Etymology: AS, tyrnan + ME, bocle, small shield; ONorse, kasta
an orthopedic device used to encase and immobilize the entire trunk, one upper arm to the elbow, and the opposite upper leg to the knee. It is constructed of plaster of paris or fiberglass and incorporates hinges as part of its design in the treatment of scoliosis. The hinges are placed at the level of the apex of the curvature. It is used for preoperative and postoperative positioning, although less frequently than the Risser cast. An adaptation of the turnbuckle cast is used occasionally as a hyperextension cast for the treatment of kyphosis or kyphoscoliosis. Compare Risser cast.