What Is a Reflex Hammer?

The reflex hammer is a common medical instrument used for eliciting the response of deep tendon reflexes. Developed in the 1800s, it arguably is one of the oldest and most widely recognized basic exam tools. This well-known piece of equipment helps physicians test neurological function and judge abnormalities in the central and peripheral nervous system. Most people know a reflex hammer as the tool that a doctor uses to tap a patient below the kneecap, but they also can be used on other parts of the body.

There are many shapes and models of the basic reflex hammer. The Taylor, or tomahawk hammer, is the most widely known in the United States. It consists of a triangular rubber head affixed to a straight, metallic handle.

Another popular reflex hammer is the Queen Square. The Queen Square hammer was developed for use in London's National Hospital for Nervous Diseases, now known as the National Hospital for Neurology and Neurosurgery. It is a plastic cane with a sharp taper on one end and a small metal and plastic disc on the other end. The Queen Square is the hammer most popularly chosen by neurologists in the United Kingdom.

Other reflex hammers developed over the years include the Babinski, the Troemner, the Berliner and the Buck. Each hammer is designed to elicit slightly different reflex responses, including plantar, myotatic and cutaneous reflexes. These reflexes involve different areas of the body, including the foot, tendons and the skin. A more recent addition to the market includes a hammer that claims to combine the functionality of five different hammers into one. It features a rotating adjustable head and meets the testing abilities of the Taylor, Troemner, Buck, Babinski and Berliner hammers.

Testing for deep tendon reflexes using a reflex hammer is a simple operation. The physician utilizes impulses from the hammer to stretch the muscle and tendon. When the hammer taps the muscle tendon, a response known as a reflex arc between the muscle and the spine or brain stem causes the muscles to contract immediately. Perhaps the most well-known reflex test occurs when the hammer is applied directly below the patient's kneecap, causing the lower leg to swing or kick.

When a doctor performs a reflex exam, he or she is looking for a well-timed, normal motor response. If the patient displays a weak or diminished response to reflex testing, it is known as hyporeflexia. Patients with the opposite response, a reflex that repeats or is exaggerated, display a condition known as hyperreflexia. Hypo- and hyperreflexia might indicate injury, trauma or other problems along the neural motor pathways.