Adductor reflex

Of the Adductor reflex is an intrinsic reflex of the muscles and muscle groups in the thighs and arms called adductors. The absence of the reflex indicates damage to the corresponding brain area.

What is the adductor reflex?

The adductor reflex is triggered by a blow on the medial protrusion of the long tubular bones of the legs or arms. This involves pulling the arms or legs towards the body. For example, 'adduction' is the Latin name for 'pulling in'. In medicine it means bringing a part of the body to the body. This drawing takes place with the so-called adductors. These are the muscles and muscle groups that align the long axis of the limbs with the long axis of the body. In this way, the adductors ensure, among other things, that a splayed leg or splayed arm is brought up to the body. The same goes for splayed thumbs and toes. Adductor diseases are usually caused by sports injuries.

Strictly speaking, the adductor reflex is mainly related to the reflex reaction of the thigh adductors. Responsible for this is the obturator nerve, which as the nerve of the lumbar plexus (lumbar plexus) has its origin in the 2nd to 4th lumbar segment of the spinal cord.

The adductor reflex is a self-reflex and therefore takes place where the stimulus occurred. In contrast to the external reflex, the reflex response is not weakened by repetition.

Function & task

With the adductor reflex, the reflexes of the adductors in the thigh are checked. This enables a statement to be made about the function of the obturator nerve.

The adductor reflex belongs to the group of self-reflexes. Here, signals from muscle stretching are sent via just one synapse to the alpha motor neuron in the spinal cord and then transmitted back to the corresponding muscle via the motor nerves. The muscle reacts in the form of a reflex. The reflex leads to a visible twitch of the muscle, which then performs its typical movements. With the adductors, the irritated limb is reflexively brought closer to the body.

The reflex response to an adductor reflex is physiological. Only the absence or reinforcement of this reflex would indicate a disturbance in the transmission of stimuli.

The adductors are in constant interplay with their opponents, the abductors. Abductors, in turn, are muscle groups that cause movements away from the body. If the neural impulse to the adductors were disturbed, the corresponding limbs would constantly spread apart. An approximately permanently abducted leg cannot be guided in a straight line when moving forward. It can only be moved in outward arcs.

Several thigh muscles are required for adduction of the leg. In addition to adduction movements, rotational movements are sometimes necessary. The adductor box in the thigh includes the five muscle groups, musculus adductor brevis, musculus adductor longus, musculus adductor magnus, musculus gracilis and musculus pectineus. In the interaction of all adductors, adductions, rotational movements and flexions are coordinated with one another.

In addition to supplying the adductors, the obturator nerve also sensibly innervates the hip joint. Lesions on the obturator nerve can therefore also lead to pain on the inside of the thigh.

Illnesses & ailments

Checking the adductor reflex is intended to give the doctor information about possible neurological diseases. The reflex response depends both on the state of excitation of the motor neurons and on the intact structures involved in the reflex arc. After a stroke, there is often an increase in muscle reflexes, which is noticeable in spasticity. In this context, reflex twitches are also triggered in the neighboring muscle groups. These become noticeable as external reflexes.

A weakening of the muscle reflex is triggered by mechanical or inflammatory processes in the corresponding reflex arc. In the case of the adductors, this can lead to permanent slight splaying of the limbs. Paralysis of the obturator nerve can occur, which usually occurs during childbirth. When the fetus passes through the pelvis, the nerve is sometimes pressed against the inner pelvic wall, which can damage it. This is especially the case when the birth canal is too narrow.

In rare cases, surgical removal of lymph nodes in cancer can lead to lesions of the obturator nerve. The paralysis manifests itself in a lateral spreading of one leg. The leg can no longer be pulled towards the body and is only dragged along with sideways arching movements when moving forward. In extreme cases, it can also slide sideways.

There are also situations in which an obturator nerve block must be performed. This is a regional anesthetic procedure for an operation on the bladder. If, for example, bladder tissue is to be removed by electrocautery, the obturator nerve must be immobilized as it runs directly on the outer wall of the bladder. The electrical stimulation would reflexively contract the adductor muscles. As a result, the resectoscope could perforate the bladder.

To immobilize the obturator nerve, a local anesthetic is injected into the adductor muscle attachment to the pubic bone. The obturator nerve block can also be used for pain in the hip joint or for adductor spasm.

Thigh pain can have many causes. If the obturator nerve is damaged, isolated pain occurs on the inside of the thigh. Nerve lesions can result from entrapment of the nerves in a herniated disc or pelvic fracture. In order to determine whether the adductor pain is really caused by a lesion of the nerve, a comprehensive diagnosis is required.