This is a useful tool to help assist the decision-making and consent process for anterior shoulder instability and dislocations. It is based on the research work done in the University of Pittsburgh and a current (2025) summation of the evidence-based known risk factors for anterior shoulder instability.

Please note that the study is not perfect and may not specifically apply to an individual patient, but is (in my opinion) the best tool we have at the moment to assist the decision-making process in these specific patient groups.

Full details in the Original Article on Sciencedirect

Shaquille Charles, Stephen Marcaccio, Ryan T. Lin, Stephanie Boden, Ehab M. Nazzal, Jonathan D. Hughes, Adam Popchak, Bryson P. Lesniak, Albert Lin,The Pittsburgh Instability Tool Score Predicts Outcomes After Arthroscopic Anterior Shoulder Stabilization in Patients With Subcritical Bone Loss, Arthroscopy: The Journal of Arthroscopic & Related Surgery, 2025,

Step 1: Calculate the DTD (Distance-to-Dislocation) using the Hill-Sachs Index (HSI) & Glenoid Track (GT)
 

• HSI = Interval width between the medial edge of the Hill-Sachs lesion to the cuff insertion on the Axial sequence.
• D = Diameter of a circle based on the posterior glenoid on the best Sagittal sequence showing the glenoid surface.
• d = width of glenoid bone loss
  • GT = (0.83*D)-d

Step 2: Calculate the Pittsburgh Instability Score.