Feature - Sciatica: is Extension the Right Choice?

Introduction and Definitions

For quite some time now, spinal extension has been used ubiquitously for the treatment of sciatica. Whilst it may help some people, there are concerns about whether this movement should be used for patients with lumbar radiculopathy.

The fact that 'sciatica', 'radicular pain' and 'radiculo- pathy' mean different things has important clinical implications when it comes to the choice of which movement to use for these different conditions.

Sciatica - pain in the distribution of the sciatic nerve. This may come from a nerve root (therefore is also classified as radicular pain). Radicular pain may have many possible causes, including disc bulge, protrusion or herniation or medical pathologies such as arachoiditis or arachnoidoma.

Sciatica may also originate from the sciatic nerve itself (therefore is not radicular pain). Such peripheral nerve causes could be a piriformis syndrome, adhesion around the nerve in the thigh after trauma or even something as serious as myosarcoma in the hamstring muscles.

Radicular pain - pain in the distribution of a nerve root. This most commonly involves L4-S1 nerve roots which feed the sciatic nerve. In terms of definitions, dysfunction or pathology in the nerve root can also produce sciatica. This relates to the next topic below, the dynatome.

What is a dynatome? - a dynatome is the area of symptoms (eg. pain and pins and needles) produced from a nerve root. This is different from a dermatome or myotome because it is a function of 'referred pain mechanisms' and is not a result of reduced function in the nerve root such as that which can occur in radiculopathy. Note that these dynatomes are distributed differently from dermatomes (Slipman et al 1998). Due to these differences, the dynatome should NOT be used in isolation to determine which nerve root is involved. A neurologicial evaluation is essential in determining this.

Radiculopathy - pathology of the nerve root. This is characterised by reduced nerve root conduction which in turn manifests itself in the patient as impairment of neurological function in relation to a specific nerve root. Thus, knowledge of the dermatomes and myotomes are key elements of making this diagnosis. The diagnosis of radiculopathy is ultimately made with a detailed neurological evaluation, radiological investigations and/or during observation at surgery. Radiculopathy is essentially a diagnosis of pathology in the nerve root expressed as neurological impairment related to that particular nerve root.

What Does Lumbar Extension Do?

Increased Epidural and Intraforaminal Pressure

Fig 1: Lumbar intraforaminal pressureUsing direct pressure measurements in the epidural space in patients with spinal stenosis, Takahashi et al (1995) showed increases in pressure during standing, walking and particularly the double stance phase of walking in which repeated lumbar extension occurs.

Morishita et al (2006) showed that, in two groups of patients, those with spinal stenosis and those with disc herniation without stenosis or significant degenerative changes, extension produced a significant increase in the intraforaminal pressure (Figure 1).

Figure 1.) Lumbar intraforaminal pressure in three positions; from left to right, lumbar flexion, neutral and extension. From neutral, flexion produced a reduction in pressure whilst there was a step step-wise increase in pressure toward extension (From Morishita et al 2006, buy paper).

Mechanism of Increased Pressure in the Intervertebral Foramen

The mechanism by which lumbar extension increases pressure in the canal and intervertebral foramen (IVF) is closing of the posterior vertebral area at the back of the discs, bulging in a posterior direction by the posterior annulus and a pincer action between the facet joint capsule, disc and ligamentum flavum (as in Figure 2).

Fig 2: Effects of lumbar extensionIt is quite clear that, compared to flexion, extension of the lumbar spine increases epidural and intraforaminal pressure and, in the presence of raised intraforaminal pressure, such as that caused by disc herniation, this movement has the potential to produce adverse effects in the lumbar nerve root.

Figure 2.) Effects of lumbar extension. The movement shortens the spine, compressing the posterior aspect of the intervertebral disc and facet joint, compresses and causes forward buckling of the ligamentum flavum into the canal, reduces the vertical height the intervertebral foramen and produces a pincer action between the facet capsule and posterior annulus (From Shacklock 2005, Clinical Neurodynamics, Elsevier, Oxford).

Reduced Lumbar Nerve Root Conduction

An important study in relation to whether lumbar extension is appropriate for patients with lumbar radiculopathy is that published by Morishita et al (2006).

At surgery, they assessed the conduction (CMAPs - combined muscle action potentials) of lumbar nerve roots in lumbar flexion, neutral and extension in two groups of patients and those with spinal stenosis those with lumbar disc herniation without significant degenerative changes.

Fig 3: Amplitude of CMAPsIn this study, they showed that lumbar extension produced a reduction in nerve root conduction (reduced amplitude of CMAPs) in patients with spinal stenosis. This was due to a significant increase in pressure in the IVF, measured at surgery (P<0.001).

These findings, combined with clinical observations on the effects of spinal movements that open and close the IVF, have important clinical implications, as discussed below.

Figure 3.) Amplitude of compound muscle action potentials (CMAPs) in lumbar flexion and during intraoperative measurement. Amplitude of CMAPs was significantly smaller in lumbar extension (From Morishita et al 2006, buy paper).

Should Extension Movements Be Used for Lumbar Radiculopathy?

Clearly, a key clinical goal is to determine the basis for the sciatica. As mentioned above, there are many potential causes of pain in the distribution of the sciatic nerve, one of which is increased pressure in the IVF due to disc lesions. If genuine radiculopathy exists, movements that compress the nerve root (eg. lumbar extension) may be contraindicated.

Recommendations for Treatment of Patients with Sciatica Emanating From the Lumbar Spine

BACKGROUND

From the above research and clinical observations, there are times when spinal movements that produce closing around the nerve root and increased pressure in the canal or IVF may be hazardous. Extension is a key movement because of its propensity to produce such effects. However, generally, the effect of treatment techniques on patient responses must be established in all techniques whether they involve extension, flexion or movements.

CLINICAL PRIORITIES

• Prevent any adverse compression of the nerve root
  
  
• Ensure that all safety procedures have been executed prior to, during, and after reatment to determine that the treatment has NOT produced deleterious effects in the nerve root. It is one thing for the patient to leave with less pain but it is still incumbent on the practitioner to execute procedures that ensure that adverse effects have not also occurred.
  
  
• Clinically, it can be observed that pain and neurological changes to not always run in parallel. Therefore, even if the patientʼs symptoms improve, this does not necessarily mean that the nerve root pathology and conduction have also improved. In fact it can be observed clinically that, sometimes as pain improves, the neurological status can simultaneously deteriorate. Treatments that produce increased pressure on the nerve root are therefore contraindicated.

PHYSICAL EXAMINATION

Perform neurological examination as the first part of physical examination. Note any changes for reassessment.

Perform physical examination carefully, with respect the potential for nerve root pressure and provocation.

Reassess neurological status to establish that neurological status has not deteriorated. For instance if movements or manual techniques that close the canal or foramen are performed in the physical examination, it may be necessary to ensure that these alone do not produce a deterioration in nerve root function. If they do, they are contraindicated at this time.

If techniques that close the foramen eg. extension, ipsilateral lateral flexion or rotation, produce a deterioration in nerve root function, alternatives that produce the opposite mechanical effect around (opening of the foramen) may be indicated. These consist of the systematic progressions of opening techniques presented in Shacklock (2005, Figure 4).

Fig 4: patient position front
Fig 4: manual techniqueFigure 4.) Opening IVF technique for the lumbar nerve root in which closing movements eg. extension increase symptoms or produce a deterioration in nerve root function.

Left: patient position from the front – Right: manual technique (From Shacklock 2005, Clinical Neurodynamics, Elsevier, Oxford).

For information on treatment of the neural tension dysfunction component of the problem, click here