Monday, June 13, 2016

Reverse total shoulder and heterotopic bone at the inferior glenoid

Heterotopic ossification of the long head of the triceps after reverse total shoulder arthroplasty.

These authors reviewed 164 patients having a reverse shoulder arthroplasty performed between 2008 and 2012. They found heterotopic ossification (HO) inferior to the glenoid in 61.6%. In 23.2% of the cases there was contact between the HO and the humerus, 3.0% appeared ankylosed.  14.6% of the cases had scapular notching.

Male and female HO rates were 74.0% and 56.1%, respectively (P = .0304). Patients with HO had less forward elevation (121°) than those without HO (133°, P = .0087).

Comment: The rate of HO in this series is somewhat higher than we might expect. The underlying cause for this increased rate of HO in reverse shoulder arthroplasty is not clear. It is possible that the surgical technique used included release of the soft tissues from the inferior glenoid with resultant stimulation of new bone formation. Erosion of the lateral glenoid neck by the humeral prosthesis ("scapular notching") with the Grammont-style implant may release bits of bone into the area that contribute to heterotopic bone formation.

The x-rays shown below demonstrate the variety of patterns of heterotopic bone formation after reverse total shoulder arthroplasty.

We suggest that the risk of HO may be reduced through the use of a more laterally offset glenosphere that avoids contact between the humeral component and the lateral scapula, by avoiding irritating the bone at the lateral scapula when performing soft tissue releases around the glenoid, and by thorough irrigation to remove any bone fragments that may have resulted from preparation for the implants.