[Anatomical study of the limited osteotomy suture button fixation Latarjet procedure with coracoacromial ligament preservation].

Objective: To investigate the morphological characteristics of the glenohumeral joint (including the glenoid and coracoid) in the Chinese population and determine the feasibility of designing coracoid osteotomy based on the preoperative glenoid defect arc length by constructing glenoid defect models and simulating suture button fixation Latarjet procedure. Methods: Twelve shoulder joint specimens from 6 adult cadavers donated voluntarily were harvested. First, whether the coracoacromial ligament and conjoint tendon connected was anatomically observed and their intersection point was identified. The vertical distance from the intersection point to the coracoid, the maximum allowable osteotomy length starting from the intersection point, and the maximum osteotomy angle were measured. Next, the anteroinferior glenoid defect models of different degrees were randomly constructed. The arc length and area of the glenoid defect were measured. Based on the arc length of the glenoid defect of the model, the size of coracoid oblique osteotomy was designed and the actual length and angle of the coracoid osteotomy were measured. A limited osteotomy suture button fixation Latarjet procedure with the coracoacromial ligament and pectoralis minor preservation was performed and the position of coracoid block was observed. Results: All shoulder joint specimens exhibited crossing fibers between the coracoacromial ligament and the conjoint tendon. The vertical distance from the tip of the coracoid to the coracoid return point was 24.8-32.2 mm (mean, 28.5 mm). The maximum allowable osteotomy length starting from the intersection point was 26.7-36.9 mm (mean, 32.0 mm). The maximum osteotomy angle was 58.8°-71.9° (mean, 63.5°). Based on the anteroinferior glenoid defect model, the arc length of the glenoid defect was 22.6-29.4 mm (mean, 26.0 mm); the ratio of glenoid defect was 20.8%-26.2% (mean, 23.7%). Based on the coracoid block, the length of the coracoid osteotomy was 23.5-31.4 mm (mean, 26.4 mm); the osteotomy angle was 51.3°-69.2° (mean, 57.1°). There was no significant difference between the arc length of the glenoid defect and the length of the coracoid osteotomy ( P>0.05). After simulating the suture button fixation Latarjet procedure, the highest points of the coracoid block (suture loop fixation position) in all models located below the optimal center point, with the bone block concentrated in the anteroinferior glenoid defect position. Conclusion: The size of the coracoid is generally sufficient to meet the needs of repairing larger glenoid defects. The oblique osteotomy with preserving the coracoacromial ligament may potentially replace the traditional Latarjet osteotomy method.

Development of a musculoskeletal shoulder model considering anatomic joint structures and soft-tissue deformation for dynamic simulation.

The shoulder joint has a high degree of freedom and an extremely complex and unstable kinematic mechanism. Coordinated contraction of the rotator cuff muscles that stop around the humeral head and the deltoid muscles and the extensibility of soft tissues, such as the joint capsule, labrum, and ligaments, contribute to shoulder-joint stability. Understanding the mechanics of shoulder-joint movement, including soft-tissue characteristics, is important for disease prevention and the development of a device for disease treatment. This study aimed to create a musculoskeletal shoulder model to represent the realistic behavior of joint movement and soft-tissue deformation as a dynamic simulation using a rigid-body model for bones and a soft-body model for soft tissues via a spring-damper-mass system. To reproduce the muscle-contraction properties of organisms, we used a muscle-expansion representation and Hill's mechanical muscle model. Shoulder motion, including the movement of the center of rotation in joints, was reproduced, and the strain in the joint capsule during dynamic shoulder movement was quantified. Furthermore, we investigated narrowing of the acromiohumeral distance in several situations to induce tissue damage due to rotator cuff impingement at the anterior-subacromial border during shoulder abduction. Given that the model can analyze exercises under disease conditions, such as muscle and tendon injuries and impingement syndrome, the proposed model is expected to help elucidate disease mechanisms and develop treatment guidelines.

Human shoulder anatomy: new ultrasound, anatomical, and microscopic perspectives.

This study aimed to describe the shoulder anatomy, together with the anatomical relationships in adults and early stages of development. The shoulder muscles were studied from ultrasound, anatomical, and microscopic perspectives in a sample of 34 human shoulders. Thickness measurements were taken of the tendons and fasciae of the subscapularis, long head tendon of the biceps brachii, supraspinatus, infraspinatus, and teres minor. Ultrasound and dissection techniques are strongly correlated. However, the measurements obtained from the dissection technique were superior to those obtained from the ultrasound in all cases, except for the thickness of the long head tendon of the biceps brachii, the teres minor tendon, and the fascia thickness of the infraspinatus. In addition, the study of shoulder anatomy revealed no differences between females and males. Relevant findings from dissection included a clear overlap between the infraspinatus and supraspinatus, which shared tendon fibers, and a similar connection between the transverse ligament of the long head tendon of the biceps brachii and the subscapularis, which created a more interconnected shoulder function. The study of the anatomical measurements shows an underestimation of the shoulder measurements in the ultrasound compared with the dissection technique, but a high correlation between the measurements made by the two techniques. We present reference values for the tendon and fascia thicknesses of the rotator cuff, with no differences observed by gender. The relationships between shoulder structures described in the anatomical study imply as well that, in the event of an injury, adjacent tissues may be affected. This extended information may facilitate future optimal clinical explorations.

Tension Distribution in Articular Surfaces of the Rotator Cable and Crescent: A Cadaveric Study.

BACKGROUND: The rotator cable functions as a stress and/or load transfer structure. Some studies suggested that a disruption of the cable negatively affects shoulder function and tendon integrity in patients with rotator cuff tears, while others found no functional impairment regardless of rotator cable tear severity. Although anatomical studies have identified distinct regions within the rotator cuff muscles, the strain distribution within the articular sides of the rotator cuff tendons that results from the tension in each region remains unknown. We hypothesized that the posterior region of the supraspinatus (SSP) muscle and the middle region of the infraspinatus (ISP) muscle, with their firm capsular attachments to the cable, transmit 3D strains, and thus tension, to the whole cable, leading to differences in tension within the cable. METHODS: The 3D strain distributions in the articular sides of the SSP and ISP tendons of 8 fresh-frozen cadaveric intact shoulders were determined when tension was applied to the various SSP and ISP muscle regions. RESULTS: Loading the anterior SSP muscle region yielded significantly higher strains in the anterior third of the cable compared with the posterior third (p < 0.05). Loading the posterior SSP muscle region yielded no significant differences among the cable and crescent regions. Loading the middle ISP muscle region yielded higher strains in the anterior and posterior thirds of the cable compared with the middle third (p < 0.01). Loading the superior ISP muscle region yielded no significant differences among the cable and crescent regions (p > 0.05). CONCLUSIONS: Tension generated from the posterior region of the SSP muscle and middle region of the ISP muscle was evenly distributed to the anterior and posterior attachments of the rotator cable, while the tension generated from other SSP and ISP muscle regions was locally transmitted to the respective attachment area. CLINICAL RELEVANCE: The rotator cable and crescent serve pivotal roles in transmitting tension generated from the deep regions of the rotator cuff muscles, i.e., the posterior SSP and middle ISP. These findings indicate that both the rotator cable and the rotator crescent play crucial roles as tension transmitters for the deep regions of the rotator cuff muscles. This information could have important implications for developing anatomically relevant repair techniques and enhancing rehabilitation protocols.

How anatomic should anatomic total shoulder arthroplasty be? Evaluation of humeral head reconstruction with the best-fit circle.

BACKGROUND: Humeral implant designs for anatomic total shoulder arthroplasty (aTSA) focus on anatomic reconstruction of the articular segment. Likewise, the pathoanatomy of advanced glenohumeral osteoarthritis often results in humeral head deformity. We hypothesized the anatomic reconstruction of the humeral head in aTSA risks overstuffing the glenohumeral joint. METHODS: Ninety-seven cases (52 females) of primary glenohumeral osteoarthritis in patients treated with aTSA were evaluated. Preoperative computed tomography scans were used to classify glenoid morphology according to the Walch classification. Coronal plane images in the plane of the humerus were used to determine the anatomic best-fit circle as described by Youderian et al. Humeral head thinning was determined as the distance from the center of rotation of the best-fit circle to the nearest point along the humeral articular surface. aTSA was modeled with a predicted anatomic humeral head and a simulated 4-mm polyethylene glenoid component. The change in the position of the native humerus was determined. Wilcoxon Rank Sum tests were used to evaluate differences in humeral head thinning and humeral lateralization between monoconcave and biconcave glenoid morphologies. Spearman's rank correlation coefficients were used to assess the relationship between humeral head thinning with preoperative active forward elevation and external rotation. RESULTS: The mean radius of the best-fit circle was 25.0 ± 2.1 mm. There was a mean thinning of 2.4 ± 2.0 mm (range -1.7 to 8.3). The mean percent thinning of the humeral head was 9.4% ± 7.7%. The mean humeral lateralization was 6.4 ± 2.0 mm. Humeral head thinning was not significantly associated with active forward elevation (r = -0.15, P = .14) or active external rotation (r = -0.12, P = .25). There were no significant differences in the percentage of humeral head thinning (P = .324) or humeral lateralization (P = .350) between concentric and eccentric glenoid wear patterns. CONCLUSIONS: Utilization of the best-fit circle as a guide in aTSA may risk excessive lateralization of the humerus and overstuffing the glenohumeral joint. This may have implications for subscapularis repair and healing, as well as glenoid implant and rotator cuff longevity. These findings call into question whether recreation of normal glenohumeral anatomy in aTSA is appropriate for all patients. Humeral head reconstruction in aTSA should account for glenohumeral joint volume and soft tissue contracture.

Scapular morphology variation affects reverse total shoulder arthroplasty biomechanics. A predictive simulation study using statistical and musculoskeletal shoulder models.

Reverse total shoulder arthroplasty (RTSA) accounts for over half of shoulder replacement surgeries. At present, the optimal position of RTSA components is unknown. Previous biomechanical studies have investigated the effect of construct placement to quantify mobility, stability and functionality postoperatively. While studies have provided valuable information on construct design and surgical placement, they have not systematically evaluated the importance of scapular morphology on biomechanical outcomes. The aim of this study was to assess the influence of scapular morphology variation on RTSA biomechanics using statistical models, musculoskeletal modeling and predictive simulation. The scapular geometry of a musculoskeletal model was altered across six modes of variation at four levels (±1 and ±3 SD) from a clinically derived statistical shape model. For each model, a standardized virtual surgery was performed to place RTSA components in the same relative position on each model then implemented in 50 predictive simulations of upward and lateral reaching tasks. Results showed morphology affected functional changes in the deltoid moment arms and recruitment for the two tasks. Variation of the anatomy that reduced the efficiency of the deltoids showed increased levels of muscle force production, joint load magnitude and shear. These findings suggest that scapular morphology plays an important role in postoperative biomechanical function of the shoulder with an implanted RTSA. Furthermore a "one-size-fits-all" approach for construct surgical placement may lead to suboptimal patient outcomes across a clinical population. Patient glenoid as well as scapular anatomy may need to be carefully considered when planning RTSA to optimize postoperative success.

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.

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

BACKGROUND: The etiology of rotator cuff tears (RCTs) have been investigated for years and many underlying causes have been identified. Shoulder joint morphology is one of the extrinsic causes of RCTs. AIM: Morphometric measurements on MRI sections determined which parameters are an important indicator of RCT in patients with shoulder pain. The aim of this study was to determine the risk factors in the etiology of RCTs by evaluating the shoulder joint morphology with the help of previously defined radiological parameters. METHOD: Between January 2019-December 2020, 408 patients (40-70 years old) who underwent shoulder MRI and met the criteria were included in the study. There were 202 patients in the RCT group and 206 patients in the control group. Acromion type, acromial index (AI), critical shoulder angle (CSA), acromiohumeral distance (AHD), lateral acromial angle (LAA), acromial angulation (AA), acromion-greater tuberosity impingement index (ATI), and glenoid version angle (GVA) were measured from the MRI images of the patients. RESULTS: AI (0.64 vs. 0.60, p = 0.003) CSA (35.3° vs. 32.4°, p = 0.004), ATI (0.91 vs. 0.83, P < 0.001), and AA (13.6° vs. 11.9°, p = 0.011) values were higher in the RCT group than in the control group and the difference was significant. AHD (8.1 mm vs. 9.9 mm, P < 0.001), LAA (77.2° vs. 80.9°, p = 0.004) and GVA (-3.9° vs. -2.5°, P < 0.001) values were lower in the RCT group than in the control group, and again the difference was significant. According to the receiver operating characteristic curve analysis, the cutoff values were 0.623 for AI and 0.860 for ATI. CONCLUSION: Acromion type, AI, CSA, AHD, LAA, AA, ATI, and GVA are suitable radiological parameters to evaluate shoulder joint morphology. High AI, CSA, AA, ATI, GVA and low AHD and LAA are risk factors for RCT.

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.