Critical shoulder angle: Measurement reproducibility and correlation with rotator cuff tendon tears

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

OBJECTIVES

Critical 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.

METHODS

CSA 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.

RESULTS

Eighty 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).

CONCLUSION

Higher 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 EVIDENCE

Level III.

Glenoid-based reference system to differentiate shoulder pathologies on plain radiographs

BACKGROUND

Shoulder radiographs are used for evaluation and the planning of treatment of various pathologies. Making a diagnosis of these pathologies on plain radiographs occurs by recognizing the relationship of the humeral head on the registry of the glenoid. Quantification of these changes in registry does not currently exist. We hypothesize that a geometric relationship of the humeral head and the glenoid exists that is defined on an anteroposterior Grashey view radiograph by the relationship of the best-fit circle of the humeral head relative to the best-fit circle of the glenoid such that relative measurements will define the normal shoulder and the pathologic shoulder.

METHODS

One hundred fifty-six shoulders were included: 53 normal shoulders, 51 with primary glenohumeral osteoarthritis (GHOA), and 52 with cuff tear arthropathy (CTA). Humeral head best-fit circle was used to define the circle of the humeral head (cHH). A glenoid best-fit circle (cG) was defined by the following rules: (1) best fit of the glenoid articular surface and (2) was limited by the acromion such that either (a) it reaches maximal interaction with the inferior surface of the acromion or (b) the perimeter of the circle is at the lateralmost point of the acromion. The relationship between cHH and cG is defined by measurement of cHH in horizontal and vertical planes relative to the glenoid circle reference. The horizontal displacement angle (HDA) measures the horizontal position of cHH relative to cG, representing the degree of medialization toward the glenoid. The vertical displacement angle (VDA) measures the vertical position of cHH relative to cG, representing the degree of superiorization toward the acromion. Angles were compared by diagnosis and sex.

RESULTS

The mean HDA was 61.0° (95% confidence interval [CI] 60.3°-61.7°) in normal shoulders, 79.9° (95% CI 76.9°-82.9°) in GHOA, and 63.4° (95% CI 61.7°-65.1°) in CTA (P < .001). The mean VDA was 43.1° (95% CI 42.2°-44.0°) in normal shoulders, 40.9° (95% CI 39.9°-42.0°) in GHOA, and 59.7° (95% CI 57.6°-61.7°) in CTA (P < .001). Interobserver reliability was 0.991 (95% CI 0.94-1.0) and intraobserver reliability was 0.998 (95% CI 0.99-1.0). The geometric relationship of cHH to the glenoid circle reference was plotted for each group.

CONCLUSION

A geometric relationship exists of the humeral head in reference to the glenoid circle. Together, the HDA and the VDA distinguish between a normal shoulder and those with GHOA or CTA. This suggests that this novel methodology may provide a preoperative planning tool that is easily accessible.

Can the presence of SLAP-5 lesions be predicted by using the critical shoulder angle in traumatic anterior shoulder instability?

OBJECTIVE

Although SLAP-5 lesions are associated with recurrent dislocations, their causes and pathomechanisms have not been fully elucidated. This study aimed to investigate the association between SLAP-5 lesions and scapular morphology in traumatic anterior shoulder instability (ASI). We hypothesized that there may be a relationship between SLAP-5 lesions and scapular morphology in traumatic ASI patients.

MATERIALS AND METHODS

The study included 74 patients with isolated Bankart lesions and 69 with SLAP-5 lesions who underwent arthroscopic labral repair for ASI. Critical shoulder angle (CSA) was measured on the roentgenograms, while glenoid inclination (GI) and glenoid version (GV) were measured on magnetic resonance imaging (MRI) by two observers in two separate sessions blinded to each other. Both groups were compared in terms of CSA, GI, and GV.

RESULTS

The mean ages of Bankart and SLAP-5 patients were 28.4±9.1 and 27.9±7.7 (P=0.89), respectively; their mean CSA values were 33.1°±2.6° and 28.2°±2.4°, respectively (P<0.001). The ROC analysis's cut-off value was 30.5°, with 75.0% sensitivity and 76.7% specificity (AUC = 0.830). SLAP-5 lesions were more common on the dominant side than isolated Bankart lesions (P=0.021), but no difference was found between the groups in terms of GI and GV (P=0.334, P=0.081, respectively).

CONCLUSIONS

In ASI, low CSA values appeared to be related to SLAP-5 lesions, and the cut-off value of CSA for SLAP lesion formation was 30.5° with 75.0% sensitivity and 76.7% specificity. Scapula morphology may be related to the SLAP-5 lesions, and CSA can be used as an additional parameter in provocative diagnostic tests and medical imaging techniques for the detection of SLAP lesions accompanying Bankart lesions.

LEVEL OF EVIDENCE

III retrospective case-control study.

Impact of critical shoulder angle in shoulder pathology: a current concepts review

Background

This review aims to describe the origin and development of critical shoulder angle (CSA) and its correlation with different shoulder pathologies. Current literature is inconclusive in characterizing the role of CSA in predicting pathology and surgical outcomes.

Methods

A literature search of both historical and more contemporary research articles on CSA was conducted to compare data points on the impact of CSA on shoulder pathology and postoperative clinical outcomes. This compilation of studies ranges from retrospective reviews to case series as well as cadaveric imaging studies.

Results

The CSA is a reliable radiographic measure in predicting shoulder pathology in correctly oriented radiographs. Surgically modifying the CSA with arthroscopic lateral acromioplasty and results has largely shown improved recovery of strength postoperatively as with no increase in postsurgical complication rates. However, it remains unclear whether surgical alteration of CSA has a role in preventing clinical failure after arthroscopic procedures such as acromioplasty and rotator cuff repair as well as following shoulder arthroplasty.

Discussion

Stronger conclusions regarding the prognostic utility of CSA are limited by the fact that most studies evaluating CSA are smaller retrospective cohorts. Moving forward, randomized controlled trials being conducted may offer greater insight as to how CSA can improve patient-reported outcomes postoperatively.

Critical Shoulder Angle in Patients With Cuff Tears

OBJECTIVE

The pathogenesis of rotator cuff tears (RCTs) is multifactorial. Critical shoulder angle (CSA), which represents the lateral extension of the acromion over the cuff, has been proposed as an extrinsic risk factor. The aim of the present systematic review and meta-analysis was to analyze the available literature regarding the correlation between RCT and CSA.

METHODS

A review was carried out in accordance with the "Preferred Reporting Items for Systematic reviews and Meta-Analyses" guidelines on July 17, 2023, using the following databases: PubMed, Ovid, and Cochrane Reviews. The following keywords were used: "critical shoulder angle," "rotator cuff tears," and "rotator cuff lesions." The methodological quality of the studies was assessed with the MINORS SCORE.

RESULTS

Twenty-eight studies were included. The average CSA among the 2110 patients with full-thickness RCT was 36.7 degrees, whereas the same value among the 2972 controls was 33.1 degrees. The average CSA in the 348 patients with partial-thickness RCT was 34.6 degrees, whereas it was 38.1 degrees in the 132 patients with massive RCT. The average MINORS score was 15.6.

CONCLUSIONS

CSA values were significantly higher in patients with RCT compared with the asymptomatic population. In addition, it appears that CSA values increase with the severity of rotator cuff involvement.

Fully automatic algorithm for detecting and tracking anatomical shoulder landmarks on fluoroscopy images with artificial intelligence

OBJECTIVE

Patients with rotator cuff tears present often with glenohumeral joint instability. Assessing anatomic angles and shoulder kinematics from fluoroscopy requires labelling of specific landmarks in each image. This study aimed to develop an artificial intelligence model for automatic landmark detection from fluoroscopic images for motion tracking of the scapula and humeral head.

MATERIALS AND METHODS

Fluoroscopic images were acquired for both shoulders of 25 participants (N = 12 patients with unilateral rotator cuff tear, 6 men, mean (standard deviation) age: 63.7 ± 9.7 years; 13 asymptomatic subjects, 7 men, 58.2 ± 8.9 years) during a 30° arm abduction and adduction movement in the scapular plane with and without handheld weights of 2 and 4 kg. A 3D full-resolution convolutional neural network (nnU-Net) was trained to automatically locate five landmarks (glenohumeral joint centre, humeral shaft, inferior and superior edges of the glenoid and most lateral point of the acromion) and a calibration sphere.

RESULTS

The nnU-Net was trained with ground-truth data from 6021 fluoroscopic images of 40 shoulders and tested with 1925 fluoroscopic images of 10 shoulders. The automatic landmark detection algorithm achieved an accuracy above inter-rater variability and slightly below intra-rater variability. All landmarks and the calibration sphere were located within 1.5 mm, except the humeral landmark within 9.6 mm, but differences in abduction angles were within 1°.

CONCLUSION

The proposed algorithm detects the desired landmarks on fluoroscopic images with sufficient accuracy and can therefore be applied to automatically assess shoulder motion, scapular rotation or glenohumeral translation in the scapular plane.

CLINICAL RELEVANCE STATEMENT

This nnU-net algorithm facilitates efficient and objective identification and tracking of anatomical landmarks on fluoroscopic images necessary for measuring clinically relevant anatomical configuration (e.g. critical shoulder angle) and enables investigation of dynamic glenohumeral joint stability in pathological shoulders.

KEY POINTS

• Anatomical configuration and glenohumeral joint stability are often a concern after rotator cuff tears. • Artificial intelligence applied to fluoroscopic images helps to identify and track anatomical landmarks during dynamic movements. • The developed automatic landmark detection algorithm optimised the labelling procedures and is suitable for clinical application.

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

BACKGROUND

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.

AIM

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.

METHOD

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.

RESULTS

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.

CONCLUSION

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.

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.

The Correlation between Various Shoulder Anatomical Indices on X-Ray and Subacromial Impingement and Morphology of Rotator Cuff Tears

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.

INFORMATIVE VALUE OF RADIOLOGICAL METHODS FOR DIAGNOSING SUBACROMIAL IMPINGEMENT SYNDROME

Up to 30% of the adult population suffers from impingement syndrome with severe pain. Detection of the disease in the early stages is difficult. Early diagnosis of the initial signs of degenerative changes in the subacromial space saves the patient from surgery and additional risk of postoperative complications. The aim of the study is to evaluate the informative value of radiation methods for diagnosing subacromial impingement syndrome based on the analysis of papers published by domestic and foreign authors, depending on etiopathogenetic factors and anatomical structure of the shoulder joint. Materials and methods. The authors analyzed Russian and foreign publications on anatomical, etiological, pathogenetic, clinical, diagnostic features of subacromial conflict syndrome from databases: e-library (https://www.elibrary.ru), Oxford Medicine Online (https://academic.oup.com /), PubMed (https://pubmed.ncbi.nlm.nih.gov/) and others. The applied research methods were analysis and synthesis, axiomatic method and abstraction. Results. The development of subacromial impingement syndrome was revealed to be due to the structural features of the shoulder joint, which differs from other joints in anatomical and functional complexity. At this, changes in the rotator cuff of the shoulder joint develop under the influence of various etiopathogenetic factors, which can be both external (a decrease in subacromial space, an increase in the volume of the coracoacromial arch, instability, overload of the shoulder joint) and internal (changes in vascularization, pathology of collagen fibers' microstructure, degeneration of the tendons in the rotator cuff, etc.) Currently there is no unified approach to the algorithm of radiation diagnosing the early signs of impingement syndrome and injuries to the rotator cuff of the shoulder joint. Although radiography is a simple and informative method to assess the condition of the shoulder joint, its sensitivity at an early stage of impingement syndrome is insufficient. Magnetic resonance imaging is highly informative and sensitive in the diagnosis of injuries to the rotator cuff of the shoulder joint, however, it has a number of limitations, such as the presence of some contraindications, its high cost, protracted examination time, etc. Ultrasound examination is currently considered the preferred method in the diagnosis of impingement syndrome due to its high informative value, speed of execution and the possibility of its repeatability. Conclusions. The analysis of the informative value of radiation diagnostics methods showed that in identifying the early signs of subacromial impingement syndrome, taking into account etiopathogenetic factors and the anatomical structure of the shoulder joint, the ultrasound method is optimal and preferable; for more complex and controversial cases, according to certain indications, they are the methods of X-ray computer and magnetic resonance imaging. In the absence of the possibility of using high-tech diagnostic methods, classical radiography of the shoulder joint is performed.

Reliability and accuracy of the critical shoulder angle measured by anteroposterior radiographs: using digitally reconstructed radiograph from 3-dimensional computed tomography images

BACKGROUND

Accuracy of current standard radiographic measurement of the critical shoulder angle (CSA) is not well established. This study analyzed the reliability and accuracy of the CSA measurements obtained via anteroposterior (AP) radiographs, using a digitally reconstructed radiograph (true AP view) generated from a computed tomography image as the gold standard.

METHODS

The CSA was measured on the radiographs and true AP views of 88 consecutive patients who had undergone shoulder arthroscopy for rotator cuff tears. Intraobserver and interobserver reliabilities of the CSA, measured by 2 orthopedic surgeons, were evaluated, and the average deviation of the CSA between radiographs and true AP views was calculated. Moreover, we compared the deviation of CSA between standard AP films (types A1 and C1) and nonstandard AP films (other types) against the Suter-Henninger criteria.

RESULTS

Intraobserver and interobserver reliabilities were almost perfect on radiographs (0.96, 0.86) and true AP views (0.93, 0.85). The average deviation of CSA was 2.1° ± 1.6° for observer 1 and 2.2° ± 1.9° for observer 2. The percentage of cases with deviations of 2° or more when compared with the true AP view was 42% (37 of 88) for observer 1 and 53% (47 of 88) for observer 2. Only 22% (19 of 88) of films were standard AP films. The average deviation of CSA was not significantly different between standard and nonstandard AP films for observer 1 (standard 1.9° ± 1.3°; nonstandard 2.1° ± 1.7°; P = .76) and observer 2 (standard 1.6° ± 1.5°; nonstandard 2.4° ± 1.9°; P = .09).

CONCLUSION

The CSA measurements using radiography were highly congruent, but a large measurement deviation occurred between radiographs and true AP views. The clinical usefulness and role of CSA in diagnosis require careful consideration.

Acute, Traumatic Rotator Cuff Tears Have Smaller Critical Shoulder Angles Than Degenerative Tears

PURPOSE

To determine whether the critical shoulder angle (CSA) in acute, traumatic rotator cuff tears (RCTs) is consistent with the previously described CSA in chronic degenerative RCTs.

METHODS

We performed a multicenter retrospective analysis of 134 patients presenting to 5 surgeons fellowship trained in shoulder and elbow or sports. Preoperative imaging was used to measure the CSA and tear characteristics. Patients were included if they had acute, traumatic full-thickness RCTs documented on advanced imaging and had preoperative Grashey radiographs. Patients were excluded if they had any history of shoulder pain, injury, surgery, or treatment prior to the current episode; were overhead athletes; or had fatty infiltration greater than Goutallier grade 1 on imaging.

RESULTS

The mean CSA was 33.5° (standard deviation, 4.1°), and 60% of tears had a CSA of less than 35°, much below the mean of 38.0° and the threshold of greater than 35° in degenerative RCTs. The mean age was 58 years, and 70% of patients were men. Overall, 60% of tears involved the subscapularis, 49% of tears occurred in patients aged 60 years or older, and 18% of patients sustained a dislocation. Older age (β = 0.316, P = .003) and male sex (β = 5.532, P = .025) were predictive of tear size, and older age (β = 0.229, P = .011) and biceps avulsion (β = 8.822, P = .012) were predictive of tear retraction.

CONCLUSIONS

Acute, traumatic RCTs have CSAs that are 5° smaller than those of degenerative tears, and the majority (60%) have CSAs that are below the threshold consistent with degenerative RCTs. The majority of traumatic tears (60%) involve the subscapularis.

CLINICAL RELEVANCE

The study findings suggest that a traumatic tear is not simply the acute failure of a degenerative tendon and that it represents a distinct pathologic entity. These findings support current practice of treating traumatic RCTs differently than degenerative RCTs.

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).

How much acromial bone should be removed to decrease the critical shoulder angle? A 3D CT acromioplasty planning study

BACKGROUND

A high critical shoulder angle (CSA) is associated with rotator cuff tear (RCT) and retear rate after repair. CSA reduced to less than 33° by acromioplasty is correlated with better clinical results and healing. But up to 24% of patients retain a CSA above 35° after acromioplasty. The objective of the study was to evaluate the use of 3D when planning acromioplasty and measure acromial bone removal volume dimensions.

METHODS

Computed tomography (CT) scans from 45 patients with RCT and CSA ≥ 38° were retrospectively included. A 33° CSA cutting plane was positioned. Acromion was divided into 5 mm slices and acromial bone resection measured on each slice.

RESULTS

Intra- and inter-observer reproducibility measurements were rated strong or very strong. Patients' mean preoperative CSA was 40° (38°, 49° ± 2.3°). Measurements of acromial resection were: anteroposterior length: 32.7 mm (20, 50 ± 7.4); inferior width: 7.6 mm (4.2, 19 ± 2.9); superior width: 4.1 mm (0, 16 ± 3.0); height: 6.1 mm (1.7, 6.7 ± 1.6); and cutting angle: 74° (46, 91 ± 8.0). Maximum width of acromial resection was located 10.6 mm (5, 17.5 ± 0.6) from the acromion's anterior edge and decreased gradually moving posteriorly. Preoperative CSA was linearly correlated with width (P < 0.0001, R = 84%) and length (P = 0.0001, R = 28%) of acromioplasty; the higher the CSA, the greater the width and length.

CONCLUSIONS

3D CT reconstructions are valid for planning a CSA decreasing acromioplasty. To reduce CSA to 33°, acromioplasty must be performed anterolaterally and resection is at least 2 cm long anteroposteriorly. For higher CSAs, acromioplasty may require lateral resection over 1 cm in width and up to 5 cm in length. To decrease the CSA efficiently, acromioplasty must be adapted to patient anatomy and 3D planning could be considered.

LEVEL OF EVIDENCE

IV.

A predictive model for the critical shoulder angle based on a three-dimensional analysis of scapular angular and linear morphometrics

BACKGROUND

The purpose of this study was to define the features of scapular morphology that are associated with changes in the critical shoulder angle (CSA) by developing the best predictive model for the CSA based on multiple potential explanatory variables, using a completely 3D assessment.

METHODS

3D meshes were created from CT DICOMs using InVesalius (Vers 3.1.1, RTI [Renato Archer Information Technology Centre], Brazil) and Meshmixer (3.4.35, Autodesk Inc., San Rafael, CA). The analysis included 17 potential angular, weighted linear and area measurements. The correlation of the explanatory variables with the CSA was investigated with the Pearson's correlation coefficient. Using multivariable linear regression, the approach for predictive model-building was leave-one-out cross-validation and best subset selection.

RESULTS

Fifty-three meshes were analysed. Glenoid inclination (GI) and coronal plane angulation of the acromion (CPAA) [Pearson's r: 0.535; -0.502] correlated best with CSA. The best model (adjusted R-squared value 0.67) for CSA prediction contained 10 explanatory variables including glenoid, scapular spine and acromial factors. CPAA and GI were the most important based on their distribution, estimate of coefficients and loss in predictive power if removed.

CONCLUSIONS

The relationship between scapular morphology and CSA is more complex than the concept of it being dictated solely by GI and acromial horizontal offset and includes glenoid, scapular spine and acromial factors of which CPAA and GI are most important. A further investigation in a closely defined cohort with rotator cuff tears is required before drawing any clinical conclusions about the role of surgical modification of scapular morphology.

LEVEL OF EVIDENCE

Level 4 retrospective observational cohort study with no comparison group.

Deep learning model for measurement of shoulder critical angle and acromion index on shoulder radiographs

Background

Several bone morphological parameters, including the anterior acromion morphology, the lateral acromial angle, the coracohumeral interval, the glenoid inclination, the acromion index (AI), and the shoulder critical angle (CSA), have been proposed to impact the development of rotator cuff tears and glenohumeral osteoarthritis. This study aimed to develop a deep learning tool to automate the measurement of CSA and AI on anteroposterior shoulder radiographs.

Methods

We used MURA Dataset v1.1, which is a large publicly available musculoskeletal radiograph dataset from the Stanford University School of Medicine. All normal shoulder anteroposterior radiographs were extracted and annotated by an experienced orthopedic surgeon. The annotated images were divided into train (1004), validation (174), and test (93) sets. We use pytorch_segmentation_models for U-Net implementation and PyTorch framework for training the model. The test set was used for final evaluation of the model.

Results

The mean absolute error for CSA and AI between human-performed and machine-performed measurements on the test set with 93 images was 1.68° (95% CI 1.406°-1.979°) and 0.03 (95% CI 0.02 - 0.03), respectively.

Conclusions

A deep learning model can precisely and accurately measure CSA and AI in shoulder anteroposterior radiographs. A tool of this nature makes large-scale research projects feasible and holds promise as a clinical application if integrated with a radiology software program.

Optimization of the Grashey View Radiograph for Critical Shoulder Angle Measurement: A Reliability Assessment With Zero Echo Time MRI

Background:

Suboptimal positioning on Grashey view radiographs may limit the prognosticating potential of the critical shoulder angle (CSA) for shoulder disorders.

Purpose:

To investigate whether radiography optimized according to the latest research is reliable for measuring CSA in comparison with magnetic resonance imaging (MRI) featuring 3-dimensional (3D) zero echo time (ZTE) sequencing, which accentuates the contrast between cortical bone and surrounding soft tissue with high fidelity.

Study Design:

Cohort study (diagnosis); Level of evidence, 2.

Methods:

Patients with shoulder pain were prospectively and consecutively enrolled. All patients had Grashey view radiographs as well as 3.0-T MRI scans with isotropic 3D ZTE sequencing. Acceptable positioning on the radiographs was determined using the ratio of the transverse to longitudinal (RTL) diameter of the lateral glenoid outline; radiographs with an RTL ≥0.25 were repeated. Two observers independently measured the CSA on the radiographs and the coronal oblique reformatted ZTE images, the latter including verification of measurement points by cross-referencing against images from other planes. Reliability of measurements between observers and modalities was analyzed with the intraclass correlation coefficient (ICC). The paired-samples t test was used to compare the differences between imaging modalities.

Results:

Enrolled were 65 patients (35 female and 30 male; mean age, 40.2 years; range, 25-49 years). Radiographs with optimal positioning (RTL < 0.25) were attained after a mean of 1.6 exposures (range, 1-4); the mean RTL was 0.09 (range, 0-0.20). Interobserver agreement of CSA was excellent for radiographs (ICC = 0.91; 95% CI, 0.84-0.94) and good for ZTE MRI scans (ICC = 0.85; 95% CI, 0.71-0.92). Intermodality agreement of CSA between radiographs and ZTE MRI scans was moderate (ICC = 0.66; 95% CI, 0.48-0.73). The CSA was significantly different between an optimal radiograph (30.7° ± 4.3°) and ZTE MRI scan (31.8° ± 3.8) (P = .005). Subgroup analysis revealed no significant differences in CSA measurement between ZTE MRI scans and Grashey view radiographs with an RTL of <0.1 (P = .08).

Conclusion:

CSA measurement on ZTE MRI scans with anatomic point cross-referencing was significantly different from that on Grashey view radiographs, even with optimal positioning, and radiography may necessitate more than 1 exposure. An RTL of <0.1 ensured reliability of radiographs when other standards of sufficient x-ray exposure were met.

Controversy on the Association of the Critical Shoulder Angle and the Development of Degenerative Rotator Cuff Tears: Is There a True Association? A Meta-analytical Approach

BACKGROUND

The role of the critical shoulder angle (CSA) as a risk factor for rotator cuff tear (RCT) remains controversial. Studies on the association between the CSA and RCT show considerable differences in design, and this could be responsible for the variation in study results.

PURPOSE

To (1) describe the reliability of CSA measurement and (2) evaluate the results of the studies reporting the association between the CSA and RCT using meta-analytical techniques to explore potential sources of variation of study results.

STUDY DESIGN

Systematic review and meta-analysis; Level of evidence, 4.

METHODS

MEDLINE, EMBASE, and CINAHL electronic databases were searched through June 30, 2019. Case-control and cross-sectional studies reporting the association of the CSA and RCT were selected. The weighted mean difference in the CSA was estimated using a random-effects model. Prediction interval was computed to better express uncertainties in the effect estimate. Metaregression and subgroup analyses were performed to explore potential sources of heterogeneity.

RESULTS

A total of 14 studies, including 1154 cases and 1271 controls, were identified. Of these studies, 79% (11/14) assessed the reliability of the CSA measurement, demonstrating an excellent intraobserver (range, 0.91-0.99) and interobserver (range, 0.87-0.99) reliability. Compared with controls, cases with RCT showed larger measurements of the CSA (3.3° [95% CI, 2.3°- 4.4°]). However, there was a high heterogeneity (I² = 93%), and the 95% prediction interval (-0.4° to 7.1°) included no difference in the CSA. Results of the metaregression analysis showed a significant association of several methodological aspects with the heterogeneity. The difference in the CSA tended to be larger when only full-thickness tears were included, when no specific defined criterion for assessing radiographic viewing perspective was used, in studies with smaller sample sizes, and in studies at higher risk of bias.

CONCLUSION

While the CSA can be reliably measured, the difference in the CSA between cases and controls varied from very large to modest or almost no difference. Several determinants of heterogeneity were determined. Owing to this heterogeneity, it is difficult to gain an insight into the strength and exact nature of the association between the CSA and RCT with the current evidence.

Critical shoulder angle and failure of conservative treatment in patients with atraumatic full thickness rotator cuff tears

Background

Atraumatic full thickness rotator cuff tears (AFTRCT) are common lesions whose incidence increases with age. Physical therapy is an effective conservative treatment in these patients with a reported success rate near 85% within 12 weeks of treatment. The critical shoulder angle (CSA) is a radiographic metric that relates the glenoid inclination with the lateral extension of the acromion in the coronal plane. A larger CSA has been associated with higher incidence of AFTRCT and a higher re-tear rate after surgical treatment. However, no study has yet described an association between a larger CSA and failure of conservatory treatment in ARCT. The main objective of this study is to determine whether there is an association between CSA and failure of physical therapy in patients with AFTRCT.

Methods

We reviewed the imaging and clinical records of 48 patients (53 shoulders), 60% female, with a mean age of 63.2 years (95% CI ± 10.4 years); treated for AFTRCT who also underwent a true anteroposterior radiograph of the shoulder within a year of diagnosis of the tear. We recorded demographic (age, sex, type of work), clinical (comorbidities), and imaging data (CSA, size and location of the tear). We divided the patients into two groups according to success or failure of conservative treatment (indication for surgery), so 21 shoulders (39.6%) required surgery and were classified as failure of conservative treatment.

Univariate and multivariate analysis was performed to detect predictors of failure of conservative treatment.

Results

The median CSA was 35.5º with no differences between those with failure (median 35.5º, range 29º to 48.2º) and success of conservative treatment (median 35.45º, range 30.2º to 40.3º), p = 0.978.

The multivariate analysis showed a younger age in patients with failure of conservative treatment (56.14 ± 9.2 vs 67.8 ± 8.4, p < 0.001) and that male gender was also associated with failure of conservative treatment (57% of men required surgery vs 28% of women, p = 0.035).

Conclusions

It is still unclear if CSA does predict failure of conservative treatment. A lower age and male gender both could predicted failure of conservative treatment in AFTRCT. Further research is needed to better address this subject.

Reliability of the Fluoroscopic Assessment of Load-Induced Glenohumeral Translation during a 30° Shoulder Abduction Test

Rotator cuff tears are often linked to superior translational instability, but a thorough understanding of glenohumeral motion is lacking. This study aimed to assess the reliability of fluoroscopically measured glenohumeral translation during a shoulder abduction test. Ten patients with rotator cuff tears participated in this study. Fluoroscopic images were acquired during 30° abduction and adduction in the scapular plane with and without handheld weights of 2 kg and 4 kg. Images were labelled by two raters, and inferior–superior glenohumeral translation was calculated. During abduction, glenohumeral translation (mean (standard deviation)) ranged from 3.3 (2.2) mm for 0 kg to 4.1 (1.8) mm for 4 kg, and from 2.3 (1.5) mm for 0 kg to 3.8 (2.2) mm for 4 kg for the asymptomatic and symptomatic sides, respectively. For the translation range, moderate to good interrater (intra-class correlation coefficient ICC [95% confidence interval (CI)]; abduction: 0.803 [0.691; 0.877]; adduction: 0.705 [0.551; 0.813]) and intrarater reliabilities (ICC [95% CI]; abduction: 0.817 [0.712; 0.887]; adduction: 0.688 [0.529; 0.801]) were found. Differences in the translation range between the repeated measurements were not statistically significant (mean difference, interrater: abduction, −0.1 mm, p = 0.686; adduction, −0.1 mm, p = 0.466; intrarater: abduction 0.0 mm, p = 0.888; adduction, 0.2 mm, p = 0.275). This method is suitable for measuring inferior–superior glenohumeral translation in the scapular plane.

A prospective observational case control study investigating the coronal plane scapular morphological differences in full-thickness posterosuperior cuff tears and primary glenohumeral osteoarthritis

INTRODUCTION

The critical shoulder angle (CSA) is a surrogate marker of the coronal plane morphology of the scapula. CSA differences between scapulae could be due to differences in glenoid inclination (GI) or the location of the most lateral part of the acromion relative to the inferior glenoid, or both. An understanding of the hierarchy of the scapular morphological changes associated with glenohumeral osteoarthritis (GHOA) and rotator cuff (RC) tears would allow accurate biomechanical modeling.

METHODS

A prospective observational case control study was undertaken in which the GI, "nonglenoid"-CSA, acromial vertical offset index, acromial horizontal offset index, acromial horizontal-vertical offset index, and coronal plane angulation of the acromion (CPAA-m) were measured on high-quality radiographs to compare coronal plane scapular anatomy in: (1) patients with asymptomatic atraumatic full-thickness RC tears, (2) patients with symptomatic primary GHOA, and (3) a control group with no RC tear or GHOA treated for glenohumeral instability or symptomatic labral pathology. Intraobserver reliability of the measurements was performed.

RESULTS

In the GHOA group, the GI was lower (less superiorly inclined) than the RC tear group (difference between the means: -4.8°, 95% confidence interval [CI] [-8.8°, -0.9°], P = .014) and the control group (difference between the means: -7.9°, 95% CI [-11.8°, -3.9°], P = .000); there was no difference in the acromial measurements. In the RC tear group, the nonglenoid-CSA was higher (difference between the means: 7.7°, 95% CI [3.0°, 12.3°], P = .001), the acromial vertical offset index was lower (difference between the means: -0.13, 95% CI [-0.24, -0.01], P = .026), and the acromial horizontal-vertical offset index was higher (difference between the means: 0.15, 95% CI [0.01, 0.28], P = .030) than the control group; there was no difference in the acromial horizontal offset index or the GI. The CPAA-m was lower (greater coronal plane downslope of the acromion) in both GHOA (difference between the means: -9.6°, 95% CI [-18.6°, -0.5°], P = .036) and RC tears (difference between the means: -9.9°, 95% CI [-19.0°, -0.9°], P = .029) compared with the control group. The intraclass correlation coefficients for intraobserver reliability demonstrated excellent reliability for the measurements (all >0.900).

DISCUSSION

Scapulae associated with GHOA have lower GI, but no spatial differences in the location of the lateral acromion compared with a normal population. Scapulae associated with RC tears have a lower vertical offset of the lateral acromion, but no difference in horizontal offset or GI compared with a normal population. The downslope of the acromion in the coronal plane is greater (lower CPAA-m) in both RC tears and GHOA than the normal population.

In Vitro Simulation of Shoulder Motion Driven by Three-Dimensional Scapular and Humeral Kinematics

In vitro simulation of three-dimensional (3D) shoulder motion using in vivo kinematics obtained from human subjects allows investigation of clinical conditions in the context of physiologically relevant biomechanics. Herein, we present a framework for laboratory simulation of subject-specific kinematics that combines individual 3D scapular and humeral control in cadavers. The objectives were to: (1) robotically simulate seven healthy subject-specific 3D scapulothoracic and glenohumeral kinematic trajectories in six cadavers, (2) characterize system performance using kinematic orientation accuracy and repeatability, and muscle force repeatability metrics, and (3) analyze effects of input kinematics and cadaver specimen variability. Using an industrial robot to orient the scapula range of motion (ROM), errors with repeatability of ±0.1 mm and <0.5 deg were achieved. Using a custom robot and a trajectory prediction algorithm to orient the humerus relative to the scapula, orientation accuracy for glenohumeral elevation, plane of elevation, and axial rotation of <3 deg mean absolute error (MAE) was achieved. Kinematic accuracy was not affected by varying input kinematics or cadaver specimens. Muscle forces over five repeated setups showed variability typically <33% relative to the overall simulations. Varying cadaver specimens and subject-specific human motions showed effects on muscle forces, illustrating that the system was capable of differentiating changes in forces due to input conditions. The anterior and middle deltoid, specifically, showed notable variations in patterns across the ROM that were affected by subject-specific motion. This machine provides a platform for future laboratory studies to investigate shoulder biomechanics and consider the impacts of variable input kinematics from populations of interest, as they can significantly impact study outputs and resultant conclusions.

Does isolated arthroscopic anterior acromioplasty modify critical shoulder angle?

INTRODUCTION

Critical shoulder angle (CSA)>35° correlates significantly with primary rotator cuff tear and re-tear after repair. Acromial axial orientation varies between individuals. The present study aimed to assess the impact of strictly anterior acromioplasty on CSA.

HYPOTHESIS

CSA is reduced by arthroscopic anterior acromioplasty.

MATERIAL AND METHODS

A single-center retrospective study included patients receiving isolated arthroscopic acromioplasty between January 2016 and December 2017. Exclusion criteria comprised history of surgery and fracture or dislocation of the shoulder. Pre- and post-operative AP shoulder radiographs were taken. The angle subtended by a line between the inferior and superior edges of the glenoid and a line between the inferior edge of the glenoid and the most lateral point on the acromion was measured.

RESULTS

One hundred and two patients were included: mean age, 50.5±10.1 years (range, 23-82 years). Mean CSA was 34.7±4.4° (range, 26-48°) preoperatively and 31.7±3.7° (range, 23-40°) postoperatively (p<0.001). In the group with CSA >35°, the decrease was significant: 34.4±3.2° (range, 28-40°) versus 38.9±2.8° (range, 36-48°) (p<0.001), with 64% CSA <35° after isolated anterior acromioplasty.

DISCUSSION

CSA was decreased by arthroscopic acromioplasty. However, in 36% of cases with preoperative CSA >35°, CSA was not normalized.

CONCLUSION

Anterior arthroscopic acromioplasty significantly reduced CSA in the overall population, and especially in case of high CSA.

LEVEL OF EVIDENCE

IV; retrospective study.

Are critical shoulder angle and acromion index correlated to the size of a rotator cuff tear

PURPOSE

Scapular morphology is an extrinsic factor playing role in rotator cuff tear (RCT) etiology. The objective of this study was to evaluate the relationship between critical shoulder angle (CSA) and acromion index (AI) with partial-bursal side and full thickness RCT and the size of the RCT.

HYPOTHESIS

The hypothesis was that CSA and AI would be greater in partial bursal-side RCT and full-thickness RCT patients and would increase with the size of the RCT.

METHODS

This retrospective study assessed 218 patients who had standard shoulder radiographs and magnetic resonance imaging. Patients were divided into three groups: intact rotator cuff (68), partial bursal-side RCT (34) and full-thickness RCT (116). In the second part, full-thickness RCT patients were divided into four groups according to RCT size; small (<1cm), medium (1-3cm), large (3-5cm) and massive (>5cm). AI and CSA measurements were evaluated from radiographs.

RESULTS

The mean CSA was 32.8̊ in control group, 34.3̊ in partial group and 36.9̊ in full-thickness group. The mean AI was 0.66, 0.68 and 0.72 respectively. Significant difference was found in AI and CSA between full thickness RCT and intact RC group (p<0.01), and partial RCT and full thickness RCT group (p<0.05) in paired comparisons. In full thickness RCT size groups the mean CSA was 34.2̊, 36.4̊, 39.0̊ and 40.8̊ and mean AI was 0.70, 0.71, 0.73 and 0.79 respectively. Significant difference was found between small-large, small-massive, medium-massive groups for CSA in paired comparisons and between small-massive, medium-massive groups for AI.

CONCLUSION

CSA and AI were significantly greater in full-thickness RCT patients and the size of the RCT increased with CSA and AI. The greater CSA and AI could be predictors for larger RCT.

LEVEL OF EVIDENCE

III; Cross-Sectional Design; Prognosis Study.

Could radio-morphological changes in humerus greater tuberosity be an early indicator of rotator cuff tendon injuries?

OBJECTIVES

To reveal the possible relationship between greater tuberosity volume with rotator cuff tendon injuries.

MATERIALS AND METHODS

In our study, the morphology of the greater tuberosity was evaluated retrospectively by using radiographs and MR images of 335 cases. While critical shoulder angle (CSA) was measured on radiographs, greater tuberosity (GT) area and volume were calculated, and also supraspinatus, infraspinatus, and teres minor tendons were evaluated, on MR images. The relationship of the measurements with the tendon injuries was analyzed statistically.

RESULTS

Among 188 female and 147 male patients, no statistically significant relationship was found between tendon injuries in terms of gender. The relationships between supra and infraspinatus tendon injuries and GT angle, area, and volume measurements were statistically significant. There was a statistically significant relationship between teres minor injury and GT angle, but no significant correlation with GT area and volume. Finally, there was no statistically significant correlation between all three tendon pathologies and CSA.

CONCLUSION

Area, and especially volume measurements, which are morphological features of the GT, may reflect tendon damage without significant degenerative changes in the bone structure. In examinations before tendon damage progresses, GT volume is a morphological feature that needs to be evaluated and may facilitate early recognition of tendinopathies and be an early marker of rotator cuff injuries.

High Critical Shoulder Angle Values Are Associated With Full-Thickness Posterosuperior Cuff Tears and Low Values With Primary Glenohumeral Osteoarthritis

PURPOSE

To compare critical shoulder angle (CSA) measurements using high-quality radiographs in the following groups: Group 1: symptomatic atraumatic full-thickness rotator cuff (RC) tears; Group 2: symptomatic primary glenohumeral osteoarthritis (GHOA); and Group 3: no RC tear or primary GHOA being treated for glenohumeral instability or symptomatic labral pathology (control group).

METHODS

A prospective observational case control study with 10 shoulders in each group was performed GHOA and full-thickness RC tears were diagnosed by radiographs and magnetic resonance imaging (MRI). For these three groups, the exclusion criteria were the following: Group 1) partial thickness RC tears, traumatic RC tears, isolated subscapularis tears, and advanced cuff tear arthropathy with erosion of the superior glenoid; Group 2) secondary causes of glenohumeral arthritis; coexistent full-thickness RC tear; and Group 3) glenoid bone lesions that may affect the CSA measurement. Only shoulders with adequate radiographic quality (Suter-Henninger type A and C) were eligible. A one-way ANOVA, followed by Tukey multiple pairwise-comparisons test, was performed to compare the groups. Interobserver and intraobserver reliability was assessed using Intraclass Correlation Coefficients (ICC).

RESULTS

Mean CSA values were 37.4° ± 4.7 (RC tear group), 28.9° ± 2.4 (GHOA group), and 32.8° ± 1.1 (control group). The CSA of the RC group was higher than the control group (P = .006) and the GHOA group (P = .000). The CSA of the GHOA group was lower than the control group (P = .027). Intraobserver and interobserver reliabilities for the CSA measurement were excellent (Observer 1 [ICC]: .986 [95% CI .970-.993]; Observer 2 [ICC]: .976[95% CI .951-.989]; and Observer 1v2: 0.968[95% CI .933-.985]).

CONCLUSIONS

There is a difference in the CSA between patients with symptomatic atraumatic full-thickness RC tears (4.6° higher than the control group), symptomatic GHOA (3.8° lower than the control group), and glenohumeral instability or labral pathology with no RC tear or GHOA.

LEVEL OF EVIDENCE

Level 2, prospective observational case control diagnostic study.

Anatomically Parameterized Statistical Shape Model: Explaining Morphometry through Statistical Learning

Objective: Statistical shape models (SSMs) are a popular tool to conduct morphological analysis of anatomical structures which is a crucial step in clinical practices. However, shape representations through SSMs are based on shape coefficients and lack an explicit one-to-one relationship with anatomical measures of clinical relevance. While a shape coefficient embeds a combination of anatomical measures, a formalized approach to find the relationship between them remains elusive in the literature. This limits the use of SSMs to subjective evaluations in clinical practices. We propose a novel SSM controlled by anatomical parameters derived from morphometric analysis. Methods: The proposed anatomically parameterized SSM (ANAT_SSM) is based on learning a linear mapping between shape coefficients (latent space) and selected anatomical parameters (anatomical space). This mapping is learned from a synthetic population generated by the standard SSM. Determining the pseudo-inverse of the mapping allows us to build the ANAT_SSM. We further impose orthogonality constraints to the anatomical parameterization (OC-ANAT_SSM) to obtain independent shape variation patterns. The proposed contribution was evaluated on two skeletal databases of femoral and scapular bone shapes using clinically relevant anatomical parameters within each (five for femoral and six for scapular bone). Results: Anatomical measures of the synthetically generated shapes exhibited realistic statistics. The learned matrices corroborated well with the obtained statistical relationship, while the two SSMs achieved moderate to excellent performance in predicting anatomical parameters on unseen shapes. Conclusion: This study demonstrates the use of anatomical representation for creating anatomically parameterized SSMs and as a result, removes the limited clinical interpretability of standard SSMs. Significance: The proposed models could help analyze differences in relevant bone morphometry between populations, and be integrated in patient-specific pre-surgery planning or in-surgery assessment.

Critical shoulder angle (CSA): age and gender distribution in the general population

Objective

Anatomical parameters and pathologies that can affect the critical shoulder angle (CSA) are subjects of discussion. To date, we do not know if the CSA value changes in the different decades of life in a population characterized by the same ethnicity, nor if there are differences related to gender or side. This study hypothesizes that age and gender may affect the CSA.

Methods

Patients older than 15 years old affected by a shoulder trauma and who were discharged with a diagnosis of shoulder contusion were enrolled. A true AP view of the shoulder was obtained as well as data regarding age and gender of all participants. The CSA was measured by three authors, and interoperator reliability was assessed. Eight subcategories, according to decades of life, were considered. Finally, the studied population was divided into three subcategories according to CSA values (< 30°; 30–35°; ≥ 35°).

Results

The initial sample comprised 3587 shoulder X-rays. The interobserver reproducibility was high, with an intraclass correlation coefficient of 0.865 (95% CI 0.793–0.915).

Two thousand eight hundred seventy-three radiograms were excluded. The studied group comprised 714 patients [431 females, 283 males; mean age (SD): 47.2 (20.9) years, range: 11–93 years]. The mean CSA was 33.6° (range: 24–50°; SD: 3.9°). The mean CSA values in females and males were 33.7°and 33.5°, respectively. The mean CSA values of the right and left shoulders were 33.3° and 33.9°, respectively (p > 0.05). Linear regression analysis showed a CSA increase by 0.04° every year. The mean CSA in subjects aged between 15 and 19 years was significantly lower than all the other groups, except for patients older than 80 years.

No significant differences were found between CSA subcategories, gender, or side.

Conclusions

In the general population, the mean CSA value was 33.6°. No significant differences were found regarding the mean CSA value according to gender or side. A significant positive linear correlation between CSA and age was detected. In each decade of life, the CSA value, which is genetically determined, shows a large variability.

Level of evidence: IV.

Evaluation of MR-derived simulated CT-like images and simulated radiographs compared to conventional radiography in patients with shoulder pain: a proof-of-concept study

Background

To evaluate the diagnostic value of MR-derived CT-like images and simulated radiographs compared with conventional radiographs in patients with suspected shoulder pathology.

Methods

3 T MRI of the shoulder including a 3D T1-weighted gradient echo sequence was performed in 25 patients (mean age 52.4 ± 18 years, 13 women) with suspected shoulder pathology. Subsequently a cone-beam forward projection algorithm was used to obtain intensity-inverted CT-like images and simulated radiographs. Two radiologists evaluated the simulated images separately and independently using the conventional radiographs as the standard of reference, including measurements of the image quality, acromiohumeral distance, critical shoulder angle, degenerative joint changes and the acromial type. Additionally, the CT-like MR images were evaluated for glenoid defects, subcortical cysts and calcifications. Agreement between the MR-derived simulated radiographs and conventional radiographs was calculated using Cohen’s Kappa.

Results

Measurements on simulated radiographs and conventional radiographs overall showed a substantial to almost perfect inter- and intra-rater agreement (κ = 0.69–1.00 and κ = 0.65–0.85, respectively). Image quality of the simulated radiographs was rated good to excellent (1.6 ± 0.7 and 1.8 ± 0.6, respectively) by the radiologists. A substantial agreement was found regarding diagnostically relevant features, assessed on Y- and anteroposterior projections (κ = 0.84 and κ = 0.69 for the measurement of the CSA; κ = 0.95 and κ = 0.60 for the measurement of the AHD; κ = 0.77 and κ = 0.77 for grading of the Samilson-Prieto classification; κ = 0.83 and κ = 0.67 for the grading of the Bigliani classification, respectively).

Conclusion

In this proof-of-concept study, clinically relevant features of the shoulder joint were assessed reliably using MR-derived CT-like images and simulated radiographs with an image quality equivalent to conventional radiographs. MR-derived CT-like images and simulated radiographs may provide useful diagnostic information while reducing the amount of radiation exposure.

Are any radiologic parameters independently associated with degenerative postero-superior rotator cuff tears?

BACKGROUND

Several radiologic parameters representing scapular morphology have been proposed as risk factors for degenerative posterosuperior rotator cuff tear (PSRCT). The causes of PSRCT are multifactorial; many reported risk factors are compound entities. However, no determination, made after adjustment with previously reported risk factors, of which radiologic parameters are independent risk factors for degenerative PSRCT, has been reported. Therefore, this study's purpose was to determine which radiologic parameters representing scapular morphology are independent risk factors for degenerative PSRCT in a general population after adjustment with previously suggested risk factors.

METHODS

This study involved 629 subjects (629 shoulders) drawn from a cohort of rural residents. PSRCT diagnoses were based on magnetic resonance imaging findings. Logistic regression analysis was used to determine the odds ratios and 95% confidence intervals for the following variables: sex, age, height, weight, waist circumference, dominant-side involvement, smoking, alcohol consumption, manual labor, diabetes, hypertension, metabolic syndrome, thyroid dysfunction, serum lipid profile, high-sensitivity C-reactive protein, and radiologic parameters. The evaluated radiologic parameters were the superior displacement of the humeral head (SDHH) and those representing the scapular morphology. The radiologic parameters representing the scapular morphology were lateral acromial angle, acromial slope, acromial tilt, acromial index, and critical shoulder angle (CSA). Univariate logistic regression analyses for all variables, as well as multivariable logistic regression analyses for variables with significant associations and clinical effect sizes in the univariate logistic regression analyses, were performed. In order to determine the cutoff value for significant radiologic parameters, each pair of candidate cutoff values was obtained as follows: 1 candidate, as the lowest significant ordinal value in a univariate analysis, and the other candidate, according to a receiver operating characteristic curve analysis. Then, the cutoff values were determined by selecting the value in each candidate pair that had the larger area under the receiver operating characteristic curve, using the DeLong test.

RESULTS

In the multivariable analyses, CSA was significantly associated with degenerative PSRCT after controlling for the following factors: age, waist circumference, dominant-side involvement, manual labor, diabetes, metabolic syndrome, hypo-high-density lipoproteinemia, and SDHH (P ≤ .033). CSA (odds ratio, 1.58 [95% confidence interval, 1.45-1.72]; P < .001) was the only significantly associated radiologic parameter among the studied radiologic parameters representing scapular morphology.

CONCLUSION

CSA (≥35°) is an independent associated factor for degenerative PSRCT after adjustment for the following suggested risk factors: age, waist circumference, dominant-side involvement, manual labor, diabetes, metabolic syndrome, hypo-high-density lipoproteinemia, and SDHH.

WITHDRAWN: Does anterior arthroscopic acromioplasty modify critical shoulder angle?

This article has been withdrawn because we accidentally published the same article twice due to an error by the Managing editor/Elsevier. The correct version of the article has been published later in Orthop Traumatol Surg Res, 108 (2022) 103040, https://doi.org/10.1016/j.otsr.2021.103040. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal

Quantification of acromioplasty. Systematic review of the literature

INTRODUCTION

Acromioplasty is controversial. Technically, it consists in bone resection, but there is no gold-standard technique and resection is often not quantified. The aims of the present study were 1/to assess the methodological quality of studies of acromioplasty; 2/to identify reports in which acromioplasty was quantified; and 3/to assess any correlation between clinical results and resection quantity.

MATERIAL AND METHODS

A systematic literature review was performed on PRISMA criteria in the PubMed, Springer and Ovid databases, including all articles in French or English referring to acromioplasty. Articles were analyzed by 2 surgeons and those with complete procedural description were selected. 1/Methodology was assessed on 3 grades according to aim of acromioplasty, intraoperative assessment of resection, and postoperative radiologic assessment. 2/Results were extracted from articles with robust methodology and quantitative data. 3/Correlations were assessed between clinical results and resection quantity.

RESULTS

Out of the 250 articles retrieved, 94 were selected. 1/44 of these (47%) specified the aim of the acromioplasty, 53 (56%) included an intraoperative clinical assessment criterion, and 13 (14%) included postoperative radiographic assessment. Methodologic quality was insufficient in 33 articles (35%), poor in 23 (24%) and robust in 38 (40%). 2/Seven articles (7.5%) included quantitative results. 3/Three articles assessed correlation between clinical results and resection quantity, but only 1 used reproducible radiographic assessment by critical shoulder angle (CSA); this study reported a significant positive correlation between clinical results and decreased CSA.

CONCLUSION

Methodology in studies of acromioplasty was largely insufficient and resection was usually not quantified. Current data to assess the usefulness of the procedure are sparse. We advocate including a Checklist for Acromioplasty Studies in the methodology of future studies. There is at present no gold-standard for assessing and quantifying acromial resection. CSA seems contributive, but other methods might be worth developing.

LEVEL OF EVIDENCE

IV; systematic review of level 1-4 studies.

Usefulness of computed tomography based three-dimensional reconstructions to assess the critical shoulder angle

BACKGROUND

The critical shoulder angle (CSA) is a radiographic measurement that provides an assessment of both glenoid inclination and acromial length. Higher values may correlate with the presence of rotator cuff tears. However, it is difficult to obtain a high-quality true anteroposterior (AP) radiograph of the shoulder, with any excess scapular version or flexion/extension resulting in deviation from the true CSA value. Three-dimensional (3D) bony reconstructions of computed tomography (CT) shoulder scans may be able to be rotated to obtain a similar view to that of true AP radiographs.

AIM

To compare CSA measurements performed on 3D bony CT reconstructions, with those on corresponding true AP radiographs.

METHODS

CT shoulder scans were matched with true AP radiographs that were classified as either Suter-Henninger type A or C quality. 3D bony reconstructions were segmented from the CT scans, and rotated to replicate an ideal true AP view. Two observers performed CSA measurements using both CT and radiographic images. Measurements were repeated after a one week interval. Reliability was assessed using intraclass correlation coefficients (ICCs) and Bland-Altman plots [bias, limits of agreement (LOA)].

RESULTS

Twenty CT shoulder scans were matched. The mean CSA values were 32.55° (± 4.26°) with radiographs and 29.82° (± 3.49°) with the CT-based method [mean difference 2.73° (± 2.86°); P < 0.001; bias +2.73°; LOA -2.17° to +7.63°]. There was a strong correlation between the two methods (r = 0.748; P < 0.001). Intra-observer reliability was similar, but the best intra-observer values were achieved by the most experienced observer using the CT-based method [ICC: 0.983 (0.958-0.993); bias +0.03°, LOA -1.28° to +1.34°]. Inter-observer reliability was better with the CT-based method [ICC: 0.897 (0.758-0.958), bias +0.24°, LOA -2.93° to +3.41°].

CONCLUSION

The described CT-based method may be a suitable alternative for critical shoulder angle measurement, as it overcomes the difficulty in obtaining a true AP radiographic view.

Influence of Radiographic Parameters on Reduction of the Critical Shoulder Angle With Arthroscopic Lateral Acromioplasty-A Mathematical Model

Objectives

To develop a mathematical model for the preoperative planning of arthroscopic lateral acromioplasty (ALA) and to evaluate the role of radiographic parameters with regards to the critical shoulder angle (CSA).

Methods

Anteroposterior (AP) radiographs of patients who underwent rotator cuff surgery were screened to identify true AP radiographs. Radiographs were assessed for (1) native CSA, (2) CSA after simulated resection of a spur if present, (3) amount of ALA necessary to achieve a CSA of 34°, (4) CSA after 5-mm ALA, (5) lateral acromion angle, (6) acromion index, and (7) sclerosis of the greater tuberosity.

Results

A total of 1191 radiographs were screened. Of the 124 patients included, the native CSA was large (≥35°) in 56 patients (45%). In 30 patients (24%), a subacromial spur was detected and resection reduced the CSA by a median of 2°. Spur resection alone reduced the CSA to ≤34° in 19 patients (15.3%). Mean amount of ALA to achieve a CSA of 34° was 3.9 ± 1.8 mm, and this value strongly correlated with the CSA before ALA (R = 0.88, P < .001). The linear regression model to determine the amount of ALA to achieve a CSA of 34° was as follows: R e q u i r e d A L A i n m m = - 39.120 + 1.165 ∗ C S A n a t i v e The multiple R² for this model was 0.777. Mean reduction of CSA by 5-mm ALA was 3.8 ± 0.8° and 75% of large CSAs were reduced to a CSA of 30-34°. The acromion index had no significant independent influence on the model (P = .427), whereas lateral acromion angle was an independently significant predictor of required ALA to achieve a CSA of 34° (P = .019). Sclerosis of the greater tuberosity was significantly associated with a CSA of 35° or greater (P = .003).

Conclusions

The amount of ALA needed to reduce a large CSA to 34° correlates with the CSA before ALA and can preoperatively be planned with the use of a simple equation.

Level of Evidence

Level III; cross-sectional design; epidemiology study.

The Lateral Deltoid Originates From the Entire Lateral Wall of the Acromion: MRI and Histologic Cadaveric Analysis Regarding Vertical Lateral Acromioplasty

Purpose

The aim of this study was to assess the nature of the middle deltoid muscle insertion onto the lateral acromion by macroscopic, MRI and histologic examination and to, therefore, assess the potential impact of a vertical lateral acromioplasty on the deltoid origin.

Methods

We assessed the acromial origin of the deltoid in 6 cadaver shoulders by macroscopic, MRI and histologic examination. The cadavers were scanned with T1 and proton density-weighted sequences. H&E- and Masson trichrome-stained histologic sections through the acromion were taken and visualized under polarized microscopy.

Results

The enthesis of the deltoid muscle consisted of dense birefringent bundles of collagen that blended with the bony endplate of the acromion at all points on its lateral wall. A prominent band of collagen was seen on both MRI and histologic slices, traversing the superior surface of the acromion. It was continuous with the deltoid origin and blended with the superficial fascia of the deltoid laterally.

Conclusions

The middle deltoid muscle occupies the entire lateral acromion.

Clinical Relevance

A high critical shoulder angle is associated with rotator cuff tears. A lateral acromioplasty resects the lateral acromion and aims to normalize the critical shoulder angle. However, a vertical lateral acromioplasty may release the middle deltoid origin from the lateral acromion. The superior band of collagen may anchor the middle deltoid to the superior acromion and prevent retraction.

Position of the acromioclavicular joint and relation to the critical shoulder angle in shoulders with rotator cuff tears

OBJECTIVE

To evaluate the position of the acromioclavicular joint (ACJ) and relation to the critical shoulder angle (CSA) in shoulders with rotator cuff tears (RCT).

METHODS

In a matched pair study including 75 shoulders with arthroscopically validated RCT and 75 controls (mean age 59.4 ± 7.9 years) the position of the ACJ in relation to the glenoid and the CSA were measured on true ap radiographs.

RESULTS

The CSA is larger (p = 0.0018) and the position of the ACJ is more lateral (p = 0.0016) in shoulders with RCT in comparison to matched controls.

CONCLUSION

The more lateral position of the ACJ in shoulders with a large CSA might be an additional component in the multifactorial pathogenesis of RCT.

Critical Shoulder Angle and Its Clinical Correlation in Shoulder Pain

Introduction The critical shoulder angle is defined as the angle formed between the plane of the glenoid and the line connecting the most lateral border of the acromion process, as seen on the true anteroposterior radiograph of the shoulder. The purpose of this study was to determine the association between the critical shoulder angle and shoulder pathologies like rotator cuff tears and glenohumeral osteoarthritis. It was also to assess the reproducibility and accuracy of critical shoulder angle values, which were measured with radiographs.  Objective The aim of the study was to find out the association between the critical shoulder angle and shoulder injuries in a rural population cohort. The secondary aims were to assess clinical and radiological correlations between the critical shoulder angle and the symptomology of shoulder pain. Materials and methods Our study analysis was a prospective design conducted at R L Jalappa Hospital & Research Centre, Karnataka, South India. After meeting the inclusion and exclusion criteria, 100 patients were recruited for the study. Forty-five patients had glenohumeral osteoarthritis and 55 patients had a diagnosis of rotator cuff tears. The majority of the patients were male (70%) in both the glenohumeral osteoarthritis and rotator cuff tear groups. The mean critical shoulder angles in the glenohumeral osteoarthritis and rotator cuff tear groups were 30.31 and 33.62, respectively. Conclusions Our data aid in demonstrating that glenohumeral osteoarthritis is associated with a significantly narrower critical shoulder angle and wider critical shoulder angles in rotator cuff disease. Further studies, however, should determine whether this association has a cause-and-effect relationship.

Three-dimensional scapular morphology is associated with rotator cuff tears and alters the abduction moment arm of the supraspinatus

BACKGROUND

Numerous studies have reported an association between rotator cuff injury and two-dimensional measures of scapular morphology. However, the mechanical underpinnings explaining how these shape features affect glenohumeral joint function and lead to injury are poorly understood. We hypothesized that three-dimensional features of scapular morphology differentiate asymptomatic shoulders from those with rotator cuff tears, and that these features would alter the mechanical advantage of the supraspinatus.

METHODS

Twenty-four individuals with supraspinatus tears and twenty-seven age-matched controls were recruited. A statistical shape analysis identified scapular features distinguishing symptomatic patients from asymptomatic controls. We examined the effect of injury-associated morphology on mechanics by developing a morphable model driven by six degree-of-freedom biplanar videoradiography data. We used the model to simulate abduction for a range of shapes and computed the supraspinatus moment arm.

FINDINGS

Rotator cuff injury was associated with a cranial orientation of the glenoid and scapular spine (P = .011, d = 0.75) and/or decreased subacromial space (P = .001, d = 0.94). The shape analysis also identified previously undocumented features associated with superior inclination and subacromial narrowing. In our computational model, warping the scapula from a cranial to a lateral orientation increased the supraspinatus moment arm at 20° of abduction and decreased the moment arm at 160° of abduction.

INTERPRETATIONS

Three-dimensional analysis of scapular morphology indicates a stronger relationship between morphology and cuff tears than two-dimensional measures. Insight into how morphological features affect rotator cuff mechanics may improve patient-specific strategies for prevention and treatment of cuff tears.

The critical shoulder angle (CSA) in glenohumeral osteoarthritis: Does observer experience affect measurement reliability on plain radiographs?

Background

The critical shoulder angle (CSA) has been associated with full-thickness rotator cuff tears both in the presence and absence of glenohumeral arthritis. It is unclear whether the CSA can be reliably measured from plain radiographs of concentric glenohumeral osteoarthritis amongst examiners at differing levels of training.

Methods

We retrospectively reviewed the radiographs of consecutive patients who underwent shoulder arthroplasty for glenohumeral osteoarthritis. The CSA was measured on a standardized AP scapular view at baseline and then 4 weeks later by fellowship-trained orthopaedic surgeons, a shoulder fellow and a senior orthopaedic resident. Grade of arthritis was categorized using the Samilson and Prieto method. The inter- and intra-observer reliability was then determined for all examiners, as well as for increasing severity of radiographic arthritis. The relationship between the CSA and grade of arthritis was assessed.

Results

There were 166 included patients comprised of 104 females (63%) and 62 males (37%) with a mean age of 65.9 ± 10.4 years. The inter- and intra-observer reliability for measuring the CSA amongst all examiners was found to be excellent, with an intra-class coefficient (ICC) of >0.9 (p < 0.0001). The ICC remained excellent even amongst radiographs with more advanced arthritis. Furthermore, there was a weak, inverse relationship between the grade of arthritis and the CSA (r = -0.377, p < 0.005).

Conclusion

The CSA can reliably be measured by examiners at varying levels of orthopaedic training, even with more advanced radiographic glenohumeral osteoarthritis. Level of evidence: Level III (Prognostic).

Role of shoulder gradient in the pathogenesis of rotator cuff tears

BACKGROUND

Shoulder gradient has been associated with shoulder pathologies such as shoulder impingement syndrome.

AIM

To investigate if there is an association between shoulder gradient and incidence of rotator cuff tear (RCT).

METHODS

A total of 61 patients with a confirmed diagnosis of RCT were included in this retrospective study. The anteroposterior radiograph of the shoulder was used to measure shoulder gradient in adduction and neutral rotation positions. The pain level was assessed with the visual analog scale for pain.

RESULTS

The mean age of the patients was 55.7 ± 12.3 years. The mean visual analog scale of the patients was 4.1 ± 1.2. The mean shoulder gradient was 14.11º ± 2.65º for the affected shoulder and 15.8º ± 2.2º for the unaffected shoulders. This difference was not statistically significant (P = 0.41). A difference of 1.15º ± 1.82º was found between the injured and non-injured shoulder. No significant association was found between the gradient difference of the shoulder and demographic and clinical characteristics of the patients.

CONCLUSION

Shoulder gradient is not associated with the pathology of RCT. Yet, future studies with more standardization and a larger sample size are needed to investigate the role of shoulder gradient in RCT pathogenesis further.

WITHDRAWN: Does anterior arthroscopic acromioplasty modify critical shoulder angle?

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Critical shoulder angle: what do radiologists need to know?

The critical shoulder angle (CSA) constitutes a straightforward and highly reproducible tool. Degenerative rotator cuff tears (RCT) are associated with a significantly larger CSA. In this review, the most relevant features of the CSA are summarized: (1) the relationship between the CSA and RCT pathophysiology, (2) accurate measurement of the CSA according to various imaging modalities, (3) the contribution of the CSA in predicting the occurrence of RCT, and (4) RCT recurrence after surgical repair.

The Critical Shoulder Angle Shows a Reciprocal Change in Magnitude When Evaluating Symptomatic Full-Thickness Rotator Cuff Tears Versus Primary Glenohumeral Osteoarthritis as Compared With Control Subjects: A Systematic Review and Meta-analysis

PURPOSE

To determine whether a high critical shoulder angle (CSA) is associated with symptomatic full-thickness rotator cuff (RC) tears and/or whether a low CSA is associated with primary glenohumeral osteoarthritis (GHOA).

METHODS

A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. All observational studies that examined an association between CSA and full-thickness RC tears and/or primary GHOA were included. A primary meta-analysis was performed including all studies that met the inclusion criteria regardless of radiographic quality. A secondary meta-analysis was performed to explore the hypothesis that radiographic quality was a source of heterogeneity, which excluded those studies in which radiograph quality was not strictly defined and controlled.

RESULTS

For the primary meta-analysis, 11 studies met the inclusion criteria for RC tears and 5 for primary GHOA. The CSA was greater in the RC tear group than the control group (mean difference 4.03°, 95% confidence interval 2.95°-5.11, 95% prediction interval 0.0487°-8.01°; P < .001). The CSA was lower in the GHOA group than the control group (mean difference -3.98°, 95% confidence interval -5.66° to -2.31°, 95% prediction interval -10.2° to -2.19°; P < .001).A high level of heterogeneity was observed in the RC tear analysis (I² = 88.4), which decreased after the exclusion of 5 studies based on radiographic quality (I² = 75.3). A high level of heterogeneity also was observed in the primary GHOA analysis (I² = 87.3), which decreased after the exclusion of 2 studies based on the radiographic quality (I² = 48.2).

CONCLUSIONS

There is a reciprocal change in magnitude of the CSA when evaluating symptomatic full-thickness RC tears versus primary GHOA as compared with control subjects. Radiographic quality is a source of heterogeneity in studies that investigate a link between CSA and RC tears and primary GHOA.

LEVEL OF EVIDENCE

Level III, systematic review and meta-analysis of Level III studies.

Biomechanical analysis of the humeral head coverage, glenoid inclination and acromio-glenoidal height as isolated components of the critical shoulder angle in a dynamic cadaveric shoulder model

BACKGROUND

The Critical Shoulder Angle was introduced as a combined radiographic surrogate parameter reflecting the influence of the morphological characteristics of the scapula on the development of degenerative shoulder disease such as rotator cuff tears and osteoarthritis. Although, glenoid inclination and lateral extension of the acromion were studied in biomechanical models separately, no investigation included all three individual parameters that determine the Critical Shoulder Angle: glenoid inclination, acromial coverage and acromial height in one cadaveric study protocol.

METHODS

Three proximal humerus cadavers were attached to a robotic shoulder simulator which allowed for independent change of either lateral acromial coverage, glenoid inclination or acromial height. Combined dynamic scapula-thoracic and glenohumeral abduction up to 60° with different Critical Shoulder Angle configurations was performed and muscle forces as well as joint reaction forces were recorded.

FINDINGS

All three components had an effect on either muscle forces and or joint reaction forces. While glenoid inclination showed the highest impact on joint stability with increasing upward-tilting causing cranial subluxation, changing of the lateral acromial coverage or acromial height had less influence on stability but showed significant alteration of joint reaction forces.

INTERPRETATION

All three components of the Critical Shoulder Angle, glenoid inclination, lateral acromial extension and acromial height showed independent biomechanical effects when changed isolated. However, glenoid inclination seems to have the largest impact regarding joint stability.

Is Bony Morphology and Morphometry Associated With Degenerative Full-Thickness Rotator Cuff Tears? A Systematic Review and Meta-analysis

PURPOSE

To scope the scientific literature and analyze the influence of bony risk factors for degenerative full-thickness primary rotator cuff tear.

METHODS

A systematic review of databases PubMed, Scopus, EMBASE, and Cochrane Library was performed up to June 30, 2018. Meta-analysis was performed with mean difference (MD) or risk ratio for degenerative full-thickness rotator cuff injury, and when there were ≥3 studies for the considered potential risk factor. Methodologic quality was assessed using the Newcastle-Ottawa scale.

RESULTS

We analyzed 34 studies comprising 5,916 shoulders (3,369 shoulders with rotator cuff tear and 2,546 controls) and identified 19 potential risk factors for degenerative full-thickness rotator cuff tears. There was moderate evidence that a higher critical shoulder angle (MD = 4.41, 95% confidence interval [CI] 3.43 to 5.39), higher acromion index (MD = 0.06, 95% CI 0.04 to 0.09), and lower lateral acromion angles (MD = -7.11, 95% CI -8.32 to -5.90) were associated with degenerative full-thickness rotator cuff tears compared with controls. Moderate evidence showed that a type III acromion significantly increases the risk for full-thickness degenerative rotator cuff tear (risk ratio = 2.26, 95% CI 1.38 to 3.70).

CONCLUSION

There is moderate evidence that larger critical shoulder angle, higher acromion index, lower lateral acromion angles, and a type III acromion are significantly associated with degenerative full-thickness rotator cuff tears. Other potential risk factors identified showed insufficient evidence.

LEVEL OF EVIDENCE

Level IV, systematic review of level II to IV studies.

Critical shoulder angle and greater tuberosity angle according to the partial thickness rotator cuff tear patterns

BACKGROUND

Current studies suggest that radiographic markers such as the critical shoulder angle (CSA) and the greater tuberosity angle (GTA) are associated with rotator cuff tears (RCTs). However, because the analysis of CSAs and GTAs according to the partial thickness rotator cuff tear patterns is limited, the purpose of the present study was to evaluate the relationship of CSAs and GTAs with partial thickness rotator cuff tear (PTRCT) patterns.

METHOD

This retrospective study included 1,069 patients from 2013 to 2017. The subjects were divided into 4 groups: Group A, control group; Group B, articular-sided PTRCTs; Group C, bursal-sided PTRCTs; and Group D, full thickness rotator cuff tears (FTRCTs). RCTs were diagnosed with magnetic resonance imaging and the CSA and GTA were measured on simple radiographs. Multivariable analyses were used to clarify the potential risks for these pathologies.

RESULTS

The mean CSAs of articular-sided PTRCTs (34.2°±4.7°) and FTRCTs (34.7°±4.4°) were significantly larger than those of the control group (32.3°±4.3°) and the bursal-sided PTRCTs (31.5°±4.6°), (P<0.001). Multivariable analysis also showed that larger CSAs had a significantly increased risk of both articular-sided PTRCTs and FTRCTs, with odds ratios of 1.12 and 1.17 per degree, respectively. The mean GTAs of bursal-sided PTRCTs (73.2°±4.8°) and FTRCTs (72.3°±5.4°) were significantly larger than that of the control group (70.5°±5.1°) (P<0.001), although the mean GTA of articular-sided PTRCTs (71.5°±6.9°) did not show a significant difference when compared with the other groups. Multivariable analysis also showed that larger GTAs had a significantly increased risk of both bursal-sided PTRCTs and FTRCTs, with odds ratios of 1.13 and 1.07 per degree, respectively.

CONCLUSION

A large critical shoulder angle was associated more with articular-sided PTRCTs than bursal-sided PTRCTs. A large greater tuberosity angle was associated more with bursal-sided PTRCTs than with articular-sided PTRCTs. Both critical shoulder angle and greater tuberosity angle were positively associated with the occurrence of full thickness rotator cuff tears.

LEVEL OF EVIDENCE

IV, Retrospective study.

Anatomic shoulder parameters and their relationship to the presence of degenerative rotator cuff tears and glenohumeral osteoarthritis: a systematic review and meta-analysis

BACKGROUND

Scapular anatomy, as measured by the acromial index (AI), critical shoulder angle (CSA), lateral acromial angle (LAA), and glenoid inclination (GI), has emerged as a possible contributor to the development of degenerative shoulder conditions such as rotator cuff tears and glenohumeral osteoarthritis. The purpose of this study was to investigate the published literature on influences of scapular morphology on the development of degenerative shoulder conditions.

METHODS

A systematic review of the Embase and PubMed databases was performed to identify published studies on the potential influence of scapular bony morphology on the development of degenerative rotator cuff tears and glenohumeral osteoarthritis. The studies were reviewed by 2 authors. The findings were summarized for various anatomic parameters. A meta-analysis was completed for parameters reported in more than 5 related publications.

RESULTS

A total of 660 unique titles and 55 potentially relevant abstracts were reviewed with 30 published articles identified for inclusion. The AI, CSA, LAA, and GI were the most commonly reported bony measurements. Increased CSA and AI correlated with rotator cuff tears, whereas lower CSA appeared to be related to the presence of glenohumeral osteoarthritis. Decreased LAA correlated with degenerative rotator cuff tears. Five articles reported on the GI with mixed results on shoulder pathology.

DISCUSSION

Degenerative rotator cuff tears appear to be significantly associated with the AI, CSA, and LAA. There does not appear to be a significant relationship between the included shoulder parameters and the development of osteoarthritis.

The Relationship Between the Critical Shoulder Angle and the Incidence of Chronic, Full-Thickness Rotator Cuff Tears and Outcomes After Rotator Cuff Repair: A Systematic Review

PURPOSE

To summarize the available evidence and examine the relationship between the critical shoulder angle (CSA) and (1) the incidence of chronic full-thickness rotator cuff tears (RCTs) and (2) outcomes after rotator cuff repair (RCR).

METHODS

A comprehensive search of MEDLINE, Embase, and CINAHL was completed. Comparative studies were included and the influence of the CSA on either the incidence of chronic, full-thickness RCTs, or outcomes following RCR was evaluated. Demographic variables and outcomes were collected.

RESULTS

Seven comparative studies analyzed the influence of the CSA on the incidence of chronic, full-thickness RCTs (the control group constituted patients with a normal rotator cuff). High heterogeneity limited pooling of studies, but the majority concluded that a greater CSA significantly increased the likelihood of a chronic, full-thickness RCT. Conversely, 5 comparative studies analyzed the influence of CSA on outcomes following RCR, and although a greater CSA was associated with a greater re-tear rate, the majority reported that CSA did not significantly influence postoperative functional outcomes, including patient-reported outcome measures (PROMs), range of motion (ROM), and strength.

CONCLUSIONS

Based on the available evidence, there appears to be a relationship between a greater CSA and the presence of a chronic, full-thickness RCT. Furthermore, a greater CSA may be associated with a greater re-tear rate following RCR; however, CSA does not appear to influence functional outcomes following RCR. Despite these observations, the available evidence is of poor quality, and the clinical utility and role of the CSA in the diagnosis and surgical management of a chronic, full-thickness RCT remains in question.

LEVEL OF EVIDENCE

Level IV: Systematic review of Level II-IV studies.