Objective

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To explore the mechanism of mechanical adjustment in the treatment of lateral ankle sprain by rotating， pulling and poking.

Methods

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The CT tomographic image of the ankle below the distal 1/3 of the tibia in one case of acute lateral ankle sprain was collected， and the three-dimensional finite element model of the ankle was constructed by Abaqus 6.13 and Mimics 10.0 software. Rotating， pulling and poking manipulation were performed， once every other day for two weeks. The mechanical data of in vivo tests were collected and transformed before the manipulation， after initial treatment， and after 2-week treatment， and the transformed mechanical parameters were substituted into the finite element model to analyze the stress peak value and stress distribution area of the articular surface under the four ankle joint working conditions （plantar flexion， dorsiflexion， eversion， inversion） at three time points in the treatment of lateral ankle sprain by rotating-pulling-poking manipulation.

Results

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The results of in vivo tests showed that with the passage of time， the maximum motion angle of the ankle joint increased gradually at three time points under the four working conditions， and that was 26.5°， 27.5°， and 31.7° before treatment， after initial treatment， and after 2-week treatment under the condition of dorsiflexion， respectively. The finite element loading test showed that the stress peak value and stress distribution area of talus fibular surface and talus tibial surface gradually increased with the passage of time at three time points under the four working conditions of ankle joints. Under dorsiflexion condition， the stress peak value and stress distribution area of talus tibial surface were 49.5MPa and 131.04 mm

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respectively， while those were 50.0 MPa and 146.88 mm

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after initial treatment， and 52.4 MPa and 218.88 mm

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after 2-week treatment； for talus fibular surface， the stress peak value and stress distribution area were 26.5 MPa and 226.08 mm

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before treatment， 27.5 MPa and 237.60 mm

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after initial treatment， and 32.5 MPa and 269.28 mm

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after 2-week treatment， respectively.

Conclusion

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Rotating-pulling-poking manipulation can effectively improve the stress distribution on the articular surface of the ankle point for sprained lateral ankle joint， so that the load-bearing capacity of the ankle joint surface is gradually raised， and the stress distribution is gradually distributed evently， thereby improving the symptoms of limited ankle motion after sprain. This may be one of the mechanism of mechanical adjustment in the treatment of lateral ankle sprain by rotating-pulling-poking manipulation.