Scapula revisited: new features identified and denoted by terms using consensus method of Delphi and taxonomy panel to be implemented in radiologic and surgical practice

Analysis and optimization of plate fixation fitness in acromion fracture reduction by calculating dry scapulae and x-rays acromion curvature

BACKGROUND

The acromion projects laterally in a curving orientation. When a fracture of the acromion occurs, despite being rare, matching the best-fit fixation plate is challenging due to few options and limited availability of fixation plate types. Alternative fixation methods can carry risk of nonunion complications.

PURPOSE

The objective of this study was to investigate the morphological curvature pattern of the acromion to assess the level of the fixation plates fitness and provide the suitable imaging modalities for evaluating the acromion curvature.

BASIC PROCEDURES

The correlation between the acromion curvature and five fixation plates were calculated and their fitness level was evaluated statistically. The curvature of acromion and the five available fixation plates were photographed and assessed digitally by software (FIJI ImageJ and Microsoft Excel). The method entails plotting seven points along the curving surface and margins of the acromion, while the Excel Solver function calculates the regression, ultimately giving curvature values. First, the acromion parameters were studied on 180 paired healthy dry scapulae. Then, the acromion curvature values were compared to the fixation plates curvatures. Likewise, the acromion curvature was assessed as applicable on 153 (100 AP- views, 50 Y- views, and 3 superior-views) retrospective plain X-rays and 40 3D-CT scapula reconstructions of healthy acromia.

MAIN FINDINGS

The mean length of the acromion was 48.70 ± 5.29 mm, mean thickness was 8.51 ± 1.67 mm, and mean width was 25.97 ± 5.97 mm. The calculated values of the mean curvatures were 0.050 ± 0.015 mm-1 for the mean acromion surface, 0.042 ± 0.027 mm-1 for the internal margin, and 0.055 ± 0.010 mm-1 for the external margin. The curved geometry of the acromion was plotted on a graph giving a spectrum of curvature patterns with distribution values revealing fixation plates fitness represented by area under the curve with frequencies of 4.32 % for the acromion-specific fixation plate, 14.28 % for the large clavicle fixation plate, 0.26 % for the small clavicle fixation plate, 53.38 % for the flexible universal fixation plate, and none for the rigid universal fixation plate.

PRINCIPAL CONCLUSIONS

Approximately 27.76 % of the acromion surface curvatures distribution does not overlap with any of our measured fixation plates. Evaluating the acromion surface curvature was possible on plain X-rays in the Y-view only.

Muscles variations with topographical relationship to the suprascapular notch and its potential arthroscopic feasibility

PURPOSE

This study provides an insight on the extent of muscular variability at the suprascapular notch and elaborates on its anatomical interference in suprascapular nerve arthroscopic decompression procedures.

METHODS

The suprascapular notch was dissected and its muscular topography was observed in 115 cadaveric specimens. High resolution imaging of the suprascapular notch was captured by a handheld digital microscope (Q-scope). The supraspinatus and subscapularis muscles were traced as they course at the suprascapular notch vicinity. The omohyoid muscle attachment onto the suprascapular ligament was measured. A scoping review and meta-analysis were done to investigate the observed rare muscular variants.

RESULTS

In 3.48%, the suprascapular notch anterior surface was fully covered by the subscapularis muscle. The omohyoid muscle inserted onto the suprascapular ligament in 31.25% and extended up to 3/4th of the suprascapular ligament length in 2.61%. Two rare variant muscles were encountered: subclavius posticus muscle and a newly reported "coracoscapularis muscle".

CONCLUSIONS

Four categories of muscles with topographical relationship to the suprascapular notch and its arthroscopic feasibility have been classified: (1) constant muscles not intervening with the suprascapular notch space - supraspinatus muscle; (2) constant muscles with variable positions that can intervene with the suprascapular notch space - subscapularis muscle; (3) constant muscles with variable positions that can intervene with the surgical approach - omohyoid muscle; (4) variable muscles intervening with the suprascapular notch space and surgical approach - subclavius posticus and coracoscapularis muscles. This study elucidates the necessity to assess/secure the omohyoid muscle attachment onto the suprascapular ligament in suprascapular nerve decompression ligamentectomy.

LEVEL OF EVIDENCE

V Basic Science Research.

Neurodynamic testing of the suprascapular nerve: An observational cadaveric study

BACKGROUND

Suprascapular neurodynamic tests are used to clinically test for suprascapular nerve mechanosensitivity. Various tests described in the literature are proposed to induce suprascapular nerve mechanical strain but their potential effects on nerve strain have not been established.

METHODS

This observational cadaveric study used biomechanical measurements to evaluate and compare the strain undergone by the suprascapular nerve during five different neurodynamic positions: (1) Cervical contralateral rotation and scapular retraction; (2) Cervical contralateral sidebending + shoulder girdle depression; (3) Shoulder girdle depression, retraction, posterior tilt and downward rotation; (4) Position 3 + contralateral cervical sidebending; and (5) Scapular protraction + Cervical contralateral sidebending (protraction sidebending test). Suprascapular nerve strains were measured using two differential transducers, one placed before the nerve entry by the suprascapular notch (prescapular portion) and the second after the spine of the scapula in the infraspinal fossa (scapular portion).

FINDINGS

Prescapular portion: all 5 positions induced a mean strain increase of 22.70 % (95 %CI 17.14, 28.26) with no significant differences between positions (p > 0.05). Scapular portion: the protraction sidebending test provoked the highest strain increase of 8.99 % (95 %CI 6.83, 11.15), significantly greater than the other positions (p < 0.05).

INTERPRETATION

All 5 positions increased suprascapular nerve strain of the prescapular portion of the suprascapular nerve. The protraction sidebending test induced the highest strain of the scapular portion of the nerve. As it is likely to influence both portions of the suprascapular nerve, the protraction sidebending test is the most suitable neurodynamic test to test for suprascapular heightened mechanosensitivity.

Multiple scapula defects or foramina or both?

The current bone report describes multiple openings identified in a dried scapula of a subject of unknown age and gender. Multiple openings (twelve) were identified in the subscapular fossa and were apparent at the infraspinatus fossa. These openings coexisted with a suprascapular foramen and an osteophyte at the inferomedial border of the foramen. In the current literature, two uncommon variants of the scapula were described: foramina and defects. It is still unclear how these two structures are differentiating. Both of them are results of abnormal ossification of the scapula. Clinicians should be aware of these variants because they may lead to misdiagnosis of malignancies, while the variants are benign entities.

Anatomical Variations in Morphometric Measurements of the Coracoid Process in a Cross Section of the Sudanese Population: Evaluation Using Chest Computed Tomography

Introduction The coracoid process is integral to the functionality of the scapula, serving as a crucial attachment point for several muscles involved in shoulder movement and stability. In pathologies and fractures of the coracoid process, understanding the morphometric variations is essential for devising optimal surgical strategies. Given the substantial lack of relevant data, this study aimed to analyze the morphometric variations in the dimensions of the coracoid process among the Sudanese population and evaluate the differences in the measurements in relation to gender. Methods The study was performed on 100 images of human scapulae (50 males and 50 females). The radiographs and reports were acquired from the Radiology Department at Almoalim Medical City, Khartoum, Sudan. CT scan images were uploaded to medical imaging software (PaxeraViewer version 1.0.1.9, PaxeraHealth, Newton, MA, USA). Quantitative measurements of linear parameters were calculated via this software, and data was analyzed using SPSS Statistics version 23 (IBM Corp. Released 2015. IBM SPSS Statistics for Windows, Version 23.0. Armonk, NY: IBM Corp.). Results Our study revealed that the mean measurements of the coracoid process dimensions were as follows: the length 39 ± 2.7 mm, the tip thickness 10.8 ± 1.8 mm, the base height 13 ± 1.1 mm, and the base width 22.2 ± 1.6 mm. Gender-based comparisons showed a trend towards larger parameters in males compared to females. Significant variations in the length (p = 0.03) and base height (p = 0.002) of the coracoid process were noted. Conclusion This study demonstrated variations in coracoid process dimensions among the Sudanese population, emphasizing gender influence. Moreover, comparisons to earlier research highlighted discrepancies across different ethnicities. Further investigation with a greater number of cases from a prospective viewpoint is needed for more compound insight into this issue.

Anatomical analysis of the motor endplate zones of the suprascapular nerve to the infraspinatus muscle and its clinical significance in managing pain disorder

Myofascial pain syndrome caused by myofascial trigger points is a musculoskeletal disorder commonly encountered in clinical practice. The infraspinatus muscle is the region most frequently involved in the myofascial pain syndrome in the scapular region. The characteristics of the myofascial trigger points are that they can be found constantly in the motor endplate zone. However, localizing myofascial trigger points within the motor endplate zone and establishing an accurate injection site of the infraspinatus muscle has been challenging because the anatomical position of the motor endplate zone of the infraspinatus muscle is yet to be described. Therefore, this cadaveric study aimed to scrutinize the motor endplate zone of the infraspinatus muscle, propose potential myofascial trigger points within the muscle, and recommend therapeutic injection sites. Twenty specimens of the infraspinatus muscle for nerve staining and 10 fresh frozen cadavers for evaluation of the injection were used in this study. The number of nerve branches penetrating the infraspinatus muscle and their entry locations were analyzed and photographed. Modified Sihler's staining was performed to examine the motor endplate regions of the infraspinatus muscle. The nerve entry points were mostly observed in the center of the muscle belly. The motor endplate was distributed equally throughout the infraspinatus muscle, but the motor endplate zone was primarily identified in the B area, which is approximately 20-40% proximal to the infraspinatus muscle. The second-most common occurrence of the motor endplate zone was observed in the center of the muscle. These detailed anatomical data would be very helpful in predicting potential pain sites and establishing safe and effective injection treatment using botulinum neurotoxin, steroids, or lidocaine to alleviate the pain disorder of the infraspinatus muscle.

Prevalence and anatomy of the anomalous subclavius posticus muscle and its clinical implications with emphasis in neurogenic thoracic outlet syndrome: Scoping review and meta-analysis

BACKGROUND

The subclavius muscle runs underneath the clavicle. However, there have been a few reports of a duplicated subclavius muscle which is commonly referred to as subclavius posticus muscle due to its orientation being posterior to the proper subclavius muscle. Its occurrence seems to potentially create a narrowing interval at the superior thoracic aperture as it crosses over the brachial plexus. It might also have functional influence on the shoulder girdle.

PURPOSE

To provide comprehensive gross anatomy description of the variant "subclavius posticus muscle" and to investigate its reported clinical implications with emphasis on its involvement in causing brachial plexus compression.

BASIC PROCEDURES

A scoping review with meta-analysis of the gross anatomy of the subclavius posticus muscle was conducted along with investigating its correlation to the thoracic outlet syndrome. Forty-seven articles were pooled through two rounds of the selection process. The relevant information was extracted and meta-analyzed.

MAIN FINDINGS

The scoping review and meta-analysis of the 47 articles revealed a total prevalence of 11/2069 (4.9%); 10/1369 (5.1%) in cadaveric studies, and 1/700 (5.0%) in MRI studies. The subclavius posticus muscle is a short triangular muscle with an average length of 12 cm and an average width of 1 cm. It originates from the sternal end of the first rib in most cases with reported variants of one case originating from the costoclavicular ligament and one case where it was fused with the proper subclavius muscle. Its insertion is more variable: on the superior border of the scapula with variable length in 71.35%, on the coracoid process of the scapula in 25.42%, and on the clavicle in 0.90%. The subclavian nerve seems to be the dominant nerve supply with a 57.6% prevalence, while 25.8% are innervated by the suprascapular nerve. Other reported nerves were the nerve to the myolohyoid (4.5%), accessory phrenic nerve (4.5%), and a direct branch from the brachial plexus (2.0%). The blood supply was reported (only once) to be from the suprascapular artery. However, the venous drainage was not established at all.

PRINCIPAL CONCLUSIONS

The subclavius posticus muscle is a variant muscle occurring with a reported overall prevalence of 4.9%. It can compress the brachial plexus as it runs across at the space of the superior thoracic aperture with exquisite contact, and this can lead to a neurogenic thoracic outlet syndrome. It also can be involved in the vascular thoracic outlet syndrome. Lastly, it is important not to omit its potential influence in shoulder joint instability to some extent.

Topographical study of scapular foramina and scapular nutrient foramina in dried skeletons

PURPOSE

The aim of our study is to study the prevalence and anatomy of scapular foramina (SF) and scapular nutrient foramina (SNF) in dried skeletons from the Northeastern Thai population.

METHODS

A total of 150 dried scapulae were investigated. Both SF and SNF were identified using a metal wire with a diameter of 0.36 mm. The number, locations, lengths, and diameters of SF were recorded. Subsequently, SNF were identified using the same metal wire. Their number and locations were recorded. Two observers performed the evaluations and measurements.

RESULTS

SF were present in 78.0% of scapulae. They could have up to five openings. Eighteen types were found. On average they were longer in males (21.7 ± 5.0 mm) than females (19.45 ± 4.6 mm). The mean diameters of both the superior and inferior openings were significantly greater in females (p < 0.01). SNF, in contrast, were present in 100% of scapulae. They were located in the supraspinous fossa (36.7%), subscapular fossa (31.3%), infraspinous fossa (22.8%), and peri-glenoid area (10.0%).

CONCLUSION

Unlike previous studies, the present study suggests that SF are normal anatomical findings, present in 78.0% of the scapulae investigated. Surgeons should be aware of both SNF and SF when operating or interpreting radiological findings.

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).