Location and Formation
The hiatus is located in the lower-medial part of the thigh, at the border with the popliteal fossa. Superficially in this region, the semitendinosus (m. semitendinosus) and semimembranosus (m. semimembranosus) muscles pass by.
This structure is formed in the distal portion of the adductor magnus muscle (m. adductor magnus). The tendon of this muscle attaches along the entire length of the linea aspera and arches toward the adductor tubercle (tuberculum adductorium) on the medial epicondyle. A tendinous arch forms between the muscle fibers or between the tendon and the femur, which constitutes the inferior opening of the adductor canal.
Topography and Relationship to the Adductor Canal
The adductor hiatus is an integral part of the adductor canal (canalis adductorius, Hunter's canal), serving as its distal exit. The canal itself is bounded by the following structures:
- Lateral wall — vastus medialis muscle (m. vastus medialis).
- Medial and posterior walls — adductor longus and adductor magnus muscles (m. adductor longus et m. adductor magnus).
- Roof — sartorius muscle (m. sartorius).
Proximally, the canal communicates with the femoral triangle space (trigonum femorale), and distally — via the hiatus adductorius — it opens into the popliteal fossa.
Structures Passing Through the Adductor Hiatus
The femoral vessels pass through the hiatus adductorius as they leave the adductor canal and head toward the popliteal fossa (fossa poplitea).
- Femoral artery (a. femoralis) — upon passing through the hiatus, it changes its name and continues as the popliteal artery (a. poplitea). At the exit from the canal, the artery lies deeper and more medially, closer to the bone. While directly within the hiatus adductorius, the femoral artery contributes to the collateral circulation network around the knee joint.
- Femoral vein (v. femoralis) — upon exiting the canal into the popliteal fossa, it lies more superficially and laterally relative to the artery.
Note: The saphenous nerve (n. saphenus) and descending genicular vessels (a. et v. descendens genus) do not pass through this hiatus. They leave the canal through a separate anterior opening in the vasto-adductor intermuscular septum (septum intermusculare vastoadductoria), entering the subcutaneous tissue beneath the sartorius muscle.
Clinical Significance
The adductor hiatus is the natural distal communication of the adductor canal with the popliteal fossa. The adductor canal also communicates proximally with the space of the femoral triangle.