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Background: Several tests have been suggested for screening and diagnosis of cervical spine and shoulder girdle conditions underlying shoulder pain with variable degrees of clinical accuracy. The present study aimed to test the reliability, clinical benefit and screening value of the Swimmer Arm-to-Shoulder (SAS) test; a new clinical test developed to differentiate shoulder impingement from cervical radiculopathy in patients with shoulder pain of ≤ 12 weeks., Methods: The study included 718 patients aged 40-65 years, with unilateral and localized shoulder girdle pain lasting for ≤ 12 weeks. Diagnosis based on clinical, electromyography and radiological findings was considered as the reference gold standard for test assessment., Results: Clinical diagnosis identified shoulder pathology in 288 patients (40.1%) and cervical spine pathology in 430 patients (59.9%). SAS test was positive in 274 patients (38.2%). The SAS test proved to be effective in distinguishing shoulder from cervical spine pathology with a sensitivity of 89.2% (95% CI: 85.0-92.6%), specificity of 96.1% (95% CI: 93.8-97.7%), PPV of 93.8% (95% CI: 90.5-96.0%), NPV of 93.0% (95% CI: 90.5-94.9%), LR + of 22.6% (95% CI: 14.1-36.0%), LR- of 0.11 (95% CI: 0.08-0.16) and accuracy of 93.3% (95% CI: 91.2-95.0%)., Conclusions: SAS test is an easy to perform, patient dependent and reliable as a screening test and diagnosis confirmatory test., Competing Interests: Declarations. Ethics approval and consent to participate: Protocol of the present study was approved by the ethical committee of Al-Azhar Faculty of Medicine and all participants provided informed consent in accordance with the Helsinki Declaration on clinical research involving human subjects. Consent for publication: NA. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Objective: Aims were to (i) report prevalence and (ii) evaluate reliability of the radiographic findings in examinations of patients suspected of subacromial impingement syndrome (SIS), performed before a patient's first consultation at orthopaedic department., Materials and Methods: This cross-sectional study examined radiographs from 850 patients, age 18 to 63 years, referred to orthopaedic clinic on suspicion of SIS. Prevalence (%) of radiographic findings were registered. Inter- and intrarater reliability was analysed using expected and observed agreement (%), kappa coefficients, Bland-Altman plots, or intraclass coefficients., Results: A total of 850 patients with a mean age of 48.2 years (SD = 8.8) were included. Prevalence of the radiographic findings was as follows: calcification 24.4%, Bigliani type III (hooked) acromion 15.8%, lateral/medial acromial spurs 11.1%/6.6%, acromioclavicular osteoarthritis 12.0%, and Bankart/Hill-Sachs lesions 7.1%. Inter- and intrarater Kappa values for most radiographic findings ranged between 0.40 and 0.89; highest values for the presence of calcification (0.85 and 0.89) and acromion type (0.63 and 0.66). The inter- and intrarater intraclass coefficients ranged between 0.41 and 0.83; highest values for acromial tilt (0.79 and 0.83) and calcification area (0.69 and 0.81)., Conclusion: Calcification, Bigliani type III (hooked) acromion, and acromioclavicular osteoarthritis were prevalent findings among patients seen in orthopaedic departments on suspicion of SIS. Spurs and Bankart/Hill-Sachs lesions were less common. Optimal reliabilities were found for the presence of calcification, calcification area, and acromial tilt. Calcification qualities, acromion type, lateral spur, and acromioclavicular osteoarthritis showed suboptimal reliabilities. Newer architectural measures (acromion index and lateral acromial angle) performed well with respect to reliability., (© 2024. The Author(s).)

Background: Most manual wheelchair users with pediatric-onset spinal cord injury (SCI) will experience shoulder pain or pathology at some point in their life. However, guidelines for preservation of the upper limb in children with SCI are limited., Research Question: What are the relationships between manual wheelchair handrim kinetics and quantitative ultrasound parameters related to subacromial impingement in individuals with pediatric-onset SCI?, Methods: Subacromial impingement risk factors including supraspinatus tendon thickness (SST), acromiohumeral distance (AHD), and occupation ratio (OR; SST/AHD) were measured with ultrasound in 11 manual wheelchair users with pediatric-onset SCI. Handrim kinetics were acquired during the stroke cycle, including peak resultant force (F R ), peak rate of rise of resultant force (ROR) and fractional effective force (FEF). Variability of handrim kinetics was computed using the coefficient of variation and linear regression was performed to assess correlations between handrim metrics and quantitative ultrasound parameters., Results: Peak resultant force significantly increased 1.4 % and variability of FEF significantly decreased 8.0 % for every 0.1 cm increase in AHD. FEF decreased 3.5 % for every 0.1 cm increase in SST. Variability of peak resultant force significantly increased 3.6 % and variability of peak ROR of resultant force significantly increased 7.3 % for every 0.1 cm increase in SST. FEF variability significantly decreased 11.6 % for every 0.1 cm increase in SST. Peak ROR significantly decreased 1.54 % with every 10 % increase in OR. FEF variability significantly decreased 1.5 % with every 10 % increase in OR., Significance: This is the first study to investigate relationships among handrim kinetics and shoulder structure in manual wheelchair users with pediatric-onset SCI. Associations were identified between subacromial impingement risk factors and magnitude and variability of wheelchair handrim kinetics. These results indicate the critical need to further explore the relationships among wheelchair handrim kinetics, shoulder joint dynamics, and shoulder pathology in manual wheelchair users with pediatric-onset SCI., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests. Caleb M.A. Cordes, Joshua M. Leonardis, Alyssa J. Schnorenberg, Lawrence C. Vogel, Amee L. Seitz, and Brooke A. Slavens report financial support was provided by the National Institutes of Health. Lawrence Vogel reports a relationship with Pediatric Rehabilitation Consulting, LLC that includes: paid expert testimony. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Rugby is a sport involving a great number of shoulder collisions. Traumatic stress of the shoulder can weaken the static stabilizers and promote major injuries as dislocation or full-thickness tears of the rotator cuff. The goal of this study is to evaluate the clinical and ultrasonographic dominant shoulder factures in a group of amateur rugby players, with no history of shoulder injuries, and to compare them with those of a control group., Methods: 52 male subjects join in the study: 26 amateur rugby players and 26 subjects, which did not practice rugby or competitive sport. Clinical history was obtained from all subjects, followed by dominant shoulder physical and ultrasonographic exams., Results: Rugby players showed a higher prevalence of positive clinical test, suggesting subacromial impingement than control group (p = 0.01). Among rugby group, five players (19,2%) showed positive test for radiculopathy (p = 0,02), and ten players (73,1%) reported shoulder pain needing pain-reliever drugs at list one time in the last six months (p = 0.001). In rugby group, ultrasound exams showed 23,1% degenerative changes and 30,8% tendon calcifications in supraspinatus tendons (p < 0.05)., Conclusions: Uninjured dominant shoulder of rugby players shows higher prevalence of clinical and ultrasound changes compare to control. Some rugby players without history of cervical symptoms show positive clinical test of cervical radiculopathy. Clinical and ultrasonographic monitoring of the shoulder can play a role in prevention and knowledge of silent shoulder damage in these athletes., (© 2024. The Author(s).)

Background: Subacromial impingement syndrome is one of the most common causes of painful shoulder in the middle-aged and elderly population. Coracoacromial ligament (CAL) degeneration is a well-known indicator for subacromial impingement., Purpose: To examine the relationship between CAL thickness on preoperative magnetic resonance imaging (MRI), arthroscopic CAL degeneration and types of rotator cuff tears., Material and Methods: Video records of patients who underwent arthroscopic shoulder surgery between 2015 and 2021 were retrospectively scanned through the hospital information record system. In total, 560 patients were included in this study. Video records of the surgery were used to evaluate the grade of coracoacromial ligament degeneration and the type of cuff tear. Preoperative MRI was used to measure CAL thickness, acromiohumeral distance, critical shoulder angle, acromial index, and acromion angulation., Results: Significant differences were observed between grades of CAL degeneration in terms of CAL thickness ( P  < 0.001). As CAL degeneration increases, the mean of CAL thickness decreases. According to the results of post-hoc analysis, the mean CAL thickness of normal patients was significantly higher than those of patients with full-thickness tears ( P  = 0.024) and massive tears ( P  <0.001). Patients with articular-side, bursal-side, and full-thickness tears had significantly higher CAL thickness averages than patients with massive tears., Conclusion: This study showed that the CAL thickness decreases on MRI as arthroscopic CAL degeneration increases. High-grade CAL degeneration and therefore subacromial impingement syndrome can be predicted by looking at the CAL thickness in MRI, which is a non-invasive method., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: In subacromial pain syndrome (SPS), it is unknown whether posterior shoulder stretching exercises (PSSE) with rapid eccentric contraction, a muscle energy technique, improve clinical and ultrasonographic outcomes more than no stretching or static PSSE., Hypothesis: PSSE with rapid eccentric contraction is superior to no stretching and static PSSE in improving clinical and ultrasonographic outcomes in SPS., Study Design: Randomized controlled trial., Level of Evidence: Level 1., Methods: Seventy patients with SPS and glenohumeral internal rotation deficit were randomized into the modified cross-body stretching with rapid eccentric contraction group (EMCBS; n = 24), static MCBS group (SMCBS; n = 23), or control group (CG; n = 23). In addition to 4-week physical therapy, EMCBS received PSSE with rapid eccentric contraction, SMCBS static PSSE, and CG no PSSE. The primary outcome was internal rotation range of motion (ROM). Secondary outcomes were posterior shoulder tightness, external rotation ROM (ERROM), pain, modified Constant-Murley score, short form of the disabilities of the arm, shoulder, and hand questionnaire (QuickDASH), rotator cuff strength, acromiohumeral distance (AHD), supraspinatus tendon thickness, and supraspinatus tendon occupation ratio (STOR)., Results: Shoulder mobility, pain, function and disability, strength, AHD, and STOR improved in all groups ( P < 0.05)., Conclusion: In patients with SPS, PSSE with rapid eccentric contraction and static PSSE were superior to no stretching in improving clinical and ultrasonographic outcomes. Stretching with rapid eccentric contraction was not superior to static stretching, but improved ERROM compared with no stretching., Clinical Relevance: In SPS, both PSSE with rapid eccentric contraction and static PSSE included in physical therapy program are beneficial to improve posterior shoulder mobility and other clinical and ultrasonographic outcomes. In the case of ERROM deficiency, rapid eccentric contraction might be preferred., Competing Interests: The authors report no potential conflicts of interest in the development and publication of this article.

Background: Subacromial spurs are considered the one of the pathology underlying shoulder impingement syndrome. Furthermore, few studies have focused on the morphology of the subacromial spurs in normal Chinese people. This study aimed to study the spur distribution and to illustrate the morphology of spurs, which may help guide the extent of acromioplasty., Methods: A total of 93 normal individuals were enrolled, and both shoulders of all enrolled individuals were analyzed. The subjects were divided and classified into three different groups by ages: group I = 18-40 years, group II = 41-60 years, and group III ≥ 61 years. The osteophyte distribution, osteophyte area, subacromial surface area and osteophyte area/subacromial surface area ratio were measured and illustrated using Mimics and 3-matic software. The shape of the acromion was classified according to the Bigliani and Morrison classification system. The acromial angle was also classified. Then, the relationship between osteophytes, acromial classification and acromial angle was analyzed., Results: Type II (curved shape) was the most common type of acromion, and the hooked shape was a rare form. A significant increase in the left subacromial surface area in males was observed in group III compared with group I (P < 0.001) and group II (P = 0.004). The total spur/subacromial area ratio was significantly higher in group II than I. An obvious increase in the right subacromial area was observed in group III compared with group I (P = 0.004). Furthermore, there was a significant increase in the right spur area (P = 0.021) and total spur/subacromial area ratio (P = 0.006) in females in group II compared with group I. Fewer spurs were observed on the left than on the right side (p = 0.0482). One spur was most common among type II acromions (29/36) (80.56%) on the left side and the right side (34/52, 65.38%)., Conclusions: Spurs osteophytes are mainly distributed with an irregular shape and mostly run through the medial and lateral sides of the subacromial surface in normal subjects. The characteristics of subacromial spurs are so diverse that a surgeon must conduct subacromial decompression completely based on the morphology of individual spurs., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Dong et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objective: To evaluate the diagnostic value of musculoskeletal ultrasound measurements of subacromial bursa (SAB) thickness, supraspinatus tendon (SUP) thickness, acromiohumeral distance (AHD), and SUP-to-AHD ratio (AHD%) in patients with shoulder impingement syndrome (SIS)., Methods: This was a prospective cross-sectional observational study. Thirty patients with SIS (60 shoulders) admitted between January 2019 and January 2020 were enrolled. The SUP thickness, SAB thickness, AHD, and AHD% (calculated as AHD% = [(SUP / AHD) × 100%]) were measured in 60 shoulders using musculoskeletal ultrasound., Results: The affected shoulder displayed thicker SUP and SAB (t = 7.838), narrower AHD (t = 2.324), and larger AHD% (t = 6.875) than the unaffected shoulder (P < .05). The SUP thickness showed a linear positive correlation with AHD (r = .503) and AHD% (r = .792) in the affected shoulder (P < .05). On receiver operating characteristic analysis, AHD*AHD% showed the best diagnostic performance in both measurements (area under the curve: 0.877)., Conclusion: This study revealed that SIS symptoms may be related to a larger AHD% with SUP thickening. As diagnostic criteria, the cut-off values of AHD% (65.6%) and AHD*AHD% (0.504) have good sensitivity and specificity and can help improve the differential diagnosis of patients with SIS., (© 2023 American Institute of Ultrasound in Medicine.)

Objective: To compare the effectiveness of intra-bursal injection of single-dose platelet-rich plasma (PRP) against corticosteroids under ultrasonography guidance in shoulder impingement syndrome (SIS)., Materials and Methods: This single-blind randomized controlled trial was conducted on 60 participants with a clinical diagnosis of SIS from a selected orthopedic clinic. Thirty participants in each arm were given a single dose of either PRP or triamcinolone acetonide into the subacromial sub-deltoid bursa (SASD) under ultrasonography guidance. The outcome variables assessed were the severity score of pain and the degree of shoulder abduction. Post-treatment follow-up was done in 1 week, 3 months, 6 months, and 1 year., Results: At 1 week, the triamcinolone arm showed a statistically significant reduction of pain (p = 0.039) when compared to PRP. In the long term, PRP showed statistically significant improvement in shoulder abduction, compared to the triamcinolone injection (p = 0.012)., Conclusion: PRP and triamcinolone in the SASD bursa could be considered as safe treatment options for SIS under ultrasonography guidance. While triamcinolone was effective in short-term pain reduction, PRP was effective in long-term improvement in shoulder abduction., (© 2023. The Author(s), under exclusive licence to International Skeletal Society (ISS).)

Background: The bone morphology of the greater tuberosity and lateral acromion plays a central role in subacromial impingement syndrome. The critical shoulder angle (CSA) and greater tuberosity angle (GTA) are two-dimensional measurement parameters that have been validated to evaluate it radiologically. These markers are, however, static and don't consider the dynamic effect of glenohumeral motion., Objectives: This study aimed to better understand the biomechanics in subacromial impingement with a dynamic simulation based on a validated 3D biomechanical model coupling joint kinematics and 3D reconstructed computed tomography., Study Design & Methods: Sixty-one patients were included in this study: a case group of 44 patients with degenerative rotator cuff tears involving only the supraspinatus, and a control group of 17 without a rotator cuff tear. Patients with previous surgeries, traumatic cuff tears, and cuff tear arthropathy were excluded. CSA, GTA, and impingement-free range of motion (IF-ROM) of the glenohumeral joint in scaption were calculated. Correlation tests were used to determine the relationship between ROM and CSA, GTA, and combined CSA and GTA values., Results: CSA and GTA were significantly higher in the rotator cuff tear group (p = 0.001 and < 0.001), while IF-ROM was significantly higher in the control group (p = 0.001). There was no overall correlation between CSA and GTA (R = 0.02, p = 0.8). Individual correlation between both angles with IF-ROM was negatively weak for CSA (R = -0.4, p < 0.001) and negatively moderate for GTA and IF-ROM (R = -0.5, p < 0.001). However, combining both angles resulted in a negatively high correlation with IF-ROM (R = -0.7, p < 0.001)., Conclusion: Subacromial space narrowing during scaption is highly correlated to the cumulative values of GTA and CSA. These findings suggest that the combined bony morphology of the lateral acromion and greater tuberosity plays an important role in subacromial impingement., Level of Evidence: III., (© 2023. The Author(s).)

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 X‑ray 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., (© 2023. The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

Objectives: Rotator cuff injury caused by subacromial impingement presents different morphologies. This study aims to investigate the correlation between various shoulder anatomical indexes on X-ray with subacromial impingement and morphology of rotator cuff tears to facilitate surgical management., Method: This retrospective study was carried out between January 2020 and May 2022. Patients who were diagnosed as sub-acromial impingement associated with rotator cuff tears (without tendon retraction) and received arthroscopic surgery were enrolled in this study. The radiographic indexes of acromial slope (AS), acromial tilt (AT), lateral acromial angle (LAA), acromial Index (AI), and sub-acromial distance (SAD) were measured on preoperative true AP view and outlet view. The location of rotator cuff tear (anterior, middle, posterior, medial, and lateral) and morphology of tear (horizontal, longitudinal, L-shaped, and irregular shaped) were evaluated by arthroscopy. Groups were set up due to different tear location and tear morphologies, by comparing the various radiographic indices between each group (one-way analysis of variance and t-test), the correlation between radiographic indices and tear characteristics was investigated., Results: We analyzed 92 shoulders from 92 patients with a mean age of 57.23 ± 8.45 years. The AS in anterior tear group (29.32 ± 6.91°) was significantly larger than that in middle tear group (18.41 ± 6.13°) (p = 0.000) and posterior tear group (24.01 ± 7.69°) (p = 0.041). The AS in posterior tear group (24.01 ± 7.69°) was significantly larger than that in middle tear group (18.41 ± 6.13°) (p = 0.029). The LAA in middle tear group (67.41 ± 6.54°) was significantly smaller than that in posterior group (72.74 ± 8.78°) (p = 0.046). The AS in longitudinal tear group (26.86 ± 8.41°) was significantly larger than that in horizontal tear group (22.05 ± 9.47°) (p = 0.035) and L-shaped group (21.56 ± 6.62°) (p = 0.032). The LAA in horizontal group (70.60 ± 6.50°) was significantly larger than that in L-shaped group (66.39 ± 7.31°) (p = 0.033). The AI in L-shaped tear group (0.832 ± 0.074) was significantly larger than that in horizontal tear group (0.780 ± 0.084) (p = 0.019) and irregular tear group (0.781 ± 0.068) (p = 0.047)., Conclusion: Acromion with a larger AS and a smaller LAA tend to cause anterior or posterior rotator cuff tears rather than middle tears in sub-acromial impingement. Meanwhile acromion with a larger AS tends to cause a longitudinal tear, a larger LAA tends to cause horizontal tears and a larger AI tends to cause L-shaped tears., (© 2022 The Authors. Orthopaedic Surgery published by Tianjin Hospital and John Wiley & Sons Australia, Ltd.)

Shoulder impingement is the most common diagnosis for shoulder pain. Shoulder impingement syndrome has been scrutinized as a misleading "umbrella" term, due to its vague and nonspecific context. It is better subcategorized into subacromial, internal, and subcoracoid impingement. The evaluation and treatment algorithm for each is grossly similar. A thorough history, focused physical examination, and standard radiographs are the first steps. Advanced imaging with MRI or ultrasound may be useful. The mainstay of treatment includes physical therapy, anti-inflammatory medications, and injections. Surgical treatment is reserved for refractory cases, and includes decompression, debridement, and/or repair of injured structures., Competing Interests: Disclosure E.H. Horowitz has nothing to disclose. W.R. Aibinder is a consultant for Exactech Inc, serves on the editorial board for EJOST., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Objectives: To explore the subacromial motion metrics in patients with and without subacromial impingement syndrome (SIS) and to investigate whether the abnormality was associated with rotator cuff pathologies., Design: This cross-sectional observational study used dynamic quantitative ultrasonography imaging for shoulder joint assessment., Setting: Outpatient rehabilitation clinic., Participants: Individuals with SIS on at least 1 shoulder (n=32) and asymptomatic controls (n=32) (N=64)., Interventions: Not applicable., Main Outcome Measures: Frame-by-frame, the humeral greater tuberosity against the lateral edge of the acromion was traced to obtain the minimal vertical acromiohumeral distance (AHD). The rotation angle and radius of the humerus were computed using the least-squares curve fitting method., Results: Approximately two-thirds of the shoulders with SIS did not have any sonographically identifiable rotator cuff pathologies. There was a consistent trend of nonsignificantly increased humeral rotation angles in painful shoulders. The generalized estimating equation demonstrated that the decreased minimal vertical AHD was associated with painful subacromial impingement (β coefficient: -0.123cm, 95% confidence interval [CI], -0.199 to -0.047). The area under the curve for the minimal vertical AHD to discriminate painful or impinged shoulders ranged from 0.624-0.676. The increased rotation angle (β coefficient: 10.516°; 95% CI, 3.103-17.929) and decreased rotation radius (β coefficient: -2.903cm; 95% CI, -5.693 to -0.111) were shown to be significantly related to the presence of supraspinatus tendinopathy., Conclusions: Shoulders with SIS were characterized by a decreased minimal vertical AHD during dynamic examination. Abnormal subacromial metrics can develop in patients with mild (or no) rotator cuff pathologies. More prospective cohort studies are warranted to investigate the changes in subacromial motion metrics in populations at risk for painful or impinged shoulders., (Copyright © 2022 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.)

Background: : The purpose of this study is to investigate whether the etiological factors accepted as causes of idiopathic subscapularis tears are true or not when the comparison is made with the opposite side healthy shoulder of the patients who underwent arthroscopic repair for an isolated subscapularis tear., Methods: Sixteen patients who underwent shoulder arthroscopy between February 2016 and January 2018 and were diagnosed with isolated subscapularis tear were evaluated. The coracohumeral distance (CHDax), coracoid overlap (CO), and tuberculum minus cysts (TMC) were evaluated on the axial images of the MRI studies while the acromiohumeral distance (AHDsag), CHDsag, and subscapularis tendon slip number (STSN) on the sagittal oblique images and the AHDcor and SLAP lesion on the coronal oblique images. Degeneration of the coracoacromial ligament was evaluated during arthroscopy., Results: The mean CHDsag (11.26-10.08), CHDax (10.63-9.98), CO (14.2-15.43), AHDsag (8-7.66), and AHDcor (7.65-7.68) measurements (operated side-healthy side, respectively) were statistically similar (p > 0.05). No statistically significant difference was found between TMC and STSN in healthy and operated shoulders (p > 0.05). There was mild coracoacromial ligament fraying in 4 (25%) and obvious coracoacromial ligament fraying in 8 (50%) which indicated subacromial impingement in 75% of the patients., Discussion: The parameters of the coracoid process did not reveal any significant difference between the operated (for an isolated subscapularis tear) and opposite-side healthy shoulders of the patients. However, coracoacromial ligament degeneration was present in 75% of the patients.

Background: Platelet-derived lyophilized growth factors (L-GFs) use a standardized number of allogenic pathogen-free platelets instead of autologous platelets used in PRP as a source of growth factors. This study aimed to evaluate the efficacy of L-GF injection versus placebo in subacromial impingement (SIS) treatment., Methods: The current randomized double-blind placebo-controlled study included sixty patients (40 females and 20 males, aged between 24 and 75 years) diagnosed with SIS (both clinically and sonographically). Patients were randomly assigned to two equal groups. Under ultrasound guidance, group 1 received subacromial saline injection, and group 2 received L-GF injection. Clinical examination, pain visual analogue scale (VAS), shoulder pain and disability index (SPADI) and shoulder ultrasound were performed before and at the 8th week after injection., Results: Follow-up assessment showed statistically significant improvement in the L-GF group regarding active flexion, active and passive internal rotation and extension, SPADI-disability scale, VAS and thickness of the supraspinatus tendon by US. Regression analysis showed that group 1 was approximately 30 times more likely than the L-GF group to experience painful arc at follow-up. Both groups showed statistically significant improvement in SPADI-pain scale and SPADI-total, flexion and abduction (still the mean value of abduction was significantly higher in the L-GF group)., Conclusions: L-GF injection resulted in clinically significant reductions in pain and functional disability outcomes in patients with SIS. An objective significant reduction in the thickness of the supraspinatus tendon, measured by ultrasound, in the L-GF group hopefully encourages proper healing and functioning in SIS., Trial Registration: The identification number is NCT04330027, date of first registration (01/04/2020). Unique on 21/11/2019, Protocol ID: 0106178., (© 2023. The Author(s).)

Background: Differentiation between subacromial impingement versus subcoracoid impingement are important for the treatment target. We evaluated the correlations between coracohumeral ligament (CHL) thickness and distance (CHD) and characterized the CHL and subscapularis (SSC) in subcoracoid impingement subjects., Methods: An observational, cross-sectional study was carried out. Twenty subcoracoid impingement subjects and age/gender matched controls were assessed in 4 different shoulder positions by ultrasonography., Results: Moderate correlations between CHL thickness with CHD (r = 0.455 in neutral rotation, p = 0.044; r = 0.483 in interior rotation, p = 0.031) were found in subacromial subjects. Subcoracoid impingement subjects had greater CHL thickness (difference = 0.3 mm, effect size = 0.85, p = 0.006), SSC tendon thickness (difference = 0.7 mm, effect size = 0.92, p = 0.01) and SSC/CHD occupation ratio (difference = 8%, effect size = 0.95, p = 0.005) compared with the control., Conclusions: Coracohumeral distance is related to ligament thickness, especially in subacromial impingement subjects. Increased coracohumeral ligament and subscapularis thickness as well as decreased subscapularis/coracohumeral distance occupation ratio are characterized in subcoracoid impingement subjects. These quantitative measurements can be useful in identifying patients at risk of subcoracoid impingement from subacromial impingement., (© 2023. The Author(s).)

Understanding the anatomy, injury patterns, and surgical procedures is essential for image interpretation. While direct evaluation of the rotator cuff cannot be made, radiographs of the shoulder provide the initial evaluation of the osseous abnormalities associated with rotator cuff impingement. MR imaging is considered the study of choice for the evaluation of the shoulder because of the comprehensive assessment of both bone and soft-tissue abnormalities. MR can accurately evaluate the size and shape of tendon tears, tendon tear retraction, and tendon and muscle quality. Computed tomography is an excellent modality for the evaluation of osseous detail and detection of gas and calcium deposition; however, conventional CT is much less sensitive for bone marrow edema detection and soft tissue detail of the rotator cuff. Ultrasound can assess the rotator cuff with results similar to MRI, but cannot evaluate osseous structures., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Introduction: Shoulder pain is one of the most common complaints in orthopaedics. This study focusses on the relationship between shoulder function in subacromial impingement syndrome and imaging criteria in magnetic resonance imaging (MRI)., Materials and Methods: This prospective clinical trial included 69 patients treated for subacromial impingement syndrome. Shoulder function (Constant Score, range of abduction, abduction force) and pain were correlated with the following MRI parameters: tendinosis of the rotator cuff, "halo-sign" around the biceps tendon, subacromial distance, critical shoulder angle, size of subacromial osteophytic spurs and maximum width of subacromial and subdeltoid bursa. Statistical analyses included Pearson's and Spearman's coefficients of correlation, multiple regression analysis and Student's t-test., Results: The Constant Score was correlated positively with the critical shoulder angle (r = 0.313; p = 0.009) and inversely with a "halo-sign" around the biceps tendon (rho =  -0.384; p = 0.001). There was no significant correlation between spur size and shoulder function, but the size of the subacromial and subdeltoid bursae was positively correlated with the subacromial spur's size (subacromial bursa: coronal plane: r = 0.327; p = 0.006; sagittal view: r = 0.305; p = 0.011; subdeltoid bursa coronal view: r = 0.333 p = 0.005). The width of the subdeltoid bursa in coronal plane was positively correlated with shoulder pain (r = 0.248; p = 0.004) and negatively with the range of abduction (r =  -0.270; p = 0.025), as well as the mean (r =  -0.332; p = 0.005) and maximum (r =  -0.334; p = 0.005) abduction force., Conclusions: Shoulder function and pain in subacromial impingement are best predicted by the width of the subdeltoid bursa measured in the coronal MRI plane as an indicator of bursitis as well as the presence of a "halo-sign" around the biceps tendon indicating glenohumeral joint effusion. Presence of a subacromial spur could lead to subacromial and subdeltoid bursitis, which impairs shoulder function. Shoulder function seems not to be compromised by the presence of a subacromial spur in absence of bursitis. This study was registered at the German Clinical Trials Register on 08 February 2013 (ID: DRKS00011548)., (© 2021. The Author(s).)

Objective: The aim of the study was to compare the efficacy and safety of ultrasound-guided versus anatomic landmark-guided corticosteroid injection for the treatment of subacromial impingement syndrome., Design: PubMed, Embase, Web of Science, Cochrane Central Register of Controlled Trials, Scopus, ClinicalTrials.gov , CBM, CNKI, and Wanfang databases were searched from inception to August 15, 2021, for randomized controlled trials comparing ultrasound-guided versus anatomic landmark-guided injections of corticosteroids for the treatment of subacromial impingement syndrome., Results: Twelve randomized controlled trials with 891 patients were included in this study; 454 patients received ultrasound-guided injections and 437 received anatomic landmark-guided injections. Pooled results showed that ultrasound-guided injection was more beneficial for pain relief (10 trials; mean difference = -0.58; 95% confidence interval = -1.05 to -0.10; P = 0.017) and functional improvement (11 trials; standard mean difference = -0.84; 95% confidence interval = -1.41 to -0.27; P = 0.004). There was no significant difference in shoulder range of motion. In the subgroup analysis, there was a significant difference in pain relief and functional improvement at 6-8 wks and with methylprednisolone., Conclusions: Ultrasound-guided injection of corticosteroids is potentially superior to anatomic landmark-guided injection in improving the clinical symptoms of subacromial impingement syndrome; however, these findings should be interpreted with some caution as the quality of evidence was rated as moderate to very low., Competing Interests: Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Range of motion (ROM) and prevention of notching remain a challenge for reverse shoulder arthroplasty (RSA). Both may be affected by the morphology of the scapula. The purpose of this study was to define anteroinferior (a) and posteroinferior (p) relevant scapular neck offset (RSNO) and to examine the hypothesis that pRSNO is significantly smaller than aRSNO, and influences rigid body motion (RBM). Adapting glenosphere implantation strategies may therefore be of value., Material and Methods: In this computer model study, we used deidentified computed tomographic scans of 22 patients (11 male and 11 female; mean age: 72.9 years) with massive cuff tears without joint space narrowing. Eight RSA glenoid configurations were tested with a constant neck-shaft angle (145°). Two baseplate types (25 mm; 25 + 3 mm lateralized) and 4 glenospheres (GS) (36 mm; 36 +2 mm of eccentricity; 39 mm; 39 + 3 mm) were used. RSNO was defined as the standardized measurement of the horizontal distance from the inferior extent of the GS to the bony margin of the scapula after baseplate positioning (flush to inferior glenoid extent; neutral position: 0° inclination and 0° version-both software computed)., Results: There was a highly significant difference between pRSNO and aRSNO for both genders (P < .001). pRSNO was always smaller than aRSNO. pRSNO was strongly correlated with external rotation (ERO: 0.84) and extension (EXT: 0.74) and moderately correlated with global ROM (GROM: 0.68). There was a moderately strong correlation between aRSNO and internal rotation (IRO: 0.69). pRSNO was strongly correlated with aRSNO, EXT, ERO, IRO, adduction (ADD) and GROM (0.82, 0.72, 0,8, 0.71, 0.82, 0.76) in female patients and with EXT and ERO (0.82, 0.89) in male patients. The median pRSNO allowing for at least 45° ERO and 40° EXT was 14.2 mm for men and 13.8 mm for women. For all patients and models, pRSNO ≥14 mm increased EXT, ERO, and GROM significantly compared with pRSNO <14 mm (P < .001). The combination of lateralization and inferior overhang (eccentricity) led to the most significant increase of pRSNO for each GS size (P < .001)., Conclusion: This is one of the first RSA modeling studies evaluating nonarthritic glenoids of both genders. The lateral scapular extent to glenoid relationship is asymmetric. pRSNO is always smaller than aRSNO for both genders and was a critical variable for EXT and ERO, demonstrating additional strong correlation with aRSNO, IRO, ADD, and GROM in female patients. pRSNO ≥14 mm was a safe value to prevent friction-type impingement. Combining increased glenosphere size, lateralization, and inferior overhang gives the best results in this computer-simulated setting., (Copyright © 2022 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Subacromial impingement syndrome (SAIS) is a common cause of shoulder pain. The effects of physiotherapy modalities including low-level laser (LLL) and high power laser (HPL) on the SAIS have mostly been evaluated by the subjective outcome variables accompanied with the controversial findings and none of them has compared a combination of these two modalities, yet., Objectives: The present study was conducted to evaluate the effects of low-level laser (LLL) and high power laser (HPL) combined with kinesiology taping (KT), on the pain, function, and musculoskeletal ultrasound (MSKUS) parameters in the SAIS., Methods: Thirty patients with SAIS were randomly divided into the LLL-KT, HPL-KT, and sham-KT groups, respectively. Patients received seven treatment sessions. Visual analogue scale (VAS), shoulder pain and disability index (SPADI), MSKUS parameters were measured before and 48 hours after the treatment cessation., Results: Pain intensity significantly reduced in the LLL-KT (-2.43 (0.97)), HPL-KT (-3.43 (1.99)), and sham-KT (-2.43 (1.62)) ( P < .01). All the SPADI subscales are significantly reduced in all the groups ( P < .05), except for the pain in the sham-KT ( P = .06). Significant improvements were only observed in the diameters of biceps ( P < .05), supraspinatus tendon thickness in short and long axes ( P < .05), occupation ratio ( P = .004), and echogenicity ( P = .03) in the HPL-KT. Although the acromiohumoral distance (AHD) significantly increased in all the groups including the sham-KT ( P < .01), supraspinatus tendon thickness significantly decreased ( P < .05), and echogenicity increased ( P = .003) just in the HPL-KT., Conclusions: Kinesiology taping method alone is an effective intervention. Nevertheless, adding the analgesic and anti-inflammatory effects of both LLL and HPL to KT seems to result in better improvement of the pain, function, and MSKUS parameters in the SAIS. Findings of this study suggested that the HPL is more beneficial than the LLL or KT alone for management of the patients with SAIS.

Objectives: To determine the performance of machine learning (ML)-based ultrasomic analysis of subacromial impingement syndrome (SIS) stage evaluation., Methods: In this retrospective study, 324 patients with SIS were included. The SIS stage was evaluated with a Neer test. Regions of the musculi supraspinatus were manually segmented by an experienced radiologist. Then, 5936 ultrasomic features were extracted from the Ultrasomics Platform software. The Wilcoxon test was used to identify differentially expressed radiomic features. Then, these differentially expressed features were submitted to the least absolute shrinkage and selection operator (LASSO) for model construction. The area under the curve (AUC) of the receiver operating characteristic was used to evaluate the performance of the ultrasonic model for SIS stage evaluation., Results: Finally, a total of 223 early-stage and 101 advanced-stage SIS patients were randomly divided into a training cohort (n = 227) and a validation cohort (n = 97). After feature-dimensionality reduction, a total of 28 radiomic features were submitted to LASSO analysis. Finally, 10 radiomic features were finally included for radiomics model construction. The AUC results showed that the ultrasomics model had moderate performance for SIS stage evaluation in both the training cohort (AUC = 0.839) and the validation cohort (AUC = 0.789)., Conclusions: ML-derived ultrasomics can discriminate the SIS stage in patients with SIS. This noninvasive and low-cost approach may be helpful in the preliminary screening of shoulder pain., (© 2021 American Institute of Ultrasound in Medicine.)

Purpose: To evaluate the effects of muscle shortening manoeuvre (MSM) by sonography (US) in professional water polo players with shoulder impingement syndrome (SIS)., Methods: Twenty-four professional water polo players (mean age: 22.13 ± 3.34) with SIS were assigned to one of 2 different treatment interventions: Group (1) MSM: a series of fast accelerations in the upward direction was applied to the upper limb that's connected to a spring through a metal plate with a ring. The ring was linked to a pulley system that was submitted to forces acting in the opposite direction (added mass). Group (2) Simple traction: the series of fast accelerations were performed without the springs. Pain intensity, Yocum and Hawkins tests for SIS, Neer's impingement sign, range of motion, muscle strength and shoulder US were assessed. The examination was performed before, immediately after and 30 days after each treatment to study the US width of subacromial-subdeltoid bursa (SSB), thickness of supraspinatus (ST), long biceps tendons (LBT); hypoechoic halo of surrounding the long biceps (LBH) and subscapular tendons (STH); width of acromio-clavicular joint capsule (ACJ) and the distance between bone heads (ACD). Impingement sign (IS) was evaluated by dynamic examination., Results: Immediately after treatment with MSM, pain was much reduced (p = 0.002); Yocum and Hawkins tests were decreased (p = 0.008, p = 0.031); Neer's impingement sign was negative; range of motion and muscle strength were increased. US showed that the following parameters were significantly reduced: SSB (p = 0.001), LBT (p = 0.014), LBH (p = 0.014), SSH (p = 0.002), ACJ (p = 0.004), ACD (p = 0.001). IS was no more detected. After 30 days, the improvement of clinical and US findings was maintained. In the control group, after simple traction, no clinical amelioration of US parameters was found immediately after the procedure., Conclusion: These data show that MSM could be significantly and rapidly effective against pain and the loss of function due to shoulder impingement in water polo players., (© 2022. Società Italiana di Ultrasonologia in Medicina e Biologia (SIUMB).)

Objective: To develop a new classification of acromion based on the subacromial impingement theory and the Rockwood tilt view. And explore the application value of the new classification in the diagnosis and treatment of rotator cuff tear., Methods: The clinical data of 101 patients underwent shoulder arthroscopic surgery for impingement syndrome or rotator cuff tear from January to December 2017 were retrospectively analyzed. There were 34 males and 67 females, aged from 34 to 76 years with an average of (56.31±9.63) years old, course of disease from 2 to 12 months with average of 6 months. Preoperative radiographs of the routine anteroposterior view, Rockwood tilt view and the supraspinatus outlet view were obtained. Based on the subacromial impingement theory and Rockwood radiographs, the morphology of the acromion can be divided into three types:typeⅠ(flat type), typeⅡ(bump type), and type Ⅲ (impingement type). Two observers classified 101 shoulder Rockwood radiographs according to the new classification method and the supraspinatus Outlet radiographs according to the traditional acromial morphological classification method. Supraspinatus tendon injuries were classified into no tear, partial-thickness tear, and full-thickness tear according to the arthroscopic findings. Concordance test (Kappa value) between the inter-observer and intra-observer was carried out for the new classification method and the traditional classification method respectively. The rank sum test was used to compare the mean acromiohumeral distance(AHD) of the three acromion forms in the new acromion classification method. Spearman rank correlation test and Gamma method were used to analyze the correlation between the new acromion classification method and the degree of supraspinatus tendon tear., Results: The inter-observer consistency analysis of the new classification system was significantly better than that of the traditional classification (0.827 vs 0.278), the intra-observer consistency analysis of the new classification system were also significantly better than that of the traditional classification (0.921 vs 0.448, 0.890 vs 0.539). There was no statistical significance in the AHD among three types of the new classification( H =2.186, P >0.05). In all 101 patients, the highest proportion of impingement type acromion was 45.5% (46 cases), followed by bump type acromion was 36.6% (37 cases), and flat type acromion was 17.8% (18 cases). The incidence of supraspinatus tendon tear in the patients with impingement type acromion was significantly higher than that of the other two types of acromion, there was a spearman rank correlation between the new acromion type and the degree of the supraspinatus tendon tear( rs =0.719, P <0.001)., Conclusion: Rockwood radiographs of the shoulder can well display the anterolateral osteophytes of the acromion. The new acromion classification method based on Rockwood radiographs has high reliability and good reproducibility, in which impingement type of acromion is closely related to supraspinatus tendon tear. Compared with the traditional classification and AHD, the new classification method has more diagnostic value than for rotator cuff injury.

BACKGROUND The aim of this study was to identify the diagnostic magnetic resonance imaging (MRI) findings in 47 shoulders with subcoracoid impingement syndrome by comparison with 100 normal shoulders. MATERIAL AND METHODS The subcoracoid impingement syndrome group consisted of 47 shoulders with subcoracoid impingement syndrome and the normal group consisted of 100 normal shoulders. The MRI parameters - coracoids-humeral distance (CHD), coracoid index (CI), height of the lesser tuberosity (HLT), coracoid obliquity (CO), coracoglenoid angle (CGA), coracohumeral angle (CHA), width of the subscapular tendon (WST), and contact distance between subscapular tendon and coracoid process (CD) - were compared between the subcoracoid impingement syndrome group and the normal group. The areas under the curves (AUCs) from the receiver operating characteristic (ROC) for single MRI parameters were recorded, in which the MRI parameters with AUC exceeding 0.70 were included in the analysis of combined parameters. Comparisons of ROC were made among single parameters and combined parameters. RESULTS For diagnosing subcoracoid impingement syndrome by using single MRI parameters (CHD, CI, HLT, CGA, CHA, WST, and CD), the AUCs were 0.963, 0.806, 0.745, 0.691, 0.613, 0.685, and 0.614, respectively, of which CHD had the largest AUC. CHD, CI, and HLT (AUC exceeding 0.70) were included in the study of the combined parameters. The AUC of combined CHD and HLT showed a significantly larger AUC than that of CHD (0.986 vs 0.963, P=0.036), and showed no significant difference compared with that of combined CHD, CI, and HLT (0.986 vs 0.987, P=0.882). CONCLUSIONS Measurement of the coracoid-humeral distance and height of the lesser tuberosity were key MRI diagnostic findings for subcoracoid impingement syndrome.

Introduction: Shoulder impingement syndrome is evaluated radiologically with two-dimensional measurement parameters. None of these measurement parameters accurately reflect the three-dimensional geometry. The purpose of this study was to evaluate the volumetric status of the subacromial space in patients with shoulder impingement syndrome and to investigate its relationship with two-dimensional parameters., Hypothesis: The primary hypothesis of this study is that subacromial volume is reduced in patients with impingement syndrome. The second hypothesis is that the sagittal plane morphology of the acromion reflects the subacromial volume better than the coronal plane morphology., Patients and Methods: This retrospective study consisted of a total of 52 participants: 26 patients with impingement syndrome and 26 controls. Volumetric measurements were performed with using magnetic resonance imaging. The relationship between humerus and acromion was evaluated by acromiohumeral distance. The sagittal plane morphology of the acromion was evaluated with an objective acromial angle, while the coronal plane morphology was evaluated with a lateral acromial angle. The radiological parameters between groups were compared., Results: The mean subacromial volume was significantly smaller in the impingement group compared to the control group (p=0.01). The subacromial volume had a negative correlation with the objective acromial angle (R=-0.46; p=0.01) The mean tendon volume was significantly higher in the impingement group (p<0.001). The mean acromiohumeral distance in the impingement group (6.8mm±1.0mm), was calculated to be significantly lower than the control group (10.1mm±1.5mm) (p<0.001). There was a positive moderate correlation between subacromial volume and acromiohumeral distance (R=0.61; p=0.01)., Discussion: This is the first study to demonstrate a reduction in subacromial volume in patients with impingement syndrome. The sagittal plane morphology of the acromion, rather than the coronal plane, appears to be more closely related to the subacromial volume., Level of Evidence: III; case-control study., (Copyright © 2021 Elsevier Masson SAS. All rights reserved.)

Background: Subacromial impingement (SAI) may be a cause of age-related rotator cuff abnormalities; therefore, the purpose of this study was to compare SAI characteristics between younger and older adults. In addition to the fact that thickened supraspinatus tendon (SST) indicates tendon abnormalities, SAI characteristics have been recognized as follows: greater SST thickness, reduced acromiohumeral distance (AHD), greater reduction of AHD (∆AHD) with arm elevation, and a higher percentage of SST within AHD (i.e., occupation ratio: OcAHD). Furthermore, we investigated the relationships between SST thickness and AHD, as well as SST thickness and ∆AHD to clarify the effect of SAI on rotator cuff abnormalities., Methods: Healthy younger (n = 18, 21-24-year-old) and older (n = 27, 45-80-year-old) adults without any shoulder symptoms participated in this study. We measured their SST thickness and AHD at rest and at arm elevation (30° and 60°) in the scapular plane using ultrasound, and calculated ∆AHD as the relative change expressed as a percentage of the baseline. OcAHD was expressed as the ratio of SST thickness at rest to AHD at rest and in elevated positions., Results: The older subjects had approximately one mm thicker SST (P = 0.003, 95% Confidence interval [CI] = 0.410 to 1.895) and approximately 1.0 to 1.3 mm greater AHD than the younger subjects (P = 0.011, 95%CI = 0.284 to 2.068 at rest; P = 0.037, 95%CI = 0.082 to 2.609 for 30° of arm elevation; P = 0.032, 95%CI = 0.120 to 2.458 for 60° of arm elevation). However, there were no differences in ΔAHD and OcAHD between the groups., Conclusion: This study demonstrated that, compared with the younger subjects, the older subjects showed thicker supraspinatus tendon but no other SAI characteristics including decreases in AHD and increases in OcAHD. Thus, this study suggests that older subjects showed age-related SST abnormalities without SAI, although the magnitude of the differences in SST thickness is notably small and the clinical significance of this difference is unclear., (© 2022. The Author(s).)

CME Sonography 103: Subacromial Pain Syndrome (SAPS) and Subcoracoid Impingement (SCI) Abstract. Pain in the shoulder can have its origin in different structures of the shoulder joint or in affected periarticular structures. Therefore, it is important to be able to make a specific diagnosis and identify the exact pathology behind it in order to initiate the most appropriate individually precise treatment. In this review, we discuss possible causes of impingement of the shoulder.

Background: Shoulder impingement syndrome (SIS) is the most common form of shoulder pain. Conservative and surgical treatments for SIS are often not effective. One such surgical intervention is subacromial decompression, aimed at widening the subacromial space (SAS). A better understanding of the changes in the SAS may help explain the relative ineffectiveness of current interventions., Objective: To measure the acromiohumeral distance (AHD) and supraspinatus tendon thickness (STT) in people with SIS using a case control study., Methods: The AHD and STT of 39 participants with SIS ≥3 months and 39 age, gender and dominant arm matched controls were measured using ultrasound imaging. Between-group differences for AHD and STT were compared using t-tests. A linear regression was used to determine if there was a relationship between AHD and STT measures, with group as a covariate., Results: Compared to controls (mean age 55.7 years, SD 10.6), individuals with SIS (mean age 57.1 years, SD 11.1) had a significantly larger AHD (mean difference 2.14 mm, 95% CI 1.21, 3.07, p < 0.001) and STT (mean difference 1.25 mm, 95% CI 0.60, 1.90, p < 0.001). The linear regression model indicated an association between AHD and STT (β = 0.59, 95% CI 0.29, 0.89, p < 0.01, R 2  = 0.35, n = 78), suggesting that as STT increases in size, so does the AHD., Conclusion: Individuals with SIS had a larger AHD and greater STT than controls. These results suggest the SAS is already wider in people with SIS and that the symptoms associated with SIS may be more related to an increased STT than a smaller SAS., (© 2021. The Author(s).)

Purpose: The acromiohumeral distance is in practice often evaluated on MRI by radiologists and a reduction diagnosed as subacromial impingement. However, the acromiohumeral distance as indicator for a decentered glenohumeral joint is defined on a true AP radiograph with the patient standing or sitting. The present study therefore evaluated the influence of the patient position by comparing the acromiohumeral distance in both modalities in shoulders with an intact rotator cuff., Methods: On MRI images and true AP radiographs of patients > 20 and < 80 years with an intact rotator cuff the acromiohumeral distance was measured. The maximum cranio-caudal size of the glenoid was measured as a reference to allow a direct comparison of both modalities., Results: Two-hundred and thirty-four shoulders (mean patients age 45.8 ± 14.3 years) were included. The mean acromiohumeral distance/glenoid size ratio of all shoulders was significantly larger (P < 0.0001) on the MRI with 4.6 ± 1.0 in comparison to 4.1 ± 0.9 in the radiographs indicating a smaller acromiohumeral distance on the MRI. In absolute values, a mean acromiohumeral distance of 9.2 mm ± 1.8 on MRI in comparison to 10.4 mm ± 2.4 on the radiographs was calculated. Herewith, the acromiohumeral distance in the MRI was in the average 1.2 mm ± 2.1 (13%) smaller than the in corresponding radiographs (P < 0.0001)., Conclusion: The acromiohumeral distance is significantly smaller in the MRI in comparison to AP radiographs in shoulders with an intact rotator cuff and should not be used as a decision criterion on MRI to assess glenohumeral centering or subacromial space width., Level of Evidence: IV.

To find out which structure is crucial for the formation of shoulder impingement syndrome with the purpose of directing surgical procedures of subacromial decompression and discussing whether it is necessary to manage acromioclavicular joint during operation and how to do it properly., Methods: This was a retrospective study. Clinical data and preoperative computed tomography (CT) images were collected from patients who were diagnosed with rotator cuff tears between January 2017 and August 2019 (sample size: 46) and those who were diagnosed without rotator cuff tears between March 2018 and August 2019 (sample size: 44) in our institution, respectively. Three-dimensional models of shoulders were established by multiplanar reconstruction of CT scans and measurements were performed on these models. The parameters such as the acromial length and width, the axial tilt, and the distance from acromial margin to glenoid plane were measured in an adjusted axial plane, and the critical shoulder angle and the spatial volume under acromioclavicular joint were measured in an adjusted coronal plane. The demographic characteristics, the acromial morphology and the spatial volume under acromioclavicular joint were compared to find significant differences between the two groups. The association between the axial tilt and the distance from acromial margin to glenoid plane was evaluated by an ordinary least squares linear regression., Results: The patients with rotator cuff tears consisted of 16 males and 30 females, among which 30 right shoulders and 16 left shoulders were included. The patients without rotator cuff tears consisted of 28 males and 16 females, among which 15 right shoulders and 29 left shoulders were involved. Significant differences between the groups were found in the acromial width (3.332 cm vs 3.111 cm), the axial tilt (33.765° vs 23.829°), the critical shoulder angle (32.630° vs 30.363°), the distance from anterior 3 cm of lateral acromial margin (range, 2.476 cm-3.302 cm vs 1.993 cm-3.089 cm), and anterior 0.9 cm of medial acromial margin (range, 0.967 cm-2.369 cm vs 0.668 cm-1.993 cm) to glenoid plane, and the spatial volume under acromioclavicular joint (1.089 cm vs 1.446 cm) in the two groups. No significant differences were found in the age (60.0 years vs 58.3 years) or the acromial length (4.187 cm vs 4.184 cm). Significant association was revealed by linear regression analysis between the axial tilt and the distance from anterior two-thirds of lateral acromial margin to glenoid plane, and similar association was also found in the anterior half of medial margin., Conclusion: Anterior two-thirds of lateral acromial margin, anterior half of medial acromial margin, and inferior aspect of acromioclavicular joint are crucial structures and need to be fully decompressed when treating patients with rotator cuff tears., (© 2021 The Authors. Orthopaedic Surgery published by Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.)

Objectives: The study aimed to investigate whether the shoulder tendons changed their elasticity after ultrasound-guided peritendinous or intrabursal corticosteroid injections., Design: Post hoc secondary analysis of a double-blinded, randomized controlled study with 3 months of follow-up., Setting: Outpatient rehabilitation clinic., Participants: Patients with subacromial impingement syndrome (N=60)., Interventions: Patients with unilateral shoulder pain were randomly assigned to receive standard ultrasound-guided subacromial or dual-target corticosteroid injections. The supraspinatus tendons were exposed to 40 mg triamcinolone acetonide in the formal group, whereas the long head of the biceps brachii tendons (LHBT) and supraspinatus tendons were individually infiltrated by 20 mg triamcinolone acetonide in the latter group. Patients' bilateral shoulders were divided into group 1 (n=30, receiving standard subacromial injections), group 2 (n=30, receiving dual-target injections), and group 3 (n=60, without injections)., Main Outcome Measures: Strain ratio of LHBT and supraspinatus tendons using ultrasound elastography., Results: The repeated-measures analysis of variance revealed no intragroup difference of the strain ratio of the LHBT (P=.412 for group 1, P=.936 for group 2, P=.131 for group 3) and supraspinatus tendon (P=.309 for group 1, P=.067 for group 2, P=.860 for group 3) across the 3 time points. Treating group 3 as the reference, the linear mixed model revealed no significant changes in tendon elasticity after either the standard subacromial injection (P=.205 for the LHBT and P=.529 for the supraspinatus tendon) or the dual-target injection (P=.961 for the LHBT and P=.831 for the supraspinatus tendon)., Conclusions: Elasticity of the LHBT and supraspinatus tendons is unlikely to change after a single dose of peritendinous or intrabursal corticosteroid injections. Future studies with a shorter follow-up interval are needed to validate whether corticosteroid injections can cause transient changes of the tendon's elasticity., (Copyright © 2020 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.)

An adult old cyclist presented to our hospital and was referred to the orthopaedic department with a left shoulder posterolateral acromion avulsion fracture and subacromial impingement demonstrated on X-ray and CT. This highly unusual fracture pattern was treated by open reduction and internal fixation with cannulated screws and a tension band suture technique. This fracture went onto successful union with full range of motion and good patient-reported outcome measures by the Oxford Shoulder Score at 3 months. Informed consent was taken for the following case report., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Coracoid impingement syndrome is an increasingly recognized etiology of anterior shoulder pain. Numerus studies have documented the coracohumeral distance (CHD) as a primary or secondary measurement in symptomatic individuals, but there lacks an evaluation of CHD in a large cohort of asymptomatic individuals. The purpose of this study was to quantify a normative distribution of the CHD in a large cohort of healthy, asymptomatic subjects with no history of impingement or shoulder instability., Methods: Incoming first-year students in the United States Military Academy were offered enrollment in this study as part of a prospective cohort to assess the normal anatomic relationships of the shoulder girdle. Magnetic resonance images were obtained, and a board-certified, fellowship-trained musculoskeletal radiologist performed measurements of the smallest distance from the coracoid to the humeral head on axial images., Results: Magnetic resonance images of 714 subjects were available for analysis, including 630 males and 84 females, with a total of 1120 individual shoulders with images of adequate quality. The mean CHD for all shoulders imaged was 13.7 mm. The mean CHD in male shoulders was 13.8 mm, and in female subjects the average was 12.4 mm., Conclusions: This study is the largest of its kind to evaluate the CHD in asymptomatic, healthy shoulders to date and demonstrates a mean CHD of 13.7 mm for all subjects. This information can help to standardize "normal" ranges and act as a comparison for future work, when taken in the context of age and imaging in neutral rotation., (Copyright © 2020 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.)

Objectives: To assess the long-term efficacy of arthroscopic subacromial decompression (ASD) by comparing it with diagnostic arthroscopy (primary comparison), a placebo surgical intervention, and with a non-operative alternative, exercise therapy (secondary comparison)., Methods: We conducted a multicentre, three group, randomised, controlled superiority trial. We included 210 patients aged 35-65 years, who had symptoms consistent with shoulder impingement syndrome for more than 3 months. 175 participants (83%) completed the 5 years follow-up. Patient enrolment began on 1 February 2005 and the 5-year follow-up was completed by 10 October 2018. The two primary outcomes were shoulder pain at rest and on arm activity measured with Visual Analogue Scale (VAS). Minimally important difference (MID) was set at 15. We used a mixed-model repeated measurements analysis of variance with participant as a random factor, the baseline value as a covariate and assuming a covariance structure with compound symmetry., Results: In the primary intention to treat analysis (ASD vs diagnostic arthroscopy), there were no between-group differences that exceeded the MID for the primary outcomes at 5 years: the mean difference between groups (ASD minus diagnostic arthroscopy) in pain VAS were -2.0 (95% CI -8.5 to 4.6; p=0.56) at rest and -8.0 (-17.3 to 1.3; p=0.093) on arm activity. There were no between-group differences in the secondary outcomes or adverse events that exceeded the MID. In our secondary comparison (ASD vs exercise therapy), the mean differences between groups (ASD minus exercise therapy) in pain VAS were 1.0 (-5.6 to 7.6; p=0.77) at rest and -3.9 (-12.8 to 5.1; p=0.40) on arm activity. There were no significant between-group differences for the secondary outcomes or adverse events., Conclusions: ASD provided no benefit over diagnostic arthroscopy (or exercise therapy) at 5 years for patients with shoulder impingement syndrome., Competing Interests: Competing interests: ST reports personal fees from Evalua group of companies, personal fees from DBC group of companies, and personal fees from insurance companies, outside the submitted work., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY. Published by BMJ.)

Purpose: Frozen shoulder is characterized by pain and reduced passive movement capability, and the diagnose is made clinically. However, pain is the major symptom in the first stage before stiffness occurs, and the condition can be mistaken for subacromial impingement. This study explored the possibility to use positron emission tomography/computed tomography (PET/CT) with a 18 F Flour-Deoxy-Glucose (FDG) tracer in the diagnostic process., Methods: Eleven patients with frozen shoulder and 9 patients with subacromial impingement received a 18 F-FDG PET/CT scan before being treated surgically. During arthroscopy, the diagnoses were confirmed. Images were blindly analyzed visually by two nuclear medicine physicians. Also, semi-quantified analysis applying a set of standard regions was performed, and standard uptake value in both shoulder regions was recorded., Results: Both the visual description of the pictures and the semi-quantified analysis generally showed increased FDG uptake in the affected shoulder regions of patients that had frozen shoulder and no uptake in patients with subacromial impingement. Kappa for interobserver agreement in the visual assessments was 0.74. Sensitivity was 92% and specificity 93% of the visual assessment, 77% and 93%, respectively, of the semi-quantified analyses, and by combining the two types of analyses sensitivity was 100% and specificity was 93% for the distinction between frozen shoulders and subacromial impingement/unaffected shoulders., Conclusion: 18 F-FDG PET/CT seems to be a valid method to diagnose frozen shoulder. This is clinically relevant in diagnostically challenging cases, for instance in the first phase of frozen shoulder, which can be difficult to distinguish from subacromial impingement., Level of Evidence: II.

Background: Shoulder impingement syndrome (SIS) is the most common form of shoulder pain and a persistent musculoskeletal problem. Conservative and invasive treatments, aimed at the shoulder joint, have had limited success. Research suggests shoulder function is related to thoracic posture, but it is unknown whether thoracic posture is associated with SIS., Objective: The objective of this study was to investigate whether there is a relationship between SIS and thoracic posture., Design: This was a case control study., Methods: Thoracic posture of 39 participants with SIS and 39 age-, gender-, and dominant arm-matched controls was measured using the modified Cobb angle from a standing lateral radiograph. Thoracic range of motion (ROM) was also measured using an inclinometer. Between-group differences were compared using t tests. The relationship between thoracic posture and thoracic ROM was determined with linear regression., Results: Twenty women and 19 men with SIS (mean age = 57.1 years, SD = 11.1) and 39 age-matched, gender-matched, and dominant arm-matched controls (mean age = 55.7years, SD = 10.6) participated. Individuals with SIS had greater thoracic kyphosis (mean difference = 6.2o, 95% CI 2.0-10.4) and less active thoracic extension (7.8o, 95% CI = 2.2-13.4). Greater thoracic kyphosis was associated with less extension ROM (ie, more flexion when attempting full extension: β = 0.71, 95% CI = 0.45-0.97)., Limitations: These cross-sectional data can only demonstrate association and not causation. Both radiographic measurements and inclinometer measurements were not blinded., Conclusion: Individuals with SIS had a greater thoracic kyphosis and less extension ROM than age- and gender-matched healthy controls. These results suggest that clinicians could consider addressing the thoracic spine in patients with SIS., (© 2019 American Physical Therapy Association.)

Purpose: Several radiographic parameters describe humeral head coverage by the acromion. We describe a new radiographic measurement, the acromion-greater tuberosity impingement index (ATI), and its ability to predict rotator cuff pathology., Methods: The ATI was measured with magnetic resonance imaging (MRI) and X-ray analysis in 83 patients with rotator cuff pathology and 76 patients with acute rotator cuff tears. The lateral acromial angle (LAA), acromion type, the acromion index (AI) and the critical shoulder angle (CSA) were measured to assess their correlations with the ATI. Receiver operating characteristic (ROC) curves were used to predict degenerative rotator cuff pathology. The change in the ATI after acromion surgery was evaluated in both groups., Results: According to the ROC curves, the ATI is a good predictor of degenerative rotator cuff pathology on both X-ray (cut-off, 0.865) and MRI (cut-off, 0.965). Patients with degenerative rotator cuff pathology had a significantly higher average ATI compared to the trauma group ( p = 0.001 for X-ray and MRI). The degenerative group had a significantly lower LAA ( p = 0.001) and a higher ratio of type III acromion ( p = 0.035) than the trauma group. The ATI on X-ray was negatively related to the LAA and positively related to the AI, the CSA and acromion type (each p < 0.05). The ATI on MRI was negatively related to the LAA and positively related to the AI and acromion type (each p <0.05). More patients in the degenerative group than the trauma group needed acromioplasty or acromion decompression ( p < 0.05). The ATI on MRI was significantly lower after acromion surgery compared to before surgery in both groups ( p < 0.05)., Conclusion: The ATI is a good predictor of degenerative supraspinatus tendon tears or subacromial impingement syndrome. The ATI on MRI is more accurate and can precisely guide acromion surgery.

Background: We hypothesized that cervical radiculopathy (CR) has a role in subacromial impingement syndrome (SAIS) etiology, which cannot be directly connected to anatomical causes., Objective: We aimed to investigate the presence of cervical radiculopathy in patients with SAIS diagnosed clinically and radiologically., Methods: Patients who had a clinical and radiological SAIS diagnosis between 2014 and 2016 were included in the study. Patients with secondary causes that led to SAIS were excluded. Cervical MRI of all patients with SAIS was examined for cervical radiculopathy., Results: A significant (p< 0.05) relationship was found between SIAS and the presence of root compression on the same side. 35% of the patients with SIAS had root compression on the same side., Conclusions: Cervical radiculopathy and shoulder impingement syndrome can be easily confused due to the similarity of the symptoms and the anatomical proximity of the lesions. Although both diseases can occur with different mechanisms, we believe that there is a cause and effect relationship between them.

Background: The purpose of this study to compare glenohumeral joint motion during active shoulder axial rotation between subacromial impingement syndrome (SIS) shoulders and asymptomatic shoulders using cine-magnetic resonance imaging (cine-MRI). Measurement of glenohumeral joint motion via manual intervention does not assess the usual glenohumeral joint motion, and the glenoid surface cannot be confirmed manually. However, cine-MRI can produce clear images of glenohumeral joint rotation. Therefore, we sought to measure the active ROM of the glenohumeral rotation using cine-MRI., Methods: Seventy-three shoulders in 42 asymptomatic volunteers and 110 SIS shoulders in 103 consecutive patients were included in this study. We evaluated 36 matched pairs (72 shoulders in total) adjusting for baseline characteristics with propensity score matching method. The patients underwent cine-MRI during axial rotation of the adducted arm. During imaging, participants rotated their shoulder from the maximum internal rotation to the maximum external rotation over the first 10 s and then back to the maximum internal rotation over the subsequent 10 s. We assessed internal/external rotation, and compared the asymptomatic and SIS shoulders in this regard. Evaluation of rotation angles was performed on a series of axial images through the humeral head center., Results: The mean internal rotation angles of the asymptomatic and patient groups were 55° ± 10° and 41° ± 23°, respectively, (P = .002; 95% Confidence Interval [CI], 51-58 vs 33-49); the mean external rotation angles were 47° ± 15° and 21° ± 25°, respectively, (P < .001; CI, 42-52 vs 13-29)., Conclusions: Compared to asymptomatic shoulders, SIS shoulders showed significantly restricted glenohumeral rotation as determined by cine-MRI. Our results suggested that the significant limitation of active glenohumeral rotation might be associated with rotator cuff dysfunction.

Purpose: Greater tuberosity fractures are challenging lesions concerning decision-making. In order to improve our treatment algorithm, we developed a new method, which allows predicting a possible subacromial conflict on standard anteroposterior radiographs, considering not only the displacement of the fragment but also the width of the subacromial space., Methods: The measurement technique consisted of drawing three concentric circles on true anteroposterior radiographs. The inner circle (radius Rh) perfectly matched the humeral head surface. The medial circle (radius Rt) was tangent to the greater tuberosity, and the outer circle (radius Ra) touched the undersurface of the acromion. The ratio Rt/Rh, which describes how much the greater tuberosity projects above the articular surface, and the relationship (Rt-Rh)/(Ra-Rh), which quantifies the space occupied by the greater tuberosity under the acromion, were calculated and called Greater Tuberosity Index and Impingement Index, respectively. Five dry humeri were used to assess the influence of rotation and abduction on the Greater Tuberosity Index. The radiographs of 80 shoulders without any osseous pathology were analyzed to obtain reference values for both indices. Finally, greater tuberosity fractures with different displacements were created in five cadaver specimens, and subacromial impingement was correlated with these parameters., Results: On anteroposterior radiographs, the greater tuberosity was most prominent in neutral rotation, regardless of abduction. In shoulders without osseous pathology, the Greater Tuberosity Index and the Impingement Index averaged 1.15 (range 1.06-1.28) and 0.46 (range 0.21-0.67). In the biomechanical experiments, the Impingement Index was a better discriminator for subacromial impingement than the Greater Tuberosity Index. A fracture with a displacement corresponding to an Impingement Index of 0.71 or greater was associated with subacromial impingement., Conclusions: Reduction of a displaced greater tuberosity fragment should be considered if the Impingement Index is 0.7 or greater. The measurement method is simple and reliable and has the potential to be used for the assessment of subacromial impingement in other conditions.

Objective: To evaluate the relationships between acromial anatomy and developmental alterations with rotator cuff tears in female patients and compare these parameters on radiographs and corresponding MRIs along with inter-reader performance., Materials and Methods: Patient demographics, symptoms, and acromial characteristics on radiograph (acromial index, lateral acromion angle, subacromial space on AP and Y- views, acromial anterior and lateral downsloping) and MRI (shape, slope, spur, osteoarthrosis, os acromiale) were recorded. Radiographic and MRI findings were compared and correlated with rotator cuff pathology on MRI. Inter-reader analysis was performed., Results: A total of 140 MRIs from 137 female patients were included. No significant correlation (p > 0.05) existed between acromial parameters and rotator cuff tears, except for a smaller subacromial space on the Y view and spurs correlated with subscapularis tendon tear (p = 0.02, p = 0.04). The presence of lateral downsloping on MRI correlated with a smaller lateral acromion angle (p = 0.0002) and the presence of lateral downsloping on radiography (p = 0.0015). Inter-reader agreements were good to excellent (ICC: 0.65-0.89)., Conclusion: Subacromial impingement anatomy characteristics have no significant associations with supraspinatus or infraspinatus tears in symptomatic women. Among different measures, supine MRI can be reliably used to identify lateral downsloping of the acromion.

Objective: Subacromial impingement syndrome is one of the most common causes of pain in the shoulder. To this date, there is no specific radiographic view that can be used to evaluate the size of a subacromial spur. This study aims to examine a cassette tilt view can be used to evaluate the size of a subacromial spur., Methods: A cross-sectional study was conducted between the time period of January 1, 2016, and December 31, 2016. Forty-three consecutive patients that had planned treatment of arthroscopic subacromial decompression (SAD) participated in this study. Rockwood view and cassette tilt view (caudal tilt 30  with beam and cassette) X-rays were done in all these patients. The measurements of the spur sizes were calculated from both views and were compared to the spur sizes measured intraoperatively., Result: The size of the spurs from intraoperative measurement was not significantly different from the spur size measured using the cassette tilt view with a mean difference of 0.54 (95% confidence interval (CI): - 0.58, 1.65), but the intraoperative measurement was significantly different from the Rockwood view spur measurement, with a mean difference of 2.84 (95% CI: 1.56, 4.11). Average proportions of the size of the spur from the cassette tilt and Rockwood view compared to that from intraoperative measurements were 1.09 and 1.55, respectively., Conclusion: The cassette tilt view is a simple method of measurement of the size of subacromial spurs, with good inter- and intra-observer reliabilities and good validity. This can be useful clinically when setting the patient position and portals to evaluate the size of the spur when planning SAD., Level of Evidence: This is level III.

Purpose: The purpose of this study was to investigate the natural history of intact rotator cuff in impingement syndrome patients with concomitant spur protruding from the undersurface of acromion., Methods: This retrospective study included 119 patients with an intact rotator cuff who underwent conservative treatment for a spur protruding from the undersurface of the acromion. The protruded spur was defined as a trapezoid- or tetragon-shaped bony protrusion with a downward peak extending more than 3 mm in length from the baseline drawn along the acromial undersurface on the coronal view of magnetic resonance imaging (MRI) or computed tomography arthrography (CTA). Functional outcomes were evaluated by the visual analogue scale for pain, subjective shoulder value, American Shoulder and Elbow Surgeons score, University of California Los Angeles shoulder score, and active range of motion (ROM). To evaluate cuff integrity, follow-up MRI, CTA, or ultrasound were performed at least 2 years after the initial presentation., Results: No new rotator cuff tears were noted in any patient during the follow-up imaging studies. However, 18 patients (15%) underwent arthroscopic acromioplasty during the study period. During the arthroscopic examinations, moderate to severe attrition of the cuff was identified, although no tears were seen. At the final follow-up, pain level and shoulder function, including ROM, showed satisfactory outcomes., Conclusion: Spurs protruding from the acromial undersurface did not lead to rotator cuff tears during 2-5 years of conservative treatment. However, attrition of the rotator cuff was found during arthroscopic acromioplasty, suggesting that the protruding spurs caused extrinsic impingement of the cuff., Level of Evidence: Therapeutic case series Level IV.

The authors sought to compare the accuracy and effectiveness of the mid-lateral and posterior routes of subacromial injection. They conducted a prospective randomized study involving 50 shoulders scheduled to receive subacromial injection via the midlateral or posterior route. After injection, a blinded musculoskeletal radiologist interpreted the radiographs. Age, sex, body mass index, side of shoulder involved, circumference of the proximal humerus, and acromial type were assessed. The accuracy rates of the injections, modified University of California Los Angeles shoulder scores, and visual analog scale pain scores were compared. The accuracy rate of the midlateral route was significantly higher than that of the posterior route (92% vs 68%; P<.034). Although there were significantly improved modified University of California Los Angeles shoulder and visual analog scale pain scores in both groups after injection, differences in functional outcomes were not statistically significant (P>.05). Univariate analysis showed no correlation between accuracy and age, sex, body mass index, or circumference of the proximal humerus. However, injection route had some influence on accuracy, with a crude odds ratio of 5.41 (95% confidence interval, 1.017-28.791; P=.048) for the midlateral route. Midlateral was the preferred route for subacromial injection. [Orthopedics. 2019; 42(1):e44-e50.]., (Copyright 2018, SLACK Incorporated.)

Background: The primary indication for reverse shoulder arthroplasty (RSA) is rotator cuff arthropathy caused by a deficient rotator cuff. Cuff deficiency in patients is highly variable in its distribution and extent, with mechanical implications that may significantly affect post-operative recovery. This study investigated the effects of variable cuff deficiency on the propensity for impingement between the scapula and humeral component and resulting subluxation, the source of two common complications (scapular notching and instability)., Methods: Five different finite element models of an RSA were analyzed with varying degrees of rotator cuff deficiency: (1) baseline, with intact subscapularis, infraspinatus and teres minor, (2) no subscapularis, (3) no subscapularis or infraspinatus, (4) no infraspinatus, and (5) no infraspinatus or teres minor. The supraspinatus was not included in any models, as it is absent in rotator cuff arthropathy. Each model was moved through a prescribed arc of 45° internal/ external rotation originating from neutral., Results: Greater rotator cuff deficiency was associated with more impingement and larger magnitudes of subluxation. The largest subluxation (7.5 mm) and highest impingement-related contact stress (479 MPa) was in the model lacking all rotator cuff muscle groups. Posterior subluxation was present in most models lacking the infraspinatus, while anterior subluxation was present in all models lacking the subscapularis., Conclusions: This study helps clarify how different rotator cuff deficiencies influence shoulder stability following RSA and can ultimately help predict which patients may be at greater risk for impingement-related scapular notching and subluxation., Clinical Relevance: Surgeons should carefully consider the nature of the rotator cuff deficiency and its influence on impingement and instability when planning for RSA. Level of Evidence: V., Competing Interests: Disclosures: The authors report no potential conflicts of interest related to this study.