Experimental lumbar radiculopathy behavioral and histologic changes in a model of radicular pain after spinal nerve root irritation with chromic gut ligatures in the rat

Mamoru Kawakami, James Neil Weinstein*, Ken Ichi Chatani, Kevin F. Spratt, Stephen T. Meller, G. F. Gebhart

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

121 Scopus citations

Abstract

Objective. The recently proposed animal model of lumbar radiculopathy was used to investigate behavioral consequences and histologic changes in spinal nerve roots, dorsal root ganglia, and spinal nerves after the L4, L5, arid L6 nerve roots were loosely ligated with either silk or chromic gut sutures in an attempt tc better understand the pathophysiologic mechanisms that give rise to pain associated with lumbar radiculopathy, Summary of Background Data. Little is known about Ihe pathophysiologic mechanisms that give rise to pain associated with lumbar radiculopathy. The recently proposed animal model of unilateral lumbar radiculopathy, which demonstraied an association with motor paresis antt thermal hyperalgesia of the affected hind rimb and showed evidence of spontan&uue pam ha3 been demonstrated, may serve as a vehicle to allow direct investigation of the nature of the pathophysiological mechanisms associated with lumbar radiculopathy. Methods. Three distinct treatments of the nerve roots wera initially investigated; 1) a sham intervention, where the surgery simply exposed the nerve roots and dorsal root ganglion followed by standard closing procedures; 2) 4-0 silk ligature, where two loose ligatures of 4-0 silk were placed around the nerve roots; and 3) 4-0 chromic gut 2, where four 0.3 cm pieces of 4-0 Chromic gut wero laid adjacent to the nerve roots end secured by two loose ligatures of 4-3 chromic gut. Study Design. ANOVA techniques were used to test for differential effects across time for the three treatment groups in terms of animal function. A qualitative analysis of th& histology of the ipsilateral and contralateral nerve roots, dorsal root ganglia, and spinal nerves was done to correlate histologic changes with behavioral changes, Results. Behavioral results were consistent with the previous study. Rats treated with chromic gut, but not silk, reliably demonstrated a prolonged thermal hyper- algesia that was maximal 2 weeks after surgery and Tasted for up to 12 weeks. These behavioral changes, however, were not correlated with histologic changes in myelinated fiber content in the L4, L5, and L6 nerve roots, dorsal root ganglia and spinal nerves, the ipsllateral spinal nerved, dorsal root ganglia, and nerve roots of rates ligated with silk or chromic gut showed similar, significant, decreased in the number of large diameter myelinated fibers. Conclusions. These results suggest that mechanical constriction of the L4, L5, and LG spinal nerve roots, as evidenced by a loss of myelinated fibors, is not sufficient to produce the behavioral effects associated with this model of lumbar radiculopathy. It is hypothesized that chemical factors from the chromic gut play a role In the pathophysiology and development of the behavioral, but not histological, changes In this model of lumbar radiculopathy.

Original languageEnglish (US)
Pages (from-to)1795-1802
Number of pages8
JournalSpine
Volume19
Issue number16
DOIs
StatePublished - Aug 1994

Keywords

  • Animal model
  • Histology
  • Lumbar radiculopathy
  • Persistent pain
  • Thermal hyperalgesia

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Clinical Neurology

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