After the occurrence of an inability to bend the thumb, treatment should be tailored to the cause of the inability to bend the thumb. If the thumb cannot be bent due to a rupture of the thumb flexor tendon caused by a trauma to the thumb, and simple conservative treatment is ineffective, surgery to anastomose the ruptured tendon is required to restore function. If there is a fracture in the interphalangeal joint of the thumb that affects the joint surface, and the joint movement is restricted to form the thumb cannot be bent, the joint must be surgically corrected to restore the flatness of the joint surface in order to restore the movement of the joint and restore the bending of the joint and the thumb. If the thumb cannot be bent due to stenosing tenosynovitis that affects the sliding of the tendon, surgery, i.e., partial tenosynovectomy for stenosing tenosynovitis, should be performed to relieve the stenosis and obstruction of the tendon in the tendon sheath of the thumb in order to restore the movement of the thumb.