Dec. 9, 2005

As the title implies, the acromioclavicular (A-C) separation which is seen frequently in ice hockey is no different than the A-C injury seen in other contact sports. What does differ, at times, is the mechanism of injury that produces the separation in a hockey player. Before discussing specifics, it is beneficial to review some of the basic anatomy of the shoulder joint and the acromioclavicular joint so that players, coaches and parents have a basic understanding when discussing the injury with their athletic trainer or physician.

The acromioclavicular joint is where the clavicle, or collarbone, meets the top of the shoulder blade, called the acromion. This joint is what is injured when someone separates their shoulder. What most athletes consider as the `shoulder joint' is where the upper arm bone, the humerus, meets the glenoid or shoulder socket. This joint is what is injured when someone dislocates their shoulder. Despite the fact that the media frequently interchange these two terms, they are quite different injuries that occur in different areas of the shoulder complex.

The A-C joint is stabilized by the acromioclavicular ligament which runs between the acromion and is the primary stabilizer for the joint. Other ligaments that help to hold the collarbone down and the shoulder blade up are the coracoclavicular ligaments that extend from another part of the shoulder blade (the coracoid) up to the collarbone. (see diagram)

Mechanism

The normal mechanism of injury for a separation is a direct blow to the top of the shoulder. This might occur when a football player gets low and takes on an opponent with a shoulder. Appropriate shoulder pads can help minimize this mechanism of injury. An A-C separation can also occur with a fall onto the crest of the shoulder as might occur when going over the handle bars of a bicycle or being flipped over another player when heading a ball in soccer. In ice hockey, a common mechanism for the A-C injury is a compressive force that squeezes the body from the side. Picture a hockey player skating alongside the boards and being checked hard from the side by an opponent. This slams the player into the glass causing one shoulder to be compressed in by the glass and the other shoulder to be compressed in by the blow from the opponent. A separation may occur to either shoulder (or both). In this case the shoulder pads do protect the cap of the shoulder from normal blows and bruising, but do not, and can not, prevent this lateral (sideways) force. This resultant injury is very similar to that sustained with a `normal' mechanism of injury with only minor differences which will be outlined below.

Injury Grading

Most A-C separations that occur in athletics can be graded I, II or III, (mild, moderate or severe). There are actually six grades of severity of A-C separations but grades four through six generally require extensive trauma as from a vehicular accident. A grade I separation is the most common and is characterized by a stretching or mild tearing of the acromioclavicular ligament. Other ligaments are unaffected and the collarbone does not lift as does with a more significant injury. With a grade II injury, the acromioclavicular ligament is usually completely torn and the coracoclavicular ligaments may be stretched. The collarbone will lift somewhat although this may not be evident on examination due to swelling around the A-C joint which will obscure the elevated collarbone. A grade III injury is more severe with complete tearing of the acromioclavicular ligament as well as significant tearing of the coracoclavicular ligaments. This lack of support between the shoulder blade and the collarbone causes the shoulder complex to drop and the collarbone to lift. This is usually quite obvious on physical exam. With the ice hockey mechanism of lateral compression, there is at times injury to both the acromioclavicular ligament and the coracoclavicular ligaments, even with a milder injury. Along with the A-C injury, the hockey mechanism will often cause another mild injury at the end of the collarbone that meets the breastbone, or sternum. This joint is called the sternoclavicular (S-C) joint and is aggravated when the sideways force impacts the hockey player and causes a transfer of force down the collarbone which causes trauma of the S-C joint.

Signs and Symptoms

Symptoms of an A-C injury vary depending on the patient and the severity of the injury. With a grade I injury, expect tenderness, along with the possibility of mild swelling on the top of the shoulder at the A-C joint, and at the end of the collarbone. There will be some pain with arm motion and some weakness as well. However with this injury, there is no tenderness along the coracoclavicular ligaments except perhaps when you have the `ice hockey' mechanism.

A grade II injury will exhibit swelling, and more pain with arm motion. The A-C joint will be very tender and the end of the clavicle may be slightly elevated. There will be weakness at the shoulder, especially when lifting the arm away from the body to the side or to the front. The coracoclavicular ligaments may be tender as well. Pushing down on the midpoint of the collarbone may cause the end of the collarbone to move up and down.

A Grade III injury will be quite painful. The athlete will not be able to move the shoulder and will support the injured arm with their other arm, usually grasping the injured arm at the elbow in an attempt to lift up the injured shoulder. The entire top and front of the shoulder are very tender, and swelling will be obvious. The shoulder will also look deformed since the collarbone will be quite elevated (and very unstable) and the shoulder complex will drop down.

This will often give the top of the shoulder a `step-off' look between the raised collarbone and the dropped shoulder.

Care and Treatment

Any injury of this nature should be evaluated by a medical professional with experience in diagnosing and treating sports shoulder injuries. The clinician will evaluate and rule out other injuries that might share some similar signs and symptoms. This would include a dislocated shoulder or a fractured collarbone. Most physicians will obtain a regular x-ray to aid in the diagnosis although this may not be necessary in a Grade I injury.

Standard care for Grade I-III injuries includes immediate application of ice, as well as fitting the athlete with an arm sling to both stabilize and lift the arm, thus taking the downward pressure off the A-C joint. In some Grade III injuries, a special sling will be worn that both lifts the arm up and pushes down on the collarbone. This can be applied as soon as the patient can tolerate the pressure on the collarbone.

Depending on the clinician, and on the severity of the injury, ice will be applied intermittently over the next two to five days. The sling will be used as needed for comfort, and therapy will commence as soon as the patient can tolerate. The focus of therapy will be the reduction of swelling, the return of normal shoulder motion and the return of shoulder strength.

During the acute stage after injury, and even for many weeks later, the athlete may have moderate discomfort when sleeping, especially when attempting to sleep on the affected side.

As therapy progresses, moist heat is generally used to facilitate the reduction of swelling and allow further rehabilitation. The clinician may recommend the use of anti-inflammatory medications throughout the injury and rehabilitation process.

In some severe Grade III injuries (and in many Grace IV-VI), surgery may become an option. However, research shows that conservative treatment is usually effective in Grades I-III. When surgery is deemed necessary, the orthopedic surgeon will usually perform some type of procedure that includes trimming the end of the collarbone and using some type of fixation for holding down the collarbone and supporting the shoulder complex.

Return to Play

The return-to-play decision must be made with the athlete's well-being as the single most important deciding factor. Consideration should be given to the athlete's ability to move the arm through a full range of motion. Strength is vitally important so that athletes can both protect themselves and be effective in their sport. Special custom padding (or shoulder pads) can be worn to protect the top of the shoulder. As noted before, shoulder pads can not prevent further A-C injury from the `ice hockey mechanism'. Even after return to play, it is not unusual for the athlete to experience periods of discomfort for up to several months.

Although the A-C separation is a debilitating injury in the acute stages, the success rate is very high for return-to-play at previous levels. Other than a permanent bump on the top of the shoulder, even Grade III injuries usually return to 100%!!!