low back pain: clinical exam pearls

26 Jul

Straight leg raise

useful to help confirm radiculopathy.

BASICS:

  • patient supine.
  • examiner raises the patient’s extended leg with the ankle dorsiflexed (passive)
  • test is positive when the sciatica is reproduced between 10 and 60 degrees of elevation.

A positive straight leg test is sensitive, but not specific, for herniated disc.

 

crossed straight leg raise test

test is positive when lifting the unaffected leg reproduces the sciatica in the affected leg.

less sensitive for herniated disks, but 90 percent specific.

 

neurologic testing should focus on the L5 and S1 nerve roots, since 98 percent of clinically important disc herniations occur at L4-5 and L5-S1

 

L5

  • motor testing evaluates strength of ankle and great toe dorsiflexion.
  • sensory: numbness in the medial foot and the web space between the first and second toe.

S1 nerve root

  • ankle reflexes and sensation at the posterior calf and lateral foot.
  • weakness of plantar flexion, but is difficult to detect until quite advanced (tip: have the patient raise up on tip-toe three times in a row, on one foot alone and then the other)
  • absence of ankle reflexes becomes increasingly common with age; Unilateral absence of ankle reflexes is uncommon, though (10% of those >60 yo)
  • therefore, unilateral absence of an ankle reflex is rare enough to be a clinically useful sign (specificity of 89 percent)

 

Nonorganic signs or Waddell’s signs

In patients with chronic pain, psychological distress may amplify low back symptoms, and may be associated with anatomically “inappropriate” physical signs.

 

The most reproducible of these signs are

  • superficial tenderness,
  • distracted straight leg raising (ie, discrepancy between seated and supine straight leg raising tests)
  • the observation of patient overreaction during the physical examination, also known as Waddell’s signs.

 

Other Waddell’s signs suggestive of symptom enhancement include

  • nondermatomal distribution of sensory loss,
  • sudden giving way or jerky movements with motor examination,
  • inconsistency in observed spontaneous activity (dressing, getting off table) and formal motor testing,
  • pain elicited by axial loading (pressing down on top of head, or rotating the body at hips or shoulders).

However, systematic reviews have not found an association between Waddell’s signs and psychological distress, or claims for disability compensation or litigation.

 

Submitted by J. Stanton.

 

References: uptodate.com; picture

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