Abstract: BACKGROUND: Arc edge needle-scalpel therapy has a significant clinical effect in the treatment of frozen shoulder; however, there is still a lack of basic research on the therapeutic mechanism.
OBJECTIVE: To observe the effect of arc edge needle-scalpel therapy on serum inflammatory factors and the morphology and structure of tendon and synovium in a rabbit frozen shoulder model, and to explore the possible mechanism of arc-edge needle knife therapy in the intervention of frozen shoulder.  
METHODS: Forty-eight male New Zealand rabbits were randomly divided into blank group (n=8), model group (n=8), electroacupuncture group (n=8), and arc edge needle-scalpel groups I, II, III (n=8 per group). The rabbit frozen shoulder model was made by the method of continuous mechanical strain and ice compress in all groups except for the blank group. After the establishment of the model, the electroacupuncture group was treated with electroacupuncture at Jianyu and Quchi, 3 times a week for 4 continuous weeks. Arc edge needle-scalpel groups I, II, III were treated with arc edge needle-scalpel at internodular groove, the beginning of teres major, and junction between supraspinatus tendon and muscle belly, once a week: four sessions in arc edge needle-scalpel group III, first two sessions in arc edge needle-scalpel group I, and latter two sessions in arc edge needle-scalpel group II. At 3 days after intervention termination, the width of effusion in the posterior recess of the right shoulder joint was detected by ultrasound, the contents of interleukin-1β, NLRP3 and caspase-1 in serum were detected by ELISA method, the histomorphology of long head tendon and synovium of biceps brachii was observed using hematoxylin-eosin and Masson staining, and the expression of interleukin-1β protein in synovium was observed by immunohistochemical method. The study was approved by the Animal Experimental Ethics Committee (approval No. 191213015).
RESULTS AND CONCLUSION: Compared with the blank group, after modeling, a large amount of fluid was observed on the posterior recess side of the shoulder cavity in the model group. After intervention, the width of effusion in the arc edge needle-scalpel groups I and III was significantly smaller than that in the electroacupuncture group and arc edge needle-scalpel group II. Compared with the model group, the levels of interleukin-1β, NLRP3 and caspase-1 in the serum were significantly lower in the electroacupuncture group and arc edge needle-scalpel groups I, II, III (P < 0.01). The levels of interleukin-1 β and NLRP3 in the serum of the arc edge needle-scalpel group I were significantly lower than those of the arc edge needle-scalpel group II (P < 0.05). Under hematoxylin-eosin and Masson staining, electroacupuncture group and arc edge needle-scalpel group II showed partial tendon fiber hyperplasia and rupture, synovium thickening and fibrosis; arc edge needle-scalpel groups I and III showed reduced tendon fiber proliferation and synovium thickening, and improved pathological state of tissue inflammation and fibrosis. Compared with the model group, the expression of interleukin-1β in synovium was significantly lowered in the electroacupuncture group and arc edge needle-scalpel groups I, II, III (P < 0.01), while the expression of interleukin-1β in synovium in the arc edge needle-scalpel groups I, III was significantly lower than that in the arc edge needle-scalpel groups II (P < 0.01). To conclude, arc edge needle-scalpel therapy can reduce the levels of interleukin-1β, NLRP3 and caspase-1 in serum and the expression of interleukin-1β protein in synovium, and promote the repair of damaged tissue in the rabbit frozen shoulder model, so as to inhibit local aseptic inflammation of the frozen shoulder.

Key words: frozen shoulder, arc edge needle-scalpel, interleukin-1β, inflammatory body, rabbit, animal model