Sulu's leg protected with a splint.
A splint was an ancient medical concept that uses two flat pieces of wood, or plastic, wrapped with a bandage to keep a broken bone immobile. According to Doctor Katherine Pulaski, it is a time-honored way of practicing medicine "with your head, your heart and your hands." (TNG: "Contagion")
The crew fashioned a splint to hold the bone while they carried the miniaturized Hikaru Sulu to Sickbay after fell from his controls and broke his leg. (TAS: "The Terratin Incident")
By the 23rd and 24th century the favored form of technology used to repair broken bones became the bone-knitting laser, or knitter. (TAS: "The Terratin Incident"; TNG: "Contagion")