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Comparison of lumbar proprioception as measured in unrestrained standing in individuals with disc replacement, with low back pain, and without low back pain.

STUDY DESIGN
Cross-sectional laboratory study.


OBJECTIVE
To determine whether individuals with spinal pain and those who have undergone spinal surgery have difficulty discriminating small movement differences using a spinal proprioception test for active flexion movements.


BACKGROUND
Structures contributing to proprioception may be affected during disc replacement surgery. Postsurgical assessment of proprioceptive ability to make discriminations in the range used for maintaining upright postural stability is needed to inform postoperative rehabilitation.


METHODS
Proprioceptive sensitivity to differences between lumbar spine movements of 11 degrees, 13 degrees, 15 degrees, 17 degrees, and 19 degrees of forward flexion was measured in unrestrained standing, with vision of the target obscured. Individuals after disc replacement (n=16), with disc degeneration and discogenic back pain (n=19), and without back pain (n=18) performed 50 movement trials and stated the amount of movement performed for each trial (11 degrees, 13 degrees, 15 degrees, 17 degrees, or 19 degrees).


RESULTS
The pattern of discrimination scores between adjacent lumbar flexion movement pairs shown by the individuals in the discogenic back pain group differed significantly from the disc replacement and healthy control groups (P=.024), which were not significantly different from each other. Although mean discrimination scores averaged over all movement pairs did not differ significantly between the groups, participants with discogenic back pain discriminated between the 2 smallest lumbar flexion movements significantly better than those in the other 2 groups (P=.013).


CONCLUSION
The greater sensitivity of the individuals with disc pain to discriminate between the 2 smallest flexion movements was interpreted as a contrast effect arising from differences between the groups in usual upright posture, with disc replacement restoring the same pattern of posture as seen for healthy controls.