| Description
The AC joint is where the collarbone (clavicle)
meets the highest point of the wingbone (acromion).
Injuries to this area can include wear & tear over time (AC
Joint arthritis) or a specific injury (separations) to the
joint. A shoulder separation is not truly an injury
to the shoulder joint. The injury actually involves the
acromioclavicular joint (also called the AC joint).
Mechanism of injury
The most common cause for a separation of the AC joint
is from a fall directly onto the shoulder. The fall injures
the ligaments that surround and stabilize the AC joint.
If the force is severe enough, the ligaments attaching
to the underside of the clavicle are torn. This causes the
"separation" of the collarbone and wingbone, the wingbone
actually moves downward from the weight of the arm. This
creates a "bump" or bulge above the shoulder.
The injury can range from a little change in
configuration with mild pain, to quite deforming and very
painful. Good pain-free function often returns even with a
lot of deformity. The greater the deformity, the longer it
takes for pain-free function to return.
- A mild shoulder separation involves a sprain of the
AC ligament that does not move the collarbone and looks
normal on X-rays.
- A more serious injury tears the AC ligament and
sprains or slightly tears the coracoclavicular (CC)
ligament, putting the collarbone out of alignment to some
extent.
- The most severe shoulder separation completely tears
both the AC and CC ligaments and puts the shoulder joint
noticeably out of position.
Diagnosis
The injury is easy to identify when it causes deformity.
When there is less deformity, the location of pain and
X-rays help the doctor make the diagnosis. Sometimes having
the patient hold a weight in the hand can increase the
deformity, which makes the injury more obvious on X-rays.
Treatment Options
Nonsurgical treatments such as a sling, cold packs and
medications can often help manage the pain. Sometimes a
doctor may use more complicated supports to help lessen AC
joint motion, reduce the deformity and lessen pain.
Most people return to near full function with this
injury, even if there is a persistent, significant
deformity. Some people have continued pain in the area of
the AC joint even with only a mild deformity. This may be
due to:
- Abnormal contact between the bone ends when the joint
is in motion
- Development of arthritis
- Injury to a disk-like piece of cushioning cartilage
that is often found between the bone ends of this joint
It is worthwhile to wait and see if reasonable function
returns without surgical treatment.
AC Joint arthritis is often treated initially with
conservative measures such as taping, oral antiinflamatory
medications, or cortisone injections into and around the AC
joint.
Treatment Options: Surgical
Surgery can be considered if pain persists or the
deformity is severe. A surgeon might recommend trimming
back the end of the collarbone so that it doesn't rub
against the AC. Where there is significant deformity,
reconstructing the ligaments that attach to the underside
of the collarbone is helpful. This type of surgery works
well even if it is done long after the problem started.
Whether treated conservatively or with surgery, the
shoulder will require rehabilitation to restore and rebuild
motion, strength and flexibility.
Surgical treatment of AC joint arthritis consists of
arthroscopic surgery to remove a small portion of the
clavicle - thus eliminating the bone on bone contact which
causes the pain with arthritis.
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