Anatomy, Abdomen and Pelvis, Conjoint Tendon (Inguinal Aponeurotic Falx)

Four walls create the inguinal canal, but the most pertinent portion is the posterior wall, as the conjoint tendon contributes most to this structure. The posterior wall forms from the transversalis fascia, conjoint tendon, and deep inguinal ring. The conjoint tendon derives from a common aponeurosis of the internal oblique and the transverse abdominalis muscles. Its insertion is into the crest of the pubis and pectineal line deep to the superficial inguinal ring medial to the crural fibers. On imaging, the resting conjoint tendon is more vertical than horizontal. The distal tendon can be seen posterior to the pyramidalis muscle, and the conjoint tendon is seen crossing the junction of the middle and outer third of the pubic crest.[6]

The conjoint tendon is a fusion of muscle that forms from the internal oblique tendon and the transverses abdominis tendon. In some occurrences, the tendons can be entirely separate.[7]

The surgical relevance of the conjoined tendon is anatomical consideration during inguinal hernia repair. Techniques such as McVay, Bassini, and Shouldice involve suturing through the conjoint tendon to repair the weakness of the inguinal canal floor. 

A weakness in the conjoint tendon causes a type of direct herniation known as Bugosa herniation or a Gill-Ogilvie hernia.[8] This herniation usually presents in young, athletic males with well-developed abdominal muscles. Laparoscopic repair is performed to address the risk of hernia strangulation.

Hernias to the conjoint tendon are common in athletes, commonly known as a sports hernia[9]. The conjoint tendon physiologically supports the abdominal contents when increased intraabdominal stress occurs. The current hypothesis on the mechanism of injury is the "shutter effect," where the aponeurosis of the transversus abdominis muscle tenses with increased abdominal pressure. The imbalance of strong hip adductor muscles and the weaker lower abdominal muscles leads to a shearing force across the hemipelvis that can result in tearing of the transversalis fascia/anterior muscles.

Approximately 90% of sports hernias occur in men. The most common patient populations are athletes involved in activities such as running, kicking, sharp turns, changes in direction, or rapid acceleration and deceleration. Football, soccer, and hockey athletes are the most common. The primary symptom is groin pain with exercise. The pain is located on the lower rectus abdominis muscle and may extend to the suprapubic region. It may be subtle in the beginning but can present as a sudden aggravating pain in rare instances. The pain will usually appear the next day following the injury, with a feeling of hardness in the groin and difficulty rising from the bed. The pain wanes with rest and restarts immediately following intensive exercise. Sports hernias can be hard to differentiate from other processes with symptoms of chronic inguinal pain[10]. Rotation control and pelvic stability are two of the most critical factors in preventing injury. Those with previous abdominal and inguinal injuries are at a higher risk for reoccurrence. 

The diagnosis of a sports hernia is mainly a clinical one. Imaging can be beneficial with an MRI or ultrasound. Patients will often experience severe aching, pain after activity, and upon exertion such as defecation or cough.[11] The patient will report increased pain with palpation of the inguinal area, and a Valsalva maneuver can elicit a bulge. The current recommendation for conservative care is for 6 to 8 weeks of rest. Corticosteroids and working with a physical therapist may also be beneficial in recovery. If the condition does not improve with conservative measures, laparoscopic repair has been shown to improve symptoms and pain relief. 

The terminology of the conjoint tendon is often confusing and has multiple names. The terms conjoint (sometimes spelled conjoined) tendon, Henle's ligament, and falx inguinalis are sometimes referred to interchangeably.