Definition
A falling hand is a condition in which damage to the radial nerve impairs the active movement of the wrist and finger joints in the direction of the back of the hand, i.e. the lifting of the hand and stretching of the fingers. The most common causes of radial nerve palsy (technical term for damage to the radial nerve) are fractures of the humerus or dislocations of the shoulder.
Causes for a drop hand
If a drop hand is present, the doctor will first determine the extent of the impairment by means of functional tests. This involves checking whether there is still a residual ability to stretch the hand and fingers and whether the muscle reflexes can still be triggered. The physician will then examine whether there are any other functional limitations.
The focus here is on the examination of elbow extensibility and skin sensitivity on the back of the hand and forearm. In this way, the physician can already estimate where the damage is located and how severe it is. The physician can also draw important conclusions about a possible cause or the course of the accident from the patient’s reports.
If in doubt, a so-called electromyography can then be performed. This involves using surface or needle electrodes to examine the extent to which the impulses from the radial nerve still reach the muscles responsible for extending the hand and fingers. From this, the extent and prognosis of nerve damage can be estimated relatively accurately.
Alternatively, the nerve conduction velocity (NLG) can be measured using electroneurography. The nerve conduction velocity (NLG) of a nerve refers to the speed with which a nerve can convey its information. It is often reduced when the nerve is damaged.
If the nerve is completely severed, it is obvious that no more information can be transmitted, so that the NLG drops to 0. In the case of a drop hand, measurement of the NLG can be considered if, after anamnesis and functional tests, there is still uncertainty about the diagnosis or the extent of the nerve damage. For this purpose, two electrodes are first placed on the hand, one in front and one behind the suspected site of damage.
Then an impulse is emitted via the first electrode and the time that elapses until the impulse reaches the second electrode is measured. The comparison with standard values then allows the conclusion to be drawn as to whether damage is present in the examined nerve area and, if so, how pronounced it is. You can read more about this procedure on our page on this topic: Electroneurography
