Combined posterior osseous Bankart lesion and posterior humeral avulsion of the glenohumeral ligaments: a case report and pathoanatomic subtyping of "floating" posterior inferior glenohumeral ligament lesions.

T he pathoanatomy of anterior shoulder dislocations has been well documented. Perthes described an anterior labral lesion as early as 1906, and Bankart wrote his classic article on recurrent anterior dislocations more than seventy years ago. Until recently, much less had been written about posterior shoulder instability; to our knowledge, the first case series was reported by Reeves in 1963. Recurrent posterior glenohumeral joint instability is far less common than anterior instability, accounting for approximately 2% to 10% of all cases of shoulder instability. Pathoanatomic findings in patients with unidirectional posterior instability include a posterior Bankart lesion, posterior humeral avulsion of the glenohumeral ligament (PHAGL), and various combinations of the two. In their article on humeral avulsion of the glenohumeral ligament (HAGL), Bui-Mansfield et al. defined the floating posterior inferior glenohumeral ligament (floating PIGHL) as a combined posterior Bankart lesion and PHAGL. Multiple cases of this lesion have been reported in the literature. To our knowledge, there has been no reported case of the specific combination of a posterior osseous Bankart lesion and a PHAGL injury. We present a case of recurrent posterior instability associated with a combined PHAGL injury and posterior osseous Bankart lesion. We also describe four pathoanatomic subtypes of floating PIGHL lesions. The patient was informed that data concerning his case would be submitted for publication, and he provided consent.