Osler introduced the term mycotic aneurysm in 1885 . At that time, cases were usually related to bacterial endocarditis. With the widespread use of antibiotics, the incidence of infected aneurysms has decreased, and arterial trauma has become the most frequent cause [4, 5].
The pathogenesis of mycotic aneurysms may include several different mechanisms: septic embolization lodged in the vasa vasorum or vessel lumen; contiguous septic processes extending to the peri-arterial lymphatic vessels and the vasa vasorum of nearby arteries; direct bacterial inoculation at the time of arterial trauma; bacterial infection of an intimal injury, or an atherosclerotic plaque during bacteremia; and self-induced vascular manipulation or iatrogenic causes . In one special circumstance, that of Salmonella bacteremia, it is clear that normal arterial intima, which is usually highly resistant to bacterial encroachment, may be invaded by the infectious agent. Frequently, several mechanisms operate simultaneously . In our patient’s case the exact cause of the aneurysm could not be ascertained; however, we postulate that the already vulnerable femoral arterial wall might have been damaged by the bone fragments at the fracture site during the course of manipulation and massage by the traditional bone setter, leading to acute aneurismal dilatation and eventual rupture of the femoral artery.
The diagnosis is confirmed by imaging studies (ultrasound, computed tomography, angiography or magnetic resonance angiography) and, sometimes, mycotic aneurysms are only demonstrable in this way. Mycotic aneurysms are often associated with radiographic findings: the presence of air within the aneurysm, local inflammation, contained rupture or saccular or lobulated aneurysm. We could not carry out all the necessary investigations primarily because our patient was very ill and needed urgent life-saving interventions.
S. aureus is the most commonly isolated organism in mycotic aneurysms, with Salmonella species, β-hemolytic Streptococcus, Mycobacterium tuberculosis, Escherichia coli, and anaerobic species also identified [1, 7, 8].
Mycotic aneurysms are associated with high morbidity and mortality rates, and combined therapy results in better outcome . The management of mycotic aneurysms is well established. Extra-anatomic revascularization is recommended, followed by a large excision of the aneurysm and, through a completely separate incision, debridement . Vascular reconstruction by in situ implants is possible if the bacterial agent is not multi-resistant, if the infectious process is not very extensive, and if complete debridement is feasible. In such cases, venous grafts, arterial autografts, or arterial homografts are used [7, 10]. The risk of re-infection seems to be reduced by covering the prosthesis and all sutures with a pediculated omental or muscular flap. If these techniques of revascularization fail, ligation of the arterial axes may become necessary. Ligation carries with it a 25 percent risk of ischemia and amputation . Though indicated, we could not venture into vascular reconstruction as a limb-salvaging procedure because of a lack of the necessary expertise.
Bone infection in primary osteomyelitis is usually hematogenous, however as a consequence of the HIV/acquired immunodeficiency syndrome (AIDS) pandemic osteomyelitis has been reported as a complication of pyomyositis . To avoid serious complications it is imperative to recognize, diagnose and treat osteomyelitis effectively with appropriate antibiotics. Unfortunately the diagnosis is often difficult during the first 10 to 14 days when obvious symptoms such as fever, pain, local swelling, malaise, loss of appetite, vomiting and local heat may be unremarkable. At this stage radiographic changes may remain negative. The results of blood cultures for diagnosis may be uninformative, but should be repeated as often as possible, especially during peaks of pyrexia. Diagnosis of osteomyelitis in Uganda is usually performed late because most clinicians always first think of common causes of fever such as malaria, enteric fever and upper airway infections. Some cases are diagnosed late because they first seek the services of traditional healers.
Aneurysms are associated with several complications; according to Levi et al. distal embolization occurs in up to 26 percent of cases, and acute thrombosis occurs in around 15 percent of cases. Rupture is uncommon and incidence varies between 10 percent and 14 percent of cases . Another review by Fluckiger et al. shows the risk of complications such as rupture, thrombosis and embolization to be above 50 percent. In their report, acute dilatation and rupture occurred in 34.5 percent of cases .
Mycotic aneurysms carry a poor prognosis, so it is mandatory to obtain adequate material for culture and sensitivity testing to enable a suitable combination of antibiotics to be selected. Common general principles of management include control of hemorrhage if present, the obtaining of microbial cultures, wide debridement of all infected tissue, consideration of arterial reconstruction (usually autogenous tissue, preferably through uninfected tissue planes), and continued antibiotic therapy throughout the post-operative period.