There are many internal causes of gross mechanical shoulder instability.
One in particular is due to an excessive loss of bone stock from the glenoid or shoulder socket. This is called a bony Bankhart lesion and is often referred to as an “engaging lesion”.
This type of shoulder instability will not be adequately treated by simply reconstructing the capsulolabral and ligamentous shoulder structures (via a Bankart repair). A bony reconstruction procedure needs to take place to replace the area of bone loss.
One such procedure is called a Laterjet procedure.
Some biomechanics studies suggest that containment of the humeral head is reduced when an anteroinferior glenoid defect is present and therefore the shoulder is significantly less resistant to forces that may cause dislocation.
It is generally accepted that an inferior glenoid bone loss of 20-30% is sufficient enough to adversely affect recurrence rates following a Bankart repair and require a bone grafting procedure like the Laterjet to restore osseous and overall shoulder stability.
The Laterjet procedure involve a transfer of the coracoid process to the area of glenoid bone loss. The major advantages of the Laterjet procedure are the extension of the “glenoid concavity” and the creation of a muscle-tendon “sling effect” by way of the transferred conjoined tendon.
The widely accepted method for assessing the size of the bone defect is via computed tomography (CT scan).
Below is a post surgical scan depicting the transferred coracoid process.