Multifidus Muscle Atrophy Not Observed Following Two-segment Anterior Interbody Fusion: A Rabbit Model Study With a 12-Month Follow-up.
METHODS
Experimental study evaluated magnetic resonance imaging (MRI) and histologic changes in the multifidus muscle after anterior spinal fusion.


OBJECTIVE
To determine the effect of spinal fusion on the multifidus muscle in an anterior rabbit model through the use of MRI and histologic evaluation.


BACKGROUND
Retraction and splitting approach are known to be important factors in postoperative injury and atrophy of the multifidus muscle. The effect and possible mechanism of spinal fusion as an independent factor remains unknown.


METHODS
Thirty-six New Zealand white rabbits were divided into two groups. Animals in the fusion group underwent two-level anterior spinal fusion whereas those in the control group underwent similar surgery without spinal fusion. The status of the multifidus muscle was evaluated with MRI and histological analysis at preoperative, 3 weeks, 6 weeks, 3 months, 6 months, and 12 months postoperatively.


RESULTS
All rabbits in the fusion group achieved solid fusion. The mean T1-weighted and T2-weighted signal intensity ratios of gross multifidus to psoas muscles were all approximately 1.0 postoperatively, with no remarkable difference between the groups. The mean lesser diameter of myofibrils in either group did not significantly differ between the preoperative and postoperative specimens. There was no significant fibrotic change or fatty degeneration for either group. Decrease in acetylcholine activity or granular degeneration of the neuromuscular junction were not observed, and normal shape and size were found in nearly all samples at all time points in both groups (P > 0.05).


CONCLUSIONS
After two-segment anterior spinal fusion, multifidus atrophy was not observed throughout a 12-month follow up. The rabbit model of anterior fusion is better suited to study the effect of fusion alone on the status of the multifidus muscle.


METHODS
3.
Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China.|Key Laboratory of Biotherapy of Zhejiang Province Hangzhou, China.
Wen-Bin
WB
Xu
Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China.|Key Laboratory of Biotherapy of Zhejiang Province Hangzhou, China.
Jun-Hui
JH
Liu
Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China.|Key Laboratory of Biotherapy of Zhejiang Province Hangzhou, China.
Zhi-Jun
ZJ
Chen
Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China.|Key Laboratory of Biotherapy of Zhejiang Province Hangzhou, China.
Xiang-Qian
XQ
Fang
Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China.|Key Laboratory of Biotherapy of Zhejiang Province Hangzhou, China.
Shun-Wu
SW
Fan
Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China.|Key Laboratory of Biotherapy of Zhejiang Province Hangzhou, China.
Zhi-Jun
ZJ
Hu
D000818:Animals; D004195:Disease Models, Animal; D005500:Follow-Up Studies; D008159:Lumbar Vertebrae / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods; D009133:Muscular Atrophy; D064170:Paraspinal Muscles / Q000473:pathology*; D016658:Psoas Muscles / Q000473:pathology*; D011817:Rabbits; D013123:Spinal Fusion / Q000379:methods
Yoo JS, Min SH, Yoon SH, et al. Paraspinal muscle changes of unilateral multilevel minimally invasive transforaminal interbody fusion. J Orthop Surg ResV 9 2014; 130.
Kamaz M, Kiresi D, Oguz H, et al. CT measurement of trunk muscle areas in patients with chronic low back pain. Diagn Interv Radiol 2007; 13:144–148.
Barker KL, Shamley DR, Jackson D. Changes in the cross-sectional area of multifidus and psoas in patients with unilateral back pain: the relationship to pain and disability. Spine 2004; 29:E515–E519.
Ploumis A, Michailidis N, Christodoulou P, et al. Ipsilateral atrophy of paraspinal and psoas muscle in unilateral back pain patients with monosegmental degenerative disc disease. Br J Radiol 2011; 84:709–713.
Hu ZJ, Fang XQ, Fan SW. Iatrogenic injury to the erector spinae during posterior lumbar spine surgery: underlying anatomical considerations, preventable root causes, and surgical tips and tricks. Eur J Orthop Surg Traumatol 2014; 24:127–135.
Mayer TG, Vanharanta H, Gatchel RJ, et al. Comparison of CT scan muscle measurements and isokinetic trunk strength in postoperative patients. Spine 1989; 14:33–36.
Jonsson B. The functions of individual muscles in the lumbar part of the spinae muscle. Electromyography 1970; 10:5–21.
Hu Y, Leung HB, Lu WW, et al. Histologic and electrophysiological changes of the paraspinal muscle after spinal fusion: an experimental study. Spine 2008; 33:1418–1422.
Lu WW, Hu Y, Luk KD, et al. Paraspinal muscle activities of patients with scoliosis after spine fusion: an electromyographic study. Spine 2002; 27:1180–1185.
Kim CW. Scientific basis of minimally invasive spine surgery: prevention of multifidus muscle injury during posterior lumbar surgery. Spine 2010; 35:S281–S286.
Hu ZJ, Fang XQ, Zhou ZJ, et al. Effect and possible mechanism of muscle-splitting approach on multifidus muscle injury and atrophy after posterior lumbar spine surgery. J Bone Joint Surg Am 2013; 95:e192(1-9).
Grauer JN, Erulkar JS, Patel TC, et al. Biomechanical evaluation of the New Zealand white rabbit lumbar spine: a physiologic characterization. Eur Spine J 2000; 9:250–255.
Shrout PE, Fleiss JL. Intraclass correlations: uses in assessing rater reliability. Psychological bulletin 1979; 86:420–428.
Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spine surgery, Part 1: histologic and histochemical analyses in rats. Spine 1994; 19:2590–2597.
Boden SD, Schimandle JH, Hutton WC. An experimental lumbar intertransverse process spinal fusion model. Radiographic, histologic, and biomechanical healing characteristics. Spine 1995; 20:412–420.
Erulkar JS, Grauer JN, Patel TC, et al. Flexibility analysis of posterolateral fusions in a New Zealand white rabbit model. Spine 2001; 26:1125–1130.
Strube P, Putzier M, Streitparth F, et al. Postoperative posterior lumbar muscle changes and their relationship to segmental motion preservation or restriction: a randomized prospective study. J Neurosurg Spine 2016; 24:25–31.
Remes V, Lamberg T, Tervahartiala P, et al. Long-term outcome after posterolateral, anterior, and circumferential fusion for high-grade isthmic spondylolisthesis in children and adolescents: magnetic resonance imaging findings after average of 17-year follow-up. Spine 2006; 31:2491–2499.
Dickerman RD, East JW, Winters K, et al. Anterior and posterior lumbar interbody fusion with percutaneous pedicle screws: comparison to muscle damage and minimally invasive techniques. Spine 2009; 34:E923–E925.
Kramer M, Katzmaier P, Eisele R, et al. Surface electromyography-verified muscular damage associated with the open dorsal approach to the lumbar spine. Eur Spine J 2001; 10:414–420.
Gejo R, Matsui H, Kawaguchi Y, et al. Serial changes in trunk muscle performance after posterior lumbar surgery. Spine 1999; 24:1023–1028.
Gejo R, Kawaguchi Y, Kondoh T, et al. Magnetic resonance imaging and histologic evidence of postoperative back muscle injury in rats. Spine 2000; 25:941–946.
Schimandle JH, Boden SD. Spine update. The use of animal models to study spinal fusion. Spine 1994; 19:1998–2006.
Wang JC, Kanim LE, Yoo S, et al. Effect of regional gene therapy with bone morphogenetic protein-2-producing bone marrow cells on spinal fusion in rats. J Bone Joint Surg Am 2003; 85-A:905–911.
Drespe IH, Polzhofer GK, Turner AS, et al. Animal models for spinal fusion. Spine 2005; 5:S209–S216.
Smucker JD, Petersen EB, Fredericks DC. Assessment of MASTERGRAFT PUTTY as a graft extender in a rabbit posterolateral fusion model. Spine 2012; 37:1017–1021.
Zhu W, Rawlins BA, Boachie-Adjei O, et al. Combined bone morphogenetic protein-2 and -7 gene transfer enhances osteoblastic differentiation and spine fusion in a rodent model. J Bone Miner Res 2004; 19:2021–2032.
Boden SD, Martin GJ Jr, Morone M, et al. The use of coralline hydroxyapatite with bone marrow, autogenous bone graft, or osteoinductive bone protein extract for posterolateral lumbar spine fusion. Spine 1999; 24:320–327.
Scott TP, Phan KH, Tian H, et al. Comparison of a novel oxysterol molecule and rhBMP2 fusion rates in a rabbit posterolateral lumbar spine model. Spine 2015; 15:733–742.
Huang JW, Lin SS, Chen LH, et al. The use of fluorescence-labeled mesenchymal stem cells in poly(lactide-co-glycolide)/hydroxyapatite/collagen hybrid graft as a bone substitute for posterolateral spinal fusion. J Trauma 2011; 70:1495–1502.
Lu SS, Zhang X, Soo C, et al. The osteoinductive properties of Nell-1 in a rat spinal fusion model. Spine 2007; 7:50–60.
Yamaguchi T, Inoue N, Sah RL, et al. Micro-computed tomography-based three-dimensional kinematic analysis during lateral bending for spinal fusion assessment in a rat posterolateral lumbar fusion model. Tissue Eng Part C Methods 2014; 20:578–587.