Courtesy: Prof Nabile Ebraheim, University of Toledo, Ohio, USA
Anatomy of the Tibialis Posterior Muscle
The tibialis posterior is a relatively small muscle located within the back of the calf.
• The tibialis posterior is located within the posterior compartment of the leg.
• Some believe that the tibialis posterior muscle may have its own compartment.
Tibialis Posterior
• ORIGIN – It originates from the upper 2/3rd of the back of the tibia lateral to the vertical line and below the soleal line.
• It also originates from FIBULA – the upper 2/3rd medial surface of the fibula, deep transverse fascia, adjacent intramuscular septa, and posterior surface of the interosseous membrane.
Tibialis Posterior
• INSERTION -The muscle, and then the tendon of the tibialis posterior, travels distally running posterior to the medial malleolus of the tibia within the groove.
• It then splits into a medial and lateral part.
• The medial insertion (important) of the tendon is inserted into the tuberosity of the navicular bone and the medial cuneiform bone.
• The lateral part of the tendon inserts into the intermediate and lateral cuneiforms as well as the base of the 2nd, 3rd and 4th metatarsal bones.
INNERVATION
• The muscles of the posterior compartment, including the tibialis posterior, are supplied by the posterior tibial nerve (L4 – L5).
FUNCTION
• The action of the tibialis posterior is to:-
1. Invert the foot.
2. Assists in plantar flexion.
3. Maintains the medial longitudinal arch.
• The major antagonist to the tibialis posterior muscle (INVERSION) is the peroneus brevis muscle (causes EVERSION of the foot).
• The tendon of the tibialis posterior may become entrapped during lateral subtalar dislocation.
POSTERIOR COLLICULAR FRACTURE
• With a posterior collicular fracture of the medial malleolus, the tibialis posterior tendon and the flexor digitorum longus tendon support the medial malleolar fragment.
• This is why the fragment does not displace significantly.
TIBIALIS POSTERIOR TENDON RUPTURE
• When the tendon ruptures and the condition is advanced, it has the classic finding of “Too Many Toes” sign because of collapse of the medial longitudinal arch, hind foot valgus, forefoot abduction and varus.
• Degeneration of the tibialis posterior tendon occurs in the watershed area of the tendon distal to the medal malleolus.
POSTEROLATERAL APPROACH TO THE TIBIA
• The posterolateral approach can be used for open plate fixation of the tibia on its posterior surface.
• This may be necessary when the anterior soft tissues are compromised.
• This approach is often also utilized for treatment of non – unions, especially infected nonunions, with posterolateral bone grafting.
• It allows access to both the tibia and fibula and creates synostosis between the two bones.
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