Monday, July 1, 2013

Pattern of erosion in type B glenoids - is there such thing as a B1?

Three-dimensional computed tomography scan evaluation of the pattern of erosion in type B glenoids

The humeral head is often posterior displaced and the posterior glenoid is often eroded in glenohumeral osteoarthritis and in capsulorrhaphy arthropathy. Posterior head displacement without glenoid erosion is referred to as a Walch B1 type and posterior head displacement with posterior glenoid erosion is refferred to as a Walch B2 type glenoid, although intermediate forms are common.

The authors performed 3D reconstruction of 24 type B1 glenoids and 48 type B2 glenoids. Posterior erosion averaged 4.2 mm (range 1.7 to 9.6 mm).  The erosion was typically in the posteroinferior direction (119°; SD, 26.8).

While the authors stated that 3-D scans are necessary to evaluate the glenoid, we have found that a standardized axillary view provides the information necessary for surgical reconstruction. However, this article is important in that it demonstrates that all type B glenoids (i.e. those with posterior displacement of the humeral head)  have at least some degree of posterior erosion. Thus, all type B glenoids may be type B2s with a degree of biconcavity.

Posterior inferior glenoid erosion is important because it favors posterior instability of the elevated arm.

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