To investigate the effect of hyperbaric oxygen combined with ultrashort wave assisted treatment of Achilles tendon rupture on Achilles tendon healing.

Eighty New Zealand white rabbits were used for creating models by cutting off the Achilles tendon, and all ruptures were sutured by the Kessler method. After being fixed by plaster and ankle-knee fixation for 4 weeks, the rabbits were randomly divided into four groups: hyperbaric oxygen group (group A), ultrashort wave group (group B), hyperbaric oxygen combined with ultra-short wave group (group C), and control group (group D), with 20 rabbits in each group. Groups A and C were treated with hyperbaric oxygen immediately after surgery, twice a day for the first three days and once a day for the next four days, for a total of 7 days. Groups B and C were given ultrashort wave treatment every day for 6 days after operation. Group D was not treated. Ten white rabbits were sacrificed in each group at 4 and 8 weeks after operation. Achilles tendon tissue was taken for HE staining, immunohistochemical staining, and biomechanical detection (maximum tensile length and maximum tensile force). ANOVA was used to compare the results of biomechanical tests at 4 and 8 weeks after operation, and LSD-t test was used for comparisons between two groups.

Biomechanical test results showed that the average maximum tensile force and length of the Achilles tendon in groups A, B, and C at 4 weeks postoperatively were significantly higher than those in group D [maximum tensile force: (276.20±8.16) N, (278.10±7.92) N, and (309.90±9.78) N vs (259.50±4.99) N, t=5.519, 6.280, and 14.513, P<0.001; maximum tensile length: (4.62±0.14) mm, (4.67±0.16) mm, and (5.05±0.17) mm vs (4.18±0.32) mm, t=3.934, 4.136, and 7.563, P=0.001, <0.001, and <0.001]; the two indicators in group C were significantly better than those in groups A and B (maximum tensile force: t=8.366 and 7.989, P<0.001; maximum tensile length: t=6.164 and 5.190, P<0.001). The average maximum tensile force and length of the Achilles tendon in groups A, B, and C at 8 weeks postoperatively were also significantly higher than those in group D [maximum tensile force: (354.60±5.68) N, (355.30±9.62) N, (390.70±7.48) N vs (339.60±5.60) N, t=5.946, 4.461, and 17.286, P<0.001; maximum tensile length: (4.88±0.18) mm, (5.10±0.16) mm, (5.38±0.15) mm vs (4.46±0.23) mm, t=4.578, 7.327, and 10.628, P<0.001]; the two indicators in group C were significantly better than those in groups A and B (maximum tensile force: t=12.150 and 9.187, P<0.001; maximum tensile length: t=6.600 and 3.925, P<0.001 and =0.001). Histologically, it was found that there were a large number of proliferating fibroblasts near the stump of the Achilles tendon, and there were a few inflammatory cells in group C. Although a large number of fibroblasts can be seen in groups A and B, they were fewer than those in group C, but the number of inflammatory cells was larger. In group D, the number of inflammatory cells was significantly more than those of the other three groups, and the growth of fibroblasts lagged significantly behind the other three groups. Immunohistochemical staining showed positive expression of type I collagen fibers, and the number of type I collagen fibers was most abundant in group C, followed sequentially by group B, group A, and group D.

Hyperbaric oxygen combined with ultrashort wave can promote the healing after Achilles tendon rupture, and promote the synthesis of typeⅠcollagen fibers.