Glenohumeral joint reaction forces increase with critical shoulder angles representative of osteoarthritis-A biomechanical analysis

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

BACKGROUND

Descriptions of glenoid deformities in glenohumeral osteoarthritis (GHOA) have focused on the axial plane. Less is known regarding arthritic glenoids with higher amounts of superior inclination and little evidence exists to guide management of inclination or combined version-inclination deformity when performing anatomic total shoulder arthroplasty (aTSA). We hypothesized that biplanar deformities (BD) would be present in a higher proportion of GHOA patients than previously appreciated, and these deformities would be difficult to adequately reconstruct with contemporary aTSA implants.

METHODS

A retrospective query was performed of GHOA patients indicated for TSA 2012-2017 with a computed tomography (CT) scan within three months of surgery. Images were uploaded to three-dimensional (3D) software for automated measurements. Glenoids with superior inclination ≥10°, and retroversion ≥20° were considered to have BD. Walch classification was determined, and C-type glenoids were excluded. Rotator-cuff muscle cross-sectional area (CSA) was measured and fatty infiltration was graded. Glenoids with BD were virtually planned for aTSA with correction to neutral inclination and version, then with 5° superior inclination and 10° retroversion.

RESULTS

Two-hundred and sixty-eight shoulders in 250 patients were included; average age was 65 years, 67% male. There were no differences in inclination between Walch types (P = .25). Twenty-nine shoulders with BD were identified (11%). These deformities were not associated with age (P = .47) or gender (P = .50) but were skewed towards Walch B-type, specifically B2 (P = .03). Acromial index and posterior humeral head subluxation were higher in BD patients (P = .04, P < .001, respectively). Biplanar deformities had similar cuff CSA compared to those without but were less frequently associated with fatty infiltration of the subscapularis (P = .05). When correcting to neutral version and inclination, 41% BD could not be reconstructed. Of those that could, 94% required augmented implants. When correcting to 5° superior inclination and 10° retroversion, 10% could not be reconstructed. Of those that could, 58% required augmented implants. With partial correction, augment use was predicted by retroversion >26° (P = .009). Inclination did not predict augment use (P = .90). Final implant position commonly involved unseating in the posterosuperior quadrant and cancellous exposure in the anteroinferior quadrant.

CONCLUSIONS

This retrospective computed tomography (CT)-based study of 268 shoulders with GHOA found an 11% prevalence of BD. These deformities were commonly associated with Walch B2 wear patterns. Virtual aTSA planning showed a high failure rate (41%) when correcting to neutral version and inclination. Posteriorly augmented implants were frequently required, and often still involved unseating in the posterosuperior quadrant, increased cancellous exposure in the anteroinferior quadrant, and vault perforation.

Anthropometric study of the scapula in a contemporary population from granada. Sex estimation and glenohumeral osteoarthritis prevalence

Anthropometric studies of the scapula have been rare in Spanish populations, nevertheless they are of current interest in forensic anthropology for estimation of sex. Although the estimation of sex is usually carried out on the pelvis and skull, other measurements related to the scapula can be helpful when the skeletal remains are incomplete. Glenohumeral osteoarthritis development is influenced, among others, by the morphology of the scapula, which is one of the less studied aspects. We carried out a descriptive study of anthropometric parameters in a series of 157 scapulae (82 individuals) on bone remains dated to the 20th century from a population of Granada (Southern Spain). Seventy seven (49%) were right-side and 80 (51%) left-side; 72 (45.9%) were from males and 85 (54.1%) from females, and the mean age at death was 70.76±11.7 years. The objective was to develop a discrimination function for sex estimation based on anthropometric parameters of the scapula other than those considered to date, and to analyze the prevalence of glenohumeral osteoarthritis in relation to selected anthropometric parameters. A logistic regression model based on parameters of the upper-external segment of the scapula was done. The obtained formula: 1/1+e^ (- (-57.911 + 0.350*B + 0283*C + 0.249*b + 0.166*a +-0.100*β) classifies male sex with 98.3% accuracy and female sex with 92.1%. Glenohumeral osteoarthritis was detected in 16.6% of individuals and was related to age (p<0.05), scapular length (p<0.05), glenoid width (p<0.05), glenopolar angle (p<0.05), and α angle (p<0.05) in bivariate analyses but showed no significant associations in multivariate analyses. This approach can be useful for anthropological-forensic identification when scapula remains are incomplete. Glenohumeral osteoarthritis is significantly associated with a smaller α angle.

The Modified Ultrasound-Assisted Method: A Study of the Correlation between Magnetic Resonance Imaging and the Ultrasound-Assisted Evaluation of the Critical Shoulder Angle

BACKGROUND

An increased or decreased critical shoulder angle (CSA) is a known risk factor for osteoarthritis, lesions, and re-ruptures in the rotator cuff. A CSA greater than 35° correlates with degenerative rotator cuff tears, while a CSA of less than 30° correlates with osteoarthritis in the glenohumeral joint. The diagnostic gold standard for its determination is X-ray or MRI.

OBJECTIVES

The primary objective of this research was to assess the viability of utilizing sonography imaging as a diagnostic tool to determine the modified critical shoulder angle (mCSA). This study aimed to investigate the feasibility and effectiveness of sonographic techniques in accurately diagnosing CSA compared to MRI.

STUDY DESIGN AND METHODS

A cohort study was carried out (level of evidence 3). The CSA (MRI) and the mCSA (ultrasound) were assessed retrospectively by two independent board-certified investigators in 109 patients with shoulder pain by MRI and musculoskeletal sonography. The CSA in the MRI dataset was determined using routine protocols and then compared to the values assessed using the modified sonography-assisted method (mCSA). Both results were analyzed with linear regression to determine a possible correlation. All investigations were performed by a DEGUM (German Society for Medical Ultrasound)-certified specialist in musculoskeletal sonography.

RESULTS

A total of 112 patients were included in this study, namely 40 female patients and 72 male patients with a mean age of 54.7 years at the time of the investigation. The mean CSA in MRI was 31.5° ± 3.899, and the mCSA in sonography was 30.1° ± 4.753. The inter- and intraobserver reliability for the CSA was factual with values of 0.993 and 0.967. The inter- and intraobserver reliability for mCSA was factual as well, with values of 0.989 and 0.948. The ANOVA analysis did not reveal a significant difference between the CSA and the mCSA values, and linear regression determined the R2 value to be 0.358 with p < 0.05.

CONCLUSIONS

Diagnosing the mCSA using sonography is a safe and valid method. No statistically significant differences between the results in MRI and sonography could be seen. Although this is a retrospective, single-center study including only Caucasian mid-Europeans, and with the known limitations of ultrasound imaging, it nevertheless shows that sonography can be used as a simple, cheap, and fast technique to assess a modified CSA, which shows very good correlation with the standard CSA without losing the diagnostic quality.

The value of the glenohumeral joint cross-sectional area as a morphological parameter of glenohumeral osteoarthritis

Glenohumeral joint (GHJ) space narrowing has been demonstrated to be an important morphologic parameter of glenohumeral osteoarthritis (GHO). However, the morphology of GHJ space is irregular because of degeneration of subchondral bone and articular cartilage. Thus, we devised GHJ cartilage cross-sectional area (GHJCCSA) as a new diagnostic morphological parameter to assess the irregular morphologic change of GHJ. GHJ samples were acquired from 33 patients with GHO and from 33 normal controls without evidence of GHO based on shoulder magnetic resonance imaging. T2-weighted coronal MRIs were collected at the GHJ level for all individuals. GHJCCSA and GHJ cartilage thickness (GHJCT) at the GHJ were measured on MRIs using a graphic measuring system. The GHJCCSA was measured as the whole cartilage cross-sectional area of the GHJ. The average GHJCCSA was 115.28 ± 17.36 mm2 in normal individuals and 61.77 ± 13.74 mm2 in the GHO group. The mean GHJCT was 2.06 ± 0.35 mm in normal individuals and 1.50 ± 0.28 mm in the GHO group. GHO patients had significantly lower GHJCCSA (P < .001) and GHJCT (P < .001) than normal individuals. Receiver operator characteristics curve analysis revealed that the optimal cutoff score of the GHJCCSA was 82.21 mm2, with a sensitivity of 97.0%, a specificity of 97.0%, and an area under the curve of 0.99 (95% CI: 0.97-1.00). Although GHJCCSA and GHJCT were both significantly associated with GHO, the GHJCCSA was a more sensitive measurement parameter.

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.

Measuring the critical shoulder angle on radiographs: an accurate and repeatable deep learning model

PURPOSE

Since the critical shoulder angle (CSA) is considered a risk factor for shoulder pathology and the intra- and inter-rater variabilities in its calculation are not negligible, we developed a deep learning model that calculates it automatically and accurately.

METHODS

We used a dataset of 8467 anteroposterior x-ray images of the shoulder annotated with 3 landmarks of interest. A Convolutional Neural Network model coupled with a spatial to numerical transform (DSNT) layer was used to predict the landmark coordinates from which the CSA was calculated. The performances were evaluated by calculating the Euclidean distance between the ground truth coordinates and the predicted ones normalized with respect to the distance between the first and the second points, and the error between the CSA angle measured by a human observer and the predicted one.

RESULTS

Regarding the normalized point distances, we obtained a median error of 2.9%, 2.5%, and 2% for the three points among the entire set. Considering CSA calculations, the median errors were 1° (standard deviation 1.2°), 0.88° (standard deviation 0.87°), and 0.99° (standard deviation 1°) for angles below 30°, between 30° and 35°, and above 35°, respectively.

DISCUSSION

These results demonstrate that the model has the potential to be used in clinical settings where the replicability is important. The reported standard error of the CSA measurement is greater than 2° that is above the median error of our model, indicating a potential accuracy sufficient to be used in a clinical setting.

Quantitative SSM-based analysis of humeral head migration in rotator cuff tear arthropathy patients

Rotator cuff tear arthropathy (RCTA) is characterized by massive rotator cuff tearing combined with humeral head migration (HHM). The aim of this study is to investigate the quantitative characteristics of this migration and its association with glenoid erosions and prearthropathy scapular anatomy. We quantified HHM and prearthropathy scapular anatomy of 64 RCTA patients with statistical shape modeling-based techniques. Glenoid erosion was classified according to Sirveaux et al. A cutoff value for confirming HHM was 5 mm based on a control group of 49 patients. Group 1 (RCTA without HHM) consisted of 21 patients, with a mean subluxation distance (SLD) of 3 mm. Group 2 (RCTA with HHM) consisted of 43 patients, with mean SLD of 9 mm, SLD in the anteroposterior plane of -1 mm (SD ± 4 mm), SLD in the superoinferior plane of 7 mm (SD ± 3 mm), and subluxation angle (SLA) of -5° (SD ± 40°). Analysis with Fisher's exact test showed a clear association between HHM and glenoid erosions (p = 0.002). Multivariate regression analysis of Group 2 showed that prearthropathy lateral acromial angle combined with critical shoulder angle (p = 0.004) explained 21% of the observed variability in SLD. The prearthropathy glenoid version explained 23% of the variability in SLA (p = 0.001). HHM in RCTA patients has a wide variation in both magnitude and direction leading to a distorted glenohumeral relationship in the coronal and axial plane. HHM is highly associated with the occurrence of glenoid erosions. There is a correlation between the prearthropathy scapular anatomy and the magnitude and direction of HHM.

Lateral Acromioplasty With the Aim of Reducing the Critical Shoulder Angle Using Techniques Based on the Lateral Acromial Border Result in Larger-Than-Necessary Resections

Purpose

Methods

Results

Conclusions

Clinical relevance

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.

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.

Association of the Posterior Acromion Extension with Glenoid Retroversion: A CT Study in Normal and Osteoarthritic Shoulders

Posterior eccentric glenoid wear is associated with higher complication rates after shoulder arthroplasty. The recently reported association between the acromion shape and glenoid retroversion in both normal and osteoarthritic shoulders remains controversial. The three-dimensional coordinates of the angulus acromialis (AA) and acromioclavicular joint were examined in the scapular coordinate system. Four acromion angles were defined from these two acromion landmarks: the acromion posterior angle (APA), acromion tilt angle (ATA), acromion length angle (ALA), and acromion axial tilt angle (AXA). Shoulder computed tomography scans of 112 normal scapulae and 125 patients with primary glenohumeral osteoarthritis were analyzed with simple and stepwise multiple linear regressions between all morphological acromion parameters and glenoid retroversion. In normal scapulae, the glenoid retroversion angle was most strongly correlated with the posterior extension of the AA (R² = 0.48, p < 0.0001), which can be conveniently characterized by the APA. Combining the APA with the ALA and ATA helped slightly improve the correlation (R² = 0.55, p < 0.0001), but adding the AXA did not. In osteoarthritic scapulae, a critical APA > 15 degrees was found to best identify glenoids with a critical retroversion angle > 8 degrees. The APA is more strongly associated with the glenoid retroversion angle in normal than primary osteoarthritic scapulae.

The Influence of Critical Shoulder Angle in Secondary Rotator Cuff Failure After Shoulder Replacement: An Age- and Sex-Matched Case-Control Study

Introduction

Decreased or increased critical shoulder angles (CSA) are associated with osteoarthritis or rotator cuff failure respectively. Secondary cuff failure after shoulder arthroplasty is disabling and often requires additional surgery. The aim of this study was to investigate if the initial CSA correlated with cuff failure in the context of shoulder arthroplasty.

Methods

Patients from a tertiary referral centre were reviewed from 2011-2017. Those who underwent revision from hemiarthroplasty (HA) or anatomic total shoulder arthroplasty (TSA) to a reverse shoulder arthroplasty (RSA) following rotator cuff failure were compared to an age and sex-matched control group. The CSA was calculated from initial pre-operative radiographs.

Results

In this study, 16 patients with symptomatic cuff failure after anatomic TSA or HA requiring revision to RSA were compared to a control group of 16 age- and sex-matched patients showing no signs of symptomatic cuff failure. The median CSA in the study group was significantly greater than that of the control group (31.5^o, IQR = 29.8 - 36.1^o vs. 29.5^o, IQR = 27.6 - 30.4^o; p= 0.026).

Conclusion

The difference in CSA between those who required revision for secondary cuff failure than those who didn’t suggest that pre-operative measurement of CSA may help guide surgical planning in shoulder arthroplasty.

A lower critical coracoid process angle is associated with type-B osteoarthritis: a radiological study of normal and diseased shoulders

Background

Degenerative rotator cuff tears and osteoarthritis (OA) are associated with differences in coronal plane scapular morphology, with particular focus on the effect of the critical shoulder angle (CSA) on shoulder biomechanics. The effect, if any, of axial plane scapular morphology is less well established. We have noticed wide disparity of axial coracoid tip position in relation to the face of the glenoid and sought to investigate the significance of this through measurement of the critical coracoid process angle (CCPA), which incorporates coracoid tip position and glenoid version.

Methods

CCPA, CSA, and glenoid retroversion were measured by three independent reviewers from the cross-sectional two-dimensional computed tomography (CT) and magnetic resonance imaging of 160 patients in four equal and matched case-control groups: (1) a control group of patients with a radiologically normal shoulder and no history of shoulder symptoms who had a CT thorax for another reason, (2) patients with primary OA with Walch type-A glenoid wear pattern on CT scan, (3) patients with type-B glenoid primary OA, and (4) patients with magnetic resonance imaging–proven atraumatic tears of the posterosuperior rotator cuff.

Results

Interobserver agreement was excellent for all measured parameters. The median CCPA was significantly lower in the type-B OA group (9.3˚) than that in controls (18.7˚), but not significantly different in the other study groups. There was a trend toward greater glenoid retroversion in the type-B OA group, but receiver operating characteristic curve analysis demonstrated the CCPA to be by far the most powerful discriminator for type-B OA. The optimal cutoff value was calculated for the CCPA at 14.3˚ with a sensitivity of 93% and specificity of 90% for type-B OA. Compared with controls, the CSA was significantly higher in the rotator cuff tear group and lower in both OA groups, but did not differentiate between type-A and type-B OA.

Conclusion

Combined with a lower CSA, a lower CCPA (<14.3˚) is strongly predictive of type-B glenoid OA. The authors propose a simple model of pectoralis major biomechanics to explain the effect of this axial plane anatomical variation, which requires further investigation.

Biconcave glenoids show 3 differently oriented posterior erosion patterns

BACKGROUND

Posterior glenoid wear remains a challenge in anatomic and reverse total shoulder arthroplasty (rTSA) because of an asymmetric erosion with altered retroversion. The purpose of this study was to assess glenoid morphology and evaluate the influence of acromial orientation in posterior glenoid erosion patterns by using 3-dimensional (3D) models.

MATERIAL AND METHODS

Computed tomographic (CT) shoulder scans from 3 study centers of patients awaiting rTSA between 2017 and 2018 were converted into 3D models and analyzed by 2 observers. Morphology, orientation and greatest depth of erosion, inclination, current retroversion and premorbid retroversion, surface areas of the glenoid, and external acromial orientation and posterior acromial slope were assessed. Measurements were compared between wear patterns, glenoid erosion entities, and genders.

RESULTS

In the complete cohort of 68 patients (63.8 ± 10.0 years; 19 female, 49 male), a mean of 85.9° (±22.2°) was observed for the glenoid erosion orientation. Additionally, a further distinct classification of the glenoid erosion as posterior-central (PC, n = 39), posterior-inferior (PI, n = 12), and posterior-superior (PS, n = 17) wear patterns was possible. These wear patterns significantly (P < .001) distinguished by erosion orientation (PC = 86.9° ± 12.0°, PI = 116.3° ± 10.3°, PS = 62.3° ± 18.9°). The greatest depth of erosion found was 7.3 ± 2.7 mm in PC wear patterns (PC vs. PI: P = .03; PC vs. PS: n.s.; PI vs. PS: n.s.). Overall, the observed erosion divided the glenoid surface into a paleoglenoid proportion of 48% (±11%) and a neoglenoid proportion of 52% (±12%). For the complete cohort, glenoid inclination was 85.4° (±6.6°), premorbid glenoid retroversion was 80.7° (±8.1°), and current glenoid retroversion was 73.4° (±7.4°), with an estimated increase of 6.9° (±6.0°). The mean external acromial orientation was 118.2° (±8.9°), and the mean posterior acromial slope was 107.2° (±9.6°). There were no further significant differences if parameters were compared by wear patterns, entities, and gender.

CONCLUSION

Three significantly differently oriented wear patterns (posterior-superior, posterior-central, and posterior-inferior) were distinguished in shoulders demonstrating posterior wear on axillary imaging. No significant differences between the observed erosion patterns or any relevant correlations were found regarding the orientation of the acromion.

Biomechanics of anatomic and reverse shoulder arthroplasty

The biomechanics of the shoulder relies on careful balancing between stability and mobility. A thorough understanding of normal and degenerative shoulder anatomy is necessary, as the goal of anatomic total shoulder arthroplasty is to reproduce premorbid shoulder kinematics.With reported joint reaction forces up to 2.4 times bodyweight, failure to restore anatomy and therefore provide a stable fulcrum will result in early implant failure secondary to glenoid loosening.The high variability of proximal humeral anatomy can be addressed with modular stems or stemless humeral components. The development of three-dimensional planning has led to a better understanding of the complex nature of glenoid bone deformity in eccentric osteoarthritis.The treatment of cuff tear arthropathy patients was revolutionized by the arrival of Grammont's reverse shoulder arthroplasty. The initial design medialized the centre of rotation and distalized the humerus, allowing up to a 42% increase in the deltoid moment arm.More modern reverse designs have maintained the element of restored stability but sought a more anatomic postoperative position to minimize complications and maximize rotational range of motion. Cite this article: EFORT Open Rev 2021;6:918-931. DOI: 10.1302/2058-5241.6.210014.

Determination of predisposing scapular anatomy with a statistical shape model-Part II: shoulder osteoarthritis

HYPOTHESIS AND BACKGROUND

Shoulder osteoarthritis can be divided into different glenoid types (A, B, C, and D) and subtypes. The aim of this study was to investigate if there is an association between the prearthropathy scapular anatomy, shoulder osteoarthritis, and different glenoid types and subtypes.

METHODS

Using principal components analysis, a statistical shape model (SSM) of the scapula was constructed from a data set of 110 computed tomographic (CT) scans. These subjects formed the control group. Next, CT scan images of 117 patients with osteoarthritis were classified according to the modified Walch classification. A complete 3-dimensional (3D) scapular bone model was created for every patient, and using the SSM, a reconstruction of their prearthropathy scapular anatomy was performed. Automated 3D measurements were performed in both the patient and control group to obtain glenoid version and inclination, critical shoulder angle (CSA), posterior acromial slope (PAS), lateral acromion angle, scapular offset, and the rotational alignment of the coracoacromial complex. These parameters were compared between controls, patients with osteoarthritis, and glenoid types and subtypes.

RESULTS

Mean version and inclination for the control group was 6° retroversion and 8° superior inclination (both SD 4°). The mean CSA, PAS, coracoid-posterior acromion angle, posterior acromion-scapular plane angle, and fulcrum axis ratio were 30° (SD 4°), 64° (SD 8°), 116° (SD 9°), 55° (SD 7°), and 46% (SD 4%), respectively. Patients with osteoarthritis had a significant lower CSA, posterior acromion-scapular plane angle, coracoid-posterior acromion angle, and fulcrum axis ratio (27°, 50°, 111°, and 44%, all P < .001). We found a significant difference between the control group and the respective glenoid types for the following parameters: mean CSA and coracoid-posterior acromion angle for A glenoids (27°, P = .001, and 111°, P = .007); mean version, CSA, PAS, coracoid-posterior acromion angle, posterior acromion-scapular plane angle, and fulcrum axis ratio for B glenoids (11°, 27°, 71°, 111°, 49°, and 43%, all P < .001); and mean version, CSA, and posterior acromion-scapular plane angle for D glenoids (2°, P = .002, 26°, P = .003, and 48°, P = .007).

DISCUSSION

There seems to be an association between prearthropathy scapular anatomy and shoulder osteoarthritis. A small lateral extension and less posterior rotation of the acromion is associated with shoulder osteoarthritis and is present in almost all types and subtypes of glenoid morphology. Furthermore, B and D glenoids are associated with, respectively, a more and less pronounced prearthropathy glenoid retroversion.

Three-dimensional evaluation of scapular morphology in primary glenohumeral arthritis, rotator cuff arthropathy, and asymptomatic shoulders

BACKGROUND

Recently, the 3-dimensional (3D) morphology of the coracoacromial complex in nonpathologic shoulders has been described. The aim of this study was to evaluate and compare the coracoacromial complex in pathologic shoulders (glenohumeral osteoarthritis [GHOA] and cuff tear arthropathy [CTA]) and nonpathologic shoulders.

METHODS

A 3D computed tomography reconstruction of 205 scapulae was performed (49 with GHOA, 48 with CTA, and 108 in normal shoulders [NL]). Subsequently, the center of the glenoid circle and several points at the coracoid, acromion, and glenoid were determined. The distances between these points and the rotation of the coracoacromial complex were calculated, and the acromion-glenoid angle was measured.

RESULTS

The acromial overhang was significantly different between the NL (37 mm) and CTA (35 mm) groups (P = .045), as well as between the CTA and GHOA groups (33 mm) (P = .010). The acromion-glenoid angle showed a significant difference between the NL (mean, 50°) and GHOA (mean, 42°) groups (P < .001) and between the CTA (mean, 50°) and GHOA groups (P < .001). Furthermore, a significant difference was found in the acromial height, which was larger in the GHOA group (36 mm) than in the CTA group (30 mm) (P < .001) or NL group (30 mm) (P < .001).

CONCLUSION

This 3D morphologic study showed that the acromial part of the complex was turned more posteriorly in both pathologic groups. Furthermore, we found the coracoacromial complex to be more cranial to the glenoid center in the GHOA group. Finally, a significant difference in the lateral overhang of the coracoacromial complex was observed between the 3 groups. The NL group had a larger overhang than the CTA group, and the CTA group in turn had a larger overhang than the GHOA group.

The critical shoulder angle does not change over time: a radiographic study

BACKGROUND

The anatomy of the scapula may predispose individuals to develop shoulder pathologies. The purpose of this study was to determine if the scapular anatomy, in particular the critical shoulder angle (CSA), changes over a long-term follow-up, or if it is a stable parameter. We hypothesized that increasing age would not influence the scapular morphology.

METHODS

We analyzed shoulder radiographs in our database from 2002 to 2019 to extract radiographs at an interval of at least 10 years. Radiographic analysis included measuring the CSA and assessing the acromion type according to Bigliani and Morrison, the posterior acromial height and the posterior acromial tilt.

RESULTS

A total of 41 patients (47 shoulders) with a mean age of 53 years (range, 15-76; standard deviation [SD], ±14) fulfilled the inclusion criteria. The mean interval between the 2 sets of radiographs was 12 years (range, 10-16; SD ±2).The mean CSA did not change significantly with 34° (range, 20-41; SD ±4) at the first and 34° (range, 19-44; SD ±5) (P = .597) at the second assessment. On the initial lateral radiographs ("Neer view"), there were 11 type 1 (24%), 32 type 2 (70%), and 3 type 3 (6%) acromia according to Bigliani and Morrison. At the second assessment, there were 16 type 1 (34%), 28 type 2 (60%), and 3 type 3 (7%). Between both sets of radiographs, 11 were different (23%), without a trend in the type of change being discernible. The posterior acromial height was stable with 19 mm (range, 2-36; SD ±8) at the first and 18 mm (range, 5-38; SD ±8) at the second assessment (P = .186). The posterior acromion tilt changed from 59° (range, 34-81; SD ±10) to 62° (range, 30-81; SD ±10) (P < .001). Among 6 cases with rotator cuff tears (RCTs) already at the first assessment, the CSA did not change significantly at 10 years' follow-up (P = .414). Among the 10 cases with new RCTs at the second assessment, the CSA did not change significantly at 10 years' follow-up from 34° (range, 25-41; SD ±5) to 35° (range, 24-44; SD ±6) (P = .510). In the group of 31 shoulders without RCT, the mean CSA at the first assessment of 34° (range, 28-41; SD ±3) stayed also stable with 34° (range, 28-40; SD ±3) (P = .796).

CONCLUSION

The CSA is an anatomical parameter of the scapula that does not change in size after closure of the physes.

The Effect of Acromial Morphology on the Functional Outcomes of Degenerative Rotator Cuff Tear Surgery

PURPOSE

The aim of this study was to investigate how the critical shoulder angle (CSA) and acromion index (AI) affect the outcome of arthroscopic rotator cuff tear (RCT) repair.

METHODS

A total of 287 patients, who underwent arthroscopic surgery due to degenerative rotator cuff tear, were evaluated. The Constant Shoulder Score (CSS), Oxford Shoulder Score (OSS) and Visual Analogue Scale (VAS) were evaluated preoperatively and postoperatively. The AI and CSA were measured on true anteroposterior shoulder radiographs. The patients were separated into two groups according to their CSA and AI values (control group ≤ 38°, increased CSA > 38°, and control group ≤ 0.7, increased AI > 0.7). The relationship between CSS, OSS and VAS was examined in all the groups.

RESULT

The evaluation was made of a total of 287 patients with a mean age of 60.29 ± 8.55 years. The mean duration of follow-up of the patients was 34.00 ± 18.97 months (range 12-80 months). There was a statistically significant difference between the preoperative and postoperative clinical scores of the patients (p < 0.05). No relationship was determined between CSA, AI and CSS, OSS or VAS during follow-up (p > 0.05). The interobserver ICC for CSA and AI were determined to be 0.962 and 0.967, respectively (95% CI) indicating a high correlation (p < 0.001).

CONCLUSION

CSA and AI do not affect functional outcomes in the postoperative period, so they are not significant at the time of degenerative arthroscopic rotator cuff repair decisions.

Effect of arthroscopic acromioplasty on reducing critical shoulder angle: a protocol for a prospective randomized clinical trial

Background

The critical shoulder angle (CSA), which helps to predict patients who are at risk of rotator cuff tears (RCTs) with large degree and who are susceptible to osteoarthritis with low angle, has been identified as one of the most vital acromial parameters; anterolateral and lateral acromioplasties have been proven to be valid ways to reduce CSA. However, no study has compared the effect of different acromioplasties on the reduction of the large CSA (≥33°) clinically. Additionally, either anterolateral or lateral acromioplasty could not precisely correct large CSAs to a favorable range (30–33°) in each patient. Thus, we will propose a novel precise acromioplasty technique for the purpose of reducing CSA accurately and effectively, and compare the effectiveness of different acromioplasties on the reduction of the CSA.

Methods

A total of 60 RCT patients who have indications for arthroscopic rotator cuff repair and with pre-operative CSA ≥33° will be recruited in outpatient center of Sun Yat-sen Memorial Hospital. Eligible participants will be randomly allocated to Group A (anterolateral acromioplasty), Group B (lateral acromioplasty) or Group C (precise acromioplasty) via a random, computer-generated number system. Three surgical plans will be made for each participant respectively by one professional surgeon according to the results of randomization allocation. The post-operative CSA will be measured 2 days post-operation. Follow-up will be maintained at 3, 6, and 12 months after surgery including the visual analog scale score, the University of California at Los Angeles score, the Constant Shoulder Score and the American Shoulder and Elbow Surgeon Shoulder Assessment Form. Finally, all outcomes will be assessed by two researchers who are blinded to the recruitment and allocation.

Discussion

This is the first clinical trial to evaluate the impact of different acromioplasties on the reduction of the CSA. Additionally, this study will provide a new precise acromioplasty technique, which is a novel precision and individualized treatment to prevent degenerative RCTs by reducing the CSA.

Trial registration

ChiCTR2000032343. Registered on April 26th, 2020.

The Critical Shoulder Angle as a Diagnostic Measure for Osteoarthritis and Rotator Cuff Pathology

The purpose of this study was to correlate critical shoulder angle (CSA), a measurement that takes into account both glenoid tilt and the acromial index (AI), with shoulder pathologies as presented in an earlier study by Moor et al. (2013). Based on Moor et al.’s predicted normal CSA range of 30-35°, we hypothesized that a greater-than-normal CSA would be correlated to or associated with rotator cuff pathology, while a smaller-than-normal CSA would be associated with osteoarthritis (OA). Following Moore et al., we utilized Grashey radiographic imaging because it provides the clearest view of the entire glenoid fossa and acromion. We analyzed 323 anterior-posterior (AP) radiographs to identify and measure the CSA, classifying each patient into one of five groups [none reported (n=94), mild OA (n=156), moderate OA (n=36), severe OA (n=37), and rotator cuff pathology (n=40)]. Our results were statistically significant, supporting the association of smaller CSAs with OA and larger CSAs with rotator cuff pathology. CSA measurements could provide a new means for identifying shoulder pathology and thereby reduce the need for costly and timely imaging techniques. CSA values could also provide useful information to utilize preventatively with interventions such as physical therapy to alter the CSA and reduce the prevalence of OA and shoulder arthroplasties. This study builds on the findings of Moore et al. in creating a correlation between CSA and shoulder pathology.

A biomechanical confirmation of the relationship between critical shoulder angle (CSA) and articular joint loading

BACKGROUND

The critical shoulder angle (CSA) has been shown to be correlated with shoulder disease states. The biomechanical hypothesis to explain this correlation is that the CSA changes the shear and compressive forces on the shoulder. The objective of this study is to test this hypothesis by use of a validated computational shoulder model. Specifically, this study assesses the impact on glenohumeral biomechanics of modifying the CSA.

METHODS

An inverse dynamics 3-dimensional musculoskeletal model of the shoulder was used to quantify muscle forces and glenohumeral joint forces. The CSA was changed by altering the attachment point of the middle deltoid into a normal CSA (33°), a reduced CSA of 28°, and an increased CSA of 38°. Subject-specific kinematics of slow and fast speed abduction in the scapular plane and slow and fast forward flexion measured by a 3-dimensional motion capture system were used to quantify joint reaction shear and compressive forces.

RESULTS

Increasing the CSA results in increased superior-inferior forces (shearing forces; integrated over the range of motion; P < .05). Reducing CSA results in increased lateromedial (compressive) forces for both the maximum and integrated sum of the forces over the whole motion (P < .01).

DISCUSSION/CONCLUSION

Changes in the CSA modify glenohumeral joint biomechanics with increasing CSA producing higher shear forces that could contribute to rotator cuff overuse, whereas reducing the CSA results in higher compressive forces that contribute to joint wear.

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).

Critical shoulder angle is intrinsically associated with the development of degenerative shoulder diseases: A systematic review

Aim of this study was to investigate the potential influence of Critical Shoulder Angle (CSA) as a predisposing factor for the development of degenerative full-thickness rotator cuff tears (DRCT) or primary glenohumeral osteoarthritis (PGOA). A systematic review of the Pubmed, Scopus, Mendeley, ScienceDirect and the Cochrane Central Register of Controlled Trials online databases was performed for literature regarding CSA and its association with DRCT and PGOA. In order to evaluate solely the relationship between CSA as a predisposing factor for the development of the aforementioned degenerative shoulder diseases (DSDs), we precluded any study in which traumatic cases were not clearly excluded. Our search strategy identified 289 studies in total, nine of which were eligible for inclusion based on our pre-established criteria. Quality assessment contacted using the Newcastle Ottawa Scale for case-control studies. There were a total of 998 patients with DRCT and 285 patients with PGOA. The control groups consisted of a total of 538 patients. The mean CSA ranged from 33.9° to 41.01° for the DRCT group, from 27.3° to 29.8° for the PGOA group and from 30.2° to 37.28° for the control group. All studies reported statistically significant differences between the DRCT and PGOA groups and the respective control groups. Our study results showed that there is moderate evidence in the literature supporting an intrinsic role of CSA in the development of DSDs. Level of evidence: IV. Systematic review of diagnostic studies, Level II-IV.

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.

Acromial Fractures Following Reverse Total Shoulder Arthroplasty: A Cohort Controlled Analysis

Fractures of the acromion can develop after reverse total shoulder arthroplasty (RTSA). This study sought to identify risk factors for acromial fractures in patients with RTSA. A total of 1146 RTSAs were performed at the authors' institution between 1999 and 2016. In 21 patients (1.8%), the authors identified an acromial fracture during the postoperative course. These patients were compared with a matched cohort of 84 patients who had not developed an acromial fracture postoperatively. As an indicator of changes in pre- to postoperative deltoid loading, the authors created an angle called the "delta angle." There was an elevated risk for acromial fractures with lower lateralization of the humerus from pre- to postoperatively (4.1±7.1 mm vs 8.4±6.1 mm; P=.006), lower preoperative anteroposterior acromial slope (117.3°±11.2° vs 121.7°±17.0°; P=.044), and higher glenoid inclination (beta angle, 72.0°±5.5° vs 76.5°±6.8°; P=.005). Pre- to postoperative changes in the beta angle (9.2°±8.0° vs 4.4°±9.4°; P=.022) and the delta angle (29.4°±8.1° vs 19.5°±9.7°; P<.001) were larger in the fracture group. In addition, diagnosed and treated osteoporosis appeared to be a risk factor for acromial fractures (33% vs 13%; P=.047). The delta angle after RTSA seems to correlate with the risk of developing an acromial fracture. Patients with a high glenoid inclination and/or osteoporosis should be informed that they are at risk. Further, surgeons should be aware that lower distalization together with greater medialization of the center of rotation was associated with more acromial fractures in this study. [Orthopedics. 2020; 43(1):15-22.].

Normal and Pathoanatomy of the Arthritic Shoulder: Considerations for Shoulder Arthroplasty

The glenohumeral joint is a highly mobile, complex articulation that relies not only on the bony support between the humeral head and glenoid but also on appropriate balance and tension of the surrounding soft-tissue structures. Recreating the normal anatomic relationships is a basic premise in joint arthroplasty, which can be challenging in shoulder arthroplasty, as the normal glenohumeral anatomy has considerable variation from patient to patient. Also, as the anatomy of the glenohumeral joint becomes distorted with advanced shoulder pathology, it becomes a challenge to return the shoulder to its premorbid anatomic state. Failure to restore normal anatomic parameters after shoulder arthroplasty has been shown to have deleterious effects on postoperative function and implant survival. As the recognition of this has grown, shoulder prostheses have evolved to allow for considerable more variation in an attempt to recreate patient-specific anatomy. However, understanding the progression of shoulder pathology to better predict the patient's premorbid anatomy remains limited. A thorough understanding of the premorbid and pathologic anatomy of the glenohumeral joint will aid in preoperative planning and intraoperative execution and lead to a more predictable reconstruction of the shoulder, which is critical for a successful outcome after shoulder arthroplasty.

Does an Increased Critical Shoulder Angle Affect Re-tear Rates and Clinical Outcomes Following Primary Rotator Cuff Repair? A Systematic Review

PURPOSE

To determine if an increased critical shoulder angle (CSA) predisposes patients to higher re-tear rates and worse clinical outcomes after rotator cuff (RC) repair.

METHODS

A comprehensive search of the PubMed, MEDLINE, and EMBASE databases was performed in October 2018 for English-language studies pertaining to RC repair and an increased CSA in accordance with Preferred Reported Items for Systematic Reviews and Meta-analyses guidelines. Studies of all levels of evidence were included provided that any outcomes, including pain, patient-reported outcomes, and re-tear rates, were reported.

RESULTS

Of a group of 1126 studies that satisfied the initial search criteria, 6 studies were included in the final analysis, comprising data from 473 patients. Three comparative studies were assessed for an association between increased CSA and RC re-tear rates. Among these 3 studies that compared RC re-tear rate in patients with larger and smaller CSAs, 22 of 97 patients (23%) with a larger CSA had a RC re-tear in comparison to 10 of 99 patients (10%) with a smaller CSA. All 3 studies demonstrated higher RC re-tear rates in patients with larger CSAs (risk ratio, 2.39-9.66, I² = 7%.) The mean CSA in those patients who did not have RC re-tears ranged from 34.3° to 37°, and the mean CSA in those patients who had RC re-tears ranged from 37° to 40°.

CONCLUSION

RC re-tear rates were higher in patients with larger CSAs among comparative, nonrandomized studies. However, the heterogeneity of the relevant literature limits the strength of his observation. Based on the current literature, it remains unclear as to whether lateral acromioplasty affects clinical outcomes as a function of a reduced postoperative CSA.

LEVEL OF EVIDENCE

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

The critical shoulder angle: can it be sufficient to reflect the shoulder joint without the humeral head?

HYPOTHESIS

We hypothesized that a new method considering the humeral head would distinguish rotator cuff tears (RCTs) and osteoarthritis (OA) better than the critical shoulder angle (CSA).

METHODS

A total of 1011 patients were tested in this study and divided into 4 groups: those with RCTs (n = 493), those with OA (n = 73), those with anterior instability (n = 361), and those with adhesive capsulitis (n = 84). The CSA and new radiologic parameters including the humeral head were measured in the true anterior-to-posterior view: the Y angle connecting the lower end of the glenoid (LG), the center of the humeral head (CH), and the upper end of the glenoid (UG); the G angle connecting UG, CH, and the lateral tip of the acromion; the YG angle connecting LG, CH, and the lateral tip of the acromion; and the R angle connecting UG, LG, and CH.

RESULTS

The CSA and G angle were the largest in the RCT group (34.2° and 70.4°, respectively; P < .001) and the smallest in the OA group (29.8° and 61.7°, respectively; P < .001). The Y angle was the largest in the OA group (82.8°, P < .001). The R angle in the RCT group (52.9°) was significantly larger than that in the OA group, which was the smallest among the groups (48.0°; P < .001). The CSA was correlated with the G and YG angles in the RCT group, whereas the CSA was correlated with the Y, G, and R angles in the OA group (P < .05). The CSA showed the highest correlation with the size of RCTs (correlation coefficient = 0.138).

CONCLUSION

The Y, G, and R angles reflected the lesions of RCTs or OA. The CSA showed good correlations with the new radiologic parameters, and it had the highest correlation coefficient with the size of RCTs.

Critical shoulder angle: Acromial coverage is more relevant than glenoid inclination

It is still unknown whether glenoid inclination or lateral acromial roof extension is a more important determinant for development of rotator cuff tears (RCT) or osteoarthritis (OA) of the shoulder. It was the purpose of this study, to evaluate whether there is a potential predominance of one of these factors in pathogenesis of RCT or concentric OA. We analyzed 70 shoulders with advanced degenerative RCT and 54 shoulders with concentric OA undergoing primary shoulder arthroplasty (anatomical or reverse) using antero-posterior radiography and multiplanar computed tomography. The two groups were compared in relation to glenoid inclination, lateral acromion roof extension, acromial height, and critical shoulder angle (CSA). All measured parameters were highly significantly different between RCT and concentric OA (p < 0.001). Based on Cohen's d effect size, group differences were most distinct in lateral acromial roof extension (1.36_x-ray , 0.92_ct ) compared with acromial height (1.06_x-ray , 0.73_ct ) and glenoid inclination (0.60_x-ray , 0.61_ct ). However, no single factor showed an effect size which was as high as that of the CSA (1.63_x-ray ). Interestingly, a ratio of lateral acromion roof extension and acromial height could enhance the effect size (1.60_x-ray , 1.16_ct ) near to values of the CSA (1.63_x-ray ). In summary, lateral acromial roof extension has a greater influence in pathogenesis of degenerative RCT and concentric OA than acromial height or glenoid inclination. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Small anteroposterior inclination of the acromion is a predictor for posterior glenohumeral erosion (B2 or C)

BACKGROUND

Anatomic factors associated with static posterior translation of the humeral head with or without glenohumeral osteoarthritis are unknown. We tested the hypothesis that there is an association between glenoid wear, glenoid version, and/or anteroposterior acromial tilt.

METHODS

Ninety-nine patients with glenohumeral joint degeneration involving advanced glenoid cartilage wear and/or rotator cuff disease scheduled for anatomic or reverse total shoulder replacement underwent standardized conventional radiographic and computed tomographic shoulder imaging. Measurements included glenoid version, humeral torsion, posterior acromial slope, and critical shoulder angle. The glenoid shape was classified according to Walch et al, and the integrity of the rotator cuff was assessed.

RESULTS

Patients with glenoid type B2 or C had a median of 4° more glenoid retroversion (P = .022), a 5° less steep acromion (posterior acromial slope, 61° vs 56°; P = .004), and a higher combined score (glenoid version minus slope; odds ratio, 0.93 [95% confidence interval, 0.89-0.97]; P < .001; cutoff, -27°) than those with type A or B1. When the rotator cuff was torn, osteoarthritic changes were milder than when the cuff was intact (eg, P < .001 for supraspinatus).

CONCLUSION

The study's hypothesis that the bony anatomy of the scapula and in particular the acromion is correlated with the type of glenoid wear was confirmed. Both a more horizontal acromial orientation in the sagittal plane and increased posterior glenoid version are found in osteoarthritis of the shoulder associated with eccentric, posterior glenoid wear. Tears of the rotator cuff are significantly associated with concentric osteoarthritis of the glenoid.

Different acromial roof morphology in concentric and eccentric osteoarthritis of the shoulder: a multiplane reconstruction analysis of 105 shoulder computed tomography scans

BACKGROUND

The pathomechanisms of eccentric osteoarthritis of the shoulder remain unclear. Although there is increasing evidence of bony differences between shoulders with rotator cuff tears and osteoarthritis, analogous differences have not been identified for primary concentric and eccentric osteoarthritis. This study examined the shape and orientation of the acromial roof as a potential risk factor for the development of posterior glenoid wear.

METHODS

We analyzed computed tomography images of 105 shoulders with primary osteoarthritis. Based on the classification of Walch, 45 shoulders had concentric osteoarthritis (Walch A) and 60 shoulders were affected by eccentric osteoarthritis (Walch B; EOA). A comparison of acromial morphology was performed in a multiplanar reconstruction analysis of computed tomography scans.

RESULTS

Acromial shape: Acromial length, width, and area were not significantly different. Acromial roof orientation: The acromial roof in EOA was an average of 5° flatter (sagittal tilt; P < .01) and 5° more downward tilted (coronal tilt; P < .01). There was no difference in axial rotation (axial tilt; P = .47). Anteroposterior glenoid coverage: The glenoid in EOA was covered an average of 4° less posteriorly (P = .01) and 4° more anteriorly (P = .04). No differences were shown for overall glenoid coverage.

CONCLUSIONS

The acromial roof could play a role in the pathogenesis of EOA. Less posterior support due to a flatter acromion with less posterior glenoid coverage could contribute to static posterior subluxation of the humeral head and posterior glenoid wear. Further biomechanical investigations are needed to confirm these findings.

Acromial roof in patients with concentric osteoarthritis and massive rotator cuff tears: multiplanar analysis of 115 computed tomography scans

BACKGROUND

There is evidence for differences of scapular shape between shoulders with rotator cuff tears (RCT) and osteoarthritic shoulders (OA). This study analyzed orientation and shape of the acromion in patients with massive RCT and concentric OA (COA) in a multiplanar computed tomography (CT) analysis.

METHODS

CT scans of 70 shoulders with degenerative RCT and 45 shoulders with COA undergoing primary shoulder arthroplasty were analyzed. The 2 groups were compared in relation of (1) shape of the acromion, (2) its orientation in space, and (3) the anteroposterior glenoid coverage in relation to the scapular plane.

RESULTS

Lateral acromial roof extension was an average of 4.6 mm wider and the acromial area was an average of 156 mm² larger in RCT than in COA (P < .001). Significant differences of the lateral extension of the acromion margin were limited to the anterior two-thirds. Acromial roof orientation in RCT was average of 10.8° more "externally rotated" (axial plane: P < .001) and an average of 7.8° more tilted downward (coronal plane: P < .001) than in COA. The glenoid in RCT was an average of 5.5° (P < .001) more covered posteriorly compared with COA.

CONCLUSIONS

A more externally rotated (axial plane), more downward tilted (coronal plane), and wider posterior covering acromion was more frequent in patients with massive RCT than COA.

High-fat/high-sucrose diet-induced obesity results in joint-specific development of osteoarthritis-like degeneration in a rat model

Objectives

Metabolic syndrome and low-grade systemic inflammation are associated with knee osteoarthritis (OA), but the relationships between these factors and OA in other synovial joints are unclear. The aim of this study was to determine if a high-fat/high-sucrose (HFS) diet results in OA-like joint damage in the shoulders, knees, and hips of rats after induction of obesity, and to identify potential joint-specific risks for OA-like changes.

Methods

A total of 16 male Sprague-Dawley rats were allocated to either the diet-induced obesity group (DIO, 40% fat, 45% sucrose, n = 9) or a chow control diet (n = 7) for 12 weeks. At sacrifice, histological assessments of the shoulder, hip, and knee joints were performed. Serum inflammatory mediators and body composition were also evaluated. The total Mankin score for each animal was assessed by adding together the individual Modified Mankin scores across all three joints. Linear regression modelling was conducted to evaluate predictive relationships between serum mediators and total joint damage.

Results

The HFS diet, in the absence of trauma, resulted in increased joint damage in the shoulder and knee joints of rats. Hip joint damage, however, was not significantly affected by DIO, consistent with findings in human studies. The total Mankin score was increased in DIO animals compared with the chow group, and was associated with percentage of body fat. Positive significant predictive relationships for total Mankin score were found between body fat and two serum mediators (interleukin 1 alpha (IL-1α) and vascular endothelial growth factor (VEGF)).

Conclusion

Systemic inflammatory alterations from DIO in this model system may result in a higher risk for development of knee, shoulder, and multi-joint damage with a HFS diet.Cite this article: K. H. Collins, D. A. Hart, R. A. Seerattan, R. A. Reimer, W. Herzog. High-fat/high-sucrose diet-induced obesity results in joint-specific development of osteoarthritis-like degeneration in a rat model. Bone Joint Res 2018;7:274-281. DOI: 10.1302/2046-3758.74.BJR-2017-0201.R2.

Glenoid component loosening associated with increased critical shoulder angle at midterm follow-up

BACKGROUND

Glenoid component loosening is a common failure mode of total shoulder arthroplasty (TSA). A larger critical shoulder angle (CSA) may cause superior glenoid component loading and more rapid component loosening. The purpose of this study was to define the relationship between the CSA and glenoid component loosening in midterm follow-up after TSA.

METHODS

We conducted a retrospective study of 61 primary TSAs for osteoarthritis with an average follow-up of 5.0 ± 2.2 years without surgical revision. Standard true anteroposterior radiographs postoperatively and at longest follow-up were graded in a blinded and repetitive nature for pegged glenoid radiolucent lines and measured for the CSA. An "at-risk" glenoid was defined as grade 3 or higher lucency.

RESULTS

The average CSA was 32° ± 5°, median midterm lucency grade was 2 (range, 0-5), and median progression of lucency grade was 1 (range, -1 to 4). At midterm follow-up, 20% of TSAs were grade 3 or higher mean glenoid lucency, with an average CSA of 36°. There was a statistically significant correlation between CSA and both glenoid lucency grade (odds ratio, 1.20 per degree CSA) and progression of lucency grade (odds ratio, 1.24). An increase in CSA of 10° was associated with a 6.2-fold increased odds of having an at-risk glenoid.

CONCLUSION

This study identifies the CSA as a risk factor for glenoid component loosening after TSA. Our findings suggest that the CSA may be a modifiable factor during surgery to improve glenoid component outcomes.

The critical shoulder angle is associated with osteoarthritis in the shoulder but not rotator cuff tears: a retrospective case-control study

BACKGROUND

In 2013 Moor et al introduced the concept of the critical shoulder angle (CSA) and suggested that an abnormal CSA was a leading factor in development of rotator cuff tear (RCT) and osteoarthritis (OA) of the shoulder. This study assessed whether the CSA was associated with RCT and OA and tested the inter- and intrarater reliability of the CSA when measuring RCT and OA.

MATERIALS AND METHODS

The study was performed as a retrospective case-control study. The cases comprised 2 groups: 97 patients with RCT and 87 patients with OA. The controls were matched 3:1, by age and sex, from a population of 795 patients with humeral fractures. The CSA was measured as described by Moor et al. Analysis of the relation with CSA for RCT and OA was done by logistic regression. Models were fitted separately for RCT and OA and used the controls matched to the respective cases. Inter- and intrarater reliability was determined by measuring the intraclass correlation coefficient and minimal detectable change.

RESULTS

The mean CSA was 33.9° in the RCT group and 33.6° in the matched control group. The odds ratio for developing RCT for people with a CSA above 35° was 1.12 (P = .63). The mean CSA in the OA group was 31.1° and in the matched control group 33.3°. The odds ratio for developing OA for people with a CSA below 30° was 2.25 (P = .002). The CSA measurements showed strong intra- and inter-rater reliability, with intraclass correlation coefficient values above 0.92 and minimal detectable change values below 0.4°.

CONCLUSIONS

This study did not find any association between CSA and RCT but did show association between CSA and OA, with a 2.25 odds ratio of developing OA given the patient had a CSA below 30°. The results do not support the suggested praxis of shaving away the lateral border of the acromion to make the CSA smaller because it might increase the risk of developing OA without decreasing the risk of developing RCT. The CSA measurements showed excellent intra- and inter-rater reliability.

Critical shoulder angle combined with age predict five shoulder pathologies: a retrospective analysis of 1000 cases

BACKGROUND

Acromial morphology has previously been defined as a risk factor for some shoulder pathologies. Yet, study results are inconclusive and not all major shoulder diseases have been sufficiently investigated. Thus, the aim of the present study was to analyze predictive value of three radiological parameters including the critical shoulder angle, acromion index, and lateral acromion angle in relationship to symptomatic patients with either cuff tear arthropathy, glenohumeral osteoarthritis, rotator cuff tear, impingement, and tendinitis calcarea.

METHODS

A total of 1000 patients' standardized true-anteroposterior radiographs were retrospectively assessed. Receiver-operating curve analyses and multinomial logistic regression were used to examine the association between shoulder pathologies and acromion morphology. The prediction model was derived from a development cohort and applied to a validation cohort. Prediction model's performance was statistically evaluated.

RESULTS

The majority of radiological measurements were significantly different between shoulder pathologies, but the critical shoulder angle was an overall better parameter to predict and distinguish between the different pathologies than the acromion index or lateral acromion angle. Typical critical shoulder angle-age patterns for the different shoulder pathologies could be detected. Patients diagnosed with rotator cuff tears had the highest, whereas patients with osteoarthritis had the lowest critical shoulder angle. The youngest patients were in the tendinitis calcarea and the oldest in the cuff tear arthropathy group.

CONCLUSIONS

The present study showed that critical shoulder angle and age, two easily assessable variables, adequately predict different shoulder pathologies in patients with shoulder complaints.

Is There an Association Between the "Critical Shoulder Angle" and Clinical Outcome After Rotator Cuff Repair?

BACKGROUND

Variations in scapular morphology have been associated with the development of atraumatic rotator cuff tears (RCTs). The critical shoulder angle (CSA) accounts for both glenoid inclination and lateral extension of the acromion. The impact of the CSA on outcomes after rotator cuff repair (RCR) has not been investigated previously.

HYPOTHESIS

Our hypothesis was that individuals with smaller CSAs will have better patient-reported outcome scores over time compared with those with larger CSAs. Theoretically, a smaller CSA minimizes the biomechanical forces favoring superior translation of the humeral head, which may be advantageous after RCR. This is the first study to examine the relationship between the CSA and clinical outcomes after RCR.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Fifty-three patients (mean age, 61 years) with atraumatic full-thickness RCTs who underwent arthroscopic RCR were prospectively evaluated. Demographic data as well as the Western Ontario Rotator Cuff Index (WORC) score, American Shoulder and Elbow Surgeons (ASES) score, and a visual analog scale (VAS) for pain were prospectively collected at various time points up to 24 months postoperatively. Statistical analysis included longitudinal multilevel regression modeling to investigate the association between the CSA and the WORC, ASES, and VAS scores.

RESULTS

The overall clinical outcome, as measured by the WORC, ASES, and VAS, improved significantly (P < .0001). Controlling for demographic and clinical characteristics, a multilevel regression analysis demonstrated that the CSA was not a significant independent predictor for change in WORC (P = .581), ASES (P = .458), or VAS (P = .859) scores at 24 months after arthroscopic RCR. Interobserver and intraobserver reliability for CSA measurements resulted in interclass correlation coefficients of 0.986 and 0.982, respectively (P < .001), indicating excellent agreement.

CONCLUSION

The CSA did not appear to be a significant predictor of patient-reported outcomes after arthroscopic repair of atraumatic full-thickness RCTs.

Effects of anterior offsetting of humeral head component in posteriorly unstable total shoulder arthroplasty: Finite element modeling of cadaver specimens

A novel technique of "anterior offsetting" of the humeral head component to address posterior instability in total shoulder arthroplasty has been proposed, and its biomechanical benefits have been previously demonstrated experimentally. The present study sought to characterize the changes in joint mechanics associated with anterior offsetting with various amounts of glenoid retroversion using cadaver specimen-specific 3-dimensional finite element models. Specimen-specific computational finite element models were developed through importing digitized locations of six musculotendinous units of the rotator cuff and deltoid muscles based off three cadaveric shoulder specimens implanted with total shoulder arthroplasty in either anatomic or anterior humeral head offset. Additional glenoid retroversion angles (0°, 10°, 20°, and 30°) other than each specimen׳s actual retroversion were modeled. Contact area, contact force, peak pressure, center of pressure, and humeral head displacement were calculated at each offset and retroversion for statistical analysis. Anterior offsetting was associated with significant anterior shift of center of pressure and humeral head displacement upon muscle loading (p<0.05). Although statistically insignificant, anterior offsetting was associated with increased contact area and decreased peak pressure (p > 0.05). All study variables showed significant differences when compared between the 4 different glenoid retroversion angles (p < 0.05) except for total force (p < 0.05). The study finding suggests that the anterior offsetting technique may contribute to joint stability in posteriorly unstable shoulder arthroplasty and may reduce eccentric loading on glenoid components although the long term clinical results are yet to be investigated in future.

The morphometric anatomy of the delto-fulcral triangle: A 3D CT-based reconstruction study

This study introduced the new delto-fulcral triangle (DFT), the first anatomical model of its kind. As seen from the orthopaedician's supraspinatus-outlet view, the antero-superior point of the coracoid process along with the lateral- and posterior-most acromial landmarks form the boundaries of the DFT. Since these osseous scapular landmarks accounted for both dynamic and static stabilisers of the glenohumeral joint, knowledge of the anatomical features of the DFT may prove beneficial to the orthopaedic surgeon. This study thus aimed to investigate the morphometry of the new DFT. The bony surfaces of one-hundred and sixty-nine (n = 169) normal and pathological (Omarthrosis and Cuff-Tear Arthropathy) shoulders from the hospital's CT scan database were reconstructed (Mimics^®: Materialise, Leuven, Belgium). Statistical significance was observed between all three groups for Side 2 (LACPF: distance between most lateral and most posterior points of the acromion) and angles α (angle between sides 1 and 3) and β (angle between sides 1 and 2) of the DFT. It was postulated that although pathological cases present with a smaller lateral acromial distance (LACPF), their lateral acromion landmark is more posteriorly placed from the scapular plane than that of a normal case. As the aspects of the morphometric anatomy of the DFT presented with levels of statistical significance, it may provide a means to evaluate the anatomy of normal and pathological cases. Additionally, the three osseous scapular landmarks that create the DFT are clearly visualised and palpable, therefore they are easily reproducible from both X-ray images and CT scans.