Impingement Syndrome
 GENERAL
The shoulder is the most mobile joint in the body. Its remarkable range
of motion is achieved by a design with less stability than a ball and socket
joint like the hip. The shoulder resembles a golf ball sitting on a tee. It
falls off easily (dislocates) and the normal restraints for this are the capsule
with its incorporated ligaments, and the rotator cuff. The rotator cuff is
a sleeve of tendons whose muscles originate primarily from the shoulder blade
(scapula). The tendons of these muscles insert in a ring at the perimeter of the humeral head (ball of the joint). These muscles are so named
because they provide rotational motion of the arm. They also act to hold
the head of the humerus down, by their general downward inclination from the
humerus to the scapula. The deltoid is the most superficial muscle over
the shoulder, and covers it like a hood. It elevates the arm but at the
same time, elevates the humeral head against the acromion. The deltoid
originates from the acromion (shoulder cap), the clavicle, and the spine of the
scapula, and inserts halfway down the upper arm.
SYMPTOMS
Impingement occurs when the rotator cuff tendons are pinched between the
acromion and the humeral head. This causes characteristic anterior
shoulder pain which is "tooth-ache" like in nature. Pain
generally radiates down the front of the upper arm. Overhead activities
and reaching at arms reach, aggravate this condition, and reaching behind the
back is painful. Neck pain or scapular pain may result with associated muscle spasm. Night-time awakening is common.
CAUSES
Any force which causes recoil of the humeral head against the acromion
increases symptoms. Throwing or racquet sports may increase symptoms.
Shoulder instability, which allows for abnormal motion of the ball relative to
the cup (subluxation) may also cause impingement. Repetitive overhead arm
use, reaching, or scrubbing motions with the arm may aggravate symptoms.
Normally a bursa (sac) is interposed between the rotator cuff and the acromion.
This lubricates the motion of the tendons minimizing friction and wear.
Normally, the bursa is thin and resembles a plastic bag with a few drops of oil
inside. Bursitis or inflammation of the sac causes thickening and less
space for the tendons. This causes more symptoms of impingement with catching
and crunching sounds on overhead motion of the arm. This occurs as the bursa is pinched between the acromion and humerus. With prolonged
inflammation, the rotator cuff tendons are rubbed on directly and slowly are
abraded. Eventually this may result in a rotator cuff tear. Here the
tendons rip from their attachment into the humeral head. Early this may be
painful with little functional loss. A large tear, however, is often very
debilitating and causes weak rotational strength and limited arm elevation.
The symptoms of impingement on physical exam are fairly characteristic. A
special x-ray view is also highly correlated with symptoms. Cervical spine
problems or arthritis between the acromion and clavicle may mimic the condition.
TREATMENT
Treatment is in three stages. Initially, rest from irritating
activities and oral anti-inflammatory medicine helps relieve bursal swelling.
Rotator cuff strengthening helps hold the humerus down and open the tendon
space. If this is not effective, subacromial steroid injection may act
directly in the space to rapidly decrease inflammation. More than 80% of
patients treated by these means improve to their satisfaction. If symptoms
are not relieved, and conservative measures are exhausted, Arthroscopic
decompression may be performed to remove the bony impingement against the
rotator cuff. This is performed as an outpatient procedure, and has an 85%
good to excellent result in carefully selected patients. Those with
associated rotator cuff tears may be treated arthroscopically with simultaneous
repair of the cuff through a small incision directly over the tear. If the
tear is too large, however, a standard operative anterior approach is required.
Generally surgery is performed as an outpatient procedure, however with large
tears overnight hospitalization may be required.
REHABILITATION
After Arthroscopy
describes basic surgical aftercare. The shoulder is
highly susceptible to postoperative stiffness. It is important to maintain a
normal range of motion after surgery. When Arthroscopic decompression is only
needed, rapid return of motion and strength are encouraged without restrictions.
With rotator cuff repair, passive elevation only is allowed for 6 to 8 weeks
while tendon healing is in progress. Muscle strengthening is then
encouraged beginning with rotator cuff strengthening.
SUMMARY
In summary, impingement syndrome is a mechanical pinching of the rotator cuff
increased by certain activities and anatomic variation. Conservative measures
generally relieve symptoms in about 85% of patients to their satisfaction.
If this fails, surgical intervention improves pain and disability in a high
percentage of patients, and often can be performed on an out-patient basis.
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