Symptoms of tibial nerve damage

The tibial nerve (n. tibialis) is formed by fibers of the LIV-SIII spinal roots. In the distal part of the popliteal fossa, the medial cutaneous nerve of the leg branches off from the tibial nerve. It passes between the two heads of the gastrocnemius muscle and pierces the deep fascia in the middle third of the posterior surface of the leg. At the border of the posterior and lower thirds of the leg, the lateral cutaneous branch of the common peroneal nerve joins this nerve, and from this level it is called the sural nerve (n. suralis).

The nerve then runs along the Achilles tendon, giving off a branch to the posterolateral surface of the lower third of the leg. At the level of the ankle joint, it is located behind the tendons of the peroneal muscles and gives off external calcaneal branches to the ankle joint and heel. On the foot, the sural nerve is located superficially. It gives off branches to the ankle and tarsal joints and supplies the skin of the outer edge of the foot and the fifth toe to the level of the terminal interphalangeal joint. On the foot, the sural nerve also communicates with the superficial peroneal nerve. The area of innervation of the sural cervix depends on the diameter of this anastomosis. It can include a significant part of the dorsum of the foot and even the adjacent surfaces of the third and fourth interdigital spaces.

Symptoms of sural nerve damage include pain, paresthesia, and a feeling of numbness and hypoesthesia or anesthesia in the area of the outer edge of the foot and the fifth toe. There is pain on palpation corresponding to the site of nerve compression (behind and below the outer ankle or on the outer part of the heel, at the outer edge of the foot). Finger compression at this level causes or increases pain in the area of the outer edge of the foot.

The initial sections of the tibial nerve supply the following muscles: triceps surae, long flexor of the fingers, plantar, popliteal, posterior tibialis, long flexor of the big toe, etc.

The triceps surae muscle is formed by the gastrocnemius and soleus muscles. The gastrocnemius muscle flexes the lower limb at the knee and ankle joints.

Tests to determine the strength of the calf muscle:

1. the subject, lying on his back with his lower limb straightened, is asked to bend it at the ankle joint; the examiner resists this movement and palpates the contracted muscle;
2. The subject, lying on his stomach, is asked to bend his lower limb at the knee joint at an angle of 15°; the examiner resists this movement.

The soleus muscle flexes the lower limb at the ankle joint.

Test for determining the strength of the soleus muscle: the subject, in a prone position with the lower limb bent at an angle of 90° at the knee joint, is asked to bend it at the ankle joint; the examiner resists this movement and palpates the contracted muscle and tendon.

The plantaris muscle, with its tendon, is woven into the medial part of the Achilles tendon and is involved in flexion at the ankle joint.

The popliteus muscle is involved in flexion at the knee joint and inward rotation of the lower leg.

The posterior tibialis muscle adducts and elevates the inner edge of the foot (supinates) and promotes flexion at the ankle joint.

Test for determining the strength of the posterior tibialis muscle: the subject lies on his back with the lower limb straightened, flexes it at the ankle joint and simultaneously adducts and lifts the inner edge of the foot; the examiner resists this movement and palpates the contracted muscle and the tense tendon.

The long flexor digitorum flexes the distal phalanges of the second through fifth toes.

Test for determining the strength of the long flexor of the fingers: the subject, lying on his back, is asked to bend the distal phalanges of the second to fifth toes at the joint; the examiner prevents this movement and holds the proximal phalanges straight with the other hand. The long flexor of the big toe bends the first toe; its function is tested similarly.

The internal calcaneal cutaneous branches extend from the tibial nerve slightly above the medial malleolus, innervating the skin of the posterior calcaneal region and the posterior part of the sole. At the level of the ankle joint, the main trunk of the tibial nerve passes through a rigid osteofibrous tunnel - the tarsal canal. This canal goes obliquely downwards and forwards, connecting the ankle joint area with the sole, and is divided into 2 floors: the upper - malleolar and the lower - submalleolar. The upper floor is limited externally by the bone-articular wall. From the inside, the upper floor is limited by the internal annular ligament formed from the superficial and deep aponeurosis of the leg. The lower floor is limited externally by the internal surface of the calcaneus, from the inside - by the adductor muscle of the big toe, enclosed in the duplication of the internal annular ligament. The tarsal canal has two openings: upper and lower. The tendons of the posterior tibial muscle, the long flexor of the fingers and the long flexor of the hallucis, as well as the posterior tibial neurovascular bundle pass through the canal. It is located in a fibrous case and includes the tibial nerve and the posterior tibial artery with its satellite veins. In the upper floor of the tarsal canal, the neurovascular bundle passes between the tendons of the long flexor of the hallucis. The nerve is located outside and behind the artery and is projected at an equal distance from the calcaneal tendon to the posterior edge of the medial malleolus. In the lower floor of the canal, the neurovascular bundle is adjacent to the posterolateral surface of the tendon of the long flexor of the hallucis. Here, the tibial nerve divides into terminal branches - the internal and external plantar nerves. The first of them innervates the skin of the plantar surface of the inner part of the foot and all phalanges of the toes, the dorsal surface of the terminal phalanges of the first to third and the inner half of the fourth toe, as well as the short flexors of the toes, which flex the middle phalanges of the second to fifth toes, the short flexor of the big toe, the muscle that abducts the big toe, and the first and second lumbrical muscles. The external plantar nerve supplies the skin of the outer part of the plantar surface of the foot, the plantar surface of all phalanges of the toes, and the dorsal surface of the terminal phalanges of the fifth and outer half of the fourth toe. Motor fibers innervate the quadratus plantaris; flexion is facilitated by the first to fourth interosseous and second to fourth lumbrical muscles, the muscle that abducts the little toe, and, in part, the short flexor of the little toe. The skin of the heel area is innervated by the internal calcaneal nerve, which branches off from the common trunk of the tibial nerve slightly above the tarsal canal.

When the common trunk of the tibial nerve is affected, muscle paralysis develops in the popliteal fossa and the ability to flex the lower limb at the ankle joint, at the joints of the distal phalanges of the toes, the middle phalanges of the second through fifth toes and the proximal phalanx of the first toe is lost. Due to the antagonistic contraction of the extensors of the foot and toes innervated by the peroneal nerve, the foot is in a position of extension (dorsal flexion); the so-called heel foot (pes calcaneus) develops. When walking, the patient rests on the heel, rising on the toes is impossible. Atrophy of the interosseous and lumbrical muscles leads to a claw-like position of the toes (the main phalanges are extended at the joints, and the middle and terminal ones are bent). Abduction and adduction of the toes are impossible.

When the tibial nerve is damaged below the branches that branch off to the gastrocnemius muscles and long flexors of the toes, only the small muscles of the plantar part of the foot are paralyzed.

For topical diagnostics of the level of damage to this nerve, the zone of sensory impairment is important. Sensory branches sequentially depart for innervation of the skin on the back of the leg (medial cutaneous nerve of the calf - in the popliteal fossa), the outer surface of the heel (medial and lateral calcaneal branches - in the lower third of the leg and at the level of the ankle joint), on the outer edge of the foot (lateral dorsal cutaneous nerve), on the plantar surface of the foot and toes (I - V common plantar digital nerves).

When the tibial nerve is damaged at the level of the ankle joint and below, sensory disturbances are localized only on the sole.

In case of partial damage to the tibial nerve and its branches, causalgic syndrome often occurs. Excruciating pain extends from the back of the leg to the middle of the sole. The touch on the plantar side of the foot is extremely painful, which interferes with walking. The patient rests only on the outer edge of the foot and on the toes, limping when walking. The pain can radiate throughout the lower limb and sharply increase with light touch to any area of the skin on this limb. Patients cannot walk, even leaning on crutches.

Often the pain is combined with vasomotor, secretory and trophic disorders. Atrophy of the muscles of the back of the leg and interosseous muscles develops, as a result of which the metatarsal bones clearly protrude on the dorsum of the foot. Achilles and plantar reflexes decrease or disappear.

When the terminal branches of the tibial nerve are affected, reflex contracture of the affected limb with swelling, hyperesthesia of the skin and osteoporosis of the bones of the foot is sometimes observed.

Most often, the tibial nerve is affected in the tarsal canal area by the mechanism of tunnel (compression-ischemic) syndrome.

In tarsal tunnel syndrome, pain comes to the fore. Most often, it is felt in the back of the leg, often in the plantar part of the foot and toes, and less often radiates to the thigh. Paresthesia is observed along the plantar surface of the foot and toes. Here, a feeling of numbness often occurs and a decrease in sensitivity is detected within the innervation zone of the external and / or internal plantar nerve, and sometimes in the area supplied by the calcaneal nerve. Less often than sensory disorders, motor disorders occur - paresis of the small muscles of the foot. In this case, flexion and spreading of the toes is difficult, and in advanced cases, due to muscle atrophy, the foot takes on the appearance of a clawed paw. The skin becomes dry and thins. In tarsal tunnel syndrome, light percussion or finger compression in the area between the inner malleolus and the Achilles tendon causes paresthesia and pain in the plantar region of the foot, the latter can be felt in the back of the leg. Painful sensations are provoked both by pronation and simultaneously formed extension of the foot, as well as by forced plantar flexion of the first toe against the action of the resistance force.

With the specified tunnel syndrome, sensory disorders in the heel area occur rarely. Weakness of flexion of the shin and foot, as well as hypoesthesia along the posterior outer surface of the shin are signs of damage to the tibial nerve above the level of the tarsal canal.

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