Anatomy of Posterior Tibial Nerve

BY: Syed Irshad MurtazaClinical Neurophysiology

Dept.AKUH Karachi.

Date: 15-05-2013

Anatomy of Tibial Nerve

• The Tibial Nerve also known as posterior tibial nerve is the largest nerve of sciatic division.

• It is formed by the fibers of L4 and L5 of lumber and the S1, S2 and S3 of sacral ventral (anterior) rami.

Sciatic nerve and hamstring muscles• The sciatic nerve is the broadest nerve of the human

body (2.5cm at its origin). It descends along the back of the thigh and just above the popliteal fossa it separates into its two terminal divisions (Posterior tibial and common fibular(peroneal) nerve).

• Before the bifurcate it supplies 3muscles (hamstring) as semitendinosus, semimembranosus and biceps femoris (long and short head). All hamistring muscles are believed to have tibial nerve components except the short head of biceps femoris which has peroneal component.

Cont’d• The tibial nerve then

descends along the back of the thigh and the popliteal fossa to the distal border of the popliteus muscle, passing with the popliteal artery and vein to enter the leg.

• In the popliteal fossa the nerve gives off branches to gastroc-nemius (S1,S2) , popliteus (L4,L5,S1) and soleus (S1,S2) mucsles.

• Gastrocnemius (S1,S2) is involved in standing, walking, running and jumping. The medial head originates at the medial epicondyle of the femur while the lateral head originates at the lateral epicondyle of femur.

Popliteus Muscle• The popliteus (L4,L5,S1)

muscle in the leg is used to unlock the knee by laterally rotating the femur on the tibia during a closed chain movement (such as one with the foot in contact with the ground).

Popletius muscles

• The Soleus (S1,S2) is

a powerful muscle in the back part of the lower leg (the calf). It runs from just below the knee to the heel, and is involved in standing and walking.

Cutaneous innervation • The sural nerve (S1,S2)

is formed by the joined fibres of tibial and common peroneal nerve and runs down the calf to supply the lateral aspect of the ankle and foot. It ends on the lateral side of the 5th digit.

Muscular supply Below soleus

• Below the soleus muscle the tibial nerve lies close to the tibia bone and supplies the tibialis posterior (L4, L5,S1) first.

• The muscle is mainly responsible for the inversion of the foot.

• The Flexor Digitorum Longus (L5,S1,S2) is the next muscle supplied by tibial nerve after TP, which is situated on the medial side of the leg. At its origin it is thin & pointed, but it gradually increases in size as it descends. This muscle serves to flex (curl) the lesser toes (2nd, 3rd, , 4th & 5th toes) or (flexion of phalanges II-V) without plantar flexion or foot inversion.

Flexor Hallucis LongusFlexor Hallucis Longus..The Flexor Hallucis Longus lexor Hallucis Longus

(L5,S1,S2)(L5,S1,S2) is situated on the fibular side of the leg. It arises from the inferior two-thirds of the posterior surface of the body of the fibula, with the exception of 2.5 cm.

Flexion of the great toe without co’activation of other muscles, activates the flexor hallucis longus.

Passing through tarsal tunnel• The nerve passes into the foot below the

medial malleolus. • Here it is bound down by the flexor

retinaculum in company with the posterior tibial artery. Before entering the tarsal tunnel the nerve splits into 3 different paths. One nerve (calcaneal) continues to the heel, the other two nerve (medial and lateral plantar) continue on the bottom of the foot.

Division of tibial nerve at ankle

Division of tibial nerve at ankle

Medial Plantar Nerve• The medial platar nerve gives off cutaneous

and muscular branches.• Cutaneous branches supply to skin of the sole,

foot, including the the digital branches of the hallux, the 2nd ,3rd and half of the 4th toe.

• The Muscular branches in foot are mainly as,• Abductor hallucis (S1, S2)• Flexor digitorum brevis (S1, S2)• Flexor hallucis brevis (S1, S2) and• First lumbrical (S1, S2)

Origination & Functions– Abductor hallucis (S1, S2)Originates at the medial process of

the calcaneus & serves in abduction of great (big) toe.

Flexor digitorum brevis (S1, S2)

Originates at the medial process of calcaneus & serves in flexion of four lesser toes.

Flexor hallucis brevis (S1, S2)Originates at the plantar surface and

the tendon of the tibialis posterior. It serves in flexion of the great toe.

Lateral Plantar Nerve• The lateral plantar nerve

supplies the skin of the 5th toe and lateral half of the 4th digit.

• The muscular branches supply most deep muscles of the foot including,

• Flexor Digitorum accessorius (S1,S2)

• Abductor Digiti minimi (Quinti) (S1, S2)

• Flexor Digiti Minimi Brevis (S1, S2)

• 2nd and 4th lumbricals (S1, S2) & • Adductor hallucis (S1, S2)

ENTRAPMENT OF TIBIAL NERVE• Entrapment involves pressure on the nerve

where it passes through a narrow structure (tarsal tunnel), the compression is known as tarsal tunnel syndrome (TTS).

• Clinically the following symptoms may be seen• Sensation changes on the bottom of the foot

(sole)• Numbness, tingling, or other abnormal

sensations. • Burning sensation • Pain • Weakness of the knee or foot, difficulty in

walking.

Recording techniques for Motor NCS

• Tibial Nerve is recorded from the abductor hallucis muscle.

• It is stimulated from the ankle and knee.• The normative values are• Distal Latency: ≤ 5.8msec• Conduction velocity: ≥ 41msec• CMAP amplitudes: ≥ 4mV• F-wave latency: ≤ 5msec.

RECORDING TECHNIQUES FOR MEDIAL AND LATERAL PLANTAR (Mixed Nerves)

Recording site. Medial ankleG1 is placed on tibial nerve above & posterior to the medial malleolus.G2 is placed 3-4 cm proximally.G3 is placed between active recording & stimulating electrodes

Stimulation sites. Medial sole (medial planter nerve)Lateral sole (lateral plantar nerve).

Distance14cm from the recording electrode. Measure 10cm from the recording site in to the sole of the foot. Then additional 4cm on a line drawn parallel to the web space between the 1st & 2nd toes for medial plantar, while additional 4cm on a line drawn parallel to the web space between the 4th & 5th toes for lateral plantar nerve.

NCS technique for Plantar nerves

Medial plantar mixed nerve study

Lateral planter mixed nerve study.

Recording technique for sural sensory NCS

• Recording Site: Posterior Ankle• G1 placed posterior to the lateral malleolus.• G2 placed 3-4 cm distally• G3 place between G1 & stimulating electrodes• Stimulation Site: Posterior-lateral calf• Distance: 14Cm• Normative Data: Peak latency: ≤4.4msec• SNAP amplitude: ≥ 6uv• Conduction velocity: ≥35-40uV

Thanks for the patience.

• Never underestimate others, nor allow others underestimating you, because one might do it better than

you, and at the same time you may do it better than others. BY. IM