Os Acromiale Info
Last reviewed
Patient-facing topic on os acromiale — failed fusion of an acromial ossification centre that may cause shoulder pain and contribute to subacromial impingement.
What you're feeling
You may feel pain in the top of your shoulder. This condition affects about 2.13% of patients with shoulder problems who need an MRI. The pain often comes from a tear in the rotator cuff, which is a group of muscles and tendons that move your arm. This tear happens because the extra bone piece moves abnormally and rubs against your other tissues.
Your pain might flare up after you do certain activities. It can also wake you up at night or hurt when you try to sleep on that side. Simple daily tasks can become difficult. You might struggle to reach behind your back to fasten a bra or tuck in a shirt. These movements put pressure on the area where the bone pieces do not fully join together.
If you have had shoulder replacement surgery, you might notice tenderness right over this bone piece. This happens in 1 out of 4 patients after the procedure. The good news is that this soreness usually goes away on its own over time for most people. Your surgeon will check your symptoms to decide if this extra bone piece is the main cause of your pain.
What's actually happening
Your shoulder has a small bone fragment called the os acromiale that hasn't fused to the main bone. This happens in about 2.13% of patients with shoulder problems needing an MRI. Think of this unfused spot as a loose gasket between two parts of your shoulder bone. Instead of moving as one solid piece, this loose fragment can rub and shift when you move your arm.
This abnormal motion often irritates the soft tissues nearby. The rotator cuff is a group of tendons that act like ropes to lift and rotate your arm. Because the loose bone moves strangely, it can pinch these tendons. This pinching, or impingement, often leads to a rotator cuff tear. In young athletes, this specific injury pattern is common and needs careful checking to confirm the diagnosis.
Sometimes this loose bone can get hurt after a fall or injury, though this is rare. If you have surgery for other reasons, like a reverse total shoulder replacement, you might feel local tenderness at this spot in 1 out of 4 patients. This soreness usually goes away on its own over time. Having this extra bone fragment does not seem to hurt your overall results from major shoulder replacement surgery.
What we can do about it
Most people start with self-care and physical therapy to manage pain. Your therapist will guide exercises to strengthen the shoulder muscles and improve movement. This approach aims to reduce friction where the extra bone piece sits. You should give this non-surgical plan a fair trial before considering other steps.
If pain persists, your surgeon may discuss medication or injections. Anti-inflammatory drugs can help reduce swelling and soreness around the joint. In some cases, a cortisone injection is used to calm inflammation quickly. While the evidence does not specify exact durations for these treatments, many patients find relief while the medication works. If you are a competitive athlete, your surgeon will weigh the risks carefully, as surgery is often not recommended for professional tennis players.
Surgery is usually considered only if these conservative measures fail to control your symptoms. The goal of the operation is to remove the unstable bone fragment or fix it in place to stop the painful motion. This decision is made together with your surgeon after reviewing your specific case and imaging results.
When to see someone
See your GP if you have persistent shoulder pain that does not improve with rest. Ask for a specialist review if you notice weakness, instability, or your shoulder locks or gives way. Symptoms that interfere with sleep or work also require attention. Seek help if you experience a sudden worsening of pain. This condition is linked to rotator cuff injuries, which may cause impingement from abnormal motion. While rare, the joint can be injured after trauma. If you are a professional tennis player, surgical treatment is usually not indicated, but a specialist can confirm the diagnosis through examination and imaging.
