Acromial and scapular spine fractures after reverse total shoulder arthroplasty

Acromial and scapular spine fractures after reverse total shoulder arthroplasty (RTSA) can occur intraoperatively or postoperatively with post-operative stress fractures the most common.

Epidemiology

Acromial and scapular spine fractures complicate ~7.5% (range 3.1-11.2%) of RTSAs ^1,2.

Pathology

• intraoperative fracture: rare and can be treated depending on the location and displacement of the fracture, as well as the stability of the implant, conservatively or with open reduction-internal fixation (ORIF) ¹

• post-operative fracture

  • most commonly occur between 3 and 12 months (range 1-94 months) after RTSA ¹

  • acromial or scapular spine stress fractures are more common the post-trauma fractures ²

    • the mechanism of fracture in a fall or an event requiring to reach out and grab something to prevent a fall may be from rapid deltoid contraction ¹

  • atraumatic glenoid neck periprosthetic fractures ⁵

    • can occur with or without glenoid loosening

    • mechanism thought to be related to deltoid over tensioning, low bone mineral density, and/or screw position

Several factors may also increase the risk of acromial fractures after RTSA:

• the superior screw of the glenoid baseplate is too long or exiting at the scapular spine base may cause increased stress in the scapular spine with fracture ¹

• distalisation and medialisation of the center of rotation causes excessive tension on the deltoid with increased stress on the acromion and scapular spine ¹

• low bone mineral density ³

Classification

Three types of acromial fracture are defined by Levy et al. ¹

• type I: small fractures of the anterior acromion

• type II: fractures through the anterior acromion just posterior to the acromioclavicular joint

• type III: fractures of the posterior acromion or scapular spine

Radiographic features

Plain radiograph

X-ray is the first-line imaging choice but only has a sensitivity of ~80% ¹.

CT

In patients with a high clinical suspicion for scapular fractures, CT is the imaging modality that best identifies fractures not apparent on plain radiographs ^1,3.

Nuclear medicine

SPECT-CT can be used for a diagnosis of the stress reaction or non-displaced fracture in the symptomatic patient.

Treatment and prognosis

• conservative management for acute non-displaced fractures of the scapula with nonunion rates as high as 50-75% ¹

• operative management for painful nonunion or displaced fractures with surgical fixation with dual orthogonal plating if possible ¹

See also

• reverse total shoulder arthroplasty

• open reduction-internal fixation (ORIF)