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Special Test

Lumbar Spine Nerve Roots

Lumbar Spine Nerve Roots consist of 5 roots pairs (L1, L2, L3, L4 and L5), each root traverses the respective disc space above the named vertebral body and exits the respective foramen under the pedicle.

Lumbar Spine Nerve Roots Motor Examination

Each Lumbar Spine Nerve Root supplies a specific dermatome of the lower extremity (sensory supply) and a specific group of muscle (motor supply).

See Also: Spine Movements

L1, L2 Nerve Roots (Hip Flexion)

L1 and L2 nerve roots supply the iliopsoas muscle, the primary flexor of hip.

To test the iliospoas, the patient is asked to sit by the side of the examination table with his knees flexed to 90°. The patient is now instructed to lift his thigh off the table (with the knee in flexion) while the examiner gives a downward pressure over the patient’s knee with both hands. In a normal patient, the examiner should be able to overcome the patient’s effort with some difficulty.

See Also: Thomas Test
Assessing L1 L2 motor function -iliopsoas strength
Assessing L1 L2 motor function – iliopsoas strength

L3 Nerve Root (Knee Extension)

L3 nerve root is evaluated by testing the strength of quadriceps muscle.

The patient is asked to sit by the edge of the examination table with the knee flexed to 90°. The examiner now gives a downward pressure on the patient’s leg just above the ankle while the patient tries to extend his knee. In a normal patient, quadriceps muscle can be seen and felt contracting with the examiner being unable to initiate knee flexion.

See Also: Prone Knee Flexion Test
Assessing L3 motor function -quadriceps strength
Assessing L3 motor function – quadriceps strength

L4 Nerve Root (Ankle Dorsiflexion)

L4 nerve root is assessed by testing the strength of tibialis anterior muscle.

With the patient seated by the side of the table with his knees at 90°, he is asked to maximally dorsiflex the ankle while the examiner tries to plantar flex the ankle. Comparison of both the sides can be done by testing both ankles simultaneously with the patient lying supine.

It can also be screened by asking the patient to walk on his heels with the toes held high off the floor.

See Also: Ankle Range of Motion
Assessing L4 motor function tibialis anterior strength
Assessing L4 motor function – tibialis anterior strength
Assessing L4 motor function - heel walking
Assessing L4 motor function – heel walking

L5 Nerve Root (Toe Extension, Hip Abduction)

L5 nerve root can be assessed by testing for long toe extensors (extensor hallucis longus and extensor digitorum longus) and hip abductor (gluteus medius).

With the patient lying supine on the examination table, the examiner instructs the patient to extend the great toe while he tries to flex the toe by applying pressure over the dorsal aspect of the distal phalanx of great toe. Both the legs are examined simultaneously and are compared to evaluate the strength of extensor hallucis longus.

Assessing L5 motor function -extensor hallucis longus
Assessing L5 motor function – extensor hallucis longus

The extensor digitorum longus can be assessed by asking the patient to extend the toes as far as possible while the examiner tries to passively flex the toes with his fingers.

Assessing L5 motor function -extensor digitorum longus
Assessing L5 motor function – extensor digitorum longus

Gluteus medius is evaluated by assessing the strength of hip abduction. With the patient lying in a lateral position on the examination table, the examiner instructs the patient to abduct his lower limb keeping the knee in extension while the examiner tries to push the thigh back towards the table.

See Also: Ankle Anatomy
Assessing L5 motor function -gluteus medius
Assessing L5 motor function – gluteus medius

Lumbar Spine Nerve Roots Sensory Examination

The approximate areas of sensory innervations from the lumbar and sacral nerve roots are shown.

spinal nerve dermatomes

Reflex Examination

Cremasteric Reflex

The patient lies supine while the examiner strokes the inner side of the upper thigh with a pointed object. The test is negative if the scrotal sac on the tested side pulls up. Absence or reduction the reflex bilaterally suggests an upper motor neuron lesion.

A unilateral absence suggests a lower motor neuron lesion between L1 and L2. Absences have increased significance if they are associated with exaggerated deep tendon reflexes.

Patellar Tendon Reflex (L4)

The patellar tendon reflex is usually assessed with the patient seated on the side of the examination table with the knees flexed and the feet dangling. The examiner then sharply strikes the midportion of the patellar tendon with the flat side of a rubber reflex hammer. The examiner’s other hand may rest lightly on the patient’s quadriceps to feel for a muscle contraction. In a normal patient, there is visible contraction of the quadriceps with extension of the knee.

Patellar tendon reflex- L4 nerve root
Patellar tendon reflex- L4 nerve root

Tibialis Posterior and Medial Hamstring Reflex (L5)

The tibialis posterior reflex is evaluated in the seated patient. The examiner holds the patient’s foot in a small amount of eversion and dorsiflexion and strikes the posterior tibial tendon just below the medial malleolus. The examiner may also place a finger on the posterior tibial tendon and strike the finger instead of striking the tendon directly. When the reflex is elicited, a slight plantar flexion inversion response is noted.

Tibialis posterior reflex -L5 nerve root
Tibialis posterior reflex -L5 nerve root

To elicit the medial hamstring reflex, the patient is placed in the prone position. The examiner passes one hand underneath the patient’s leg and places the thumb of that hand on the semitendinosus tendon in the popliteal fossa. The patient’s leg is allowed to rest on the examiner’s forearm so that the patient’s knee is somewhat flexed. The examiner then strikes the thumb, which is pressing on the semitendinosus tendon, with the pointed end of the hammer. When the reflex is elicited, the examiner feels a contraction transmitted through the semitendinosus tendon or actually sees slight flexion of the knee take place.

See Also: Hamstring Flexibility
Medial hamstring reflex -L5 nerve root
Medial hamstring reflex -L5 nerve root

References

  1. Sassack B, Carrier JD. Anatomy, Back, Lumbar Spine. [Updated 2021 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557616/
  2. Basit H, Reddy V, Varacallo M. Anatomy, Back, Spinal Nerve-Muscle Innervation. [Updated 2022 Feb 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538322/
  3. Sarvdeep S. Dhatt, Sharad Prabhakar – Handbook of Clinical Examination in Orthopedics. An Illustrated Guide-Springer Singapore.
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