Radiologic features of idiopathic pre-osteoarthritic posterior subluxation of the humeral head

Pre-osteoarthritic posterior subluxation of the humeral head (PPSHH), also referred to as a Walch B0 glenoid, is characterized by pathologic posterior subluxation of the humeral head without degenerative bony changes on plain radiographs. The purpose of this study was to describe the imaging findings of PPSHH and to assess the relationship between glenoid retroversion and HH subluxation.

This was a retrospective case series of patients with symptomatic PPSHH. Retroversion was measured on magnetic resonance imaging based on both Friedman's line and the scapular axis line. HH subluxation was measured based on the glenohumeral index (GHI) and the scapulohumeral index (SHI). The relationship between retroversion and HH subluxation was evaluated. The difference in glenoid cartilage thickness between the anterior and posterior aspects of the glenoid was compared.

Eight patients were included (mean age, 34.0±4.7 years). Mean retroversion was 17.2°±5.8° based on Friedman's line and 14.0°±5.6° based on scapular axis line. Mean HH subluxation was 63.7%±6.2% based on GHI and 77.5%±9.9% based on SHI. Cartilage thickness was less in the posterior glenoid compared to anterior glenoid, and all patients had selective chondral wear on the posterior glenoid with a posterior labral tear. There was a direct relationship between the degree of glenoid retroversion and HH subluxation.

PPSHH is characterized by posterior glenoid chondral thinning and posterior labral tears in the setting of HH subluxation without erosive osseous changes. This pathology can present with varying degrees of retroversion and HH subluxation, and increasing retroversion is associated with more severe subluxation. Level of evidence: IV.