Experimental study of the impact of different lumbar posterior approaches on multifidus muscle.

Objective To assess the effect of different surgical approaches on atrophy of multifidus muscle occurring after lumbar surgery. Methods Forty adult goats were randomly divided four groups.Group A underwent a spinous process-splitting procedure to expose the lamina; Group B did the bilateral multifidus muscles stripped and the spinous process excised; Group C underwent the cutting of the spinous process at the bottom, with unilateral multifidus muscle stripped (Group C1), and without stripped (Group C2); and Group D did the bilateral multifidus muscles stripped. Ten months after surgery, the atrophy rates of the cross-sectional areas, the subjective scores of fibrosis and fatty tissue infiltration of the bilateral multi-fidus muscles on MRI, and the histological assessment were evaluated. Normal multifidus muscles taken from healthy goats at L_6 level and the preoperative data of MRI in experimental animals provided control data.Results MRI and histological scores of multifidus muscles from Groups A, B, C1, C2, and D were signifi-cantly decreased, and the atrophy rate were significantly higher in comparison to control data. The postoper-ative MRI and histological scores of Group A and C2 were highest and the atrophy rate was lowest, while an-imals from Group B had highest atrophy rate and lowest MRI and histological scores among all experimental groups (P<0.05). The Groups A and C2 achieved lower atrophy rate, higher MRI and histological scores than those from Groups C1 and D which did have muscles stripped (P<0.05). The Groups C1 and D which recon-structed spinous process after detachment of muscles represented lower atrophy rate, higher MRI and histo-logical scores than Group B (P<0.05). The postoperative histological scores were positively correlated with MRI scores, but it had no correlation with atrophy rate of multifidus. Conclusion Multifidus muscle can be ef-fectively protected by reducing the extent of muscle detachment and reconstructing the posterior bone-ligament complex. The spinous process-splitting procedure is an effective method to avoid postoperative muscle atrophy. Key words: Lumbar vertebrae; Pathology; Magnetic Resonance Imaging; Goats