Spine www.spinejournal.com E919 B ASIC S CIENCE SPINE Volume 38, Number 15, pp E919-E924 ©2013, Lippincott Williams & Wilkins Comparison of CatWalk Analysis and von Frey Testing for Pain Assessment in a Rat Model of Nerve Crush Plus Inflammation Takafumi Sakuma, MD, Hiroto Kamoda, MD, PhD, Masayuki Miyagi, MD, PhD, Tetsuhiro Ishikawa, MD, PhD, Gen Arai, MD, Yawara Eguchi, MD, PhD, Miyako Suzuki, MD, PhD, Yasuhiro Oikawa, MD, Yoshihiro Sakuma, MD, Go Kubota, MD, Kazuhide Inage, MD, Takeshi Saino, MD, Sumihisa Orita, MD, PhD, Kazuyo Yamauchi, MD, PhD, Gen Inoue, MD, PhD, Kazuhisa Takahashi, MD, PhD, and Seiji Ohtori, MD, PhD DOI: 10.1097/BRS.0b013e318297bfb6 Study Design. Assessment of pain-related behavior and immuno- histology of the dorsal root ganglion in a rat model. Objective. To investigate pain-related behavior in a rat model of nerve crush plus inflammation using the CatWalk system. Summary of Background Data. A definitive method for evaluating animal models of lumbar disease has not been established. Von Frey testing has often been used in this type of study, but the reliability remains in question. The CatWalk system is a computer-assisted apparatus for analyzing gait that provides an automated way to assess gait function during pain. However, there have been few reports using this system for models of lumbar disease. Methods. Fourteen rats were divided into 2 groups: a treatment group and a sham group. For the treatment group, nucleus pulposus was applied to the sciatic nerve and the sciatic nerve was pinched. Two different methods for assessment of pain-related behavior, von Frey testing and CatWalk analysis, were used before surgery and at 4 and 7 days after surgery. Immunohistochemistry was used to examine calcitonin gene-related peptide expression in L4 to L6 dorsal root ganglia. Results. No significant differences were found between the treatment and sham control groups using von Frey testing. How- ever, significant differences in 4 parameters were found between the 2 groups using the CatWalk system ( P < 0.05). The propor- tion of calcitonin gene–related peptide-immunoreactive neurons was higher in the treatment group than in the control group ( P < 0.05). From the Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, Inohana, Chuo-ku, Chiba, Japan. Acknowledgment date: April 24, 2012. First revision date: December 7, 2012. Second revision date: April 8, 2013. Acceptance date: April 10, 2013. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No relevant financial activities outside the submitted work. Address correspondence and reprint requests to Hiroto Kamoda MD, PhD, Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba, 260-8677, Japan; E-mail: kamodahiroto@gmail.com V arious kinds of behavioral tests are used for assessing animal models in pain research. Usually, escape behavior from mechanical or thermal stimuli of the planter surface is observed, and the strength of pain is quan- tified by a withdrawal threshold. To date, von Frey testing is among the most common and reliable methods for stimulat- ing the skin mechanically to estimate the sensitivity of the stimulus area. 1,2 This test has been used for the evaluation of mechanical hyperalgesia induced by inflammation and tissue or nerve injury. 3–5 Some authors have reported behavioral changes with von Frey testing in rodent models of lumbar disease such as lumbar disc hernia or spinal stenosis. 6–8 However, it is known that when the entrapment of spinal nerves occurs in lumbar disease, lower extremity hypoalge- sia is clinically observed in humans. 9,10 It is doubtful whether using this conventional method to quantify skin sensitivity is a feasible way to evaluate pain severity in animal models of lumbar disease. The CatWalk system is a comparatively new method of measuring rodent gait parameters and has been used for the assessment of pain in models of allodynia and arthritis. 11,12 In this study, we constructed a model of nerve crush plus inflammation in rats and compared behavioral changes to estimate the severity of pain using von Frey testing and the CatWalk system. We also examined changes in calcitonin gene-related peptide (CGRP) expression in dorsal root gan- glion (DRG) neurons. CGRP is a marker of sensory neurons involved mainly in nociception and is considered to be a marker of inflammatory pain. 13 Conclusion. Our results demonstrate that the CatWalk system is useful for the measurement of pain-related behavioral change in our rat model in which nociception was indicated at a cellular level. Although further studies are needed, we think that this system is a valid alternative method for the evaluation of models of lumbar disease in rodents. Key words: CatWalk, von Frey test, lumbar disc hernia, dorsal root ganglion, calcitonin gene-related peptide. Spine 2013;38:E919–E924 Copyright © 2013 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.