Walch B0 glenoid: pre-osteoarthritic posterior subluxation of the humeral head.

The management of primary osteoarthritis of the shoulder has been well investigated. However, the etiology and management of posterior humeral head subluxation in the context of primary glenohumeral osteoarthritis remain controversial. The finding of static posterior subluxation of the humeral head before the development of posterior bone erosion of the glenoid in young men with radiographic findings of primary osteoarthritis has been described as arthrogenic posterior subluxation of the humeral head. It demonstrates the earliest form of the osteoarthritic evolution, and an excessive glenoid retroversion is the only probable cause of this static subluxation, although this is controversial. The clinical relevance of these findings is important in allowing the identification of patients at risk for development of glenohumeral osteoarthritis and in developing an early treatment for the subluxation to try to alter the natural course of this disease. The aim of our summary paper was to review the current literature on this matter in an attempt to better understand the pathophysiologic mechanism of this condition, which we named pre-osteoarthritic posterior subluxation of the humeral head, or Walch B-zero (B0) glenoid. It appears that Walch B0 glenoid is a pathologic condition (initially dynamic, eventually evolving into a static condition) that may lead to posterior erosion of the glenoid, taking place once there is asymmetric increased posterior glenohumeral contact forces and possibly associated with increased glenoid retroversion.