The SHEAR Deformity in OBPI
One of the most important consequences of OBPI is the internal rotation posture that is seen in many if not most of these children. It appears to be a continuation of the “waiter’s tip” posture seen at birth. The direct cause of the waiter's tip is weakness in the abductors and external rotator muscles of the shoulder. The first secondary effects are contractures that form in the gravity-enhanced muscles of the chest and back. This leads to weakness in abduction of the shoulder and is treated with the Mod Quad sequence of surgical procedures.
The Mod Quad has had a long record of success in improving abduction significantly. One residual problem has always been the ongoing internal rotation posture and winging of the scapula. Recent advances in 3D CT scan technology have allowed visualization of the bony deformity and then allowed design of a surgical procedure to improve the problem.
The bony changes are collectively known as a SHEAR deformity (Scapular Hypoplasia, Elevation and Rotation). There are 5 grades (0 through 4) and the Triangle Tilt surgery normalizes the relationships of the bones to allow better arm and hand positioning, movement, and growth.