SHOULDER SEPARATION – PART 1: ANATOMY AND CLASSIFICATION
There are a number of muscles, tendons, and ligaments attaching to the bones of the shoulder (e.g. the scapula, humerus, and clavicle) that maintain the bones in a normal position to one another.
The acromioclavicular (AC) joint is the joint between the acromion (part of the scapula) and the end of the clavicle (collar bone). The AC joint is normally stabilized by the AC joint capsule, the acromioclavicular ligament, two coracoclavicular ligaments (i.e. conoid ligament, trapezoid ligament), and the surrounding shoulder muscles (i.e. deltoid, trapezius).
The AC joint is most commonly injured due to falls directly onto the shoulder and can result in a spectrum of injury patterns involving the above-mentioned stabilizing structures. These injuries, sometimes referred to as a “shoulder separation,” are classified based on their appearance on x-rays, from grade I through grade VI. Minor AC separations (grades I and II) maintain a significant degree of stability, do not typically result in a visible deformity, and often lead in minimal discomfort in the short-term, whereas the more severe injuries (grades III-VI) result in higher degrees of instability and deformity, leading to greater pain and disability. Additional shoulder injuries (e.g. labral tears) are also more likely to occur in these higher grade injuries.
If you are experiencing shoulder separation or would like to learn more don’t hesitate to reach out.
Nels Sampatacos, MD
Orthopedic Surgeon and Sports Medicine Specialist
