These 23 experienced surgeons assessed the inter and intra-observer reliability of the modified Walch classification using three-dimensional (3D) computed tomography (CT) imaging. A summary of the classification criteria used in this study is shown here:
A1 Centered humeral head, minor glenoid erosion.
A2 Centered humeral head, major central glenoid erosion defined by a line drawn
from the anterior to posterior rims of the glenoid transecting the humeral head.
B1 Posteriorly subluxated humeral head, with no or minor posterior glenoid erosion.
B2 Posteriorly subluxated humeral head, posterior glenoid erosion with biconcavity and no dysplasia.
B3 Posteriorly worn glenoid that is monoconcave with little or no biconcavity due to posterior and central glenoid erosion, without dysplasia. A threshold of > 15 degrees of retroversion has been suggested
C1 Dysplastic glenoid with high degrees of retroversion due to dysplasia rather than glenoid erosion. A threshold of at least 25° glenoid retroversion has been suggested.
C2 Dysplastic glenoid with acquired posterior glenoid erosion creating glenoid biconcavity and posterior subluxation of the humeral head.
D Glenoid anteversion or anterior humeral head subluxation.
De-identified preoperative CTs of patients with primary glenohumeral OA undergoing anatomic or reverse total shoulder arthroplasty (TSA) were included: Group 1 (96 cases involving all modified Walch classification categories evaluated and Group 2 (98 cases involving posterior glenoid deformity categories [B2, B3, C1,C2].
Inter-observer reliability showed fair to moderate agreement.
The authors concluded that cases with a spectrum of posterior glenoid bone loss and/or dysplasia can be harder to distinguish by modified Walch type due to a lack of defined thresholds.
Comment: This study points out the challenge of classifying glenoid pathoanatomy, even when experienced surgeons use CT scans and sophisticated software. As the authors point out, the problem is at least in part due to the issue of creating "thresholds" for variables that are continuous, such as the degree erosion (which can range from none to a lot) and the degree of version (which can range from ante version to retroversion). Note that
A1 is differentiated from A2 by the degree of glenoid erosion
B1 is differentiated from B2 by the degree of glenoid erosion
A2 is differentiated from B3 by the degree of version
A1 and A2 are differentiated from D by the degree of version
Examples of the different types of glenoid pathoanatomy are shown below.
In some respects it may be more useful and more consistent among observers if arthritic glenohumeral pathoanatomy is characterized in terms of simple measurements, including the quantitative measurement of the degrees of retroversion
These are measurements critical to the understanding of the pathoanatomy and to planning the shoulder arthroplasty.
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