Persistent shoulder pain with overhead movement, particularly when imaging reports an unusual finding at the tip of the shoulder blade, may be related to os acromiale. This developmental variant, in which part of the acromion fails to fuse during adolescence, is present in approximately 8 percent of the population but only causes symptoms in a proportion of those affected. When it does become symptomatic, it can mimic or directly contribute to rotator cuff impingement and tears.
Dr. Kushalappa Subbiah provides specialist assessment and management of symptomatic os acromiale in Bangalore, including arthroscopic decompression and open fixation for patients whose symptoms do not resolve with conservative treatment.
What is Os Acromiale?
The acromion is the bony process that projects from the shoulder blade over the top of the shoulder joint, forming the roof of the subacromial space through which the rotator cuff tendons pass. During normal development, the acromion forms from multiple ossification centres that typically fuse together between the ages of 15 and 25. In some individuals, one or more of these growth centres fail to fuse, leaving a separate unfused bony fragment connected to the rest of the acromion by fibrocartilaginous tissue. This unfused segment is called an os acromiale.
The os acromiale is most commonly found at the junction of the anterior and middle thirds of the acromion, a site called the meso-acromion. While many people with an os acromiale never develop symptoms, the mobile unfused segment can move abnormally with shoulder activity, causing repetitive trauma to the overlying deltoid attachment and the underlying rotator cuff, leading to impingement pain and, in some cases, contributing to rotator cuff tears.
Types of Os Acromiale
Causes
Os acromiale is a developmental condition rather than a fracture. The ossification centres that form the acromion during adolescence normally fuse between the ages of 15 and 25. In some individuals, likely due to a combination of genetic factors and repetitive overhead loading during the years when fusion is occurring, one or more centres fail to fuse. Repetitive overhead activity during adolescence, including competitive swimming, cricket, and throwing sports, may contribute to non-fusion. A family history of os acromiale has been reported, suggesting a genetic predisposition.
- Shoulder pain at the outer edge of the acromion, worsening with overhead movement, reaching across the body, or sustained overhead activity
- Symptoms of subacromial impingement: a painful arc of movement between 60 and 120 degrees of arm elevation
- Rotator cuff weakness and pain with resisted shoulder movements if the os acromiale has contributed to a cuff tear
- In some patients, tenderness directly over the unfused junction when the shoulder tip is palpated
- Symptoms that have often been present for years, sometimes attributed to other shoulder problems before the os acromiale is identified on imaging
Diagnosis
Os acromiale is frequently identified on shoulder X-rays, though an axillary view or a specific outlet view is often needed to clearly demonstrate the unfused segment. CT scan provides excellent bony detail of the fragment size, position, and the nature of the fibrocartilaginous junction. MRI is used to assess for rotator cuff tears, subacromial bursitis, and oedema at the junction of the os acromiale, which helps determine whether the fragment is biologically active and likely to be symptomatic. An injection of local anaesthetic into the junction can confirm whether the os acromiale is the source of pain before proceeding to surgery.
Treatment
Non-Surgical Management
Many patients with an incidentally identified os acromiale do not require any treatment. When symptoms are present, the initial approach involves physiotherapy to optimise rotator cuff and periscapular strength, anti-inflammatory medications, and corticosteroid injection into the subacromial space or the os acromiale junction. A significant proportion of patients achieve adequate symptom control with these measures.
Arthroscopic Subacromial Decompression
For patients with subacromial impingement symptoms attributable to the os acromiale, arthroscopic subacromial decompression can relieve symptoms by smoothing the undersurface of the acromion and removing inflamed bursal tissue, without addressing the os acromiale directly. This approach is suitable when the fragment is small and stable.
Open Fixation of Os Acromiale
For patients with a large, mobile, or persistently symptomatic os acromiale, particularly when associated with rotator cuff tears, Dr. Kushalappa performs open internal fixation of the unfused segment. The fibrocartilaginous junction is prepared and the bony surfaces are freshened. The os acromiale is fixed to the rest of the acromion using compression screws and, in some cases, bone graft from the local area. This achieves bony union of the fragment, eliminating the abnormal mobility that drives symptoms. Recovery involves a sling for 4 to 6 weeks, with gradual physiotherapy progression and return to full activity at 4 to 6 months.
Why Choose Dr. Kushalappa Subbiah in Bangalore?
Dr. Kushalappa Subbiah completed a Fellowship in Shoulder Surgery at the Sydney Shoulder Research Institute, where he trained in advanced arthroscopic shoulder procedures including labral repair and reconstruction. He holds the International Olympic Committee (IOC) Diploma in Sports Medicine, and has direct clinical experience managing shoulder injuries in Indian athletes across cricket, swimming, tennis, and contact sports. He is appointed as a Consultant Shoulder Surgeon at NH Hospital, Bangalore.