Developing and using fast shear wave elastography to quantify physiologically-relevant tendon forces

Evaluation of the Mechanical Behavior of the Patellar and Semitendinosus Tendons Using Supersonic Shear-wave Imaging (SSI) Elastography and Tensile Tests

Objective  To analyze the mechanical properties of the patellar (PT) and semitendinosus (ST) tendons from fresh-frozen human cadavers from a tissue bank using supersonic shear-wave imaging (SSI) elastography and tensile tests. Methods  We tested seven PT and five ST samples on a traction machine and performed their simultaneous assessment through SSI. The measurements enabled the comparison of the mechanical behavior of the tendons using the stress x strain curve and shear modulus (μ) at rest. In addition, we analyzed the stress x μ relationship under tension and tested the relationship between these parameters. The statistical analysis of the results used unpaired t -tests with Welch correction, the Pearson correlation, and linear regression for the Young modulus (E) estimation. Results  The μ values for the PT and ST at rest were of 58.86 ± 5.226 kPa and 124.3 ± 7.231 kPa respectively, and this difference was statistically significant. The correlation coefficient between stress and μ for the PT and ST was very strong. The calculated E for the PT and ST was of 19.97 kPa and 124.8 kPa respectively, with a statistically significant difference. Conclusion  The ST was stiffer than the PT in the traction tests and SSI evaluations. The μ value was directly related to the stress imposed on the tendon. Clinical relevance  The present is an evaluation of the mechanical properties of the tendons most used as grafts in knee ligament reconstruction surgeries.

Shear wave elastography of transverse carpal ligament increased with simulated carpal tunnel pressure

BACKGROUND

Elevation of carpal tunnel pressure is known to be associated with carpal tunnel syndrome. This study aimed to correlate the shear wave elastography in the transverse carpal ligament (TCL) with carpal tunnel pressures using a cadaveric model.

METHODS

Eight human cadaveric hands were dissected to evacuate the tunnels. A medical balloon was inserted into each tunnel and connected to a pressure regulator to simulate tunnel pressure in the range of 0-210 mmHg with an increment of 30 mmHg. Shear wave velocity and modulus was measure in the middle of TCL.

RESULTS

SWV and SWE were significantly dependent on the pressure levels (p < 0.001), and positively correlated to the tunnel pressure (SWV: R = 0.997, p < 0.001; SWE: R = 0.996, p < 0.001). Regression analyses showed linear relationship SWV and pressure (SWV = 4.359 + 0.0263 * Pressure, R2 = 0.994) and between SWE and pressure (SWE = 48.927 + 1.248 * Pressure, R2 = 0.996).

CONCLUSION

The study indicated that SWV and SWE in the TCL increased linearly as the tunnel pressure increased within the current pressure range. The findings suggested that SWV/SWE in the TCL has the potential for prediction of tunnel pressure and diagnosis of carpal tunnel syndrome.

The Fate of the Shoulder Post Rotator Cuff Repair: Biomechanical Properties of the Supraspinatus Tendon and Surrounding Structures

The study aimed to describe the changes in biomechanical properties of the supraspinatus tendon, deltoid muscle, and humeral head post arthroscopic rotator cuff repair using shear wave elastography. Shear wave velocity of the tendon, deltoid, and humeral head of 48 patients was measured at predetermined sites at 1 week, 6 weeks, 12 weeks, 6 months, and 12 months post repair. One-way ANOVA with Tukey's correction and Spearman's correlation were performed. Mean±SEM healing tendon stiffness, adjacent to tendon footprint, increased from 1 week (6.2±0.2 m/s) to 6 months (7.5±0.3 m/s) and 12 months (7.8±0.3 m/s) (P<0.001). Mean±SEM deltoid muscle stiffness was higher at 12 months (4.1±0.2 m/s) compared to 1 week (3.4±0.1 m/s) and 12 weeks (3.5±0.1 m/s) (P<0.05). Humeral head stiffness did not change. Following arthroscopic rotator cuff repair, supraspinatus tendon stiffness increased in a curvilinear fashion over 6 months. From 6 months, deltoid muscle stiffness increased, corresponding to when patients were instructed to return to normal activities.

Mechanical characterization of human skin-A non-invasive digital twin approach using vibration-response integrated with numerical methods

This paper proposes an innovative approach to identify elastic material properties and mass density of soft tissues based on interpreting their mechanical vibration response, externally excited by a mechanical indenter or acoustic waves. A vibration test is performed on soft sheets to measure their response to a continuous range of excitation frequencies. The frequency responses are collected with a pair of high-speed cameras in conjunction with 3-D digital image correlation (DIC). Two cases are considered, including suspended/fully-free rectangular neoprene sheets as artificial tissue cutout samples and continuous layered human skin vibrations. An efficient theoretical model is developed to analytically simulate the free vibrations of the neoprene artificial sheet samples as well as the continuous layered human skins. The high accuracy and validity of the presented analytical simulations are demonstrated through comparison with the DIC measurements and the conducted frequency tests, as well as a number of finite element (FE) modeling. The developed analytical approach is implemented into a numerical algorithm to perform an inverse calculation of the soft sheets' elastic properties using the imported experimental vibration results and the predicted system's mass via the system equivalent reduction/expansion process (SEREP) method. It is shown that the proposed frequency-dependent inverse approach is capable of rapidly predicting the material properties of the tested samples with high accuracy.

Dynamic Correlations and Disorder in the Masticatory Musculature Network

BACKGROUND

Temporomandibular joint (TMJ) disorders, which affect millions of people worldwide, have multiple etiological factors that make an accurate diagnosis and effective treatments difficult. As a consequence, the gold standard diagnostic criteria for TMJ disorders remain elusive and often depend on subjective decisions.

AIM

In this context, the lack of a non-invasive quantitative methodology capable of assessing the functional physiological state and, consequently, identifying risk indicators for the early diagnosis of TMJ disorders must be tackled and resolved.

METHODOLOGY

In this work, we have studied the biomechanics and viscoelastic properties of the functional masticatory system by a non-invasive approach involving 52 healthy subjects, analysed by statistical-physics analysis applied to myotonic measurements on specific points of the masticatory system designing a TMJ network composed of 17 nodes and 20 links.

RESULTS

We find that the muscle tone and viscoelasticity of a specific cycle linking frontal, temporal, and mandibular nodes of the network play a prominent role in the physiological functionality of the system. At the same time, the functional state is characterised by a landscape of nearly degenerated levels of elasticity in all links of the network, making this parameter critically distributed and deviating from normal behaviour.

CONCLUSIONS

Time evolution and dynamic correlations between biomechanics and viscoelastic parameters measured on the different cycles of the network provide a quantitative framework associated with the functional state of the masticatory system. Our results are expected to contribute to enriching the taxonomy of this system, primarily based on clinical observations, patient symptoms, and expert consensus.

Effect of Knee Angle and Quadriceps Muscle Force on Shear-Wave Elastography Measurements at the Patellar Tendon

Shear-wave elastography (SWE) is a non-invasive imaging technique that provides estimates of tissue stiffness via shear-wave speed measurements. No standardized protocol currently exists for SWE of the patellar tendon, which may be influenced by knee angle and quadriceps muscle force. In this study, the reliability of SWE in cadaveric patellar tendons was examined at three knee angles (0°, 30° and 60°) and three quadriceps muscle forces (0, 50 and 100 N). Shear-wave speed was significantly higher at a knee angle of 60° than at 0° or 30° (increases of 7% and 9%, respectively), and when the quadriceps muscle force was greater than or equal to 50 N (increase of 15%). SWE of the patellar tendon displayed excellent repeatability regardless of knee angle as long as no quadriceps force was generated (intra-class correlation coefficient ≥0.91). This research illustrates the importance of controlling knee angle and quadriceps force for consistency and comparison of SWE results.

The Measurement of Stiffness for Major Muscles with Shear Wave Elastography and Myoton: A Quantitative Analysis Study

The present study was performed to assess the relationship between hand-held myotonometer MyotonPRO and shear wave elastography (SWE) measurements of lower limb muscle stiffness during resting and active voluntary contraction. Forty healthy young adults, (20 males and 20 females) participated in the study. The stiffness of each subject’s rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius (MG) was measured repeatedly by MyotonPRO and SWE. Moderate to strong correlations between the two methods’ measurements were found for both resting and active voluntary contraction. (r = 0.416–0.669, p < 0.05; r = 0.398–0.594, p < 0.05, respectively). Muscle stiffness at rest was significantly lower compared contraction in all four muscles measured by both methods (p < 0.05). Intra-rater reliabilities were generally lower when measurements were taken during contraction. Additionally, when compared by gender, muscle stiffness measured by MyotonPRO was significantly higher at rest in men compared to women, except for the TA. However, a significant difference was found in TA muscle stiffness by gender when measured with SWE. When muscles were contracted, all muscles showed significantly higher stiffness in men compared to women. There were moderate to good correlations in muscle stiffness between measurements of SWE and MyotonPRO at rest and during active voluntary contraction. Additionally, both instruments showed good intra-rater reliability.

Nano-elastic modulus of tendon measured directly in living mice

The nano-biomechanical environment of the extracellular matrix is critical for cells to sense and respond to mechanical loading. However, to date, this important characteristic remains poorly understood in living tissue structures. This study reports the experimental measurement of the in vivo nano-elastic modulus of the tendon in a mouse tail model. The experiment was performed on the tail tendon of an 8-week-old C57BL/6 live mouse. Mechanical loading on tail tendons was regulated by changing both voltage and frequency of alternating current stimulation on the erector spinae. The nano-elastic modulus of the tail tendon was measured by atomic force microscope. The nano-elastic modulus showed significant variation (2.19-35.70 MPa) between different locations and up to 39% decrease under muscle contraction, suggesting a complicated biomechanical environment in which cells dwell. In addition, the nano-elastic modulus of the tail tendon measured in live mice was significantly lower than that measured in vitro, suggesting a disagreement of tissue mechanical properties in vivo and in vitro. This information is important for the designs of new extracellular biomaterial that can better mimic the biological environment, and improve clinical outcomes of musculoskeletal tissue degenerations and associated disorders.

Cross-Sectional Area Measurement Techniques of Soft Tissue: A Literature Review

Evaluation of the biomechanical properties of soft tissues by measuring the stress-strain relationships has been the focus of numerous investigations. The accuracy of stress depends, in part, upon the determination of the cross-sectional area (CSA). However, the complex geometry and pliability of soft tissues, especially ligaments and tendons, make it difficult to obtain accurate CSA, and the development of CSA measurement methods of soft tissues continues. Early attempts to determine the CSA of soft tissues include gravimetric method, geometric approximation technique, area micrometer method, and microtomy technique. Since 1990, a series of new methods have emerged, including medical imaging techniques (e.g. magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound imaging (USI)), laser techniques (e.g. the laser micrometer method, the linear laser scanner (LLS) technique, and the laser reflection system (LRS) method), molding techniques, and three-dimensional (3D) scanning techniques.

Assessment of common extensor tendon elasticity in patients with lateral epicondylitis using shear wave elastography

Background

To investigate the role of shear wave elastography (SWE) in patients with lateral epicondylitis (LE) by assessing the common extensor tendon (CET) elasticity.

Methods

A total of 62 unilateral LE patients were enrolled. Shear wave speed (SWS) and the thickness of CET in both elbows, along with the involved elbows with pre- and post-treatment, were obtained by SWE. The differences between groups, inter- and intra-observer agreements, and diagnostic accuracy were analyzed with a paired t-test, intraclass correlation coefficients (ICCs), and receiver operator characteristic (ROC) curve, respectively.

Results

LE patients had significantly lower SWS on lesion sides compared to healthy elbows (P<0.05). The SWS of involved elbows were significantly higher after non-operation treatment than before treatment. The inter- and intra-observer agreements were excellent (ICCs: 0.900-0.993) for SWE measurements. Moreover, a 12.2 m/s cutoff value of mean SWS (C _mean) for discriminating LE patients from healthy subjects revealed a sensitivity and specificity of 93% and 93%, respectively.

Conclusions

SWE is a valid imaging technique for the diagnosis of LE and monitoring of the treatment effect. Future studies are essential for investigating the correlations among clinical examinations, conventional ultrasound, and SWE.