Assessments of Fatty Infiltration and Muscle Atrophy From a Single Magnetic Resonance Image Slice Are Not Predictive of 3-Dimensional Measurements

Single slice MR image estimation of 3D supraspinatus intramuscular fatty infiltration in older adults: relevance for clinical practice and research

OBJECTIVE

(1) To compare older adults stratified by supraspinatus tendon tear status (STT status)-no tear (Intact), partial-thickness (PT) tear, full-thickness (FT) tear-by 3D Dixon fat fraction (3D-FF); 2D fat fraction (2D-FF); and 2D Goutallier grade (2D-GG) at the Y-shaped view, and 1.4 cm and 2.8 cm medial to the Y-shaped view. Stratified by STT status to determine (2) correlation of 3D-FF with 2D-FF and 2D-GG and (3) inter-rater reliability at and medial to the Y-shaped view.

MATERIALS AND METHODS

Forty-five volunteers ≥ 60 years recruited prospectively received shoulder MRI. 3D-FF and 2D-FF were measured on 6-point-Dixon MRI by three trainees. Goutallier grade was assessed on T1-weighted MRI by three fellowship-trained diagnostic radiologists. Descriptive, reliability, and correlation analyses were performed.

RESULTS

Groups showed no difference in age. The FT group showed higher (p < 0.05) mean 3D-FF (14.09% ± 10.99%), mean 2D-FF (1.4 cm medial to Y-shaped view, 14.91% ± 12.11%; 2.8 cm medial to Y-shaped view, 13.32% ± 9.48%), and mean 2D-GG (Y-shaped view, 1.71 ± 0.78; 1.4 cm medial to Y-shaped view, 1.71 ± 0.69; 2.8 cm medial to Y-shaped view, 1.71 ± 0.72), relative to Intact/PT groups. 3D-FF showed strong correlation with 2D-FF among all groups/all analyses (rho, 0.80-0.98; p < 0.001). 3D-FF showed strong correlation with 2D-GG for all FT group analyses (rho, 0.85-0.91; p < 0.05). 3D-FF showed moderate-to-strong correlation considering all Intact/PT group analyses (rho, 0.51-0.79; p < 0.50). Dixon fat fraction showed excellent reliability for all groups (≥ 0.884, intraclass correlation coefficient). Goutallier grade showed excellent reliability for FT group (0.771, weighted Fleiss's kappa) but poor (0.294) and fair (0.502) for Intact and PT groups, respectively.

CONCLUSION

Single slice MR image estimation of 3D supraspinatus intramuscular fatty infiltration has merit for continued use in clinical populations requiring potential rotator-cuff-repair surgery. However, Dixon fat fraction should be prioritized for use in research over Goutallier grade due to superior reliability.

Quantitative evaluation of natural progression of fatty infiltration and muscle atrophy in chronic rotator cuff tears without tear extension using magnetic resonance imaging

Background

The pathology of and mechanisms underlying muscle degeneration remain unclear. We aimed to quantitatively evaluate the natural changes in fatty infiltration and muscle atrophy in patients with chronic rotator cuff tears using 3-dimensional 2-point Dixon magnetic resonance imaging.

Methods

Thirty patients with nonoperatively observed rotator cuff tears without tear extension were evaluated using multiple magnetic resonance imaging examinations with a minimum interval of 2 years. The fatty infiltration ratio (%fat) and muscle volume of the rotator cuff muscles were compared between the 2 examinations in those with supraspinatus (SSP) tear <2 cm (<2 cm SSP group), SSP tear ≥2 cm (≥2 cm SSP group), and massive tear (massive group). The SSP) infraspinatus, and teres minor (ISP + TM), and subscapularis muscles were evaluated.

Results

The massive group showed a significantly greater %fat than the <2 and ≥2 cm SSP groups in the SSP (P = .002) and ISP + TM muscles (P < .001). The total muscle volume did not differ among the 3 groups for all rotator cuff muscle components. The %fat values did not change in any rotator cuff components during the follow-up period in all groups. The total muscle volume in the massive group significantly decreased in the SSP (P = .018) and ISP + TM muscles (P = .013).

Conclusion

The present results indicate that fatty infiltration of the torn muscle occurs in the early phase after a rotator cuff tear, whereas muscle atrophy appears to progress gradually in chronic rotator cuff tears. Early intervention before muscle degeneration should be considered if the tear involves the infraspinatus tendon.

Investigating the relationship between quantitative-based ultrasound and MRI estimations of rotator cuff fatty infiltration

INTRODUCTION

Fatty infiltration (FI) of the rotator cuff has important clinical implications. Quantitatively estimating FI using ultrasound (US) has considerable benefits for assessing FI in a non-invasive, accessible manner. This research investigated whether FI of the supraspinatus (SS) and infraspinatus (IS), estimated using US was related to intramuscular fat fractions measured from magnetic resonance images (MRI).

METHODS

Data from 12 healthy young adult participants were used for analysis. US images of the SS and IS were captured using multiple transducer placement techniques from which echogenicity of the muscle region was quantified. Shoulder MRI were captured from which SS and IS were manually segmented and intramuscular fat fractions calculated. Six upper limb strength exertions were performed, resisted by a hand dynamometer.

RESULTS

IS and SS echogenicity explained a significant amount of variance in MRI fat fractions for certain body positions and transducer techniques. Echogenicity agreement was higher for IS than SS. Significant relationships were identified between strength exertions and both echogenicity and MRI muscle volume, but not MRI fat fraction.

CONCLUSIONS

This research provides preliminary evidence showing that quantitative-based US methods can be used to estimate MRI calculated fat fractions for the rotator cuff.

Natural History of Quantitative Fatty Infiltration and 3D Muscle Volume After Nonoperative Treatment of Symptomatic Rotator Cuff Tears: A Prospective MRI Study of 79 Patients

BACKGROUND

The severity of fatty infiltration (FI) predicts the treatment outcome of rotator cuff tears. The purpose of this investigation was to quantitatively analyze supraspinatus (SSP) muscle FI and volume at the initial presentation and after a 3-month minimum of conservative management. We hypothesized that progression of FI could be predicted with initial tear size, FI, and muscle volume.

METHODS

Seventy-nine shoulders with rotator cuff tears were prospectively enrolled, and 2 magnetic resonance imaging (MRI) scans with 6-point Dixon sequences were acquired. The fat fraction within the SSP muscle was measured on 3 sagittal slices, and the arithmetic mean was calculated (FI SSP ). Advanced FI SSP was defined as ≥8%, pathological FI SSP was defined as ≥13.5%, and relevant progression was defined as a ≥4.5% increase in FI SSP . Furthermore, muscle volume, tear location, size, and Goutallier grade were evaluated.

RESULTS

Fifty-seven shoulders (72.2%) had normal FI SSP , 13 (16.5%) had advanced FI SSP , and 9 (11.4%) had pathological FI SSP at the initial MRI scan. Eleven shoulders (13.9%) showed a ≥4.5% increase in FI SSP at 19.5 ± 14.7 months, and 17 shoulders (21.5%) showed a ≥5-mm 3 loss of volume at 17.8 ± 15.3 months. Five tears (7.1%) with initially normal or advanced FI SSP turned pathological. These tears, compared with tears that were not pathological, had significantly higher initial mediolateral tear size (24.8 compared with 14.3 mm; p = 0.05), less volume (23.5 compared with 34.2 mm 3 ; p = 0.024), more FI SSP (9.6% compared with 5.6%; p = 0.026), and increased progression of FI SSP (8.6% compared with 0.5%; p < 0.001). An initial mediolateral tear size of ≥20 mm yielded a relevant FI SSP progression rate of 81.8% (odds ratio [OR], 19.0; p < 0.001). Progression rates of 72.7% were found for both initial FI SSP of ≥9.9% (OR, 17.5; p < 0.001) and an initial anteroposterior tear size of ≥17 mm (OR, 8.0; p = 0.003). Combining these parameters in a logistic regression analysis led to an area under the receiver operating characteristic curve (AUC) of 0.913. The correlation between FI SSP progression and the time between MRI scans was weak positive (ρ = 0.31).

CONCLUSIONS

Three risk factors for relevant FI progression, quantifiable on the initial MRI, were identified: ≥20-mm mediolateral tear size, ≥9.9% FI SSP , and ≥17-mm anteroposterior tear size. These thresholds were associated with a higher risk of tear progression: 19 times higher for ≥20-mm mediolateral tear size, 17.5 times higher for ≥9.9% FI SSP , and 8 times higher for ≥17-mm anteroposterior tear size. The presence of all 3 yielded a 91% chance of ≥4.5% progression of FI SSP within a mean of 19.5 months.

LEVEL OF EVIDENCE

Diagnostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Artificial intelligence powered advancements in upper extremity joint MRI: A review

Magnetic resonance imaging (MRI) is an indispensable medical imaging examination technique in musculoskeletal medicine. Modern MRI techniques achieve superior high-quality multiplanar imaging of soft tissue and skeletal pathologies without the harmful effects of ionizing radiation. Some current limitations of MRI include long acquisition times, artifacts, and noise. In addition, it is often challenging to distinguish abutting or closely applied soft tissue structures with similar signal characteristics. In the past decade, Artificial Intelligence (AI) has been widely employed in musculoskeletal MRI to help reduce the image acquisition time and improve image quality. Apart from being able to reduce medical costs, AI can assist clinicians in diagnosing diseases more accurately. This will effectively help formulate appropriate treatment plans and ultimately improve patient care. This review article intends to summarize AI's current research and application in musculoskeletal MRI, particularly the advancement of DL in identifying the structure and lesions of upper extremity joints in MRI images.

Impact of Deltoid Computer Tomography Image Data on the Accuracy of Machine Learning Predictions of Clinical Outcomes after Anatomic and Reverse Total Shoulder Arthroplasty

Background: Despite the importance of the deltoid to shoulder biomechanics, very few studies have quantified the three-dimensional shape, size, or quality of the deltoid muscle, and no studies have correlated these measurements to clinical outcomes after anatomic (aTSA) and/or reverse (rTSA) total shoulder arthroplasty in any statistically/scientifically relevant manner. Methods: Preoperative computer tomography (CT) images from 1057 patients (585 female, 469 male; 799 primary rTSA and 258 primary aTSA) of a single platform shoulder arthroplasty prosthesis (Equinoxe; Exactech, Inc., Gainesville, FL) were analyzed in this study. A machine learning (ML) framework was used to segment the deltoid muscle for 1057 patients and quantify 15 different muscle characteristics, including volumetric (size, shape, etc.) and intensity-based Hounsfield (HU) measurements. These deltoid measurements were correlated to postoperative clinical outcomes and utilized as inputs to train/test ML algorithms used to predict postoperative outcomes at multiple postoperative timepoints (1 year, 2-3 years, and 3-5 years) for aTSA and rTSA. Results: Numerous deltoid muscle measurements were demonstrated to significantly vary with age, gender, prosthesis type, and CT image kernel; notably, normalized deltoid volume and deltoid fatty infiltration were demonstrated to be relevant to preoperative and postoperative clinical outcomes after aTSA and rTSA. Incorporating deltoid image data into the ML models improved clinical outcome prediction accuracy relative to ML algorithms without image data, particularly for the prediction of abduction and forward elevation after aTSA and rTSA. Analyzing ML feature importance facilitated rank-ordering of the deltoid image measurements relevant to aTSA and rTSA clinical outcomes. Specifically, we identified that deltoid shape flatness, normalized deltoid volume, deltoid voxel skewness, and deltoid shape sphericity were the most predictive image-based features used to predict clinical outcomes after aTSA and rTSA. Many of these deltoid measurements were found to be more predictive of aTSA and rTSA postoperative outcomes than patient demographic data, comorbidity data, and diagnosis data. Conclusions: While future work is required to further refine the ML models, which include additional shoulder muscles, like the rotator cuff, our results show promise that the developed ML framework can be used to evolve traditional CT-based preoperative planning software into an evidence-based ML clinical decision support tool.

Longitudinal Changes in Overall 3D Supraspinatus Muscle Volume and Intramuscular Fatty Infiltration After Arthroscopic Rotator Cuff Repair

BACKGROUND

There is considerable debate regarding the longitudinal changes in overall rotator cuff (RC) muscle atrophy and intramuscular fatty infiltration (FI) following RC repair. We analyzed the longitudinal changes in overall 3D supraspinatus muscle volume and intramuscular FI (3D FI) to determine the effect of tear size and repair integrity on 3D muscle volume and intramuscular FI.

METHODS

Forty-seven patients who underwent arthroscopic RC repair and had 6-point Dixon shoulder magnetic resonance imaging (MRI) preoperatively and 3 and 12 months postoperatively were enrolled. The 3D supraspinatus muscle volume and intramuscular FI were calculated at the 3 time points, and their changes over time were evaluated in the entire cohort as well as according to tear size and repair integrity. The agreement of the difference between time points among the patients was assessed by Bland-Altman analysis.

RESULTS

In the cohort as a whole, there were no significant longitudinal changes in the 3D supraspinatus volume (19.65 ± 7.26 to 19.48 ± 7.46 cm 3 , p = 0.911) or 3D FI (17.18% ± 8.85% to 17.30% ± 9.18%, p = 0.977) from preoperatively to the final 12-month time point, overall and in the tear size and repair integrity subgroups. The 3D supraspinatus volume was significantly decreased at 3 months (17.39 ± 6.12 cm 3 , p < 0.001) but then increased again by 12 months (p < 0.001), reaching a value similar to the preoperative level. The 3D FI had a small increase at 3 months (18.18% ± 9.65%, p = 0.097) but subsequently decreased slightly again (p = 0.211), such that there were no significant longitudinal changes. The differences in the 3D supraspinatus volume and FI between these time points showed high agreement among patients.

CONCLUSIONS

The overall 3D supraspinatus volume and 3D FI showed no longitudinal change between the preoperative baseline and the 12-month follow-up after arthroscopic RC repair. Tear size and repair integrity had no impact on the longitudinal patterns of muscle volume and intramuscular FI changes. The 3D supraspinatus volume decreased during the first 3 months but recovered to baseline at 12 months postoperatively; 3D FI was relatively stable throughout the 12 months of follow-up after repair.

LEVEL OF EVIDENCE

Therapeutic Level II . See Instructions for Authors for a complete description of levels of evidence.

Local Injection of Rapamycin-Loaded Pcl-Peg Nanoparticles for Enhanced Tendon Healing in Rotator Cuff Tears via Simultaneously Reducing Fatty Infiltration and Drug Toxicity

As a common cause of shoulder pain, rotator cuff tears (RCTs) are difficult to treat clinically because of their unsatisfactory prognosis due to the fatty infiltration caused by muscle-derived stem cells (MDSCs). Previous studies have found that rapamycin (RAPA) can inhibit fatty infiltration. However, systemic administration of RAPA may cause complications such as infection and nausea, while local administration of RAPA may lead to the cytotoxicity of tendon cells, affecting the healing of rotator cuffs. In this study, biocompatible and clinically approved polycaprolactone-polyethylene glycol (PCL-PEG) is formulated into an injectable nanoparticle for the sustained release of RAPA. The results indicate that the RAPA/PCL-PEG nanoparticles (NPs) can efficiently prolong the release of RAPA and significantly reduce the cytotoxicity of tendon cells caused by RAPA. The study of the fatty infiltration model in rats with delayed rotator cuff repair shows that weekly intraarticular injection of RAPA/PCL-PEG NPs can more effectively reduce the fatty infiltration and muscle atrophy of rat rotator cuffs and leads to better mechanical properties and gait improvements than a daily intraarticular injection of RAPA. These findings imply that local injection of RAPA/PCL-PEG NPs in the shoulder joints can be a potential clinical option for RCTs patients with fatty infiltration.

Are glenoid retroversion, humeral subluxation, and Walch classification associated with a muscle imbalance?

BACKGROUND

The etiology of humeral posterior subluxation remains unknown, and it has been hypothesized that horizontal muscle imbalance could cause this condition. The objective of this study was to compare the ratio of anterior-to-posterior rotator cuff and deltoid muscle volume as a function of humeral subluxation and glenoid morphology when analyzed as a continuous variable in arthritic shoulders.

METHODS

In total, 333 computed tomography scans of shoulders (273 arthritic shoulders and 60 healthy controls) were included in this study and were segmented automatically. For each muscle, the volume of muscle fibers without intramuscular fat was measured. The ratio between the volume of the subscapularis and the volume of the infraspinatus plus teres minor (AP ratio) and the ratio between the anterior and posterior deltoids (APdeltoid) were calculated. Statistical analyses were performed to determine whether a correlation could be found between these ratios and glenoid version, humeral subluxation, and/or glenoid type per the Walch classification.

RESULTS

Within the arthritic cohort, no statistically significant difference in the AP ratio was found between type A glenoids (1.09 ± 0.22) and type B glenoids (1.03 ± 0.16, P = .09), type D glenoids (1.12 ± 0.27, P = .77), or type C glenoids (1.10 ± 0.19, P > .999). No correlation was found between the AP ratio and glenoid version (ρ = -0.0360, P = .55) or humeral subluxation (ρ = 0.076, P = .21). The APdeltoid ratio of type A glenoids (0.48 ± 0.15) was significantly greater than that of type B glenoids (0.35 ± 0.16, P < .01) and type C glenoids (0.21 ± 0.10, P < .01) but was not significantly different from that of type D glenoids (0.64 ± 0.34, P > .999). When evaluating both healthy control and arthritic shoulders, moderate correlations were found between the APdeltoid ratio and both glenoid version (ρ = 0.55, P < .01) and humeral subluxation (ρ = -0.61, P < .01).

CONCLUSION

This in vitro study supports the use of software for fully automated 3-dimensional reconstruction of the 4 rotator cuff muscles and the deltoid. Compared with previous 2-dimensional computed tomography scan studies, our study did not find any correlation between the anteroposterior muscle volume ratio and glenoid parameters in arthritic shoulders. However, once deformity occurred, the observed APdeltoid ratio was lower with type B and C glenoids. These findings suggest that rotator cuff muscle imbalance may not be the precipitating etiology for the posterior humeral subluxation and secondary posterior glenoid erosion characteristic of Walch type B glenoids.

Individuals with rotator cuff tears unsuccessfully treated with exercise therapy have less inferiorly oriented net muscle forces during scapular plane abduction

Exercise therapy for individuals with rotator cuff tears fails in approximately 25.0 % of cases. One reason for failure of exercise therapy may be the inability to strengthen and balance the muscle forces crossing the glenohumeral joint that act to center the humeral head on the glenoid. The objective of the current study was to compare the magnitude and orientation of the net muscle force pre- and post-exercise therapy between subjects successfully and unsuccessfully (e.g. eventually underwent surgery) treated with a 12-week individualized exercise therapy program. Twelve computational musculoskeletal models (n = 6 successful, n = 6 unsuccessful) were developed in OpenSim (v4.0) that incorporated subject specific tear characteristics, muscle peak isometric force, in-vivo kinematics and bony morphology. The models were driven with experimental kinematics and the magnitude and orientation of the net muscle force was determined during scapular plane abduction at pre- and post-exercise therapy timepoints. Subjects unsuccessfully treated had less inferiorly oriented net muscle forces pre- and post-exercise therapy compared to subjects successfully treated (p = 0.039 & 0.045, respectively). No differences were observed in the magnitude of the net muscle force (p > 0.05). The current study developed novel computational musculoskeletal models with subject specific inputs capable of distinguishing between subjects successfully and unsuccessfully treated with exercise therapy. A less inferiorly oriented net muscle force in subjects unsuccessfully treated may increase the risk of superior migration leading to impingement. Adjustments to exercise therapy programs may be warranted to avoid surgery in subjects at risk of unsuccessful treatment.

Preoperative Shoulder MRI Findings to Predict Subscapularis Tendon Tear Requiring Surgical Repair

Purpose

This study aimed to investigate which indirect parameters on preoperative MRI were the principal predictors of subscapularis tendon tears (STTs) requiring surgical repair.

Materials and Methods

Preoperative MRI scans of 86 patients were retrospectively reviewed for visual assessment of the STT, pathology of the long head of the biceps tendon (LHBT), posterior decentering (PD) of the humeral head, humeral rotation, fatty degeneration, and subscapularis muscle atrophy. To evaluate atrophy, visual grading using the anatomical line connecting the coracoid tip to the glenoid base, designated as the base-to-tip line (BTL), and thickness measurements were performed in the en-face view.

Results

Arthroscopically, 31 patients (36%) exhibited Lafosse type III or IV STT and underwent surgical repair. LHBT pathology (p = 0.002), PD of the humeral head (p = 0.012), fatty degeneration (p < 0.001), and BTL grade (p = 0.003) significantly correlated with STT. In the multivariate analysis, PD of the humeral head (p = 0.011, odds ratio [OR] = 5.14) and fatty degeneration (p = 0.046, OR = 2.81) were independent predictors of STT.

Conclusion

PD of the humeral head and fatty degeneration of the subscapularis can help to diagnose clinically significant STT. Interpretation of these findings may contribute to the planning of an optimal surgical strategy.

Different computed tomography parameters for defining myosteatosis in patients with advanced non-small cell lung cancer

BACKGROUND & AIMS

Myosteatosis, excess muscle fat infiltration, is a novel prognostic factor in cancer patients. To define myosteatosis, skeletal muscle radiodensity (SMD) is most commonly used, while intramuscular adipose tissue (IMAT) is newly introduced. We aimed to compare SMD-defined and IMAT-defined myosteatosis for predicting overall survival (OS) in patients with advanced non-small cell lung cancer (NSCLC) and to explore whether patients with both low SMD and high IMAT had a shorter OS than patients with low SMD or high IMAT alone.

METHODS

We consecutively and prospectively recruited adult patients with stage IIIB or IV NSCLC at a teaching hospital. The mean SMD of all skeletal muscle areas and the area of IMAT on the unenhanced chest computed tomography (CT) images at the 12th thoracic vertebral level were segmented using Mimics version 21.0. Myosteatosis was defined by either low SMD (SMD-defined myosteatosis) or high IMAT (IMAT-defined myosteatosis). The optimal cutoffs for low SMD and high IMAT were also determined using the maximally selected rank statistics method. We calculated hazard ratios (HRs) and the corresponding confidence intervals (CIs) to evaluate the associations of OS with low SMD, high IMAT, and a combination of them.

RESULTS

We included 565 patients (345 men and 220 women; mean age 58.5 ± 9.0 years). Lower IMAT exhibited a tendency toward a favorable prognosis in men (p = 0.0015) and women (p < 0.0001); whereas higher SMD tended to have a favorable prognosis in men (p = 0.0006) and women (p < 0.0001). At baseline, 423 (74.9 %) participants had high IMAT, 432 (76.5 %) participants had low SMD and 370 (65.5 %) participants had both high IMAT and low SMD. Compared to those without either high IMAT or low SMD, the participants with either high IMAT or low SMD had a shorter OS, while the participants with both High IMAT and Low SMD had the shortest OS (log-rank p < 0.0001). After adjustment for the same confounders, high IMAT (HR, 1.44; 95 % CI, 1.10-1.87) and low SMD (HR, 1.92; 95 % CI, 1.36-2.43) were separately associated with poor prognosis. Moreover, the combination of high IMAT and low SMD indicated a higher risk of poor prognosis (HR, 2.43; 95 % CI, 1.62-3.66).

CONCLUSIONS

Both SMD-defined and IMAT-defined myosteatosis are highly prevalent in patients with advanced NSCLC and may serve as independent prognostic factors for OS. The diagnosis of myosteatosis might consider a combination of low SMD and high IMAT because this would help identify patients at a higher risk of mortality.

In vivo imaging of skeletal muscle form and function: 50 years of insight

Skeletal muscle form and function has fascinated scientists for centuries. Our understanding of muscle function has long been driven by advancements in imaging techniques. For example, the sliding filament theory of muscle, which is now widely leveraged in biomechanics research, stemmed from observations made possible by scanning electron microscopy. Over the last 50 years, advancing in medical imaging, combined with ingenuity and creativity of biomechanists, have provide a wealth of new and important insights into in vivo human muscle function. Incorporation of in vivo imaging has also advanced computational modeling and allowed our research to have an impact in many clinical populations. While this review does not provide a comprehensive or meta-analysis of the all the in vivo muscle imaging work over the last five decades, it provides a narrative about the past, present, and future of in vivo muscle imaging.

Objective analysis of partial three-dimensional rotator cuff muscle volume and fat infiltration across ages and sex from clinical MRI scans

Objective analysis of rotator cuff (RC) atrophy and fatty infiltration (FI) from clinical MRI is limited by qualitative measures and variation in scapular coverage. The goals of this study were to: develop/evaluate a method to quantify RC muscle size, atrophy, and FI from clinical MRIs (with typical lateral only coverage) and then quantify the effects of age and sex on RC muscle. To develop the method, 47 full scapula coverage CTs with matching clinical MRIs were used to: correct for variation in scan capture, and ensure impactful information of the RC is measured. Utilizing this methodology and automated artificial intelligence, 170 healthy clinical shoulder MRIs of varying age and sex were segmented, and each RC muscle's size, relative contribution, and FI as a function of scapula location were quantified. A two-way ANOVA was used to examine the effect of age and sex on RC musculature. The analysis revealed significant (p < 0.05): decreases in size of the supraspinatus, teres minor, and subscapularis with age; decreased supraspinatus and increased infraspinatus relative contribution with age; and increased FI in the infraspinatus with age and in females. This study demonstrated that clinically obtained MRIs can be utilized for automatic 3D analysis of the RC. This method is not susceptible to coverage variation or patient size. Application of methodology in a healthy population revealed differences in RC musculature across ages and FI level between sexes. This large database can be used to reference expected muscle characteristics as a function of scapula location and could eventually be used in conjunction with the proposed methodology for analysis in patient populations.

Estimating 3D supraspinatus intramuscular fatty infiltration in older adults: a pilot study

BACKGROUND

A recent report suggests that semi-quantitative two-dimensional Goutallier grade (2D-GG) correlates poorly with quantitative three-dimensional Dixon fat fraction (3D-Dixon-FF) on magnetic resonance imaging (MRI).

PURPOSE

To determine whether the finding of poor correlation of supraspinatus 3D-Dixon-FF with 2D-GG is reproducible, and to determine the strength of the correlation of 3D-Dixon-FF with quantitative 2D Dixon fat fraction (2D-Dixon-FF).

MATERIAL AND METHODS

Ten adults aged ≥60 years were recruited prospectively received shoulder MRI. 2D-Dixon-FF and 3D-Dixon-FF were measured on 6-point Dixon fat fraction maps. 2D-GG was rated on T1-weighted images.

RESULTS

The mean age of participants was 70.7 ± 3.7 years. The mean 3D-Dixon-FF was 8.3% ± 5.7%; the mean 2D-Dixon-FF was 7.3% ± 4.4%; and the mean 2D-GG was 0.9 ± 0.7. There was a strong correlation for 3D-Dixon-FF with 2D-Dixon-FF (rho = 0.90; P < 0.001) and with 2D-GG (rho = 0.73; P = 0.017). Excellent inter-observer reliability was found for Dixon fat fraction (intraclass correlation coefficient = 0.946), which was good for Goutallier grade (weighted kappa = 0.634).

CONCLUSION

Supraspinatus 3D-Dixon-FF had a strong correlation with 2D-Dixon-FF and 2D-GG in our study population.

The Modified Assessment Tool Based on Scapular Y-View for Global Fatty Infiltration in the Supraspinatus Muscle: Correlation, Predictive Performance, and Reliability Analyses

BACKGROUND

The accurate evaluation of rotator cuff (RC) fatty degeneration after tears is critical for appropriate surgical decision making and prognosis. However, there is currently no reliable and practical tool to reflect the global fatty infiltration (Global-FI) throughout the 3-dimensional (3D) volumetric RC muscles.

PURPOSE

(1) To determine the correlations between 2 modified assessment tools and the Global-FI and their predictive performances and reliabilities for Global-FI prediction, and (2) to compare these predictive parameters with those of the conventional tool using a single scapular Y-view slice.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

A total of 49 patients with full-thickness RC tears scheduled to undergo arthroscopic repairs were included, and their surgical shoulders underwent 6-point Dixon magnetic resonance imaging preoperatively. The Global-FI was measured by calculating the 3D-volumetric fat fraction (FF) of the whole supraspinatus muscle through all acquired oblique sagittal slices. As a commonly used radiological landmark, the scapular Y-view was used to evaluate single-plane fatty infiltration (Y-FI) by calculating the FF in 1 slice, defined as the conventional assessment tool. Two modified assessment tools expand the analytic imaging by integrating the FFs from the scapular Y-view slice and its neighboring slices, which were calculated by averaging the FFs of these 3 slices (^meanY₃-FI) and accumulating local 3D-volumetric FFs from 3 slices (^volY₃-FI), respectively. The correlations between 3 assessment tools and the Global-FI were analyzed, and the predictive performance for Global-FI prediction using these tools was determined by goodness of fit and agreement. Moreover, the inter- and intraobserver reliabilities of these assessment tools were evaluated. Similar analyses were performed in the small-medium, large, or massive tear subgroups.

RESULTS

The Y-FI was significantly higher than the Global-FI in all cases and tear size subgroups, while the 2 modified assessment tools (^meanY₃-FI and ^volY₃-FI) did not significantly differ from the Global-FI. All assessment tools were significantly correlated with the Global-FI, but the ^meanY₃-FI and ^volY₃-FI showed stronger correlations than the Y-FI, which was also determined in different tear sizes. Moreover, the regression models of the ^meanY₃-FI and ^volY₃-FI showed superior goodness of fit to Y-FI in Global-FI prediction in all cases and subgroups, with larger coefficients of determination (R²) and smaller root mean square errors. The predicted Global-FI using the regression model of ^volY₃-FI had the best agreement with the measured Global-FI, followed by the ^meanY₃-FI, both showing smaller biases and standard deviation of the percentage difference between predicted- and measured Global-FI than the conventional Y-FI. In addition, the 2 modified assessment tools achieved better interobserver and intraobserver reliabilities than the conventional tool in all cases and subgroups.

CONCLUSION

Two modified assessment tools (^meanY₃-FI and ^volY₃-FI) were comparable with the Global-FI of the whole supraspinatus muscle, showing stronger correlations with the Global-FI and better predictive performances and reliabilities than the conventional tool (Y-FI). Moreover, the ^volY₃-FI was slightly superior to ^meanY₃-FI in the predictive performance and reliability.

The 3-Dimensional Fatty Infiltration in the Overall Supraspinatus Can Be Predicted by Localized Sectional Accumulation Units: A Cross-Sectional Study in Patients with Atraumatic Small-to-Massive Rotator Cuff Tears

BACKGROUND

Fatty infiltration (FI) of the rotator cuff (RC) muscles is one of the most common risk factors for a retear following RC repair. Recent methodological developments focus on using 3-dimensional measurements of the overall FI of RC muscles instead of using single-plane-based measurements. However, the required labor-intensive segmentation and time-consuming post-processing steps need to be optimized for routine clinical use.

METHODS

We collected all 6-point Dixon magnetic resonance imaging (MRI) slices of the overall supraspinatus in 46 patients with atraumatic small-to-massive RC tears. Using emerging techniques, the overall 3-dimensional FI of the supraspinatus (overall FI, using all N slices) was assessed as the reference. Each sagittal segment of the supraspinatus was defined as a sectional accumulation unit (SAU). The localized FI in SAUs with different scales of N/3, N/6, and N/12 slices (SAU-FIs) was then calculated using piecewise accumulation by stacking neighboring slices after the overall supraspinatus had been sequentially segmented using MRI slices of the same thickness. The capacity of the SAU-FIs to predict the overall FI, and the ideal locations for prediction, were evaluated using linear regression models after the associations were examined. Goodness-of-fit of the regression models was appraised by the coefficient of determination (R 2 ) and root-mean-square error (RMSE). The agreement between the predicted and measured overall FI was assessed using Bland-Altman analysis and the standard deviation of the percent differences (sd%).

RESULTS

The localized SAU-FIs of the N/3, N/6, and N/12 SAUs generally displayed comparable distributions throughout the normalized distal-proximal long axis of the supraspinatus. The localized SAU-FIs showed substantial correspondence with the overall FI, and the highest correlations were found in the 2/3 SAU (Pearson r and Spearman ρ: 0.95, 0.98), 3/6 and 4/6 SAUs (Pearson r and Spearman ρ: 0.97), and 5/12 to 7/12 SAUs (Pearson r and Spearman ρ: 0.95 to 0.96). The strongest predictors to estimate the overall supraspinatus FI in the regression analysis were these SAU-FIs located in the middle third, which demonstrated good fits to the overall FI (all R 2 ≥ 0.90; RMSE ≤ 1.69). The best agreements between the overall FI predicted by the regression models and the measured overall FI were found in these SAUs (2/3 SAU: sd% = 4.84%; 3/6 and 4/6 SAUs: sd% = 5.14%; 5/12 to 7/12 SAUs: sd% = 6.44%).

CONCLUSIONS

Specific SAUs near the center of the supraspinatus (2/3, 3/6 and 4/6, and 5/12 to 7/12 SAUs), which displayed the best agreement between the predictions and actual measurements of overall FI values, can serve as appropriate surrogates to estimate the overall FI of the supraspinatus in small-to-massive RC tears. The potential to assess the overall FI of the supraspinatus using specific localized SAUs may improve the speed of analytical strategies for accurately assessing the overall FI of RC muscles and thus enable their routine clinical use in the future.

LEVEL OF EVIDENCE

Prognostic Level IV . See Instructions for Authors for a complete description of levels of evidence.

Three-Dimensional Software- and MR-Imaging-Based Muscle Volumetry Reveals Overestimation of Supraspinatus Muscle Atrophy Using Occupation Ratios in Full-Thickness Tendon Tears

Supraspinatus muscle atrophy is widely determined from oblique-sagittal MRI by calculating the occupation ratio. This ex vivo and clinical study aimed to validate the accuracy of 3D software- and MR-imaging-based muscle volumetry, as well as to assess the influence of the tear pattern on the occupation ratio. Ten porcine muscle specimens were volumetrized using the physical water displacement volumetry as a standard of reference. A total of 149 individuals with intact supraspinatus tendons, partial tears, and full-thickness tears had 3T MRI. Two radiologists independently determined occupation ratio values. An excellent correlation with a Pearson’s r of 0.95 for the variables physical volumetry using the water displacement method and MR-imaging-based muscle volumetry using the software was found and formed the standard of reference for the patient study. The inter-reader reliability was 0.92 for occupation ratios. The correlation between occupation ratios and software-based muscle volumes was good in patients with intact tendons (0.84) and partial tears (0.93) but considerably lower in patients with full-thickness tears (0.68). Three-dimensional-software- and MR-imaging-based muscle volumetry is reliable and accurate. Compared to 3D muscle volumetry, the occupation ratio method overestimates supraspinatus muscle atrophy in full-thickness tears, which is most likely due to the medial retraction of the myotendinous unit.

Three-dimensional quantitative measurements of atrophy and fat infiltration in sub-regions of the supraspinatus muscle show heterogeneous distributions: a cadaveric study

INTRODUCTION

Rotator cuff tears are common in the older population. Atrophy and fat infiltration develop un-evenly in torn supraspinatus (SSP) muscles leading to pre- and post-surgical complications. The purpose of the current study was twofold: first, to implement a volumetric and quantitative magnetic resonance imaging (MRI) approach to quantify the degree of muscle atrophy and fat infiltration within the SSP muscle and its four sub-regions (AS, PS, AD, and PD); second to compare 3-D MRI outcomes to the standard 2-D assessment and investigate their relationship with tear size.

MATERIALS AND METHODS

Fifteen cadaveric shoulders were obtained and MRI performed. Quantitative 3-D outcomes included SSP muscle volume, fossa volume, fat-free muscle volume, and fat fraction for the whole SSP muscle and its four sub-regions. 2-D and qualitative measurements included tear size, 2-D fat infiltration using the Goutallier classification, tangent sign, and occupation ratio.

RESULTS

Linear regression outcomes with tear size were not significant for both cross-sectional area (r = - 0.494, p = 0.061) and occupation ratio (r = - 0.011, p = 0.969). Tear size negatively correlated with fat-free muscle volume for both AS and PS sub-regions (AS: r = - 0.78, p < 0.001; PS: r = - 0.68, p = 0.005, respectively) while showing no significant correlation with fat fraction outcomes. AD and PD sub-regions positively correlated with tear size and fat fraction outcomes (AD: r = 0.70, p = 0.017; PD: r = 0.52, p = 0.045, respectively), while no significant correlation was observed between tear size and fat-free muscle volumes.

CONCLUSION

Quantitative 3-D volumetric assessment of muscle degeneration resulted in better outcomes compared to the standard 2-D evaluation. The superficial supraspinatus muscle sub-regions primarily presented muscle atrophy, while the deep sub-regions were mainly affected by fat infiltration. 3-D assessments could be used pre-surgically to determine the best course of treatment and to estimate the muscles' regenerative capacity and function.

MRI-based 3-dimensional volumetric assessment of fatty infiltration and muscle atrophy in rotator cuff tears

BACKGROUND

The Goutallier and Warner Classification systems are useful in determining rotator cuff reparability. Data are limited on how accurately the scapular-Y view used in both systems reflects the 3-dimensional (3-D) changes in fatty infiltration (FI) and muscle atrophy (MA). Tendon retraction in the setting of a cuff tear may also influence the perception of these changes. This study's objectives were to (1) measure the 3-D volume of the supraspinatus muscle in intact rotator cuffs, and with varying magnitudes of retraction; (2) measure the 3-D volume of FI in the supraspinatus muscle in these conditions; and (3) determine the influence of tendon retraction on measured FI and MA using the Goutallier and Warner Classification Systems.

METHODS

Between August 2015 and February 2016, all shoulder magnetic resonance images (MRIs) at the Portland VA Medical Center were standardized to include the medial scapular border. MRIs and charts were reviewed for inclusion/exclusion criteria. Included MRIs were categorized into 4 groups based on rotator cuff retraction. Supraspinatus muscle and fossa were traced to create 3-D volumes. FI and MA were measured within the supraspinatus. The supraspinatus muscle was graded among 6 physicians using the Goutallier and Warner classification systems. These grades were compared to 3-D measured FI and MA. The influence of tendon retraction on the measured grades were also evaluated.

RESULTS

One hundred nine patients met inclusion/exclusion criteria. Ten MRIs for each group (N = 40) were included for image analysis. Supraspinatus volume tracings were highly reproducible and consistent between tracers. Supraspinatus muscle volumes decreased while global FI and MA increased with greater degrees of tendon retraction. In muscles with less than 10% global fat, fat concentrated in the lateral third of the muscle. In muscle with more than 10% global fat content, it distributed more diffusely throughout the muscle from medial to lateral. In comparing the scapular-Y to a medial cut, there was no consistent trend in FI whereas MA was more accurate at the medial cut.

CONCLUSION

Parasagittal imaging location did not significantly influence the Goutallier score; however, assessment of MA using the Warner score leads readers to perceive less MA medially regardless of the magnitude of tendon retraction. The pattern of FI within the supraspinatus muscle changes from a laterally based location around the muscle-tendon junction to a more diffuse, global infiltration pattern when the whole muscle fat content exceeds 10%.

Advantages of 3-dimensional Measurements for Supraspinatus Intramuscular Fatty Evaluation in Patients With Medium to Massive Rotator Cuff Tears: Comparison With a Single Sagittal Slice

BACKGROUND

Fatty infiltration of the rotator cuff muscles is highly related to poor outcomes after rotator cuff tears. Fat fraction (FF) based on traditional 2-dimensional measurements (2D-FF) from a single sagittal Y-view slice cannot determine intramuscular FF in the rotator cuff muscles; the newly developed 3-dimensional method (3D-FF) is supposed to precede 2D measurements for intramuscular FF evaluation in accuracy and reliability.

PURPOSE

(1) To measure 3D-FF and (2) to compare 3D-FF and 2D-FF in terms of quantitative values and intra- and interobserver agreement.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

Six-point Dixon magnetic resonance imaging was performed in patients with full-thickness supraspinatus tears. 2D-FF was calculated on a single sagittal Y-view. Semiautomatic segmentation software (ITK-SNAP) was used to reconstruct 3D volumes of the supraspinatus muscle and fat. 3D-FF was obtained by dividing the fat volume by the total volume of the supraspinatus muscle. A paired t test was used to compare the individual differences between 2D-FF and 3D-FF results. Linear regression and Bland-Altman analyses were performed to determine the agreement between 2D-FF and 3D-FF. Intraclass correlation coefficients (ICCs) were calculated to determine intra- and interobserver agreement.

RESULTS

The 3D muscular and fatty models presented an inhomogeneous distribution of intramuscular fat in the supraspinatus, indicating the superiority of 3D-FF over 2D-FF in capturing all muscle morphologic information. 2D-FF was significantly higher than 3D-FF in the supraspinatus with large (19.5% ± 5.9% vs 16.2% ± 3.7%; P = .002) and massive (34.8% ± 13.3% vs 26.2% ± 9.4%; P < .001) rotator cuff tears. 2D-FF overestimated the FF compared with 3D-FF by >50% in 14.7% of all patients and by >15% in 67.6% of patients with large or massive RCTs. The discrepancy between 2D-FF and 3D-FF increased with increasing mean FF. The intra- and interobserver agreement of 3D-FF (ICCs, 0.89-0.99 and 0.89-0.95) was superior to that of 2D-FF (ICCs, 0.71-0.95 and 0.64-0.79).

CONCLUSION

3D-FF indicated an inhomogeneous distribution of intramuscular fat by capturing all muscle and fat morphologic information. In patients with large and massive rotator cuff tears, 2D-FF of the supraspinatus was significantly higher than 3D-FF. 3D-FF was more reliable than 2D-FF for estimating fatty infiltration in the supraspinatus, with better intra- and interobserver agreement.

Monitoring Rotator Cuff Muscle Fatty Infiltration Progression by Magnetic Resonance Imaging T1 Mapping: Correlation With Direct Evaluation Findings in Rats

BACKGROUND

Monitoring the fatty infiltration (FI) process in rotator cuff muscles is of value in establishing a treatment plan and predicting the postoperative prognosis. Quantitative T1 mapping shows promise for evaluating muscle degeneration, while its validity in monitoring rotator cuff muscle FI progression needs further investigation.

PURPOSE

To determine the validity of T1 mapping in monitoring FI progression of rotator cuff muscles.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sprague-Dawley rats (N = 108) underwent left supraspinatus (SS) and infraspinatus (IS) tenotomy only (TT), suprascapular nerve transection only (NT), or SS and IS tenotomy plus suprascapular nerve transection (TT+NT). Sham surgery on the right shoulder served as the control. The magnetic resonance imaging examination included T1 mapping performed at 12, 16, and 20 weeks postoperation. SS and IS muscles were harvested to quantitatively evaluate FI via direct evaluation (triglyceride quantification assay and histological analysis) at the same predetermined intervals. The correlation of the imaging data with direct evaluation of rotator cuff muscles was analyzed.

RESULTS

T1 values were significantly lower in left SS and IS muscles at 12, 16, and 20 weeks postoperation as compared with those on the right side. T1 values of the left SS and IS muscles were continuously decreased in all groups. The TT+NT group had a greater decrease in T1 value than did the TT and NT groups. Triglyceride quantification assay and histological analysis demonstrated significant and progressive FI of the left SS and IS muscles in the 3 groups. The most serious FI changes were observed in the TT+NT group. T1 values were also well correlated with triglyceride contents and area fractions of fat.

CONCLUSION

T1 mapping can be an effective imaging modality for sensitive and quantitative monitoring of FI progression in rotator cuff muscles.

CLINICAL RELEVANCE

The findings of this study provide a tool for researchers to noninvasively and quantitatively monitor the process of muscle degeneration, contributing to the evaluation of surgical indication and postoperative prognosis.

Three-dimensional muscle loss assessment: a novel computed tomography-based quantitative method to evaluate rotator cuff muscle fatty infiltration

BACKGROUND

Rotator cuff fatty infiltration (FI) is one of the most important parameters to predict the outcome of certain shoulder conditions. The primary objective of this study was to define a new computed tomography (CT)-based quantitative 3-dimensional (3D) measure of muscle loss (3DML) based on the rationale of the 2-dimensional (2D) qualitative Goutallier score. The secondary objective of this study was to compare this new measurement method to traditional 2D qualitative assessment of FI according to Goutallier et al and to a 3D quantitative measurement of fatty infiltration (3DFI).

MATERIALS AND METHODS

102 CT scans from healthy shoulders (46) and shoulders with cuff tear arthropathy (21), irreparable rotator cuff tears (18), and primary osteoarthritis (17) were analyzed by 3 experienced shoulder surgeons for subjective grading of fatty infiltration according to Goutallier, and their rotator cuff muscles were manually segmented. Quantitative 3D measurements of fatty infiltration (3DFI) were completed. The volume of muscle fibers without intramuscular fat was then calculated for each rotator cuff muscle and normalized to the patient's scapular volume to account for the effect of body size (NV_fibers). 3D muscle mass (3DMM) was calculated by dividing the NV_fibers value of a given muscle by the mean expected volume in healthy shoulders. 3D muscle loss (3DML) was defined as 1 - (3DMM). The correlation between Goutallier grading, 3DFI, and 3DML was compared using a Spearman rank correlation.

RESULTS

Interobserver reliability for the traditional 2D Goutallier grading was moderate for the infraspinatus (ISP, 0.42) and fair for the supraspinatus (SSP, 0.38), subscapularis (SSC, 0.27) and teres minor (TM, 0.27). 2D Goutallier grading was found to be significantly and highly correlated with 3DFI (SSP, 0.79; ISP, 0.83; SSC, 0.69; TM, 0.45) and 3DML (SSP, 0.87; ISP, 0.85; SSC, 0.69; TM, 0.46) for all 4 rotator cuff muscles (P < .0001). This correlation was significantly higher for 3DML than for the 3DFI for SSP only (P = .01). The mean values of 3DFI and 3DML were 0.9% and 5.3% for Goutallier 0, 2.9% and 25.6% for Goutallier 1, 11.4% and 49.5% for Goutallier 2, 20.7% and 59.7% for Goutallier 3, and 29.3% and 70.2% for Goutallier 4, respectively.

CONCLUSION

The Goutallier score has been helping surgeons by using 2D CT scan slices. However, this grading is associated with suboptimal interobserver agreement. The new measures we propose provide a more consistent assessment that correlates well with Goutallier's principles. As 3DML measurements incorporate atrophy and fatty infiltration, they could become a very reliable index for assessing shoulder muscle function. Future algorithms capable of automatically calculating the 3DML of the cuff could help in the decision process for cuff repair and the choice of anatomic or reverse shoulder arthroplasty.

Fatty degeneration of the rotator cuff: pathogenesis, clinical implications, and future treatment

Chronic rotator cuff pathology is often complicated by fatty degeneration of the rotator cuff (FDRC) muscles, an insidious process associated with poor prognosis with or without surgical intervention. Currently there is no treatment for FDRC, and many studies have described a natural course for this disease almost always resulting in further degeneration and morbidity. Recapitulating FDRC using animal injury models, and using imaging-based studies of human FDRC, the pathophysiology of this disease continues to be further characterized. Researchers studying mesenchymal stem cell-derived progenitor cells and known fibrogenic and adipogenic signaling pathways implicated in FDRC seek to clarify the underlying processes driving these changes. While new cell- and molecular-based therapies are being developed, currently the strongest available avenue for improved management of FDRC is the use of novel imaging techniques which allow for more accurate and personalized staging of fatty degeneration. This narrative review summarizes the evidence on the molecular and pathophysiologic mechanisms of FDRC and provides a clinical update on the diagnosis and management of this condition based on the existing knowledge. We also sought to examine the role of newer biologic therapies in the management of RC fatty degeneration and to identify areas of future research.

Diagnostic Ultrasound Shows Reversal of Supraspinatus Muscle Atrophy Following Arthroscopic Rotator Cuff Repair

PURPOSE

Prospective study to assess ultrasonography (US) utility as an imaging tool for supraspinatus muscle atrophy diagnosis, establishing if there is any relationship between repairing supraspinatus tears and its eventual muscular recovery.

METHODS

Observational study.

SELECTION CRITERIA

adults with a full-thickness reparable supraspinatus tear confirmed arthroscopically. Clinical and imaging data pre- and postoperatively with 12 months of follow-up were recorded, including demographic data, Constant scale, Patte classification, repair type, and supraspinatus muscle belly US images in both shoulders, recording height, diameter, echogenicity (mean number of pixels between 0-black and 255-white), and central tendon pennate angle (PA).

RESULTS

In total, 110 supraspinatus tears underwent arthroscopic repair (2015-2018). Mean age was 61 ± 8 years (46-77). We detected a correlation between atrophy and age in terms of echogenicity and PA (P = .01). Echogenicity improved from 54.5 to 51.0 (P = .365) and slightly deteriorated on the contralateral side from 51.6 to 52.9 (P = .351). Supraspinatus echogenicity compared to trapezius muscle reduced from 0.43 to 0.36 (P < .001). PA augmented from 5.8 to 8.6 (P < .001). Mean PA on the contralateral side was 8.6 preoperatively. Patte II cases showed the most significant improvement in terms of imaging evaluation of atrophy. Although Patte III cases almost did not improve in terms of atrophy, they improved clinically. We observed improvement after surgery in Constant score from 35 to 85 (P < .001). Minimal clinically important differences for Constant and visual analog scale were 44.45 ± 12.87 and 6.54 ± 1.41, respectively. Recurrence of symptoms was 13%, related to worse results of PA and echogenicity compared to nonrecurrences.

CONCLUSIONS

Supraspinatus atrophic muscle changes after repair can be reversed. It can be quantified using US imaging (histogram, histogram ratio and echogenicity reduction, pennate pattern, and PA augmentation). Patte II cases showed the best results after repair, demonstrated by US. The faster the repair, the better the results without being influenced by repair type. The bigger the tear and retraction, the more echogenicity and less PA, with worse clinical and US results.

LEVEL OF EVIDENCE

Level III, prospective therapeutic study.

Editorial Commentary: Monitoring Tendon and Muscle Recovery After Rotator Cuff Repair Using Diagnostic Ultrasound Demonstrates that Early Repair is Beneficial for Many Patients With Reparable Tears

Rotator cuff repair is performed to effect healing of the enthesis; to restore shoulder comfort, strength, and function; to prevent tear propagation; and to prevent progression of atrophic muscle changes (fatty degeneration, fatty infiltration, and fatty atrophy) that eventually occur. Non-retracted and moderately retracted rotator cuff tears usually heal after repair, and muscle atrophy may recover over time. It follows that early rotator cuff repair is beneficial for many patients with chronic but reparable rotator cuff tears. Diagnostic ultrasound can provide quantitative information about the recovery of both muscle and tendon and represents a viable alternative to magnetic resonance imaging for evaluating healing after rotator cuff repair.

CT-based volumetric assessment of rotator cuff muscle in shoulder arthroplasty preoperative planning

Aims

The aim of this study was to describe a quantitative 3D CT method to measure rotator cuff muscle volume, atrophy, and balance in healthy controls and in three pathological shoulder cohorts.

Methods

In all, 102 CT scans were included in the analysis: 46 healthy, 21 cuff tear arthropathy (CTA), 18 irreparable rotator cuff tear (IRCT), and 17 primary osteoarthritis (OA). The four rotator cuff muscles were manually segmented and their volume, including intramuscular fat, was calculated. The normalized volume (NV) of each muscle was calculated by dividing muscle volume to the patient’s scapular bone volume. Muscle volume and percentage of muscle atrophy were compared between muscles and between cohorts.

Results

Rotator cuff muscle volume was significantly decreased in patients with OA, CTA, and IRCT compared to healthy patients (p < 0.0001). Atrophy was comparable for all muscles between CTA, IRCT, and OA patients, except for the supraspinatus, which was significantly more atrophied in CTA and IRCT (p = 0.002). In healthy shoulders, the anterior cuff represented 45% of the entire cuff, while the posterior cuff represented 40%. A similar partition between anterior and posterior cuff was also found in both CTA and IRCT patients. However, in OA patients, the relative volume of the anterior (42%) and posterior cuff (45%) were similar.

Conclusion

This study shows that rotator cuff muscle volume is significantly decreased in patients with OA, CTA, or IRCT compared to healthy patients, but that only minimal differences can be observed between the different pathological groups. This suggests that the influence of rotator cuff muscle volume and atrophy (including intramuscular fat) as an independent factor of outcome may be overestimated.

Cite this article: Bone Jt Open 2021;2(7):552–561.

Trunk Muscle Characteristics: Differences Between Sedentary Adults With and Without Unilateral Lower Limb Amputation

OBJECTIVE

The primary purpose of this study was to compare trunk muscle characteristics between adults with and without unilateral lower limb amputation (LLA) to determine the presence of modifiable trunk muscle deficits (ie, impaired activity, reduced volume, increased intramuscular fat) evaluated by ultrasonography (US) and magnetic resonance imaging (MRI). We hypothesized that compared with adults without LLA (controls), individuals with transfemoral or transtibial LLA would demonstrate reduced multifidi activity, worse multifidi and erector spinae morphology, and greater side-to-side trunk muscle asymmetries.

DESIGN

Cross-sectional imaging study.

SETTING

Research laboratory and imaging center.

PARTICIPANTS

Sedentary adults (n=38 total) with LLA (n=9 transfemoral level; n=14 transtibial level) and controls without LLA (n=15).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

We examined bilateral multifidi activity using US at levels L3/L4-L5/S1. MRI was performed using 3-dimensional quantitative fat-water imaging; bilateral L1-L5 multifidi and erector spinae were manually traced, and muscle volume (normalized to body weight) and percentage intramuscular fat were determined. Between-group and side-to-side differences were evaluated.

RESULTS

Compared with adults without LLA, participants with LLA demonstrated reduced sound-side multifidi activity; those with transfemoral LLA had larger amputated-side multifidi volume, whereas those with transtibial LLA had greater sound- and amputated-side erector spinae intramuscular fat (P<.050). With transfemoral LLA, side-to-side differences in erector spinae volume, as well as multifidi and erector spinae intramuscular fat, were found (P<.050).

CONCLUSIONS

Impaired trunk muscle activity and increased intramuscular fat may be modifiable targets for intervention after LLA.

Clinical Y-view versus 3-dimensional assessments of intramuscular fat in patients with full-thickness rotator cuff tears

RATIONALE AND OBJECTIVES

Recent evidence suggests an inhomogeneous distribution of intramuscular rotator cuff fat infiltration (FI) in a small sample of individuals with rotator cuff tears, yet clinically just a few slices at the scapular Y-view are used to evaluate FI in patients with rotator cuff tears. The purpose of this study was to determine if assessment of FI using the scapular Y-view is representative of the entire muscle in patients with full-thickness rotator cuff tears, and whether this varies by tear size.

MATERIALS AND METHODS

Patients (N = 25) diagnosed with full-thickness rotator cuff tear and confirmed with magnetic resonance imaging (MRI) were included. Fat-water sequences were used to objectively quantify mean FI (%) in the entire 3D muscle and the mean from 3 slices at the Y-view. Mixed-model 2 × 2 ANOVAs were used to assess for differences between methods, and if results vary by tear-size.

RESULTS

There were no statistically significant differences between mean amount of FI of the entire 3D muscle and mean Y-view in the supraspinatus or infraspinatus muscles (p > 0.05). Additionally, this did not differ across tear size groups (p > 0.05).

CONCLUSION

Results of this study suggest FI assessed in the Y-view is not different (mean difference < 1.0%) from FI of the entire 3D muscle in patients with full-thickness rotator cuff tears. Therefore, the clinical utility of evaluating rotator cuff intramuscular fat infiltration with the Y-view is further supported in patients with full-thickness rotator cuff tears across tear sizes.

Volumetric MicroCT Intensity Histograms of Fatty Infiltration Correlate with the Mechanical Strength of Rotator Cuff Repairs: An Ex Vivo Rabbit Model

BACKGROUND

Fatty infiltration of the rotator cuff occurs after injury to the tendon and results in a buildup of adipose in the muscle. Fatty infiltration may be a biomarker for predicting future injuries and mechanical properties after tendon repair. As such, quantifying fatty infiltration accurately could be a relevant metric for determining the success of tendon repairs. Currently, fatty infiltration is quantified by an experienced observer using the Goutallier or Fuchs staging system, but because such score-based quantification systems rely on subjective assessments, newer techniques using semiautomated analyses in CT and MRI were developed and have met with varying degrees of success. However, semiautomated analyses of CT and MRI results remain limited in cases where only a few two-dimensional slices of tissue are examined and applied to the three-dimensional (3-D) tissue structure. We propose that it is feasible to assess fatty infiltration within the 3-D volume of muscle and tendon in a semiautomated fashion by selecting anatomic features and examining descriptive metrics of intensity histograms collected from a cylinder placed within the central volume of the muscle and tendon of interest.

QUESTIONS/PURPOSES

(1) Do descriptive metrics (mean and SD) of intensity histograms from microCT images correlate with the percentage of fat present in muscle after rotator cuff repair? (2) Do descriptive metrics of intensity histograms correlate with the maximum load during mechanical testing of rotator cuff repairs?

METHODS

We developed a custom semiautomated program to generate intensity histograms based on user-selected anatomic features. MicroCT images were obtained from 12 adult female New Zealand White rabbits (age 8 to 12 months, weight 3.7 kg ± 5 kg) that were randomized to surgical repair or sham repair of an induced infraspinatus defect. Intensity histograms were generated from images of the operative and contralateral intact shoulder in these rabbits which were presented to the user in a random order without identifying information to minimize sources of bias. The mean and SD of the intensity histograms were calculated and compared with the total percentage of the volume threshold as fat. Patterns of fat identified were qualitatively compared with histologic samples to confirm that thresholding was detecting fat. We conducted monotonic tensile strength-to-failure tests of the humeral-infraspinatus bone-tendon-muscle complex, and evaluated associations between histogram mean and SDs and maximum load.

RESULTS

The total percentage of fat was negatively correlated with the intensity histogram mean (Pearson correlation coefficient -0.92; p < 0.001) and positively with intensity histogram SD (Pearson correlation coefficient 0.88; p < 0.001), suggesting that the increase in fat leads to a reduction and wider variability in volumetric tissue density. The percentage of fat content was also negatively correlated with the maximum load during mechanical testing (Pearson correlation coefficient -78; p = 0.001), indicating that as the percentage of fat in the volume increases, the mechanical strength of the repair decreases. Furthermore, the intensity histogram mean was positively correlated with maximum load (Pearson correlation coefficient 0.77; p = 0.001) and histogram SD was negatively correlated with maximum load (Pearson correlation coefficient -0.72; p = 0.004). These correlations were strengthened by normalizing maximum load to account for animal size (Pearson correlation coefficient 0.86 and -0.9, respectively), indicating that as histogram mean decreases, the maximum load of the repair decreases and as histogram spread increases, the maximum load decreases.

CONCLUSION

In this ex vivo rabbit model, a semiautomated approach to quantifying fat on microCT images was a noninvasive way of quantifying fatty infiltration associated with the strength of tendon healing.

CLINICAL RELEVANCE

Histogram-derived variables may be useful as surrogate measures of repair strength after rotator cuff repair. The preclinical results presented here provide a foundation for future studies to translate this technique to patient studies and additional imaging modalities. This semiautomated method provides an accessible approach to quantification of fatty infiltration by users of varying experience and can be easily adapted to any intensity-based imaging approach. To translate this approach to clinical practice, this technique should be calibrated for MRI or conventional CT imaging and applied to patient scans. Further investigations are needed to assess the correlation of volumetric intensity histogram descriptive metrics to clinical mechanical outcomes.

Ultrasound shear wave elastography and its association with rotator cuff tear characteristics

Background

Approximately 20-60% of rotator cuff repairs fail with higher failure rates in patients with larger or more chronic tears. Although MRI provides an objective estimate of tear size, it can only provide qualitative descriptions of tear chronicity. By contrast, ultrasound shear wave elastography (SWE) may assess tear chronicity by estimating tissue mechanical properties (ie, shear modulus). Furthermore, SWE imaging does not share many of the challenges associated with MRI (eg, high cost, risk of claustrophobia). Therefore, the objective of this study was to determine the extent to which estimated supraspinatus shear modulus is associated with conventional MRI-based measures of rotator cuff tear size and chronicity.

Methods

Shear modulus was estimated using ultrasound SWE in two regions of the supraspinatus (intramuscular tendon, muscle belly) under two contractile conditions (passive, active) in 22 participants with full-thickness rotator cuff tears. The extent to which estimated supraspinatus shear modulus is associated with conventional MRI measures of tear size and chronicity was assessed using correlation coefficients and Kruskal-Wallis tests, as appropriate.

Results

Estimated shear modulus was not significantly associated with anterior/posterior tear size (P > .09), tear retraction (P > .20), occupation ratio (P > .11), or fatty infiltration (P > .30) under any testing condition.

Discussion

Although ultrasound SWE measurements have been shown to be altered in the presence of various tendinopathies, the findings of this study suggest the utility of ultrasound SWE in this population (ie, patients with a small to medium supraspinatus rotator cuff tear) before surgical rotator cuff repair remains unclear.

New quantified measurement of fatty infiltration of the rotator cuff muscles using magnetic resonance imaging

BACKGROUND

The degree of fatty infiltration of the rotator cuff muscle is typically evaluated using the Goutallier-Fuchs grading system, but its consistency remains controversial. This study aimed to evaluate a new quantified measurement of fatty infiltration based on three-dimensionally reconstructed volumetric data obtained from magnetic resonance images of non-pathologic shoulders using open-source software.

METHODS

Fourteen shoulder 3-T magnetic resonance images (8 men, 6 women) without lesions obtained between 2010 and 2017 were analysed. Slicer version 4.6.2 was used to semi-automatically reconstruct the three-dimensional volumetric data from T2 sagittal oblique images and to differentiate fat tissue from rotator cuff muscle using the difference in signal intensity.

RESULTS

The cutoff value for dividing muscle and fat was 508.9. The inter-class and intra-class correlations of each rotator cuff muscle and fat tissue were >0.9 (all P < 0.001). The mean muscle volume of the supraspinatus, infraspinatus, teres minor, and subscapularis were 15.2, 20.9, 13.3, and 29.7 mL, respectively. The muscle volume of the men was greater than that of the women (all P < 0.001), and the fat infiltration ratio was positively correlated with body mass index (all P < 0.05).

CONCLUSIONS

The semi-automated quantified measurement of fatty infiltration of the rotator cuff muscles using magnetic resonance imaging and Slicer software presented excellent consistency. This technique could be an alternative measurement to complement the weak consistency of the Goutallier-Fuchs grading system. However, to reduce the error of measurement, this study evaluated non-pathologic shoulders. Therefore, further study using magnetic resonance imaging of pathologic shoulders is necessary for actual clinical application.

LEVEL OF EVIDENCE

Level IV, case series, diagnostic study.

MRI in Neuromuscular Diseases: An Emerging Diagnostic Tool and Biomarker for Prognosis and Efficacy

There is an unmet need to identify biomarkers sensitive to change in rare, slowly progressive neuromuscular diseases. Quantitative magnetic resonance imaging (MRI) of muscle may offer this opportunity, as it is noninvasive and can be carried out almost independent of patient cooperation and disease severity. Muscle fat content correlates with muscle function in neuromuscular diseases, and changes in fat content precede changes in function, which suggests that muscle MRI is a strong biomarker candidate to predict prognosis and treatment efficacy. In this paper, we review the evidence suggesting that muscle MRI may be an important biomarker for diagnosis and to monitor change in disease severity. ANN NEUROL 2020;88:669-681.

The Role of Imaging Biomarkers in the Assessment of Sarcopenia

BACKGROUND

The diagnosis of sarcopenia through clinical assessment has some limitations. The literature advises studies that include objective markers along with clinical assessment in order to improve the sensitivity and specificity of current diagnostic criteria. The decrease of muscle quality precedes the loss of quantity, so we studied the role magnetic resonance imaging biomarkers as indicators of the quantity and quality of muscle in sarcopenia patients.

METHODS

a cross-sectional analysis was performed to analyze what MR-derived imaging parameters correlate better with sarcopenia diagnostic criteria in women of 70 years of age and over (independent walking and community-dwelling women who were sarcopenic in accordance with EWGSOP criteria with muscle mass adjusted to Spanish population were chosen).

RESULTS

The study included 26 women; 81 ± 8 years old. A strong correlation was obtained between cineanthropometric variables (BMI; thigh perimeter and fat mass) and imaging biomarkers (muscle/fat ratio, fatty infiltration, muscle T2*, water diffusion coefficient, and proton density fat fraction) with coefficients around 0.7 (absolute value).

CONCLUSIONS

Knowing the correlation of clinical parameters and imaging-derived muscle quality indicators can help to identify older women at risk of developing sarcopenia at an early stage. This may allow taking preventive actions to decrease disability, morbidity, and mortality in sarcopenia patients.

Threshold-based quantification of fatty degeneration in the supraspinatus muscle on MRI as an alternative method to Goutallier classification and single-voxel MR spectroscopy

Background

Conventional fat quantification methods for rotator cuff muscles have various limitations, such as inconsistent reliabilities of the Goutallier grades and need for advanced techniques in quantitative MRI sequences. We aimed to examine a threshold-based fat quantification method in the supraspinatus muscle on standard T1-weighted MR images and compare the threshold-based method with Goutallier grades and MR spectroscopy.

Methods

We retrospectively examined 38 symptomatic patients, who underwent T1 and T2-weighted fast spin-echo MR imaging and a single voxel spin-echo MR spectroscopy. The supraspinatus muscle and fossa were manually segmented in T1-weighted sagittal images and clustering-based thresholding was applied to quantify the fat fractions in the segmented areas using custom MATLAB software. Threshold-based fat fractions were compared with the Goutallier grades and MR spectroscopy fat/water ratios. A one-way analysis of variance and Pearson correlation were tested in the MATLAB software.

Results

Inter-observer reliability of threshold-based fat fractions for the supraspinatus muscle and fossa were 0.977 and 0.990 respectively, whereas the reliability of the Goutallier grading was 0.798. Threshold-based fat fractions in the supraspinatus fossa were significantly different between various Goutallier grades (one-way ANOVA, p < 0.001). Threshold-based fat fractions in the supraspinatus muscle strongly correlated with the MR spectroscopy fat/water ratio (Pearson correlation R-square = 0.83).

Conclusions

Threshold-based fat quantification on standard T1-weighted MR images was highly reliable and produced comparable results to conventional Goutallier grades and MR spectroscopy fat/water ratios and could serve as an alternative method for accurate fat quantification in rotator cuff muscles.

Lipid is heterogeneously distributed in muscle and associates with low radiodensity in cancer patients

BACKGROUND

Low muscle radiodensity is associated with mortality in a variety of cancer types. Biochemical and morphological correlates are unknown. We aimed to evaluate triglyceride (TG) content and location as a function of computed tomography (CT)-derived measures of skeletal muscle radiodensity in cancer patients.

METHODS

Rectus abdominis (RA) biopsies were collected during cancer surgery from 75 patients diagnosed with cancer. Thin-layer chromatography and gas chromatography were used for quantification of TG content of the muscle. Axial CT images of lumbar vertebra were used to measure muscle radiodensity. Oil Red O staining was used to determine the location of neutral lipids in frozen muscle sections.

RESULTS

There was wide variation in RA radiodensity in repeated measures (CV% ranged from 3 to 55% based on 10 serial images) as well as within one slice (CV% ranged from 6 to 61% based on 10 subregions). RA radiodensity and total lumbar muscle radiodensity were inversely associated with TG content of RA (r = -0.396, P < 0.001, and r = -0.355, P = 0.002, respectively). Of the total percentage area of muscle staining positive for neutral lipid, 54 ± 17% was present as extramyocellular lipids (range 23.5-77.8%) and 46 ± 17% (range 22.2-76.5%) present as intramyocellular lipid droplets.

CONCLUSIONS

Repeated measures revealed wide variation in radiodensity of RA muscle, both vertically and horizontally. Low muscle radiodensity reflects high level of TG in patients with cancer. Non-uniform distribution of intramyocellular and extramyocellular lipids was evident using light microscopy. These results warrant investigation of mechanisms resulting in lipid deposition in muscles of cancer patients.

Fat quantification of multifidus muscle using T2-weighted Dixon: which measurement methods are best suited for revealing the relationship between fat infiltration and herniated nucleus pulposus

OBJECTIVE

To reveal the best-suited method for fat quantification of lumbar multifidus to demonstrate its relationship to herniated nucleus pulposus (HNP) using T2-weighted Dixon.

MATERIALS AND METHODS

One hundred eight patients who underwent MRI for low back pain were enrolled. Two readers independently analyzed the fat fraction (Ff) using axial two-dimensional (D), coronal 2-D, and coronal 3-D measurement. Pearson's correlation coefficient was calculated between age, body mass index (BMI), and the Ff, and age, sex, BMI, and Ff were compared between 'HNP group' and 'no HNP group'. Multivariate logistic regression analysis was performed to identify factors associated with HNP.

RESULTS

Coronal 2-D Ff showed the highest correlation with age (r = 0.536, P < 0.001). Coronal 2-D Ff, and coronal 3-D Ff were significantly higher in those with HNP (coronal 2-D: 18.9 ± 2.9, coronal 3-D: 19.7 ± 2.6, respectively) than those without HNP (coronal 2-D: 17.2 ± 3.2, coronal 3-D: 17.4 ± 3.2, respectively). Ff of all three measurements were significantly higher in those with HNP ≥ 3 levels (axial 2-D: 20.7 ± 3.0, coronal 2-D: 21.1 ± 2.7, coronal 3-D: 21.6 ± 2.5, respectively) than those with HNP <3 levels (axial 2-D: 17.5 ± 4.3, coronal 2-D: 18.5 ± 2.7, coronal 3-D: 19.3 ± 2.5). The BMI was an independent predisposing factor to HNP (P = 0.011). Age and coronal 2-D Ff were significant predictors for multilevel HNP (P = 0.028 and 0.040, respectively).

CONCLUSIONS

The Ff of the multifidus muscle on T2-weighted Dixon was associated with age, sex, and HNP. The coronal 2-D measurement was the best suited for fat quantification in multifidus muscle among three measurement methods.

ASSOCIATION BETWEEN BODY COMPOSITION AND FAT INFILTRATION IN THE LUMBAR MULTIFIDUS IN YOUNG ADULTS

ABSTRACT Introduction: The increase in body fat is a natural and progressive process with aging, allowing fat infiltration in ectopic sites, such as skeletal muscle, which disrupts its function. Objective: To evaluate the association between body composition, fat infiltration into the low back multifidus muscles, and history of low back pain. Methods: This is a transversal and qualitative study that included young adult subjects of both sexes, and excluded individuals with neurological and musculoskeletal disorders and pregnant women. Fat infiltration into the multifidus and cross section area by magnetic resonance imaging; body composition by Dual-energy X-ray absorptiometry (DXA), and physical activity level determined by the International Physical Activity Questionnaire (IPAQ) were evaluated. The sample was divided by sex and. Pearson and Spearman's correlation and stepwise linear regression were performed. For this study, a p<0.05, a level of significance of 5% and confidence interval of 95% were adopted. Results: Thirty-two individuals were evaluated (59.37% women; 40.63% men). There was a correlation between fat percentage and total cross-sectional area (CSAtotal) (r=0.525; p=0.021), in women, and with lean abdominal mass (r= −0.648; p=0.017) and Body Mass Index (BMI) (r= −0.644; p=0.018) in men. There was also an association, in women, between fat percentage and cross section area (R2=0.275; p=0.021; CI=0.364 − 3.925) and, in men, with lean abdominal mass (R2=0.420; p=0.017; CI: −9.981- [-1.235]). Conclusion: There was correlation between fat percentage in the multifidus and CSA in women, and lean abdominal mass and BMI in men. There was also an association between fat percentage and cross section area in women, and lean abdominal mass in men. However, there was no evidence of any correlation between pain and low back dysfunction. Level of evidence I; Diagnostic studies - Investigating a diagnostic test.

Relation of Superficial and Deep Layers of Delaminated Rotator Cuff Tear to Supraspinatus and Infraspinatus Insertions

BACKGROUND

It remains unclear whether the deep layer of the rotator cuff is an articular layer of the supraspinatus (SS) or infraspinatus (IS), rotator cable, or superior capsule. Therefore, this study aimed to analyse the relationship between occupation ratios and delamination patterns of rotator cuff tears (RCTs). We hypothesised that the deep layers are related to the occupation ratios of the deep SS and IS sections.

MATERIALS AND METHODS

A total of 265 patients with RCTs were retrospectively enrolled between 2013 and 2017 and divided into four groups: A, non-delaminated tear; B, delaminated tear with the deep layer equally retracted to the superficial layer; C, delaminated tear with the deep layer more retracted; D, delaminated tear with the superficial layer more retracted. Muscle volume was evaluated by measurement of each occupation ratio of the SS and IS, and the IS muscle was additionally divided into two areas, deep and superficial.

RESULTS

The SS occupation ratio was significantly lower in group C than in the other groups (p = 0.009). Conversely, comparison of the IS occupation ratios revealed no significant intergroup differences. The occupation ratio of the superficial IS was significantly lower in group D than in the other groups (p = 0.003). In group C, the occupation ratios of the deep IS section were significantly decreased according to RCT size (p = 0.034).

CONCLUSION

Our findings demonstrate that the superficial layers are related to the IS superficial section and the deep layers to the SS and IS deep sections.

LEVEL OF STUDY

IV.

Restoration of supraspinatus and infraspinatus deep plane occupation ratios was greater in delaminated tears than in non-delaminated tears after rotator cuff repair

Total 132 patients who underwent arthroscopic suture bridge repair were divided into two groups: group A, non-delaminated tears; group B, deep layer, more retracted, delaminated tears. In addition, group B were divided into two subgroups: group I (≤2-cm) and group II (>2-cm). Muscle volume was evaluated by measuring the occupation ratio and restoration of the rotator cuff muscle was defined as the difference between the preoperative and postoperative occupation ratios. The restoration of the SS and IS deep plane occupation ratios was greater in >2-cm-sized delaminated tears than in ≤2-cm-sized delaminated and non-delaminated tears.

Automated postoperative muscle assessment of hip arthroplasty patients using multimodal imaging joint segmentation

BACKGROUND AND OBJECTIVE

In patients treated with hip arthroplasty, the muscular condition and presence of inflammatory reactions are assessed using magnetic resonance imaging (MRI). As MRI lacks contrast for bony structures, computed tomography (CT) is preferred for clinical evaluation of bone tissue and orthopaedic surgical planning. Combining the complementary information of MRI and CT could improve current clinical practice for diagnosis, monitoring and treatment planning. In particular, the different contrast of these modalities could help better quantify the presence of fatty infiltration to characterise muscular condition and assess implant failure. In this work, we combine CT and MRI for joint bone and muscle segmentation and we propose a novel Intramuscular Fat Fraction estimation method for the quantification of muscle atrophy.

METHODS

Our multimodal framework is able to segment healthy and pathological musculoskeletal structures as well as implants, and develops into three steps. First, input images are pre-processed to improve the low quality of clinically acquired images and to reduce the noise associated with metal artefact. Subsequently, CT and MRI are non-linearly aligned using a novel approach which imposes rigidity constraints on bony structures to ensure realistic deformation. Finally, taking advantage of a multimodal atlas we created for this task, a multi-atlas based segmentation delineates pelvic bones, abductor muscles and implants on both modalities jointly. From the obtained segmentation, a multimodal estimation of the Intramuscular Fat Fraction can be automatically derived.

RESULTS

Evaluation of the segmentation in a leave-one-out cross-validation study on 22 hip sides resulted in an average Dice score of 0.90 for skeletal and 0.84 for muscular structures. Our multimodal Intramuscular Fat Fraction was benchmarked on 27 different cases against a standard radiological score, showing stronger association than a single modality approach in a one-way ANOVA F-test analysis.

CONCLUSIONS

The proposed framework represents a promising tool to support image analysis in hip arthroplasty, being robust to the presence of implants and associated image artefacts. By allowing for the automated extraction of a muscle atrophy imaging biomarker, it could quantitatively inform the decision-making process about patient's management.

The supraspinatus occupation ratios of both the ≥ 50% articular- and bursal-side partial-thickness rotator cuff tears were low and the infraspinatus occupation ratio of the ≥ 50% bursal-side partial-thickness rotator cuff tears was low

PURPOSE

The purpose of this study was to analyze the relationship between the occupation ratio and partial-thickness rotator cuff tears.

METHODS

The study included and retrospectively investigated 683 patients with partial-thickness rotator cuff tears between 2013 and 2017. Fifty patients with impingement syndrome were also enrolled as the control group for normal-population comparison. The participants were divided into five groups: Group A, control group; Group B, < 50% articular-side tears; Group C, ≥ 50% articular-side tears; Group D, < 50% bursal-side tears; and Group E, ≥ 50% bursal-side tears. Muscle volume was evaluated by measurement of each occupation ratio of the supraspinatus and infraspinatus tendons on the most lateral view of the T1-weighted oblique-sagittal images in which the scapular spine remained in contact with the scapular body.

RESULTS

Fifty patients were enrolled in Group A. A total of 683 patients with Partial thickness rotator cuff tear were divided and classified into the following groups: 272 into Group B, 153 into Group C, 161 into Group D, and 97 into Group E. The supraspinatus occupation ratios of all partial-thickness rotator cuff tear groups were significantly lower than those of the control group. Furthermore, the supraspinatus occupation ratios of Groups C and E (≥ 50% partial-thickness rotator cuff tears) were significantly lower than those of Groups B and D (< 50% partial-thickness rotator cuff tears). However, the infraspinatus occupation ratio of only Group E was significantly lower than that of the other groups.

CONCLUSION

The supraspinatus occupation ratios of both the ≥ 50% articular- and bursal-side partial-thickness rotator cuff tears were lower than those of the other partial-thickness rotator cuff tears. Conversely, the infraspinatus occupation ratio of only the ≥ 50% bursal-side partial-thickness rotator cuff tears was low.

LEVEL OF EVIDENCE

IV.

Changes of Supraspinatus Muscle Volume and Fat Fraction After Successful or Failed Arthroscopic Rotator Cuff Repair

BACKGROUND

Muscle atrophy and fatty infiltration are limiting factors for successful rotator cuff (RC) repair. Quantitative data regarding these hallmarks of degenerative muscle changes after RC repair in humans are scarce. By utilizing a new application of the 6-point Dixon magnetic resonance imaging technology, 3-dimensional volume and fat fraction analysis of the whole RC muscle have become possible.

PURPOSE

Quantitative analysis of atrophy and fatty infiltration of the supraspinatus muscle after healed and failed RC tendon-to-bone repair.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Muscle volume and fat fraction were measured preoperatively and at 3 and 12 months postoperatively in 19 failed and 21 healed arthroscopic supraspinatus tendon repairs, with full muscle volume segmentation and magnetic resonance Dixon sequences.

RESULTS

In both groups, the muscle volume initially decreased 3 months after RC repair by -3% in intact (P = .140) and -10% in failed repair (P = .004) but recovered between 3 and 12 months to 103% (P = .274) in intact and 92% (P = .040) in failed repairs when compared with the preoperative volume (difference of change between groups, preoperative to 12 month: P = .013). The supraspinatus muscle's fat fraction did not significantly change after successful repair (6.5% preoperative, 6.6% after 3 months, and 6.7% after 12 months; all nonsignificant). There was, however, a significant increase from 7.8% to 10.8% at 3 months (P = .014) and 11.4% at 12 months (P = .020) after failed repair (difference between groups at 3- and 12-month follow-up: P = .018 and P = .001, respectively).

CONCLUSION

After successful arthroscopic repair, RC tendon tear-induced fatty infiltration can be almost stopped, and muscle atrophy can even be slightly reversed. In case of a failed repair, however, these changes are further pronounced during the first 3 postoperative months but seem to stabilize thereafter.

All-arthroscopic glenoid reconstruction by iliac crest bone graft transfer does not affect structural integrity and 3-dimensional volume of the subscapularis muscle

AIM

The subscapularis muscle is an important active stabilizer of the glenohumeral joint. For this radiological study, we investigated if its radiological integrity is affected after arthroscopic glenoid reconstruction. In the technique used, an autologous iliac crest graft is transported through the rotator interval, and the graft is fixed via an antero-inferior portal with compression screws.

METHODS

3 women and 6 men (mean age 31 ± 9 years, min 21, max 46 years) who had a preoperative glenoid deficit of 23% ± 6% (min 13%, max 29%) were included. In a follow-up after an interval of 34 months (min 19, max 50), MRI scans were performed on both shoulders. With ITK-SNAP, a 3D reconstruction software, the volume of the subscapularis muscle in the injured and contralateral shoulder was measured. In addition, signal intensity ratios (PSI) (infraspinatus muscle / cranial subscapularis muscle and infraspinatus muscle / caudal subscapularis muscle) were analyzed and the width of the cranial and caudal portions as well as the length of the subscapularis muscle in the parasagittal plane were determined.

RESULTS

The 3D volume showed no difference between operated and healthy shoulders (p = 0.07), neither did PSI ratios (infraspinatus muscle / cranial subscapularis muscle: p = 1.00, infraspinatus muscle / caudal subscapularis muscle: p = 1.00). In the parasagittal plane, length (p = 0.09) and cranial width (p = 0.23) did not differ. However, the width of the lower muscle was increased in injured shoulders (p = 0.02).

CONCLUSION

In this cohort, no relevant volume loss could be found after arthroscopic glenoid reconstruction. However, a greater width of the lower muscle portion could be identified in the parasagittal plane as a possible indication of scarring.

Optimizing methods to quantify intramuscular fat in rotator cuff tears with normalization

OBJECTIVE

To determine which normalization method may best account for confounding individual factors, such as age or BMI, when quantifying fat infiltration on MRI in patients with rotator cuff tears, the effects of normalization using three different muscles (teres major; triceps brachii; teres minor) were compared.

METHODS

Thirty-seven consecutive patients diagnosed with rotator cuff pathology were included. MRI fat-water sequences were used to quantify rotator cuff intramuscular fat (%fat). Three reference muscles (teres major, triceps, teres minor) were used to derive normalized %fat. Relationships between intramuscular %fat and tear size, age, and BMI in each rotator cuff muscle, before and after normalization, were compared with Fisher transformations (α = 0.05).

RESULTS

Normalization with teres major ameliorated confounding relationships of age and BMI on rotator cuff %fat. In contrast, normalization with triceps maintained the confounding relationships between %fat and age in supraspinatus (p = 0.03) and infraspinatus/teres minor (p = 0.028). Normalization with teres minor maintained the confounding relationship between %fat and BMI in subscapularis (p = 0.039). Normalization with teres major best-maintained relationships between tear size and infraspinatus/teres minor %fat (p = 0.021). In contrast, normalization with triceps or teres minor eliminated all significant relationships with tear size.

CONCLUSIONS

Results of this pilot study suggest normalization to teres major using MRI-based %fat quantification methods can effectively control for individual factors, such as BMI or age, and may have utility in evaluating and monitoring rotator cuff fat infiltration attributed specifically to a tendon tear.

Development of 3D method to assess intramuscular spatial distribution of fat infiltration in patients with rotator cuff tear: reliability and concurrent validity

Background

Intramuscular fat infiltration is a critical factor in surgical decision-making and is the most important factor used to prognosticate surgical repair outcomes in patients with rotator cuff tears. Quantitative 3D assessment of total rotator cuff fat infiltration in patients with rotator cuff tears has been realized. However, a reproducible method to evaluate 3D spatial distribution of rotator cuff intramuscular fat has not been established. The objective of this study was to establish the reproducibility, change detectable beyond error, and concurrent validity of a semi-automated method to evaluate the 3D spatial distribution of fat infiltration and muscle volume in patients with rotator cuff tears.

Methods

Thirteen consecutive patients diagnosed with symptomatic rotator cuff pathology and 3.0 T MRI confirmation at a single center were included. Fat-water imaging was used to quantify 3D intramuscular fat (%fat) in sagittal oblique sequences and intramuscular spatial distribution with the semi-automated technique. Each rotator cuff muscle was manually segmented yielding %fat in four axial intramuscular quartile-regions (superior-inferior; Q1–4) and three sagittal (medial/ intermediate/ lateral) regions. Reliability and concurrent validity of %fat and whole muscle volume were calculated with intraclass correlation coefficients (ICC).

Results

Intra-rater reliability for intramuscular sagittal divisions (ICC = 0.93–0.99) and axial divisions (ICC = 0.78–0.99) was good/excellent. Inter-rater reliability for %fat (ICC = 0.82–0.99) and volume (ICC = 0.92–0.99) was good/excellent. Concurrent validity with commercialized software showed good/excellent agreement (ICC = 0.66–0.99).

Conclusions

A new semi-automated method to assess 3-dimensional intramuscular distribution of fat infiltration in patients with rotator cuff tears using advanced MR imaging demonstrates high intra and inter-rater reliability and good concurrent validity. Minimal detectable change thresholds established facilitate clinical interpretation for future clinical application of this technique to assess change and treatment efficacy in patients with rotator cuff tears.

Ankle strength, muscle size, and adipose content following unilateral tibiotalar arthrodesis

Tibiotalar arthrodesis is commonly used to treat end-stage ankle osteoarthritis. Post-operative impairments are often attributed to limited ankle motion. However, whether muscular deficits also exist, thereby potentially contributing to impairments, is unknown. This study aimed to identify post-operative deficits in ankle musculature by examining range of motion, strength (maximum isometric ankle joint torque), and leg composition (cross-sectional area of individual tissue types: bone, subcutaneous adipose, intramuscular adipose, muscle). Ten individuals with unilateral tibiotalar arthrodesis participated. Paired t-tests (p < 0.05) identified differences between the fused and contralateral, control limb. The results indicate that individuals with tibiotalar arthrodesis have profound losses of range of motion and strength. Across participants, range of motion in the fused limb was 53.5 ± 11.7%, 66.8 ± 6.3%, 38.2 ± 18.7%, 37.8 ± 13.6% less than the control for dorsiflexion, plantarflexion, inversion, and eversion, respectively. The largest strength deficit was in dorsiflexion, with the fused limb producing 47.2 ± 9.4% less torque than the control. The quantity and quality of muscle tissue was also negatively affected in individuals following tibiotalar arthrodesis. The total cross-sectional area of the fused limb was 11.4 ± 5.4% smaller than the control limb. This change was primarily due to the 16.1 ± 6.7% decrease in muscle cross-sectional area. However, intramuscular adipose was significantly increased. Although the posterior compartment demonstrated a significant decrease in cross-sectional area, when accounting for differences in total cross-sectional area, the relative sizes of the four muscle compartments were consistent between limbs. This cross-sectional study motivates longitudinal research examining muscular deficits and whether these deficits are reversible with exercise and rehabilitation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Surgical injury and repair of hip external rotators in THA via posterior approach: a three-dimensional MRI-evident quantitative prospective study

BACKGROUND

As one of the classical total hip arthroplasty (THA) approaches, the posterior approach is widely used. However, there is a lack of in-depth quantitative researches on the surgical-related injury to the hip external rotators. The purpose of this study is to quantificationally analyse the surgical injury of hip external rotators after posterior THA and explore the effect of the muscle repair on the muscle recovery using the MRI three-dimensional reconstruction technique combined with the clinical assessment.

METHODS

Sixty five patients were eligible to receive a unilateral cementless THA via the posterior approach. During operation, the piriformis tendon was reattached but it was not applicable for the internal obturator muscle. We performed three-dimensional MRI reconstruction of bilateral piriformis and internal obturator muscle along with clinical assessment preoperatively, 6, 12 and 52 weeks postoperatively.

RESULTS

Bilateral piriformis and internal obturator muscle were homogeneous preoperatively. Compared with the contralateral side, the volume atrophy and fat-muscle ratio of the piriformis on the operated side increased inconspicuously by 1.64%, 0.26% (p = 0.062, p = 0.071) at 6 weeks and 1.33%, 0.20% (p = 0.057, p = 0.058) at 12 weeks, while 7.28%, 2.09% and 15.71%, 5.14% for the internal obturator muscle (p < 0.01). Up to 52 weeks, the pirformis also showed significant muscle atrophy as well as fatty infiltration (increased by 7.79%, 4.21%; p < 0.01), and 24.18%, 11.91% for the internal obturator muscle (p < 0.01).

CONCLUSION

The THA via posterior approach significantly harms the hip external rotators and the early hip external rotation function. The effective repair could be conducive to the early postoperative recovery of the hip external rotators.

TRAIL REGISTRATION

The study has been registered in Chinese Clinical Trial Registry (ChiCTR) before the clical trial started, the Clinical Trial Registry Number is ChiCTR-IOR-17013007 . Registered 17 October 2017. The Trial registration is prospective registration.

Increasing the deltoid muscle volume positively affects functional outcomes after arthroscopic rotator cuff repair

PURPOSE

The aim of this study was to determine the effect of changes in deltoid muscle volume (DMV) on the clinical outcomes of patients who underwent arthroscopic repair due to chronic rotator cuff rupture.

METHODS

A total of 54 patients (35 females, 19 males) between 40 and 70 years of age who underwent single-row arthroscopic repair due to chronic rotator cuff tears were compared via preoperative (preop) and postoperative (postop) (6-12 months) magnetic resonance imaging (MRI) to determine the total DMV (tDMV). A clinical evaluation was performed with American Shoulder and Elbow Surgeons (ASES) and Constant scores in both the preop and postop groups. tDMV values were also measured in a randomly selected control group (50 patients). A standardized rehabilitation program was recommended for all patients.

RESULTS

Positive correlations were found between the change in tDMV (ΔtDMV) and ASES and Constant scores (p < 0.03 and p < 0.032, respectively). The preop tDMV value was significantly lower in the patient group than in the control group (p < 0.02). Significantly lower ΔtDMV and body mass index (BMI)-adjusted tDMV values [Δ(tDMV/BMI)] were observed in patients who had rerupture at the postop MRI.

CONCLUSIONS

According to the present study, changes in DMV impact clinical outcomes after rotator cuff repair. Rehabilitation of the DMV or increasing the preop DMV values positively affects postop clinical outcomes. In addition, if the DMV is below the cutoff value during the preop period, there is insufficient improvement in clinical scores. The clinical relevance of this study is the finding that in patients with a chronic rotator cuff tear and a hypotrophic deltoid muscle, increasing the preop DMV could help achieve better functional outcomes.

LEVEL OF EVIDENCE

Prognostic, Level 3, case-control study.

A novel diagnostic method to predict subscapularis tendon tear with sagittal oblique view magnetic resonance imaging

PURPOSE

To find novel measurement guidelines correlating with known tear size on two sagittal oblique views (en-face view and Y-view).

METHODS

From a series of arthroscopic rotator cuff repair cases between 2012 and 2015, 50 patients were randomly selected from each of six subscapularis tear classifications. Due to rarity of type IV lesions, 272 shoulders were included. En-face view and Y-view in sagittal plane MRI were selected. Image evaluation was retrospectively performed by two researchers independently. In en-face view, anatomical line connecting the coracoid tip to the glenoid base designated as the base-to-tip line was used for thickness measurement and classification. Grading according to base-to-tip line, overlapped segment of base-to-tip line, thickness of subscapularis, and fluid accumulation were measured. In Y-view, a tangent line was drawn through the scapular spine and the coracoid. Parallel lines were then made. Grading according to tangent line, vertical length, cephalic width, caudal width, and fluid accumulation was measured.

RESULTS

In en-face view, grading according to base-to-tip line and overlapped segment of base-to-tip line showed differences in subscapularis tendon tear types IIB, III, and IV compared to the normal group. Thickness of subscapularis showed differences in types III and IV. No significant difference was observed in fluid accumulation. In Y-view, grading according to tangent line, vertical length, cephalic width, and fluid accumulation showed significant differences in types III and IV. Caudal width in Y-view was significantly different only in type IV.

CONCLUSION

Several measurement parameters in two additional views in sagittal-oblique MRI (en-face view and Y-view) showed different degrees of subscapularis tendon tears. Grading of base-to-tip line is easy to use and helps diagnose partial subscapularis tear.

LEVEL OF EVIDENCE

III.