Emphysematous osteomyelitis (EO) is an extremely rare infection caused by gas-producing bacteria.1 It has high morbidity and mortality rates, which means it requires an early and aggressive therapeutic approach.2 We present a case of EO of the hip with poor progress in a patient who presented with septic shock. We show a characteristic radiological sign which was key to establishing the suspected diagnosis.
This was a 52-year-old woman with a history of type II Chiari malformation with secondary paraplegia who was brought to Accident and Emergency due to disorientation and low level of consciousness for a number of hours.
On arrival at the hospital she was stuporous, tachypnoeic and tachycardic. Examination revealed the presence of a pressure ulcer in the right gluteus developed in the previous month and managed at home with topical wound care, despite which it had increased in extension and depth.
The analysis revealed leucocytosis (19,200 leucocytes/μl) and elevated C-reactive protein (CRP) (>25mg/dl). Brain computed tomography (CT) and chest x-ray showed no abnormalities.
The patient's level of consciousness deteriorated and she became haemodynamically unstable, requiring admission to the ICU.
Given the suspicion of sepsis with a focus on the skin and soft tissues, an CT of abdomen and pelvis with contrast was requested (Fig. 1), which showed findings compatible with EO.
Extensive inflammatory process mainly involving the components of the right hip, with the presence of gas in the thickness of the bone of the femoral head ("pumice stone sign") (A and C), in the iliac acetabulum and in the right femoroacetabular joint (B). The presence of gas can also be seen in the adjacent soft tissues (A and C).
The Orthopaedics and Trauma Department was contacted, and they performed urgent surgery with resection of the right femoral head, cleaning and debridement.
Initially, she was given empirical antibiotic therapy with meropenem, linezolid and amikacin. The following were isolated in blood cultures without antibiotic pressure: Streptococcus anginosus, Streptococcus constellatus, Bacteroides fragilis group, Clostridium ramosum (2/2). Cultures of bone and periarticular tissue after surgery grew: Escherichia coli, Streptococcus anginosus, Streptococcus constellatus, Eikenella corrodens, Clostridium spp., Prevotella intermedia, Parvimonas micra and Bacteroides caccae.
After the above isolations, the antibiotic therapy was adjusted to piperacillin/tazobactam, ciprofloxacin and daptomycin. Given the probable involvement of anaerobic bacteria (Clostridium spp. and Bacteroides spp.), metronidazole was added to the combination after performing antibiotic sensitivity tests.
The patient made very slow progress, with the need for drainage of collections and debridement of pressure ulcers. After more than four months in hospital, the focus was under control and the patient was discharged.
The presence of intraosseous gas was described for the first time in 1981.3 When it is identified in the vertebral bodies, it is usually related to non-infectious causes.1 In contrast, in the extra-axial skeleton, it is a finding highly suggestive of EO.4
EO is a serious bone infection with very few cases described in the literature.1 It is generally produced by haematogenous or contiguous spread. In the first case, monomicrobial infections predominate, while in the second, polymicrobial infections.2 When it spreads by contiguity, it is usually derived from an intra-abdominal infection, spinal surgery, or skin and soft tissue infection (SSTI).5
The identification of polymicrobial bacteraemia should alert to the presence of an uncontrolled focus, generally intra-abdominal.6 In our patient, we suspect that the most likely mechanism was the deep extension of an SSTI due to her history of pressure ulcer with adjacent pyomyositis and arthritis. This case illustrates the importance of adequate management of chronic wounds and pressure sores, as they can be a focus of polymicrobial bacteraemia.
From the microbiology point of view, anaerobic bacteria and enterobacteria are usually isolated7 In our case it was a polymicrobial infection with predominance of Clostridium spp. and Bacteroides spp. Given the severity of anaerobic bacteraemia, antibiotic sensitivity tests must be performed to confirm the sensitivity of these species to metronidazole, piperacillin/tazobactam and carbapenems, as sensitivity can vary between different species and strains.8
Contrast-enhanced CT is the most sensitive test for diagnosing EO, showing the “pumice stone sign” in more than 90% of cases. Other typical radiographic findings are emphysema in the surrounding soft tissues and the absence of destruction of the cortical bone.1
Treatment is combined with parenteral broad-spectrum antibiotic therapy for at least four weeks and surgical control of the focus.1,4,9
It is important to define the optimal duration of antibiotic therapy and the need for surgical intervention in all cases, as multiple or complex surgical interventions can increase mortality rates.9
FundingThe authors declare that they did not receive any funding.
AuthorshipAll authors contributed to the preparation of the article.
Conflicts of interestThere are no conflicts of interest in the preparation of this article.
