Chan Kevin, Knowles Nikolas K, Chaoui Jean, Gauci Marc-Olivier, Ferreira Louis M, Walch Gilles, Athwal George S
Roth|McFarlane Hand and Upper Limb Center, St. Joseph's Health Care, Western University, London, ON, Canada.
Telecom Bretagne, Plouzané, France.
J Shoulder Elbow Surg. 2017 May;26(5):909-914. doi: 10.1016/j.jse.2016.10.003. Epub 2017 Jan 11.
The type B3 glenoid is an addition to the Walch classification. A potential etiologic theory is that it is a progression of the B2. It is characterized by uniconcavity, absent paleoglenoid, medialization, retroversion, and subluxation. The purpose of this study was to describe the morphology of B3 glenoids.
Fifty-two patients with B3 glenoids underwent 3-dimensional analysis of computed tomography data. Glenoid measurements (retroversion, inclination, medialization) and humeral head subluxation according to the scapular and glenoid planes were determined. The measured variables were compared between male and female patients.
The mean B3 retroversion, inclination, and medialization were 24° ± 7°, 8° ± 6° superior, and 14 ± 4 mm, respectively. The mean posterior subluxation was 80% ± 8% and 54% ± 6% according to the scapular and glenoid planes, respectively. There were no differences in B3 characteristics between sexes (P > .05). A significant correlation existed between glenoid retroversion and humeral head subluxation relative to the scapular plane, with every 1° increase in retroversion translating to a 1% increase in subluxation (P < .001). In contrast, when referencing the glenoid plane, the humeral head remained concentric to the erosion.
The B3 is uniconcave and retroverted. As glenoid retroversion increases, posterior humeral head subluxation significantly increases as referenced to the scapular plane; however, when referenced to the glenoid plane, the head remains concentric to the erosion. This appearance of "concentricity" is acquired secondary to the wear pattern, creating a uniconcave glenoid. Therefore, surgeons should be aware that the visualized concentricity is a product of the erosion pattern and thus may conceal a greater amount of subluxation potential.
B3型肩胛盂是瓦尔什分类的补充类型。一种潜在的病因学理论认为它是B2型的进展。其特征为单凹面、陈旧性肩胛盂缺失、内移、后倾和半脱位。本研究的目的是描述B3型肩胛盂的形态。
对52例B3型肩胛盂患者的计算机断层扫描数据进行三维分析。确定肩胛盂测量值（后倾、倾斜度、内移）以及根据肩胛和肩胛盂平面的肱骨头半脱位情况。比较男性和女性患者的测量变量。
B3型肩胛盂的平均后倾、倾斜度和内移分别为24°±7°、上倾8°±6°和14±4mm。根据肩胛平面和肩胛盂平面，平均后方半脱位分别为80%±8%和54%±6%。两性之间的B3型特征无差异（P＞0.05）。肩胛盂后倾与相对于肩胛平面的肱骨头半脱位之间存在显著相关性，后倾每增加1°，半脱位增加1%（P＜0.001）。相比之下，以肩胛盂平面为参照时，肱骨头与侵蚀部位保持同心。
B3型肩胛盂为单凹面且后倾。随着肩胛盂后倾增加，相对于肩胛平面，肱骨头后方半脱位显著增加；然而，以肩胛盂平面为参照时，肱骨头与侵蚀部位保持同心。这种“同心”外观是磨损模式导致的继发性结果，形成了单凹面肩胛盂。因此，外科医生应意识到所观察到的同心性是侵蚀模式的产物，可能会掩盖更大的半脱位潜能。
