An acromioclavicular joint
separation, or AC separation, is a very frequent
injury among physically active people. In this injury the
clavicle (collar bone) separates from the scapula
(shoulder blade). It is commonly caused by a fall directly
on the "point" of the shoulder or a direct blow
received in a contact sport. Football players and cyclists
who fall over the handlebars are often subject to AC separations.
In general, most AC injuries
don't require surgery. There are certain situations, however,
in which surgery may be necessary. Most patients recover with
full function of the shoulder. The period of disability and
discomfort ranges from a few days to 12 weeks depending on
the severity of the separation. Disruption of the AC joint
results in pain and instability in the entire shoulder and
arm. The pain is most severe when the patient attempts
overhead movements or tries to sleep on the affected side.
shoulder is the most mobile joint in the human body, with
a complex arrangement of structures working together to provide
the movement necessary for daily life. Unfortunately, this
great mobility comes at the expense of stability. Several bones
and a network of soft tissue structures (ligaments, tendons,
and muscles), work together to produce shoulder movement.
They interact to keep the joint in place while it moves through
extreme ranges of motion. Each of these structures makes an
important contribution to shoulder movement and stability.
Certain work or sports activities can put great demands upon
the shoulder, and injury can occur when the limits of movement
are exceeded and/or the individual structures are overloaded.Click
here to read more about shoulder structure.
is an AC joint separation?
AC joint separation, often called a shoulder separation, is
a dislocation of the clavicle from the acromion. This injury
is usually caused by a blow to the shoulder, or a fall in
which the individual lands directly on the shoulder or an
outstretched arm. AC joint separations are most common
in contact sports, such as football and hockey.
does the inside of the shoulder look like?
The severity of an acromioclavicular
joint injury depends on which supporting structures are damaged,
and the extent of that damage. Tearing of the acromioclavicular
ligament alone is not a serious injury, but when the coracoclavicular
ligaments are ruptured, the whole shoulder unit is involved,
thus complicating the dislocation.
Simple AC injuries are classified in three grades ranging
from a mild dislocation to a complete separation:
- A slight displacement of the joint. The acromioclavicular
ligament may be stretched or partially torn. This is
the most common type of injury to the AC joint.
- A partial dislocation of the joint in which there may
be some displacement that may not be obvious during a
physical examination. The acromioclavicular ligament is
completely torn, while the coracoclavicular ligaments
- A complete separation of the joint. The acromioclavicular
ligament, the coracoclavicular ligaments, and the capsule
surrounding the joint are torn. Usually, the displacement
is obvious on clinical exam. Without any ligament support,
the shoulder falls under the weight of the arm and the
clavicle is pushed up, causing a bump on the shoulder.
There are a total of six grades
of severity of AC separations. Grades I-III are the most common.
Grades IV-VI are very uncommon and are usually the result
of a very high-energy injury such as one that might occur
in a motor vehicle accident. Grades IV-VI are all treated
surgically because of the severe disruption of all the ligamentous
support for the arm and shoulder.