[Effect of acupotomy intervention on the morphology and ultrastructure of rectus femoris muscle in rabbits with knee osteoarthritis].

Objective: To observe the effect of acupotomy on the morphology and ultrastructure of rectus femoris muscle in rabbits with knee osteoarthritis and to reveal the possible therapeutic mechanism involved in the effect of acupotomology on the treatment of knee osteoarthritis(KOA).

Methods: Twenty-four male New Zealand rabbits aged 6 months and weighed (2.0±0.5) kg were randomly divided into blank group, model group and acupotomy group, 8 rabbits in each group. KOA model was established by modified Videman method with left hind limb extended plaster immobility for 6 weeks. In acupotomy group, the transfascial focal points of quadriceps femoris muscle were released by acupotomy under the guidance of Jingjin theory for 4 times and once a week, and the treatment points include Hedingci, Binwaixia, Binneixia. Blank group and model group were fed normally without intervention. One week after the end of the intervention, the pennation angle(PA), muscle thickness(MT), cross-sectional area(CSA) and strain ratio(SR) of rectus femoris were measured by ultrasound. HE staining was used to observe the changes of the tissue morphology, the number of muscle fibers and the average area of muscle fibers. The myofibril of rectus femoris, sarcomere and myofilament were observed by transmission electron microscope.

Results: The PA of rectus femoris muscle in the blank group was (9.05±0.21)°. The MT was(1.09±0.09) cm and the CSA was(1.30±0.01) cm. The PA of rectus femoris muscle in the model group was (3.06±0.15)°. The MT was (0.71±0.02) cm and the CSA was(0.77±0.02) cm. The PA of rectus femoris muscle in the acupotomy group was (6.94±0.28)°. The MT was (0.80±0.05) cm and the CSA was(0.94±0.03) cm. The muscle PA, MT and CSA of rectus femoris in the model group were significantly smaller than those in the blank group (<0.05). Those in acupotomy group were significantly increased compared with those in model group (<0.05). The SR of rectus femoris muscle was 1.19±0.02 in the blank group, 3.50±0.05 in the model group and 1.99±0.07 in the acupotomy group. The elastic SR of the model group was significantly higher than that of the blank group (<0.05). These in acupotomy group was significantly lower than that in model group(<0.05). The results of HE staining showed:in blank group, the fascicles of rectus femoris were arranged neatly, the number of beam of muscle fibers within the fixed visual field was 94.38±3.50 and the average CSA was(0.75±0.22) mm. In model group, the fascicles of rectus femoris with different sizes were disorganized with a small amount of inflammatory cell infiltration, the number of beam of muscle fibers within the fixed visual field was 196.63±2.62 and the average CSA was(0.26±0.03) mm. Compared to the blank group, a significant increase in the number of muscle fibers in the fixed field in the model group (<0.05) and the average CSA decreased significantly(<0.05). In acupotomy group, the rectus femoris fascicles in the acupotomy group tended to be arranged in a more orderly manner, with the inflammatory cells decreased, the number of beam of muscle fibers within the fixed visual field was 132.88±4.61 and the average CSA was(0.70±0.07) mm. Compared to the model group, a significant decrease in the number of muscle fibers in the fixed field in the model group(<0.05) and the average CSA increased significantly(<0.05). The results of transmission electron microscope showed:compared with the blank group, the overall arrangement of the myofibrils of the rectus femoris in the model group was less structured. There was fracture between the muscle fibers and the sarcomere, the myofilaments were disordered, and the fracture of the Z line was discontinuous. Compared with the model group, the myofibrillar texture of rectus femoris in acupotomy group was clearer, and the Z line was more continuous.

Conclusion: Based on the jingjin theory, the release of quadriceps femoris by acupotomy can effectively improve the morphology and structure of rectus femoris, and promote the repair and reconstruction of chronic skeletal muscle injury in rabbits with KOA, which may be one of the mechanisms of acupotomy in the treatment of KOA.