Tarsal Tunnel | Tibial Nerve | Posterior Malleolus and Distal Tibia
Surgical Imaging
The tarsal tunnel contains structures in a precise order from anterior to posterior: Tibialis posterior (Tom), Flexor digitorum longus (Dick), Posterior tibial artery and tibial nerve (And Very Nervous), Flexor hallucis longus (Harry). The tibial nerve lies between FDL and FHL and must be protected.
The tibial nerve provides motor innervation to the posterior compartment and sensation to the sole of the foot. Injury causes plantarflexion weakness, toe flexion loss, and sole numbness. Identify the nerve early, use vessel loop protection, and avoid prolonged retraction.
The posterior malleolus provides the posterior tibial plafond and attachment for the posterior inferior tibiofibular ligament. Fragments greater than 25 percent of the articular surface or with greater than 2 mm step-off require fixation. The posteromedial approach allows direct buttress plating.
The approach can be performed prone (excellent for bilateral posterior access) or supine with leg externally rotated (allows combined anteromedial approach without repositioning). Knee flexion relaxes the gastrocnemius and improves access.
In pilon fractures, the posteromedial approach addresses the posteromedial fragment and medial malleolus. Often combined with anterolateral or anteromedial approaches. Staged soft tissue management is critical - wait for wrinkle test before definitive fixation.
The approach provides excellent exposure for posterior tibial tendon and FHL tendon procedures including debridement, repair, and transfer. Tarsal tunnel release for posterior tibial nerve compression is performed through the same interval.
At a Glance
The posteromedial approach to the ankle provides direct access to the posteromedial distal tibia, medial malleolus, and posterior malleolar fragment through the tarsal tunnel. The approach is essential for fixation of posterior malleolus fractures, posteromedial pilon fragments, and procedures involving the posterior tibial or FHL tendons. The critical structure is the tibial nerve, which must be identified and protected throughout. The mnemonic Tom, Dick And Very Nervous Harry describes the order of structures within the tarsal tunnel from anterior to posterior. The approach can be performed prone or supine with external rotation and is frequently combined with anterior approaches for complex pilon fractures.
TARSALTARSAL TUNNEL CONTENTS - Tom Dick And Very Nervous Harry
Hook:Tom Dick And Very Nervous Harry - always identify the nerve before retraction!
POSTMEDPOSTEROMEDIAL ANKLE - Surgical Steps
Hook:POSTMED approach - protect the tibial nerve at every step!
Surgical Technique
Positioning Options
- Prone position: Excellent for isolated posterior malleolus or combined posterior approaches. Chest rolls, arms abducted less than 90 degrees, knee slightly flexed.
- Supine with external rotation: Leg externally rotated, knee flexed over a bolster. Allows combined anteromedial approach without repositioning. Preferred for most pilon cases.
Surface Landmarks
- Medial malleolus tip and anterior/posterior borders
- Posterior tibial artery pulse (palpable behind malleolus)
- Flexor hallucis longus tendon (palpable with great toe flexion)
- Medial border of Achilles tendon (posterior boundary)
- Incision placed 1 cm posterior to medial malleolus, extending proximally along medial tibia and distally toward navicular
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“A 42-year-old presents after a fall with a trimalleolar ankle fracture. CT shows a large posterior malleolar fragment involving 30 percent of the articular surface with 3 mm step-off. Describe your surgical approach.”
“During a posteromedial approach for a pilon fracture, you notice the patient has new numbness on the sole of the foot and weak toe flexion postoperatively. What is your assessment?”
“A 55-year-old with a complex pilon fracture has both anterolateral and posteromedial fragments. How do you plan your surgical approaches and positioning?”