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Techniques and Outcome in Pelvic Fractures

Corona Mortis

Incidence and Location

Tornetta, Paul; Hochwald, Neal; Levine, Richard

Editor(s): Tornetta, Paul

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Clinical Orthopaedics & Related Research: August 1996 - Volume 329 - Issue - p 97-101
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Abstract

The corona mortis is generally considered to be an arterial connection between the obturator and external iliac systems (Fig 1)5 Alternately, it may represent the origin of the obturator artery from the external iliac system. Estimates of an anomalous origin of the obturator artery range from 10% to 40%.1,4-6,8

Less information is available regarding the incidence and location of venous communications. In a recent study of acetabular fractures Cole and Bolhofner2 reported that communications between the external iliac and obturator systems were common.

This study determines the incidence and location of arterial and venous channels running over the superior ramus as they apply to surgery of the anterior pelvic ring.

MATERIALS AND METHODS

Fifty fresh cadaver sides were dissected. The dissection was done by making a Pfannenstiel type incision from the anterior superior iliac spine to the symphysis pubis. The superficial soft tissue anterior to the external oblique and rectus fascia were removed. Next, a vertical incision was made splitting the rectus muscles. The rectus was released from the symphyseal body and reflected laterally. The dissection proceeded laterally along the superior surface of the superior ramus from the insertion of the rectus toward the external iliac vessels. Attention was given to the soft tissues behind the symphyseal body and superior ramus to identify any vertically crossing vascular channels. Only vessels 2 mm in size or greater were preserved. All vessels were identified as arterial or venous and isolated (Figs 2, 3). The dissection was continued laterally until the sacroiliac joint was reached. After completion of the dissection and identification of all vessels, the distance of each was measured from the symphysis.

RESULTS

A vascular connection was identified in 42 (84%) cadaver sides. Seventeen (34%) had an arterial connection and 35 (70%) had a venous connection. Ten (59%) of the 17 arterial communications had an associated venous connection. Three (6%) had 2 arterial connections and 2 (4%) had 2 venous connections.

The distance from the symphysis to the vessels was 62 ± 12 mm. The range was 30 to 90 mm. The vessels were between 2 and 4 mm in diameter.

DISCUSSION

Variation in the origin of the obturator artery has been well described.1,4,5,8,9 Connections between the external iliac and obturator systems have been referred to as the corona mortis. Several acetabular surgeons have estimated its incidence as 10% to 15%.5,6 Yet, previous anatomic dissections have manifested a higher rate of anomalies of the obturator artery. Braithewaite1 found that the obturator artery came directly from the anterior division of the internal iliac artery in only 41% of 169 pelvic halves. Twenty-five percent originated from 1 of the gluteal arteries or trunk. An additional 20% came from the external iliac system and 6.5% had 2 origins (1 from the internal iliac system and 1 from the external iliac system). Braithewaite also found that only 23% had the same origin bilaterally.

In a similar study of 640 pelvic halves, Pick et al8 reported that 70% of the obturator arteries originated from the internal iliac system and 30% from the external iliac system. Most of the obturator arteries from the external system actually originated from the inferior epigastric artery.

It was first postulated that the obturator artery developed with 2 origins, 1 from each of the iliac systems. One of these became dominant.4,5 This was disputed by Jastschinski4,5 who studied the artery's origin in fetuses, children, and adults. He found the incidence of an anomalous origin to be 31%, 34%, and 24%, respectively.

The more commonly held belief is that the anastomoses between the external iliac system and the obturator artery represent large variations of the normal pelvic branches of the obturator and inferior epigastric arteries.8 These branches run on the inside of the superior ramus.

Although much attention has been given to the origin and variations of the obturator artery, little attention has been given to anomalies of the venous circulation in this region. Veins contribute to the bleeding in pelvic injuries, and in pelvic surgery.

This study was done to evaluate the incidence and location of vascular channels running over the superior pubic ramus as they apply to surgery of the anterior pelvic ring. Most surgeons approach the anterior pelvic ring through a Pfannenstiel incision and split the rectus. Alternately, the rectus can be released from its insertion surgically or might have been avulsed by the injury. In either case, the surgical exposure of the anterior ring involves lateral dissection on the superior pubic ramus. This dissection is carried laterally far enough to place fixation across the fracture.9

During this approach, vascular channels crossing the superior ramus in a vertical direction are at risk. It is irrelevant whether these vessels are anomalous arteries, veins, or simply anastomoses. If they are cut, they can lead to severe bleeding.3 Retraction of the vessel inferiorly or through the obturator foramen can make hemostasis very difficult. Additionally, if there is a simultaneous origin of the obturator artery, then the laceration of even a small caliber vessel can create a high flow arterial bleed via an extrapelvic anastomosis with the femoral circumflex vessel.8

To delineate the incidence and location of these vessels 50 cadaver halves were dissected from 25 cadavers. The data were reported as pelvic halves because of the low incidence of bilateral mirror image vascular trees found in earlier works.1 These dissections, which were carried out in a manner similar to the standard approach to the anterior ring, revealed vessels running vertically over and behind the superior ramus in 84% of the sides. The distance that the vessels were encountered as measured from the symphysis was 62 mm (range, 30-90 mm). These data correlate well with a recent report by Teague et al10 who found an incidence of 43% arterial and 59% venous channels in cadavers using the ilioinguinal approach.

The incidence of vertically directed vascular channels that are likely to be encountered during dissection along the superior ramus is higher than previously reported. Surgeons performing surgery on the anterior ring of the pelvis should be cautious to look for these vessels to avoid potentially serious bleeding.

Fig 1
Fig 1:
. Schematic drawing showing an arterial and a venous anastomosis between the external iliac and obturator systems. In this example, the connection originates from the inferior epigastric vessels and passes over the superior ramus.
Fig 2
Fig 2:
. Cadaveric dissection showing an arterial and a venous connection (arrows) passing over the superior ramus. For reference, the head is to the left and a Kirschner wire is in the symphysis.
Fig 3
Fig 3:
. Figure 2 has been inset to a line drawing of the bony pelvis to highlight its true position.

References

1. Braithewaite JL: Variations in origin of the parietal branches of the internal iliac artery. Am J Anat 86:423-430, 1952.
2. Cole J, Bolhofner B: Acetabular fracture fixation via a modified Stoppa limited intrapelvic approach. Clin Orthop 305:112-123, 1994.
3. Fernandez Llerena A: Hemorragia de la “corona mortis”. Pren Med Argent 55:382-385, 1968.
4. Jastschinski SN: Die Abweichungen der A. Obturotoria nebst Erklarung ihres Entstehens. Internationale Monatsschrift fur Anatomic und Physiologie. Bd. 8, S. 367-386, 1891.
5. Jastschinski SN: Die Abweichungen der A. obturotoria nebst Erklarung ihres Entstehens. Internationale Monatsschrift fur Anatomic Und Physiologie. Bd. 8, S. 417-446, 1891.
6. Letournel E, Judet R: Fractures of the Acetabulum. New York, Springer 1993.
7. Mayo K: Surgical approaches to the acetabulum. Tech Orthop 4:24-35, 1990.
    8. Pick JW, Anson BJ, Ashley FL: The origin of the obturator artery; study of 640 body halves. Am J Anat 70:317-343, 1942.
    9. Sappey MPC: Traite d'anatomic descriptive avec figures intercalees dans le texte, T.1. Delahaye, Paris 1853.
    10. Teague DC, Graney DO, Routt ML: Retropubic vascular hazards of the ilioinguinal exposure: A cadaveric and clinical study. Final Program Orthopedic Trauma Association, Los Angeles, CA 89, 1994.
    11. Tornetta III P, Matta JM: Internal fixation of unstable pelvic ring injuries. Orthop Trans 18:727, 1994.

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