Lower back pain continues to be a leading cause of disability in people of all ages, and has been associated with
degenerative disc disease. It is well accepted that mechanical stress, among other factors, can play a role in the
development of disc degeneration. Pressures generated in the intervertebral disc have been measured both in vivo and in
vitro for humans and animals. However, thus far it has been difficult to measure pressure experimentally in rodent discs
due to their small size. With the prevalent use of rodent tail disc models in mechanobiology, it is important to
characterize the intradiscal pressures generated with externally applied stresses.
In this paper, a miniature fiber optic Fabry-Perot interferometric pressure sensor with an outer diameter of 360 &mgr;m was
developed to measure intradiscal pressures in rat caudal discs. A low coherence interferometer based optical system was
used, which includes a broadband light source, a high-speed spectrometer, and a Fabry-Perot sensor. The sensor employs
a capillary tube, a flexible, polymer diaphragm coated with titanium as a partial mirror, and a fiber tip as another mirror.
The pressure induced deformation of the diaphragm results in a cavity length change of the Fabry-Perot interferometer
which can be calculated from the wavelength shift of interference fringes. The sensor exhibited good linearity with small
applied pressures. Our validation experiments show that owing to the small size, inserting the sensor does not disrupt
the annulus fibrosus and will not alter intradiscal pressures generated. Measurements also demonstrate the feasibility of
using this sensor to quantify external load intradiscal pressure relationships in small animal discs.