Downloaded from www.ajronline.org by 58.20.55.71 on 10/06/15 from IP address 58.20.55.71. Copyright ARRS. For personal use only; all rights reserved
271
CT Evidence for the “Osseous Pinch” Mechanism of Traumatic
Aortic
Alan
Jeffrey
M. Cohen1 R. Crass1
HolIis A. Thomas2 Richard G. Fisher3 David G. Jacobs4
Injury
OBJECTIVE. Our prior experiments induced by rapid deceleration results the anterior
suggested that traumatic laceration of the aorta from pinching of the aorta between the spine and (manubnum, clavicle, and first rib). This study examines that
bony complex
hypothesis
with in vivo CT data.
MATERIALS AND METHODS. In 22 patients with angiographically and surgically proved lacerations of the proximal descending aorta, chest CT scans were obtained before (18) or after (four) surgical repair. The point of impact of the anterior bony complex with the anterior surface of the thoracic spine during compression of the thorax was predicted by simulated rotation of the first rib based on calculations made from the CT scans. RESULTS. In all 22 patients, the projected site of impact of the anterior bony complex with the spine corresponded to the actual injured aortic segment as determined with angiography. CONCLUSION. Our data further support the proposed “osseous pinch” mechanism of injury to explain traumatic tears of the aorta. AJR
159:271-274,
August
1992
Previously proposed theories trauma were largely speculative
segments
(whiplash),
torsion
to explain the mechanism and included differential
forces,
hydrostatic
of aortic injury in blunt deceleration of aortic
forces, or various combinations
of
these mechanisms [1 -13]. Our prior series ofexperiments suggested that traumatic aortic lacerations could result from compression of the aorta between the anterior bony complex (manubrium, clavicle, and first rib) and the spine [14]. Compressive
forces present in blunt thoracic trauma depress the anterior thoracic osseous structures, causing them to rotate posteriorly and inferiorly about the posterior rib
Received November 18, revision February 25, 1992. 1
Department
of Radiology,
1991;
accepted
MetroHealth
after Medical
Center, Case Western Reserve University, 2500 MetroHealth Dr., Cleveland, OH 44109. Address reprint requests to A. M. Cohen. 2 of Diagnostic Radiology, Humana Hospital-University, Jackson
University
St., Louisville,
3Department 1502 Taub
Loop,
of Louisville,
Houston,
Ben Taub
0361 -803X/92/1 592-0271 © American Roentgen Ray Society
pinch” mechanism
Materials
and
CT scans Hospital,
accidents before
TX 77030.
Department of Surgery, MetroHealth Center, Case Western Reserve University, land, OH 44109.
“osseous
of traumatic
aortic injury.
Methods
530 5.
KY 40202.
of Radiology,
articulations. These forces could pinch and shear interposed vascular structures [14]. This article examines the cross-sectional anatomy from CT scans in patients with traumatic aortic lacerations to determine whether the theoretical point of impact between the anterior bony complex and the spine matches the actual site of aortic injury. It provides the first in vivo support for our hypothesis of the
Medical Cleve-
of 22 patients
form (n
preoperative
=
1 8)
the
data
or after
angiography,
admitted
set (n
for =
this
to our institutions
study.
4) surgery
which
documented
Each for
repair
patient
after high-speed had
a CT
of a traumatic
traumatic
laceration
scan
of the
motor chest
vehicle either
tear of the aorta. All had of the
aorta.
The CT scans in 21 patients were obtained with contiguous 1 -cm-thick sections from the thoracic inlet to below the carina; one patient had similar scans with 1-cm-thick sections at 1 .5-cm intervals. The locations and spatial relationships of the spine, ribs, sternum, and aorta found on the CT scans were recorded in a sagittal projection relative to the tabletop on graph
Downloaded from www.ajronline.org by 58.20.55.71 on 10/06/15 from IP address 58.20.55.71. Copyright ARRS. For personal use only; all rights reserved
272
COHEN
paper by using the following method: (1) each division along the xand y-axes of the linear graph paper represented 1 cm; (2) the table was assumed to keep a constant height in relation to the CT gantry so that it could serve as a point of zero reference for the y-axis; (3) scan slices were stacked along the x-axis at correct (1 .0 or 1 .5 cm) intervals; (4) each of the noted structures was measured from the tabletop by using the internal ruler present on the CT scan slice; (5) each structure was plotted on its visualized CT scan slice at the proper height on the y-axis of the graph paper. Compression of the thorax was simulated by a previously described method [1 4J: (1) the plotted costovertebral joints of the first rib defined the center point of all rotations; (2) the radius of rotation was defined by the distance from
the
center
point
to the
anterior
structure,
first
rib,
clavicle,
or
manubrium; (3) the motion of the anterior osseous structures relative to the aorta and anterior surface of the vertebral column was plotted around the axis of rotation by using the defined radius. Since the graph paper was linear and a properly scaled model was plotted on both axes, a compass or calipers could be used for this procedure (Fig.
1). This
allowed
analysis
of the osseous
aorta as well as study of the probable structures
on the
motion
segment
in relation
to the
of impact of those
aorta.
After the theoretical segment of impact was determined from the above calculation, that region was compared with the actual injured segment shown on the preoperative CT scans or with the segment of aorta replaced shown on the postoperative CT scans. By viewing the vascular anatomy and abnormalities present on each CT scan slice and correlating them with the angiographically defined site of aortic
injury,
we
were
able
to
localize
the
site
of vascular
injury
to
one or at most two contiguous scan slices in the 18 presurgery patients. On postoperative scans, tube grafts were visible for three to four
contiguous
scan
slices
so that
localization
was
less
ET AL.
AJR:159,
predicted rotation of cided within one scan aortic injury seen on dicted rotation of the within one scan slice
point
on the thoracic spine where maximal would cause the tip of the first rib, or manubrium to touch the spine. The points of from these structures on the spine had a sagittal of 3 cm or less in all instances. The point of impact
rotation
for the manubrium usually was on the same slice and at the same point as one of the other two structures. In 13 patients,
The region of aortic injury in the proximal descending aorta varied somewhat among 19 patients. In addition, three patients had relatively high lacerations of the aorta, one near the origin of the left carotid artery and two at the top of the
aortic arch (Fig. 3). The projected of the aorta
corresponded
and atypical
instances.
increased mediastinal toma. This ranged without mediastinal density with marked
support
16
0 14
anterior surface of spine
0
first rib origin
12
projected 10
I
I
1
2
3
4
5
6
CT slice (in cm)
A
B
pinch
hypothesis.
the point of aortic impingement
18
0
CT scans showed
density indicative of mediastinal hemafrom small periaortic density changes distortion to large regions of increased mediastinal contour changes.
for the osseous
0 .0
U)
All 18 preoperative
pinching
in the typical
In an earlier study [1 4], we demonstrated in a model that normal thoracic anatomy allows trapping of the aorta between the spine and anterior osseous structures when the thorax is
E
0 0 C 0
point of osseous
to the site of injury
Discussion
20
a E
had longer
We were
by using the
model previously described [1 4]. The theoretical contact point of the spine with the anterior osseous structures during maximal thoracic compression coincided with the injured aortic segment in each instance. The three cases with unusual sites of aortic laceration, which were accurately predicted with this model, further support the hypothesis and suggest that this mechanism may also account for great vessel injuries from blunt thoracic trauma [14]. Prior theories concerning the mechanism of vascular injury after blunt thoracic trauma never adequately explained these unusual, infrequent sites [1-13].
Analysis ofthe 22 CT scans ofthe thorax allowed prediction
(2 C
with tube grafts
compressed. Calculations made from the cross-sectional anatomy shown on CT scans in our current study provide
precise.
Results
clavicle, impact spread
patients
segments of CT localization. The entire rotated anterior bony complex struck the level of the tube graft in each instance. A typical case is shown in Figure 2.
able to calculate
rib or clavicle
1992
the first rib/manubrium complex coinslice, or 1 cm, with the actual site of imaging studies. In five patients, preclavicle/manubrium complex coincided with the imaged region of aortic injury.
The four postoperative
some
of the theoretical
August
aortic 7
8
tear 9
10
Fig. 1.-A, Line drawing (sagittal projection) of area of aortic injury analyzed in B shows relationship of aorta to anterior osseous complex and spine. Manubrium, clavicles, and anterior ends of first ribs, when compressed, describe similar arcs around an axis that originates at posterior articulations of first ribs. Arrows mdicate movement of anterior osseous complex that occurs with full compression. Site of expected aortic impingement is shown by asterisk. B, Graph of measurements obtained from set of CT sections of one patient. Measurements for each structure are from CT tabletop. Projected axis of rotation of anterior osseous complex with posterior first rib used as center of rotation is shown by dotted lines. Posterior first rib (open circle), anterior first rib (solid circle), clavicle (asterisk), and anterior surface of spine (triangles) are recorded. Solid arrow marks CT scan of section with actual aortic injury.
AJR:159,
August
1992
MECHANISM
OF AORTIC
INJURY
ON
CT
273
Fig. 2.-CT slices corresponding to sections defined in Fig. lB of patient whose CT scans
were used to create Fig. lB. A, CT scan of slice 2 located near thoracic inlet delineates location of posterior insertions for first ribs (arrows). Anterior surface of spine
Downloaded from www.ajronline.org by 58.20.55.71 on 10/06/15 from IP address 58.20.55.71. Copyright ARRS. For personal use only; all rights reserved
was measured
but is not marked.
B, CT scan of slice 5 shows location of articulations of anterior end of first rib (whlte arrow) and clavicle (solid black arrows) with manu-
brium. Manubrium was measured on next slice further cephalad (slice 4). Anterior surface of spine (open arrow). Increased density in mediastinum is indicative of blood. C, CT scan of slice 7 at level of aortic arch shows calculated location of impact to anterior osseous complex on anterior surface of spine (arrow). Mediastinum is dense, containing blood. D, Angiogram shows traumatic tear of aorta just distal to great vessels.
A
B
I U Fig. 3.-CT slices corresponding to sections similar to those graphically depicted in Fig. lB. A, CT scan of slice 4 shows posterior surface of manubrium (curved arrow), clavicles (straight solid arrows), and anterior surface of spine Generalized increased density in mediastinum is indicative of blood. Nearly round density to left of trachea may represent a pseudoaneurysm with aortic laceration. Projected slice of contact of anterior osseous complex with spine lies between this and next slice further caudad. B, CT scan of slice 5 shows aortic arch surrounded by blood. Projected point of impact is at this or next level further cephalad. C, Arteriogram shows a laceration and pseudoaneurysm at junction of aortic arch with left common carotid artery.
(open arrow). associated
COHEN
274
Our study indicates that the specific anterior bony structure causing vascular injury may vary. A combination of the manubrium and the clavicle or first rib best fits the geometry in most patients. Differences in patients’ anatomy, variations in
impact Downloaded from www.ajronline.org by 58.20.55.71 on 10/06/15 from IP address 58.20.55.71. Copyright ARRS. For personal use only; all rights reserved
suggest
force
vectors,
a degree
and the interaction
of variability
in where
of these the
factors
anterior
of the heart and great vessels of up to 8 cm during experimentally controlled thoracic trauma in dogs. Even in these animals and with the profound pectus carinatum of the spe-
cies, the anterior and posterior bones met. Therefore, our observed variation of osseous compression seems probable. The osseous pinch theory cannot readily be used to disprove older proposed theories explaining aortic lacerations [1 -1 2, 1 5, 16]. However, these theories also are unproved, having been created to fit the observed locations of vascular injury. The limitations inherent in previous models become
clear after several factors are considered. No experimental model exists to validate those proposed mechanisms of injury. Furthermore, although many currently existing theories suggest that the sudden, extreme mobility of the aorta is the
observations equivocally cause aortic
process responsible for the typical isthmic as to which aortic segment, the aortic arch aorta [9], is mobile on impact. Finally,
and statements contained in these articles unshow that the postulated forces are insufficient to tearing
[1,4,
5, 8, 9, 12]. In contrast,
vascular mechanism
study support
to explain
aortic
our proposed lacerations
osseous from
August
1992
REFERENCES 1 . Greendyke RM. Traumatic rupture of aorta. JAMA 1966;1 95:119-122 2. Klotz 0, Simpson W. Spontaneous rupture of the aorta. Am J Med Sci 1932;184:455-473 3. Kuhn LP. Traumatic rupture of thoracic aorta with review of fifty-five abdominal injuries. Ill Med J 1925;47:420-427 4. Lundevall J. The mechanism of traumatic rupture of the aorta. Acta Pathol Microbiol Scand 1964;62:34-46 5. Lundevall J. Traumatic rupture of the aorta with special reference to road accidents. Acta Pathol Microbiol Scand [A] 1964;62:29-33 6. Marsh CL, Moore AC. Deceleration trauma. Am J Surg 1957;93:623-631 7. Oldegard B, Wernan P0. Quoted by: Greendyke AM. Traumatic rupture 8.
9. 10. 11 . 1 2.
13.
14.
lesions.
Results of the current pinch
AJR:159,
the use of cadavers to test this theory [1 4], the current medicolegal climate has made that unfeasible. Instead, threedimensional computer modeling is being considered to provide an alternative method of studying the thorax and the deformities that could occur during blunt chest trauma.
the osseous
pinch theory is based on proven anatomic relationships. It even potentially explains why injuries caused by high-speed motor vehicle accidents, vehicles hitting pedestrians, falls from heights, and power tool kickback injuries can produce similar
AL.
and
posterior bones will contact. This has some experimental and logical basis. Jackson et al. [1 5] noted profound movement
primary pathologic tear, they disagree [1 2] or descending
ET
blunt
trauma. Without a human model, absolute proof of this or any theory is probably impossible. Although we had suggested
15. 16.
of
aorta. JAMA 1966;195:119-122 Oppenheim F. Quoted by: Parrnley LF, Mattingly TW, Manion WC, Jahnke EJ. Non-penetrating traumatic injury of the aorta. Circulation 1958;17:1086-1 101 Parmley LF, Mattingly TW, Manion WC, Jahnke EJ. Non-penetrating traumatic injury of the aorta. Circulation 1958;1 7:1086-1101 Stark P. Traumatic rupture of the thoracic aorta: review. CRC Crit Rev Diagn Imaging l984;21 :229-255 Strassman G. Traumatic rupture of the aorta. Am Heart J 1947;33: 508-515 Zehnder MA. Delayed post-traumatic rupture of the aorta in a young healthy individual after closed injury: mechanical-etiological considerations. Angiology l956;7:252-267 Fisher AG, Hadlock F, Ben-Menachern Y. Laceration of the thoracic aorta and brachiocephalic arteries by blunt trauma. Radio! Clin North Am 1981;19:91-1 10 Crass JA, Cohen AM, Motta AO, Tomashefski JF Jr, Wiesen EJ. A proposed new mechanism of traumatic aortic rupture: the osseous pinch. Radiology 1990;176:645-649 Jackson FR, Berkas EM, Roberts VL. Traumatic aortic rupture after blunt trauma. Dis Chest 1968;53:577-584 Haas GM. Types of internal injuries of personnel involved in aircraft accidents. J Aviation Med 1944;15:77-84
271
CT Evidence for the “Osseous Pinch” Mechanism of Traumatic
Aortic
Alan
Jeffrey
M. Cohen1 R. Crass1
HolIis A. Thomas2 Richard G. Fisher3 David G. Jacobs4
Injury
OBJECTIVE. Our prior experiments induced by rapid deceleration results the anterior
suggested that traumatic laceration of the aorta from pinching of the aorta between the spine and (manubnum, clavicle, and first rib). This study examines that
bony complex
hypothesis
with in vivo CT data.
MATERIALS AND METHODS. In 22 patients with angiographically and surgically proved lacerations of the proximal descending aorta, chest CT scans were obtained before (18) or after (four) surgical repair. The point of impact of the anterior bony complex with the anterior surface of the thoracic spine during compression of the thorax was predicted by simulated rotation of the first rib based on calculations made from the CT scans. RESULTS. In all 22 patients, the projected site of impact of the anterior bony complex with the spine corresponded to the actual injured aortic segment as determined with angiography. CONCLUSION. Our data further support the proposed “osseous pinch” mechanism of injury to explain traumatic tears of the aorta. AJR
159:271-274,
August
1992
Previously proposed theories trauma were largely speculative
segments
(whiplash),
torsion
to explain the mechanism and included differential
forces,
hydrostatic
of aortic injury in blunt deceleration of aortic
forces, or various combinations
of
these mechanisms [1 -13]. Our prior series ofexperiments suggested that traumatic aortic lacerations could result from compression of the aorta between the anterior bony complex (manubrium, clavicle, and first rib) and the spine [14]. Compressive
forces present in blunt thoracic trauma depress the anterior thoracic osseous structures, causing them to rotate posteriorly and inferiorly about the posterior rib
Received November 18, revision February 25, 1992. 1
Department
of Radiology,
1991;
accepted
MetroHealth
after Medical
Center, Case Western Reserve University, 2500 MetroHealth Dr., Cleveland, OH 44109. Address reprint requests to A. M. Cohen. 2 of Diagnostic Radiology, Humana Hospital-University, Jackson
University
St., Louisville,
3Department 1502 Taub
Loop,
of Louisville,
Houston,
Ben Taub
0361 -803X/92/1 592-0271 © American Roentgen Ray Society
pinch” mechanism
Materials
and
CT scans Hospital,
accidents before
TX 77030.
Department of Surgery, MetroHealth Center, Case Western Reserve University, land, OH 44109.
“osseous
of traumatic
aortic injury.
Methods
530 5.
KY 40202.
of Radiology,
articulations. These forces could pinch and shear interposed vascular structures [14]. This article examines the cross-sectional anatomy from CT scans in patients with traumatic aortic lacerations to determine whether the theoretical point of impact between the anterior bony complex and the spine matches the actual site of aortic injury. It provides the first in vivo support for our hypothesis of the
Medical Cleve-
of 22 patients
form (n
preoperative
=
1 8)
the
data
or after
angiography,
admitted
set (n
for =
this
to our institutions
study.
4) surgery
which
documented
Each for
repair
patient
after high-speed had
a CT
of a traumatic
traumatic
laceration
scan
of the
motor chest
vehicle either
tear of the aorta. All had of the
aorta.
The CT scans in 21 patients were obtained with contiguous 1 -cm-thick sections from the thoracic inlet to below the carina; one patient had similar scans with 1-cm-thick sections at 1 .5-cm intervals. The locations and spatial relationships of the spine, ribs, sternum, and aorta found on the CT scans were recorded in a sagittal projection relative to the tabletop on graph
Downloaded from www.ajronline.org by 58.20.55.71 on 10/06/15 from IP address 58.20.55.71. Copyright ARRS. For personal use only; all rights reserved
272
COHEN
paper by using the following method: (1) each division along the xand y-axes of the linear graph paper represented 1 cm; (2) the table was assumed to keep a constant height in relation to the CT gantry so that it could serve as a point of zero reference for the y-axis; (3) scan slices were stacked along the x-axis at correct (1 .0 or 1 .5 cm) intervals; (4) each of the noted structures was measured from the tabletop by using the internal ruler present on the CT scan slice; (5) each structure was plotted on its visualized CT scan slice at the proper height on the y-axis of the graph paper. Compression of the thorax was simulated by a previously described method [1 4J: (1) the plotted costovertebral joints of the first rib defined the center point of all rotations; (2) the radius of rotation was defined by the distance from
the
center
point
to the
anterior
structure,
first
rib,
clavicle,
or
manubrium; (3) the motion of the anterior osseous structures relative to the aorta and anterior surface of the vertebral column was plotted around the axis of rotation by using the defined radius. Since the graph paper was linear and a properly scaled model was plotted on both axes, a compass or calipers could be used for this procedure (Fig.
1). This
allowed
analysis
of the osseous
aorta as well as study of the probable structures
on the
motion
segment
in relation
to the
of impact of those
aorta.
After the theoretical segment of impact was determined from the above calculation, that region was compared with the actual injured segment shown on the preoperative CT scans or with the segment of aorta replaced shown on the postoperative CT scans. By viewing the vascular anatomy and abnormalities present on each CT scan slice and correlating them with the angiographically defined site of aortic
injury,
we
were
able
to
localize
the
site
of vascular
injury
to
one or at most two contiguous scan slices in the 18 presurgery patients. On postoperative scans, tube grafts were visible for three to four
contiguous
scan
slices
so that
localization
was
less
ET AL.
AJR:159,
predicted rotation of cided within one scan aortic injury seen on dicted rotation of the within one scan slice
point
on the thoracic spine where maximal would cause the tip of the first rib, or manubrium to touch the spine. The points of from these structures on the spine had a sagittal of 3 cm or less in all instances. The point of impact
rotation
for the manubrium usually was on the same slice and at the same point as one of the other two structures. In 13 patients,
The region of aortic injury in the proximal descending aorta varied somewhat among 19 patients. In addition, three patients had relatively high lacerations of the aorta, one near the origin of the left carotid artery and two at the top of the
aortic arch (Fig. 3). The projected of the aorta
corresponded
and atypical
instances.
increased mediastinal toma. This ranged without mediastinal density with marked
support
16
0 14
anterior surface of spine
0
first rib origin
12
projected 10
I
I
1
2
3
4
5
6
CT slice (in cm)
A
B
pinch
hypothesis.
the point of aortic impingement
18
0
CT scans showed
density indicative of mediastinal hemafrom small periaortic density changes distortion to large regions of increased mediastinal contour changes.
for the osseous
0 .0
U)
All 18 preoperative
pinching
in the typical
In an earlier study [1 4], we demonstrated in a model that normal thoracic anatomy allows trapping of the aorta between the spine and anterior osseous structures when the thorax is
E
0 0 C 0
point of osseous
to the site of injury
Discussion
20
a E
had longer
We were
by using the
model previously described [1 4]. The theoretical contact point of the spine with the anterior osseous structures during maximal thoracic compression coincided with the injured aortic segment in each instance. The three cases with unusual sites of aortic laceration, which were accurately predicted with this model, further support the hypothesis and suggest that this mechanism may also account for great vessel injuries from blunt thoracic trauma [14]. Prior theories concerning the mechanism of vascular injury after blunt thoracic trauma never adequately explained these unusual, infrequent sites [1-13].
Analysis ofthe 22 CT scans ofthe thorax allowed prediction
(2 C
with tube grafts
compressed. Calculations made from the cross-sectional anatomy shown on CT scans in our current study provide
precise.
Results
clavicle, impact spread
patients
segments of CT localization. The entire rotated anterior bony complex struck the level of the tube graft in each instance. A typical case is shown in Figure 2.
able to calculate
rib or clavicle
1992
the first rib/manubrium complex coinslice, or 1 cm, with the actual site of imaging studies. In five patients, preclavicle/manubrium complex coincided with the imaged region of aortic injury.
The four postoperative
some
of the theoretical
August
aortic 7
8
tear 9
10
Fig. 1.-A, Line drawing (sagittal projection) of area of aortic injury analyzed in B shows relationship of aorta to anterior osseous complex and spine. Manubrium, clavicles, and anterior ends of first ribs, when compressed, describe similar arcs around an axis that originates at posterior articulations of first ribs. Arrows mdicate movement of anterior osseous complex that occurs with full compression. Site of expected aortic impingement is shown by asterisk. B, Graph of measurements obtained from set of CT sections of one patient. Measurements for each structure are from CT tabletop. Projected axis of rotation of anterior osseous complex with posterior first rib used as center of rotation is shown by dotted lines. Posterior first rib (open circle), anterior first rib (solid circle), clavicle (asterisk), and anterior surface of spine (triangles) are recorded. Solid arrow marks CT scan of section with actual aortic injury.
AJR:159,
August
1992
MECHANISM
OF AORTIC
INJURY
ON
CT
273
Fig. 2.-CT slices corresponding to sections defined in Fig. lB of patient whose CT scans
were used to create Fig. lB. A, CT scan of slice 2 located near thoracic inlet delineates location of posterior insertions for first ribs (arrows). Anterior surface of spine
Downloaded from www.ajronline.org by 58.20.55.71 on 10/06/15 from IP address 58.20.55.71. Copyright ARRS. For personal use only; all rights reserved
was measured
but is not marked.
B, CT scan of slice 5 shows location of articulations of anterior end of first rib (whlte arrow) and clavicle (solid black arrows) with manu-
brium. Manubrium was measured on next slice further cephalad (slice 4). Anterior surface of spine (open arrow). Increased density in mediastinum is indicative of blood. C, CT scan of slice 7 at level of aortic arch shows calculated location of impact to anterior osseous complex on anterior surface of spine (arrow). Mediastinum is dense, containing blood. D, Angiogram shows traumatic tear of aorta just distal to great vessels.
A
B
I U Fig. 3.-CT slices corresponding to sections similar to those graphically depicted in Fig. lB. A, CT scan of slice 4 shows posterior surface of manubrium (curved arrow), clavicles (straight solid arrows), and anterior surface of spine Generalized increased density in mediastinum is indicative of blood. Nearly round density to left of trachea may represent a pseudoaneurysm with aortic laceration. Projected slice of contact of anterior osseous complex with spine lies between this and next slice further caudad. B, CT scan of slice 5 shows aortic arch surrounded by blood. Projected point of impact is at this or next level further cephalad. C, Arteriogram shows a laceration and pseudoaneurysm at junction of aortic arch with left common carotid artery.
(open arrow). associated
COHEN
274
Our study indicates that the specific anterior bony structure causing vascular injury may vary. A combination of the manubrium and the clavicle or first rib best fits the geometry in most patients. Differences in patients’ anatomy, variations in
impact Downloaded from www.ajronline.org by 58.20.55.71 on 10/06/15 from IP address 58.20.55.71. Copyright ARRS. For personal use only; all rights reserved
suggest
force
vectors,
a degree
and the interaction
of variability
in where
of these the
factors
anterior
of the heart and great vessels of up to 8 cm during experimentally controlled thoracic trauma in dogs. Even in these animals and with the profound pectus carinatum of the spe-
cies, the anterior and posterior bones met. Therefore, our observed variation of osseous compression seems probable. The osseous pinch theory cannot readily be used to disprove older proposed theories explaining aortic lacerations [1 -1 2, 1 5, 16]. However, these theories also are unproved, having been created to fit the observed locations of vascular injury. The limitations inherent in previous models become
clear after several factors are considered. No experimental model exists to validate those proposed mechanisms of injury. Furthermore, although many currently existing theories suggest that the sudden, extreme mobility of the aorta is the
observations equivocally cause aortic
process responsible for the typical isthmic as to which aortic segment, the aortic arch aorta [9], is mobile on impact. Finally,
and statements contained in these articles unshow that the postulated forces are insufficient to tearing
[1,4,
5, 8, 9, 12]. In contrast,
vascular mechanism
study support
to explain
aortic
our proposed lacerations
osseous from
August
1992
REFERENCES 1 . Greendyke RM. Traumatic rupture of aorta. JAMA 1966;1 95:119-122 2. Klotz 0, Simpson W. Spontaneous rupture of the aorta. Am J Med Sci 1932;184:455-473 3. Kuhn LP. Traumatic rupture of thoracic aorta with review of fifty-five abdominal injuries. Ill Med J 1925;47:420-427 4. Lundevall J. The mechanism of traumatic rupture of the aorta. Acta Pathol Microbiol Scand 1964;62:34-46 5. Lundevall J. Traumatic rupture of the aorta with special reference to road accidents. Acta Pathol Microbiol Scand [A] 1964;62:29-33 6. Marsh CL, Moore AC. Deceleration trauma. Am J Surg 1957;93:623-631 7. Oldegard B, Wernan P0. Quoted by: Greendyke AM. Traumatic rupture 8.
9. 10. 11 . 1 2.
13.
14.
lesions.
Results of the current pinch
AJR:159,
the use of cadavers to test this theory [1 4], the current medicolegal climate has made that unfeasible. Instead, threedimensional computer modeling is being considered to provide an alternative method of studying the thorax and the deformities that could occur during blunt chest trauma.
the osseous
pinch theory is based on proven anatomic relationships. It even potentially explains why injuries caused by high-speed motor vehicle accidents, vehicles hitting pedestrians, falls from heights, and power tool kickback injuries can produce similar
AL.
and
posterior bones will contact. This has some experimental and logical basis. Jackson et al. [1 5] noted profound movement
primary pathologic tear, they disagree [1 2] or descending
ET
blunt
trauma. Without a human model, absolute proof of this or any theory is probably impossible. Although we had suggested
15. 16.
of
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