Acromioclavicular Joint Instability on Cross-Body Adduction View: The Biomechanical Effect of Acromioclavicular and Coracoclavicular Ligaments Sectioning

Background The relationship between acromioclavicular (AC) joint dislocation, corresponding radiological evaluation, and ligament injuries remains controversial. We hypothesized that AC and trapezoid ligament injuries induce AC joint instability, and the clavicle can override the acromion on cross-body adduction view without conoid ligament injury. We aimed to investigate how biomechanically sectioning the AC and coracoclavicular (CC) ligaments contributes to AC joint instability in the cross-body adduction position using fresh-frozen cadaver models. Methods Six fresh-frozen cadaveric shoulders were used in this study, comprising five male and one female specimen, with a mean age of 68.7 (range, 51–87) years). The left side of the trunk and upper limb, and the cervical and thoracic vertebrae and sternum were firmly fixed with an external fixator. The displacement of the distal end of the clavicle relative to the acromion was measured using an electromagnetic tracking device. We simulated AC joint dislocation by sequential resection of AC ligament, AC joint capsule, and CC ligaments in the following order of stages. Stage 0: Intact AC and CC ligaments and acromioclavicular joint capsule; stage 1: Completely sectioned AC ligament and joint disc; stage 2: Sectioned trapezoid ligament; and stage 3: Sectioned conoid ligament. The superior clavicle displacement related to the acromion was measured in the horizontal adduction position, and clavicle overriding on the acromion was assessed radiologically at each stage. Data were analyzed using a one-way analysis of variance and post-hoc tests. Results Superior displacement was 0.3 mm at stage 1, 6.5 mm at stage 2, and 10.7 mm at stage 3. On the cross-body adduction view, there was no distal clavicle overriding at stages 0 and 1, and distal clavicle overriding was observed in five cases (5/6: 83%) at stage 2 and in six cases (6/6: 100%) at stage 3. Conclusion We found that AC and trapezoid ligament sectioning induced AC joint instability and that the clavicle could override the acromion on cross-body adduction view regardless of conoid ligament sectioning. AC and trapezoid ligament injuries may lead to significant AC joint instability, and the distal clavicle may subsequently override the acromion.

Avulsion Fracture of the Coracoid Process at the Coracoclavicular Ligament Insertion: A Report of Three Cases

Avulsion fracture at the site of attachment of the coracoid process of the coracoclavicular ligament (CCL) is extremely rare. We presented three adult cases of this unusual avulsion fracture associated with other injuries. Case 1 was a 25-year-old right-handed male with a left distal clavicular fracture with an avulsion fracture of the coracoid attachment of the CCL; this case was treated surgically and achieved an excellent outcome. Case 2 was a 39-year-old right-handed male with dislocation of the left acromioclavicular joint with two avulsion fractures: one at the posteromedial surface of the coracoid process at the attachment of the conoid ligament and one at the inferior surface of the clavicle at the attachment site of the trapezoid ligament; this case was treated conservatively, and unfavorable symptoms such as dull pain at rest and sharp pain during some daily activities remained. Case 3 was a 41-year-old right-handed female with a right distal clavicular fracture with an avulsion fracture of the coracoid attachment of the conoid ligament; this case was treated conservatively, and the distal clavicular fracture became typical nonunion. These three cases corresponded to type I fractures according to Ogawa’s classification as the firm scapuloclavicular connection was destroyed and also to double disruption of the superior shoulder suspensory complex. We recommend surgical intervention when treating patients with this type of acute or subacute injury, especially in those engaging in heavy lifting or overhead work.

Carcinoma of the Anterior Commissure of the Larynx: I. Embryological and Anatomic Considerations

In this study we attempt to define the organization of the anterior region of the adult larynx, on the basis of its development. For this purpose, we have studied the development of the anterior commissure region on serial sections of human larynges from embryos, fetuses, and adults. Our findings indicate that all the structures of this region derive from a single median mesenchymal band, first evident at 7 to 8 weeks of gestation, between the lateral laminae of the thyroid cartilage. This band of mesenchyme gives rise to all the structures along the midline of the thyroid cartilage and immediately beyond, including the intermediate lamina of the thyroid cartilage, the median process, and the connective tissue that connects the latter with the conoid ligament. We provide, for the first time, evidence that Broyles' ligament (commissural tendon) derives from the dorsal part of the median process and becomes intimately connected with the surrounding structures, including the insertion fibers of the vocal muscles, from early in development. On the basis of this finding we identify an independent anterior commissure region in the adult larynx, which comprises the intermediate lamina, Broyles' ligament, the connective tissue between the Broyles' and conoid ligaments, and the insertion fibers of the vocal muscles. The interpretation of all these structures as a unified region can explain the peculiar progression pathways and evolution of commissural and cordo-commissural tumors.