement instruments.

OBJECTIVES: To determine the reliability of lumbar range of motion measurements among examiners, subjects, and instruments, and to determine whether variance is due to subject inconsistency, examiner inconsistency, differences between examiners, or differences between instruments.

SUMMARY OF BACKGROUND DATA: Measurements of lumbar spine range of motion are widely used in research and clinical applications as well as in disability rating systems for patients with low back pain.

METHODS: Fourteen examiners measured the sagittal range of motion. Using three instruments, 18 healthy subjects were measured twice in a randomized sequence with blinded readings when performing full flexion, and partial flexion to a defined midpoint. None of the examiners routinely used the particular instruments in their practices.

RESULTS: The mean test-retest reliability was 4.9 degrees. The intraexaminer reliability did not differ significantly among the examiners. Furthermore, there was no systematic difference resulting from instruments or posture condition. However, there was a statistically significant variance among examiners--i.e., a poor interexaminer reliability.

CONCLUSION: The most likely explanation for these findings is the variability among examiners in locating bony landmarks. The results indicate that range of motion measurements must be interpreted with caution in clinical, research, and disability applications. Test administrator training may improve results, but this could not be determined from this study.