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The [lacunar ligament] is a half-moon shaped ligament that extends between the inguinal ligament (Poupart's ligament) superiorly and the pectineal ligament (Cooper's ligament) inferiorly. The lacunar ligament is at its narrowest at the point where the inguinal ligament and the pectineal ligament meet at the pubic tubercle where all three ligaments insert. The lacunar ligament is the medial boundary of the femoral ring.
The lacunar ligament was first described in 1765 by Don Antonio de Gimbernat y Arbós (1734 - 1816), who also described the importance of this ligament in the reduction of a strangulated femoral hernia.
In the anterior (open) approach to a strangulated femoral hernia, there is very little space at the femoral ring to enlarge it and allow reduction of the hernia contents. What Gimbernat did was to carefully cut the ligament from lateral to medial, enlarging the femoral ring and allowing reduction of the hernia. This was against the technique practiced at the time, which was to cut trough the inguinal ligament.
One of concerns when using this technique is the presence of the Corona Mortis, an anatomical variation in the area. Since the Corona Mortis is found posterior to the lacunar ligament, it can be unknowingly transected when repairing a femoral hernia from the anterior aspect.