Arterial pseudoaneurysm formation is a rare consequence of orthopedic surgery. A pseudoaneurysm occurs when a blood vessel wall is breached, and the blood leaking through it is contained by hematoma, perivascular soft tissue, and the adventitia surroundings ^[1]. Clinically, such injury does not present with common signs of ischemia, and therefore may be overlooked. Pseudoaneurysms might result from Total Knee Arthroplasties (TKA), but may also follow other knee surgeries in the popliteal artery, such as superolateral, inferolateral, or inferomedial geniculate arteries ^[2].
Diaphyseal femoral fractures are common, and in adults often treated with interlocked intramedullary nailing. Vascular injuries, however, are uncommon and usually occur when the drill bit or screws have over penetrated – particularly during the distal interlocking procedure ^[3].

A 19-year-old male, normally healthy and with no medical issues, arrived to the emergency room (ER) after being involved in a motor vehicle accident. He was presented with multiple injuries including swelling, deformity with tenderness of middle thigh, sensation, and distal pulse intact. In the ER, the patient was stable with 16.1 hemoglobin (Hb). A diagnosis of diaphyseal femoral fracture was determined, and a splint was applied.
Under anesthesia, the patient underwent Closed Reduction with Internal Fixation using Antegrade Long Intra-Medullary Nail (IMN) with distal locking screw (Fig. 1 and 2). The screw was placed from lateral to medial after a stab-wound skin cut, using a mosquito for blunt dissection before drilling. Postoperatively, the patient felt well, was stable with normal blood pressure and had no tachycardia. Blood was collected during 3 days post-operation and the Hb levels were: 11.8, 8.7, and 6.8. After blood transfusion, Hb levels were improved.
A computed tomography angiography was performed, presenting an arteriovenous fistula of the lateral superior geniculate artery (Fig. 3). The artery was closed with a coil (Fig. 4) and Hb levels were recovered once more (Table 1).

Vascular injury after IMN distal interlocking, is rare and has scarce evidence in the literature. As a possible cause for this complication, Yang et al. suggested that the involved limb adducted and internally rotated, which may cause abutment of the femoral vessels to the femur, endangering the superficial femoral artery. Therefore, they suggested that during preparation of the interlocking hole, the limb will be placed in a neutral position ^[2].
Mounasamy et al. (Table 1) reported a pseudoaneurysm case of lateral geniculate artery at the distal screw insertion site of interlocked IMN, diagnosed after Doppler examination was done to exclude a recurrent abscess associated with the trauma a year before ^[4].
In a case reported by Bose et al. (Table 1), 4 years post the initial femoral nailing; a pulsatile swelling was noticed on the medial aspect of the left distal thigh. US and MRI showed a penetration of the distal locking screws tips to the mass, which was suspected to be an arterial pseudoaneurysm ^[5].
In most reported cases of post-TKA, pseudoaneurysms were also described. Pai et al. reported a false aneurysm of the inferior lateral geniculate artery, following a total knee replacement as a pulsatile mass with compressive neuropathy of the posterior tibia nerve ^[6]. Dennis et al. described a traumatic arteriovenous fistula with false aneurysm as a TKA complication ^[7]. Langkamer et al. presented a case report in which an A-V fistula was confirmed 6 weeks after TKA ^[8]. Another case of pseudoaneurysm, 3 weeks after anterior cruciate ligament repair, was presented by Oversier et al. ^[9]. Scoles et al. described a patient with hemophilic arthroplasty following synovectomy. In this case, the descending genicular artery evolved as a complication of suction drainage from a knee ^[10].
However, most reported cases of distal locking related lateral geniculate artery pseudoaneurysm, are delayed post-operative complications. The injury case presented here differs in timing, with immediate post-operative acute bleeding up to dangerously decreasing hemoglobin levels.

Our case report joins to rare evidences of pseudoaneurysm related to distal IMN interlocking. We conclude that distal interlocking screws should be carefully placed, including blunt dissection before drilling and screw placement. In addition, post-operative physical examination as well as blood count, should be performed as part of the routine.

Although hemoglobin level frequently decreases post-operation, if continuing, it might indicate a rare arteriovenous fistula as was described here. This case proves the importance of blunt dissection before drilling, as well as post-operative serial blood count as follow-up.