Pseudoaneurysm of the lateral inferior genicular artery following anterior cruciate ligament reconstruction.

Clinical History

A 23 year old man presented with right knee pain and local swelling three days after anterior cruciate ligament (ACL) replacement because of a skiing trauma.

Imaging Findings

A 23-year-old young man underwent orthopaedic arthroscopic surgery for ACL replacement after a skiing trauma. Three days after surgery, he showed local inflammation signs, like swelling and anatomic profile deformities, increasing right calf pain, mainly with flexion and local joint’s warmth. All of the extremity pulses were palpable, and there was no evidence of venous obstruction. A knee US was then performed and showed a liquid sinovial bursa effusion that appeared anechoic and homogeneous, in para-patellar region continuing in joint region. Moreover, we noticed a large haematoma of gastrocnemius medial head and suspecting a supplied haematoma, the patient underwent a spiral CT angiography examination. It revealed a small inferior-lateral right knee artery pseudoaneurysm probably due to surgical treatment with haematoma and effusion. In order to keep the pseudoaneurysm out of the blood flow, in agreement with the orthopaedic specialist, a lower-extremity arteriography were immediately performed in our hospital. It confirmed the pseudoaneurysm presence, and so, we proceeded to subsequent embolization of the lesion with a microcoil (3x60mm). Six days later a color Doppler US showed the pseudoaneurysm was without flow and it demonstrated the initial resolution of the haematoma.

Discussion

Pseudo-aneurysm, also termed false aneurysm, is a leakage of arterial blood from an artery into the surrounding tissue with a persistent communication between the originating artery and the resultant adjacent cavity caused by arterial wall lesions. Pseudo-aneurysms of vessels are rarely related to iatrogenic injuries such as catheterisation and orthopaedic procedures. They are most commonly related to blunt or penetrating trauma. Unusual cases of pseudo-aneurysms and aneurysms related to Ehnler Darlos, neurofibromatosis, and Behcet’s disease have been reported. The popliteal artery descends obliquely as a continuation of the superficial femoral artery and crosses the knee joint line, closely opposed to the posterior capsule of the knee (mean distance 0.96–3.15 mm), placing it at risk of injury during arthroscopy and knee arthroplasty procedures.
Usually, some precautions are also performed in surgical operations to minimize the risks, like the flexed knee position or special surgical devices, but sometimes they are not sufficient to avoid all risks. Generally, the documented mechanisms of injury can be classified into 4 general categories: arterial occlusion, arterial severance, arteriovenous fistula formation, and pseudo-aneurysmal formation. Popliteal artery pseudoaneurysms are usually not recognized unless the patient suffers from unusual and persistent knee pain, swelling, and paresthesia. The use of colour-Doppler US is recommended in patients with such symptoms after a knee surgery, to exclude deep venous thrombosis or popliteal artery pseudo-aneurysms.
The criteria used to diagnose a pseudo-aneurysm include: swirling colour flow seen in a mass separated from the affected artery, colour flow within a tract leading from the artery to the mass consistent with pseudo-aneurysm neck, and a typical “to and from” Doppler waveform in the pseudo-aneurysm neck. Usually, spiral CT angiography and digital subtraction angiography (DSA) are used to confirm the diagnosis; the last also for the treatment.
Pseudo-aneurysms of popliteal or infrapopliteal vessels can be treated with percutaneous injection of thrombin or with transcatheter embolization with acrylate adhesive “glue” , coils or stent grafts deployment. This technique is less invasive than open surgical repair, especially in patients in whom these complications develop in the first few days after surgery. The results achieved by endovascular treatment of these lesions are satisfactory and represent a valid alternative to conventional vascular surgical procedures.

Differential Diagnosis List

Final Diagnosis

Pseudoaneurysm of the lateral inferior genicular artery.

URL:	https://www.eurorad.org/case/7125
DOI:	10.1594/EURORAD/CASE.7125
ISSN:	1563-4086