Retromalleolar regions (med.+ lat.)
### Topographic Anatomy of the Retromalleolar Regions (Medial and Lateral)
The *retromalleolar regions* refer to the anatomical spaces located posterior to the *medial* and *lateral malleoli* of the ankle. These regions are clinically significant as they contain important tendons, nerves, and blood vessels that pass from the leg to the foot.
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### *1. Medial Retromalleolar Region*
The *medial retromalleolar region* lies posterior to the *medial malleolus* of the tibia and serves as a passage for several structures going to the plantar aspect of the foot.
#### *Borders*:
- *Anterior*: Posterior aspect of the medial malleolus.
- *Posterior*: Calcaneus.
- *Superior*: Lower end of the tibia.
- *Inferior*: Continuous with the plantar aspect of the foot.
#### *Contents* (Tom, Dick And Very Nervous Harry mnemonic):
1. *T*ibialis posterior tendon:
- The most anterior structure, responsible for inversion and plantar flexion of the foot.
2. *Flexor **D*igitorum longus tendon:
- Runs just posterior to the tibialis posterior tendon, flexes the lateral four toes.
3. *Posterior tibial Artery*:
- Located posterior to the flexor digitorum longus tendon and gives off the medial and lateral plantar arteries as it enters the foot.
4. *Posterior tibial Vein*:
- Accompanies the posterior tibial artery.
5. *Tibial Nerve*:
- Positioned between the artery and the flexor hallucis longus tendon, it provides motor and sensory innervation to the foot.
6. *Flexor Hallucis Longus tendon*:
- The most posterior tendon in this region, it flexes the great toe and assists with plantar flexion of the foot.
#### *Clinical Relevance*:
1. *Tarsal Tunnel Syndrome*:
- This condition occurs when the *tibial nerve* is compressed within the tarsal tunnel (medial retromalleolar region), leading to pain, numbness, and tingling in the plantar aspect of the foot.
2. *Posterior Tibial Pulse*:
- The posterior tibial artery can be palpated posterior to the medial malleolus, a key site for checking vascular supply to the foot.
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### *2. Lateral Retromalleolar Region*
The *lateral retromalleolar region* lies posterior to the *lateral malleolus* of the fibula. This region allows tendons of the peroneal muscles to pass from the leg to the foot.
#### *Borders*:
- *Anterior*: Posterior aspect of the lateral malleolus.
- *Posterior*: Calcaneus.
- *Superior*: Lower end of the fibula.
- *Inferior*: Continuous with the lateral aspect of the foot.
#### *Contents*:
1. *Peroneus Longus Tendon*:
- The more superficial tendon of the lateral retromalleolar region, it crosses the lateral side of the ankle and inserts into the base of the first metatarsal and medial cuneiform. It functions to *evert* and *plantar flex* the foot.
2. *Peroneus Brevis Tendon*:
- Located just anterior to the peroneus longus tendon, it inserts into the base of the fifth metatarsal. Its function is *eversion* of the foot.
#### *Clinical Relevance*:
1. *Peroneal Tendonitis*:
- Inflammation of the peroneal tendons due to overuse or trauma can cause pain in the lateral ankle, often seen in athletes and runners.
2. *Peroneal Tendon Subluxation*:
- A condition where the peroneal tendons dislocate from behind the lateral malleolus due to damage to the superior peroneal retinaculum, often caused by ankle sprains.
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### *Retinacula in the Retromalleolar Regions*
Both the medial and lateral retromalleolar regions are stabilized by *retinacula*, which are thickened bands of deep fascia that hold tendons in place as they pass around the ankle.
- *Flexor Retinaculum (Medial)*: Holds the tendons of the tibialis posterior, flexor digitorum longus, and flexor hallucis longus in place, forming the roof of the tarsal tunnel.
- *Superior and Inferior Peroneal Retinacula (Lateral)*: Secure the peroneus longus and brevis tendons behind the lateral malleolus.