Os Acromiale

What is an Os Acromiale

Os acromiale is a growth defect in a bone (acromion) in the shoulder joint. The acromion is at the top of each shoulder, at the tip of the shoulder blade. As the acromion develops, four sections of cartilage (growth plates) must join together and harden into bone (fusion).

An os acromiale occurs when one of the accessory ossification centers of the acromial process fails to completely fuse.

The acromial ossification centers appear by age 15 and usually fuse by 25 years of age.

On MRI, it is easiest to identify this on the superior-most images of the axial images. An os acromiale may cause impingement by narrowing the subacromial space.

In most people, fusion occurs by age 18–25. If you have os acromiale, the growth plates are not completely fused. This means that when certain shoulder muscles are used, they can pull on a weak spot in the acromion and cause pain.

Os acromiale may occur in one shoulder or both shoulders. This condition can narrow the space that that the rotator cuff tendon (supraspinatus) passes through, and pinch the tendon (impingement).

What are the causes?

This condition is caused by incomplete fusion of the growth plates in the acromion. The cause of incomplete fusion is not known.

What increases the risk?

The following factors may make you more likely to experience pain as a result of os acromiale:

• Doing physical activity that involves repetitive overhead arm movements. This includes:
  • Sports that involve throwing.
  • Tennis.
  • Swimming.
  • Volleyball.
• Injury (trauma), such as getting hit, falling onto your shoulder, or breaking a fall with your hands.

What are the symptoms?

This condition may not cause any symptoms. If you have symptoms, they may include:

• Pain on the top of the shoulder. Pain may get worse when you do overhead arm movements or when you lie on your side.
• Decreased range of motion.
• Tenderness when the affected area is touched.
• Weakness.

How is this diagnosed?

If you do not have symptoms, this condition often gets diagnosed when you have a shoulder X-ray for another reason. If you have symptoms, your health care provider may diagnose this condition based on:

• Your symptoms.
• Your medical history.
• A physical exam.
• Whether an injection of numbing medicine in the space under your acromion relieves your pain.
• Imaging tests, such as:
  • X-rays.
  • MRI.
  • Ultrasound.

How is this treated?

Treatment for this condition may include:

• Resting your shoulder and avoiding all activities that cause pain or put stress on the shoulder.
• Icing your shoulder.
• NSAIDs to help reduce pain and swelling.
• One or more injections of medicines to numb the affected area and reduce inflammation.
• Physical therapy.
• Surgery. This may be needed if other treatments do not help after 6 months.

Follow these instructions at home:

Managing pain, stiffness, and swelling

• If directed, apply ice to the injured area.
  • Put ice in a plastic bag.
  • Place a towel between your skin and the bag.
  • Leave the ice on for 20 minutes, 2–3 times a day.
• Move your fingers often to avoid stiffness and to lessen swelling.
• Raise (elevate) the injured area above the level of your heart while you are lying down.

Activity

• Return to your normal activities as told by your health care provider. Ask your health care provider what activities are safe for you.
• Do exercises as told by your health care provider.

General instructions

• Do not drive or operate heavy machinery while taking prescription pain medicine.
• Do not use any tobacco products, such as cigarettes, chewing tobacco, and e-cigarettes. Tobacco can delay bone healing. If you need help quitting, ask your health care provider.
• Take over-the-counter and prescription medicines only as told by your health care provider.
• Keep all follow-up visits as told by your health care provider. This is important.

Contact a health care provider if:

• Your symptoms have not improved after 6 months of home care.
• Your symptoms are getting worse even though you are doing home care.

Os Acromiale Rehabilitation

Ask your health care provider which exercises are safe for you. Do exercises exactly as told by your health care provider and adjust them as directed.

It is normal to feel mild stretching, pulling, tightness, or discomfort as you do these exercises, but you should stop right away if you feel sudden pain or your pain gets worse. Do not begin these exercises until told by your health care provider.

Strengthening exercises

These exercises build strength and endurance in your shoulder. Endurance is the ability to use your muscles for a long time, even after they get tired.

Exercise A: Scapular protraction, supine

1. Lie on your back on a firm surface. Hold a __________ weight in your left / right hand.
2. Raise your left / right arm straight into the air so your hand is directly above your shoulder joint.
3. Push the weight into the air so your shoulder lifts off of the surface that you are lying on. Do not move your head, neck, or back.
4. Hold for __________ seconds.
5. Slowly return to the starting position. Let your muscles relax completely before you repeat this exercise.

Repeat __________ times. Complete this exercise __________ times a day.

Exercise B: Scapular retraction

1. Sit in a stable chair without armrests, or stand.
2. Secure an exercise band to a stable object in front of you so the band is at shoulder height.
3. Hold one end of the exercise band in each hand.
4. Squeeze your shoulder blades together and move your elbows slightly behind you. Do not shrug your shoulders while you do this.
5. Hold for __________ seconds.
6. Slowly return to the starting position.

Repeat __________ times. Complete this exercise __________ times a day.

Exercise C: Shoulder extension

1. Sit in a stable chair without armrests, or stand.
2. Secure an exercise band to a stable object in front of you so the band is above shoulder height.
3. Hold one end of the exercise band in each hand.
4. Straighten your elbows and lift your hands up to shoulder height.
5. Squeeze your shoulder blades together and pull your hands down to the sides of your thighs. Stop when your hands are straight down by your sides. Do not let your hands go behind your body.
6. Hold for __________ seconds.
7. Slowly return to the starting position.

Repeat __________ times. Complete this exercise __________ times a day.

Exercise D: Internal rotation

1. Sit in a stable chair without armrests, or stand.
2. At elbow height on your left / right side, secure an exercise band to a stable object.
3. Place a soft object, such as a folded towel or a small pillow, between your left / right upper arm and your body so your elbow is a few inches (about 10 cm) away from your side.
4. Grasp the end of the exercise band in your left / right hand.
5. Keeping your upper arm steady, move your forearm across your body toward your abdomen. Keep your body steady so the movement is only coming from your shoulder.
6. Hold for __________ seconds.
7. Slowly return to the starting position.

Repeat __________ times. Complete this exercise __________ times a day.

Exercise E: External rotation

1. Lie down on your left / right side.
2. Place a small pillow or a rolled-up towel between your left / right upper arm and your body.
3. Bend your left / right elbow to an “L” shape (90 degrees) so your hand is palm-down on your abdomen.
4. Squeeze your shoulder blade back toward your spine.
5. Keeping your upper arm against the pillow or towel:
   1. Move (pivot) your forearm and your hand away from your abdomen and toward the ceiling.
   1. Keep your elbow bent at 90 degrees.
6. Hold for __________ seconds.
7. Slowly return to the starting position.

Repeat __________ times. Complete this exercise __________ times a day.