NONINVASIVE MEASUREMENT OF SCIATIC NERVE STIFFNESS IN PATIENTS WITH CHRONIC LOW BACK RELATED LEG PAIN USING SHEAR WAVE ELASTOGRAPHY

BACKGROUND & OBJECTIVE

It has been shown there is increased cross sectional area and altered transverse displacement of the sciatic nerve in chronic low back related leg pain (CLBRLP) sufferers, as well as increased stiffness in other peripheral neuropathies. Little is known about the stiffness of the sciatic nerve in the CLBRLP population. Shear wave elastography is a reliable way of estimating neural stiffness in healthy and clinical populations. This study was designed to determine whether sciatic nerve stiffness is altered in people with CLBRLP. They hypothesized that nerve stiffness would be increased in the affected limb of people with CLBRLP.

METHODS

The sciatic nerve shear wave velocity (index of stiffness) was measured in both legs of 16 participants (8 with unilateral low back-related leg pain and 8 healthy controls) between 18-45yo with a BMI <30 and CLBRLP >6 months. Spinal surgery or acute states preventing them from assuming a prone position were used as exclusion criteria. Stiffness was measured 10cm below the gluteal fold during a passive ankle dorsiflexion motion performed at 2º/s in an isokinetic dynamometer. EMG was used to ensure passive motion. The ankle ROM and passive torque, as well as muscle activity, were also measured.

RESULTS

There were no significant differences found in demographics between the CLBRLP group and heathy controls. The stiffness measurements revealed good intra-rater reliability. During all measurements, the mean EMG values for semitendinosus, medial gastrocnemius, and tibialis anterior muscles were < 2.8%

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