Risk factors for acromial and scapular spine fractures - are we any smarter about preventing these complications?

Acromial and scapular spine fractures are major complications of reverse total shoulder arthroplasty with a substantial negative impact on the clinical outcome of the procedure. The management of these fractures is challenging with high rates of malunion and nonunion, decreased function, and complications (see Acromial and scapular spine fractures after reverse total shoulder arthroplasty)

Surgeons and patients are concerned about reducing the incidence of these fractures through the identification of modifiable risk fractures.

The 57 authors of Risk Factors of Acromial and Scapular Spine Stress Fractures Differ by Indication: A Study by the ASES Complications of Reverse Shoulder Arthroplasty Multicenter Research Group point out that both patient and surgical (implant and technique) characteristics affect the risk of fracture of the acromion and scapular spine.

Their study included 4764 patients with preoperative diagnoses of arthritis (GHOA),  cuff tear arthropathy (CTA), or massive cuff tear (MCT) with the minimum follow-up of 3 months (range: 3-84). The incidence of cumulative stress fracture was 4.1%. The incidence of stress fracture in the GHOA cohort was 2.1% compared to 5.2% in the CTA/MCT cohort. Presence of inflammatory arthritis and osteoporosis were associated with an increased risk of these fractures. Most of the fractures were atraumatic. 

Comment: Because of its short minimum followup after reverse total shoulder surgery (3 months) this study may underestimate the rate of these fractures. The publication Incidence, radiographic predictors, and clinicaloutcome of acromial stress reaction and acromial fractures in reverse total shoulder arthroplasty found that acromial and scapular spine fractures are detected at a mean of 16 ±
24 months after RSA.

The authors of Risk Factors of Acromial and Scapular Spine Stress Fractures Differ by Indication: A Study by the ASES Complications of Reverse Shoulder Arthroplasty Multicenter Research  Group concluded that "Patients with CTA/MCT and postoperative stress fracture are more likely to be female, have osteoporosis, and have a diagnosis of inflammatory arthritis, while patients with GHOA are at risk of stress fracture with a diagnosis of inflammatory arthritis alone." However, the diagnosis is not a modifiable risk factor; neither is age, sex, preoperative pathoanatomy, or the degree of osteoporosis. 

Modifiable risk factors may include surgical technique, implant characteristics, component position and postoperative activity. This study did not investigate the relationship of these modifiable characteristics to the rate of acromial / scapular spine fracture after reverse total shoulder.

Hopefully analysis of these modifiable risk factors is forthcoming from the ASES Complications of Research Shoulder Arthroplasty Multicenter Research Group.

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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 ream and run procedure (see this link).
The total shoulder arthroplasty (see 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).