Degeneration of the extensor muscle group in a surgical low back and leg pain population

The spinal muscles have received great attention in low back pain (LBP) with suggestions of a de-conditioning syndrome. It is not known whether it is a long or short term consequence of LBP. This study explored the cross section area (CSA) and muscle quality of the spinal extensor group in LBP patients referred to a spinal clinic. MRI scans of 100 annoymised patients were retrospectively reviewed; sagittal and transverse (from levels L3-5) images were archived and analysed to determine CSA and levels of fat infiltration of the extensor muscle groups. Forty six patients had spinal stenosis (28 males, 18 females, mean age 66 ± 14.2 years) and 54 had a disc prolapse (28 males, 26 females, mean age 50 ± 12.9 years). CSA was significantly smaller in the stenotics at both L3/4 and L4/5. Patients presenting with leg pain and a disc herniation had a significantly smaller CSA (p < 0.01) at L3/4 and L4/5 levels. Fat infiltration was present in both groups but was significantly greater in the stenotic group (p < 0.01) and was present at a similar degree at all spinal levels. Multiple regression analysis confirmed that reduced CSA was linked to leg pain (p < 0.01) and age was linked with fat infiltration (p < 0.01). Future work should explore the extent of such changes in an age and sex matched control population with no current back pain or sciatica.