Clinically osteomyelitis can be divided into two general categories, osteomyelitis secondary to hematogenous spread or osteomyelitis secondary to involvement of the bone by a contiguous soft tissue infection.1 Furthermore, these categories can be subdivided based upon the presence or absence of peripheral vascular disease and/or prosthetic devices. This distinction is clinically important since contiguous-focus osteomyelitis tends to have a poorer outcome, with relapse rates reported as high as 50%.2
Osteomyelitis of the pelvis has reported incidence of between 2-11% with the ilium is the most frequent site of involvement.3 Etiologies include gastrointestinal surgery and trauma, as were present in this case, as well as urinary tract infections, Crohn's disease and pelvic surgery. The bacterial organism most frequently encountered in these cases is Staphylococcus aureus.
The development of acute osteomyelitis of the axial skeleton occurs infrequently. A minority of these cases develop secondary to trauma with even a smaller percentage being related to civilian gunshot wounds so there is little in the literature regarding the clinical course and management of such infections. Maler et al,4 in a retrospective study of pyogenic axial osteomyelitis following civilian gunshot wounds, reported that 75% of the patients in whom axial osteomyelitis developed had contiguous soft tissue abscesses, a situation similar to the present case. Other factors such as the presence of gastrointestinal spillage/injury, shock, or whether or not surgical debridement was performed were not statistically significant in determining the development of osteomyelitis.
Anaerobic osteomyelitis, while relatively rare with slightly greater than 800 cases reported in the literature, has been increasingly recognized in the recent past with an incidence ranging from <1% to 22% of reported cases.5,6,7 Whether this increase represents a changing of the natural microbiology of the disease process or is simply a reflection of improved sample collection, sample transportation, laboratory cultivation, and identification methods for anaerobic organisms is unclear. A recent Veterans Administration Hospital study reported isolating 1.7 anaerobic and 0.5 aerobic/facultative aerobic organisms per specimen collected over a 10 year period with 33% of osteomyelitis containing mixed aerobic and anaerobic infections.5 The recognition of mixed infections is clinically important as these infections may have treatment failure rates which are in excess of three times that of pure aerobic infections.8
Group C ß-hemolytic Streptococci, although a frequent cause of animal infections, rarely cause serious human infections. When pathogenic in humans this organism can cause a myriad of infections including pharyngitis, bacteremia, soft tissue abscesses, puerperal infections, endocarditis, pneumonia, meningitis and urinary tract infections.9 These organisms have rarely been associated with osteomyelitis, 9-13making it difficult to predict the biologic behavior and the clinical progression of this disease entity.
Contributed by Scott Kulich, MD PhD and William A. Pasculle, ScD