Physical characteristics of the axial interosseous ligament of the human sacroiliac joint.
BACKGROUND
Although the sacroiliac joint has occupied a place in medical literature since at least the eighteenth century, its role in normal function and dysfunction of the back and hip remains controversial. The controversy persists, because there is still no suitable method to study the role of stability and mobility at the sacroiliac joints in vivo. One cost-effective approach to understanding such complex, deeply placed structures is biomechanical modeling. Unfortunately, very few data on the mechanical properties of tissues in this region are currently available to modelers.


OBJECTIVE
The objective of this preliminary project was to determine some mechanical properties of the axial interosseous ligament (AIL), and to investigate the histology of the ligament.


METHODS
A modified split plot design was used in conjunction with descriptive statistics to identify AIL characteristics.


METHODS
This was a cadaveric study.


METHODS
The study used descriptive statistics to categorize the ultimate failure strength of the AIL, and to describe the macro-constituents of the ligament.


METHODS
Eighteen sacroiliac joints were harvested from nine fresh female cadavers (age range, 54 to 92). Data from 10 joints submitted to mechanical testing are reported. The eight remaining joints were used for histologic analysis of the AIL by light microscopy.


RESULTS
The AIL proved to be relatively weak, with a mean failure load of 381 N (SD 43.7N) and a peak stress of 1.73 MPa (SD 0.99 MPa). Histologically, the AIL contained significantly less collagen than most other "typical" ligaments.


CONCLUSIONS
The AIL failure loads are just slightly higher than those for the ligamentum flavum in the spine, a tissue composed mainly of elastic fibers. In contrast, the AIL has negligible elastin content. Because the AIL represents about 14% of the total area of interosseous sacroiliac ligaments, its mechanical properties should be useful to modelers of the joint. In addition, it appears that injury to the AIL would do little to compromise the mechanical integrity of the sacroiliac joint. Further study of this ligament seems warranted.
Department of Physical Therapy, University of Maryland, Baltimore, School of Medicine, 100 Penn Street, Suite 115, Baltimore, MD 21201, USA. rbechtel@umaryland.edu
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D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D004210:Dissection; D005260:Female; D006801:Humans; D017746:Joint Capsule / Q000502:physiology; D008023:Ligaments, Articular / Q000502:physiology* / Q000648:ultrastructure; D008875:Middle Aged; D012446:Sacroiliac Joint / Q000502:physiology*; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D013718:Tensile Strength; D016474:Weight-Bearing