Background: Numerous animal models of intervertebral disc (IVD) degeneration have been proposed in the literature. The rat caudal disc has been used in disc degeneration studies because of its low cost and simplicity. However, no consensus on the size of the needle to be used during this process has been reached, yet.
Objectives: This study aims to select an optimal needle size to establish a reproducible IVD degeneration model.
Study design: This is a randomized, experimental trial.
Setting: Cell therapy and experimental surgery of musculoskeletal system LR18SP1 Lab, The Faculty of Medicine of Sfax, Tunisia.
Methods: The validity was verified by magnetic resonance imaging (MRI), histological, and immunohistochemical examinations.
Results: The MRI, histological, and immunohistochemical examinations showed that a disc that is perforated with a 21G needle degenerated acutely one week after the surgery, while a 29G needle puncture failed to develop disc degeneration. A 25G needle induced progressive degeneration in the IVD.
Limitations: This study was not very long (6 weeks).
Conclusions: We conclude that the size of the needle affects the onset and the progression of disc degeneration; a larger needle size leads to a more extended histological and radiographic degeneration within the IVD and in a relatively short time. Therefore, a 21G needle is an optimal choice to induce rapid degeneration in rats' caudal discs. However, the use of a 29G needle failed to establish a degenerative IVD model, which makes it ideal for IVD injection of drugs, plasmids, and growth factors. A 25G needle may be used to induce gradual degeneration.
Keywords: animal model; caudal spine; different needle sizes; optimal choice; Degenerative intervertebral disc.