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Extrusion or protrusion of an intervertebral disc is a common, frequently debilitating, painful, and
sometimes fatal neurologic disease in the chondrodystrophic dog (dachshund, Pekingese, etc.). A similar
condition of intervertebral disc degeneration with extrusion/protrusion is also a relatively common
neurologic condition in human patients. Degeneration of the relatively avascular chondrodystrophoid
intervertebral disc is associated with loss of water content, increased collagen, and deposits of calcified
mineral in the nucleus pulposus. Current diagnostic methods have many limitations for providing accurate
information regarding disc composition in situ prior to surgical intervention. Disc composition (i.e.,
mineralization), can influence the type of treatment regime and potentially prognosis and recurrence rates.
The objective of this study is to investigate the feasibility of using a fiber-needle spectroscopy sensor to
analyze the changes of tissue compositions involved in the chondrodystrophoid condition of the canine
intervertebral disc. The nucleous pulposus, in which the metaplastic process / degeneration develops, is
approximately 2mm thick and 5mm in diameter in the dachshund-sized dog. It lies in the center of the
disc, surrounded by the annulus fibrosis and is enclosed by cartilaginous vertebral endplates cranially and
caudally. This "shallow-and-small-slab" geometry limits the configuration of a fiber probe to sense the
disc tissue volume without interference from the vertebrae. A single-fiber sensor is inserted into a 20
gauge myelographic spinal needle for insertion into the disc in situ and connected via a bifurcated fiber to
the light source and a spectrometer. A tungsten light source and a 940nm light-emitting-diode are
combined for spectral illumination covering VIS/NIR with expected improved sensitivity to water.
Analysis of the reflectance spectra is expected to provide information of scattering and absorption
compositions of tissue in proximity to the fiber-tip. Preliminary measurements on cadaveric canine
intervertebral discs indicated significant reduction of scattering constituents and possible diminishment of
water content after percutaneous laser disc ablation (PLDA). This fiber-needle based sensing
configuration may be feasible for integrating the evaluation of calcification and water content into the
work-flow of holmium:YAG laser disc ablation for pre-operative in-line detection and post-operative
evaluation of therapeutic interventions regarding the chondrodystrophic disc.
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