Pseudoaneurysm of a Genicular Branch of the Popliteal Artery and Deep Venous Thrombosis: An Unusual Presentation of an Osteochondroma

Editor: Osteochondroma is the most common primary bone tumor (1,2). Most osteochondromas are asymptomatic and diagnosed incidentally on radiologic studies (1,2). Symptomatic osteochondromas typically manifest because of the effects of a variety of complications (1,2). Vascular complications of osteochondromas are rare (1–3) and include pseudoaneurysm formation, arterial thrombosis, limb ischemia, and deep venous thrombosis (1–3). A 12-year-old boy, who was otherwise healthy, fell to the ground grasping his thigh when his left leg gave way on rising after playing video games for 3 hours. The pain was not relieved with an over-the-counter pain reliever and a warm bath and he was taken to the emergency department, where he was examined 8 hours after his fall. He had a 7/10 pain score in his left popliteal fossa and maintained his knee in 30° flexion. He was afebrile with stable vital signs. There was some calf swelling, but no pulsatile mass, palpable thrill, audible bruit, or signs of inflammation locally despite being exquisitely tender to palpation. Peripheral pulses were preserved with a brisk capillary refill. The ankle-brachial index was 1.1. Radiographs obtained in the emergency department revealed a bony excretion in the distal femur, but no fracture. An ultrasonographic scan obtained with color Doppler flow depicted a pseudoaneurysm in the popliteal fossa and a nonocclusive thrombus in the femoral vein and above-knee popliteal vein. The patient was admitted and placed on a heparin drip with a sliding scale per protocol. Computed tomographic (CT) angiography helped confirm the presence of the bony excretion and localized the pseudoaneurysm to a genicular branch of the popliteal artery (Fig 1). A soft tissue mass surrounding the pseudoaneurysm and the bony excretion prompted magnetic resonance (MR) imaging of the left knee (Fig 2). This revealed the bony excretion to have bone marrow continuity with the femoral diaphysis and a thin cartilage cap. The soft tissue mass was not in continuity with the bony excretion and had characteristics typical of a hematoma. A provisional diagnosis of a femoral osteochondroma complicated by a ruptured pseudoaneurysm of a genicular branch of the popliteal artery and associated deep venous thrombosis (DVT) was made. Four days after presentation, the patient underwent evacuation of the hematoma and excision of the pseudoaneurysm with ligation of the donor genicular branch and excision of the presumed osteochondroma. He was discharged home the next day with anticoagulation medications to control his DVT. Histologic examination of the excised specimen showed the typical features of an osteochondroma, with a cartilage cap and underlying osteocartilaginous trabeculae with associated adjacent cortical bone. Seven months after surgery, the patient is doing well. Osteochondroma occurs in 1%–2% of the population (1,2) and comprises 10%–15% of all bone tumors and 20%–50% of benign bone tumors (1,3). Osteochondromas are typically asymptomatic and diagnosed as incidental findings on radiologic studies (1,2). Symptomatic osteochondromas manifest in young adults most commonly as a painless, nontender mass (1,2). Complications are rare and include cosmetic and osseous deformity, pathologic fracture, neurovascular complications, and malignant transformation (1–3). Osteochondromas rarely manifest as vascular complications (1–3); however, approximately 100 cases presenting with vascular complications have been reported (2). Vessel displacement or compression, pseudoaneurysm formation, limb ischemia, and development of DVT have all been reported (1,2). The femur is the most common location of osteochondroma formation (30% of cases), with the distal aspect being three times more commonly affected than the proximal aspect (1–3). This makes the popliteal vessels particularly susceptible to vascular complications (1–3), with most of these comprising pseudoaneurysm formation of the popliteal artery (2). This may reflect the common involvement of the distal femur with osteochondroma (1–3) and the relative fixation of the popliteal artery proximally at the adductor canal and distally by its branches (1,3). It has been postulated that the ossification of the cartilaginous cap during skeletal maturation causes the surface of osteochondromas to harden and that repeated micro trauma to the fixed popliteal artery damages the integrity of the vessel wall (1–3). Although a history of trauma has been reported in some cases, it is equally common to have no history of trauma (2). Clinical symptoms of vascular presentation of osteochondromas vary greatly, the most common being the classic pulsatile mass of an aneurysm (2). Other presentations include nonpulsatile mass, distal ischemia, soft tissue swelling and edema, phlebitis, and parasthesias (2). Direct compression of the popliteal artery and vein has been reported in two patients (4,5), and compression of the popliteal vein by a popliteal artery pseudoaneurysm was the inciting factor (6). Surgery remains the accepted treatment of vascular complications of osteochondromas (2,3). This enables definitive treatment of the vascular complication with pseudoaneurysm ligation and repair of the donor artery along with excision of the underlying osteochondroma (1). In conclusion, osteochondromas are common bone tumors that typically have a benign course. Presentation with vascular complications is rare and occurs predominantly in young patients. The diagnosis of an osteochondroma should be suspected in any young patient presenting with vascular symptoms in a limb, especially the distal femur. Surgical DOI: 10.1016/j.jvir.2007.01.019 Letters to the Editor