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

Developing a three-dimensional convolutional neural network for automated full-volume multi-tissue segmentation of the shoulder with comparisons to Goutallier classification and partial volume muscle quality analysis

BACKGROUND

Preoperative intramuscular fat (IMF) is a strong predictor of tendon failure after a rotator cuff repair. Due to the contemporary labor intensive and time-dependent manual segmentation required for quantitative assessment of IMF, clinical implementation remains a challenge. The emergence of accurate three-dimensional evaluation of the rotator cuff may permit implementation with greater inter-rater reliability than common subjective scales (eg, Goutallier classification (GC)). Here, we developed and validated a convolutional neural network (CNN) model for auto-segmentation of the shoulder on Dixon magnetic resonance imaging. Also, we aimed to assess the agreement among GC, two-dimensional (2D), and 3D IMF, including their discriminatory ability for the identification of muscles above an IMF threshold shown to negatively impact surgical outcomes (ie, GC ≥ 3).

METHODS

This study retrospectively obtained fat-water Dixon shoulder magnetic resonance imagings between March 2023 and March 2024 to develop and validate a CNN model for the segmentation of individual rotator cuff muscles and surrounding tissues. The CNN model was trained using a modified U-Net architecture (n = 80) and tested on an external dataset (n = 25). Accuracy was primarily evaluated using the Dice Similarity Coefficient (DSC) compared to manual segmentation. Reliability was evaluated by the intraclass correlation coefficient (ICC2,1) and discriminatory ability was evaluated by the area under the receiver operating characteristic curve.

RESULTS

The model after training (37 male and 43 female, mean age = 55.8 ± 15.6 years) and testing (15 male and 10 female, mean age = 56.6 ± 19.7 years) produced DSCs of ≥0.89 except for teres minor (DSC = 0.86 ± 0.03). The model demonstrated excellent reliability for volume (ICC2,1 ≥ 0.93) and good to excellent reliability for IMF (ICC2,1 ≥ 0.80), with the exceptions of teres major volume (ICC2,1 = 0.82, 95% CI: 0.63-0.92, P < .001) and subscapularis IMF (ICC2,1 = 0.55, 95% CI: 0.22-0.77, P < .001). 3D IMF but not 2D IMF was associated with GC for the supraspinatus, subscapularis, and infraspinatus (U ≥ 4.02, P < .045). The proposed CNN model's IMF outputs produced excellent discriminatory capability of muscles above the IMF threshold shown to negatively impact outcomes (receiver operating characteristic curve ≥0.93).

CONCLUSION

The development of a CNN model allows for efficient, accurate segmentation of muscle and bone, enabling reliable evaluation of muscle quality. The model demonstrates that 2D evaluation of IMF is insufficient for differentiating between rotator cuff muscles on either side of a clinically meaningful IMF threshold on the GC scheme, whereas 3D IMF shows excellent discriminant validity across all rotator cuff muscles.

3-Dimensional (3D) Isotropic MRI of the Shoulder - Advantages Over 2D MRI

The increasing implementation of high-field MRI scanners and the development of novel imaging techniques have rendered 3D imaging of joints more feasible and efficient than ever. This article describes the current state of 3D MRI of the shoulder and highlights the benefits of the technique over conventional 2D MRI with respect to shoulder derangements.

3D quantitative CT study to assess rotator cuff muscle fatty infiltration

Fatty infiltration is a degenerative condition of the tendon-muscle unit of rotator cuff muscles, characterized by fatty accumulation within and around the muscles. This study compares a 3D method to the Goutallier classification for evaluating fatty infiltration of the rotator cuff muscles. Employing a retrospective study design, four researchers performed 3D segmentation of the rotator cuff muscles on 65 CT scans of patients with rotator cuff arthropathy. The Goutallier classification was graded on screenshots of the Y view and two axial slices. Measurements, including HU, volume, cross-sectional area, and Goutallier grade, were performed on the 3D segmentations and the respective 2D slices. The inter- and intra-rater variability for 2D and 3D methods were calculated using the Intraclass Correlation Coefficient (ICC). The ICC for 2D and 3D methods was excellent (ICC: 0.90-0.95 and 0.81-0.99, respectively) and good for the Goutallier classification (ICC: 0.62-0.81). Overall, the relative 3D fatty infiltration was 0% for Goutallier grade 0 muscles, 7% for grade 1, 19% for grade 2, 33% for grade 3, and 37% for grade 4. The relative 2D fatty infiltration was 0%, 8%, 25%, 37%, and 43%, respectively. We conclude that 3D segmentation on CT scans is better reproducible and evaluates the muscle entirely. However, the time-intensive nature of the 3D method currently limits its clinical practicality. Quantitive 2D evaluation is excellently reproducible but may overestimate the actual fatty infiltration percentage of the whole muscle.

Systematic identification of aberrant non-coding RNAs and their mediated modules in rotator cuff tears

Background: Rotator cuff tears (RCT) is the most common cause of shoulder dysfunction, however, its molecular mechanisms remain unclear. Non-coding RNAs(ncRNAs), such as long ncRNA (lncRNA), microRNA (miRNA) and circular RNA (circRNA), are involved in a variety of diseases, but little is known about their roles in RCT. Therefore, the purpose of this study is to identify dysregulated ncRNAs and understand how they influence RCT.

Methods: We performed RNA sequencing and miRNA sequencing on five pairs of torn supraspinatus muscles and matched unharmed subscapularis muscles to identify RNAs dysregulated in RCT patients. To better comprehend the fundamental biological processes, we carried out enrichment analysis of these dysregulated mRNAs or the co-expressed genes of dysregulated ncRNAs. According to the competing endogenous RNA (ceRNA) theory, we finally established ceRNA networks to explore the relationship among dysregulated RNAs in RCT.

Results: A total of 151 mRNAs, 38 miRNAs, 20 lncRNAs and 90 circRNAs were differentially expressed between torn supraspinatus muscles and matched unharmed subscapularis muscles, respectively. We found that these dysregulated mRNAs, the target mRNAs of these dysregulated miRNAs or the co-expressed mRNAs of these dysregulated ncRNAs were enriched in muscle structure development, actin-mediated cell contraction and actin binding. Then we constructed and analyzed the ceRNA network and found that the largest module in the ceRNA network was associated with vasculature development. Based on the topological properties of the largest module, we identified several important ncRNAs including hsa_circ_0000722, hsa-miR-129-5p and hsa-miR-30c-5p, whose interacting mRNAs related to muscle diseases, fat and inflammation.

Conclusion: This study presented a systematic dissection of the expression profile of mRNAs and ncRNAs in RCT patients and revealed some important ncRNAs which may contribute to the development of RCT. Such results could provide new insights for further research on RCT.

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.

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.

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 insights into intrinsic foot muscle morphology and composition using ultra-high-field (7-Tesla) magnetic resonance imaging

Background

The intrinsic muscles of the foot are key contributors to foot function and are important to evaluate in lower limb disorders. Magnetic resonance imaging (MRI), provides a non-invasive option to measure muscle morphology and composition, which are primary determinants of muscle function. Ultra-high-field (7-T) magnetic resonance imaging provides sufficient signal to evaluate the morphology of the intrinsic foot muscles, and, when combined with chemical-shift sequences, measures of muscle composition can be obtained. Here we aim to provide a proof-of-concept method for measuring intrinsic foot muscle morphology and composition with high-field MRI.

Methods

One healthy female (age 39 years, mass 65 kg, height 1.73 m) underwent MRI. A T1-weighted VIBE – radio-frequency spoiled 3D steady state GRE – sequence of the whole foot was acquired on a Siemens 7T MAGNETOM scanner, as well as a 3T MAGNETOM Prisma scanner for comparison. A high-resolution fat/water separation image was also acquired using a 3D 2-point DIXON sequence at 7T. Coronal plane images from 3T and 7T scanners were compared. Using 3D Slicer software, regions of interest were manually contoured for each muscle on 7T images. Muscle volumes and percentage of muscle fat infiltration were calculated (muscle fat infiltration % = Fat/(Fat + Water) x100) for each muscle.

Results

Compared to the 3T images, the 7T images provided superior resolution, particularly at the forefoot, to facilitate segmentation of individual muscles. Muscle volumes ranged from 1.5 cm³ and 19.8 cm³, and percentage muscle fat infiltration ranged from 9.2–15.0%.

Conclusions

This proof-of-concept study demonstrates a feasible method of quantifying muscle morphology and composition for individual intrinsic foot muscles using advanced high-field MRI techniques. This method can be used in future studies to better understand intrinsic foot muscle morphology and composition in healthy individuals, as well as those with lower disorders.

Rotator cuff tear degeneration and the role of fibro-adipogenic progenitors

The high prevalence of rotator cuff tears poses challenges to individual patients and the healthcare system at large. This orthopedic injury is complicated further by high rates of retear after surgical repair. Outcomes following repair are highly dependent upon the quality of the injured rotator cuff muscles, and it is, therefore, crucial that the pathophysiology of rotator cuff degeneration continues to be explored. Fibro-adipogenic progenitors, a major population of resident muscle stem cells, have emerged as the main source of intramuscular fibrosis and fatty infiltration, both of which are key features of rotator cuff muscle degeneration. Improvements to rotator cuff repair outcomes will likely require addressing the muscle pathology produced by these cells. The aim of this review is to summarize the current rotator cuff degeneration assessment tools, the effects of poor muscle quality on patient outcomes, the role of fibro-adipogenic progenitors in mediating muscle pathology, and how these cells could be leveraged for potential therapeutics to augment current rotator cuff surgical and rehabilitative strategies.

Foot exercise plus education versus wait and see for the treatment of plantar heel pain (FEET trial): a protocol for a feasibility study

Background

Plantar heel pain (PHP) is present in a wide range of individuals and creates significant burden to quality of life and participation in physical activity. The high recurrence rates and persistence of PHP suggests current management options may not address all potentially modifiable factors associated with the condition. Reports of intrinsic foot muscle (IFM) atrophy in individuals with PHP, together with biomechanical evidence of their important contribution to optimal foot function, suggests that an intervention focused on IFM training may be beneficial in managing PHP. We will test the feasibility of a prospective, assessor-blinded, parallel-group, randomised clinical trial that compares foot exercise plus education to brief advice in individuals with PHP.

Methods

Twenty participants with PHP will be randomly allocated to one of two groups for a 12-week intervention period: (i) foot exercise plus education, or (ii) brief advice. The foot exercise plus education group will attend eight sessions with a physiotherapist and receive detailed education on self-management strategies as well as a progressive exercise program for the IFMs. The brief advice group will attend one session with a physiotherapist and receive brief information about self-management strategies and reassurance. Outcome measures will be obtained at baseline and the primary end-point of 12 weeks. Primary outcomes will be the feasibility of conducting a full-scale randomised clinical trial (RCT), and the credibility and acceptability of the foot exercise plus education intervention. Secondary outcomes will explore treatment effects, which will consist of pain, physical function, physical activity level, pain self-efficacy, perceived treatment effect, magnetic resonance and ultrasound image measurement of IFM morphology, ultrasound imaging measurement of plantar fascia thickness, IFM motor performance, foot posture, foot mobility, ankle dorsiflexion range of motion, toe flexor and plantar flexor strength/endurance.

Discussion

To reduce the burden of PHP on individuals and society, there is a need to establish effective treatments that are feasible and accepted by patients and health professionals. This trial will be the first to evaluate the feasibility of conducting a full-scale RCT, as well as the credibility, acceptability, and treatment effects, of education and foot exercise for PHP. The findings of this study will inform the development of a full-scale RCT.

Trial registration

The trial protocol was prospectively registered with the Australia and New Zealand Clinical Trial Registry (ACTRN12619000987167) on 11th July 2019.