FLEXION OR EXTENSION

Williams and others recommended that reducing the lumbar lordosis of patients with low back pain when standing, sitting and during recumbency is essential for the health of the spine. Their reasons were LBP is often caused by lumbar lordosis placing an excessive stress on the posterior bony and soft tissue structures of the lumbar spine On the other hand Cyriax and McKenzie recommended that maintenance of lordosis was important to the health of the spine. They suggested that maintaining or increased lordosis results in anterior displacement of the NP with a decrease in the pressure on the pain sensitive structures in the neural foramen.

Clinical studies have reported favorable outcomes using exercises and postures that increase or maintain lumbar lordosis. Although the flexed position is thought to increase the diameter of the neural foramina and thus reduce the mechanical stimulus on the pain sensitive structures that are located in these areas, McKenzie and Cyriax proposed that when the spine is flexed the NP becomes closer to the pain sensitive structures in and near the spinal canal. Based on this, cyriax and McKenzie recommended supine lying with the hips in the anatomically neutral position and the knees in extension, and a lumbar roll under the lower back.

Harrison et al., 1999 in a review of literature on Sitting Biomechanics

“In the 1990s, Adams and colleagues began to reverse their minority-held opinion about sitting flexed postures being desirable. In a 1995 review of lumbar spine mechanics, they stated that the only known loading condition to cause posterior disc prolapse involved prolonged forward bending (flexion) with compression and lateral bending. They also noted that stress concentrations in the posterior annulus caused by prolonged flexion might be a common cause of pain from the disc”

(Schnebel et al., 1988) used discography to study nuclear displacement in symptomatic with normal and abnormal discs in flexion and extension. Discograms with normal morphology showed significant change in position anteriorly with extension.
Williams, McKenzie, van Wijmen (1991) In a randomized study that excluded pathologies aggravated by lordotic positions ( spondylolisthesis and spinal stenosis ), It was demonstrated that 48% of subjects with pain extending below the knee experienced reduction and centralization of pain towards the spine when sitting in the lordosed posture. 24% of kyphotic group peripheralized compared to 6% of lordotic group with just 10 min of sitting with lumbar roll.
(Fennell et al., 1996) Position of nucleus in neutral, flexion, and extension using MRI on non-degenerate discs. Flexion of an intervertebral disc in a living person tends to be accompanied by posteriorly directed migration of the nucleus pulposus within the disc. Extension tends to be accompanied by an anteriorly directed migration.
Treatment for LBP should be based on symptomatic response to movement and positions was the conclusion after the MRI study on degenerated and non- degenerated discs by (Edmonston, et al., 2000). 26% of all discs demonstrated Grade II degeneration of the nucleus. . In 46% of discs with grade 2 nucleus degeneration extension induced anterior migration of nucleus. 38.4% of them induced posterior migration of nucleus with flexion. 15% did not show any effect with either movement. , it is difficult to anticipate a stereotypical response within the disc to changes in position, consistent with clinical theory (McKenzie 1981).
Sagittal migration of nucleus in 6 functional positions using MRI. (Alexander et al., 2007). To quantify sagittal migration of the lumbar nucleus pulposus in six functional positions of standing, upright, flexed and extended sitting, supine and prone extension.
A systemic review of studies on the conceptual model from 1978-2007 (Kolber, et al.,2009). Anterior migration in extension and posterior with flexion. Contradictory in degenerated and symptomatic, which supports McKenzie’s concept of looking towards the self reported symptomatic and mechanical responses in assessment and management, It is difficult to anticipate a stereotypical response within the disc to changes in position, consistent with clinical theory (McKenzie 1981)

It is so often that we read prescriptions with "No extension exercises" or "Advised flexion exercises". Patients advised to prolonged bed rest in supine position with pillows under the knee, although study after study has been suggesting the better effects of movement and exercise and the ill-effects of prolonged bed rest. Let us look at the study results of what this famous position offers to the average back pain patient.

Position of nucleus in two supine position using MRI in asymptomatics (Beattie et al 1994). Supine lying with the hips and knee in flexion has traditionally been advocated as the appropriate position off rest for individuals with LBP which was challenged by Cyriax and McKenzie. Distance of posterior margin of NP to posterior margin adjacent vertebral margin was greater in extended position introducing a roll under the low back than in supine position with pillow under the knee, in L3/4, L4/5, and L5/S1. There was no difference in anterior position. The NP of degenerated did not move in the same way as normal disc. Williams maintained that LBP is often caused by lumbar lordosis placing an excessive stress on the posterior bony and soft tissue structures of the lumbar spine. According to McKenzie and Cyriax, increased lordosis results in anterior displacement of the NP with a decrease in the pressure on the pain sensitive structures in the neural foramen. The above (Beattie et al 1994) study proves it all.

Would you still advice your patients to rest with pillows under knee to induce flexion in the spine?

As study after study has revealed to us, that it is difficult to anticipate a stereotypical response within the disc to changes in position, consistent with clinical theory, would it not be in the best interest of your patients quick recovery that exercises be based on symptomatic response to movement and positions.

Mechanical Diagnosis and Therapy (MDT) or famously called 'The McKenzie Concept" is a low technology assessment system which is well researched. Managment using McKenzie concept follows the diagnostic classification, based on symptomatic and mechanical response to movement, positions and postures. MDT is evidenced to be reliable between clinicians who are trained in it, to bring out responders and non-responders. In responders we would know how best to help your patient control their pain and prevent their recurrences, and when and how they would need our help to control their pain in the least number of sessions. We do not need any expensive investigations, nor gadgets to recognise non-responders to the system. Our structured assessement and clinical reasoning is all that is needed.

RCT

Reliability Studies in MDT or (McKenzie Concept) -

Prognostic Studies in MDT (McKenzie Concept)-

RCT (McKenzie Concept)-

Cost effectiveness (McKenzie Concept)- .

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