Upper limb flexor retinaculum (wrist)
In the upper limb, the retinaculum mm. flexorum is a distal derivative of the forearm fascia (fascia antebrachii). This fascia forms a dense "cuff" around the forearm and, in the area of the radiocarpal joint, forms the palmar flexor retinaculum, also called the transverse carpal ligament.
- Function: The retinaculum forms the roof of the carpal tunnel.
- Canal contents: Running beneath the retinaculum are the tendons of the flexor digitorum superficialis and profundus (m. flexor digitorum superficialis et profundus), as well as the tendon of the flexor pollicis longus (m. flexor pollicis longus). These tendons are enclosed in synovial sheaths: the common flexor sheath and the radial bursa.
- Topography: In the proximal middle compartment of the palm and within the carpal tunnel, the flexor tendons lie tightly against the retinaculum and the palmar aponeurosis. Therefore, the subaponeurotic space of the palm generally has no direct connection with Pirogov-Parona space. The blind end of the radial synovial sheath lies 2 cm proximal to the retinaculum mm. flexorum, and the proximal end of the common flexor sheath lies 3–4 cm proximal to it.
Lower limb flexor retinaculum (ankle)
In the lower limb, the structure of the same name is located in the medial retromalleolar region (regio retromalleolaris medialis). It is a distal thickening of the dense leg fascia (fascia cruris), which forms intermuscular septa.
- Location: The ligament spans between the medial malleolus of the tibia (tibia) and the calcaneus.
- Function: It forms tarsal tunnels (canales tarsales) for the tendons of the tibialis posterior, flexor digitorum longus, and flexor hallucis longus muscles. Additionally, the retinaculum serves as one of the origin sites for the abductor hallucis muscle (m. abductor hallucis).
- Structures passing beneath it: Passing beneath the retinaculum are the synovial sheaths containing the tendons of the tibialis posterior (m. tibialis posterior), flexor digitorum longus (m. flexor digitorum longus), and flexor hallucis longus (m. flexor hallucis longus) muscles.
- Vessels and nerves: Accompanying the tendons is the neurovascular bundle, which includes the posterior tibial artery (a. tibialis posterior) and the tibial nerve (n. tibialis). In this area, calcaneal branches (rr. calcanei) arise from the tibial neurovascular bundle.
Clinical significance
Compression of the posterior tibial artery (a. tibialis posterior) posterior to the medial malleolus beneath the retinaculum mm. flexorum leads to tunnel syndrome.
Class and exam questions
Where is the Pirogov-Parona space located relative to the flexor retinaculum of the wrist?
The proximal blind ends of the synovial sheaths are located superior to the flexor retinaculum (retinaculum mm. flexorum): the radial bursa by 2 cm, and the common flexor sheath by 3–4 cm.
Does the subaponeurotic space of the palm communicate with the Pirogov-Parona space?
As a rule, there is no direct connection between them. This is because the flexor tendons in the proximal part of the middle palmar compartment and in the carpal tunnel lie closely against the flexor retinaculum and the palmar aponeurosis.
Which tendons pass beneath the flexor retinaculum in the foot?
Passing beneath the retinaculum are the tendons of the tibialis posterior, flexor digitorum longus, and flexor hallucis longus, each enclosed in its own synovial sheath.
What else to study on this topic
- The carpal tunnel and its contents
- Tarsal tunnel (canalis tarsalis)
- Pirogov-Parona fascial space
- Synovial sheaths of the hand
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