The acromion is the bony roof at the top of the shoulder blade, over the top of the shoulder joint. It normally forms from several separate pieces of bone that fuse together during adolescence. In an os acromiale one of those pieces has not fused, and the separated fragment remains joined to the rest of the acromion by cartilage rather than by solid bone.
An os acromiale is usually harmless and is often found incidentally. Most are managed without surgery, with physiotherapy. In some people, however, the unfused fragment moves and becomes painful, contributing to impingement and affecting the rotator cuff and the surrounding tendons. Surgery is considered when that is the case and non-surgical treatment has not helped.
The procedure
There are two surgical options. The separated fragment can be fixed to the rest of the acromion with screws or anchors so that the two parts unite, or the fragment can be excised, meaning it is removed altogether. Which option is appropriate depends on the type of os acromiale (meso, meta or pre, describing where along the acromion the separation lies) and on any other shoulder conditions that are present and may need treating at the same time.
The operation is usually carried out arthroscopically, through keyhole incisions, although it can be done open. About two hours of operating theatre time is typically booked.
Risks and complications
All surgery carries risk. The risks that are relevant to you are discussed with you in consultation before any decision about surgery is made.
General surgical risks
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Bruising and haematoma. The amount of bruising varies from patient to patient and usually settles quickly. A haematoma, which is a collection of blood under the wound, occasionally needs to be drained in theatre.
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Infection. Infection is uncommon but possible, and is usually treated with antibiotics.
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Deep vein thrombosis (DVT) and pulmonary embolism (PE). Blood clots can form in the veins of the leg and can travel to the lungs. These are serious conditions if they go untreated, but the risk of lasting harm is significantly reduced when they are recognised and treated promptly.
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Anaesthetic risks. These are discussed with your anaesthetist before surgery. In Australia the risk of death from a general anaesthetic is around 1 in 100,000.
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Wound problems. Superficial wound problems can occur, and most need a small intervention.
Risks specific to this procedure
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Deltoid weakness. The deltoid muscle attaches to the acromion, so weakness can follow surgery here. This is particularly relevant where the unfused fragment is excised rather than fixed.
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Persistent pain or discomfort. Pain may continue after surgery.
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Hardware problems. Where screws or anchors are used to fix the fragment, the hardware can cause problems and may need to be addressed with further surgery.
Before surgery
There are a number of things to work through while you are waiting for your surgery date. You will be given detailed written instructions covering all of this.
- Confirm with your health fund that the hospital fee is covered.
- Confirm your anaesthetist’s fees.
- Register your details with the hospital.
- Read, complete and return your paperwork to the rooms.
- Plan your transport to and from hospital. You cannot drive yourself home.
- Attend any pre-operative physiotherapy that has been recommended.
- Complete any pre-operative pathology, such as blood tests, if it has been requested.
- Wash the shoulder with benzoyl peroxide 5% wash, twice daily for two days, and then once more on the morning of surgery, five applications in total. This reduces the risk of infection with Cutibacterium acnes, a bacterium that lives in the skin.
- Pack your hospital bag: your regular medications in their original packaging, a loose button-up shirt, nightwear and toiletries. Bring your CPAP machine if you have sleep apnoea.
- If you take blood thinners, phone the rooms to confirm when to stop them.
- If you take tablets for diabetes, phone your anaesthetist to confirm whether to stop them.
- Confirm your admission details with the rooms one to two business days before surgery.
The day of surgery
- Your admission details are confirmed one to two business days beforehand. Make a note of your admission time, which may be as early as 6am, and the time from which you must fast.
- If you do not live in Brisbane, staying in the city the night before is usually recommended.
- After the admissions process you wait in the surgical waiting area. Your anaesthetist will see you for a brief consultation before you go through to theatre.
- Dr Cutbush will greet you in the anaesthetic bay and mark the operation site. You are then given the general anaesthetic.
- The usual stay is one night. Discharge is generally around 10am, after Dr Cutbush has reviewed you.
- You will be given a folder containing your post-operative pack: a letter describing what was found and what was done, together with your rehabilitation and aftercare information.
- Arrange for someone to take you home.
Recovery and healing
The shoulder is immobilised in a sling, worn full time for six weeks. Only gentle, limited movements are permitted during this period, enough to limit stiffness and to help reduce swelling and pain, but not enough to disturb the surgery. Time off work is required.
Once the sling is no longer needed, physiotherapy begins in earnest. Full recovery usually takes between six and twelve months.
Rehabilitation
Rehabilitation after os acromiale surgery focuses on reducing pain and inflammation and then restoring range of motion.
Day one
The hospital physiotherapist will fit your sling and show you how to manage eating, showering and dressing while wearing it.
The goals on day one are to manage pain and inflammation and to minimise stiffness in the glenohumeral joint while protecting the surgery. Early passive range is limited to less than 90 degrees of elevation and 45 degrees of external rotation.
Precautions: no load through the arm, no active elevation, no weight bearing, and no pushing or pulling.
Day one exercises
- Gentle active neck movements.
- Active movements of the elbow, wrist and hand.
- Gentle scapular neutral exercises and postural advice, without large scapular rolls.
- Passive pendulum exercises below 90 degrees.
- Active or passive external rotation from neutral to 30 to 45 degrees.
Pain management: positioning, a correctly fitted sling, and cryotherapy for 20 minutes every two to three hours for the first three days. After that, heat may be more helpful.
Follow-up
See a local physiotherapist in week one to two. Your exercises should not change from the day one programme unless Dr Cutbush advises otherwise.
Results after surgery
Most people who have surgery for a painful os acromiale experience improvement in pain, function, range of motion and strength. Both fixation and excision can achieve this, and individual factors affect the outcome. Where the fragment is excised, deltoid function may be affected. Where the fragment is fixed, a small proportion of patients need revision surgery, usually because the fragment has not united. Individual results vary.
Next steps
This page is general information about a surgical procedure and is not a recommendation that you have it. Whether surgery is appropriate for you can only be determined after assessment. All surgery carries risk; the risks relevant to you are discussed in consultation before any decision is made.
