Thomas’ splint [Hugh O. Thomas, English surgeon, 1834–1891] , 1. a rigid splint constructed of steel bars that are curved to fit the involved limb and are held in place by a cast or a rigid bandage. It is used in the treatment of chronic joint diseases. 2. a rigid metal splint that extends from a ring at the hip to beyond the foot. It is used to treat a fractured leg and, in conjunction with various traction and suspension devices, to immobilize and position a fractured femur in a preoperative or postoperative patient. Also called Thomas’ knee splint, Thomas’ ring splint.