Histologic analysis of neural elements in the human sacroiliac joint.
METHODS
The posterior ligament of the human sacroiliac joint was examined for nerves and nerve endings using histologic and immunohistochemical techniques.


OBJECTIVE
To identify nerve fibers and mechanoreceptors in the posterior ligament.


BACKGROUND
According to the findings of previous studies, the human sacroiliac joint receives myelinated and unmyelinated axons that presumably conduct pain and proprioceptive impulses derived from mechanoreceptors and free nerve endings in the human sacroiliac joint.


METHODS
Tissue obtained from six patients was stained with gold chloride and that obtained from six additional patients was stained using antibodies specific for substance P and protein gene product 9.5.


RESULTS
The staining of joint tissue using the gold chloride technique showed myelinated and unmyelinated nerve fibers, two morphotypes of paciniform encapsulated mechanoreceptors, and a single nonpaciniform mechanoreceptor. Analysis using immunohistochemical staining for protein gene product 9.5 did not unequivocally show axons, nerve fascicles, or mechanoreceptors. Similarly, analysis based on immunohistochemical staining for substance P, one of several neurotransmitters known to signal pain from the periphery, showed reactive elements that may have been nerves, but because of background staining, could not be positively identified as such.


CONCLUSIONS
The presence of nerve fibers and mechanoreceptors in the sacroiliac ligament demonstrates that the central nervous system receives information, certainly proprioceptive, and possibly pain from the sacroiliac joint. Although it is not known how the central nervous system uses such information, it seems reasonable to speculate that the proprioceptive information is used to optimize upper body balance at this joint. In addition, because the staining techniques used generally to show nerves and nerve elements in periarticular connective tissue are nonspecific, the distinction between neural and nonneural should be made on the basis of both morphologic and staining characteristics.
Vilensky
Joel A
JA
Departments of Anatomy and Microbiology, Indiana University School of Medicine, Fort Wayne, Indiana. vilensk@ipfw.edu
O'Connor
Brian L
BL
Fortin
Joseph D
JD
Merkel
Glenn J
GJ
Jimenez
Ana M
AM
Scofield
Barbara A
BA
Kleiner
Jeffrey B
JB
D000328:Adult; D001174:Arthrodesis; D017612:Gold Compounds; D006801:Humans; D007150:Immunohistochemistry; D008022:Ligaments / Q000166:cytology / Q000294:innervation; D008465:Mechanoreceptors / Q000166:cytology; D008875:Middle Aged; D009411:Nerve Endings / Q000166:cytology*; D009412:Nerve Fibers; D012446:Sacroiliac Joint / Q000166:cytology / Q000294:innervation* / Q000378:metabolism / Q000601:surgery; D013373:Substance P / Q000096:biosynthesis; D013869:Thiolester Hydrolases / Q000096:biosynthesis; D043222:Ubiquitin Thiolesterase
D017612:Gold Compounds; C038016:gold chloride; D013373:Substance P; D013869:Thiolester Hydrolases; D043222:Ubiquitin Thiolesterase