Computed tomography-guided nucleus pulposus biopsy for canine intervertebral disc degeneration preparation: a radiology and histology study.

Background Context: Different animal models are being used in disc degenerative disease (DDD) research; most of these models are induced invasively rather than noninvasively. Computed tomography (CT)-guided percutaneous biopsy, widely used in clinical malignant pathology diagnosis, is a safe, useful, and highly accurate procedure. However, this process was not carried out in animal model preparation of intervertebral disc degeneration.

Purpose: To apply a minimally invasive method in DDD animal model preparation with a biopsy gun guided by CT scan and evaluate the accuracy and efficiency of this process with radiology and histology analyses. The relationship between the weight of removed nucleus pulposus (NP) and the degenerative process was also explored preliminarily.

Methods: The canine intervertebral discs L1-L2, L3-L4, and L5-L6 were divided into three groups randomly: Group A: 18G biopsy gun; Group B: 20G biopsy gun; and Group C: 24G biopsy gun. After the lumbar spine was scanned with CT and the depth and angle of the centesis operation sites ascertained, biopsy gun was stabbed percutaneously through the annulus into the NP. A certain volume of NP tissue was removed by the biopsy gun. Radiology examination, including digital radiography (DR) and magnetic resonance imaging (MRI), was carried out preoperatively and at first and third months postoperatively. Each sample was harvested at the 3rd month postoperation for histology evaluation.

Results: Computed tomography-guided percutaneous biopsy with 18G, 20G, and 24G biopsy guns was carried out for six discs, respectively. In the procedure, the weight of the NP tissue was removed: 3.0±0.53mg in Group A, 2.01±0.34 mg in Group B, and 0.99±0.12 mg in Group C. Significant differences of the weight of the removed NP tissue were calculated between groups (p<.05). During the observation period, although the disc height of Group A and B was reduced, no significant differences in the disc height comparison were found between groups at each time point and within groups at different time points in DR analysis. However, the signal intensity of MRI was reduced significantly (p<.05) in Group A when compared with Group C at third month, whereas the signal intensity was decrease mildly (p>.05) in Group B when compared with Group C at third month. The decreased content of NP, the number of NP cells, and the loose annulus fibrosus at the inner area was observed in both hematoxylin-eosin and Safranin-O staining in Group A at the 3rd month postoperation.

Conclusions: Computed tomography-guided percutaneous biopsy could be applied in intervertebral disc degeneration preparation of canine model, and the 20G biopsy gun would be the optimal choice in this procedure. The intervertebral disc degenerative process could be forecasted approximately on an account of the negative association between the degeneration process and the weight of the removed NP tissue.