The Quantitative Study Of The Biomechanical Properties Of Triceps Surae-Achilles Tendon-Plantar Fascia

Objectives1.To investigate intra-and inter-operator reliability of the stiffness in the gastrocnemius muscle-Achilles tendon complex at different ankle joint angles by using the shear wave elastography(SWE),and to evaluate the correlation between the individual muscle of the gastrocnemius[the medial head of gastrocnemius(MG)and the lateral head of gastrocnemius(LG)]and the regional stiffness of Achilles tendon(AT).2.To investigate the effects of different ankle angles and different knee angles on the stiffness of soleus(SOL),MG,LG,AT and plantar fascial(PF).3.To evaluate the acute effects of static stretching(SS)on the stiffness of MG,LG and AT for different regions,and to examine the differences in range of motion(ROM),the change of AT thickness and fascicle length of MG and LG before and after a SS.4.To investigate the stiffness of the MG and LG in participants with and without plantar fasciitis,and to examine the correlation between the stiffness of gastrocnemius and intensity of pain as well as plantar fascia thickness in patients with plantar fasciitis,and to detect optimal cut-off points of stiffness of the MG and LG in identifying participants with plantar fasciitis.Methods1.Twenty healthy participants(10 males and 10 females)were recruited.Operator A and operator B used SWE to measure the stiffness of AT(0cm,3cm,6cm),MG and LG when the ankle joint at the relaxed position and 90 degree position,the same participants attended at 5 days later,which was repeated according to the previous steps by operator A for the intra-operator investigation.2.Twenty healthy participants(both were male)with the knee flexed 90° or fully extended(0°),the stiffness of the MG,LG,SOL,AT and PF were quantified using the SWE at dorsiflexion 25°(DF25°),0°(neutral position),and plantar flexion 50°(PF50°)of the ankle joint.3.Thirty healthy participants(15 males and 15 females)were recruited,and their AT stiffness,MG stiffness and LG stiffness,muscle fascicle length,AT thickness and active ROM were evaluated before and after 5 minutes of static stretching.4.Twenty patients with clinical diagnosis of plantar fasciitis were recruited and 20 healthy volunteers of the same age and gender were recruited.The SWE was used to quantitatively evaluate the stiffness of MG and LG,and B-mode ultrasonography as used to evaluate the thickness of PF.At the same time,the visual analogue scale(VAS)was used to assess the pain intensity of patients with plantar.fasciitis.Results1.The SWE has higher reliability in quantifying the stiffness of the gastrocnemius-Achilles tendon complex at different ankle angles from moderate to excellent.The intra-tester reliability is good to excellent(ICC:0.77 to 0.96),and the inter-tester reliability is moderate to excellent(ICC:0.66 to 0.96).The minimal detectable change(MDC)of MG,LG and AT are 3.24 kPa,1.72 kPa and 24.49 kPa,respectively.In addition,the stiffness at ATOcm has a significant positive correlation with the stiffness of the MG,and there is no correlation between stiffness of AT and MG at other positions.Furthermore,there is no significant correlation between the stiffness of the LG and the stiffness of the AT.2.The stiffness of the AT and the MG,LG,SOL with the knee fully extended was significantly greater than those performed with the knee flexed 90°(P<0.05).When the knee fully extended,the stiffness of the three regions of PF is less than that of knee flexion at 90°,these only found when the ankle joint was at 0° and 25° dorsiflexion(P<0.05),and when the ankle joint was at 50° plantar flexion,the stiffness of the three regions of PF were not statistically significant(P>0.05).In addition,when the knee fully extended,with the ankle dorsiflexion angle increased,the stiffness of the proximal regions of MG,LG,and PF also increased.When the knee flexed 90°,with the ankle dorsiflexion increased,the stiffness of the proximal regions of LG,SOL,PF and AT also increased When the knee flexed 90°,the stiffness of PF increases significantly when the ankle dorsiflexion at 0° to 25°.When the knee fully extended,the stiffness of LG is greater than that of MG at PF50°,and the stiffness of MG is greater than that of LG at DF25°.No significant difference was found between MG and LG when knee flexed 90°.Regardless of knee rotation,AT stiffness increased in 3 cm>0 cm>6 cm at PF50° and 0°,while AT stiffness increased in 0 cm>3 cm>6 cm at DF25°.For the three regions of PF(proximal,middle,and distal),regardless of the knee and ankle angles,the stiffness increased in proximal region>middle region>distal region.3.The static stretching effects are not homogeneous among different regions of muscle and tendon.The immediate effect of 5 minutes SS is that the stiffness of the MG and LG is significantly decreased,while the stiffness of AT is significantly increased.The ROM of ankle joint increased by 8.02%(P<0.000).Nevertheless,the fascicle length of MG and LG and the thickness of AT were not significant changes.4.When the ankle joint was in the relaxed position,the MG stiffness of patients with plantar fasciitis increased significantly compared with the control group(P<0.05),while the LG did not increase significantly(P>0.05).The PF thickness of patients with plantar fasciitis was significantly larger than that of the control group.In addition,the pain score of patients with plantar fasciitis has a significant correlation with the stiffness of the MG(middle region:r=0.640,P=0.002;distal region:r=0.661,P=0.002),and no correlation was observed between the thickness of the PF and pain(P=0.849).When the ankle joint is in a relaxed position,An optimal cut-off stiffness of MG is 29.08 kPa.Conclusions1.SWE has higher reliability in quantitatively assessing the stiffness of the Achilles tendon and gastrocnemius muscle.Whether the Achilles tendon and gastrocnemius muscles are in a relaxed or stretched state,SWE can help clinicians determine and quantify the stiffness of the Achilles tendon and gastrocnemius muscles,and provide powerful data support for further diagnosis or treatment.In addition,there is a significant positive correlation between ATOcm and stiffness of MG(i.e.,if mg is harder,AT is also harder).2.Changes in knee and ankle joint angles can cause uneven changes in muscle-tendon-plantar fascia stiffness.These insights could be used for providing more intuitive understanding of the relationship between the stiffness of the muscle-tendon-plantar fascia and its function.3.Before static stretching,the stiffness distribution of MG,LG,and AT is always uneven,but after static stretching,the stiffness distribution of MG and LG becomes more uniform,and the stiffness distribution of AT is still uneven.This may enhance our understanding of improved muscle performance and reduced muscle damage after static stretching.Stretching can effectively increase the flexibility of muscle and tendons.In addition,muscle and tendon structures are not related to changes in the stiffness of muscles and tendons.4.The change of muscle stiffness is a good indicator of the clinical condition of patients with plantar fasciitis.A muscle-specific approach is needed for the prevention of plantar fasciitis and rehabilitation of patients with plantar fasciitis.In view of the correlation between MG stiffness and pain index,we suggest that the stiffness of muscles should be used to assess plantar fasciitis and that the treatment program for plantar fasciitis diseases may to be tailored to the MG.