Numbness of the thumb after arm fracture may be caused by nerve damage or swelling and bleeding at the fracture site, which should be treated by medication and physical therapy under the guidance of physician after clarifying the severity of the condition. 1. Nerve injury: the degree of nerve injury can be clarified through electromyography. If the symptoms are mild, methylcobalamin and adenosylcobalamin can be used under the guidance of the physician; if the symptoms are more serious, methylcobalamin and other drugs can be taken together with local massage, acupuncture and other physical therapy to promote nerve recovery. 2. Swelling and bleeding at the fracture site: after arm fracture, hematoma is easy to form at the fracture site, affecting the peripheral circulation of the fingers, thus causing numbness of the little finger, the fracture should be reset in time, and the injury can be fixed with a brace, and ibuprofen, paralysis capsules can be taken to improve the hematoma of the wound and alleviate the numbness of the little finger. If the numbness of the thumb occurs after the arm fracture, you should go to the hospital in time for examination, to clarify the cause of numbness, and carry out targeted treatment as soon as possible to prevent the condition from aggravating and causing other hand problems.