Bony Defects: Glenoid and Humeral Side—On-Track/Off-Track Concept

Abstract

Bone loss is one of the most relevant factors affecting shoulder stability. Effective assessment of the bone loss pattern might be the key to understand the behavior of a large number of shoulder instabilities, to plan the most effective treatment, and to establish the prognosis. Coexisting lesions on the glenoid side and the humeral head side interacting together are a highly relevant bone loss pattern affecting shoulder biomechanics. These are named “bipolar lesions.” Great effort was made to develop a method to quantify the negative influence of this relationship and to define a data-related therapeutic pathway, thus the “on-/off-track method” was refined. At 5 years from its publication, the advantages and limitations of this method are better defined.