Courtesy: Prof Nabil Ebraheim
Tibialis Anterior Muscle
- The Tibialis Anterior muscle is located within the anterior extensor compartment of the leg.
- Origin: From upper half and lateral condyle of the tibia
- Insertion: into the medial cuneiform and first metatarsal base of the foot
- Tibialis anterior muscle comes from the lateral surface of the tibia and at the ankle, it is the most medial structure.
- The tendon of the Tibialis anterior along with other extensor tendons pass under the superior and inferior extensor retinaculum.
A mnemonic phrase to remember the order of artery, nerve, tendon at the anterior ankle
Tom Has Very Nice Dog and Pig
T- Tibialis Anterior
H- Flexor Hallucis Longus
V-Vessel(artery)
N-Nerve
D- extensor Digitorum Longus
P- Peroneus Tertius
Innervation: Deep Peroneal Nerve.
NB: Tibialis Anterior Muscle is more L4 than L5
Function:
1)Dorsal flexion of the ankle and inversion of hindfoot
A loss of function of muscle due to tear of the tendon or nerve injury can lead to FOOT DROP.
2)Tibialis anterior dorsiflexes the foot in preparation for heel strike during the late swing phase of the gait and it eccentrically contracts after heel strikes to slow progression.
Foot drop occurs through the interruption of nerve supply due to pelvic fracture affecting L4/L5 nerve root which leads to loss of sensation in the medial foot , loss of patellar tendon reflex, weakness of tibialis anterior muscle( weakness of foot inversion and ankle dorsiflexion)
*posterolateral disc herniation-L3, L4 ; *Foraminal disc herniation-L4, L5 tibialis anterior muscle will be affected and cause foot drop.
*sciatic Nerve injury-
To differentiate between a common peroneal injury that is high at the sciatic nerve level and the common peroneal nerve injury that is at knee-Test the short head of biceps femoris muscle and if the short head of biceps femoris muscle is working then the injury is at the knee and not at hip.
Rupture of tibialis anterior muscle:
- It is an uncommon disorder that may cause loss of ankle dorsiflexion
- It may be caused due to laceration or a closed rupture.
- Closed rupture may occur due to strong eccentric contracture in young patients or attenuation attrition rupture in older patients .
- The older patients who may have diabetes , inflammatory arthritis or may have had steroid injections.
- Patient may present with difficulty clearing the foot during gait with chronic rupture.
- In acute rupture you will hear a POP and there will be swelling of anterior ankle
Clinical Features:
- Foot drop , steppage gait , pseudo tumor , anterior ankle pain , weak dorsiflexion , no tendon is felt in resisted dorsiflexion
- MRI will show that tendon is missing.
Treatment :
1. Partial tear- cast or boot can be used
2. Complete tear- AFO in low demand patients however surgical repair proves to be successful in elderly patients
3. Surgery: Best choice
When there is chronic rupture, autograft can be done or an allograft attached to distal stump or mid foot
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