Sarah F. Eby

Validation of shear wave elastography in skeletal muscle

Skeletal muscle is a very dynamic tissue, thus accurate quantification of skeletal muscle stiffness throughout its functional range is crucial to improve the physical functioning and independence following pathology. Shear wave elastography (SWE) is an ultrasound-based technique that characterizes tissue mechanical properties based on the propagation of remotely induced shear waves. The objective of this study is to validate SWE throughout the functional range of motion of skeletal muscle for three ultrasound transducer orientations. We hypothesized that combining traditional materials testing (MTS) techniques with SWE measurements will show increased stiffness measures with increasing tensile load, and will correlate well with each other for trials in which the transducer is parallel to underlying muscle fibers. To evaluate this hypothesis, we monitored the deformation throughout tensile loading of four porcine brachialis whole-muscle tissue specimens, while simultaneously making SWE measurements of the same specimen. We used regression to examine the correlation between Youngs modulus from MTS and shear modulus from SWE for each of the transducer orientations. We applied a generalized linear model to account for repeated testing. Model parameters were estimated via generalized estimating equations. The regression coefficient was 0.1944, with a 95% confidence interval of (0.1463-0.2425) for parallel transducer trials. Shear waves did not propagate well for both the 45° and perpendicular transducer orientations. Both parallel SWE and MTS showed increased stiffness with increasing tensile load. This study provides the necessary first step for additional studies that can evaluate the distribution of stiffness throughout muscle.

Ultrasound elastography: the new frontier in direct measurement of muscle stiffness.

The use of brightness-mode ultrasound and Doppler ultrasound in physical medicine and rehabilitation has increased dramatically. The continuing evolution of ultrasound technology has also produced ultrasound elastography, a cutting-edge technology that can directly measure the mechanical properties of tissue, including muscle stiffness. Its real-time and direct measurements of muscle stiffness can aid the diagnosis and rehabilitation of acute musculoskeletal injuries and chronic myofascial pain. It can also help monitor outcomes of interventions affecting muscle in neuromuscular and musculoskeletal diseases, and it can better inform the functional prognosis. This technology has implications for even broader use of ultrasound in physical medicine and rehabilitation practice, but more knowledge about its uses and limitations is essential to its appropriate clinical implementation. In this review, we describe different ultrasound elastography techniques for studying muscle stiffness, including strain elastography, acoustic radiation force impulse imaging, and shear-wave elastography. We discuss the basic principles of these techniques, including the strengths and limitations of their measurement capabilities. We review the current muscle research, discuss physiatric clinical applications of these techniques, and note directions for future research.

Shear wave elastography of passive skeletal muscle stiffness: Influences of sex and age throughout adulthood

BACKGROUND Numerous structural and compositional changes - related not only to age, but also activity level and sex - may affect skeletal muscle stiffness across the adult age-span. Measurement techniques available thus far have largely limited passive stiffness evaluations to those of entire joints and muscle-tendon units. Shear wave elastography is an increasingly popular ultrasound technique for evaluating the mechanical properties of skeletal muscle tissue. The purpose of this study was to quantify the passive stiffness, or shear modulus, of the biceps brachii throughout adulthood in flexed and extended elbow positions. We hypothesized that shear modulus would be higher in males relative to females, and with advanced age in both sexes. METHODS Shear wave elastography quantified biceps brachii stiffness at 90° elbow flexion and full extension in a large sample of adults between 21 and 94 years old (n=133; 47 males). FINDINGS Regression analysis found sex and age were significant parameters for older adults (>60 years) in full extension. As expected, shear modulus values increased with advancing age; however, shear modulus values for females tended to be higher than those for males. INTERPRETATION This study begins to establish normative trends for skeletal muscle shear modulus throughout adulthood. Specifically, this work establishes for the first time that the higher passive joint torque often found in males relative to females likely relates to parameters other than muscle shear modulus. Indeed, perhaps increases in skeletal muscle passive stiffness, though potentially altering the length-tension curve, serve a protective role - maintaining the tendon-muscle-tendon length-tension curve within a functional range.

Magnetic Resonance Imaging of the Throwing Elbow in the Uninjured, High School–Aged Baseball Pitcher

Background: Tissue adaptations in response to pitching are an expected finding during magnetic resonance imaging (MRI) evaluation of the throwing elbow of adult pitchers. These changes are considered normal in the absence of symptom complaints. It is unclear when during the playing career these tissue adaptations are initiated. Hypothesis: Abnormalities in the appearance of the throwing elbow compared with the nonthrowing elbow would be visible during MRI assessment of this asymptomatic population of high school–aged throwers. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Twenty-three uninjured, asymptomatic male high school–aged baseball pitchers (mean age, 16 years) with no history of elbow injury were recruited for the study. Participants had a minimum of 3 years’ experience with pitching as their primary position (mean experience, 6 years). Bilateral elbow MRI examinations were performed using a standardized protocol including fast spin-echo proton-density (axial and coronal), T1-weighted (sagittal), and T2-weighted fat-saturated (axial, sagittal, and coronal) sequences. Osteoarticular, ligamentous, musculotendinous, and neural structures were evaluated and compared bilaterally. The images were reviewed by a musculoskeletal radiologist who was blinded to all the gathered data on these athletes, including limb dominance. Results: Three participants (13%) had no abnormalities. Fifteen individuals (65%) had asymmetrical anterior band ulnar collateral ligament thickening, including 4 individuals who also had mild sublime tubercle/anteromedial facet edema. Fourteen participants (61%) had posteromedial subchondral sclerosis of the ulnotrochlear articulation, including 8 (35%) with a posteromedial ulnotrochlear osteophyte, and 4 (17%) with mild posteromedial ulnotrochlear chondromalacia. Ten individuals (43%) had multiple abnormal findings in the throwing elbow. Conclusion: Thickening of the anterior band of the ulnar collateral ligament and posteromedial subchondral sclerosis of the trochlea are common findings in the high school–aged pitcher and may be considered normal clinical findings in the absence of symptom complaints. Other changes in tissue appearance of the throwing elbow are uncommon in this age group and should be regarded with a higher level of caution when evaluating for the presence of injury. An understanding of the MRI appearance of the uninjured youth pitcher is necessary for clinicians to distinguish between normal adaptations and the presence of injury.

Feasibility and Reliability of Quantifying Passive Muscle Stiffness in Young Children by Using Shear Wave Ultrasound Elastography

The purpose of this study was to investigate the feasibility and reliability of passive muscle stiffness measurements in children by shear wave ultrasound elastography.

Quantifying passive muscle stiffness in children with and without cerebral palsy using ultrasound shear wave elastography

The aim of this study was to compare passive muscle stiffness in children with cerebral palsy (CP) and children with typical development using a novel ultrasound technique: ultrasound shear wave elastography (SWE).

Iliac Bone Grafting of the Intact Glenoid Improves Shoulder Stability with Optimal Graft Positioning

BACKGROUND Bone grafting procedures are increasingly popular for the treatment of anterior shoulder instability. In patients with a high risk of recurrence, open coracoid transplantation is preferred but can be technically demanding. Free bone graft glenoid augmentation may be an alternative strategy for high-risk patients without significant glenoid bone loss. This biomechanical cadaveric study assessed the stabilizing effect of free iliac crest bone grafting of the intact glenoid and the importance of sagittal graft position. METHODS Eight fresh frozen cadaveric shoulders were tested. The bone graft was fixed on the glenoid neck at 3 sagittal positions (50%, 75%, and 100% below the glenoid equator). Displacement and reaction force were monitored with a custom device while translating the humeral head over the glenoid surface in both anterior and anteroinferior direction. RESULTS Peak force (PF) increased significantly from the standard labral repair to the grafted conditions in both anterior (14.7 ± 5.5 N vs 27.3 ± 6.9 N) and anteroinferior translation (22.0 ± 5.3 N vs 29.3 ± 6.9 N). PF was significantly higher for the grafts at the 50% and 75% positions compared with the grafts 100% below the equator with anterior translation. Anteroinferior translation resulted in significantly higher values for the 100% and 75% positions compared with the 50% position. CONCLUSIONS This biomechanical study confirms improved anterior glenohumeral stability after iliac crest bone graft augmentation of the anterior glenoid. The results also demonstrate the importance of bone graft position in the sagittal plane, with the ideal position determined by the direction of dislocation.

Quantitative Evaluation of Passive Muscle Stiffness in Chronic Stroke.

ObjectiveThe aim of this study was to evaluate the potential for shear wave elastography (SWE) to measure passive biceps brachii individual muscle stiffness as a musculoskeletal manifestation of chronic stroke. DesignThis was a cross-sectional study. Nine subjects with stroke were evaluated using the Fugl-Meyer and Modified Ashworth scales. Electromyography, joint torque, and SWE of the biceps brachii were obtained during passive elbow extension in subjects with stroke and four controls. Torque values at the time points corresponding to each SWE measurement during all trials were selected for direct comparison with the respective SWE stiffness using regression analysis. Intraclass correlation coefficients (ICC(1,1)) were used to evaluate the reliability of expressing alterations in material properties. ResultsTorque and passive stiffness increased with elbow extension—minimally for the controls and most pronounced in the contralateral limb of those with stroke. In the stroke group, several patterns of shear moduli and torque responses to passive elbow extension were identified, with a subset of several subjects displaying a very strong torque response coupled with minimal stiffness responses (y = 2.712x + 6.676; R2 = 0.181; P = 0.0310). Values of ICC(1,1) indicate consistent muscle stiffness throughout testing for the dominant side of controls, but largely inconsistent stiffness for other study conditions. ConclusionsSWE shows promise for enhancing evaluation of skeletal muscle after stroke. The wide variability between subjects with stroke highlights the need for precise, individualized measures.

Quantifying spasticity in individual muscles using shear wave elastography

Spasticity is common following stroke; however, high subject variability and unreliable measurement techniques limit research and treatment advances. Our objective was to investigate the use of shear wave elastography (SWE) to characterize the spastic reflex in the biceps brachii during passive elbow extension in an individual with spasticity. The patient was a 42-year-old right-hand-dominant male with history of right middle cerebral artery-distribution ischemic infarction causing spastic left hemiparesis. We compared Fugl-Meyer scores (numerical evaluation of motor function, sensation, motion, and pain), Modified Ashworth scores (most commonly used clinical assessment of spasticity), and SWE measures of bilateral biceps brachii during passive elbow extension. We detected a catch that featured markedly increased stiffness of the brachialis muscle during several trials of the contralateral limb, especially at higher extension velocities. SWE was able to detect velocity-related increases in stiffness with extension of the contralateral limb, likely indicative of the spastic reflex. This study offers optimism that SWE can provide a rapid, real-time, quantitative technique that is readily accessible to clinicians for evaluating spasticity.

Thoracogenic spinal deformity: a rare cause of early-onset scoliosis

OBJECTIVESurgery for severe congenital defects, such as congenital diaphragmatic hernia, congenital heart defects, and tracheoesophageal disorders, are life-saving treatments for many infants. However, the incidence of scoliosis following thoracoabdominal surgery has been reported to range from 8% to 50%. Little is known about severe scoliosis that occurs after chest wall procedures in infants. The authors sought to determine the prevalence of thoracogenic scoliosis, disease severity, and need for scoliosis surgery in patients who underwent chest wall procedures in early childhood.METHODSA multicenter database of patients with early-onset scoliosis was queried to identify patients with a history of thoracogenic or acquired iatrogenic scoliosis. Patients with significant congenital spine deformities were excluded. Forty-one patients (1.6%) were noted to have thoracogenic scoliosis. Of these patients, 14 patients were observed; 10 received casts and/or braces; and 17 underwent treatment with rib-based distraction rods, Shilla procedures, or spine-based growing rod devices. Radiographs, complications, and patient characteristics were reviewed.RESULTSThe mean age at scoliosis diagnosis for the 41 patients was 6.0 years. The mean time to follow-up was 2.9 years (4.5 years in the 17 surgical patients). The mean preoperative coronal Cobb angle in the surgical group was 65° and improved to 47° postoperatively (p = 0.01). The mean Cobb angle for the nonoperative group was 31° initially and 32° at follow-up (p = 0.44). Among the 17 patients undergoing surgery for scoliosis, there were 13 complications in 7 patients, including a brachial plexus palsy following rib-based distraction rod placement. This resolved with revision of the rib hooks. There were no known complications in the nonoperative cohort.CONCLUSIONSSevere scoliosis can develop after thoracoabdominal surgeries during infancy. Further work is needed to understand the pathogenesis of scoliosis in this population so as to implement measures for prevention and early diagnosis and to guide appropriate treatment.