Acromial fractures after reverse total shoulder arthroplasty

Classification of postoperative acromial fractures following reverse shoulder arthroplasty.

Acromial / scapular spine fractures are noted in approximately 5% of patients having reverse total shoulders. These authors investigated 18 patients having pain along the acromion or scapular spine after a reverse total shoulder.

Pausing there for a moment, this scenario strongly suggests a fatigue fracture of the acromion/scapular spine no matter what the imaging findings might be (compare to a runner who after increasing the workouts develops pain and transverse tenderness across the mid/distal tibia). 

Anyway, the authors set out to investigate the ability of observers to detect these fractures on radiographs and to  establish fracture union (again, isn't resolution of the pain a pretty good way to track progress to union?).

In this series, if radiographic findings were negative, computed tomography (CT) scans were performed. Sixteen of the 18 had radiographic confirmation of fracture.  The authors tried to classify the fractures on the basis of the imaging studies (again, wouldn't clinical exam localize the fracture in relation to the anatomy of the acromion and scapular spine?). 

In their classification,  type I included fractures through the mid part of the acromion, involving a portion of the anterior and middle deltoid origin; type II fractures involved at least the entire middle deltoid origin with a portion but not all of the posterior deltoid origin; type-III fractures involved the entire middle and posterior deltoid origin. Among the 16 with radiographic confirmation, there were 2 type Is, 8 type IIs, and 6 type IIIs.

The clinical outcomes were poor in 1 of 2 of the type Is, 1 of 8 of the type IIs and in both of the type IIIs.

These cases came from a series of  157 reverse shoulder arthroplasties (152 patients) performed by a single surgeon over a period of fifty-six months, from November 2006 through July 2011.  This is a rate of 10%, higher than those often reported. It would be really nice to know how the patients in this series with fractures differed from those who did not have recognized fractures with respect to factors such as age, gender, bone quality, lengthening of arm, component selection and more. From this information we might learn how to avoid these problems in the future.

Well, within 24 hours of putting up the post above, we get a call that one of our patients who had a reverse in November of 2012 and who had been doing exceptionally well, put her arm out to the side and felt a sudden soreness over the back of her shoulder blade. On exam she was able to pinpoint the tender spot - the mid scapular spine (zone II in the illustration below). Knowing the diagnosis at that point, we reviewed the plain images obtained by another provider.

The scapular spine crack can be seen between the ends of the two black lines in the image below.

We plan to reduce her arm use for 6 weeks in anticipation that this fracture will heal.

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