Dynamic MRI evaluation of lumbar spine- Manual therapy implications

Flexion and extension movements or positions have been advocated in the treatment of various forms of low back dysfunction due to the potential pain relieving effects attributed to displacements of the intervertebral disc (IVD). Kinetic MRI is a novel dynamic magnetic resonance imaging (MRI) system used to study lumbar disc herniations. Many times a static MRI may not reveal disc disorder yet functional MRI may reveal pathology.
Edmondston SJ (manual therapy, 2000) did MRI to evaluate the influence of sagittal plane positions on lumbar IVD height and nucleus displacement in a small asymptomatic population.T2-weighted sagittal plane images from L1 to S1 were obtained from 10 subjects (mean age: 30+/-5 years) positioned supine in lumbar flexion, followed by extension. Changes in disc height and localization of nucleus position (determined by peak MRI signal intensity) between the two positions were calculated. He found:
1. Despite the anterior displacement of the nucleus in extension observed in the pooled analysis, 30% of discs did not follow this trend. Nucleus degeneration was observed in at least one disc in nine subjects and in 26% of all discs examined.
2. Lumbar spine position was found to be associated with small measured changes in anterior disc height and nucleus position, however, this response was variable within and between individuals. The theoretical concept of a stereotypical effect of spinal position on the lumbar IVD is challenged by these initial data.
In another study Zou J et al’s (spine, 2008) tried to determine if adding flexion and extension MRI studies to the traditional neutral views would be beneficial in the diagnosis of lumbar disc herniations. They found a significant increase in the degree of lumbar disc herniation was found by examining flexion and extension views when compared with neutral views alone. Dynamic MRI views provide valuable added information, especially in situations where symptomatic radiculopathy is present without any abnormalities demonstrated on conventional MRI.
In the lieu of above said finding Edmondston’s recommendation sounds apt. His recommendation for the manual therapists is as follows: since the health of the disc is often unknown in clinical practice, manual therapy treatment for lumbar spine pain should be based on the symptomatic response to movement and position rather than biomechanical theory.

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