The ligaments that surround the sternoclavicular joint guarantee its stability; however, the joint is inherently unstable [2, 3]. A direct force on the medial part of the clavicle could lead to posterior dislocation of the joint . Indirect lateral compressive forces that affect the shoulder could rupture the anterior capsule and ligaments via the lever effect of the clavicle and can potentially result in anterior sternoclavicular joint dislocation [7, 15]. Closed reduction is the first choice for the treatment of anterior sternoclavicular joint dislocation, but it is usually unsatisfactory due to ligamentous rupture, which makes the joint unstable . The sternoclavicular joint is the only bony articulation between the axial skeleton and upper extremity, and movement at the joint, which is produced by the transmission of the movements of the scapula on the chest wall, can occur passively in three planes [1, 15]. During shoulder abduction, the sternoclavicular joint can move in the coronal and anteroposterior planes. Therefore, preservation of micromotion in the sternoclavicular joint has a significant effect on the postoperative range of glenohumeral joint motion . According to our research, patients in the LP group had limited movement of the sternoclavicular joint; therefore, glenohumeral joint motion was significantly limited relative to that of those in the AJHP group.
There are many important thoracic structures are located posterior to the sternoclavicular joint [14, 15]. The fact that these complex structures surround the sternoclavicular joint implies that dislocation could cause serious trauma, such as rupture of blood vessels, nerve injury, pleura rupture, lung rupture, and mediastinum organ injury. Additionally, operations on the joint require increased caution. In the LP group, drilling and screwing on the sternum could increase the risk of rupture or injury to mediastinal structures, although such complications were not observed in this study.
Comparing the incisions used to surgically treat both groups, in the AJHP group, a small part of the sternal manubrium was exposed, which was sufficient for plate insertion. However, in the LP group, most parts of the sternal manubrium, and even the mesosternum, was exposed to facilitate fixation of the plate and screws. Due to the shorter incision and smaller number of screws needed, blood loss in the AJHP group was significantly lower than that in the LP group. In addition, LP bending, drilling, and screwing on the sternum prolonged the duration of the operation in the LP group.
In our research, AJHP and LP were used for the treatment of sternoclavicular joint dislocation. Some advantages of AJHP treatment were as follows: (1) AJHP facilitates micromotion within a certain range between the hook and manubrium of the sternum, which is beneficial for glenohumeral joint motion; (2) the hook structure behind the sternal manubrium could reduce the risk of mediastinal structure rupture during drilling and screwing; and (3) the AJHP operation method requires a shorter incision, produces less blood loss, and has a shorter operation time.
However, there are some disadvantages of this study, such as the following: (1) the structure of the AJHP is not suitable for the anatomical structure of the sternoclavicular joint, and the plate is not in line with the joint; (2) there is no special screw hole available for sternoclavicular joint dislocation with medial clavicle fracture; (3) for treatment with LP, the repetitive stress of joint micromotion may cause loosen or break of the plate, so the LP should be removed early but most of them were removed with 1 year or longer after surgery in our study; (4) compared with LP, the hook structure of AJHP facilitates micromotion within a certain range, and reduces the probability of plate loosen or break. However, risk of hook cutting through the sternum still exists due to the sharpness of the hook of the plate when the AJHP is used to treat patients with anterior sternoclavicular joint dislocation although the case has not been found in our study; and (5) AJHP might provide good treatment outcomes in patients with anterior sternoclavicular joint dislocation in this study, but it might carry risks to penetrate the mediastinal structures in patients with posterior dislocation of sternoclavicular joint. (6) there is still no guideline for the treatment of sternoclavicular joint dislocation, the treatments of AJHP and LP are experimental, and patients should be informed the disadvantages of using AJHP or LP clearly, such as cutting through the sternum, vascular injury and reoperation . Based on these disadvantages, the current AJHP needs to be promoted in these details in the future, for example, the time of removing AJHP.