Abstract

Purpose. The present work hypothesized that proteolytic dissolution of intervertebral discs could induce biomechanical change comparable to the change observed in natural disc degeneration. A method to do such could be utilized for in vitro research where intersample differences in geometry and chemical makeup render it difficult to compare and aggregate results into generalized conclusions.
Methods. Forty-one bovine coccygeal intervertebral discs were isolated with individual functional spinal units. Samples were loaded in three modes: compression/tension, flexion/extension, and axial rotation. The anulus fibrosus of each disc was injected with 200µl trypsin or fetal bovine serum (control) and incubated for an allotted period: 30 minute, 60 minutes, or 180 minutes. Mechanical loading was repeated and the load-displacement responses before and after treatment were compared as were the differences between each time group.
Results. Significant change was observed in the discs' total range (stiffness), low range (laxity), and hysteresis. Changes in load-displacement response were observed to be correlated with both treatment and time.
Conclusions. Enzymatic degeneration of intervertebral discs shows promise as a means to further understanding of disc mechanics in varying levels of degeneration. In virtually all cases, the trypsinized discs exhibited the increased joint laxity and decreased stiffness that is associated with early stage, natural disc degeneration.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering

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