|Using the reflex hammer
Deep tendon reflex examination entails the use of a reflex hammer to strike a tendon or muscle in order to elicit a reflexive contraction of the same muscle. When using a reflex hammer, it is important to adhere to the following recommendations:
Variables of contact
- The force of your stimulus must be sufficient enough to elicit a reflex and be kept consistent to provide for a reproducible response.
- Allowing a weighted or Queen Square reflex hammer to fall by the force of gravity from a distance of 10 to 12 cm will typically provide sufficient force.
- Allowing a smaller, unweighted Taylor or tomahawk style reflex hammer to swing loosely between the thumb and forefinger and moving the hammer and wrist through a 45 to 60 degree arc will typically provide sufficient force.
- Use the least amount of force that is necessary to elicit a definitive and consistent response.
- Do not continue to strike the patient if you fail to elicit a response with proper and repeated testing.
- Compare each reflex with its contralateral counterpart so that any asymmetries can be detected and documented.
- If indicated, repeat each test 5 to 10 times in order to standardize the point of contact and force, confirm reproducibility of the response, and identify changes that may occur with repeated testing that are a function of pathology (i.e., spinal nerve root pathology).
- A non-latex reflex hammer is preferred.
Certain reflexes are readily elicited by striking the tendon connected to the muscle with the reflex hammer, while others are readily elicited by directly striking the muscle with the reflex hammer. In some instances, the clinician’s finger may be placed between the hammer and muscle/tendon (i.e., brachioradialis, biceps, adductor) to cushion the force and/or to palpate a response which might be invisible to the naked eye. The clinician should match the contacting surface of the reflex hammer (i.e., broad or small tip) to the size of the tendon or muscle being tested.