Patients with neck pain due to cervical nerve root irritation may have accompanying wrist, hand and finger pain.
Pain and spasm or stiffness in the flexor digitorum superficialis muscle will lead to difficulty in making a fist. Both the flexor digitorum superficialis and flexor digitorum profundus muscles must be able to contract well to make a fist.
Whenever there is difficulty in making a fist either due to stiffness, pain or spasm in the muscles that flex the fingers, it is essential to examine the muscles that must balance the action of the finger flexors.
The muscles on the dorsal aspect of the forearm and wrist, namely the wrist and finger extensors must undergo lengthening contractions to balance the action of the finger flexors.
The dorsal forearm muscles are needed to contract well to stabilize the wrist while making a fist. Therefore any problems in the function of the wrist and finger extensors, need to be worked on simultaneously to increase the function of the finger flexors.
You will note that when your wrist is bent down (flexed), you will have a hard time making a fist and your grip will be weak. Your wrist has to be bent-up (extended) for you to be able to make a fist with a strong grip.
The flexor digitorum superficialis is responsible for bending (flexing) the middle phalanx. The best way to test it is to hyperextend the knuckle (metacarpophalangeal) joint. With the metacarpophalangeal joint pushed back into hyperextension, the action of the flexor digitorum profundus is made silent. In this position, only the flexor digitorum superficialis can contract.
Flexor digitorum superficialis is supplied by the median nerve (C8, T1 roots).