Background <p>Primary intraosseous arteriovenous malformations (AVMs) are exceedingly rare vascular anomalies that can weaken bone architecture and predispose to pathological fracture. Their imaging appearance frequently mimics malignant bone tumors, creating significant diagnostic and therapeutic challenges. Recognition of the characteristic imaging features of intraosseous AVMs in the setting of pathological fracture is essential to avoid misdiagnosis and to prevent catastrophic hemorrhagic complications during inadvertent surgical intervention.</p> Case presentation <p>A 25-year-old male presented with severe pain, swelling, deformity of the right thigh, and inability to bear weight following a fall from height. Initial radiographs demonstrated a displaced mid-shaft femoral fracture with permeative lytic and sclerotic changes, raising suspicion of a pathological fracture. Magnetic resonance imaging (MRI) revealed multiple dilated serpiginous intramedullary flow voids extending into adjacent muscle planes, consistent with a high-flow intraosseous AVM, and a large lobulated flow void between the fracture fragments communicating with adjacent dilated tortuous vessels, consistent with a traumatic pseudoaneurysm. Computed tomography (CT) angiography confirmed multiple dilated vessels supplied by branches of the right internal iliac, profunda femoris, and superficial femoral arteries with early venous drainage and a large contrast-filled pseudoaneurysm communicating with the medullary cavity. By the 2018 International Society for the Study of Vascular Anomalies (ISSVA) classification, the lesion was categorized as a simple, high-flow arteriovenous malformation of the lower extremity (Schobinger Stage III). The patient underwent transarterial endovascular embolization of the AVM nidus and pseudoaneurysm using an n-butyl cyanoacrylate (NBCA)–Lipiodol emulsion via a retrograde left common femoral artery approach, with embolization of the nidus and obliteration of the traumatic pseudoaneurysm with reduction in arteriovenous shunting through the embolized territory achieved on post-embolization digital subtraction angiography (DSA). Following multidisciplinary review with Orthopedics and Cardiovascular and Thoracic Surgery (CTVS), definitive intramedullary nailing was deferred because of extensive intraosseous AVM involvement along the medullary trajectory of any intended nail, rendering the femoral cortex fragile and unsuitable for safe internal fixation. The patient was managed conservatively with a Thomas splint, limb immobilization, analgesia, and bone-health optimization. At the time of discharge approximately seven days after the embolization session, the patient was clinically stable, with intact distal neurovascular status and no interval hemorrhagic event. The patient was subsequently lost to follow-up despite repeated attempts at contact through the details provided at admission, and therefore long-term clinical and imaging outcome data are not available for this report.</p> Conclusions <p>This case underscores the pivotal role of multimodality imaging in evaluating pathological fractures with atypical lytic changes, and illustrates that a staged, multidisciplinary management strategy—combining endovascular embolization with individualized, imaging-guided decisions about orthopedic fixation—can safely control a high-flow intraosseous AVM complicated by traumatic pseudoaneurysm while avoiding potentially fatal intraoperative hemorrhage. In this case, conservative orthopedic management after endovascular control was the multidisciplinary strategy selected on the basis of the specific intraosseous anatomy; further multi-case series are needed before this approach can be broadly recommended. Post-embolization DSA follow-up is essential to confirm treatment response and to guide further embolization and orthopedic planning.</p>