OBJECTIVETo identify the affect of chronic low back pain on multifidus muscle atrophy and fatty infiltration.

METHODSFrom March 2010 to August 2013, a retrospective study were carried out in the department of orthopedics of patients with low back pain. Finally 31 cases were selected to this study including 19 males and 12 females with an average age of 36.4 years ranging from 23 to 55 years. The main symptoms of these patients were repeated back pain. Duration was more than 1 year. X-ray, CT, MRI showed no obvious abnormalities. The changes of net cross-sectional area of multifidus and T2 signal ratio of the same patient were measured at different time by MRI. VAS and Oswestry disability scores were recorded in two MRI examination. Correlation between these change of multifidus net area and T2 signal ratio in two times measurement and duration of low back pain, VAS, Oswestry disability scores were analyzed to find the affection of low back pain on paraspinal multifidus muscle.

RESULTSThe net multifidus cross-sectional area in same case by the second follow-up MRI is significantly smaller than that of the first follow-up, T2 signal ratio at second was significantly higher than that of the first (P < 0.05). The net cross sectional area of multifidus muscles reduced rate were positively correlated with VAS scores, duration and of Oswestry disabilitry scores (P < 0.001). The rate of increase in T2 signal ratio was not correlated with VAS scores,duration and the Oswestry disability scores (P > 0.05).

CONCLUSIONChronic low back pain is one of the most important reasons of paraspinal multifidus muscle atrophy and fatty. The duration, VAS and Oswestry disability scores of chronic low back pain were positively correlated with the multifidus muscle atrophy.