No difference in long-term trunk muscle strength, cross-sectional area, and density in patients with chronic low back pain 7 to 11 years after lumbar fusion versus cognitive intervention and exercises

Background contextReduced muscle strength and density observed at 1 year after lumbar fusion may deteriorate more in the long term.PurposeTo compare the long-term effect of lumbar fusion and cognitive intervention and exercises on muscle strength, cross-sectional area, density, and self-rated function in patients with chronic low back pain (CLBP) and disc degeneration.Study designRandomized controlled study with a follow-up examination at 8.5 years (range, 7–11 years).Patients and methodsPatients with CLBP and disc degeneration randomized to either instrumented posterolateral fusion of one or both of the two lower lumbar levels or a 3-week cognitive intervention and exercise program were included. Isokinetic muscle strength was measured by a Cybex 6000 (Cybex-Lumex, Inc., Ronkonkoma, NY, USA). All patients had previous experience with the test procedure. The back extension (E) flexion (F) muscles were tested, and the E/F ratios were calculated. Cross-sectional area and density of the back muscles were measured at the L3–L4 segment by computed tomography. Patients rated their function by the General Function Score.Outcome measuresTrunk muscle strength, cross-sectional area, density, and self-rated function.ResultsFifty-five patients (90%) were included at long-term follow-up. There were no significant differences in cross-sectional area, density, muscle strength, or self-rated function between the two groups. The cognitive intervention and exercise group increased trunk muscle extension significantly (p<.05), and both groups performed significantly better on trunk muscle flexion tests (p<.01) at long-term follow-up. On average, self-rated function improved by 56%, cross-sectional area was reduced by 8.5%, and muscle density was reduced by 27%.ConclusionAlthough this study did not assess the morphology of muscles likely damaged by surgery, trunk muscle strength and cross-sectional area above the surgical levels are not different between those who had lumbar fusion or cognitive intervention and exercises at 7- to 11-year follow-up.