"Triangle of pain"

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A Moment in History

Jean George Bachmann
(1877 – 1959)

French physician–physiologist whose experimental work in the early twentieth century provided the first clear functional description of a preferential interatrial conduction pathway. This structure, eponymically named “Bachmann’s bundle”, plays a central role in normal atrial activation and in the pathophysiology of interatrial block and atrial arrhythmias.

As a young man, Bachmann served as a merchant sailor, crossing the Atlantic multiple times. He emigrated to the United States in 1902 and earned his medical degree at the top of his class from Jefferson Medical College in Philadelphia in 1907. He stayed at this Medical College as a demonstrator and physiologist. In 1910, he joined Emory University in Atlanta. Between 1917 -1918 he served as a medical officer in the US Army. He retired from Emory in 1947 and continued his private medical practice until his death in 1959.

On the personal side, Bachmann was a man of many talents: a polyglot, he was fluent in German, French, Spanish and English. He was a chef in his own right and occasionally worked as a chef in international hotels. In fact, he paid his tuition at Jefferson Medical College, working both as a chef and as a language tutor.

The intrinsic cardiac conduction system was a major focus of cardiovascular research in the late nineteenth and early twentieth centuries. The atrioventricular (AV) node was discovered and described by Sunao Tawara and Karl Albert Aschoff in 1906, and the sinoatrial node by Arthur Keith and Martin Flack in 1907.

While the connections that distribute the electrical impulse from the AV node to the ventricles were known through the works of Wilhelm His Jr, in 1893 and Jan Evangelista Purkinje in 1839, the mechanism by which electrical impulses spread between the atria remained uncertain.

In 1916 Bachmann published a paper titled “The Inter-Auricular Time Interval” in the American Journal of Physiology. Bachmann measured activation times between the right and left atria and demonstrated that interruption of a distinct anterior interatrial muscular band resulted in delayed left atrial activation. He concluded that this band constituted the principal route for rapid interatrial conduction.

Subsequent anatomical and electrophysiological studies confirmed the importance of the structure described by Bachmann, which came to bear his name. Bachmann’s bundle is now recognized as a key determinant of atrial activation patterns, and its dysfunction is associated with interatrial block, atrial fibrillation, and abnormal P-wave morphology. His work remains foundational in both basic cardiac anatomy and clinical electrophysiology.

Sources and references
1. Bachmann G. “The inter-auricular time interval”. Am J Physiol. 1916;41:309–320.
2. Hurst JW. “Profiles in Cardiology: Jean George Bachmann (1877–1959)”. Clin Cardiol. 1987;10:185–187.
3. Lemery R, Guiraudon G, Veinot JP. “Anatomic description of Bachmann’s bundle and its relation to the atrial septum”. Am J Cardiol. 2003;91:148–152.
4. "Remembering the canonical discoverers of the core components of the mammalian cardiac conduction system: Keith and Flack, Aschoff and Tawara, His, and Purkinje" Icilio Cavero and Henry Holzgrefe Advances in Physiology Education 2022 46:4, 549-579.
5. Knol WG, de Vos CB, Crijns HJGM, et al. “The Bachmann bundle and interatrial conduction” Heart Rhythm. 2019;16:127–133.
6. “Iatrogenic biatrial flutter. The role of the Bachmann’s bundle” Constán E.; García F., Linde, A.. Complejo Hospitalario de Jaén, Jaén. Spain
7. Keith A, Flack M. The form and nature of the muscular connections between the primary divisions of the vertebrate heart. J Anat Physiol 41: 172–189, 1907.

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Image property of: CAA.Inc.. Artist: M. Zuptich.

The so-called "triangle of pain" is a misnomer coined by laparoscopic hernia surgeons who observed the anatomy of the inguinofemoral region from the posterior aspect and refers to an inverted "V" shaped area which should be avoided because of the potential to damage nerves when placing staples, tacks, or sutures to anchor a mesh during a laparoscopic herniorrhaphy.

An example of a similar situation with terminology is the so-called "triangle of doom". It is also not a triangle, as it only has two boundaries. similarly, it does indicate an area where it is dangerous to place staples or sutures during laparoscopic hernia surgery.

The "triangle of pain" is an inverted "V" shaped area with its apex at the internal (deep) inguinal ring. It is bound anteriorly by the iliopubic tract / inguinal ligament and by the testicular (spermatic) vessels posteromedially. This "triangle" has no defined posterolateral boundary. although you can see it in drawings by some authors.

The reason why this area should be avoided and not place staples or sutures to anchor a hernia mesh is that there are several nerves which usually cannot be seen as they run just deep to the endoabdominopelvic fascia.These nerves can suffer damage or entrapment when performing a laparoscopic herniorrhaphy and cause pain (hence the name of the area) as well as motor and sensory disorders.

The nerves are:

• Lateral femoral cutaneous nerve: arising from the ventral rami of L2 and L3, this nerve provides sensory innervation to the anterior skin of the thigh

• Femoral nerve: arising from the ventral rami of L2, L3, and L4, this nerves provides motor and sensory innervation to the anterior compartment of the thigh as well as sensory branches to the hip joint

• Genitofemoral nerve: arising from the ventral rami of L1 and L2, this nerve divides anterior to the psoas major muscle into two branches. The genital branch of the genitofemoral nerve enters the inguinal canal and provides sensory and motor innervation to the scrotum and cremaster muscle, as well as the labia majora and mons pubis. The femoral branch of the genitofemoral nerve enters the "triangle of pain" region and passes inferior to the inguinal ligament to provide sensory cutaneous innervation to the superior aspect of the thigh.

The image shows a posterior view of the inguinal region. The "triangle of pain" is depicted in yellow. The iliopubic tract / inguinal ligament is shown by a blue dotted line while the testicular vessels boundary is shown by a red dotted line. The blue arrow points to the aberrant obturator artery (Corona Mortis).

Thanks to Steve Pearson for suggesting this term. Medical illustration by Mark J. Zuptich.

Clinical anatomy of the inguinofemoral hernias, as well as abdominal and perineal hernias are some of the lecture topics developed and delivered to the medical devices industry by Clinical Anatomy Associates, Inc. For more information Contact Us.

"Triangle of pain"

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