The 2D and 3D MR arthrographic description of aponeurotic expansion of supraspinatus tendon and biceps tendon anomaly in a large patient cohort.

OBJECTIVE: To describe the aponeurotic expansion of supraspinatus tendon (AEST) and biceps tendon abnormalities with magnetic resonance (MR) arthrographic examinations and determine their prevalence in patients, we performed a high-resolution 3D direct MR arthrography. MATERIALS AND METHODS: This was a retrospective study of 700 shoulder MR arthrograms performed between May 2010 and January 2022. Extension in the coronal plane of an AEST on 3D fat-suppressed T1-weighted volumetric interpolated breath-hold examination (VIBE) MR arthrography was identified. Based on its morphology, the AEST on MR arthrography was divided into four subtypes: absence of tendinous thickness in the bicipital synovial surface or intra-synovial tendon-like structure in the bicipital groove, thin and flat tendinous thickness ≥1 mm of bicipital synovium, oval tendinous structure less than half the size of the adjacent biceps tendon, oval tendinous structure more than half the size of the adjacent biceps tendon, and oval tendinous structure larger than the adjacent biceps tendon. Based on its origin and termination, aponeurotic expansions can be divided into three subtypes: proximal pulley zone, middle humeral neck zone, and distal myotendinous junction zone. Association with the biceps synovium of the AEST was categorized into three types: intra-synovial, extra-synovial, and trans-synovial. RESULTS: An AEST in the anterior shoulder joint in 3D VIBE MR arthrography images was identified in 63 (9%) of 700 arthrograms. The most common arthrographic type of AEST was type 1-this was detected in 39 of 63 patients. The most common course type of the AEST was anteriorly midline. The most common distal insertion type was at the tenosynovial sheath of the long head of the biceps tendon (LHBT) in the middle humeral neck zone-this was detected in 31 of 63 patients. There were only 10 MR arthrograms biceps tendon abnormality, including 4 biceps agenesis and 6 split ruptures. CONCLUSION: A 2D and high-resolution 3D MR arthrography can demonstrate the anatomical detail around the bicipital groove and facilitate the differentiation between a biceps tendon anomaly and an AEST. On high-resolution 3D MR arthrographic images, the AEST tends to be in the anterior midline and anteromedial portions of the biceps synovium with intra-synovial, extra-synovial, and trans-synovial courses and its three different insertion types.

Functional anatomy of shoulder muscles in the Pacific white-sided dolphin (Lagenorhynchus obliquidens).

Most intrinsic muscles of the forelimb in dolphins are either degenerated or lost; however, the muscles around the shoulder joint are well preserved. We dissected the forelimbs of Pacific white-sided dolphins and constructed a full-scale model of the flipper to compare and examine their movements following dissection. The humerus was oriented at approximately 45° ventrally from the horizontal plane of the dolphin and 45° caudally from the frontal plane. This maintains the neutral position of the flipper. The deltoideus and pectoralis major muscles were inserted into the body of the humerus, and the flipper was moved in the dorsal and ventral directions, respectively. A large tubercle, known as the common tubercle, was observed at the medial end of the humerus. Four muscles were inserted into the common tubercle: the brachiocephalicus, supraspinatus, and cranial part of the subscapularis, which laterally rotated the common tubercle. Subsequently, the flipper swung forward, and its radial edge was lifted. Conversely, the medial rotation of the common tubercle caused by the coracobrachialis and the caudal part of the subscapularis was accompanied by backward swinging of the flipper and lowering of the radial edge. These findings suggest the function of the flipper as a stabilizer or rudder is caused by the rotation of the humerus's common tubercle.

Restudy of shoulder motion in the theropod dinosaur Mononykus olecranus (Alvarezsauridae).

Background: Range of motion in the forelimb of the Upper Cretaceous theropod dinosaur Mononykus olecranus, a member of the family Alvarezsauridae, has previously been investigated. However, the method used to investigate range of motion at the shoulder in M. olecranus did not follow the standardized procedure used in subsequent studies. The latter procedure yields more reliable results, and its standardization provides that its results are directly comparable to the results of similar studies in other species. I therefore reinvestigated the range of motion at the shoulder in M. olecranus, using the latter procedure. Methods: Casts of the left scapula and coracoid of M. olecranus were posed on a horizontal surface, supported from beneath with modeling clay, with the medial surface of the scapula facing toward the horizontal surface. A cast of the left humerus was posed at the limits of motion through the transverse and parasagittal planes. Photos of the poses in orthal views were superimposed and used to measure range of motion, which was measured as the angle between lines drawn down the long axis of the humerus in each position. Results: Through the transverse plane, the humerus of M. olecranus could be elevated to a subhorizontal position and depressed to a subvertical position. It could move through the parasagittal plane from a subvertical position at full protraction to a position above the horizontal at full retraction. These results correct the previous mischaracterization of shoulder motion in M. olecranus as restricted to a small arc with the arms held in a permanent sprawl. The range of humeral motion in M. olecranus is much greater than that found by the previous method and allowed the animal to tuck its arms in at the sides, in addition to allowing them to sprawl so as to orient the palm downward. The wide range of humeral motion allowed M. olecranus to forage for insects by employing hook-and-pull digging at surfaces with a wider range of orientations than the previous study showed to be possible.

Evaluation of Preoperative Magnetic Resonance Imaging Parameters with Arthroscopic Validation of Subscapularis Tendon Abnormalities in 187 Patients at a Single Center in Turkey.

BACKGROUND This study from a single center in Turkey aimed to evaluate preoperative magnetic resonance imaging (MRI) parameters with arthroscopic validation of subscapularis (SS) tendon abnormalities in 187 patients. MATERIAL AND METHODS Preoperative MRI scans of 187 patients who had undergone arthroscopic shoulder surgery by the senior author (all in lateral decubitus position) were evaluated by 3 researchers. Patients with arthroscopically proven SS tendon rupture (n=69) and without rupture (n=118) were divided into 2 groups and compared with various distances and angles. The following parameters were measured: coracohumeral distance (CHD), coracoid morphology, coraco-glenoid angle (CGA), coracoid angle (CA), coraco-humeral angle (CHA), coracoid overlap (CO), coracoid body-glenoid angle (CBGA), coracoid tip-glenoid angle (CTGA), coracoid tip-body angle (CTBA), coraco-scapular angle (CSA), lesser tuberosity angle (LTA), and lesser tuberosity height (LTH). RESULTS CHD, CHA, CA, and LTA values decreased in the SS tendon rupture group; coracoid type grade and CO increased (all P<0.001, excluding LTA [P=0.022]). The cut-off values of these measurements were CHD=7.25 mm, CHA=107.25°, CA=111.5°, LTA=31.7°, and CO=16.5 mm. The differences in CGA and CBGA values were not statistically significant (P=0.11, 0.441, respectively). CTGA, CTBA, LTH, and CSA measurements were not included in the intergroup comparisons due to insufficient inter-observer reliability (kappa=0.478, 0.239, 0.496, 0.309, respectively). Power (1- b) in post hoc analysis was calculated as 0.941. CONCLUSIONS SS tendon rupture was associated with a reduction in the parameters of CHD, CHA, CA, and LTA and an increase in CO on MRI.

The morphofunctional implications of the glenoid labrum of the glenohumeral joint in hominoids.

OBJECTIVES: A morphocline of the glenoid cavity has been used to infer differences in locomotor behaviors; however, the glenoid cavity is surrounded by the glenoid labrum, a fibrocartilaginous structure that could influence the functionality of the glenoid. The objectives of this study are to explore the effects of the glenoid labrum on the area, depth, and morphology of the glenoid cavity in primates. MATERIALS AND METHODS: Photogrammetry was used to build 3D models of the glenoid, with and without the labrum, and three- (3D) and two-dimensional (2D) geometric morphometrics (GM) was applied. 2D areas were collected from zenithal images for glenoids with and without labrum to evaluate the availability of articular surface area. RESULTS: In the 2D GM the morphocline is present in the dry-bone sample but not with the presence of the glenoid labrum. In the 3D GM there are differences between species mainly concerning the depth of the glenoid cavity. 2D areas reveal that the amount of articular area of the glenoid cavity increases with the presence of the labrum, particularly in humans. DISCUSSION: The glenoid labrum changes the shape, increases the depth and the surface area of the glenoid cavity, particularly in humans. Therefore, the glenoid labrum might hold a functional role, increasing the stability of the glenohumeral joint of primates in general, and especially in humans.

A shallow morphology of the intertubercular groove is associated with medial and bilateral but not lateral pulley lesions.

PURPOSE: To investigate the influence of intertubercular groove (IG) morphology on the development of different types of biceps reflection pulley (BRP) injuries. METHODS: A consecutive cohort of 221 patients with ventral shoulder pain and a preoperative diagnosis suspecting BRP injury, who underwent arthroscopy, was retrospectively reviewed. The presence or absence as well as type of pulley injury (medial, lateral or bilateral) was confirmed arthroscopically. The intertubercular groove was evaluated on MRIs after triplanar reconstruction of the axial plane. IG depth, width, medial wall angle (MWA), lateral wall angle (LWA) and total opening angle (TOA) were measured. IG depth and width were expressed in relation to the humeral head diameter. Measurements were performed by two clinicians independently and averaged. RESULTS: Of 166 included patients 43 had bilateral, 65 medial and 38 lateral BRP lesions. 20 patients had intact BRPs and represented the control group. The intra-class correlation coefficient of measurements was 0.843-0.955. Patients with a medial or bilateral BRP injury had a flatter MWA (38.8° or 40.0° vs. 47.9°, p < 0.001), wider TOA (96.1° or 96.6° vs. 82.6°, p < 0.001), greater width (12.5 or 12.3 vs. 10.8 mm, p = 0.013) and shallower depth (5.5 or 5.4 vs. 6.2 mm, p < 0.001) than the control group. Conversely, the IG morphology of those with lateral BRP injuries did not differ significantly from the control group. The odds ratio for a medial or bilateral BRP injury when the TOA exceeded 95° was 6.8 (95% confidence interval 3.04-15.2). CONCLUSION: A dysplastic type of IG morphology with a wide TOA, flat MWA, decreased depth and increased width is associated with the presence of medial and bilateral BRP injuries. A TOA of > 95° increases the likelihood of a medial or bilateral BRP injury 6.8-fold. Lateral BRP injuries are not associated with dysplastic IG morphology. Concomitant LHBT surgery may, therefore, not always be necessary during isolated supraspinatus tendon repair. LEVEL OF EVIDENCE: Level III.

Anatomy features of the shoulder joint in asymptomatic chinese Han adults.

BACKGROUND: To evaluate the shoulder anatomical characteristics in asymptomatic Chinese adults. METHODS: The prospective study enrolled individuals without shoulder pain at Beijing Tiantan Hospital Affiliated to Capital Medical University between January 2019 and January 2020. Six radiographic parameters were measured and analyzed, including glenoid plane to the acromion (GA), glenoid plane to the lateral aspect of the humeral head (GH), acromion index (AI), lateral acromial angle (LAA), acromion-humeral interval (AHI), and critical shoulder angle (CSA). RESULTS: 103 participants (51 males and 52 females) were enrolled. The mean values of GA, GH, AI, CSA, LAA, and AHI were 32.88 ± 5.68 mm, 47.16 ± 4.82 mm, 0.70 ± 0.11, 37.45 ± 6.00°, 6.32 ± 3.99°, and 9.611.86 mm, respectively. Females had lower GA (30.78 ± 5.06 vs. 35.01 ± 5.51 mm, P < 0.001) and GH (44.28 ± 3.67 vs. 50.11 ± 4.02 mm, P < 0.001) than males and LAA was significantly smaller in the Bigliani flat type compared with the curved type and the hooked type (5.07 ± 2.31° vs 12.33 ± 5.46°vs 10.00 ± 3.37, P = 0.001). CONCLUSIONS: Females had lower GA and GH than males in asymptomatic Chinese Han adults. Asymptomatic Chinese Han subjects with Bigliani flat type had lower LAA. CSA appears lager in Chinese Han individuals. Curve type of acromion performed lager LAA. The results may help establish an anatomical model of the shoulder joint and elucidate the anatomy features of the shoulder joint in asymptomatic Chinese Han adults.

Scapular morphology of great apes and humans: A three-dimensional computed tomography-based comparative study.

The primate scapula has been studied widely since its shape has been shown to correlate with how the forelimb is used in daily activities. In this study, we expand on the existing literature and use an image-based methodology that was originally developed for orthopaedic practice to quantify and compare the three-dimensional (3D) morphology of the scapula across humans and great apes. We expect that this image-based approach will allow us to identify differences between great apes and humans that can be related to differences in mobility and loading regime of the shoulder. We hypothesize that gorillas and chimpanzees will have a similar scapular morphology, geared towards stability and weight-bearing in knuckle-walking, whilst the scapular morphology of orangutans is expected to be more similar to that of humans given their high glenohumeral mobility associated with their suspensory lifestyle. We made 3D reconstructions of computed tomography scans of 69 scapulae from four hominid genera (Pongo, Gorilla, Pan and Homo). On these 3D bone meshes, the inferior glenoid plane was determined, and subsequently, a set of bony landmarks on the scapular body, coracoid, and acromion were defined. These landmarks allowed us to measure a set of functionally relevant angles which represent acromial overhang, subacromial space and coracoacromial space. The angles that were measured are: the delto-fulcral triangle (DFT), comprising the alpha, beta, and delta angle, the acromion-glenoid angle (AGA), the coracoid-glenoid centre-posterior acromial angle (CGA), the anterior tilt (TA CGA) and the posterior tilt of the CGA (PT CGA). Three observers placed the landmarks on the 3D bone meshes, allowing us to calculate the inter-observer error. The main differences in the DFT were found between humans and the great apes, with small differences between the great apes. The DFT of humans was significantly lower compared to that of the great apes, with the smallest alpha (32.7°), smallest delta (45.7°) and highest beta angle (101.6°) of all genera. The DFT of chimpanzees was significantly higher compared to that of humans (p < 0.01), with a larger alpha (37.6°) and delta angle (54.5°) and smaller beta angle (87.9°). The mean AGA of humans (59.1°) was significantly smaller (p < 0.001) than that of gorillas (68.8°). The mean CGA of humans (110.1°) was significantly higher (p < 0.001) than in orangutans (92.9°). Humans and gorillas showed mainly a posterior tilt of their coracoacromial complex whilst chimpanzees showed mainly an anterior tilt. The coracoacromial complex of the orangutans was not tilted anteriorly or posteriorly. With our image-based method, we were able to identify morphological features of the scapula that differed significantly between hominid genera. However, we did not find an overall dichotomy in scapular morphology geared towards high stability (Pan/Gorilla) or high mobility (Homo/Pongo). Further research is needed to investigate the functional implications of these differences in scapular morphology.

Morphological and radiological study of the shoulder and elbow joints of the giant anteater (Myrmecophaga tridactyla).

The giant anteater (Myrmecophaga tridactyla) has specialized thoracic limbs to forage by breaking the walls of anthills and termite mounds. They also play critical roles in defense posture and locomotion. This study aimed to provide a morphological and radiographic description of the shoulder joint and elbow joint of the giant anteater. Both joints of 13 tamanduas were assessed by morphological dissections and histological evaluation and radiographies without and with positive contrast. The radiographic projections selected to this study were the mediolateral and craniocaudal projections. The radiographic and anatomical findings were compared with the following results: the shoulder joint had a continuous joint capsule with the tendon sheaths of the short head and long head of the biceps brachii muscle, which could be visualized with an injection of 3 ml of intra-articular contrast. The shoulder joint arthrography was performed with the needle positioned cranially to the joint for contrast injection. The elbow joint presented three articular compartments, and the insertion of the joint capsule was proximal to the radial fossa and distal to the radial tuberosity in the radial notch of the ulna, which were possible to identify with 2 ml of intra-articular contrast. The elbow joint arthrography was performed with the needle positioned laterally to the joint for contrast injection. Moreover, the joint capsule presented a caudomedial distention and fat pads. The powerful muscles of the forelimb play a fundamental role in maintaining the shoulder joint and elbow joint stability due to bony adaptations and the absence of usual ligaments. The morphological and radiological study provided relevant information on the soft-tissue characteristics of shoulder and elbow joints, which may aid clinical-surgical and diagnostic imaging procedures.

Anteroposterior and Lateral Coverage of the Acromion: Prediction of the Rotator Cuff Tear and Tear Size.

Background: The aim of this study was to assess whether the anteroposterior coverage of the acromion reflecting acromial morphology affects the rotator cuff tear (RCT) and tear size, in addition to the lateral coverage. Methods: Medical records of 356 patients with RCTs, concentric osteoarthritis, and calcific tendinitis identified using three-dimensional computed tomography between January 2016 and December 2017 were retrospectively analyzed. The patients were divided into group A (those with RCTs) and group B (those with concentric osteoarthritis or calcific tendinitis). Subsequently, group A was subdivided into three categories according to the size of RCTs: small-to-medium, large, and massive. The lateral coverage was measured through the lateral acromial angle (LAA) and critical shoulder angle (CSA), whereas the anteroposterior coverage was measured via the acromial tilt (AT), acromiohumeral interval (AHI) in the sagittal view, and anteroposterior coverage index (APCI) as a new radiologic parameter. Results: Between groups A and B, CSA (34.5° ± 3.4° and 30.8° ± 3.4°, respectively), APCI (0.83 ± 0.10 and 0.75 ± 0.08, respectively), and AHI (6.3 ± 2.0 mm and 7.8 ± 1.8 mm, respectively) were significantly different (all p < 0.001), whereas LAA and AT did not show a significant difference between the groups (p = 0.089 and p = 0.665, respectively). The independent predictive radiologic parameters of the RCT were the CSA, APCI, and AHI (p < 0.001, p < 0.001, and p = 0.043, respectively); among these, the APCI showed the highest regression coefficient (odds ratio = 2.82). The parameters associated with the size of RCTs were CSA (p = 0.022) and AHI, of which AHI, in particular, had the most significant effect on both small-to-medium and large tears (all p < 0.001). Conclusions: Large CSA, high APCI, and low AHI were predictors of RCTs, with the APCI showing the strongest correlation. In addition to the large CSA, low AHI also correlated with the size of RCTs and affected the entire size groups. We suggest that both the lateral coverage and anteroposterior coverage of the acromion should be considered essential factors for predicting the presence of RCTs and tear size.

Morphological determination of glenohumeral joint and acromioclavicular joint with computed tomography / Determinación morfológica de la articulación glenohumeral y la articulación acromioclavicular con tomografía computarizada

SUMMARY: Although acute and chronic pathologies of the glenohumeral and acromioclavicular joints are frequently encountered in the population, the anatomy and morphometry are not fully known. The aim of this study is to determine the measurements of morphometric parameters according to age groups and sex in a large series of Turkish population. Nine hundred and forty-one shoulders computed tomography (CT) images were screened and those of subjects with healthy anatomical structure were included. Humeral head diameter (HDD) was measured on CT images. Measurements were made using 3D-CT images of: width (GW) and height (GH) of the glenoid cavity; width (CW) and height (CH) of the distal clavicular joint surface; and width (AW) and height (AH) of the acromial joint surface. Data were compared, stratified by age and sex. Images of 223 patients (118 men, 105 women) were analyzed. The following mean measurements were determined: HDD, 41.77±3.77 mm; GH, 34.66±3.26 mm; GW, 25.50±2.90 mm; CW, 14.85±3.51 mm; CH, 8.49±2.27 mm; AW, 12.97±2.94 mm; AH, 7.01±1.77 mm. When startified by sex, HDD (p<0.001), GH (p<0.001), GW (p<0.001), CW (p<0.001), CH (p=0.002), AW (p<0.001) and AH (p<0.001) measurements were significantly different and mean values were greater in men. Similarly for age, significant differences were found for GH (p=0.028), CW (p<0.001), AW (p<0.001), AH (p<0.001). The parametric values we have obtained in the Turkish population we measure differ from the measurements made in different populations according to age groups and sex. Knowing these features will contribute to treatment planning, implant and prosthesis applications.

Aunque las patologías agudas y crónicas de las articulaciones glenohumeral y acromioclavicular son frecuentes en la población, la anatomía y morfometría no se conocen por completo. El objetivo de este estudio fue determinar las medidas de los parámetros morfométricos según grupos de edad y sexo en una serie de individuos de población turca. Se examinaron 941 imágenes de tomografía computarizada (TC) de hombro y se incluyeron las de sujetos con una estructura anatómica sana. El diámetro de la cabeza humeral (HDD) se midió en imágenes de TC. Las mediciones se realizaron utilizando imágenes 3D-CT de: ancho (GW) y altura (GH) de la cavidad glenoidea; anchura (CW) y altura (CH) de la superficie articular clavicular; y anchura (AW) y altura (AH) de la superficie articular acromial. Los datos fueron comparados, estratificados por edad y sexo. Se analizaron imágenes de 223 pacientes (118 hombres, 105 mujeres). Se determinaron las siguientes medidas medias: HDD, 41,77±3,77 mm; GH, 34,66 ± 3,26 mm; GW, 25,50±2,90 mm; CW, 14,85±3,51 mm; CH, 8,49±2,27 mm; AW, 12,97±2,94 mm; AH, 7,01±1,77 mm. Cuando se inicia por sexo, HDD (p<0,001), GH (p<0,001), GW (p<0,001), CW (p<0,001), CH (p=0,002), AW (p<0,001) y AH (p <0,001) las mediciones fueron significativamente diferentes y los valores medios fueron mayores en los hombres. De igual forma para la edad se encontraron diferencias significativas para GH (p=0,028), CW (p<0,001), AW (p<0,001), AH (p<0,001). Los valores paramétricos que hemos obtenido en la población turca difieren de las medidas realizadas en diferentes poblaciones según grupos de edad y sexo. El conocimiento de estas características contribuirá a la planificación del tratamiento, aplicaciones de implantes y prótesis.

An unreported infraspinatus muscle variation-two-headed infraspinatus minor muscle and three-headed fusion with the teres minor muscle.

The infraspinatus muscle is situated under the scapular spine in the infraspinous fossa and inserts into the greater tuberosity of the humerus. It is a component of a crucial shoulder muscle group, the rotator cuff. There are a few interesting additional muscles in the infraspinal region. In the literature they are called the infraspinatus superficialis, infraspinatus minor and infraspinatus accessory muscles. The infraspinatus minor muscle is described as a superficial muscle bundle running under the scapular spine. During routine anatomical dissection, an unreported variation of the infraspinatus minor muscle was found. It derived from the inferior surface of the scapular spine and the infraspinous fossa. It had two heads. The superior head inserted on the greater tuberosity of the humerus. The inferior head inserted on the tendinous part of the infraspinatus muscle. There was also an unusual fusion of the infraspinatus muscle with the teres minor muscle. In this paper we will discuss the anatomical and physiological relationships of this morphological variation.

A proposal for a new classification of the long head of the biceps brachii.

INTRODUCTION: The anterior compartment of the arm consists of three muscles: the biceps brachii, brachialis and coracobrachialis. The aim of the present study was to characterize possible variations in the morphology of the proximal attachments of the long head of the biceps brachii and to propose an accurate classification of the area which can be useful for planning surgical procedures and planning rehabilitation in the region. MATERIALS AND METHODS: Eighty (40 left and 40 right, 40 female, 40 male) upper limbs fixed in 10% formalin solution were examined. RESULTS: The main tendon of the long head of the biceps brachii demonstrated three types of attachment. The most common type, Type I (53.75%), was characterized by a single attachment only for the supraglenoid tubercle. Type III (33.75%) was characterized by a single attachment to the glenoid labrum. Type II (12.5%) was characterized by a double attachment to the glenoid labrum and the supraglenoid tubercle. Additionally, two types of the accessory tendon of the long head of the biceps brachii were identified (Type A-B). Type A (14 cases) was attached to the capsule of the humeral joint, and Type B (six cases) was attached to the greater tubercle of the humerus. CONCLUSION: The long head of the biceps brachii is characterized by high morphological variability. The new classification proposes three types of proximal attachment (I-III), with two types of accessory long head of the biceps brachii (A-B) tendon. A thorough understanding of the morphological variability of the long head of the biceps brachii is necessary when planning arthroscopic procedures or even planning rehabilitation procedures.

Glenoid bony morphology along long diameter is associated with the occurrence of recurrent anterior shoulder dislocation: a case-control study based on three-dimensional CT measurements.

PURPOSE: The purpose of our study is to compare the anatomic parameters of proximal humerus, glenoid, and glenohumeral joint between patients with recurrent anterior shoulder dislocation (RASD) and patients without RASD with the assistance of three-dimensional (3D) CT scans. METHODS: Sixty patients were included in the study and divided into group RASD and group control. 3D-CT models of shoulder joint for each included patient were reconstructed and multiple anatomic parameters were measured. RESULTS: There were no statistically significant differences between the two groups in morphological parameters of humerus and glenohumeral joints. Long diameter of glenoid was 3.50 ± 0.34 cm for patients in group RASD and 3.31 ± 0.32 cm in group control (p = 0.039). There was a statistically significant difference in the ratio of long to short diameter of glenoid (p < 0.001). Ratio of humeral head height to glenoid long diameter (Hhh/Gld) was 1.02 ± 0.07 in group RASD, significantly lower than 1.09 ± 0.08 in group control (p = 0.001). Longitudinal depth of glenoid was significantly higher in group RASD (p = 0.013). CONCLUSION: The glenoid morphology along long diameter is closely correlated with the stability of glenohumeral joint, including glenoid long diameter and glenoid longitudinal depth. It is especially noteworthy that the value of Hhh/Gld decreases in patients with RASD. The difference of Hhh/Gld between the two groups reminds us that the correlation of bony structure along long diameter between glenoid and humeral head plays an important role in RASD.

MRI morphological evaluation of humeral head bone profile inside region of the biceps pulley reflection.

OBJECTIVE: Evaluating humeral head bone profile inside biceps reflection pulley area in order to identify possible anatomical variants and any causes predisposing to tendon's instability of the long head of the biceps. MATERIALS AND METHODS: This retrospective study analyzed 326 patients, 183 males and 143 females (age 15-88 years; average 51.5 years), who underwent MRI examination between 2013 and 2019. Biceps pulley reflection area morphology of 192 right shoulders and 134 left shoulders was assessed analyzing 309 MRI and 17 MR arthrography (MRA) shoulder exams. We investigated age and gender and the frequency of morphological variants among the patient groups. RESULTS: Four possible morphological variants were identified: 95 with convex shape; 127 with flat shape; 77 with spiculated shape; and 12 with mixed morphology. Fifteen humeral bone profiles were not classifiable. CONCLUSIONS: MRI was effective in defining humeral head anatomic variants inside the biceps pulley reflection area. The most frequent variants were flat or convex types.

A newly reported muscle: an accessory infraspinatus or a deep layer of the latissimus dorsi?

The infraspinatus muscle is a component of the rotator cuff; the latissimus dorsi muscle is the largest muscle of the back. These muscles are not considered very morphologically variable. However, the latissimus dorsi has more frequent variations than the infraspinatus. During anatomical dissection, an additional muscle structure was found. It originated on the medial border of the scapula, ran under the scapular spine, and ended on the greater tubercle next to the infraspinatus attachment. We will discuss the anatomical and physiological relationships of this muscle. We believe that our finding underlines the importance of different muscle variants in the rotator cuff region. Level of evidence: II basic science research.

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.

Glenohumeral joint reconstruction using statistical shape modeling.

Evaluation of the bony anatomy of the glenohumeral joint is frequently required for surgical planning and subject-specific computational modeling and simulation. The three-dimensional geometry of bones is traditionally obtained by segmenting medical image datasets, but this can be time-consuming and may not be practical in the clinical setting. The aims of this study were twofold. Firstly, to develop and validate a statistical shape modeling approach to rapidly reconstruct the complete scapular and humeral geometries using discrete morphometric measurements that can be quickly and easily measured directly from CT, and secondly, to assess the effectiveness of statistical shape modeling in reconstruction of the entire humerus using just the landmarks in the immediate vicinity of the glenohumeral joint. The most representative shape prediction models presented in this study achieved complete scapular and humeral geometry prediction from seven or fewer morphometric measurements and yielded a mean surface root mean square (RMS) error under 2 mm. Reconstruction of the entire humerus was achieved using information of only proximal humerus bony landmarks and yielding mean surface RMS errors under 3 mm. The proposed statistical shape modeling facilitates rapid generation of 3D anatomical models of the shoulder, which may be useful in rapid development of personalized musculoskeletal models.

Subscapularis minor-does it exist?

INTRODUCTION: It has been well established that the subscapularis is divided in two different parts with a tendinous insertion at its superior two-thirds and a muscular attachment on its inferior third. The objective of this cadaveric study was to follow the muscular insertion of the subscapularis medially in order to determine the origin of this inferior muscle insertion and whether a subscapularis minor can be individualized MATERIALS AND METHODS: Twenty-six shoulders from thirteen fresh-frozen cadaveric specimens (5 males and 8 females; mean age, 74.4 years) were dissected in our anatomy lab. The humeral insertion of the subscapularis was then analyzed, and the inferior muscular part of the insertion was identified. The muscle fibers were followed medially until their scapular origin which was recorded as line drawings and photographs. We measured the dimensions of both the humeral insertion and of the scapular origin of the fibers going to the muscular portion. RESULTS: In all cases, the fibres going to the tendinous portion and those going to the muscular portion of the insertion had a different orientation. The fibres going to the muscular portion of the humeral insertion did not originate from the subscapularis fossa but on the glenoid neck and in a depression at the infero-lateral part of the scapular pillar. The mean length of the superior tendinous portion of the humeral insertion was 3.42 cm (± 0.43 cm); the mean length of the inferior muscular portion of the humeral insertion was 1.88 cm (± 0.80 cm). The mean length of the scapular origin in the depression at the infero-lateral part of the scapular pillar of the fibres going to the muscular portion of the humeral insertion was 3.7 cm (± 0.17 cm). CONCLUSION: The fibres of the subscapularis do not all originate from the subscapularis fossa. An additional origin exists at the inferior part of the glenoid neck and in a depression at the infero-lateral part of the scapular pillar. The fibers which originate at this location all insert on the humerus at the muscular portion of the subscapularis humeral insertion. This portion however does not seem to correspond to the so-called subscapularis minor which has been previously described.

The morphology of the subacromial and related shoulder bursae. An anatomical and histological study.

Shoulder bursae are essential for normal movement and are also implicated in the pathogenesis of shoulder pain and dysfunction. The subacromial bursa (SAB), within the subacromial space, is considered a primary source of shoulder pain. Several other bursae related to the subcoracoid space, including the coracobrachial (CBB), subcoracoid (SCB) and subtendinous bursa of subscapularis (SSB), are also clinically relevant. The detailed morphology and histological characteristics of these bursae are not well described. Sixteen embalmed cadaveric shoulders from eight individuals (five females, three males; mean age 78.6 ± 7.9 years) were investigated using macro-dissection and histological techniques to describe the locations, dimensions and attachments of the bursae, their relationship to surrounding structures and neurovascular supply. Bursal sections were stained with haematoxylin and eosin to examine the synovium and with antibodies against von Willebrand factor and neurofilament to identify blood vessels and neural structures respectively. Four separate bursae were related to the subacromial and subcoracoid spaces. The SAB was large, with a confluent subdeltoid portion in all except one specimen, which displayed a distinct subdeltoid bursa. The SAB roof attached to the lateral edge and deep surface of the acromion and coracoacromial ligament, and the subdeltoid fascia; its floor fused with the supraspinatus tendon and greater tubercle. The CBB (15/16 specimens) was deep to the conjoint tendon of coracobrachialis and short head of biceps brachii and the tip of the coracoid process, while the inconstant SCB (5/16 specimens) was deep to the coracoid process. Located deep to the subscapularis tendon, the SSB was a constant entity that commonly displayed a superior extension. Synovial tissue was predominantly areolar (SAB and SSB) or fibrous (CBB and SCB), with a higher proportion of areolar synovium in the bursal roofs compared to their floors. Blood vessels were consistently present in the subintima with a median density of 3% of the tissue surface area, being greatest in the SSB and SAB roofs (4.9% and 3.4% respectively) and least in the SAB floor (1.8%) and CBB roof and floor (both 1.6%). Nerve bundles and free nerve endings were identified in the subintima in approximately one-third of the samples, while encapsulated nerve endings were present in deeper tissue layers. The extensive expanse and attachments of the SAB support adoption of the term subacromial-subdeltoid bursa. Morphologically, the strong attachments of the bursal roofs and floors along with their free edges manifest as fixed and mobile portions, which enable movement in relation to surrounding structures. The presence of neurovascular structures demonstrates that these bursae potentially contribute blood supply to surrounding structures and are involved in mechanoreception. The anatomical details presented in this study clarify the morphology of the shoulder bursae, including histological findings that offer further insight into their potential function.