Shoulder Separation (AC Joint Separation)

What is a separated shoulder?

Separated shoulder, also known as AC joint separation occurs from a direct fall on or blow to the shoulder. This injury accounts for 9%-12% of shoulder injuries. Continue reading to learn more about recognizing and treating AC joint separation.

Understanding the anatomy

Three bones form the shoulder joint: the humerus (upper arm bone), the scapula (shoulder blade), and the clavicle (collarbone).  The AC joint, short for acromioclavicular joint, is where the clavicle meets the highest portion of the scapula, the acromion, and is held together by the acromioclavicular (AC) ligament and coracoclavicular (CC) ligament.

Who gets AC joint separation?

This most often occurs in men in their 20’s who participate in contact sports like football, hockey, and wrestling.  However, it can occur in anyone with a traumatic injury to the shoulder.

What causes AC joint separation?

AC separations often occur from falling directly onto the shoulder.  The force of falling on the shoulder injures the ligaments that connect the clavicle and acromion by either a sprain (stretch) of the ligament or a tear.  The force of the fall determines the severity of the injury. When the ligament is torn, the clavicle separates from the acromion; the clavicle will then elevate and the acromion drops due to the weight of the arm.  This results in a bump over the top of the shoulder.

AC separations can also occur from an indirect injury like falling on an outstretched arm or elbow pushing the humeral head into the acromion.

What are the symptoms of AC joint separation?

Usually there is an injury resulting in pain in the shoulder and then one would notice a bump over the top of the shoulder.  There are grades to separation ranging from 1-6; with increasing in grade you can expect increase in pain and deformity. Patients will also experience pain and popping with overhead range of motion and cross body range of motion and might even experience lack of range of motion in these directions.

What are the grades of AC joint separation?

Grade I or II/ Mild separation:  sprain of the AC ligament with no or minimal movement of the clavicle from the acromion.  This is the most common AC joint separation, occurring twice as often than higher grades.

Grade III-IV/ Moderate separation: tearing of the AC ligament with sprains of the CC ligament.  There is significant noticeable elevation of the clavicle at this point.

Grade V-VI/ severe separation: complete tears of both the AC ligament and CC ligament, resulting in obvious elevation of clavicle.

Diagnosis of AC joint separation

When seeing an orthopaedic surgeon we can diagnose AC joint separation with history and physical exam.  History will most likely include direct injury to the shoulder. Most patients on physical exam will be tender to palpation over the AC joint with a possible elevated clavicle.  X-ray is used to confirm diagnosis and determine the grade of separation, which will also help rule out any other possible injury to the shoulder like fracture of the humerus, scapula or clavicle.  There is a specific x- ray technique used for AC joint injury and normally both AC joints will be imaged for comparison.

Treatment of AC Joint Separation

Treatment depends on your grade or severity of separation.

Grade I and II:   This is a mild injury, so treatment is usually conservative and patients recover quickly.  You will start with rest, ice, NSAIDs and possible sling for comfort. Physical therapy is started for range of motion and strengthening fairly quickly.

Grade III:   This is a moderate injury to the AC joint.  Treatment for this is more controversial. Some experts recommend non-operative treatment with rest, ice, sling and NSAIDs.  If your pain persists or deformity is concerning, surgery could be considered. Other experts recommend surgery for athletes or laborers for Grade III separations. Grade III separation takes a total of 6-12 weeks to fully heal before returning to sport or heavy overhead work.

Grade IV, V, VI: This is the severe injury to the AC joint.  These usually require surgical treatment, either open or arthroscopic procedures.   Some chronic injuries require use of a graft to reconstruct the ligaments that are torn.  The purpose of surgery is to realign the clavicle to the acromion. Surgical patients are placed in a sling for six weeks with no overhead activity.   After six weeks, the sling is removed and patients start physical therapy for range of motion and strengthening. Total healing time for this severity of injury can be up to 3 – 6 months.

If you have concerns about Shoulder Separation, schedule an appointment with one of our Shoulder specialists.