Acromioclavicular Joint Anatomy and Biomechanics: The Significance of Posterior Rotational and Translational Stability

The biomechanical phenomena observed in the cell invasion pathway of porcine epidemic diarrhea virus: a review

Porcine epidemic diarrhea virus (PEDV) is the primary pathogen responsible for highly contagious intestinal infections in pigs, which results in significant economic losses to the global animal husbandry industry. PEDV is an enveloped virus that enters cells via endocytosis, a process that is dependent on the binding of the viral surface S protein to a receptor on the host cell membrane. This results in a series of biomechanical alterations that drive the fusion of the viral and host cell membranes. These alterations stabilise the binding of the virus to the receptor and also affect the tension and the curvature of the plasma membrane and the formation of endocytic vesicles. A comprehensive understanding of the mechanism by which PEDV enters cells and the biomechanical changes that accompany this process is of paramount importance for the development of PEDV inhibitors, vaccines, and disease prevention and control strategies. Here, we review the general mechanism of PEDV entry, the biomechanical phenomena that occur during endocytosis, and the potential applications of biomechanics in antiviral therapy. It is anticipated that by gaining insight into these mechanisms, novel approaches to regulating viral entry pathways through mechanical interference, vaccine development, and antiviral drug design can be explored.

Kinematic analysis of the sternoclavicular, acromioclavicular and scapulothoracic joint demonstrates significant multiplanar alterations in acromioclavicular injuries with each consecutive ligamentous injury during movements of the shoulder girdle: A whole-cadaver study

PURPOSE

In acromioclavicular (AC) joint injuries, the kinematical interplay between the AC ligament, coracoclavicular (CC) ligaments and deltotrapezial fascia (DTF) during motions of the shoulder complex is disturbed. This study assessed kinematic alterations of sternoclavicular (SC), scapulothoracic (ST) and AC joint motion during humerothoracic and ST movements in AC injuries.

METHODS

Shoulder girdle motion was evaluated in 14 cadaveric shoulders in 4 conditions, consisting of an intact state and AC injuries of increasing severity by sequentially sectioning the AC and CC ligaments and DTF. Joint motions were registered during humerothoracic elevation and protraction. An optical navigation system measured three-dimensional rotations and translations in the SC, ST and AC joints.

RESULTS

Sectioning of the AC ligament increased inferior and anterior AC translation with a concomitant increase of scapular protraction. The clavicle rotated to an overall more posteriorly rotated position. Sectioning of the CC ligaments increased lateral rotation and protraction of the scapula relative to the clavicle with a concomitant inferior translation of the acromion. Also, manifest overriding of the clavicle is noted due to instability in the superoinferior and anteroposterior axes. The clavicle rotated back to an overall more anteriorly rotated position, similar to the native condition. Sectioning of the DTF further increased protraction of the scapula relative to the clavicle, while a further medial translation of the acromion under the clavicle is observed.

CONCLUSION

The AC ligament affects anteroposterior stability, while the CC ligaments disturb stability in a superoinferior and mediolateral direction. All ligaments influence clavicular axial rotation. The DTF exacerbates alterations caused by the CC ligaments. Multiplanar decoupling results in overriding of the clavicle observed after sectioning the CC ligaments. Each sectioned ligament significantly increases scapular protraction. These findings guide further advancements in (non)surgical treatment of AC injuries to restore optimal function.

LEVEL OF EVIDENCE

N/A.

Effect of Acromioclavicular Joint Injuries on the Acromioclavicular Joint Complex and Scapulohumeral Rhythm: A Functional and Mechanical Perspective

This overview approaches the acromioclavicular joint (ACJ) and ACJ injuries from a mechanical perspective that places the ACJ complex-the scapula, clavicle, ACJ, AC and coracoclavicular ligaments, and periscapular muscles-into the context of its ability to facilitate scapulohumeral rhythm (SHR) functions of scapula placement and humeral mobility. Mechanical concepts underlying this perspective include linkage of the scapula and clavicle into a single segment, the "claviscapula," the role of the AC and coracoclavicular ligaments in torque transduction and horizontal and vertical stability, and the deleterious effects of decoupling the claviscapular segment. The clinical examination and surgical treatment should address anatomic restoration of individual structures and the effect on the functional integrity of the entire ACJ complex within SHR. This context, which unifies anatomic injury with functional consequences, can be used to create a more comprehensive understanding of the clinical presentation and effect on ACJ function and SHR.

Current Concepts in Management of Acromioclavicular Joint Injury

Background: The management of acromioclavicular joint injuries requires a thorough understanding of the anatomy and biomechanics of the joint, as well as knowledge of the pertinent physical exam findings and classification to determine an appropriate treatment approach, whether operative or nonoperative. In this article, we present a narrative review of the current state of understanding surrounding these issues. Although there are a large number of options for operative intervention, we additionally present our experience with anatomic coracoclavicular ligament reconstruction (ACCR) with imbrication of the deltoid fascia. Methods: A retrospective review of prospectively collected data on a total of 45 patients who had undergone ACCR between 2003 and 2016 were collected. Results: We found that improvements were seen in American Shoulder and Elbow Surgeons Score (ASES) (53 ± 19 to 81 ± 23), Simple Shoulder Test (SST) (6 ± 3 to 12 ± 13), Constant-Murley (CM) (60 ± 18 to 92 ± 8), and Rowe (67 ± 14 to 89 ± 11) and the mean post-operative SANE score was 86 ± 17. Conclusions: ACCR has the advantage of addressing both horizontal and vertical stability with good outcomes.