Denouement

Continued from p. 881. The patient was found to have clay-shoveler’s fracture, a fracture of the spinous process of the first thoracic vertebra (T1), spinous process, and associated bilateral erector spinae muscle abscesses (pyomyositis). The radiograph of the cervical spine demonstrated an avulsion fracture of the spinous process of T1 (Fig. 1), an entity known as clay-shoveler’s fracture. This correlated with the area of tenderness to palpation on examination; however, it did not explain his fevers. The patient therefore underwent a magnetic resonance imaging of the spine (Fig. 2A and 2B), which revealed increased T2 signal and gadolinium contrast enhancement of the right and left erector spinae musculature and central areas of nonenhancement from T1 to T4 bilaterally, consistent with intramuscular erector spinae abscesses. The following day, ultrasound-guided percutaneous drainage of the abscesses was performed. A few white blood cells and moderate Gram-positive cocci in pairs and clusters were noted on the Gram stain. Intravenous (IV) vancomycin (1000 mg every 8 hours) was initiated. The culture grew methicillin-susceptible Staphylococcus aureus, and antibiotic therapy was changed to cefazolin (25 mg/kg/dose IV every 8 hours). The patient’s fever resolved, and his C-reactive protein decreased to 5.2 mg/dL by the time of discharge 4 days later. He received 2 weeks of IV cefazolin and then completed 2 additional weeks of oral cefadroxil (1000 mg twice daily). By the end of antibiotic therapy, he was asymptomatic, and the inflammatory markers had normalized. A follow-up radiograph of the cervical spine 2 weeks later showed continued healing of the avulsion fracture of the T1 spinous process.FIGURE 1: Lateral radiograph of the cervical spine. A small ossific density is seen dorsal to the tip of the T1 spinous process consistent with an avulsion fracture. Black arrow indicates avulsed tip of T1 spinous process; SP, spinous process of T1; and vertebra T1, vertebral body of T1.FIGURE 2: A) A 1.5 Tesla magnetic resonance image of the cervical and thoracic spine. Axial postgadolinium T1-weighted image with fat suppression demonstrates central nonenhancing areas within the erector spinae muscles, especially on the left, surrounded by contrast enhancement in both erector spinae muscles consistent with intramuscular abscesses. Black arrows indicate left erector spinae intramuscular abscess; star, inflammatory gadolinium contrast enhancement of the right erector spinae muscle; SC, spinal cord; and T1, T1 vertebral body. B) Left parasagittal T1-weighted post–contrast-enhanced magnetic resonance image showing the longitudinal extent of the intramuscular abscess (white star).A clay-shoveler’s fracture1 is an avulsion fracture of a lower cervical (C6-7) or upper T1 spinous process. This term originated in the 1930s in reference to Australian workers who sustained this injury from shoveling heavy clay soil, particularly when attempting to throw clay stuck to the shovel. The mechanism of injury is believed to be due to stress on the spinous processes by direct muscle forces or the result of reflex muscle contracture. A fracture of this nature also can result from direct injury or hyperextension and hyperflexion of the neck.2 Case reports2–5 have described these fractures in association with golfing, playing Wii games and a variety of accidents. Venable et al6 reported that these fractures can result from the repetitive stress of manual labor rather than from acute injury. Clay-shoveler’s fractures, regardless of the mechanism of injury, are considered stable and treated symptomatically. Our patient denied any specific trauma and did not recall any events that elicited acute pain. However, his daily farming responsibilities included cleaning chicken pens and shoveling hay, activities that can be associated with this type of fracture. The mechanism of formation of our patient’s bilateral erector spinae muscle abscesses was less clear, but we suspect the fracture may have led to hematoma formation and secondary infection with S. aureus. Pyomyositis is more often reported in tropical areas,7 although it is becoming increasingly recognized in temperate climates as well.8,9 Most cases of pyomyositis (infection of the skeletal muscle) involve the large muscle groups of the legs and pelvic girdle.8 Infection can be multifocal, and muscle abscesses frequently occur without a clear portal of entry. Although the exact pathogenesis of pyomyositis is unclear, it is often believed that infection develops after muscle injury at a time of transient bacteremia.9,10S. aureus is the bacterial pathogen most often isolated in North America,8,11 and is responsible for about two-thirds of cases, with the majority due to methicillin-susceptible organisms. In one review,8 older patients and those with underlying diseases had a higher incidence of Gram-negative infections. Predisposing risk factors for the development of pyomyositis include diabetes mellitus, malignancy, rheumatologic disease, cirrhosis, renal insufficiency, lung disease, sickle cell disease and aplastic anemia, as well as HIV infection. As was true in our teen’s case, the presentation of pyomyositis is variable, and diagnosis may be difficult and delayed.7 The early signs of illness, including muscle pain and cramping, are often nonspecific. As an abscess develops, fever occurs and the muscle becomes exquisitely tender.11 However, the classic signs of abscess formation such as erythema and fluctuance may be absent. If left untreated, bacteremia, septic shock and endocarditis can develop. Our patient’s muscle abscesses were of particular concern because of their potential to spread contiguously and cause a spinal epidural abscess. Overall, mortality is rare but increased in patients with underlying medical conditions.12 Management of pyomyositis usually requires both antibiotics and abscess drainage.8–11 Initial antibiotic therapy should target S. aureus, as well as Gram-negative bacteria if predisposing factors are present. Culture results should direct the definitive therapy. There are no established guidelines for duration of antibiotics, but generally therapy should be continued until symptoms have resolved and inflammatory markers have normalized. To our knowledge, this is the first report of a case of bilateral erector spinae muscle abscesses associated with a clay-shoveler’s fracture. A careful review of our teen’s occupational history provided the clue to explain this injury, although further imaging was required to elucidate the source of fever. Pyomyositis is a rare but potentially serious infection; this case should remind clinicians to strongly consider pyomyositis in a patient with fever and focal musculoskeletal tenderness.