History of the Reflex Hammer

The history of reflex hammers begins in 1875, when Erb and Westphal described the clinical utility of the muscle stretch reflex. At that time, it was realized that a tool would be required to test reflexes. Heinrich Erb recommended testing the patellar-tendon reflex (the knee-jerk reflex we all know and love) by striking the tendon with either a finger or a percussion hammer. Carl Friedrich Otto Westphal similarly recommended this reflex, by striking the patellar ligament “lightly but quickly with a finger” best when the index finger is put on top of the middle finger and the former is accelerated downward – or even more effectively with a percussion hammer.” [Author’s note: after hours of twisting my fingers around, I have yet to figure out what he meant]

In the 1880’s, William Gowers coined the phrase “myotatic reflex” for this knee-jerk reflex, and he recommended eliciting this reflex by striking the patellar tendon with either the side of the hand or the rubber edge of the end of a stethoscope. I know that most physicians have experimented with these techniques, as it is very common (and disgraceful in my opinion) to be without a reflex hammer handy.

Over the next several decades, percussion hammers became the preferred tools for eliciting reflexes. Charcot even recommended the particular Skoda hammer for obtaining the knee-jerk reflex. Joseph Babinski (Charcot’s pupil) was an advocate of hammers. Rather than use the side of the hand, he felt “one would be better served to use a percussion hammer.” Bernhard Berliner (like myself) was an adamant advocate of hammers. He is quoted as having said “it is not very elegant to percuss the knee or achilles tendon with a paper weight, the edge of a large electrode, the foot of a laboratory stand, a table lamp, or similar devices.”

Because percussion hammers were not specifically designed for eliciting reflexes, it is to be expected that hammers would be developed specifically for this purpose. It was quickly realized that the percussion hammer had too small a head and was too light to securely strike the desired tendon. In addition to greater weight and larger striking area, some hammer designers added a pointed tip to facilitate testing of cutaneous reflexes, a pin, a brush, and a ruler along the handle.

The first “reflex hammer” was probably designed by John Madison Taylor in Philadelphia in 1888. Krauss, Berliner , Dejerine, Stuempell, Troemner, Babinski, Ebstein, Wintle, and others developed reflex hammers which enjoyed popularity.

The most consistent new feature of these reflex hammers was their greater weight. The Taylor hammer, at approximately 60 – 70 grams, was considered heavy when it was introduced. The later hammers were even heavier, weighing between 80 and 140 grams. Some contemporary versions of the Troemner and Queen Square hammers weight over 200 grams! The added weight of the head, and in some cases a longer flexible handle, increased the hammer’s effectiveness. Berliner even claimed that his hammer “allows, in almost all instances, the elicitation of an existing Achilles reflex through the patient’s boots.” Now that’s a reflex hammer.

Primary reference: Lanska, DJ; Neurology Nov 1989 p1542-9; The History of Reflex Hammers

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