Anterior deltoid muscle tension quantified with shear wave ultrasound elastography correlates with pain level after reverse shoulder arthroplasty.

INTRODUCTION: Reverse shoulder arthroplasty (RSA) leads to medialization and distalization of the centre of rotation of the shoulder joint resulting in lengthening of the deltoid muscle. Shear wave ultrasound elastography (SWE) is a reliable method for quantifying tissue stiffness. The purpose of this study was to analyse if deltoid muscle tension after RSA correlates with the patients' pain level. We hypothesized that higher deltoid muscle tension would be associated with increased pain. MATERIAL AND METHODS: Eighteen patients treated with RSA were included. Constant score (CS) and pain level on the visual analogue scale (VAS) were analysed and SWE was performed on both shoulders. All three regions of the deltoid muscle were examined in resting position and under standardized isometric loading. RESULTS: Average patient age was 76 (range 64-84) years and average follow-up was 15 months (range 4-48). The average CS was 66 points (range 35-89) and the average pain level on the VAS was 1.8 (range 0.5-4.7). SWE revealed statistically significant higher muscle tension in the anterior and middle deltoid muscle region in patients after RSA compared to the contralateral non-operated side. There was a statistically significant correlation between pain level and anterior deltoid muscle tension. CONCLUSION: SWE revealed increased tension in the anterior and middle portion of the deltoid muscle after RSA in a clinical setting. Increased tension of the anterior deltoid muscle portion significantly correlated with an increased pain level. SWE is a powerful, cost-effective, quick, dynamic, non-invasive, and radiation-free imaging technique to evaluate tissue elasticity in the shoulder with a wide range of applications. LEVEL OF EVIDENCE: Diagnostic study, Level III.

Supraspinatus muscle elasticity measured with real time shear wave ultrasound elastography correlates with MRI spectroscopic measured amount of fatty degeneration.

BACKGROUND: Fatty Degeneration (FD) of the rotator cuff muscles influences functional and anatomical outcome after rotator cuff repair. The MRI based estimation of fatty degeneration is the gold standard. There is some evidence that Ultrasound elastography (EUS) can detect local differences of tissue stiffness in muscles and tendons. Shear-wave elastography (SWE) was evaluated to determine the extent to which shear wave velocity was associated with measures of fatty degeneration. MRI-spectroscopic fat measurement was used as a reference to quantify the amount of fat in the muscle belly. METHODS: Forty-two patients underwent SWE of the supraspinatus muscles at its thickest diameter. After ultrasound evaluation an MRI-spectroscopic fat measurement of the supraspinatus muscle was performed using the SPLASH-technique. A gel filled capsule was used to locate the measured area in the MRI. The values of shear wave velocity (SWV) measured with SWE and spectroscopic fat measurement were correlated statistically using Pearson's correlation test. RESULTS: Correlation of the fat amount measured with MRI-spectroscopy and the SWV measured with SWE was ρ =0.82. Spectroscopic measured fat ratio of the supraspinatus muscle ranged from 0% to 77.41% and SWV from 1.59 m/s to 5.32 m/s. In 4 patients no sufficient SWE could be performed, these individuals showed a larger diameter of the overlying soft tissue. SWV measured with SWE showed a good correlation with MRI spectroscopic fat amount of the supraspinatus muscle. CONCLUSION: These preliminary data suggest that SWE may be a sufficient tool in detecting and estimating the amount of fatty degeneration in the supraspinatus muscle in real time. Large overlying soft tissue may be a limitation in performing sufficient EUS. Ethical Committee Approval: Nr: 156/14 Date 12th August 2014. LEVEL OF EVIDENCE: III.

Automated reconstruction of the initial distribution of laser accelerated ion beams from radiochromic film (RCF) stacks.

Radiochromic film (RCF) stacks are the most commonly used diagnostic of laser accelerated ion beams at Gesellschaft für Schwerionenforschung, Darmstadt (GSI) and at other laboratories. So far, the evaluation of the stacks is performed using manual input for the deposited energy determination. This is usually a tedious task and introduces uncertainty in the resulting ion energy spectrum and also in the corresponding angular distribution. An automated procedure is especially important if larger data sets, containing multiple laser shots, are investigated. Here, we describe an automated procedure for the evaluation of digitized RCF stacks. RCF stacks obtained at GSI's PHELIX laser system are evaluated as a test case. A validation of parts of the procedure is performed on generated input data.