In-vivo strain measurement of surgically repaired achilles tendon under isometric contraction using real-time ultrasonography

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In-vivo strain measurement of surgically repaired achilles tendon under isometric contraction using real-time ultrasonography

 

Author: Chan, Yim-ling Jolinna
Title: In-vivo strain measurement of surgically repaired achilles tendon under isometric contraction using real-time ultrasonography
Degree: M.Sc.
Year: 2004
Subject: Hong Kong Polytechnic University -- Dissertations
Achilles tendon -- Wounds and injuries -- Treatment
Ultrasonic imaging
Department: Jockey Club Rehabilitation Engineering Centre
Pages: x, 78 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1772698
URI: http://theses.lib.polyu.edu.hk/handle/200/1974
Abstract: Since Achilles tendon is subjected to great stress during human locomotion, their mechanical properties are of great interests especially after rupture. During rehabilitation, the type and intensity of exercise are important and crucial so as to prevent any damage to the repaired tendon. Investigations on tendon biomechanics are usually limited by biomechanical testing equipment especially for in-vivo conditions. Therapists usually base on clinical symptoms such as swelling, signs of inflammation to determine whether the given exercise is appropriate or not. Not much information has been reported in literatures on the strain and stress under exercise conditions, which provide guidelines to therapist to plan treatments. Recently, ultrasonic measurement of tissue elasticity in-vivo has been widely used for various tissues. In this prospective randomized study, ultrasound imaging was used to measure the strains of Achilles tendons under isometric contraction in-vivo. Our aim is to investigate the differences between the strains of the healthy and repaired Achilles tendons so as to obtain useful information for providing better physiotherapy schemes during the rehabilitation stage. A portable ultrasound scanner (Sonosite 180 plus) with a linear-array probe (7.5 Mhz) was used to study the strains of the repaired Achilles tendon during isometric contractions. Six male subjects with age ranged from 28 to 51 were recruited and their levels of rupture range were 2 cm to 7 cm from the insertion of Achilles tendon. They were tested 12.8 +-1.3 weeks after operation. Their healthy legs were used as controls. In addition, three healthy male subjects were recruited so as to find any difference between the dominant and non-dominant legs. Ultrasound images were obtained along the Achilles tendon at the level of rupture site in-vivo under isometric contraction using Cybex 6000, which also recorded the torque of gastrocnemius-soleus complex simultaneously. The displacement of the selected part of the tendon was extracted from the ultrasound images using a program for dynamic ultrasound signal and image analysis. Results were compared with the good side of the same subject. Results demonstrated that the strain of the repaired side was less than the normal side for all subjects under the same torque condition. The strain difference ranged from 0.8% to 35%. Results showed that the strain of affected side was significantly smaller than that of the good side (p=0.017). In addition, porcine Achilles tendons were measured in-vitro for the validation of the technique. The porcine tendon was fixated by a modified caliper with pins inserted as the marker for ultrasound measurement. Stain was placed on the same points for tracking the displacements on the tendon surface using a digital video simultaneously. The validation results showed there was a good correlation between the displacements measured by the ultrasound and optical methods (r2 = 0.903 +-0.028). The results of the present study demonstrated that ultrasound imaging could be used to measure the strains of Achilles tendons under isometric contraction in-vivo. Further studies are suggested to investigate the mechanical properties of repaired Achilles tendon at different range of movement of ankle joint under isometric contraction, or under different exercise conditions such as isotonic exercises. Moreover, the uninvolved part of repaired Achilles tendon should be further investigated so as to provide thorough information on the whole tendon.

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