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Q: My friend hurt herself, and her doctor said she had separated her shoulder. How is this different from a shoulder dislocation?
A: The ball shaped head of the humerus (the upper arm bone) fits comfortably into the glenoid fossa (the cup shaped part of the scapula), creating the ball and socket shoulder joint. Part of the stabilization of the scapula is its anchoring to the clavicle (collar bone) via the acromion (the part of the scapula that starts on its outer end, wraps over the top of the head of the humerus and then turns back towards the clavicle); they are held together by the acromioclavicular (AC) ligament. In addition, many other ligaments strengthen the shoulder (including the coracoclavicular (CC) ligaments between the coracoid process of the scapula and the collar bone), tendons connect the bones to the four rotator cuff muscles and cartilage acts as a cushion between the bones. All together this makes the shoulder the most versatile joint in the body, allowing the arm to have an amazing range of motion while maintaining great strength.
The tradeoff for this amazing versatility is that the shoulder may be a bit unstable; it is the most commonly dislocated joint in the body (not including fingers and toes), accounting for over half of all major joint dislocations. When the shoulder dislocates the head of the humerus (the ball) slips out of the glenoid fossa (the socket).
A shoulder separation is actually a misnomer; it is more accurately called an acromioclavicular (AC) joint injury, involving the AC and/or CC ligaments. AC joint injuries are usually caused by direct trauma to the area, but occasionally can be caused by indirect force, such as from a fall onto an outstretched hand.
An AC joint injury is diagnosed based on the history and physical examination, along with specialized x-rays (when indicated); when severe injury is suspected an MRI may be ordered. The prognosis and treatment needed depend on the grade (severity) of the injury.
Grade I injuries have tenderness over the AC joint from the sprain/partial tear of the AC ligament (the CC ligament is not involved); no deformity is typically identified. Conservative treatment with non-steroidal anti-inflammatory pain medications (NSAIDs), ice (to reduce swelling) and rest (usually with an arm sling), typically leads to resolution of the symptoms within days to a couple of weeks.
Grade II separation is characterized by a complete tear of the AC ligament, and a sprain/partial tear of the CC ligament. The tenderness over the AC joint is accompanied by significant swelling, so a deformity (a lump from swelling and/or misalignment of the acromion and clavicle) is often identified. Treatment is again conservative, although physical therapy (stretching and/or strengthening exercises) may be required as well. It will often take a couple of weeks to a month for complete resolution of symptoms, allowing for a complete return to normal activities.
Q: My friend hurt herself, and her doctor said she had separated her shoulder. How is this different from a shoulder dislocation?
A: The ball shaped head of the humerus (the upper arm bone) fits comfortably into the glenoid fossa (the cup shaped part of the scapula), creating the ball and socket shoulder joint. Part of the stabilization of the scapula is its anchoring to the clavicle (collar bone) via the acromion (the part of the scapula that starts on its outer end, wraps over the top of the head of the humerus and then turns back towards the clavicle); they are held together by the acromioclavicular (AC) ligament. In addition, many other ligaments strengthen the shoulder (including the coracoclavicular (CC) ligaments between the coracoid process of the scapula and the collar bone), tendons connect the bones to the four rotator cuff muscles and cartilage acts as a cushion between the bones. All together this makes the shoulder the most versatile joint in the body, allowing the arm to have an amazing range of motion while maintaining great strength.
The tradeoff for this amazing versatility is that the shoulder may be a bit unstable; it is the most commonly dislocated joint in the body (not including fingers and toes), accounting for over half of all major joint dislocations. When the shoulder dislocates the head of the humerus (the ball) slips out of the glenoid fossa (the socket).
A shoulder separation is actually a misnomer; it is more accurately called an acromioclavicular (AC) joint injury, involving the AC and/or CC ligaments. AC joint injuries are usually caused by direct trauma to the area, but occasionally can be caused by indirect force, such as from a fall onto an outstretched hand.
An AC joint injury is diagnosed based on the history and physical examination, along with specialized x-rays (when indicated); when severe injury is suspected an MRI may be ordered. The prognosis and treatment needed depend on the grade (severity) of the injury.
Grade I injuries have tenderness over the AC joint from the sprain/partial tear of the AC ligament (the CC ligament is not involved); no deformity is typically identified. Conservative treatment with non-steroidal anti-inflammatory pain medications (NSAIDs), ice (to reduce swelling) and rest (usually with an arm sling), typically leads to resolution of the symptoms within days to a couple of weeks.
Grade II separation is characterized by a complete tear of the AC ligament, and a sprain/partial tear of the CC ligament. The tenderness over the AC joint is accompanied by significant swelling, so a deformity (a lump from swelling and/or misalignment of the acromion and clavicle) is often identified. Treatment is again conservative, although physical therapy (stretching and/or strengthening exercises) may be required as well. It will often take a couple of weeks to a month for complete resolution of symptoms, allowing for a complete return to normal activities.
Grade III injuries have complete tears of both the AC and CC ligaments; there is typically a significant deformity from the disruption of the AC joint, which may be more evident when the joint is stressed (for example from pulling down on the arm). Conservative treatment (including physical therapy when the patient can tolerate it) is usually initiated, with the expectation that complete recovery may take months. For patients who worsen or fail to improve despite treatment, surgery may be considered.
The most severe grades of injury (Grade IV, V and VI) not only have tears of the AC and CC ligaments, but also include significant displacement of the clavicle. Grade IV has the clavicle displaced into/through the trapezius muscle, Grade V is characterized by compromise of the musclular attachments of the distal clavicle, and Grade VI has complete disruption of the musculature supporting the clavicle. All these more advanced grades of injury usually require surgical intervention.
If you suffer an injury that results in tenderness and/or a lump by the outside end of the collar bone (on top inside part of the shoulder), you may have an AC joint injury. You should be seen by a physician to be evaluated for the extent of the injury so appropriate treatment can be initiated.
Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com.
