Elastographic Region of Interest Determination for Muscle with Fat Infiltration

Muscle belly ratio is the most suitable estimate of the activity of the torn supraspinatus muscle

Background

A torn rotator cuff muscle deteriorates over time leading with an increase in muscle atrophy and fatty infiltration. There are several clinical assessments for evaluating the atrophy of the torn supraspinatus muscle. However, it is unclear which approach can more accurately estimate the activity of the torn supraspinatus muscle. The purpose of this study was to determine which magnetic resonance imaging-based muscle atrophy imaging assessment currently implemented in the clinical setting accurately estimates the activity of the torn supraspinatus muscle.

Methods

Forty patients who were diagnosed with a rotator cuff tear and were candidates for repairs were selected for this study. Cross-sectional area, occupation ratio, and tangent sign were analyzed on T1-weighted oblique sagittal plane magnetic resonance images in which the scapular spine leads to the Y-section. Muscle belly ratio of the supraspinatus muscle was analyzed by calculating the ratio of the width of the muscle belly to the distance from the greater tubercle to the proximal end of the muscle on T1-weighted coronal plane magnetic resonance imaging images. Fatty infiltration was evaluated using the Goutallier classification system. Tear size was obtained intraoperatively by measuring the width and length of the tear and classified based on the Cofield's classification. To assess activity of the torn supraspinatus muscle, participants were first instructed to sit on a chair with the affected arm resting on a table and the shoulder abducted to 60° in the scapular plane with neutral rotation. Elasticity of the supraspinatus muscle belly was then obtained at rest and during isometric contraction using with real-time tissue elastography. Muscle activity, a surrogate for contractility, was defined as the difference between the elasticities measured at rest and during isometric contraction. A stepwise multiple regression analysis was used to investigate independent factors, such as sex, tear width, cross-sectional area, occupation ratio, tangent sign, and muscle belly ratio, related to muscle activity.

Results

Stepwise multiple regression analysis (R2 = 0.522, P < .001) revealed that supraspinatus muscle activity was significantly correlated with muscle belly ratio (β = 0.306, P = .044) and Goutallier stage (β = -0.490, P = .002).

Conclusion

Estimations of muscle belly ratio are most suitable for assessing the activity of a torn supraspinatus muscle compared to other clinical measurements.

Intracompartmental pressure in lower leg muscles and tibial nerve in healthy volunteers correlate to the stiffness measured using shear wave elastography

BACKGROUND

Acute compartment syndrome in the lower leg is a painful condition characterized by an increase in intracompartmental pressure. To prevent misdiagnosis and delay in the recognition of the condition, which can lead to severe complications, continuous monitoring of intracompartmental pressure for at least 24 h. from the onset of initial symptoms has been recommended. The purpose of the current study was to establish shear wave elastography as a potential imaging biomarker for the observed increase in pressure in four compartments of the lower leg.

METHODS

Eighteen healthy participants (9 males) without any injury in their leg muscles were recruited for the study after internal review board approval. Subjects were instructed to sit on a table and pressures at 60, 90, and 120 mmHg were applied using a pressure cuff placed above the proximal pole of the patella. Shear wave elastography-measured stiffness outcomes at baseline (0 mmHg) and at each cuff pressure level were obtained from the tibialis anterior, the peroneus longs, gastrocnemius medialis, and tibialis posterior muscles, as well as the tibial nerve.

FINDINGS

Spearman's rank correlation coefficient showed strong correlations between shear wave elastography-measured stiffness from all four muscles and cuff pressure levels (r > 0.80, P < 0.05). Stiffness from the tibial nerve was also significantly correlated with cuff pressure levels (r > 0.99, P < 0.05).

INTERPRETATION

Shear wave elastography imaging of lower leg muscles and nerve can be useful to non-invasively monitor intracompartmental pressure in patients suspected of acute compartment syndrome.