A porcine model of intervertebral disc degeneration induced by annular injury characterized with magnetic resonance imaging and histopathological findings. Laboratory investigation.
OBJECTIVE
Appropriate animal models of disc degeneration are critical for the study of proposed interventions as well as to further delineate the degenerative process. The purpose of this study was to characterize a porcine model for disc degeneration confirmed on magnetic resonance (MR) imaging studies and histological analysis.


METHODS
Twelve miniature pigs were used (weight 48-65 kg) to study degeneration in the lumbar spine. Under fluoroscopic guidance, the disc was percutaneously punctured with a 3.2-mm-diameter trephine to a 5-mm depth into the annulus fibrosus. Control and experimental levels were randomized among 6 levels in the lumbar spine. The unlesioned spinal levels were used as controls and were compared with lesioned levels. Magnetic resonance imaging grading and disc height were serially recorded preoperatively, and at 5, 8, 19, 32, and 39 weeks postoperatively. The animals were killed in groups of 3 at 7, 18, 32, and 41 weeks postinjury, and the discs were examined histopathologically.


RESULTS
Consistent, sequential, and progressive degeneration of the annular injury was observed on MR imaging and histopathological studies from the time of injury to the final time point. The disc height and the disc height index also sequentially decreased from the time of the injury in a consistent manner. The uninjured control levels did not show any progressive degeneration and maintained their normal state.


CONCLUSIONS
Based on MR imaging and histopathological findings, the authors demonstrated and characterized a reliable model of sequential disc degeneration in miniature pigs with percutaneous injury to the annulus fibrosus. In the early stages, as soon as 5 weeks after injury, significant disc degeneration was seen on MR imaging grading with decreases in disc height. This degeneration did not improve by the final time point of 39 weeks.
Yoon
Seung-Hwan
SH
Department of Neurosurgery, Inha University Hospital, Incheon, Korea.
Miyazaki
Masashi
M
Hong
Soon-Woo
SW
Tow
Ben
B
Morishita
Yuichiro
Y
Hu
Ming
M
Ahn
Sung-Joon
SJ
Wang
Jeffrey C
JC
D000818:Animals; D019902:Chondrocytes / Q000473:pathology; D004396:Coloring Agents; D003238:Connective Tissue / Q000473:pathology; D004195:Disease Models, Animal; D018450:Disease Progression; D005260:Female; D005456:Fluorescent Dyes; D007403:Intervertebral Disc / Q000293:injuries* / Q000473:pathology; D008159:Lumbar Vertebrae / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008867:Microtomy; D011897:Random Allocation; D013122:Spinal Diseases / Q000175:diagnosis / Q000209:etiology* / Q000473:pathology; D013552:Swine; D013556:Swine, Miniature; D013997:Time Factors
D004396:Coloring Agents; D005456:Fluorescent Dyes