CASE 17488 Published on 27.10.2021

Intraosseous air bubbles, a sign of emphysematous osteomyelitis.

Section

Musculoskeletal system

Case Type

Clinical Cases

Authors

Lucía Lara Huéscar, Javier San Miguel Espinosa, Luz María Morán Blanco, Paulino García Benedito, Carlos Rubio Sánchez, Patricia Oliveros Ordás

Department of Radiology, Hospital Universitario Puerta de Hierro Majadahonda, Madrid, Spain)

Patient

69 years, male

Categories
Area of Interest Musculoskeletal bone, Musculoskeletal joint, Pelvis ; Imaging Technique CT, MR
Clinical History

A 69-year man came to the Emergency Department with low back pain that irradiated to his left leg. On examination, he was febrile, tachycardic, and hypotensive. His white blood count showed sepsis. There was no significant past medical history.

An abdominopelvic-CT was performed before being transferred to the Intensive Care Unit (ICU).

Imaging Findings

Emergency CT revealed multiple pockets of gas within the medullary cavity of the head, neck, and trochanteric region of the left femur, in addition to joint effusion accompanied by gas within the ipsilateral hip joint cavity. No cortical bone destruction was observed. (Figures 1A-1B). These imaging findings were consistent with emphysematous osteomyelitis and septic arthritis.

Thrombophlebitis of the inferior mesenteric vein was also observed in this study. (Figure 1c)

Blood cultures demonstrated Escherichia coli, and intravenous antibiotic therapy was given to the patient. Based on patient clinical deterioration, an additional pelvic and lower limbs CT was performed four days later. It showed more bubble gas within the femur and extended to the ilium, ischium and, acetabulum in the left hemipelvis. Air bubbles were also noted in the surrounding soft tissues (adductor and quadricipital compartment). (Figures 2a-2b-2c).

A magnetic resonance imaging (MRI) confirmed the progression of emphysematous osteomyelitis with necrotizing fasciitis and myositis. (Figure 3)

The patient was urgently planned for surgery. (Figures 4a-b)

Discussion

Intraosseous gas was first described as a sign of osteomyelitis by Ram in 1981 [1]. Emphysematous osteomyelitis (EO) is a rare, aggressive, and potentially fatal variant of osteomyelitis related to gas-forming organisms and usually secondary to hematogenous spread [2,3].

EO is usually a clinically unsuspected condition that is diagnosed upon radiological findings. It most commonly affects patients with significant underlying comorbidity (malignancy, DM, alcohol abuse, etc). It is related to high mortality, requiring early diagnosis and aggressive therapeutic intervention [2,3].

In our case, the source was suspected to be acute diverticulitis which complicated inferior mesenteric vein thrombophlebitis. Escherichia coli was found in blood, as well as in articular and bone cultures.  Surprisingly, our patient has not known comorbidities.

Computed tomography (CT) constitutes the imaging modality of choice because it is the most sensitive method for detecting intraosseous gas. Typically, EO is seen as multiple (more than 3) irregular small foci of intramedullary gas, without associated cortical destruction. This pattern was named as “pumice stone” sign. (4) Accompanying soft tissue emphysema is also identified in the majority of EO cases and MRI is the modality of election for this compromise. MRI is essential to detect soft tissue collections that could be aspirated to reach the diagnosis and to obtain the isolation of microorganisms involved in the infection.

Diagnosis of septic arthritis was given by the presence of gas within the joint cavity, as this is a specific sign of septic origin (while joint effusion alone can be observed in many other conditions).

A key imaging feature of EO is the lack of associated cortical bone destruction: the combination of both intraosseous and extraosseous gas without cortical destruction is very specific to this entity [4].

The most common sites of EO, include the pelvic bones (38%), vertebral bodies (32%), and femurs (24%) [4].

Alternative considerations resulting in intraosseous gas include trauma, postsurgical change, lymphangiomatosis of the bone, degenerative disease, osteonecrosis, and neoplasm [5].

In the absence of a history of surgery, trauma, or degenerative change, the intraosseous gas in the appendicular skeleton is highly suggestive of emphysematous osteomyelitis. However, the intraosseous gas in vertebral bodies is generally due to a non-infectious cause, most commonly being a degenerative process.

Treatment of patients with EO should be aggressive with long term (at least 4 weeks) antibiotic therapy in addition to surgical debridement [5,6].

Our patient was attended to in the ICU for 41 days and surgical debridement was needed several times, including Girdlestone resection arthroplasty. Patient evolution was satisfactory being discharged after completing the full course of antibiotics.

Differential Diagnosis List
Emphysematous osteomyelitis due to Escherichia coli
Osteonecrosis
Degenerative disease
Lymphangiomatosis of the bone
Neoplasm
Final Diagnosis
Emphysematous osteomyelitis due to Escherichia coli
Case information
URL: https://www.eurorad.org/case/17488
DOI: 10.35100/eurorad/case.17488
ISSN: 1563-4086
License