Ability of a second generation Nucleus Pulposus Prosthesis (NPPv2.0) to restore axial disc height in canine cadaveric specimens both before and after biomechanical testing

Abstract

A new treatment option to restore the natural function of the nucleus pulposus function and thereby preventing further clinical signs of intervertebral disc degeneration (IVDD) is the insertion of a nucleus pulposus prosthesis (NPP) in a nucleotomized disc. In humans, disc prostheses are already sparsely being used, but for dogs this option is currently not yet available. The present study investigated whether after nuclectomy, insertion and swelling of second generation nucleus pulposus prosthesis (NPPv2.0) would restore the original axial disc height of an L2-L3 intervertebral disc. Canine cadaveric specimens of 11 healthy Beagles were used and biomechanical tests (flexion/extension, lateral bending, and axial rotation) were applied to the spinal segments L2-L4 to gain information about the restoration of the biomechanical properties and the axial disc height. The biomechanical tests were carried out on 1) the native spine, 2) after nuclectomy, and 3) after insertion and swelling of the NPPv2.0. Lateral and dorsoventral radiographs were obtained and measured twice by two independent observers with a method developed by Hofstetter et al, and a method developed by Twomey and Taylor. Compared to the intact spine, a significant (p<0.05) decrease in the mean disc height was found after biomechanical testing, using either measurement method. After insertion and swelling of the NPPv2.0, it was found that the mean disc height of an L2-L3 intervertebral disc can significantly be restored (p<0.05). Before we can test the NPPv2.0 in vivo in dogs some additional tests of the physical en biomechanical properties of the NPPv2.0 needs to be performed but preliminary results are looking promising. In the future the NPPv2.0 may be a valuable addition to the surgical treatment options currently available for canine and human IVDD patients.