Keywords
anterior tibial artery - missile fragment - posterior tibial neuropathy
Introduction
Arterial injuries are common event in military and civilian practice with iatrogenic
one occurring in increasing frequency.[1]
[2]
[3]
[4]
If the initial injury, in particular in noncritical arteries, is left unrecognized
or is regarded insignificant to seek medical advice, a traumatic aneurysm might develop.[5]
[6]
[7]
[8]
[9]
[10]
[11]
Traumatic aneurysms are true when the arterial wall injury occurs in intimal and medial
layers of the artery with intact adventitia, and hence tend to be fusiform and their
expansion is limited. A pseudoaneurysm or false aneurysm develops when all three layers
of the artery are affected. In such circumstances, low-flow bleeding continues at
the site of injury and this will gradually result in the reaction of the surrounding
tissues with formation of a fibrous capsule around the hematoma.[7]
[8]
[9]
[10]
[11] This means that in a pseudoaneurysm, the hematoma freely communicates with the intravascular
space, so that it can be designated as pulsating hematoma. For this reason, pseudoaneurysms
are more likely to expand. With considerable expansion, adjacent structures and in
particular the nearest traversing peripheral nerve might be compressed resulting in
progressive neuropathy.[12]
[13]
The leg arterial network is composed of three arteries: posterior tibial, peroneal,
and anterior tibial. Anterior tibial artery is a nonvital artery of the leg with a
short, but deeply located proximal and a long superficially located distal segment.
Anterior tibial artery injury is one of the least among the arterial injuries of the
extremities and account for approximately 2%, both in civilian and military experience.[1]
[5]
[6]
[8] Nonetheless, according to these cases series, vulnerability of the distal segment
of this artery to trauma compared with its proximal segment becomes apparent.[14]
On the contrary, formation of an arterial pseudoaneurysm due to missile fragment in
the lower extremities and in particular in the leg is a well-known pathology in military
practice. Reviewing the military experience since World War II, we found that traumatic
aneurysms of anterior tibial artery account from 0 to approximately 2% of all traumatic
aneurysms of the extremities with antipersonnel mines standing at the top.[1]
[5]
[6]
[8]
[15]
Survey of civilian experience yielded the same result regarding the incidence.[4]
[11]
[15]
[16]
[17]
[18]
[19]
[20]
[21] In civilian communities, traumatic pseudoaneurysm of the anterior tibial artery
is secondary to tibial or fibula shaft fractures, stab wounds, or low-velocity bullet
injuries.[3]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
Recently, iatrogenic pseudoaneurysms of this artery due to orthopedic procedures are
reported in increasing frequency.[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
In careful review of the literature, we found that the injury of the proximal segment
of the anterior tibial artery has been reported only in one rare occasion, where not
a single case of pseudoaneurysm originating from this segment has been reported.[14] This means that all published pseudoaneurysms of this artery have been confined
to the distal segment.
In this article, we present the first example of a pseudoaneurysm of the proximal
segment of the anterior tibial artery with compressive posterior tibial neuropathy
which was diagnosed 12 years after being injured by a small missile fragment. This
pathology was managed by exclusion of the pseudoaneurysm after ligation of the artery
proximal and distal to the aneurysmal sac and subsequent neurolysis of the posterior
tibial nerve.
Furthermore, where the usual delay in the diagnosis of the posttraumatic pseudoaneurysms
of the extremities may range from a few days to several weeks with a mean of 45 days,
onset of the pathology after such a long delay following a penetrating injury makes
this case more interesting.[33]
[34]
[35]
[36]
[37]
Case Report
This 38-year-old military man was referred for the evaluation of radicular pain over
the posterior aspect of his right leg and numbness at the planter aspect of his right
foot for 3 weeks of duration. The patient had a history of being injured by several
missile fragments 11 years before admission. With probable diagnosis of S1 root radiculopathy
from L5–S1 disc herniation, lumbar myelography in another institution was normal.
With continuing discomfort, he was referred to our institution.
His neurological exam revealed distal sciatica at the course of S1 root, with hypoesthesia
of the right sole. Further examination and palpation revealed a painful and pulsatile
mass in the popliteal region. A bruit was heard in auscultation. With the diagnosis
of a pseudoaneurysm, selective angiography was done and this revealed a pseudoaneurysm
arising from the proximal segment of the anterior tibial artery. The artery bowed
because of the compressive effect of the pseudoaneurysms ([Fig.1]). With consideration of the existence of difference between the size of the aneurysm
in angiography and the size of the mass in palpation, contrasted CT scan was done
to estimate the exact size of the aneurysm. This showed a large isointense mass with
rim enhancement surrounding a hyperdense area. The rim was compatible with the pseudocapsule
of the aneurysm and the isointense mass was an old clot where hyperdense area was
the patent part of the aneurysm ([Fig. 2]).
Fig. 1 (A, B) 0, AP and lateral femoral artery angiography show the pseudoaneurysm arising from
proximal anterior tibial artery in popliteal region (black arrow head).The tibioperoneal
trunk is patent (white arrow head). The posterior tibial artery (black arrow) is demonstrated
where peroneal artery (white arrow seems to be narrow probably because of the compressive
effect of the pseudoaneurysm. A small missile fragment is demonstrated in both views
(short black arrows).
Fig. 2 Contrasted CT scan showing the actual size of the aneurysm with its pseudocapsule
being presented as rim enhancement. The patent part of the aneurysm is demonstrated
as a hyperdense mass compatible with fresh blood which is surrounded by isodense area
compatible with old clot. An artifact may be due to the missile fragment hidden behind
the bone.
Intervention
The popliteal fossa was approached through a loose S-shape posterolateral incision. The popliteal, tibiofibular trunk and the proximal
part of anterior tibial artery were identified and exposed. The proximal anterior
tibial artery was ligated. Then the aneurysmal sac with dense fibrous wall was incised.
Large quantities of old and fresh bloods were evacuated. Then, the orifice of the
artery distal to the aneurysm was identified through its faint retrograde bleeding
and this was sutured and occluded. Subsequently, the aneurysmal sac was dissected
from surrounding structures including the flattened discolored posterior tibial nerve
and was totally removed, and the affected nerve was released separately from the adhesions
using magnification. Postoperative course was uneventful. At 2-month follow-up, he
was neurologically normal.
Discussion
Anterior tibial artery injury is one of the three arteries of the leg which has a
deep proximal segment and superficial distal segment. Vulnerability of this artery
to trauma differs in these two segments. For better understanding of this difference,
review of its anatomy is necessary. This artery is the first branch of the popliteal
artery which after traversing a few centimeters in the popliteal fossa pierces the
interosseous membrane and descends into the anterior compartment of the leg along
the shin in close proximity to peroneal nerve. The popliteal artery, currently being
called tibiofibular trunk, divides into two branches, posterior tibial and peroneal
arteries. Expectedly, the superficial and unprotected distal segment of the anterior
tibial artery allows access for wounds not strong enough to be able to traumatize
the short proximal segment embedded deeply in a rather more protected location. Even
among the arteries of the popliteal region, the distal anterior tibial artery is the
least susceptible.[14]
With arterial injury left unrecognized, a pseudoaneurysm might develop. Especially
if the initial trauma is regarded too insignificant to seek medical advice.[5]
[6]
[7]
[8]
[9]
[10]
[11] The pathogenesis of a pseudoaneurysm is characterized by a disruption of the arterial
continuity with extravasation of blood into the surrounding tissues.[5]
[6]
[7]
[8]
[9]
[10]
[11] This leads to the formation of a fibrous sac that progressively enlarges due to
the arterial pressure.[5]
[6]
[7]
[8]
[9]
[10]
[11]
With more susceptibility of the distal segment of this artery, the pseudoaneurysms
of this part of anterior tibial artery are reported in increasing frequency. In the
past only missile wounds, low-velocity bullet injuries, penetrating injuries such
as stab wounds, and tibia-fibula closed fractures had been the major causes of the
pseudoaneurysms formation.[5]
[6]
[7]
[8]
[9]
[10]
[11]
[16]
[17]
[18]
[19]
[20]
[21] Nowadays, with the development of technology, iatrogenic etiology is the most frequent
cause of this pathology, including percutaneous osteotomy, fixators, tibial nailing,
locking plate, arthroscopy, meniscectomy, and knee and ankle arhtroplasty.[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
Before surveying the literature, with respect to the rarity of the distal segment
arterial injury, a traumatic pseudoaneurysm developing at this site was expected to
be an extremely rare event. Therefore, we were not surprised that not a single case
of such pathology could be found in careful review.
The timeframe for the development or detection of a pseudoaneurysm after a trauma
is quite variable and ranges from a few days to a few months or even years. In our
case, the depth of the affected artery and the size of the missile fragment may explain
the rather slow process and the unusual delay in diagnosis.
Pseudoaneurysm detection several years after injury has been reported only in six
occasions including our case.[33]
[34]
[35]
[36]
[37] Surprisingly, three of these cases have followed trivial missile fragment injuries,
one with gunshot wound 12 years earlier, one with history of stab wound, and the last
one because of a nail puncture.[33]
[34]
[35]
[36]
[37]
Usually, a peripheral nerve accompanies the arteries of the extremities and with formation
of an aneurysm, vascular compressive neuropathy might appear.[12]
[13] The distal segment of the anterior tibial artery is in close proximity to the peroneal
nerve and with sufficient enlargement of the corresponding aneurysm, peroneal nerve
neuropathy might occur.[38]
However, compressive neuropathy due to a pseudoaneurysm of proximal segment is unlikely
because of its far distance from the nearest nerve, which is posterior tibial nerve.
Reasonably, if posterior tibial compressive neuropathy coinciding a traumatic aneurysm
of the proximal anterior tibial artery occurs, it should be an exception and only
occur when the corresponding pseudoaneurysm reach to a giant size.
Historically, surgical strategy for pseudoaneurysm of less vital arteries had been
ligation of the artery proximal and distal to the aneurysm followed by aneurysmal
sac excision.[6]
[10] This remained the gold standard strategy for anterior tibial artery pseudoaneurysms.
Actually, with classification of the anterior tibial artery as a nonvital artery,
resection and re-establishment of continuity of this artery is regarded unnecessary.[20] However, preservation of the patency of the anterior tibial artery via autogenous
vein graft is necessary only when the posterior tibial artery has been already occluded.
With improvements in medical technology, treatment options for pseudoaneurysms of
the peripheral arteries have evolved to less invasive methods.[27]
[39]
[40]
[41]
[42]
[43]
[44] Advantages of these techniques are the ability to reach locations that would otherwise
require extensive open surgical exploration. Furthermore, it allows rapid mobilization
and return of the patient to normal activities.[27]
[39]
[40]
[41]
[42]
[43]
[44]
These new therapeutic techniques were started with ultrasonic-guided manual compression
of the neck of the aneurysm. Later, echo-guided thrombin injection was introduced
which has been tried successfully in a patient with anterior tibial artery pseudoaneurysms.[40]
Transcatheter coil embolization is another accepted treatment modality which offers
many advantages including rapid safe occlusion and this had been successfully accomplished
in the pseudoaneurysms of the anterior tibial artery as well.[40]
[41] In this procedure, occlusion should be performed both proximal and distal to the
aneurysm for complete cessation of blood flow into and from the lesion.
Recently, endovascular anatomic reconstruction of the arterial wall with covered stent
has been developed.[42]
[43]
[44] Eventually, this technique is not a vital procedure for anterior tibial artery pseudoaneurysms,
although it has been utilized in a few rare instances.
Obviously, none of these noninvasive options are recommended in the patients with
aneurysmal compressive neuropathy where excision of the aneurysm and subsequent neurolysis
of the affected nerve are the mainstay of surgery. In our patient, because of posterior
tibial neuropathy, open surgical intervention was preferred. Furthermore, reconstruction
of the artery was not indicated because of the integrity of tibioperoneal trunk and
its two major branches.
Duration and extent of compression have prognostic influence on associated neural
recovery.[12]
[13] With early diagnosis, the neural function of the compressed nerve will recover soon
after decompression.
In conclusion, we believe that this presentation can serve as a good reminder of another
uncommon possible cause of posterior tibial neuropathy diagnosed with high index of
suspicion. This report also emphasizes on the importance of taking into account the
possibility of a pseudoaneurysm in differential diagnosis and a compressive neuropathy
even years after trivial missile injuries.
