Emphysematous osteomyelitis has rarely been described, and to the authors' knowledge, it has not been described in the orthopedic literature. Intraosseous gas was first reported as a sign of infection in 1981.1 It indicates an aggressive, often fatal infection with a mortality rate greater than 30%.2–5 A rare entity with only 30 previously reported cases,3 emphysematous osteomyelitis requires aggressive surgical debridement and management. Organisms found to form gas within bone include Escherichia coli, Klebsiella pneumoniae, Enterobacter aerogenes, Fusobacterium necrophorum, Pseudomonas species, Streptococcus species, Salmonella species, Clostridium species, and fungi.2,3,5–9 To the authors' knowledge, no prior reports of emphysematous osteomyelitis within a femoral shaft exist. The authors report a case of Escherichia coli emphysematous osteomyelitis in bilateral femoral shafts managed with an intramedullary Reamer/Irrigator/Aspirator (DePuy Synthes, West Chester, Pennsylvania) and insertion of antibiotic-laden cement rods.10
A 60-year-old woman with a history of rheumatoid arthritis presented with 3 months of left thigh pain that had acutely worsened during the week prior to admission. She reported similar symptoms in the right thigh 3 months preceding the onset of her current pain, but stated that the pain had since resolved. She was actively undergoing prednisone therapy managed by her rheumatologist and had received multiple knee intra-articular steroid injections, the most recent administered 2 weeks prior to admission.
Initial laboratory test results indicated elevated inflammatory markers (erythrocyte sedimentation rate, 47 mm/h; C-reactive protein, 25.3 mg/dL; white blood cell count, 16.6×103/mm3). Radiographs did not show cortical erosions, sequestra, or other evidence of osteomyelitis, but did raise concern for subcutaneous gas (Figure 1). A computed tomography scan of the left thigh revealed a large subcutaneous abscess along the medial aspect of the distal two-thirds of the femur (Figure 2). In addition, intramedullary gas consistent with emphysematous osteomyelitis was detected.
Anteroposterior radiographs of the right (A) and left (B) femurs on the day of presentation suggestive of subcutaneous and intraosseous gas of the left distal femur.
Preoperative coronal (A), sagittal (B), and axial (C) computed tomography scans of the left femur. Subcutaneous and intraosseous gas detected at the junction of the middle and distal thirds.
Broad-spectrum therapy was initiated (vancomycin, piperacillin/tazobactam, and clindamycin), and the patient was brought to the operating room for emergent debridement of the left thigh to temporize the soft tissue infection. Bone cultures from this initial debridement indicated Escherichia coli. Magnetic resonance images of both thighs were obtained for preoperative planning of the staged debridements. They revealed signal changes consistent with subacute osteomyelitis, per the radiologist's report (Figure 3).
T2-weighted magnetic resonance images of the right (A) and left (B) femurs following the emergent irrigation and debridement of the left femur prior to any operative intervention on the right. Bilateral fluid and gas consistent with emphysematous osteomyelitis are seen.
The patient subsequently underwent Reamer/Irrigator/Aspirator debridement of the bilateral femurs, followed by anterograde insertion of intramedullary rods composed of bacteria-specific antibiotic cement (Figure 4). The lead author (J.R.D.) created the rods using a previously described11 technique. Further, 10 g of piperacillin/tazobactam and 2 bags of Palacos bone cement (Zimmer, Warsaw, Indiana) were used for each rod. Intraoperative aspiration of bilateral knees showed no growth.
Postoperative anteroposterior radiographs of the right (A) and left (B) femurs showing placement of intramedullary antibiotic rods.
Postoperatively, intravenous levofloxacin was administered for 6 weeks per infectious disease consultation. On completion, a 2-week antibiotic holiday was allowed to verify that there were no changes in clinical symptoms or elevation of inflammatory markers. With no evidence of return of infection, the patient underwent bilateral rod removal and bone cultures, which continued to yield negative results at final 1-year follow-up. A large medial seroma was noted on the left femur, where the original open debridement had been performed, at 6-month follow-up. This resolved with aspiration and compression. Cultured fluid again yielded negative results, confirming that the infection had been cured.
Emphysematous osteomyelitis is a rare and often fatal musculoskeletal infection that requires surgical osseous debridement in conjunction with antibiotic treatment. Although use of the Reamer/Irrigator/Aspirator in managing chronic postoperative osteomyelitis of the long bones has been described,10,12–14 the current case had no identifiable source and a more subacute presentation. In addition, unlike previous reports that relied on variable clinical follow-up, the current case offers proof of cure with negative results on bone cultures and fluid aspiration.
Local antibiotic delivery with cement vehicles has been well described in the literature and has proven effective for cases of chronic osteomyelitis or open fractures.10,15 However, the current patient had no history of trauma or a known source, although her rheumatoid arthritis and chronic immunosuppression with prednisone certainly increased her risk for infection. In addition, she did not present with chronic osteomyelitis but rather a more subacute osteomyelitis, a process well described in the pediatric but not in the adult population.
Presuming the infection began at the onset of her pain, it remained relatively quiescent for 3 to 4 months. It occurred in the absence of an identifiable source, although the causative organism and the multifocal nature indicate a likely hematogenous etiology. Interestingly, she did not present acutely septic. It is possible that the patient's taking powerful immunosuppressants diminished the inflammatory response to the point that allowed an acute infection to become more subacute in nature. However, this is speculation and, to the authors' knowledge, has not been described in the literature.
The presence of intraosseous gas in the absence of an open injury should raise clinical suspicion for aggressive infection necessitating urgent surgical debridement. Additionally, debridement with the Reamer/Irrigator/Aspirator and insertion of intramedullary culture-specific antibiotics traditionally used for chronic osteomyelitis may be adapted for more subacute presentations.
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