Popliteal aneurysm

　　The pathogenic causes of popliteal aneurysm mainly include the following aspects:

　　1. Trauma: Traumatic popliteal aneurysms are mostly pseudoaneurysms and can be caused by fractures or penetrating injuries near the knee joint or by blunt injuries to the popliteal artery due to external force. In addition, iatrogenic trauma is also increasing, such as reports of popliteal aneurysms caused by arthroscopy for meniscectomy. These factors all cause damage to the popliteal artery wall, making it weak and leading to the formation of an aneurysm. Traumatic aneurysms are more common in young patients.

　　2. Exercise: Continuous flexion and extension of the knee joint can also easily cause vascular dilation and the formation of an aneurysm. Some scholars have observed that the popliteal artery runs through the adductor canal of the middle and lower thigh and between the popliteal ligaments behind the knee, which can cause local extrinsic stenosis of the popliteal artery. The distal part of the stenosis can form an aneurysm, which proves that the dilation after popliteal artery stenosis can gradually develop into a popliteal aneurysm.

　　3. Infection: This includes endogenous infections such as infected emboli, sepsis, or direct involvement of infection foci, as well as exogenous infections, trauma, and iatrogenic injuries that can cause weakness and necrosis of the arterial wall, eventually leading to the formation of an aneurysm.

　　4. Popliteal artery compression syndrome: It often occurs in young adults due to the compression of the popliteal artery by abnormal muscles, fibrous bands, etc. in the popliteal fossa. Repeated chronic injury to the popliteal artery can cause degenerative changes in the artery, and atherosclerosis development and arterial stenosis at the site of compression, thrombosis, or intimal hyperplasia, leading to increased pressure in the proximal popliteal artery and causing post-stenotic arterial dilatation into an aneurysm.

　　5. Other causes: Other causes such as degenerative changes in the middle layer of the artery, nodular arteritis, and Behcet's disease can also cause popliteal aneurysm, but they are less common.

　　The distal embolization and rupture of popliteal aneurysm are the main complications of the disease. Among them, the most common is lower limb ischemia caused by thrombosis in the aneurysm lumen or by the detachment and embolization of stratified thrombus in the aneurysm cavity, leading to the tibial and peroneal arteries. This can result in limping, resting pain, and may also cause skin necrosis and lower limb gangrene due to acute complete occlusion.

　　Smaller popliteal aneurysms without complications are often asymptomatic, but complications and symptoms will eventually appear. Common clinical manifestations are as follows:

　　1. Pulsatile mass in the popliteal fossa: 48% of patients can detect the mass and provide complaints. Those who cannot report the presence of a mass are often overweight, stiff joints, and elderly patients. During the examination, the mass is easier to palpate in the flexed knee position. The mass can be pulsatile or non-pulsatile due to the aneurysm being filled with thrombus.

　　2. Ischemia of the foot and lower leg: This is the most common symptom of popliteal aneurysms, and can include intermittent claudication, rest pain, ulcer formation leading to gangrene (the former 45%, the latter three 38%), and the cause of limb ischemia is the formation of thrombus within the aneurysm, the continuous thickening of the thrombus adhering to the wall, which can completely block the aneurysm; secondary thrombosis can also occur in the distal branches of the popliteal artery; due to the movement of the knee joint, the thrombus adhering to the wall can be dislodged, causing repeated episodes of embolism in the distal artery.

　　3. Compression of adjacent tissues: The original popliteal artery is closely adjacent to the popliteal vein and the tibial nerve. When the aneurysm grows larger, it first compresses the popliteal vein, causing venous return obstruction, lower leg edema, and even thrombosis within the vein (13%), and further growth of the aneurysm can compress the tibial nerve (6.4%), causing pain and movement dysfunction.

　　4. Rupture and hemorrhage: rare.

　　Examination can show an expansile, pulsatile mass in the popliteal fossa that is consistent with the heartbeat of the heart. The proximal type can be palpated on the medial and posterior aspects of the lower third of the thigh, while the central and distal types can only be palpated on the posterior aspect of the popliteal fossa. Based on the symptoms of limb ischemia and compression, combined with signs such as limb coldness, numbness, weakened or absent pulse, pulsatile mass in the popliteal fossa, and eggshell-like calcification shadows on X-ray films, as well as findings from B-ultrasound, CT, arteriography, and other examinations, the diagnosis can be established without difficulty. If limb ischemia occurs, there may be signs such as pale skin, limb endulceration or gangrene, weakened or absent popliteal pulse, limb coldness, etc. If there is a suspicion of popliteal aneurysm, the contralateral limb and other areas should also be examined to confirm whether there is a concurrent aneurysm in other locations.

　　The prevention of popliteal aneurysms mainly focuses on early detection and early treatment. The greatest danger of the disease is ischemia caused by thrombosis or embolism leading to amputation. It is reported that the amputation rate can reach 16% to 44%, indicating that postoperative follow-up for patients with popliteal aneurysms needs to be strengthened to prevent the occurrence of new aneurysms.

　　The examination items for popliteal aneurysms are as follows:
　　1. X-ray examination
　　(1) Knee X-ray: The anteroposterior and lateral views can show soft tissue shadows in the popliteal fossa, and there may be eggshell-like calcification shadows.
　　(2) Lower extremity arteriography: It can show the size and extent of the popliteal aneurysm, and most importantly, understand the inflow and outflow conditions of the aneurysm near and far, which is very important for determining the treatment plan.
　　2. Doppler ultrasound
　　It can be used to diagnose popliteal aneurysms and understand the situation of the thrombus adhering to the wall and the hemodynamics within the aneurysm cavity. It can also be distinguished from arteriosclerotic occlusive disease, thromboangiitis obliterans, and solid tumors in the popliteal fossa.
　　3. CT scan
　　It can show the size, range, calcification of the aneurysm wall, and the relationship between the aneurysm and surrounding tissues.

　　Patients with popliteal aneurysms should pay attention to a light and nutritious diet. After surgery, ensure that patients have adequate rest, avoid fatigue and emotional excitement. If patients do not have anemia, there is no need for blood transfusion. Pay attention to food therapy in daily diet. The following is a recipe for food therapy:
　　1. Patients with decreased appetite, fatigue, fullness in the abdomen, and mainly Qi deficiency symptoms after surgery or radiotherapy or chemotherapy.
　　Options: 30 grams each of Codonopsis pilosula and Atractylodes macrocephala (separately wrapped in gauze), 50 grams each of Poria, Dioscorea opposita, lotus seeds without the heart, Job's tears, 15 dates, 100 grams of glutinous rice, and an appropriate amount of sugar.
　　Preparation: Add about 1000 ml of water to the herbs, boil, and then simmer with low heat for 30 minutes. Remove the bags of Codonopsis pilosula and Atractylodes macrocephala, add glutinous rice, sugar, and an appropriate amount of water to cook porridge.
　　2. Patients with deficiency of Yang after radiotherapy or chemotherapy, or in the late stage, with symptoms such as weakness, aversion to cold, cold limbs, weakness of the limbs, lack of spirit, pale complexion, and pale tongue.
　　Options: 500 grams of turtle meat, 10 grams of American ginseng, 3 grams of cornu cervi, 50 grams of Job's tears, and 15 grams of Astragalus membranaceus.
　　Preparation: Clean and cut the turtle meat, wrap the herbs in gauze, and put them in the pot with 5 slices of ginger and an appropriate amount of clean water. Boil after the water boils, add an appropriate amount of wine and cooking oil, and simmer with low heat until the meat is tender, then season with salt and other seasonings.
　　3. Anemia or decreased white blood cells after surgery, radiotherapy, or chemotherapy, with symptoms of both deficiency of Qi and blood, such as pale complexion, dry throat and mouth, shortness of breath on exertion, palpitations, and insomnia.
　　Options: 1000 grams of hen, 10 grams each of Angelica sinensis, Radix Paeoniae alba, Radix Rehmanniae preparata, Ligusticum chuanxiong, Atractylodes macrocephala, and Glycyrrhiza uralensis, 15 grams each of Codonopsis pilosula and Poria, 5 slices of ginger.
　　Preparation: Clean the chicken, cut into pieces, put them in a sand pot, add ginger, all the herbs (sand-packed), and an appropriate amount of clean water. Boil with high heat after boiling, then simmer with low heat until the chicken is tender, remove the herb bag, and season with salt and other seasonings.

　　Popliteal aneurysms are generally treated by surgery, with the principle of excising the popliteal aneurysm and reconstructing the popliteal artery.

　　1. Preoperative preparation

　　1. For a unilateral popliteal aneurysm, it is necessary to examine the contralateral lower limb and abdominal areas to determine whether there is a contralateral popliteal aneurysm, abdominal aortic aneurysm, or other arterial aneurysms at the same time. If one side of the bilateral popliteal aneurysms has thrombosis with symptoms (but without severe ischemia threatening the limb) and the other side is asymptomatic, then the asymptomatic side of the popliteal aneurysm should be treated first.

　　2. Arteriography must be performed before surgery to clarify the patency of the inflow and outflow channels at both near and distant ends. In the case where the inflow channel is still good, the patency of the outflow channel (the three arteries of the anterior tibial, posterior tibial, and fibular arteries) is a key factor determining the success rate.

　　3. Due to the fact that patients with popliteal artery disease often have concurrent coronary heart disease, hypertension, renal lesions, and cerebrovascular lesions, in order to reduce postoperative complications, it is necessary to actively treat these concurrent diseases before surgery, control the progression of the disease, and improve organ function.

　　4. Routine use of antibiotics for 1 to 2 days before surgery.

　　5. Preoperative thrombolytic therapy: In recent years, thrombolytic therapy through the artery has gradually become an effective preoperative adjuvant treatment for popliteal aneurysms complicated with acute lower limb ischemia. However, thrombolytic therapy also has limitations. For patients with severe limb ischemia, such as limb distal gangrene and neurological symptoms, thrombolytic therapy should be contraindicated. Immediate surgery should be performed, and thrombolytic therapy can be performed intraoperatively to improve the efficacy of surgery.

　　Currently, thrombolytic therapy advocates for direct, high-dose, short-term thrombolytic therapy through arterial catheterization. Options include streptokinase, urokinase, tissue plasminogen activator (t-PA), etc. For example, urokinase can be perfused at a rate of 100,000 U per hour, and after continuous application for 18 hours, perform an angiography again to further understand the patency of the distal outflow tract, and then perform surgical excision of the popliteal aneurysm and vascular reconstruction.

　　Second, Surgical Methods

　　The goal of surgical treatment for popliteal aneurysms is to remove the aneurysms that are highly disabling, restore blood supply to the lower limb, eliminate the risk of aneurysm rupture, and common surgical methods include four:

　　(1) Completely excise the aneurysm and perform end-to-end anastomosis of the popliteal artery or autologous vein transplantation. This is suitable for cases with small tumors.

　　(2) Excise the aneurysm and perform bypass transplantation surgery using autologous veins or artificial blood vessels.

　　(3) Arterial aneurysm exclusion, ligate the proximal and distal ends of the aneurysm, and then perform interposition surgery between the great saphenous vein or artificial blood vessel or bypass transplantation surgery. This is suitable for cases with severe adhesions between the aneurysm and the popliteal vein.

　　(4) Partially resect the tumor wall, ligate the openings of the artery branches within the tumor, reconstruct the blood vessels in the tumor cavity, and finally wrap and protect the blood vessels with the tumor wall. This is suitable for cases with large tumors and severe adhesions with surrounding structures.

　　Third, Surgical Approach and Method

　　According to the condition, there are three types of surgical approaches to choose from: medial approach; posterior approach; bypass transplantation.

　　Fourth, Postoperative Management

　　1. Antibiotics should be continuously applied for 1 week after surgery.

　　2. If there is a long-term ischemia of the lower limb and foot before surgery, a deep fasciotomy should be performed during the vascular reconstruction to reduce the occurrence of compartment syndrome.

　　3. Anticoagulation and antithrombotic therapy are routinely administered after surgery.

　　4. Pay close attention to the blood supply of the distal limb. If there are symptoms and signs of ischemia, surgery may be necessary again.