Acromial and spine fractures after reverse total shoulder

There has been substantial interest in the prevention, diagnosis and treatment of acromial and spine fractures after reverse total shoulder arthroplasty. 

Here's a case: a middle aged man had a reverse total shoulder after multiple failed cuff repairs of the left shoulder. At the six week checkup, all was well clinically and radiographically.

He started gentle assisted flexion exercises. Two days after the office visit while reaching up he had sudden pain in the shoulder and heard a 'crack'. He returned to the office at which time tenderness was noted at the posterior acromion. The AP view was not remarkable.

However, the axillary view showed a non-displaced crack in the acromion.

This case reveals the potential of fracture of an acromion that is not used to being loaded.

Here's another case:
An 85 year old lady presented with severe cuff tear arthropathy as shown below.

She had a reverse total shoulder in early 2012. Two years after surgery she had excellent comfort and function. Here x-rays at that point are shown below.

Three and a half years after her procedure she developed the atraumatic onset of posterior shoulder pain. Her axillary x-ray shows a fatigue fracture of the scapular spine (to the left of the red line).

We anticipate that these will heal with non operative management.

Here are a couple of recent relevant articles.

Patient risk factors for acromial stress fractures after reverse shoulder arthroplasty: a multicenter study

These authors investigated the incidence of acromial stress fractures (ASFs) after reverse total shoulder and and sought to identify preoperative patient characteristics associated with their occurrence.

They identified 1479 patients undergoing either primary or revision RTSA between 2013 and 2018 with minimum 3-month follow-up. ASFs were defined as radiographic evidence of an acromial or scapular spine fracture with clinical symptoms (eg, tenderness over the acromion or scapular spine). 

Overall, 54 (3.7%) patients were diagnosed with an ASF after RTSA. Patient-related factors independently associated with the development of an ASF included female sex, rheumatoid arthritis, osteoporosis, a diagnosis of degenerative joint disease with rotator cuff tear, and fracture malunion/nonunion (OR, 5.21; 95% CI, 1.20-22.76; P < .05).

Comment: This is an interesting study, although the followup time is short. Many acromial fractures occur more than 3 months after surgery (see this link).

The article below dives a bit deeper into the local changes in scapular bone density associated with age and sex.

Changes in Scapular Bone Density Vary by Region and are Associated with Age and Sex

They studied 97 three-dimensional models of the scapula that were segmented from routine clinical computed tomography (CT) scans, and obtained detailed calibrated bone density measurements for each bone model. The effects of age and sex on cortical and trabecular bone density were assessed for the entire scapula.

They found that cortical bone loss averaged to 1.0 mg/cc and 0.3 mg/cc per year. 

Trabecular bone loss was 1.6 mg/cc and 1.2 mg/cc for female and males respectively. 

Areas that were significantly affected by age included the acromion, the scapular spine, the base of the coracoid, the inferior glenoid neck as well as the glenoid vault. 

Areas that were significantly affected by sex were the scapular spine and body.

Comment: These findings are consistent with the risk factors for acromial and scapular spine fractures after reverse total shoulder.

Here are some other links relating to acromial and scapular spine fractures after reverse total shoulder: link 1, link 2, link 3, link 4, and link 5.

 How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link).

How to x-ray the shoulder (see this link).

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

The smooth and move procedure for irreparable rotator cuff tears (see this link).

Shoulder rehabilitation exercises (see this link).