What is the AC
Joint in the shoulder?
The top
of the wing bone or scapula is the acromion. The joint formed where the
acromion connects to the collar bone or clavicle is the AC joint. Usually
there is a protuberance or bump in this area, which can be quite large
in some people normally. This joint, like most joints in the body, has
a cartilage disk or meniscus inside and the ends of the bones are covered
with cartilage. The joint is held together by a capsule, and the clavicle
is held in the proper position by two heavy ligaments called coracoclavicular
ligaments.
How is the AC Joint
usually injured?
The AC joint is injured most often when one falls directly on the
point of the shoulder. The trauma will separate the acromion away from
the clavicle, causing a sprain or a true AC joint dislocation. In a mild
injury, the ligaments which support the AC joint are simply stretched
(Grade I), but with more severe injury, the ligaments can partially tear
(Grade II) or completely tear (Grade III). In the most severe injury,
the end of the clavicle protrudes beneath the skin and is visible as a
prominent bump.
How is an AC Joint
separation diagnosed?
Most often the clinical exam will demonstrate tenderness or bruising around
the top of the shoulder near the AC joint, and the suspected diagnosis
can be confirmed using an x-ray, which compares the injured side with
the patient's other joint.
What is the proper
treatment for a sprained AC Joint?
When a joint is first sprained, conservative treatment is certainly the
best. Applying ice directly to the point of the shoulder is helpful to
inhibit swelling and relieve pain. The arm can be supported with a sling
which also relieves some of the weight from the shoulder. Gentle motion
of the arm can be allowed to prevent stiffness, and exercise putty is
very helpful to improve function of the elbow, wrist, and hand, but any
attempts at vigorous shoulder mobilization early on will probably lead
to more swelling and pain.
How long does it
take for a shoulder separation to heal?
Depending on how severe the injury is, it may heal adequately in two to
three weeks. In severe cases, the shoulder may not heal without surgery.
When and why is
surgery necessary for AC Joint separations?
Usually surgery is reserved for those cases where there is residual pain
or unacceptable deformity in the joint after several months of conservative
treatment. The pain can occur with direct pressure on the joint, such
as with straps from underwear or work clothing. Sometimes there will be
catching, clicking, or pain with overhead activities, such as lifting,
throwing, or reaching. Finally, in some people with very thin skin and
very little muscular and soft tissue padding above their shoulders, the
prominent clavicle after the separation may be considered unattractive,
since the shoulder can appear to be unbalanced.
Are there other causes
of AC Joint pain and disability?
Arthritis can occur
as an isolated event in the AC joint, causing stiffness, aching, and sometimes
swelling. Another condition called DCO, or distal clavicle osteolysis,
gives a similar picture, usually in young people who lift heavy weights.
This is called "Weightlifter's Shoulder."
What type of surgery
can repair AC Joint problems?
The simplest type of surgery for AC joint injury involves resection or
removal of the end of the clavicle using arthroscopic (mini-surgical)
techniques (called a Mumford procedure). If the joint becomes painful
because of DCO (weightlifter's shoulder) or arthritis, or the separation
is only minor, this technique can be very satisfactory. When the joint
is severely displaced, then a more complex procedure is needed to restore
the position of the clavicle. Usually this operation, called a Weaver-Dunn
procedure, is done using a two-inch incision over the joint. The end of
the clavicle is removed, and ligament is transferred from the underside
of the acromion into the cut end of the clavicle to replace the ligaments
torn during the dislocation. Soon an arthroscopic procedure should be
available to restore the position of the joint, but at this point, only
open surgery techniques are available.
What is the postoperative
treatment and rehabilitation?
Postoperatively, treatment depends on the type of surgery performed. Usually,
when the Mumford procedure is performed using arthroscopic techniques, the
arm can be treated with a sling. Bathing is allowed in three days' time,
and elbow, wrist, and hand exercises are begun immediately. Lifting is limited
for three weeks, but following that, progressive exercise and motion activities
proceed as the symptoms allow.
When a Weaver-Dunn
procedure (rebuilding of the torn ligaments) is needed, approximately
two or three weeks is added to the immobilization time before motion exercises
are begun. This time allows the ligament to heal. Otherwise, the exercise
program is the same as that for the Mumford procedure above.
