By Joseph P. Iannotti, MD, PhD and Eric Ricchetti, MD
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The Walch classification is the most frequently utilized method for defining glenohumeral pathology in osteoarthritis. Orthopaedic surgeons have used it to make recommendations for surgical interventions and joint replacements since its creation nearly a decade ago. However, many studies have demonstrated Walch’s lower inter-rater reliability in classifying pathology, which leaves room for error in performing and interpreting clinical studies. The Walch classification’s inability to reproduce common patterns of pathology becomes even more apparent when treating patients with more severe glenoid pathology.
B and C glenoid misclassification
We hypothesized that the problem is not with the overall classification method, but with its existing definitions. Specifically, some patterns of glenoid bone loss and humeral head alignment do not fit within existing Walch definitions. These pathologies have distinguishable patterns of bone erosion and alignment that require different treatment and produce unique clinical outcomes.
This need for a more reproducible classification is especially important for patients with B and C glenoid types. Additionally, an enhanced classification system is crucial for consistent clinical outcomes research involving glenohumeral pathology. Define these new pathologies, and Walch becomes a more reliable classification system.
Uncovering potential subtypes
We analyzed 155 cases of nontraumatic, noninflammatory, primary glenohumeral osteoarthritis. We used a custom software to evaluate preoperative 3D computer tomography (CT) and to examine the relationship of the center of the humeral head to the center of the glenoid as well as the patterns of glenoid morphology.
We assessed premorbid glenohumeral anatomy based on previously validated methods using 3D glenoid vault and humeral sphere models, including joint line, premorbid glenoid version and humeral-glenoid alignment (HGA). We measured pathologic glenohumeral anatomy as joint line medialization, paleo glenoid length, glenoid version and HGA.
Consensus readings by two surgeons determined classifications for the cases within the existing five Walch groups. We then reclassified each patient based on the methods above.
Two new glenoid types: B3 and C2
We discovered measurable and reproducible anatomic features that differentiate new glenoid morphologic types from the existing Walch stratifications.
- B3 defining features:
- Normal premorbid version
- Acquired central and posterior bone loss usually greater than B2 glenoid
- Little or no paleo glenoid
- Highly variable translation of humeral head from centered to posterior translated
- Significantly greater medial wear than a classic B2
B3 has both central and asymmetric posterior bone loss making the joint line more medialized. Unlike B2, B3 either does not have or has an incredibly small paleo glenoid.
- C2 defining features:
- Dysplastic with high native retroversion yet acquired posterior bone loss
- Appears as biconcave glenoid with posterior translation of the humeral head
- Pathologic glenoid retroversion and premorbid glenoid vault model significantly higher than B2
C2 and B2 both have a biconcave surface with associated posterior humeral head subluxation. However, the pathologic glenoid retroversion and the premorbid glenoid vault model version are both significantly higher in C2 than B2.
The B3 and C2 patterns are distinct and may result in different clinical outcomes than their B2 or C counterparts. B3 and C2 should be included in a new or modified Walch classification with seven different glenoid subtypes. We recommend further independent use of a modified classification that adds the B3 and C2 groups to Walch. These new definitions will help determine whether these pathologies require different surgical interventions for optimal recovery.
Mean values for pathologic glenoid version, premorbid version, length of the paleo glenoid, joint line medialization, pathologic humeral-glenoid alignment (HGA), and premorbid HGA. For a given measure, p values represent significant differences in means across all the glenoid subtypes in the modified classification. Post hoc tests (with Bonferroni multiple comparison corrections) were then conducted to identify specific glenoid subtypes showing differences on pairwise comparisons.
Dr. Iannotti is Chair of the Orthopaedic and Rheumatologic Institute. Dr. Ricchetti is staff in the Department of Orthopaedic Surgery.