The scapular glenopolar angle: standard values and side differences

Morphometric Analysis of Glenopolar Angle of the Scapula in Indian Population

BACKGROUND

The glenopolar angle (GPA), usually ranges from 30° to 45°. GPA measures the tilt of the plane of the glenoid cavity in relation to the axis of the body of the scapula passing from the superior pole of the glenoid cavity to the inferior angle of the scapula. It is essential to assess the results of surgeries for dislocated shoulders. Worse long-term outcomes can arise from glenoid misalignment in scapular neck fractures. When evaluating prognosis and planning therapy for shoulder injuries including scapular fractures, GPA assessment is essential. Still, there is a dearth of data on the normal range of GPA and its contributing elements, which calls for more study. The purpose of this study is to determine typical GPA values by utilizing radiographs and a sizable sample of scapular bone specimens.

METHODS

In this study, the GPA was assessed in 50 chest radiographs of anteroposterior (AP) view and Neer's view of individuals as well as 100 dried scapulae of any gender. The mean GPA obtained using the various methods was then statistically compared.

FINDINGS

All scapulae had an average GPA of 42.6°. Twenty-nine scapulae had GPA observations higher than 45°, with an average of 47.2°. Twenty-seven scapulae had GPA measurements below 40°, averaging 37.3°. Right-sided 62 scapulae with an average GPA of 43.1° were present. Thirty-eight of left-side scapulae had a GPA of 41.7° on average. It was determined that the 1.6° mean difference in GPA between the two groups was not statistically significant. The Kolmogorov-Smirnov test verified that the GPA data had a normal distribution. The homogeneity of variances across various measuring techniques was confirmed using Levene's test. The average GPA measured using the dry scapula approach was 42.6°, the average GPA measured using the AP view was 39.8°, and the average GPA measured using the Neer I view was 42.3°. The GPA means from these three approaches differed considerably (p=0.0014) according to a one-way Analysis of Variance (ANOVA). Fisher's least significant difference post hoc testing showed that the scapular bone specimens and the Neer I view revealed significantly higher GPA values than AP shoulder radiographs. The GPA values obtained from the osteological group and the Neer I perspective had a mean difference of 0.21°, which was practically identical and suggested that there was no statistically significant difference between these approaches.

IN SUMMARY

In order to diagnose and treat a variety of shoulder joint diseases, this study estimates the normal values of scapular GPA. Furthermore, it offers support for improved implant design in the context of Indian shoulder joint replacement and repair. Using every measurement technique, the GPA values on the right and left sides did not differ significantly. GPA results from various measuring methods varied significantly, which emphasizes the significance of methodological consistency in clinical and research settings.

Quadruple Disruption of Superior Shoulder Suspensory Complex With Proximal Humerus Open Fracture-Dislocation: A Case Report

CASE

A 34-year-old man was a restrained passenger involved in a high-speed rollover motor vehicle crash. The patient sustained a type 5 AC joint separation, severely comminuted intra-articular glenoid fracture with extension to the coracoid process base, displaced open scapular body fracture, a posterior shoulder dislocation of the glenohumeral joint, and a 2-part proximal humerus fracture.

CONCLUSION

To our knowledge, this is the first report describing this injury pattern involving the superior shoulder suspensory complex with an associated open proximal humerus fracture-dislocation.

Scapular fractures osteosynthesis via Judet's posterior approach: clinical and radiographic results

PURPOSE

Scapular fractures are uncommon and mainly treated nonoperatively. Judet's posterior approach allows access to the fracture site through the infraspinatus fossa and may be a technical option when ORIF is decided. The aims of this study were to determine clinical and radiographic outcomes of patients who underwent scapular body and/or glenoid fractures fixation via Judet's posterior approach.

METHODS

We conducted a retrospective single-centre study, and all patients admitted for scapular fracture who underwent osteosynthesis via Judet's approach between January 2014 and September 2021 were included. At a minimum follow-up of one year, clinical outcomes were analyzed through subjective shoulder value (SSV) and Constant-Murley score (CMS). Strength in external rotation was measured in adduction and in 90° abduction and compared to healthy side. Radiographic analysis evaluated postoperative fracture reduction on CT scan and glenohumeral osteoarthritis according to Samilson's classification at last follow-up.

RESULTS

Twenty-one patients were included with a mean follow-up of 44.9 months. Mean SSV, CMS, and adjusted CMS were 73.8% ± 21.0, 65.8 points ± 19.5, and 72.8% ± 20.8, respectively. Strength in external rotation in adduction of the affected shoulder showed significant impairment when compared with the contralateral side (respectively 7.79 kg ± 4.29 and 12.0 kg ± 3.84, p = 0.02). All fractures healed uneventfully, but five patients (23.8%) required early revision surgery for intra-articular screws in three. Intra-articular gap measure decreased from 3.75 mm ± 1.93 in preoperative to 0.59 mm ± 0.97 after ORIF. The rate of arthritis was 15% at last follow-up.

CONCLUSION

Patients who underwent scapular fracture osteosynthesis via Judet's posterior approach exhibited satisfactory but incomplete recovery of the affected shoulder as evidenced by functional scores and external rotation strength measurements at a mean follow-up of 44.9 months. Because of the risk of intra-articular screws, postoperative CT scan is mandatory.

Three-dimensional morphometric analysis of glenoid in the Indonesian population and its clinical significance

Background

Understanding glenoid morphometry is important in shoulder prosthetic replacement surgery. In total and reverse shoulder arthroplasty, the size of the implants has to be determined according to the morphometry of the shoulder. However, there has been no known data on glenoid morphometry in the Indonesian population.

Methods

Seventy-four computed tomography scans of asymptomatic shoulders were obtained from the medical databases of a third referral hospital in Jakarta. Mimics Research 21.0 was used to reconstruct 3D models of the scapula from the DICOM files. The morphometry parameters included were glenoid fossa height (GFH), maximum glenoid fossa width (MGW), glenoid width at center of the glenoid fossa (CGW), vertical distance between maximum width and center (VDMC), glenoid version angle (GVA), glenoid inclination (GI), glenopolar angle (GPA), glenoid vault depth (GVD), coracoid length (CL), coracoid midpoint length (CML), coracoid tip height (CTH) and width (CTW), and coracoid midpoint height (CMH) and width (CMW).

Results

Our study found the average Indonesian GFH was 30.24 mm, the MGW was 24.03 mm, the CGW was 22.46 mm, the VDMC was 3.67 mm, the GPA was 42.76°, the GVD 18.8 mm, the GVA was 2.39° retroverted, the GI was 3.15° superiorly inclined, the CL was 37.76 mm, the CML was 18.89 mm, the CTW was 13.31 mm, the CTH was 8.52 mm, the CMW was 14.21 mm, and the CMH was 10.46 mm. All parameters except VDMC, GVA, and GI showed significant differences between male and female subjects Meanwhile, there was no significant difference in dimension and orientation of the glenoid and coracoid between the right and left shoulder.

Conclusion

Our study showed a lower value of MGW, GFH, and GVD compared to other Asian ethnicities. These results may be helpful in designing smaller prostheses suitable for Indonesian glenoids.

Circumflex arterial sulcus of the scapula (sulcus arteriae circumflexae scapulae): its anatomy and clinical relevance

INTRODUCTION

The circumflex scapular artery (CSA) has been described in detail in the literature, but the groove, i.e., the circumflex sulcus (CFS), formed by the artery on the lateral pillar of the scapula has been completely neglected. The aim of the present study was to describe the variability and anatomy of the CFS.

MATERIALS AND METHODS

The study was based on the examination of 103 pairs of dry bone specimens of adult scapulae, i.e., 206 specimens, including 92 (46 pairs) male and 114 (57 pairs) female specimens. In the first step, quantitative criteria were defined for assessment of the CFS presence and type. Subsequently, statistical analysis of the obtained data was performed.

RESULTS

The study revealed considerable variability of the arterial groove, which was well developed in 33% (type A), shallow in 40% (type B), and absent in 27% (type C) of cases. The mean distance between CFS and the infraglenoid tubercle was 3.3 cm CI_0.95 (3.1-3.3), which corresponds to the proximal third of the lateral border of the scapula.

CONCLUSION

The study has confirmed variability of the arterial groove (CFS) and its localization in relation to the inferior glenoid rim. The findings are clinically important, particularly in relation to the Judet approach to scapular fractures (localization of the CSA course).

Clinical relevance of augmented statistical shape model of the scapula in the glenoid region

OBJECTIVE

To illustrate (a) whether a statistical shape model (SSM) augmented with anatomical landmark set(s) performs better fitting and provides improved clinical relevance over non-augmented SSM and (b) which anatomical landmark set provides the best augmentation strategy for predicting the glenoid region of the scapula.

METHODS

Scapula SSM was built using 27 dry bone CT scans and augmented with three anatomical landmark sets (16 landmarks each) resulting in three augmented SSMs (aSSM_proposed, aSSM_set1, aSSM_set2). The non-augmented and three augmented SSMs were then used in a non-rigid registration (regression) algorithm to fit to six external scapular shapes. The prediction error by each type of SSM was evaluated in the glenoid region for the goodness of fit (mean error, root mean square error, Hausdorff distance and Dice similarity coefficient) and for four anatomical angles (critical shoulder angle, lateral acromion angle, glenoid inclination, glenopoar angle).

RESULTS

Inter- and intra-observer reliability for landmark selection was moderate to excellent (ICC>0.74). Prediction error was significantly lower for SSM_{non-augmented} for mean (0.9 mm) and root mean square (1.15 mm) distances. Dice coefficient was significantly higher (0.78) for aSSM_proposed compared to all other SSM types. Prediction error for anatomical angles was lowest using the aSSM_proposed for critical shoulder angle (3.4°), glenoid inclination (2.6°), and lateral acromion angle (3.2°).

CONCLUSION AND SIGNIFICANCE

The conventional SSM robustness criteria or better goodness of fit do not guarantee improved anatomical angle accuracy which may be crucial for certain clinical applications in pre-surgical planning. This study provides insights into how SSM augmented with region-specific anatomical landmarks can provide improved clinical relevance.

Does the position of the scapula in relation to the glenopolar angle change the preferred treatment of extra-articular fractures?

OBJECTIVE

To analyse the glenopolar angle (GPA) at different inclinations of the scapula using 3D CT, to test the hypothesis that the result could change the indication from conservative treatment to surgery.

MATERIALS AND METHODS

Analysis of 30 3D CT images of patients' scapulae, measuring the GPA. The GPA was measured with scapulae at 0^° and at 20^° and 30^° of internal and external rotation. Angles were compared by age, sex and examiner for the different angles of rotation of the scapulae.

RESULTS

The GPA of scapulae in rotation tended to be smaller than the GPA without rotation, and the larger the degree of rotation, the more the angle was underestimated. Additionally, for the same degree of rotation, internal rotation was associated with greater underestimation of the GPA than external rotation. Two different examiners achieved an excellent level of agreement between angle measurements. The GPA with the scapula at 0^° was significantly higher among elderly patients. The variation in GPA with the scapula in rotation (20^° and 30^°) in relation to the GPA without rotation was significantly greater for female patients.

CONCLUSIONS

As the rotation of the scapula was displaced from the scapula in the coronal position (GPA 0^°), both in internal rotation and in external rotation, the GPA reduced. Therefore, rotational displacement may lead to an error in GPA measurement, resulting in incorrect indication of treatment. It is recommended that whenever possible, GPA measurements should be taken in neutral rotation, with the scapula in a neutral position at 0^°.

How to deal with a glenoid fracture

The glenoid fossa is involved in approximately 10% of all scapular fractures.Glenoid fossa incongruity is surprisingly well tolerated.Surgery is recommended when 20% or more of the anterior glenoid fossa is involved.Glenoid rim fractures often lead to chronic shoulder instability.Unstable glenoid neck fractures need surgical treatment and stable fractures can be treated conservatively.CT examination with 3D reformations of the glenoid fossa has improved insight into fracture morphology and fracture patterns and is very helpful for clinical decision makers. Cite this article: EFORT Open Rev 2017;2. DOI: 10.1302/2058-5241.2.160082. Originally published online at www.efortopenreviews.org.

Comparison of measurements of the glenopolar angle in 3D CT reconstructions of the scapula and 2D plain radiographic views

AIMS

The aim of this study was to analyse the effect of altered viewing perspectives on the measurement of the glenopolar angle (GPA) and the differences between these measurements made on 3D CT reconstructions and anteroposterior (AP) scapular view radiographs.

MATERIALS AND METHODS

The influence of the viewing perspective on the GPA was assessed, as were the differences in the measurements of the GPA between 3D CT reconstructions and AP scapular view radiographs in 68 cadaveric scapulae.

RESULTS

The median GPA in 3D reconstructions and AP scapular views were 42.7° (95% confidence intervals (CI), 42.0° to 43.5°) and 41.3° (95% CI 40.4° to 42.0°) respectively (p < 0.001). All but five of 20 malpositions demonstrated a significant difference in GPA compared with the respective AP scapular view (p ≤ 0.005). The GPA was most susceptible to malposition in retroversion/anteversion. Inter- and intra-observer reliability for all measurements of the GPA was excellent for 3D CT reconstructions (intraclass correlation (ICC) 0.93 (95% CI 0.87 to 0.96) and 0.94 (95% CI 0.89 to 0.97), respectively) and higher than on AP scapular radiographs (p < 0.001). The intra- and inter-observer reliability was excellent in AP scapular views and malpositions in extension/flexion (ICC ≥ 0.84) but tended to decrease with increasing viewing angle in retroversion/anteversion.

CONCLUSION

These data suggest that 3D reconstructions are more reproducible than AP scapular radiographs in the assessment of the GPA and should be used to compare data in different studies, to predict outcome, define malunion, and act as an indication for surgery in patients with a scapular fracture. Cite this article: Bone Joint J 2016;98-B:1510-16.

Is radiograph glenopolar angle accurate for extraarticular scapular neck fractures?

BACKGROUND

Plain radiographs still play a role in management of extraarticular scapular neck fractures. Glenopolar angle (GPA) is one of the radiograph measurements that is used to determine the necessity for surgery. Our aim was to establish reliability of GPA on plain radiograph in patients with extraarticular scapular neck fractures.

METHODS

We performed a multicentre retrospective study including all patients with extraarticular scapular neck fractures with available imaging between 2006 and 2012. We excluded intra-articular glenoid fractures, scapular blade fractures, acromion fractures, and scapular spine fractures. We compared GPA on plain radiograph with three dimensional computed tomography (3D CT) measurement, as well as contribution of radiograph rotational error, glenoid inclination, and medial shortening of glenoid fragment towards GPA measurement.

RESULTS

One hundred patients met the inclusion criteria. The mean difference between the GPA measurements on radiographs and 3D CT was 6.1±0.85° (95% confidence interval) as an absolute value. In terms of contribution to GPA values, GPA changed by one degree with ten degrees of radiograph rotational error, three degrees of glenoid inclination, and three millimetres of glenoid fragment medial shortening.

CONCLUSION

Plain radiograph can provide a clinician with a reasonable estimation of the GPA. Glenoid inclination has a greater influence on GPA compared to medial shortening.