BACKGROUND: Minimally invasive surgery displays differences in symptoms, signs, incision size, bleeding, and postoperative imaging from conventional open approach. However, these do not exhibit advantages of minimally invasive surgery.
OBJECTIVE: With erector muscle of spine histopathological changes as quantification standard to compare effects of percutaneous and conventional open approach for posterior lumbar surgery.
METHODS: A total of 24 rabbits were randomly assigned to three groups. In conventional group, a 7-cm incision was made from spina iliace plane to rostral end along spinous process, and erector muscle of spine was tracted for 0.5 hours under certain pressure. In the percutaneous group, the guide pin was inserted into lumbar vertebral lamina, 0.5-1.0 cm from midline of 5th and 7th spinous process, expansion and working channels were implanted through the guide pin, and device was implanted and maintained for 0.5 hours. The control group was not treated. Morphological change of the erector spinae was observed by light microscope and transmission electron microscope at 3 days, 1, 2, 3 weeks, and 1, 3, 6 months after surgery.
RESULTS AND CONCLUSION: For conventional group, the pathological changes of muscle fiber included the intercellular edema, inflammatory cell infiltration, even cerosis, colliquative necrosis in the early stage. By one week postoperatively the muscle fiber necrosis was gradually obvious, regeneration of muscle fibers and neuromuscular junction began at the presence of fiber atrophy and fiber type grouping. The late pathohistological examinations showed fiber atrophy and type grouping, centronucleus fiber regeneration, severe adipose infiltration, monocyte hyperplasy, mesenchyme infiltration and fibrosis, muscle fibers almost replaced by connective tissues or scar. The ultrastructure examinations showed a parallelism with histological examinations. Muscle fiber derangement, myofibril dissolution, swollen mitochondrial, adipose degeneration, numerous collagen fibers and fibroblast proliferation were presented in conventional group. For percutaneous group, the erector spinae presented gently inflammatory cell infiltration and not severe fiber necrosis in the early stage. Late morphological change did not show severe adipose infiltration or fibrosis, the constituent ratio and cross-sectional area of muscle fiber were similar to control group. The morphological change of erector spinae has close relationship with the degree of surgical trauma, and the percutaneous surgery can reduce the injury of erector spinae.