Measuring myofascial shear strain in chronic shoulder pain with ultrasound shear strain imaging: a case report.

BACKGROUND: Dysfunctional gliding of deep fascia and muscle layers forms the basis of myofascial pain and dysfunction, which can cause chronic shoulder pain. Ultrasound shear strain imaging may offer a non-invasive tool to quantitatively evaluate the extent of muscular dysfunctional gliding and its correlation with pain. This case study is the first to use ultrasound shear strain imaging to report the shear strain between the pectoralis major and minor muscles in shoulders with and without chronic pain. CASE PRESENTATION: The shear strain between the pectoralis major and minor muscles during shoulder rotation in a volunteer with chronic shoulder pain was measured with ultrasound shear strain imaging. The results show that the mean ± standard deviation shear strain was 0.40 ± 0.09 on the affected side, compared to 1.09 ± 0.18 on the unaffected side (p<0.05). The results suggest that myofascial dysfunction may cause the muscles to adhere together thereby reducing shear strain on the affected side. CONCLUSION: Our findings elucidate a potential pathophysiology of myofascial dysfunction in chronic shoulder pain and reveal the potential utility of ultrasound imaging to provide a useful biomarker for shear strain evaluation between the pectoralis major and minor muscles.

The frequency of os acromiale in 751 shoulder MRI of Saudi population.

Background: Os acromiale (OA) is an uncommon pathology with a variable prevalence rate among different populations. Objectives: The aim of this study was to report the frequency of OA utilizing shoulder MRI of patients with shoulder pathology. Methods: It was a retrospective study. After obtaining our IRB approval, we gathered all shoulder and upper arm MRIs from the radiology department and evaluated them. Results: The prevalence of OA was found to be 3.32%. The mean age of the affected patients was 50.87 years (25-81). Conclusion: The rate of OA in patients presenting with shoulder pain is 3.32% in Saudi Arabia, which correlates with what has been previously reported in the literature.

Shoulder pathologies in CrossFit: a magnetic resonance imaging study of 51 cases.

BACKGROUND: Recent scientific work shows that the most common injuries in CrossFit© occur in the shoulder joint. This paper aims to provide a review of shoulder pathologies in a young CrossFit© cohort via MRI and clinical examination. METHODS: A survey was conducted in 13 CrossFit "boxes" in Germany, in which athletes with recurrent shoulder pain could report for a clinical examination and MRI diagnostic. Fifty-one CrossFit athletes with chronic shoulder pain agreed to participate in the study and were then examined physically and by MRI. RESULTS: Fifty-one active CrossFit athletes aged 21-45 years (mean 33.7 years, 35 male and 16 female) were recruited. The most frequently detected pathologies were partial lesions of the supraspinatus tendon (N.=25; 49%) and labral lesions (N.=11; 21.6%). The findings also identified partial lesions of the subscapularis tendon (N.=9; 17.6%), pulley lesions (N.=9; 17.6%), and partial lesions of the infraspinatus muscle (N.=2; 3.9%). CONCLUSIONS: These data demonstrate the need for a specific focus on particular shoulder injuries in CrossFit. Knowledge about the type of shoulder pathologies caused by CrossFit training allows for training-specific adaptations with regard to prevention, as well as a more targeted, sport-specific therapy. This study is the first in the literature to present on structural changes in the shoulders of active CrossFit athletes.

Effects of scapulo-humeral training on ultrasonographic and clinical evaluations in stroke: a randomized controlled trial.

BACKGROUND: After stroke, the effects of focused scapulo-humeral training with simultaneous assessment of the changes in shoulder subluxation, related muscle thicknesses and upper limb performance have not been studied in the literature. OBJECTIVES: This study aimed to investigate the effects of an 8-week scapulo-humeral training program in addition to conventional rehabilitation on upper extremity/trunk functions, shoulder pain, and sonographic measurements of the shoulder joint and periscapular muscles. METHODS: Thirty stroke individuals were randomly separated into two groups as Group I-scapulo-humeral training (5F/10 M) and Group II - control (5F/10 M). Conventional rehabilitation program was applied to both groups, and a scapulo-humeral training exercise protocol was added for the scapulo-humeral group. All the treatments were applied for 1 hour/day, 3 days/week, 8 weeks. Clinical evaluations were made using the Fugl Meyer Assessment-Upper Extremity(FMA-UE), Action Research Arm Test(ARAT), ABILHAND, Visual Analog Scale, and Trunk Impairment Scale(TIS). Ultrasound was used to measure serratus anterior/lower trapezius muscle thicknesses, and acromion-greater tubercule/acromio-humeral distances. RESULTS: FMA-UE, ARAT, ABILHAND and TIS scores increased in both groups, with greater increases in most parameters in the scapulo-humeral training group. Shoulder pain decreased only in the scapulo-humeral training group. Subacromial distances were decreased on the paretic side, and muscle thicknesses increased on both sides in the scapulo-humeral training group, and in the control group, only serratus anterior muscle thickness increased on the paretic side (p < 0.05 for all). CONCLUSIONS: Additional scapulo-humeral exercises to conventional rehabilitation was seen to improve upper extremity/trunk performance and shoulder pain, and to increase scapula stabilizer muscle thicknesses in stroke individuals with mild-moderate upper extremity disability.

Usefulness of Diagnostic Ultrasound for Detection of Common Shoulder Abnormalities Prior to MRI.

Shoulder pain is a common musculoskeletal pain in the general population and results in significant disability, quality of life impairment and financial burden to the health care system. This cross-sectional study was carried out among purposively selected 61 adult patients with shoulder pain and or limited range of motion in the Department of Radiology and Imaging, Mymensingh Medical College Hospital, Mymensingh, Bangladesh from September 2018 to August 2020 to determine the usefulness of USG in detection of common shoulder abnormalities, as an initial imaging modality using MRI as reference standard. The majority of the patients 25(40.98%) were in age group of 51-60 years with mean age of 52.98±10.85 years. In the dectection of rotator cuff pathology, the overall sensitivity, specificity and accuracy of USG for any complete tear were 100.0% each, for any partial tear were 79.71%, 96.57% and 91.80%, for any rotator cuff tear were 83.33%, 96.25% and 91.80%, and for any tendinosis were 90.48%, 99.37% and 96.31% respectively. The sensitivity, specificity and accuracy of USG were 88.23%, 92.59% & 90.16% for long head of biceps tendon sheath effusion, 100.0% each for long head of biceps tendon dislocation, 71.11%, 87.50% and 75.41% for glenohumeral joint effusion, and 58.06%, 96.67% and 77.05% for bursal effusion respectively. From this study, it is concluded that high resolution USG showed high sensitivity, specificity and accuracy compared to MRI in detecting common shoulder abnormalities, and could be considered as the first line imaging modality in the evaluation of shoulder pain.

Functional and Radiologic Outcomes of Degenerative Versus Traumatic Full-Thickness Rotator Cuff Tears Involving the Supraspinatus Tendon.

BACKGROUND: Arthroscopic rotator cuff repair (ARCR) is among the most commonly performed orthopaedic procedures. Several factors-including age, sex, and tear severity-have been identified as predictors for outcome after repair. The influence of the tear etiology on functional and structural outcome remains controversial. PURPOSE: To investigate the influence of tear etiology (degenerative vs traumatic) on functional and structural outcomes in patients with supraspinatus tendon tears. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Patients undergoing ARCR from 19 centers were prospectively enrolled between June 2020 and November 2021. Full-thickness, nonmassive tears involving the supraspinatus tendon were included. Tears were classified as degenerative (chronic shoulder pain, no history of trauma) or traumatic (acute, traumatic onset, no previous shoulder pain). Range of motion, strength, the Subjective Shoulder Value, the Oxford Shoulder Score (OSS), and the Constant-Murley Score (CMS) were assessed before (baseline) and 6 and 12 months after ARCR. The Subjective Shoulder Value and the OSS were also determined at the 24-month follow-up. Repair integrity after 12 months was documented, as well as additional surgeries up to the 24-month follow-up. Tear groups were compared using mixed models adjusted for potential confounding effects. RESULTS: From a cohort of 973 consecutive patients, 421 patients (degenerative tear, n = 230; traumatic tear, n = 191) met the inclusion criteria. The traumatic tear group had lower mean baseline OSS and CMS scores but significantly greater score changes 12 months after ARCR (OSS, 18 [SD, 8]; CMS, 34 [SD,18] vs degenerative: OSS, 15 [SD, 8]; CMS, 22 [SD, 15]) (P < .001) and significantly higher 12-month overall scores (OSS, 44 [SD, 5]; CMS, 79 [SD, 9] vs degenerative: OSS, 42 [SD, 7]; CMS, 76 [SD, 12]) (P≤ .006). At the 24-month follow-up, neither the OSS (degenerative, 44 [SD, 6]; traumatic, 45 [SD, 6]; P = .346) nor the rates of repair failure (degenerative, 14 [6.1%]; traumatic 12 [6.3%]; P = .934) and additional surgeries (7 [3%]; 7 [3.7%]; P = .723) differed between groups. CONCLUSION: Patients with degenerative and traumatic full-thickness supraspinatus tendon tears who had ARCR show satisfactory short-term functional results. Although patients with traumatic tears have lower baseline functional scores, they rehabilitate over time and show comparable clinical results 1 year after ARCR. Similarly, degenerative and traumatic rotator cuff tears show comparable structural outcomes, which suggests that degenerated tendons retain healing potential.

Clinical and ultrasound findings of 'swimmer's shoulder' and its association with training history in elite Portuguese swimmers: a cross-sectional study.

OBJECTIVES: To assess the prevalence of shoulder injuries and ultrasound findings in elite Portuguese swimmers and their association with symptoms and personal or training-related factors. METHODS: This cross-sectional study was conducted at the Portuguese Open and Youth Swimming National Championships between 27 and 30th July 2022. Each athlete entered details regarding personal and training history into a questionnaire and underwent a physical and ultrasound shoulder examination. RESULTS: A total of 102 swimmers out of 662 Portuguese athletes were included in the study. Shoulder pain experienced during the previous season was reported by 42% of the athletes. A high prevalence of shoulder structural abnormalities was noted, specifically supraspinatus tendinosis (91%), tears (29%), and subacromial bursitis (29%). Specific training for injury prevention was associated with higher rates of infraspinatus tendinosis (p = 0.047), and supraspinatus tears were linked to greater swimming distances per week (p < 0.001) and practice (p < 0.001), more years of practice (p = 0.018), shoulder pain at the time of evaluation (p = 0.023), a higher number of missed competitions (p = 0.041), and shoulder injections (p = 0.009). Subacromial bursitis was associated with shoulder pain at the time of evaluation (p = 0.002) and during the previous season (p < 0.001), missed competitions (p < 0.001), and requirement for physical therapy (p = 0.006). CONCLUSIONS: A high prevalence of shoulder morphological changes was found in surveyed swimmers and there were several associations with training load, regardless of individual characteristics of each athlete. It is essential to understand the true impact of current injury prevention programs and to develop effective measures to protect swimmers' health.

Does an Increase in Supraspinatus Tendon Thickness After Swimming Increase the Likelihood of Future Shoulder Pain?

BACKGROUND: Increase in supraspinatus tendon thickness (STT) resulting from swimming practice has been observed in those with a history of shoulder pain. The magnitude of change in STT after a swimming session and its rate of recovery may be an indicator of future shoulder pain incidence. HYPOTHESIS: The supraspinatus tendons that demonstrate a greater increase in thickness as a result of swimming practice will have an increased likelihood of future shoulder pain in a cohort of competitive swimmers over a period of 6 months. DESIGN: Descriptive epidemiology study. LEVEL OF EVIDENCE: Level 2b, individual cohort studies. METHODS: A cohort of 50 nationally qualified swimmers aged between 14 and 22 years, from 3 open National Swimming Programs in Victoria, Australia, were recruited for this study. Ultrasonographic measurements of swimmers' STT was obtained of both shoulders, before, immediately after, and 6 hours after a single swimming practice session. Data were recorded of any significant interfering shoulder pain at 3 and 6 months after the initial testing session. RESULTS: Stepwise logistic regression models indicated that significant predictors of the likelihood of experiencing significant interfering pain were sex [significant at 6 months; odds ratio (OR) 4.2] and the extent of change in STT immediately (OR 2.3 and 1.3 per mm at 3 and 6 months, respectively) and 6 hours postpractice (OR 1.9 and 1.5 per mm at 3 and 6 months, respectively). CONCLUSION: The current data suggest larger increases in tendon thickness after training are associated with an increased likelihood of future shoulder pain. CLINICAL RELEVANCE: These data may be valuable for monitoring training load and identifying athletes who may have an increased likelihood of shoulder pain.

Predictive Factors of Intra-articular Corticosteroid Injections With Ultrasound-Guided Posterior Capsule Approach for Patients With Primary Adhesive Capsulitis.

BACKGROUND: Adhesive capsulitis affects the shoulder joint, causing pain and limiting motion. In clinical practice, the effectiveness of injections varies, and the factors influencing their success remain unclear. This study investigates the predictors of effective corticosteroid injections in patients with primary adhesive capsulitis. DESIGN: This retrospective study enrolled adhesive capsulitis patients older than 35 yrs who received intra-articular corticosteroid injections. The response was determined based on patients' pain and range of motion 3 mos after the injection. Demographic data, medical comorbidities, and radiographic parameters (critical shoulder angle and acromial index) were compared between the effective and noneffective groups. Receiver operating characteristic curves and logistic regression were used to identify the predictors of injection effectiveness. RESULTS: This study included 325 patients with primary adhesive capsulitis, who were divided into responder (189 patients, 58.2%) and nonresponder (136 patients, 41.8%) groups. The receiver operating characteristic curve revealed that the acromial index score indicated favorable discrimination for predicting a poor response to injections, whereas the critical shoulder angle score did not. Logistic regression revealed that the pain period, diabetes mellitus, and acromial index are predictors of nonresponders to injections. CONCLUSIONS: Long pain duration, the presence of diabetes mellitus, and an acromial index score greater than 0.711 were predictors of nonresponse to corticosteroid injections for primary adhesive capsulitis patients.

Concordance of shoulder symptoms and imaging findings: a protocol for the Finnish Imaging of Shoulder (FIMAGE) study.

INTRODUCTION: Shoulder pain is a substantial medical and socioeconomic problem in most societies, affecting the ability to work or carry out leisure time activities as well as subsequently influencing physical and psychological well-being. According to a nationwide survey in Finland, 27% of the population reported shoulder pain within the last 30 days. In clinical practice, imaging findings of structural abnormalities are typically thought to explain symptoms, even though such findings are also prevalent in asymptomatic individuals, particularly with increasing age. Overall, there is a paucity of high-quality evidence on the prevalence, clinical relevance and prognosis of 'abnormal' imaging findings of the shoulder.The aim of the Finnish Imaging of Shoulder (FIMAGE) study is fourfold: to assess (1) the prevalence of shoulder symptoms and the most common anatomical variants and imaging abnormalities of the shoulder; (2) the concordance between shoulder symptoms, function and imaging abnormalities; (3) the most important determinants of symptoms, function and imaging abnormalities; and (4) the course of shoulder complaints over 5 years. METHODS: The FIMAGE target population of 600 participants, aged 40-75 years, will be randomly selected from a nationally representative general population sample of 9922 individuals originally recruited for the Finnish Health 2000 Survey. On giving informed consent, the participants will be invited to a clinical visit that includes assessment of general health, shoulder symptoms, bilateral shoulder examination and imaging of both shoulders with plain radiography and MRI. ETHICS AND DISSEMINATION: The study has been approved by the Institutional Review Board of the Helsinki and Uusimaa Hospital District. The findings will be published according to the Strengthening the Reporting of Observational Studies in Epidemiology criteria. TRIAL REGISTRATION NUMBER: NCT05641415.

[Subacromial shoulder impingement]. / Subakromiales Schulterimpingement.

Impingement, especially subacromial impingement, is one of the most frequent causes of shoulder pain. It results in soft tissue pathologies due to constriction of the subacromial space. It can lead to tendon pathologies and bursitis. In addition to the clinical examination, imaging methods such as magnetic resonance imaging (MRI), MRI arthrography, ultrasound and X­ray examinations are helpful in making a diagnosis or evaluating the cause of pain. Conservative treatment approaches, such as rest, medication, physiotherapy, manual therapy and infiltrations should primarily be used. If the symptoms do not improve after 3-6 months of conservative treatment, surgical treatment should be considered.

The impact of shoulder pathologies on job discontinuation and return to work: a pilot ultrasonographic investigation.

BACKGROUND: Ultrasound imaging has emerged as one of the most useful tools for evaluating shoulder disorders. To date, the association between shoulder ultrasonography and a patient's work status has rarely been explored by antecedent studies. AIM: This study aimed to investigate the association between sonographically diagnosed shoulder pathologies and job discontinuation and return to work. DESIGN: A cross-sectional study. SETTING: Outpatient clinic in the university hospital. POPULATION: Fifty-nine patients who were older than 20 years of age and had worked in a full-time job within the past three years. METHODS: All participants underwent clinical evaluation using the visual analog scale (for pain), Shoulder Pain and Disability Index, Pittsburgh Sleep Quality Index, and shoulder ultrasound examination. The work-related ergonomic risks, including dealing with heavy objects, repeated use and requiring forceful motion of the affected upper extremity, were assessed. The ultrasound-identified shoulder pathologies associated with job discontinuation, that is, sick leave due to painful shoulder for more than two consecutive months, were considered as the primary outcome. In the job discontinuation subgroup, we further investigated the association between return to work and the clinical/sonographic findings. RESULTS: Univariate analysis revealed a positive association between job discontinuation and shoulder surgery or work types requiring forceful upper-limb movements. Multivariate analysis demonstrated that job discontinuation was positively associated with supraspinatus tendon full-thickness tears (risk ratio, 8.80; 95% CI, 1.77-10.56; P=0.018). Of the patients who received shoulder surgery, 46.6% had recurrent rotator cuff tears. Return to work was likely to be related to pain scores during overhead activities and shoulder function impairment but not to sonographic findings. CONCLUSIONS: Job discontinuation is associated with shoulder surgery, work that necessitates forceful upper-extremity movements and supraspinatus tendon full-thickness tears detected by ultrasound. CLINICAL REHABILITATION IMPACT: Sonographic findings should not be used as the only standard for evaluating the patient's work capability.

Suprascapular nerve entrapment caused by a large hematoma of the scapula: a case report.

BACKGROUND: Suprascapular nerve entrapment is a rare disorder that is frequently misdiagnosed as another disease. The suprascapular nerve is commonly entrapped at the following two sites: the suprascapular and spinoglenoid notches. Nerve entrapment at the spinoglenoid notch causes infraspinatus muscle weakness and atrophy. Patients present with posterior shoulder pain and weakness. Magnetic resonance imaging is used to confirm the diagnosis of a spinoglenoid cyst and nerve compression. Open or arthroscopic aspiration or decompression is indicated for patients with cysts in whom conservative treatment has failed and those with cysts associated with suprascapular nerve compression. CASE PRESENTATION: Herein, we describe the case of a 49-year-old man with suprascapular nerve entrapment caused by a large cyst, namely, a hematoma, in the superior scapular and spinoglenoid notches. Open surgical decompression of the suprascapular nerve was performed owing to an intact rotator cuff and glenoid labrum. CONCLUSION: Posterior shoulder pain promptly resolved without complications.

Effects of adjuvant application of corticosteroid and ozone after ultrasound-guided puncture and lavage for the treatment of rotator cuff calcific tendinitis: study protocol for a non-inferiority randomized controlled trial.

BACKGROUND: Steroid injection after percutaneous irrigation of calcific deposits is a common method for the treatment of rotator cuff calcific tendinitis (RCCT). However, steroids may prevent calcification resorption and cause potentially irreversible damage to tendons. Recent studies have confirmed the positive effects of ozone injection in shoulder tendinopathies, but no RCCTs have been reported. Thus, our study aims to evaluate the non-inferiority of ozone versus steroid injection. METHODS: This is a prospective, randomized, parallel control and non-inferiority trial. A total of 100 patients with unilateral symptomatic RCCT will be enrolled and randomized in a 1:1 ratio to two groups: ultrasound-guided injection with ozone or corticosteroid. The primary outcome is the numeric rating scale for pain (NRS) at 1 week and 3 months following the procedure. Secondary outcomes include a multi-dimensional evaluation of shoulder disability and quality of life improvement, the degree of calcification absorption after treatment, and the number of multiple treatments. DISCUSSION: The results of this study will provide short-term and long-term evidence for the effectiveness of ozone treatment in RCCT in relieving pain or improving shoulder function. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR2200063469. Registered on 7 September 2022.

Imaging for patients presenting with a painful shoulder.

Shoulder pain is a common cause of musculoskeletal presentation in primary care, where both traumatic and atraumatic pathologies can also lead to emergency department attendances. This article discusses common acute and chronic presentations of a painful shoulder, looking at the typical history of patients presenting with a painful shoulder, examination findings and the most appropriate imaging modalities to consider. Strengths and weaknesses of each imaging modality are discussed along with their role in aiding diagnosis, as well as management of the various pathologies encountered in primary and secondary care.

ACR Appropriateness Criteria® Chronic Shoulder Pain: 2022 Update.

Chronic shoulder pain is an extremely common presenting complaint. Potential pain generators include the rotator cuff tendons, biceps tendon, labrum, glenohumeral articular cartilage, acromioclavicular joint, bones, suprascapular and axillary nerves, and the joint capsule/synovium. Radiographs are typically the initial imaging study obtained in patients with chronic shoulder pain. Further imaging may often be required, with modality chosen based on patient symptoms and physical examination findings, which may lead the clinician to suspect a specific pain generator. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Evaluation of a deep learning-based reconstruction method for denoising and image enhancement of shoulder MRI in patients with shoulder pain.

OBJECTIVES: To evaluate the diagnostic performance of an automated reconstruction algorithm combining MR imaging acquired using compressed SENSE (CS) with deep learning (DL) in order to reconstruct denoised high-quality images from undersampled MR images in patients with shoulder pain. METHODS: Prospectively, thirty-eight patients (14 women, mean age 40.0 ± 15.2 years) with shoulder pain underwent morphological MRI using a pseudo-random, density-weighted k-space scheme with an acceleration factor of 2.5 using CS only. An automated DL-based algorithm (CS DL) was used to create reconstructions of the same k-space data as used for CS reconstructions. Images were analyzed by two radiologists and assessed for pathologies, image quality, and visibility of anatomical landmarks using a 4-point Likert scale. RESULTS: Overall agreement for the detection of pathologies between the CS DL reconstructions and CS images was substantial to almost perfect (κ 0.95 (95% confidence interval 0.82-1.00)). Image quality and the visibility of the rotator cuff, articular cartilage, and axillary recess were overall rated significantly higher for CS DL images compared to CS (p < 0.03). Contrast-to-noise ratios were significantly higher for cartilage/fluid (CS DL 198 ± 24.3, CS 130 ± 32.2, p = 0.02) and ligament/fluid (CS DL 184 ± 17.3, CS 141 ± 23.5, p = 0.03) and SNR values were significantly higher for ligaments and muscle of the CS DL reconstructions (p < 0.04). CONCLUSION: Evaluation of shoulder pathologies was feasible using a DL-based algorithm for MRI reconstruction and denoising. In clinical routine, CS DL may be beneficial in particular for reducing image noise and may be useful for the detection and better discrimination of discrete pathologies. Assessment of shoulder pathologies was feasible with improved image quality as well as higher SNR using a compressed sensing deep learning-based framework for image reconstructions and denoising. KEY POINTS: • Automated deep learning-based reconstructions showed a significant increase in signal-to-noise ratio and contrast-to-noise ratio (p < 0.04) with only a slight increase of reconstruction time of 40 s compared to CS. • All pathologies were accurately detected with no loss of diagnostic information or prolongation of the scan time. • Significant improvements of the image quality as well as the visibility of the rotator cuff, articular cartilage, and axillary recess were detected.

Histological, radiological and clinical analysis of the supraspinatus tendon and muscle in rotator cuff tears.

BACKGROUND: Macroscopic alterations of the affected rotator cuff (RC) are undoubtedly linked to microscopic changes, but they may underestimate the actual degree of the disease. Moreover, it remains unclear whether preoperative structural RC changes may alter clinical outcomes. METHODS: Supraspinatus tendon and muscle samples were collected from 47 patients undergoing RC surgery. Tendons were evaluated histologically according to the Bonar score; fatty infiltration and muscle atrophy were quantified using a software for biomedical image analysis (ImageJ) in percentage of area affected in the observed muscle section. Preoperative shoulder ROM and pain were evaluated. Radiological muscle atrophy was evaluated with the Tangent Sign and Occupation Ratio; fatty infiltration was assessed according to the Goutallier classification. Correlations between histological, radiological and clinical outcomes were assessed. Statistics were performed using the Spearman correlation coefficient. Intraobserver and interobserver agreement was calculated. RESULTS: Histopathologic fatty infiltration (r = 0.007, p = 0.962), muscle atrophy (r = 0.003, p = 0.984) and the total Bonar score (r = 0.157, p = 0.292) were not correlated to preoperative shoulder pain. Muscle atrophy showed a significant but weak negative correlation with the preoperative movement of abduction (r = -0.344, p = 0.018). A significant but weak positive correlation was found between muscle atrophy and the total Bonar score (r = 0.352, p = 0.015). No correlation between histological and radiological evaluation was found for both fatty infiltration (r = 0.099, p = 0.510) and muscle atrophy (Tangent Sign: r = -0.223, p = 0.131; Occupation Ratio: r = -0.148, p = 0.319). Our histological evaluation showed a modal value of 3 (out of 3) for fatty infiltration and an equal modal value of 2 and 3 (out of 3) for muscle atrophy. In contrast, the modal value of the Goutallier score was 1 (out of 4) and 28 patients out of 47 showed a negative Tangent sign. At histology, intraobserver agreement ranged from 0.59 to 0.81 and interobserver agreement from 0.57 to 0.64. On the MRI intraobserver agreement ranged from 0.57 to 0.71 and interobserver agreement ranged from 0.53 to 0.65. CONCLUSIONS: Microscopic muscle atrophy appeared to negatively correlate with the movement of abduction leading to functional impairment. Shoulder pain did not show any relationship with microscopic changes. Radiological evaluation of the supraspinatus muscle alterations seemed to underestimate the degree of the same abnormalities evaluated at histology.