Posterior shoulder instability (ICL 15)

Posterior shoulder instability is much less common, more difficult to diagnose, and even more challenging to manage compared to anterior instability. Moreover, true posterior and multidirectional instability can be easily overlooked because the presentation can be confusing and oftentimes they are overlapping entities. A detailed clinical examination and careful imaging evaluation are paramount for the correct diagnosis and indication to treatment. The primary goal of treatment other than pain control and restoration of function is to avoid recurrence of instability and to reduce the risk for posttraumatic osteoarthritis. Nonsurgical treatment is successful in most cases; however, surgical intervention is indicated if conservative treatment fails. For successful surgical treatment, a thorough definition of the instability pattern and a correct evaluation of all soft tissue and bony problems that contribute to instability must be performed. Differently from bony anterior instability, in presence of bone defects, the critical amount of posterior glenoid bone loss has not been defined yet. Moreover, posterior glenoid reconstructive options are limited compared to those available for anterior glenoid bone deficiency. The following chapter will provide an overview on epidemiology, pathomechanics, clinical presentation, imaging findings, and treatment options in posterior shoulder instability.