Acromion Index Research Articles

Possibility of diagnosing rotator cuff tears in areas with scarce medical resources: can non-standard anteroposterior radiographs accurately predict rotator cuff tears?

Due to the scarcity and high cost of MRI in resource-constrained regions, prompt diagnosis and treatment of rotator cuff tears remain problematic in these areas. Therefore, extensive research has been conducted to predict rotator cuff tears using simple and affordable anteroposterior radiographs. It remains unclear whether non-standard anteroposterior radiographs would have a notable impact on the preciseness of the diagnosis. We analyzed patients treated for shoulder pain at hospitals. These patients underwent shoulder joint MRI and standard anteroposterior radiographs, were categorized into those with rotator cuff tears and a control group. We assessed whether the radiographs were standard anteroposterior radiographs using classification criteria from previous studies. Three assessors independently measured the acromiohumeral interval, upwards migration index, acromion index, critical shoulder angle, and double-circle radius ratio in radiographic images. The intraclass correlation coefficient and receiver operating characteristic curves were used to assess measurement reliability and predictive capabilities of each predictive method for rotator cuff tears. This study included 102 non-standard radiographs that met the research criteria for the measurement and analysis. The intragroup correlation coefficients for the acromiohumeral interval, upwards migration index, and double-circle radius ratio were above 0.7 (0.77, 0.71, 0.76), while those for the acromion index and critical shoulder angle exceeded 0.8 (0.86 and 0.87). In non-standard radiographs, the double-circle radius ratio reliably predicted rotator cuff tears (p < 0.05), contrary to the other methods (p > 0.05). The areas under the receiver operating characteristic curves of the double-circle radius ratio, estimated by the three researchers for rotator cuff tears. This study found that non-standard radiographs significantly impaired the diagnostic performance of the acromiohumeral interval, upwards migration index, acromion index, and critical shoulder angle. Only the double-circle radius ratio maintained its predictive power (although this diminished capability may fall short of clinical relevance) and demonstrated high applicability. These findings indicate the need for researchers to prioritize the quality of radiographs and focus on reducing the sensitivity of the prediction method in relation to radiograph quality. The capability exhibited by the double-circle radius ratio warrants further investigation, to facilitate a simplified diagnosis of rotator cuff tears.

Comparative Analysis of Critical Shoulder Angle and Acromion Index in Patients with or without Rotator Cuff Tear

Background: Recent evidence suggests that a high value of radiographic acromial indices such as critical shoulder angle (CSA) and acromial index (AI) may be associated with a higher incidence of rotator cuff tears (RCTs). The objective of this observational study was to evaluate the relationship between RCTs, CSA, and AI. Materials and Methods: We divided 68 patients with shoulder pain into two groups: Group 1, RCT and Group 2, normal cuff. Patients were evaluated with standard true anteroposterior (AP) radiographs. CSA and AI were calculated on true AP X-ray. Twenty-four males and 10 females were selected for Group 1 whereas 23 males and 11 females for Group 2. Results: The mean age for Group 1 was 53.23 years and for Group 2 was 47.53 years. CSA findings (mean ± standard deviation [SD]) were 37.5 ± 4.37 for Group 1 and 32.23 ± 3.19 for Group 2. Mean ± SD for AI were 0.72 ± 0.07 and 0.66 ± 0.09 for Groups 1 and 2, respectively. CSA and AI revealed a statistically significant P &lt; 0.0001 for both groups. Logistic regression confirmed CSA and AI to be strong predictors of an RCT. Conclusions: Higher CSA and AI are associated with degenerative RCT. Level of Study: Level III.

The Development of a Yolov8-Based Model for the Measurement of Critical Shoulder Angle (CSA), Lateral Acromion Angle (LAA), and Acromion Index (AI) from Shoulder X-ray Images.

Background: The accurate and effective evaluation of parameters such as critical shoulder angle, lateral acromion angle, and acromion index from shoulder X-ray images is crucial for identifying pathological changes and assessing disease risk in the shoulder joint. Methods: In this study, a YOLOv8-based model was developed to automatically measure these three parameters together, contributing to the existing literature. Initially, YOLOv8 was used to segment the acromion, glenoid, and humerus regions, after which the CSA, LAA angles, and AI between these regions were calculated. The MURA dataset was employed in this study. Results: Segmentation performance was evaluated with the Dice and Jaccard similarity indices, both exceeding 0.9. Statistical analyses of the measurement performance, including Pearson correlation coefficient, RMSE, and ICC values demonstrated that the proposed model exhibits high consistency and similarity with manual measurements. Conclusions: The results indicate that automatic measurement methods align with manual measurements with high accuracy and offer an effective alternative for clinical applications. This study provides valuable insights for the early diagnosis and management of shoulder diseases and makes a significant contribution to existing measurement methods.

The relationship between the shape of rotator cuff tears and shoulder anatomical parameters

BackgroundThe aim of this study is to investigate the potential relationship between shoulder anatomical parameters and the shape of rotator cuff tears (L-shaped, U-shaped, and crescent-shaped).Materials and methodsThe study included 160 (n:160) patients. Patients were divided into four groups: crescent type, u type and L type tears and control group. There were 40 cases in each group. The operated patients were divided into three groups based on the shape of the tears in arthroscopic images. Measurements of Critical Shoulder Angle (CSA), Greater Tuberosity Angle (GTA), Acromion Index (AI), Lateral Acromion Angle (LAA), and Humerus Footprint width (coronal width and sagittal width) were taken in each group and compared.ResultsPatients were divided into four different groups: Crescent type group (n:40), L type group (n:40), U type group (n:40) and control group (n:40). Upon assessing the coronal and sagittal width measurements, The mean coranal width measurement of the L-type tear group was 12.62 ± 0.29 mm, which was significantly higher than all other groups (p < 0.05). The mean sagittal width of the L-type tear group was 34.95 ± 0.29 mm, which was significantly higher than all other groups (p < 0.05). When the groups were evaluated based on GTA, CSA, and AI data, the mean GTA measurement of the L-type tear group was 73.03 ± 0.95 degrees, which was significantly higher than all other groups (p < 0.05). The mean CSA measurement of the L-type tear group was 34.77 ± 0.66 degrees, which was significantly higher than all other groups (p < 0.05). The mean AI measurement of the L-type tear group was 0.77 ± 0.02, which was significantly higher than all other groups (p < 0.05). When the groups were evaluated based on LAA data, the mean LAA measurement of the L-type tear group was 76.98 ± 1.04 degrees, which was significantly lower than all other groups (p < 0.05).ConclusionIn our study, especially in L-shaped tears, measurements of GTA, CSA, AI, LAA, coronal and sagittal width were found to be different compared to the control group. These results suggest that shoulder anatomy affects the mechanisms of rotator cuff tear formation and that these parameters play a more significant role in L-shaped tears.

Interobserver reliability of shoulder radiographic findings and correlation to MRI: a preliminary case series.

The aim of this study was to evaluate the interobserver reliability of measurements of the Acromiohumeral Distance (AHD) first described by Golding et al., the Critical Shoulder Angle (CSA), the Acromion Index with Glenoid Humeral (GH) and Glenoid Acromial (GA) distances, following the measuring method by Nyffeler et al., the Lateral Acromion Angle (LAA), as well as the morphology of the acromion according to Bigliani and the humeral head position according to Maloney in X-rays and MRI. Furthermore, the study assessed the correlation of measurement results in X-ray with those in MRI for AHD, CSA, GA, GH, AI, and LAA. A total of 187 patients who underwent shoulder joint X-ray and MRI examinations from 09/2016 to 05/2023 were included in the study. Patients with poor imaging quality, arthrosis or radical prior surgeries, like shoulder prosthetic surgery, status post humerus fractures, that have undergone surgery and therefore changed the anatomical features were excluded, what lead to a total study population of 78. X-ray measurements were performed by two observers in the true anteroposterior view, so that the humeral head and the glenoid are shown without overlap, providing a clear view into the joint space. MRI measurements were performed in oblique coronal MRI slices, using the most accurately depicted glenoid surface as a landmark. Interobserver measurement results showed a significance with p < 0.001 for the assessment of acromion type according to Bigliani, humeral head offset assessment according to Maloney, and AHD. No significance was found for interobserver reliability in measuring LAA. Additionally, there was a high correlation of measurement results in X-ray with measurements in MRI for, CSA, GH/GA, and consequently AI, a good correlation for AHD but no correlation could be shown for LAA. These findings provide valuable insights into the robustness of radiological parameters for evaluating shoulder pathology, offering promising prospects for clinical applications and further research. Nevertheless, the specific methodological considerations and patient characteristics should be taken into account when interpreting the results to ensure their accurate application in clinical practice.

Critical shoulder angle and acromial index do not influence functional outcomes after repair of massive rotator cuff tears

ObjectivesCritical shoulder angle (CSA) and acromial index (AI) are two radiographic signs that can influence the risk of rotator cuff tears and the outcomes of repair. The purpose of this study was to determine the influence of CSA and AI on massive cuff tears and on the functional outcomes after repair. The hypothesis was that CSA and AI would be higher in posterosuperior compared to anterosuperior tears. MethodsCSA and AI were retrospectively measured on radiographs of patients who underwent repair of two rotator cuff tendons. Functional outcomes were evaluated using the American Shoulder and Elbow Surgeons (ASES) score and Simple Shoulder Test (SST) at least six months postoperatively. Patients were divided according to the tendons repaired into anterosuperior group and posterosuperior group. Radiographic measurements and functional outcomes were compared. Patients in the posterosuperior group were subdivided into low or high CSA (cut-off value ​= ​39), and into low or high AI (cut-off value ​= ​0.75). All available preoperative magnetic resonance images were reviewed and graded according to Goutallier classification. Multivariate analysis was used to determine the influence of CSA, AI and Goutallier grade on functional outcomes. ResultsEighty six patients were included. Both CSA and AI were statistically significantly higher in the posterosuperior group (p ​= ​0.0143 and 0.0052, respectively). After a mean follow-up of 33 months, ASES and SST were significantly better in patients with Goutallier grades 0–1 than grades>1 (multivariate p ​= ​0.03 and 0.009, respectively). No statistically significant differences were found between low and high CSA and AI groups in terms of functional outcomes of the posterosuperior group after repair (multivariate p ​= ​0.9). ConclusionHigher CSA and AI seem to increase the risk of posterosuperior more than anterosuperior rotator cuff tears. Neither of these radiographic parameters influenced the functional outcomes of massive posterosuperior tears after repair. Level of evidenceLevel III.

Partial-Thickness Rotator Cuff Tears: Current Concepts.

» Partial-thickness rotator cuff tears (PTRCTs) are a common pathology with a likely high asymptomatic incidence rate, particularly in the overhead athlete.» The anatomy, 5-layer histology, and relationship to Ellman's classification of PTRCTs have been well studied, with recent interest in radiographic predictors such as the critical shoulder angle and acromial index.» Depending on the definition of tear progression, rates of PTRCT progression range from 4% to 44% and appear related to symptomatology and work/activity level.» Nearly all PTRCTs should be managed conservatively initially, particularly in overhead athletes, with those that fail nonoperative management undergoing arthroscopic debridement ± acromioplasty if <50% thickness or arthroscopic conversion repair or in situ repair if >50% thickness.» Augmentation of PTRCTs is promising, with leukocyte-poor platelet-rich plasma having the most robust body of supportive data. Mesenchymal signaling cell biologics and the variety of scaffold onlay augments require more rigorous studies before regular usage.

Complications and revisions in metal-backed anatomic total shoulder arthroplasty: a comparative study of revision rates between stemless and stemmed humeral components

BackgroundThe primary objective of this study was to evaluate and compare the incidence of complications and revision surgeries between in two of convertible metal-back glenoid systems in total shoulder arthroplasty (aTSA) groups over a follow-up period of up to five years. MethodsA retrospective analysis included 69 shoulders from 65 patients with primary aTSA. Patients were divided into Group 1 (n=31), receiving convertible cementless stemmed aTSA (Lima SMR) and Group 2 (n=38), receiving humeral head replacement aTSA (Arthrex, Eclipse) both with metal-back glenoid components. Clinical and radiological assessments were conducted at 2, 5, and 10 years postoperatively. Assessments included the following: Constant Score, DASH, SPADI, SSV, Glenohumeral Distance, Critical Shoulder Angle and Lateral Acromion Index. In addition, we compared complications, revision rates and survival rates between groups using Kaplan-Maier curves and Log-Rank-test. ResultsBaseline demographics and preoperative outcome scores showed no significant differences between groups (p≥0.05). The overall revision rate did not significantly differ between groups (Group 1:32% vs. Group 2:24%, p=0.60), nor did the mean time to revision (p=0.27). The mean follow-up was 71±41 months (Group 1: 94±48 months, Group 2: 53±23 months, p<0.001). Kaplan-Meier analysis showed similar mid-term survival probabilities (p=0.94). Revision reasons included rotator cuff insufficiency (n=4 in Group 1, n=2 in Group 2) and glenoid wear/loosening (n=5 in Group 1, n=7 in Group 2). Interestingly, Group 1 demonstrated no occurrence of glenoid metal baseplate or humeral loosening, while complex revisions were more common in the Group 2. At 2 and 5 years, non-revised patients in both groups had similar outcome scores. ConclusionMetal-backed glenoid implants in combination with both stemless and stemmed humeral components in aTSA exhibit comparable revision rates and survival probabilities. Rotator cuff insufficiency and polyethylene wear are the two most common complications leading to revision. To facilitate ongoing monitoring and optimize patient safety, we implemented a modification in the follow-up protocol, transitioning to annual appointments or earlier when necessary. This study underscores the unsolved disadvantages in metal-back components and the importance of a mid- to long-term longitudinal assessment of those patients.

Radiographic findings in patients suspected of subacromial impingement syndrome: prevalence and reliability

ObjectiveAims 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 methodsThis 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.ResultsA 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).ConclusionCalcification, 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.

Can coracoacromial ligament degeneration be evaluated with preoperative MRI?

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. To examine the relationship between CAL thickness on preoperative magnetic resonance imaging (MRI), arthroscopic CAL degeneration and types of rotator cuff tears. 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. 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. 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.

Three-dimensional analysis of biplanar glenoid deformities: what are they and can they be virtually reconstructed with anatomic total shoulder arthroplasty implants?

Descriptions of glenoid deformities in glenohumeral osteoarthritis (GHOA) have focused on the axial plane. Less is known regarding arthritic glenoids with higher amounts of superior inclination and little evidence exists to guide management of inclination or combined version-inclination deformity when performing anatomic total shoulder arthroplasty (aTSA). We hypothesized that biplanar deformities (BD) would be present in a higher proportion of GHOA patients than previously appreciated, and these deformities would be difficult to adequately reconstruct with contemporary aTSA implants. A retrospective query was performed of GHOA patients indicated for TSA 2012-2017 with a computed tomography (CT) scan within three months of surgery. Images were uploaded to three-dimensional (3D) software for automated measurements. Glenoids with superior inclination ≥10°, and retroversion ≥20° were considered to have BD. Walch classification was determined, and C-type glenoids were excluded. Rotator-cuff muscle cross-sectional area (CSA) was measured and fatty infiltration was graded. Glenoids withBD were virtually planned for aTSA with correction to neutral inclination and version, then with 5° superior inclination and 10° retroversion. Two-hundred and sixty-eight shoulders in 250 patients were included; average age was 65years, 67% male. There were no differences in inclination between Walch types (P=.25). Twenty-nine shoulders with BD were identified (11%). These deformities were not associated with age (P=.47) or gender (P=.50) but were skewed towards Walch B-type, specifically B2 (P=.03). Acromial index and posterior humeral head subluxation were higher in BD patients (P=.04, P<.001, respectively). Biplanar deformities had similar cuff CSA compared to those without but were less frequently associated with fatty infiltration of the subscapularis (P=.05). When correcting to neutral version and inclination, 41% BD could not be reconstructed. Of those that could, 94% required augmented implants. When correcting to 5° superior inclination and 10° retroversion, 10% could not be reconstructed. Of those that could, 58% required augmented implants. With partial correction, augment use was predicted by retroversion >26° (P=.009). Inclination did not predict augment use (P=.90). Final implant position commonly involved unseating in the posterosuperior quadrant and cancellous exposure in the anteroinferior quadrant. This retrospective computed tomography (CT)-based study of 268 shoulders with GHOA found an 11% prevalence of BD. These deformities were commonly associated with Walch B2 wear patterns. Virtual aTSA planning showed a high failure rate (41%) when correcting to neutral version and inclination. Posteriorly augmented implants were frequently required, and often still involved unseating in the posterosuperior quadrant, increased cancellous exposure in the anteroinferior quadrant, and vault perforation.

The Association between SLAP Lesions and Critical Shoulder Angle and Glenoid Depth.

The critical shoulder angle (CSA) is formed by the combination of glenoid inclination and acromial index and has been shown related to rotator cuff tears and glenohumeral osteoarthritis. SLAP lesions today have an important place among bicipitolabral pathologies that cause intensive shoulder pain. We aimed to investigate the relationship between CSA and glenoid depth and SLAP lesions. Between March 2017 and January 2022, 279 consecutive shoulder arthroscopy patients' MRI images were retrospectively examined. After the exclusion criteria, 191 patients were eligible. Patients with SLAP lesions (n=37) were assembled as the study group (Group 1), and patients with intact superior labrum (n=154) were named as the control group (Group 2). Critical shoulder angle (CSA) and glenoid depth measurements were performed using the preoperative MRI images. A total of 191 patients, of whom 84 were male (44%) were included. The mean age was 49.9±14.96 (range 18-79). There was a statistically signifi cant difference between the SLAP group (Group 1) and the control group (Group 2) in terms of CSA (p=0.032). The mean CSA was 31.66°±3.51° in Group 1 and 33.57° ±5.01° in Group 2. The cut-off value for CSA in patients with SLAP lesions was calculated as 32.85° and the area under the curve was 0.61, therefore a satisfactory association was observed between the groups. The mean glenoid depth was 4.32 ±1.25 mm in Group 1, and 4.39 ±0.32 mm in Group 2. There was no statistically signifi cant difference between the groups in terms of glenoid depth (p=0.136) and also no association between the glenoid depth and SLAP lesions was observed (cut-off=4.45 mm, AUC=0.32). Low CSA is associated with SLAP lesions, just as in glenohumeral osteoarthritis. Further prospective clinical studies are needed to enlighten the predisposing effect of CSA to SLAP lesions and the success of superior labral repairs. Retrospective comparative study, Level III.

Establishing Normative Values for Acromion Anatomy: A Comprehensive MRI-Based Study in a Healthy Population of 996 Participants.

Shoulder pain is a common issue often linked to conditions such as subacromial impingement or rotator cuff lesions. The role of the acromion in these symptoms remains a subject of debate. This study aims to establish standardized values for commonly used acromion dimensions based on whole-body MRI scans of a large and healthy population and to investigate potential correlations between acromion shape and influencing factors such as sex, age, BMI, dominant hand, and shoulder pain. The study used whole-body MRI scans from the Study of Health in Pomerania, a German population-based study. Acromion index, acromion tilt, and acromion slope were measured. Interrater variability was tested with two independent, trained viewers on 100 MRI sequences before actual measurements started. Descriptive statistics and logistic regression were used to evaluate the results. We could define reference values based on a shoulder-healthy population for each acromion parameter within the 2.5 to 97.5 percentile. No significant differences were found in acromion slope, tilt, and index between male and female participants. No significant correlations were observed between acromion morphology and anthropometric parameters such as height, weight, or BMI. No significant differences were observed in acromion parameters between dominant and non-dominant hands or stated pain intensity. This study provides valuable reference values for acromion-related parameters, offering insight into the anatomy of a healthy shoulder. The findings indicate no significant differences in acromion morphology based on sex, weight, BMI, or dominant hand. Further research is necessary to ascertain the clinical implications of these reference values. The establishment of standardized reference values opens new possibilities for enhancing clinical decision making regarding surgical interventions, such as acromioplasty.

Anatomic factors associated with degeneration and fraying of the coracoacromial ligament.

The coracoacromial ligament (CAL) is frequently observed to be damaged during arthroscopy and it is unclear how demographic, anatomic, and radiographic factors are related to CAL degeneration in full-thickness rotator cuff tears. A prospective study was conducted of patients at a single institution undergoing shoulder arthroscopy for first-time, full-thickness rotator cuff tears. We evaluated preoperative anteroposterior radiographs to obtain critical shoulder angle, glenoid inclination, acromial index, acromiohumeral distance, lateral acromial angle, and acromial morphology. We documented CAL quality, rotator cuff tear size and pattern during arthroscopy. Multiple logistic regression was used to identify predictive factors for encountering severe CAL fraying during arthroscopy. Shoulders had mild CAL degeneration in 58.1% of cases, whereas severe CAL degeneration was present in 41.9% of shoulders. Patients with severe CAL attrition were significantly older (62.0 years vs. 58.0 years, P=0.042). Shoulders with severe CAL attrition had large rotator cuff tears in 54.1% of cases (P<0.001), and tears involving the infraspinatus (63.2% vs. 29.6%, P=0.003). The severe degeneration group was more likely to have a larger critical shoulder angle measurement on preoperative radiographs than those in the mild attrition group (36.1°±3.6° [range, 30°-45°] vs. 34.1°±3.8° [range, 26°-45°], P=0.037). While the clinical impact of CAL degeneration remains uncertain, increased severity of CAL degeneration is associated with older age, larger rotator cuff tear size, presence of infraspinatus tearing, and increased preoperative critical shoulder angle. Level of evidence: III.

Investigating the multifactorial etiology of supraspinatus tendon tears.

The purpose of this study was to develop a multivariable model to determine the extent to which a combination of etiological factors is associated with supraspinatus tendon tears. Fifty-four asymptomatic individuals (55 ± 4 years) underwent testing of their dominant shoulder. Diagnostic ultrasound was used to assess for a supraspinatus tendon tear. The etiological factors investigated includeddemographics (age and sex), tendon impingement during shoulder motion (via biplane videoradiography), glenohumeral morphology (via computed tomography imaging), family history of a tear (via self-report), occupational shoulder exposure (via shoulder job exposure matrix), and athletic exposure (via self-report). Univariate relationships between etiological predictors and supraspinatus tears were assessed using logistic regression and odds ratios (ORs), while multivariable relationships were assessed using classification and regression tree analysis. Thirteen participants (24.1%) had evidence of a supraspinatus tear. Individuals with a tear had a higher critical shoulder angle (OR 1.2, p = 0.028) and acromial index (OR 1.2, p = 0.016) than individuals without a tear. The multivariable model suggested that a tear in this cohort can be explained with acceptable accuracy (AUROC = 0.731) by the interaction between acromial index and shoulder occupational exposure: a tear is more likely in individuals with a high acromial index (p < 0.001), and in individuals with a low acromial index and high occupational exposure (p < 0.001). The combination of an individual's glenohumeral morphology (acromial index) and occupational shoulder exposure may be important in the development of supraspinatus tears.

MRI is a Reliable Method for Measurement of Critical Shoulder Angle and Acromial Index.

Objective The objectives of this study are to compare absolute values of acromial index (AI) and critical shoulder angle (CSA) obtained in both radiographs and magnetic resonance image (MRI) of the shoulder; and to compare the interobserver and intra-observer agreement for AI and CSA values measured in these image modalities. Methods Patients who had medical indication of investigating shoulders conditions through radiographs and MRI were included. Images were taken to two fellowship-trained shoulder surgeons, which conducted measurements of AI and CSA in radiographs and in MRI. Twelve weeks after the first evaluation, a second evaluation was conducted. Inter- and intra-observer reliability was presented as an Intraclass Correlation Coefficient (ICC) and agreement was classified according to Landis & Koch criteria. The differences between two measurements were evaluated using Bland-Altman plots. Results 134 shoulders in 124 subjects were included. Mean intra-observer ICC for CSA in X-rays and in MRI were 0.936 and 0.940, respectively; for AI, 0.908 and 0.022. Mean inter-observer ICC for CSA were 0.892 and 0.752 in X-rays and MRI respectively; for AI, ICC values were 0.849 and 0.685. All individual analysis reached statistical power ( p < 0.001). Mean difference for AI values measured in X-rays and in MRI was 0.01 and 0.03 for observers 1 and 2, respectively. Mean difference for CSA values obtained in X-rays and MRI was 0.16 and 0.58 for observers 1 and 2, respectively. Conclusion Both MRI and X-rays provided high intra- and interobserver agreement for measurement of AI and CSA. Absolute values found for AI and CSA were highly correlated in both image modalities. These findings suggest that MRI is a suitable method to measure AI and CSA. Level of Evidence II , Diagnostic Study.

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

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. 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. 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. 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.

Can the role of the acromion index in the diagnosis of rotator cuff tear be redefined with a different measurement technique?

Background: Many radiographic parameters associated with rotator cuff tears (RCT) have been described. Our aim is to measure the capacity to predict RCT by reinterpreting the Acromion index (AI) with a new radiographic measurement technique.&#x0D; Methods: The shoulder magnetic resonance imaging (MRI) report of a total of 62 patients and AI measured with the new technique in shoulder radiographs were evaluated. On shoulder radiographs, the glenohumeral length was identified as the length between the lateral humerus tuberculum majus and the anterior midpoint of the glenoid joint. The glenoacromial length was also defined from a different perspective as the length between the lateral tip of the acromion and the anterior midpoint of the glenoid joint.&#x0D; Results: There was no significant difference in glenohumeral length between patients with complete and partial RCT and those without RCT (p value=0.163). There was no significant difference in glenoacromial length between these three groups of patients (Pvalue=0.110). It was concluded that there was no significant difference between the three groups of patients in terms of AI that we redefined (Pvalue=0.095).&#x0D; Conclusion: AI of the glenohumeral and glenoacromial lengths, which were redefined with a different measurement technique on the shoulder radiography, did not yield statistically significant results in the diagnosis of shoulder RCT.

Does Morphology of the Shoulder Joint Play a Role in the Etiology of Rotator Cuff Tear?

The etiology of rotator cuff tears (RCTs) have been investigated for years and many underlying causes have been identified. Shoulder joint morphology is one of the extrinsic causes of RCTs. Morphometric measurements on MRI sections determined which parameters are an important indicator of RCT in patients with shoulder pain. The aim of this study was to determine the risk factors in the etiology of RCTs by evaluating the shoulder joint morphology with the help of previously defined radiological parameters. Between January 2019-December 2020, 408 patients (40-70 years old) who underwent shoulder MRI and met the criteria were included in the study. There were 202 patients in the RCT group and 206 patients in the control group. Acromion type, acromial index (AI), critical shoulder angle (CSA), acromiohumeral distance (AHD), lateral acromial angle (LAA), acromial angulation (AA), acromion-greater tuberosity impingement index (ATI), and glenoid version angle (GVA) were measured from the MRI images of the patients. AI (0.64 vs. 0.60, p = 0.003) CSA (35.3° vs. 32.4°, p = 0.004), ATI (0.91 vs. 0.83, P < 0.001), and AA (13.6° vs. 11.9°, p = 0.011) values were higher in the RCT group than in the control group and the difference was significant. AHD (8.1 mm vs. 9.9 mm, P < 0.001), LAA (77.2° vs. 80.9°, p = 0.004) and GVA (-3.9° vs. -2.5°, P < 0.001) values were lower in the RCT group than in the control group, and again the difference was significant. According to the receiver operating characteristic curve analysis, the cutoff values were 0.623 for AI and 0.860 for ATI. Acromion type, AI, CSA, AHD, LAA, AA, ATI, and GVA are suitable radiological parameters to evaluate shoulder joint morphology. High AI, CSA, AA, ATI, GVA and low AHD and LAA are risk factors for RCT.

Poster 106: Association Between Glenoacromial Spacing and the Risk for Shoulder Instability

Objectives: Biomechanical studies have shown how the muscular dynamics about the shoulder are affected by the relative glenoid and acromion positions. Some believe these dynamics may play a role in predisposing shoulders to develop either osteoarthritis or rotator cuff disease. It is unclear if these dynamics also place individuals at increased risk for shoulder instability. To address these gaps in the literature, our objectives were to establish normative values for shoulder morphology in young physically active military service members and determine the influence of shoulder morphology, specifically the critical shoulder angle (CSA) and acromial index (AI) on rotator cuff strength and risk of shoulder instability. Methods: A subset of 160 US Service Academy cadets (25 Female, 18.81 ± 0.95 years, 177.01 ± 8.14 cm, and 72.52 ± 12.12 kg) were analyzed from a larger prospective cohort study, including all participants who sustained a shoulder instability injury during the 4-year follow-up period (n=36, all anterior). The remaining participants served as healthy controls. Upon entry to the primary study, baseline bilateral shoulder magnetic resonance imaging (MRI) and rotator cuff strength data were collected. Baseline MRIs were used to assess critical shoulder angle (CSA) defined as the angle formed between the glenoid plane at the inferior most glenoid to the lateral most aspect of the acromion and acromial index (AI) defined as glenoacromial distance (GA) divided by the glenohumeral distance (GH). Additionally, isometric internal rotation (IR) and external rotation (ER) strength was assessed at both 0° and 45° of glenohumeral abduction. Normative values for healthy shoulder morphology were reported by limb dominance. Multivariate linear regression models were used to estimate the association between shoulder morphology and strength. Finally, odds ratios (OR) were calculated using multivariate logistic regression models to estimate the likelihood of shoulder instability based on shoulder morphological outcomes. All multivariable models statistically controlled for the influence of potential confounding variables, including sex, height, weight, and limb dominance. Results: Normative baseline values for CSA, AI, glenohumeral distance and glenoacromial distance were established in young physically active military service members. In multivariate modeling, a positive relationship was detected between GH and ER strength at 45° abduction (Coefficient = 0.35, 95% CI: 0.04, 0.67), and between GA and IR strength at both 0° abduction (Coefficient = 4.29, 95% CI: 0.01, 8.56) and 45° abduction (Coefficient = 4.48, 95% CI: 0.81, 8.14). A positive relationship was detected between shoulder morphology and the likelihood of sustaining a shoulder instability injury (CSA: OR = 1.29, 95% CI: 0.97, 1.72; GA: OR = 14.63, 95% CI: 1.03, 206.98). These results indicate every 1° increase in CSA was associated with being 29% more likely to suffer a shoulder instability injury, while every 1cm increase in GA was associated with being 14 times more likely to suffer a shoulder instability injury. No other significant relationships were detected. Conclusions: Shoulder morphology was observed to play a role in both rotator cuff strength and the likelihood of glenohumeral instability injury. Interestingly, glenoacromial distance, specifically, was associated with both ER and IR strength, and the likelihood of shoulder instability. One theory is the larger the glenoacromial distance, the greater the moment arm for the anterior and posterior deltoid to act on the humerus. This increased mechanical advantage and resultant shear at the glenohumeral joint may be what contributes to the increased risk for instability. Another theory is the laterally placed acromion could be providing a fulcrum for the humerus to dislocate. Shoulder instability is a complex problem with many contributing factors and the glenoacromial scapular morphology may be yet another risk factor contributing to relative rotator cuff weakness and risk of shoulder instability in young active- duty military service members.