Magnetic resonance imaging of lumbar trunk parameters in chronic low backache patients and healthy population: a comparative study.

PURPOSE: The aim of this study was to evaluate the lumbar trunk parameters by MRI and investigate their association with chronic low backache.

METHODS: Fifty patients (26 males and 24 females) with mean age 33.54 ± 8.33 years with a history of low back pain (LBP) of minimum 3 consecutive months constituted the study group (Group A). To match with the study group, 15 normal healthy volunteers (9 males and 6 females) with no history of back pain were selected (Group B). Both the groups were subjected to magnetic resonance imaging of lumbosacral spine and lumbar trunk parameters were calculated.

RESULTS: Trunk width, depth and skin angle were comparable at L3-L4, L4-L5 and L5-S1 disc levels; significant difference with regard to disc angle of L3-L4 (p = 0.005) and L4-L5 (p = 0.02) and cross-sectional area (CSA) of disc at L4-L5 level (p = 0.01) was observed between two groups. There was a tendency of smaller CSA of paraspinal and abdominal oblique muscles in Group A patients, but the measurements were not statistically different from Group B patients. Rectus abdominis muscles showed a unique pattern of larger CSA at L3-L4 and L4-L5 disc levels and smaller CSA at L5-S1 in LBP patients. Intervertebral disc degenerative changes on MRI were observed in 27 (54 %) patients in the Group A; and none of the Group B participants showed degenerative changes.

CONCLUSIONS: Tendency of smaller trunk musculature CSA may be a cause or a result of chronic LBP. A unique pattern of larger CSA at L3-L4 and L4-L5 disc levels and smaller CSA at L5-S1 of Rectus abdominis muscles is observed in LBP patients compared to healthy persons. Differences in disc angles and CSA of disc at L3-L4 and L4-L5 levels between the two groups signify that these may be the predisposing factors leading to LBP due to abnormal load/stress transmission and precipitating early degenerative changes in the disc.