Septic True Aneurysm of the Posterior Tibial Artery Diagnosed after Anterior Arthroscopic Debridement of a Septic Ankle following Infective Endocarditis: A Case Report

Abstract

Introduction: There have been reports of true aneurysm of the posterior tibial artery, but only three reports have described true aneurysm of the posterior tibial artery at the ankle, and there has been only one report of tarsal tunnel syndrome caused by true aneurysm of this artery. In this case report, we describe a rare case of true septic aneurysm of the posterior tibial artery presenting as tarsal tunnel syndrome which was found after anterior arthroscopic debridement of a septic ankle in a 55-year-old man.

Case report: 13 years earlier, this patient had undergone aortic valve replacement for severe aortic regurgitation caused by infective endocarditis with aortic valve vegetations. Since then, the patient had been treated with the oral anticoagulant warfarin. The aneurysm was successfully treated by a saphenous vein graft and administration of antibiotics. The patient likely developed septic ankle and aneurysm as a consequence of infective endocarditis.

Conclusions: Magnetic resonance imaging should be performed before arthroscopic surgery to rule outaneurysm, especially in a patient with a septic ankle and/ora history of infective endocarditis.

Keywords: Anterior arthroscopy; infective endocarditis; posterior tibial artery; septic ankle; tarsal tunnel syndrome; true septic aneurysm.

Figure 1

Plain radiographs showing osseous destruction and diffuse narrowing of the right ankle joint on anterior-posterior (a) and lateral (b) views.

Figure 2

Computed tomography images reveal osseous erosions and diffuse narrowing of the right ankle joint on coronal (a), sagittal (b), and axial (c) views.

Figure 3

Photographs taken during anterior ankle arthroscopy showing significant adhesions resulting in severe infective synovitis within the ankle joint (a) and extensive severe chondral fibrillation and subchondral erosion (b). (c) Photograph of a synovial tissue sample obtained for culture and histopathologic analysis.

Figure 4

Hematoxylin-eosin staining shows chronic synovitis associated with infiltration of neutrophils and lymphocytes, angiogenesis, and accumulation of hemosiderin, indicating a chronic inflammatory response to infection.

Figure 5

Photograph of the right ankle and foot showing swelling posterior to the medial malleolus.

Figure 6

Color and duplex Doppler ultrasonography showing the communication between the posterior tibial artery and the true aneurysm.

Figure 7

Color and duplex Doppler ultrasonography showing the communication between the posterior tibial artery and the true aneurysm.

Figure 8

Photographs taken during reconstruction of the posterior tibial artery demonstrate that the true septic aneurysm was caused by dilation of the wall of the posterior tibial artery (a). The wall of the artery reconstructed using a reversed saphenous vein graft (b).

Figure 9

Post-operative enhanced three-dimensional computed tomography image showing that the posterior tibial artery is partially interposed with the saphenous vein graft.

Figure 10

Hematoxylin-eosin staining shows that the arterial wall is preserved, the intimal layer not continuous, and the elastic fibers disrupted. Infiltration of neutrophils and lymphocytes, hemosiderin, and ingrowth of small new vessels can be seen in the aneurysmal wall. The findings indicate a chronic inflammatory response to infection.