1: Spine. 1996 Nov 15;21(22):2539-43.  

Incision of the anulus fibrosus induces nerve root morphologic, vascular, and
functional changes. An experimental study.

Kayama S, Konno S, Olmarker K, Yabuki S, Kikuchi S.

Department of Orthopaedic Surgery, Fukushima Medical College, Japan.

STUDY DESIGN: The effects on nerve root structure, vasculature, and function
after incision of the adjacent disc was studied in a dog model. OBJECTIVES: To
see if only incision of the disc per se is sufficient for inducing similar
changes. SUMMARY OF BACKGROUND DATA: It is well known that nucleus pulposus will
induce nerve root structural and functional changes in experimental situations.
In these previous studies, relatively large amounts of nucleus pulposus were
applied. METHODS: The left L7 nerve root was exposed and mobilized in 10 dogs.
In five dogs, the adjacent L6-L7 disc was incised, and in five other dogs, the
disc was not incised. After 7 days, nerve conduction velocity was recorded, and
specimens were obtained for histologic evaluation. RESULTS: The nerve conduction
velocity was significantly lower in the incision group (13 +/- 14 m/sec)
compared with the nonincision group (73 +/- 5 m/sec). Structural changes of the
axons were more pronounced in the incision group, however, the degree and
distribution was too limited to fully account for the neurophysiologic reactions
observed. There aims were obvious signs of capillary stasis with an increased
number and diameter of the intraneural capillaries in the incision group.
CONCLUSIONS: The present study indicated that incision of the anulus fibrosus is
sufficient to induce significant morphologic and functional changes and that
vascular mechanisms may be of importance for the observed changes. These
experimental data suggest that leakage of nucleus pulposus material from anular
tears, with injury to adjacent nerve roots, might be one pathophysiologic
mechanism in patients with low back pain and sciatica but with no radiologic or
surgical evidence of disc herniation.

PMID: 8961440 [PubMed - indexed for MEDLINE]