The clinical anatomy of the musculotendinous part of the diaphragm.

The thoracoabdominal diaphragm is a composite musculotendinous structure, separating the thoracic and abdominal cavities. Reemphasis of the already well-delineated variations of the muscular and tendinous portions, and blood and nerve supply of the diaphragm is becoming apparent. Scientific reports concerning reconstruction of the pericardium, activation of the muscle and the phrenic nerves by use of laparoscopically placed intramuscular electrodes, and repair of congenital and traumatic hernias reemphasize the importance of the muscular to tendinous relationships. The objective of this study, therefore, was to measure the ratio of the surface area of the tendinous central region to the muscular region of the diaphragm and provide a clear description across various specimens. We classified diaphragmatic measurements from 104 adult human diaphragms into six classes (I-VI) based on the ratio of surface area between its tendinous and muscular components. The majority of specimens, 56.7%, was attributed to class II and indicated a tendon-to-muscle ratio of between 10 and 15%; however, a small number of specimens indicated a very large tendon area at the expense of muscle bulk. Future research should be geared toward assessing the relationship between surface area of the musculature and its motor points with focus on interventions for herniation repair and recovery. Our results have shown that surgical interventions should be tailored to the individual, as diaphragm size may not necessarily predict tendon-to-muscle ratio.