What is the book test for ulnar nerve?
The book test for the ulnar nerve is a physical examination of the hand to test for the palsy of the ulnar nerve specifically, the action of the adductor pollicis muscle.
Book test mainly tests the strength of the adductor pollicis muscle. As you can see in the diagram, the adductor pollicis muscle is innervated by the ulnar nerve. In the ulnar nerve palsy, the adductor pollicis muscle gets weakened, which results in reduced functionality and muscle weakness of the pinch grip.
The adductor pollicis muscle’s primary function is to perform the adduction of the thumb from an abducted position. This activity is vital for purposes that need pinching and grasping. However, in case if the book test comes out to be positive. The flexor pollicis longus muscle will act as a substitute in place of the adductor pollicis muscle. And therefore induces the thumb to go into hyperflexion.
How is the book test for ulnar nerve performed?
The patient is asked to grasp a book firmly between the thumb and index finger (pinch grip) with both hands. You can also perform this test by holding a paper or card between the thumb and index finger with both hands. After that, the examiner then tries to pull the object(either book, card or paper) out of the patient’s hand.
- If the ulnar nerve is intact. Then the individual will be able to maintain a hold on the object (book, paper, or card) without any difficulty.
- However, in the ulnar nerve palsy, the patient will suffer difficulty in maintaining a hold. The flexor pollicis longus muscle of the thumb tries to compensate for this loss of power to maintain the grip pressure by flexing/bending the thumb’s tip at the Interphalangeal joint. Therefore, this sign is known as ‘Froment’s Sign’ or ‘book test’.
There is another test similar to Froment’s sign, which is known as Jeanne’s sign. It is also seen in reaction to pinch forces.
My self Ritvik Verma and I am a Physiotherapist and the founder of www.physio-study.com. I completed my bachelor’s of physiotherapy from Integral University Lucknow and an internship at KMC Hospital Meerut.
Then I worked in the Physiotherapy Department of Lovee Shubh Hospital (Lucknow) for one year. Then I joined Holistic Touch Physical Therapy & Wellness Clinic and worked there for more than six months.
I am running my clinic and writing blogs on my website, www.physio-study.com, in my hometown, Lakhimpur Kheri.