In vitro measurements of porcine anterior column units under free swelling

The objectives of this study are to present a 2-D optical method for measuring gross kinematics of porcine anterior column units (ACUs) exposed to swelling with no applied load, provide a detailed error analysis of the 2-D optical measurement technique, and present a 2-D radiographic technique for measuring the distribution of x-ray intensity through an axial slice of the disc. The 2-D optical technique was sufficient for detecting the flexion-extension behavior of the ACUs tested. The error analysis concluded that the use of a second camera to quantify out of plane movement of the specimen would greatly improve the accuracy of the measurement of angle. The 2-D radiographic technique provided limited information on changes in intradiscal material. It was also limited in its accuracy and dependability (i.e., only 5 out of 13 specimens provided radiographs suitable for this analysis). The results of this study indicate that a relationship might exist between the flexion-extension behavior observed from swelling and intradiscal shifts of matter. Further work is needed to confirm this relationship.