Correlation of Paraspinal Atrophy and Denervation in Back Pain and Spinal Stenosis Relative to Asymptomatic Controls

Objective To determine the relationship among spinal stenosis, back pain, paraspinal muscle denervation, and paraspinal muscle atrophy. Design A prospective masked, double-controlled study. Setting A university hospital and outpatient spine clinic. Participants Ten asymptomatic subjects, 10 subjects with mechanical low back pain, and 15 subjects with symptomatic spinal stenosis; age range, 55-80 years old. Interventions Magnetic resonance imaging measurements of minimum spinal canal diameter, paraspinal muscle cross-sectional area at the level of the L5-S1 disk, and quantified paraspinal electrodiagnostic testing (MiniPM) were performed by examiners blinded to each other's results and to the participants' clinical information. Main Outcome Measurements Paraspinal muscle cross-sectional area and MiniPM scores. Results A paraspinal cross-sectional area decreased significantly from asymptomatic subjects (3872 mm 2 ) to subjects with low back pain (3627 mm 2 ) and to subjects with spinal stenosis (2985 mm 2 ). In the stenosis group, there was a trend toward increased paraspinal denervation in the subjects with severe spinal stenosis, but this was not statistically significant. Conclusions Symptomatic spinal stenosis results in greater paraspinal muscle atrophy than low back pain alone. The extent of paraspinal atrophy was not significantly explained by the extent of denervation, thus, it may be reversible, and the role of paraspinal muscle rehabilitation in patients with spinal stenosis deserves further study.