Background & Aims
: Non-specific low back pain is defined as the pain below the costal margin and above the inferior gluteal fold without clear nociceptive causes and which cannot be explained by specific spinal and non-spinal (hip, pelvic organs, vascular structure, systemic disorders) pathophysiological mechanisms. Paraspinal muscles are responsible for the mobility as well as stability of the spine and are shown to be affected in chronic non-specific low back pain. The changes observed are fatty infiltration, fibrosis and decrease in cross sectional area of the paraspinal muscles. What is the strength of association between the changes in individual paraspinal muscles and low back pain is largely unknown. This study was planned on a subset of Indian population, wherein we correlated the MRI morphometry of the paraspinal muscles with the duration of low back pain.
Aim: to investigate the changes in paraspinal muscles in patients with non-specific low back pain and compare it with the normal subject
Methods
Patients in 20 to 60 years age group with a normal spinal curvature and a history of low back pain for at least 3 months were included in the study. All patients with evidence of spine deformity, infections, trauma, malignancies and metallic implants, were excluded from the study. The patients were evaluated by axial T2 weighted MRI . All measurements were done at L3-4 level. Multifidus, Erector spinae, Psoas and the Quadratus Lumborum muscles of both sides were assessed and their total cross-sectional area (TCAS), functional cross-sectional area (FCSA), FCSA/TCSA ratio, intramuscular fat infiltration (Kader classification) and muscle atrophy were noted. Age matched controls were patients who presented to MRI suite for problems unrelated to back pain. The threshold technique and manual tracing (of region of interest) technique were utilised to calculate the TCSA and FCSA.
Results
100 patients (51 males and 49 females) participated in the study. The mean age amongst cases was 39.42±11.58 and amongst controls was 36.16±9.68(p=0.548).. Maximum muscle atrophy and high grade of fatty infiltration was observed in multifidus followed by erector spinae in cases and correlated with the longer duration of back pain. There was a strong negative correlation between Multifidus FCAS and the duration of pain (spearman correlation coefficient of -0.8). The maximum fatty infiltration (grade 3) was seen in patients with maximum pain duration and the effect size was large (Kendall’s tau= 0.63).A moderate negative correlation between FCAS of Erector Spinae on the dominant side (rho = -0.35, p=0.013) as well as the non-dominant side (rho = -0.36, p=0.011) was observed. Quadratus lumborum muscle showed a weak correlation with the pain duration whereas the psoas muscle showed a moderate correlation.
Conclusions
There is a definite correlation between the functional cross-sectional area of paraspinal muscles and the duration of pain. FCSA correlated more with the duration of pain-the lesser the FCAS, the more is the duration of pain. The ration of FCAS/TCAS can be used to predict the level of disability in non-specific low back pain.
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Presenting Author
Nimisha Verma
Poster Authors
Topics
- Specific Pain Conditions/Pain in Specific Populations: Low Back Pain