Subacromial shoulder impingement is probably the most common source of shoulder pain after the age of 40. It is related to the aging of rotator cuff tendons. This syndrome corresponds to the first stage of rotator cuff wear.
Anatomy and physiology
The rotator cuff of the shoulder is made up of 5 muscles and corresponding tendons that envelop the humeral head around the joint. These muscles help produce the strength that allow the elevation of the upper limb, internal rotation as well as external rotation. Tendons are the end of musles and attach to bones.
With age, the supraspinatus tendon, which is most often affected, loses its elastic qualities, thickens, and rubs with the acromion (acromion: part of the scapula located above the tendon). This repeated rubbing contributes to the formation of a bony spur located under the acromion. In return, this bony spur wears the superficial part of the underlying tendon, and causes pain.
Symptoms
Anterior impingement syndrom of the shoulder is most often spontaneous, occurs without effort, or notion of trauma. Pain is progressively worsening over time. At first, pain is often linked to movement, such as putting on or taking off clothing. Then, night pain comes, and often wakes the patient up in the middle of the night. Strength is most often preserved outside of acute painful episodes.
Diagnosis and Imaging
The age of the patient (after 40), the nature of the symptoms, and the accurate clinical examination carried out by the specialist contributes to the diagnosis of subacromial impingement.
The examination manoeuvres consist of highlighting the pain caused by the friction between the supraspinatus tendon and the bony spur underneath the acromion. Most of the time, mobility and strength are preserved.
Simple X-rays do not show tendons but sometimes only the bony spur located underneath the acromion.
The ultrasound scan performed by a trained practitioner sometimes highlights impingement, which is characterized by friction between the supraspinatus tendon and the acromion. The rotator cuff tendons, in this case, do not show signs of complete rupture.
The MRI scan confirms the presence of the acromial spur, and also allows consultants to assess the condition of the tendons (thinned or partially ruptured) as well as the condition of the corresponding muscle.
Finally, a test injection is mandatory to confirm the diagnosis of subacromial impingement . This test also allows to predict the success of a future procedure.
Treatment
Initially, you can start a functional treatment, based on anti-inflammatories and physiotherapy. A so-called guided injection performed by a radiologist under ultrasound control will be systematically offered in order to inject the product (corticosteroid) in the right place.
In case physio treatment fails, or steroid injection brings a very temporary pain relief, an arthroscopic procedure called decompression maybe offered.
This operation is performed through key holes, (2 or 3)under general anaesthetic.
The aim of this procedure is to remove the bony spur located under the acromion, and to allow more space between the bone and the tendon, to avoid impingement.
This procedure lasts 15 minutes and should be performed very acurately by a specialized surgeon.
Post-operative and rehabilitation
This operation is performed on a day case surgery. After decompression, the arm is free and needs immediate gentle physio to recover motion gently pain free.
Sport activity will be resumed when the pain has completely disappeared. Involvement of both shoulders is very common, but is often delayed in time, with the first side affected often being the dominant side.
The pain, which motivated the operation, disappears very gradually over a period of 4 to 6 months.
Rehabilitation begins in the pool (Hydrotherapy) but also alone in passive training as indicated below. Indeed, the first step in rehabilitation is to recover one's mobility
As soon as the pain subsides and the mobility of the shoulder recovers, it is then time to strengthen the muscles.
Complications
While most often the consequences of these operations are simple, it is nevertheless necessary to insist on the progressive nature of pain relief.
Post-operative stiffness or temporary frozen shoulder is possible, requiring injection and hydrotherapy.
Infection is an exceptional complication under arthroscopy.
Summary
Subacromial impingement is the most common cause of shoulder pain after the age of 40. It is related to the beginning of wear and tear of the rotator cuff tendons. If it causes significant discomfort or pain it is accessible to endoscopic treatment.
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