An Animal Model of Modic Changes by Embedding Autogenous Nucleus Pulposus inside Subchondral Bone of Lumbar Vertebrae

The establishment of Modic changes (MCs) in animal model was vital for research of MCs. Fifty-four rabbits were divided into a sham group, a muscle embedment group (ME group) and nucleus pulposus (NP) embedment group (NPE group). In the NPE group, the discs were exposed by the lumbar anterolateral surgical approach. A needle was used to puncture the L5 vertebral body close to the endplate. NP was extracted by a syringe from L1/2 intervertebral discs and then injected into the drilled hole of subchondral bone. The muscle embedment group and sham group had the same procedure and drill method as the NP embedment group. Some pieces of muscle were put into the hole in the ME group, but nothing was put into the hole in the sham group. After the operation, MRI scan and molecular biology tests were applied. The signal changes were found in the NPE group; while the sham group and the ME group showed no significant signal change. Histological observation confirmed that there was abnormal tissue proliferation in imbed site. High expression of IL-4, IL-17 and IFN-gamma were detected in the NPE group. The embedment of NP into subchondral bone can create an animal model of MCs.