The adductor reflex is an intrinsic reflex of the muscles and muscle groups in the thighs and arms known as the adductors. The absence of the reflex indicates damage in the corresponding area of the brain.
What is the adductor reflex?
The adductor reflex is an intrinsic reflex of the muscles and muscle groups in the thighs and arms known as the adductors. The adductor reflex is triggered by a blow to the medial bony prominence of the long tubular bones of the legs or arms. This results in the arms or legs being pulled towards the body. Thus, ‘adduction‘ is the Latin term for ‘drawing close’. In medicine, it means bringing a part of the body closer to the body. This pulling in is done with what are called the adductors. These are the muscles and muscle groups that align the longitudinal axis of the limbs with the longitudinal axis of the body. In this way, the adductors ensure, among other things, that a splayed leg or arm is brought towards the body. The same applies to splayed thumbs and toes. Disorders of the adductors 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 is the nerve of the lumbar plexus and originates in the 2nd to 4th lumbar segment of the spinal cord. The adductor reflex is an intrinsic reflex and thus occurs where the stimulus occurred. Repetition does not weaken the reflex response, unlike the extrinsic reflex.
Function and task
The adductor reflex involves testing the reflexes of the adductors in the thigh. This allows a statement to be made about the function of the obturator nerve. The adductor reflex belongs to the group of intrinsic reflexes. Here, signals from muscle stretching are transmitted via only one synapse to the alpha-motoneuron in the spinal cord and transmitted back to the corresponding muscle via the motor nerves. This results in a reaction of the muscle in the form of a reflex. The reflex leads to a visible twitch of the muscle, which then performs its typical movements. In the case of the adductor muscles, the reflex response is to bring the irritated limb closer to the body. The reflex response in an adductor reflex is physiological. Only an absence or enhancement of this reflex would indicate a disturbance in the transmission of the stimulus. The adductors are in constant interplay with their counterparts, the abductors. Abductors, in turn, are muscle groups that initiate movements away from the body. If the neuronal impulse to the adductors were disturbed, the corresponding limbs would be constantly abducted. A leg that is permanently abducted, for example, cannot be guided in a straight line during forward movement. It can only be moved in outward arcs. Several thigh muscles are required for the adduction of the leg. In addition to adduction movements, rotational movements are also sometimes necessary. For example, the adductor ligament in the thigh includes the five muscle groups Musculus adductor brevis, Musculus adductor longus, Musculus adductor magnus, Musculus gracilis and Musculus pectineus. Adductions, rotations and flexions are coordinated in the interaction of all adductors. In addition to supplying the adductors, the obturator nerve also sensitively innervates the hip joint. Lesions to the obturator nerve can therefore also cause pain in the inner thigh.
Diseases and complaints
The purpose of checking the adductor reflex is to provide the physician with information about possible neurologic diseases. The reflex response is dependent on both the state of excitation of the motor neurons and the intact structures involved in the reflex arc. For example, after a stroke, there is often an increase in muscle intrinsic reflexes, which is manifested 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 a permanent slight abduction of the limbs. Thus, paralysis of the obturator nerve may occur, usually during birth. In this case, during the passage of the fetus through the pelvis, the nerve is sometimes pressed against the internal pelvic wall, where it can be damaged.This is particularly the case if the birth canal is too narrow. Lesions of the obturator nerve can also occur in rare cases during surgical removal of lymph nodes for cancer. The paralysis manifests itself in a lateral splaying of one leg. The leg can no longer be drawn toward the body and is dragged along during forward movement only by lateral arcing movements. In extreme cases, it can also straddle the side. There are also situations in which an obturator nerve block must be performed. This is a regional anesthesia procedure for bladder surgery. For example, if bladder tissue is to be removed by electrocautery, the obturator nerve must be immobilized because it runs directly along the outer wall of the bladder. The electrical stimulation would cause the adductor muscles to contract reflexively. As a result, bladder perforation through the resectoscope could occur. To immobilize the obturator nerve, a local anesthetic is injected at the adductor muscle insertion of the pubic bone. The obturator nerve block can also be used for hip joint pain or adductor spasm conditions. Pain in the thigh can have a variety of causes. For example, damage to the obturator nerve results in isolated pain on the inner thigh. Nerve lesions can result from entrapment of the nerves in a herniated disc or pelvic fracture, among other causes. However, to determine whether adductor pain is truly due to a lesion of the nerves, a comprehensive diagnostic workup is required.
