Can coracoacromial ligament degeneration be evaluated with preoperative MRI?

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.

Diagnostic Implications of Ultrasound Evaluation in Patients With Shoulder Impingement Syndrome.

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.

Subacromial Motion Metrics in Painful Shoulder Impingement: A Dynamic Quantitative Ultrasonography Analysis.

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 (ß 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 (ß coefficient: 10.516°; 95% CI, 3.103-17.929) and decreased rotation radius (ß 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.

Alteration in coracohumeral ligament and distance in people with symptoms of subcoracoid impingement.

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.

The role of bone morphology of the greater tuberosity and lateral acromion on subacromial space during scaption: a three-dimensional dynamic simulation analysis.

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.

Subacromial impingement syndrome: association of multiple magnetic resonance imaging parameters with shoulder function and pain.

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).

Is it the subcoracoid impingement or the subacromial impingement that tears the subscapularis tendon? A comparison of the MRI findings of the operated and healthy shoulders of the patients.

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.

Identification of Diagnostic Magnetic Resonance Imaging Findings in 47 Shoulders with Subcoracoid Impingement Syndrome by Comparison with 100 Normal Shoulders.

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.

Machine Learning-Based Ultrasomics for Predicting Subacromial Impingement Syndrome Stages.

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.

Supraspinatus tendon thickness and subacromial impingement characteristics in younger and older adults.

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.

Posteroinferior relevant scapular neck offset in reverse shoulder arthroplasty: key player for motion and friction-type impingement in a computer model.

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.

Effects of Ultrasound-Guided Peritendinous and Intrabursal Corticosteroid Injections on Shoulder Tendon Elasticity: A Post Hoc Analysis of a Randomized Controlled Trial.

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.

Acromiohumeral distance and supraspinatus tendon thickness in people with shoulder impingement syndrome compared to asymptomatic age and gender-matched participants: a case control study.

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 (ß = 0.59, 95% CI 0.29, 0.89, p < 0.01, R2 = 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.

Subacromial decompression versus diagnostic arthroscopy for shoulder impingement: a 5-year follow-up of a randomised, placebo surgery controlled clinical trial.

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.

The role of 18F-FDG PET/CT in the diagnosis of frozen shoulder.

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 18F Flour-Deoxy-Glucose (FDG) tracer in the diagnostic process. METHODS: Eleven patients with frozen shoulder and 9 patients with subacromial impingement received a 18F-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: 18F-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.

The acromiohumeral distance in the MRI should not be used as a decision criterion to assess subacromial space width in shoulders with an intact rotator cuff.

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.

Measurement of the coracohumeral distance on magnetic resonance imaging in a large patient cohort.

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.

Comparison of glenohumeral joint rotation between asymptomatic subjects and patients with subacromial impingement syndrome using cine-magnetic resonance imaging: a cross-sectional study.

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.

Subacromial impingement anatomy and its association with rotator cuff pathology in women: radiograph and MRI correlation, a retrospective evaluation.

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.

Radiological and biomechanical assessment of displaced greater tuberosity fractures.

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.