Achilles Tendon Cross-sectional Area Research Articles

In Vivo Measurement of Human Achilles Tendon Morphology Using Freehand 3-D Ultrasound

This study investigated the accuracy of phantom volume and length measurements and the reliability of invivo Achilles tendon (AT) volume, length and cross-sectional area measurements obtained using freehand 3-D ultrasound. Participants (n=13) were scanned on consecutive days under active and passive loading conditions. Invivo AT length was evaluated using a two-point method and an approach that accounted for AT curvature (centroid method). Three-dimensional ultrasound provided accurate measures of phantom volume and length (mean difference=0.05mL and 0.2mm, respectively) and reliable invivo measures of AT volume, length and average cross-sectional area, with all intra-class correlations coefficients greater than 0.98. The mean minimally detectable changes for invivo AT volume, two-point length and centroid length were 0.2mL, 1.5mm and 2.0mm, respectively. Two-point AT length underestimated centroid AT length by 0.7mm, suggesting that the effect of curvature on invivo AT length is negligible.

Effects of Plyometric Training on Achilles Tendon Properties and Shuttle Running During a Simulated Cricket Batting Innings

The aim of this study was to determine whether intermittent shuttle running times (during a prolonged, simulated cricket batting innings) and Achilles tendon properties were affected by 8 weeks of plyometric training (PLYO, n = 7) or normal preseason (control [CON], n = 8). Turn (5-0-5-m agility) and 5-m sprint times were assessed using timing gates. Achilles tendon properties were determined using dynamometry, ultrasonography, and musculoskeletal geometry. Countermovement and squat jump heights were also assessed before and after training. Mean 5-0-5-m turn time did not significantly change in PLYO or CON (pre vs. post: 2.25 ± 0.08 vs. 2.22 ± 0.07 and 2.26 ± 0.06 vs. 2.25 ± 0.08 seconds, respectively). Mean 5-m sprint time did not significantly change in PLYO or CON (pre vs. post: 0.85 ± 0.02 vs. 0.84 ± 0.02 and 0.85 ± 0.03 vs. 0.85 ± 0.02 seconds, respectively). However, inferences from the smallest worthwhile change suggested that PLYO had a 51-72% chance of positive effects but only 6-15% chance of detrimental effects on shuttle running times. Jump heights only increased in PLYO (9.1-11.0%, p < 0.050). Achilles tendon mechanical properties (force, stiffness, elastic energy, strain, modulus) did not change in PLYO or CON. However, Achilles tendon cross-sectional area increased in PLYO (pre vs. post: 70 ± 7 vs. 79 ± 8 mm, p < 0.01) but not CON (77 ± 4 vs. 77 ± 5 mm, p > 0.050). In conclusion, plyometric training had possible benefits on intermittent shuttle running times and improved jump performance. Also, plyometric training increased tendon cross-sectional area, but further investigation is required to determine whether this translates to decreased injury risk.

In Vivo Evaluations of Morphologic Changes of Gastrocnemius Muscle Fascicles and Achilles Tendon in Children with Cerebral Palsy

The Achilles tendon plays an important role in soleus and gastrocnemius muscle functions, including proper muscle force transmission and movement generation. However, few studies have examined concurrent changes of tendon and muscle properties in neurologic disorders. The objective of this study was to investigate the morphologic characteristics of both the calf muscle fascicles and the Achilles tendon in children with cerebral palsy (CP). A cross-sectional study was planned, and 12 children with CP and 11 typically developing children participated in this study. For both groups, B-mode ultrasonography was used to evaluate the architecture of the medial gastrocnemius muscle, including fascicle length and pennation angle at various ankle (20, 10, and 0 degrees plantar flexion and 10 degrees dorsiflexion) and knee (full extension and 90 degrees flexion) positions. The length and cross-sectional area of the Achilles tendon were also evaluated using ultrasonography. For both CP and control groups, muscle fascicle length, pennation angle, and Achilles tendon length and cross-sectional area varied with ankle and knee positions systematically. Compared with controls, children with CP had shorter muscle fascicles across the tested ankle range of motion (P ≤ 0.003), longer Achilles tendon (P = 0.001), and smaller cross-sectional area of the Achilles tendon (P = 0.003). The changes in Achilles tendon properties could be a result of adaptation to calf muscle fascicle shortening and stiffening, which may affect performance of the muscles. A better understanding of the interactions between calf muscle fascicles and Achilles tendon in children with CP may help treat the pathologic changes more effectively.

Mechanical properties of the human Achilles tendon, in vivo

Background Ultrasonography has been widely applied for in vivo measurements of tendon mechanical properties. Assessments of human Achilles tendon mechanical properties have received great interest. Achilles tendon injuries predominantly occur in the tendon region between the Achilles-soleus myotendinous junction and Achilles-calcaneus osteotendinous junction i.e. in the free Achilles tendon. However, there has been no adequate ultrasound based method for quantifying the mechanical properties of the free human Achilles tendon. This study aimed to: 1) examine the mechanical properties of the free human Achilles tendon in vivo by the use of ultrasonography and 2) assess the between-day reproducibility of these measurements. Methods Ten male subjects had the Achilles tendon moment arm length, Achilles tendon cross sectional area and free Achilles tendon length determined. All subjects performed isometric plantarflexion ramp contractions to assess between-day reproducibility on two separate days. Simultaneous ultrasonography based measurements of Achilles-soleus myotendinous junction and Achilles-calcaneus osteotendinous junction displacement together with Achilles tendon force estimates yielded free Achilles tendon mechanical properties. Findings Free Achilles tendon maximal force, deformation and stiffness were 1924 (SD 229) N, 2.2 (SD 0.6) mm and 2622 (SD 534) N/mm on day 1. For between-day reproducibility there were no significant differences between days for free Achilles tendon mechanical properties. The between-day correlation coefficient and typical error percent were 0.81 and 5.3% for maximal Achilles tendon force, 0.85 and 11.8% for maximal Achilles tendon deformation and 0.84 and 8.8% for Achilles tendon stiffness respectively. Last, osteotendinous junction proximal displacement on average contributed with 71 (SD 12) % of proximal myotendinous junction displacement. Interpretation This study, for the first time, presents an ultrasonography based in vivo method for measurement of free AT mechanical properties. The method is applicable for evaluation of free human Achilles tendon mechanical properties in relation to training, injury and rehabilitation.

Effects of plyometric training on both active and passive parts of the plantarflexors series elastic component stiffness of muscle–tendon complex

The aims of this study were to determine the effects of plyometric training on both active and passive parts of the series elastic component (SEC) stiffness, and on geometrical parameters [i.e., muscle architecture, muscle and tendon cross-sectional area (CSA)] of the plantarflexors muscle-tendon complex to assess possible specific adaptations of the elastic properties. Nineteen subjects were randomly divided into a trained group and a control group. Active and passive components of the SEC stiffness were determined using a fast stretch during submaximal voluntary isometric plantarflexor activity. Geometrical parameters of the triceps surae muscles and the Achilles tendon were determined using ultrasonography. A significant increase in the passive component of the SEC stiffness was found (p < 0.05). In contrast, a significant decrease in the active part of the SEC stiffness was observed (p < 0.05). No significant changes in plantarflexor muscles CSA, architecture and Achilles tendon CSA were seen (p > 0.05). Thus, plyometric training led to specific adaptations within each part of the SEC. Theses adaptations could increase both the efficiency of the energy storage-recoil process and muscular tension transmission leading to an increase in jump performances.

Plyometric training effects on Achilles tendon stiffness and dissipative properties

The aim of this study was to determine the effects of 14 wk of plyometric training on mechanical properties of the Achilles tendon. Nineteen subjects were randomly assigned to trained or control group. Cross-sectional area (CSA), stiffness, and dissipation coefficient of the Achilles tendon were measured before and after the training period. In the trained group, a decrease in dissipation coefficient (-35.0%; P<0.05) and an upward trend in stiffness (+24.1%) of the Achilles tendon was found, without any changes in Achilles tendon CSA (P>0.05). Plyometric training enhances the muscular tension transmission mainly through a reduction in energy dissipated by the tendon. The lack of changes in the Achilles tendon CSA indicates that changes in mechanical properties would mainly result from a qualitative change in tendinous tissues rather than from changes in the geometry of the Achilles tendon.

Combination of hormone replacement therapy and high physical activity is associated with differences in Achilles tendon size in monozygotic female twin pairs

Estrogen concentration has been suggested to play a role in tendon abnormalities and injury. In physically active postmenopausal women, hormone replacement therapy (HRT) has been suggested to decrease tendon diameter. We hypothesized that HRT use and physical activity are associated with Achilles tendon size and tissue structure. The study applied cotwin analysis of fourteen 54- to 62-yr-old identical female twin pairs with current discordance for HRT use for an average of 7 yr. Achilles tendon thickness and cross-sectional areas were determined by ultrasonography, and tendon structural organization was analyzed from the images using linear discriminant analysis (LDA). Maximal voluntary and twitch torques from plantar flexor muscles were measured. Serum levels of estradiol, estrone, testosterone, and sex hormone binding globulin were analyzed. Total daily metabolic equivalent score (MET-h/day) was calculated from physical activity questionnaires. Results showed that, in five physically active (MET > 4) pairs, the cotwins receiving HRT had greater estradiol level (P = 0.043) and smaller tendon cross-sectional area than their sisters (63 vs. 71 mm(2), P = 0.043). Among all pairs, Achilles tendon thickness and cross-sectional area did not significantly differ between HRT using and nonusing twin sisters. Intrapair correlation for Achilles tendon thickness was high, despite HRT use discordance (r = 0.84, P < 0.001). LDA distinguished different tendon structure only from two of six examined twin pairs who had a similar level of physical activity. In conclusion, the effect of HRT on Achilles tendon characteristics independent of genetic confounding may be present only in the presence of sufficient physical activity. In physically active twin pairs, the higher level of estrogen seems to be associated with smaller tendon size.

Short-term immobilization and recovery affect skeletal muscle but not collagen tissue turnover in humans

Not much is known about the effects of immobilization and subsequent recovery on tendon connective tissue. In the present study, healthy young men had their nondominant leg immobilized for a 2-wk period, followed by a recovery period of the same length. Immobilization resulted in a mean decrease of 6% (5,413 to 5,077 mm(2)) in cross-sectional area (CSA) of the triceps surae muscles and a mean decrease of 9% (261 to 238 N.m) in strength of the immobilized calf muscles. Two weeks of recovery resulted in a 6% increased in CSA (to 5,367 mm(2)), whereas strength remained suppressed (240 N.m). No difference in Achilles tendon CSA was detected between the two legs at any time point. Local tendon collagen synthesis, measured as the peritendinous concentrations of PINP (NH(2)-terminal propeptide of type I collagen; indirect marker for collagen synthesis), was unchanged after 2 wk of immobilization. However, peritendinous levels of PINP were significantly elevated in the immobilized leg (15 to 139 ng/ml) following 2 wk of remobilization compared with preimmobilization levels. In contradiction hereto, systemic concentrations of PINP remained unchanged throughout the study. Immobilization reduced muscle size and strength, while tendon size and collagen turnover were unchanged. While recovery resulted in an increase in muscle size, strength was unchanged. No significant difference in tendon size could be detected between the two legs after 2 wk of recovery, although collagen synthesis was increased in the previously immobilized leg. Thus 2 wk of immobilization are sufficient to induce significant changes in muscle tissue, whereas tendon tissue seems to be more resistant to short-term immobilization.

Effects of long-term immobilization and recovery on human triceps surae and collagen turnover in the Achilles tendon in patients with healing ankle fracture

The aim of the present study was to analyze how human tendon connective tissue responds to an approximately 7-wk period of immobilization and a remobilization period of a similar length, in patients with unilateral ankle fracture, which is currently unknown. Calf muscle cross-sectional area (CSA) decreased by 15% (5,316 to 4,517 mm2) and strength by 54% (239 to 110 N.m) in the immobilized leg after 7 wk. During the 7-wk remobilization, the CSA increased by 9% (to 4,943 mm2) and strength by 37% (to 176 Nm). Achilles tendon CSA did not change significantly during either immobilization or remobilization. Local collagen turnover was measured as the peritendinous concentrations of NH2-terminal propeptide of type I collagen (PINP) and COOH-terminal telopeptide region of type I collagen (ICTP), markers thought to be indexes of type I collagen synthesis and degradation, respectively. Both markers were increased (PINP: 257 vs. 56 ng/ml; ICTP: 9.8 vs. 2.1 microg/l) in the immobilized leg compared with the control leg after the 7 wk of immobilization, and levels decreased again in the immobilized leg during the recovery period (PINP: 103 vs. 44 ng/ml; ICTP: 4.2 vs. 1.9 microg/l). A significant reduction in calf muscle CSA and strength was found in relation to 7 wk of immobilization. Immobilization increased both collagen synthesis and degradation in tendon near tissue. However, it cannot be excluded that the facture of the ankle in close proximity could have affected these data. Remobilization increased muscle size and strength and tendon synthesis and degradation decreased to baseline levels. These dynamic changes in tendon connective tissue turnover were not associated with macroscopic changes in tendon size.

Matrix loaded and unloaded: can tendons grow when exercised?

this question is pretty naive, in that we all know that during overall growth and development connective tissue structures such as bone, ligaments, cartilage, and tendons will enhance their size to match the overall growth of the body ([6][1]). Several animal studies have documented that intense

Sonographic Measurement of Achilles Tendons in Asymptomatic Subjects

This study was undertaken to evaluate the thickness, cross-sectional area, and length of Achilles tendons in asymptomatic subjects of different age groups and heights and between dominant and nondominant ankles. High-resolution sonographic examinations of Achilles tendons were performed in 40 healthy subjects (14 men and 26 women). The subjects were categorized into 4 age groups: (1) 20 to 29 years, (2) 30 to 39 years, (3) 40 to 49 years, and (4) 50 years or older. The thickness, cross-sectional area, and length of the Achilles tendons of both ankles were measured. All Achilles tendons were measured with the ankle in a relaxed, neutral position. There was no significant difference in the thickness and length of Achilles tendons among subjects of different age groups (P>.05). The Achilles tendon cross-sectional area of subjects 50 years or older was significantly larger than that of subjects in the younger age groups (P<.05). There was a positive correlation between the height of the subjects and the length, thickness, and cross-sectional area of the Achilles tendons; however, the correlation coefficient was low (r=0.07-0.28; P>.05). Dominance of ankles did not affect the thickness and length of the Achilles tendons, whereas the cross-sectional area of the tendons was significantly larger in the dominant ankles (P<.05). Sonography is a useful imaging tool in the evaluation of Achilles tendons. Normal variations of the tendon morphologic characteristics should be considered in the clinical diagnosis.

Sonographic evaluation of the size of achilles tendon: the effect of exercise and dominance of the ankle

This study was undertaken to measure and compare the thickness and cross-sectional area of the Achilles tendon between frequent- and infrequent-exercise subjects, and between the dominant and nondominant ankles in an asymptomatic Chinese population. Interobserver variability in the measurement of the size of Achilles tendon was also evaluated. High-resolution ultrasound (US) examination of Achilles tendons was performed in 40 healthy subjects (20 who frequently exercised, had exercise at least 3 days per week and at least 2 h per session; and 20 who infrequently exercised); their age range was 19 to 25 years. The thickness and cross-sectional area of the Achilles tendons were measured in a transverse scan at the level of medial malleolus. For each subject, the Achilles tendons were measured by five operators to evaluate the interobserver variability in the measurements. The mean thickness and cross-sectional areas of the Achilles tendon in a healthy Chinese population are 5.23 mm 2 and 56.91 mm 2 2, respectively. The mean thickness of the Achilles tendon of frequent-exercise subjects (dominant ankle 5.43 mm, nondominant ankle 5.38 mm) was significantly greater than that of infrequent-exercise subjects (dominant ankle 5.08 mm, nondominant ankle 5.04 mm) ( p < 0.05). The cross-sectional area of the tendons was also larger in frequent-exercise subjects but, whereas a significant result was found in dominant ankles (frequent-exercise subjects 60.46 mm 2 2, infrequent-exercise subjects 54.71 mm 2 2) ( p < 0.05), this was not the case for the nondominant ankles (frequent-exercise subjects 57.09 mm 2 2, infrequent-exercise subjects 55.4 mm 2 2) ( p > 0.05). In both frequent- and infrequent-exercise subjects, there was no significant difference in the mean thickness and cross-sectional area of Achilles tendon between dominant and nondominant ankles ( p > 0.05). There was a high reproducibility in the sonographic measurement of the thickness (68%) and cross-sectional area (81%) of Achilles tendons. Results suggested that exercise would cause increase in the thickness and cross-sectional area of Achilles tendon. Interobserver variability is not significant in the sonographic measurement of Achilles tendons. (E-mail: ormying@polyu.edu.hk)

Increased Cross-sectional Area and Reduced Tensile Stress of the Achilles Tendon in Elderly Compared With Young Women

The Achilles tendon cross-sectional area (CSA), tensile force, and stress during an isometric contraction were examined in healthy young (n = 9, age = 29 +/- 1 years, mean +/- SEM) and elderly (n = 10, 79 +/- 2 years) women. CSA area was obtained with magnetic resonance imaging 3 cm proximal to the insertion, and tendon force was obtained from the isometric ankle moment. The moment of force about the ankle joint was greater in young women (95 +/- 17 N m) than in elderly women (51 +/- 5 N m; p <.05). The Achilles tendon CSA was significantly greater in elderly women (56.3 +/- 3.0 mm(2)) than in young women (46.0 +/- 1.9 mm(2); p <.01). These data show that young women can exert a greater force than elderly women on the Achilles tendon during voluntary contraction, although elderly women have an increased (22%) tendon CSA, and a lower tendon force than young women. The greater tendon size combines to lower the stress on the tendon markedly, which may reduce the risk of injury to the tendon.

CROSS-SECTIONAL AREA OF THE ACHILLES TENDON IN YOUNG AND ELDERLY WOMEN

The aging process is reportedly associated with connective tissue changes although no data exists to substantiate such changes in elderly women. The present study investigated the effect of age on the cross - sectional area (CSA) of the Achilles tendon. Methods: The CSA was obtained with MRI in young (Y) healthy untrained women (n = 9, age = 29 ± 0.7 yrs (mean ± SE)) and elderly (E) healthy untrained women (n = 10, 79.4 ± 1.9 yrs). Mean CSA was obtained from 3 measures 3 cm proximal to the Achilles tendon insertion. CV for the measures was 3.4%. Achilles tendon force was obtained from maximal isometric ankle moment and moment arm data from MRI. Pearson correlation coefficients and unpaired t-tests were used for statistical evaluation. Results: (mean ± SE) Y and E did not differ in height (Y: 167 ± 3 cm, E: 163 ± 3 cm) or weight (Y: 71.3 ± 4.4 kg, E: 62.1 ± 3.6 kg). Achilles tendon CSA was greater in E (56.3+3.0 mm2) compared to Y (46.0+1.9 mm2), P < 0.01. Tendon force was greater in Y (1930 ± 393 N) compared to E (982 ± 107 N), P < 0.05. Tendon CSA was correlated to weight (r = 0.67, P < 0.05), and approached a significant relationship to tendon force (r = 0.65, P = 0.056) for Y, but not E. Conclusion: These data suggest that Achilles tendon CSA increases with age. Further, it appears that body weight and maximal strength (tendon force), in part, influences Achilles tendon CSA in young adults.

Evaluation of the aortic root by MRI: insights from patients with homozygous familial hypercholesterolemia.

In homozygous familial hypercholesterolemia (HFH), the aortic root is prone to develop atherosclerotic plaque at an early age. However, the aortic wall and plaque have not yet been assessed in this condition by MRI. We evaluated the aortic root by use of MRI in 17 HFH patients and 12 normal control subjects in a prospective, blinded, controlled study. Morphological assessment of the aortic root was done with spin-echo and gradient-echo MRI scanning. Comparisons were made with a number of measures of disease severity, including cholesterol-year score, calcium score on electron-beam CT (EBCT), and size of Achilles tendon xanthomas. Atherosclerotic plaque, visible on fat-suppressed images but never on water-suppressed images, was present in 9 HFH patients (53%). Supravalvular aortic stenosis was present in 7 patients with HFH (41%). Maximum supravalvular aortic wall thickness was significantly greater and OD and lumen cross-sectional area (CSA) were smaller in patients than in control subjects (P=0.006, 0.0005, and 0.06, respectively). Maximum wall thickness was associated with a greater calcium score on electron-beam CT (P=0.02). Although the cumulative exposure of the aortic root to cholesterol (the cholesterol-year score) was significantly correlated with the Achilles tendon CSA and vascular calcification, this score did not correlate with the wall thickness or aortic CSA. This study not only demonstrates the utility of MRI for detecting and characterizing aortic root atherosclerotic plaque and supravalvular aortic stenosis in HFH patients but also suggests that the LDL receptor plays a direct or indirect role in aortic mural development and vascular growth.

Relation of cholesterol-year score to severity of calcific atherosclerosis and tissue deposition in homozygous familial hypercholesterolemia

The high concentrations of low-density lipoprotein cholesterol in plasma lead to accelerated atherosclerosis in patients homozygous for familial hypercholesterolemia (FH). We addressed the hypothesis that lipid deposition in the arterial vasculahire and in nonvascular tissues in these patients correlates with both the duration and severity of their hypercholesterolemia. The severity of calcific atherosclerosis was defined by calcification scores and a calcified volume determined by electron beam tomography. The extent of tendinous xanthomatosis was quantitated by computed tomography. A cholesterolyear score was calculated based on the age and the yearly mean serum cholesterol concentration of each patient. Seventeen patients homozygous for FH were followed up. The average total cholesterol concentration in the study group was 780 ± 231 mg/dl (20.2 mmol/L), and the cholesterol-year scores ranged from 2,172 mg-year/dl (56 mmol-year/L) to 32,260 mg-year/dl (834 mmol-year/L). Achilles tendon width (r = 0.86) and cross-sectional area (r = 0.81; both p < 0.001) were best correlated with the cholesterol-year score. In addition, the coronary (r = 0.61; p < 0.05), ostial (r = 0.45; p < 0.05), and total (r = 0.77; p < 0.001) calcification atherosclerosis scores all were best correlated with the cholesterol-year score. Calcific atherosclerosis was not observed in these patients until the cholesterol-year score exceeded 10,000 mg-year/dl (260 mmol-year/ L). These findings establish a direct association of cholesterol-year with extravascular lipid deposition in tissues of patients with FH. The cholesterol-year score may be useful in defining the risk of atherosclerosis in patients with more common forms of hypercholesterolemia.