Effect of lumbar spinal fusion surgery on the association of self-report measures with objective measures of physical function.

Background: Self-report measures are used to evaluate surgery outcome but are not necessarily indicative of actual disabilities.

Research Question: The aim of the present study was to determine the association between self-report assessments of quality of life and objective measures of function in patients with symptomatic lumbar degenerative disease. Additionally, we evaluated the effect of lumbar spinal fusion surgery on this relationship.

Methods: Before and 6 month after surgery 26 patients completed self-report questionnaires and assessments of 3D gait analysis and trunk range of motion (ROM) during standing.

Results: Before surgery, questionnaires were not correlated with any of the gait parameters and with only 2 trunk ROM parameters. Six month after surgery, the questionnaires showed 12 significant correlations with gait parameters and 19 with trunk ROM parameters. A better Oswestry Disability Index (ODI) (r = 0.464, p = .026), EQ-5D (r = -0.440, p = .036), and EQ VAS (r = -0.472, p = .023) score were correlated with a reduced anterior thorax tilt during walking. Maximum forward flexion of the trunk during standing was correlated with a better EQ-5D (r = 0.684, p = .001) and ODI (r = -0.560, p = .008) score as well as with reduced pain scores.

Significance: The lack of association between self-reported questionnaires and objective measures of function before surgery was likely due to psychological distress, correlating with emotional and cognitive function rather than true functional capacities. The influence of these psychological factors might be reduced after surgery due to a reduction of low back pain. To obtain an accurate assessment of impairment, there is a need to evaluate function by measuring objective physiologic parameters that are unsusceptible to voluntary or affective influences.