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Paraspinal Muscle Denervation, Paradoxically Good Lumbar Endurance, and an Abnormal Flexion–Extension Cycle in Lumbar Spinal Stenosis

Leinonen, Ville, MD*†; Määttä, Sara, MD; Taimela, Simo, DMSc§∥; Herno, Arto, DMSc*; Kankaanpää, Markku, DMSc*†; Partanen, Juhani, DMSc; Hänninen, Osmo, DMSc, PhD; Airaksinen, Olavi, DMSc*

doi: 10.1097/01.BRS.0000048495.81763.8C

Study Design. A descriptive study was conducted to investigate the paraspinal muscle function in patients with lumbar spinal stenosis.

Objective. To evaluate paraspinal muscle innervation and endurance in lumbar spinal stenosis.

Summary of Background Data. Abnormal lumbar paraspinal muscle function is associated with chronic low back pain. Abnormal neurophysiologic findings of the lower limbs often are observed in lumbar spinal stenosis, and abnormal lumbar function also can be expected. However, paraspinal muscle function and innervation have not been studied in lumbar spinal stenosis.

Methods. The study evaluated 25 patients with clinically and radiologically diagnosed lumbar spinal stenosis. Electromyography of the paraspinal muscles was performed from L3 to S1 bilaterally using a concentric needle. At least 20 insertions were analyzed from each muscle. The aim of the examination was to detect abnormal spontaneous activity associated with axonal damage (fibrillation potentials, positive sharp waves, and complex repetitive discharges). Paraspinal muscle activity during trunk flexion–extension movement and muscle endurance during the dynamic isoinertial back endurance test were assessed by surface electromyography. Muscle fatigue was calculated using mean power frequency analysis.

Results. Abnormal findings in needle electromyography of the paraspinal muscles were observed in 18 of the 22 (81.8%) examined patients. Abnormal flexion–extension activation of the paraspinal muscles was observed in all the examined patients. The change in mean power frequency was significantly smaller than in previously evaluated healthy subjects and patients with nonspecific chronic low back pain (P < 0.001) who were not experiencing symptoms of lumbar spinal stenosis. Paraspinal muscle fatigability was not associated with the denervation of the muscles.

Conclusions. Denervation and abnormal activation of lumbar paraspinal muscles are frequent findings in patients with lumbar spinal stenosis who have not undergone surgery. The paraspinal muscle endurance of the patients was unexpectedly good.

From the *Department of Physical and Rehabilitation Medicine, Kuopio University Hospital, Kuopio,

the †Department of Physiology, University of Kuopio, Kuopio,

the ‡Department of Neurophysiology, Kuopio University Hospital, Kuopio,

§DBC International, Helsinki,

and the ∥Haaga Neurological Research Centre, Helsinki, Finland.

Supported by the Ministry of Education and Academy of Finland (TULES Graduate School), the Finnish Medical Society Duodecim, the Kuopio University Hospital EVO Fund, and the Finnish Cultural Foundation.

Acknowledgment date: January 15, 2002.

First revision date: March 29, 2002. Second revision date: June 26, 2002.

Acceptance date: July 23, 2002.

Device status category: The devices and drugs that are the subject of this manuscript are not FDA-approved for this indication and not commercially available in the United States.

Conflict of interest category: Foundation funds were received to support this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Address reprint requests to Ville Leinonen, MD, Department of Physiology, University of Kuopio, P.O. Box 1627, FIN-70211 Kuopio, Finland. E-mail:

© 2003 Lippincott Williams & Wilkins, Inc.