Pyogenic spondylodiskitis - A radiologic/pathologic and culture correlation study

Background.-Intervertebral disk tissue is resistant to hematogenous infecti on because of its avascularity. However, spondylodiskitis is being diagnose d with increasing frequency because of advancement in magnetic resonance im aging technology. There is a dearth of information regarding the bacteriolo gy, histomorphologic features, and radiopathologic correlation of spondylod iskitis. Design.-The study population consisted of 20 patients diagnosed as having s pondylodiskitis by magnetic resonance imaging with and without gadolinium 6 7 enhancement and bone scans with technetium Tc 99m or gallium citrate Ga 6 7. Twenty-seven biopsy and debridement specimens were obtained from these p atients. The specimens were cultured for microorganisms and also processed for histopathologic testing. Tissue sections were examined with hematoxylin -eosin and stains for infectious agents (Gomori's methenamine-silver, Gram, and Ziehl-Neelsen stains). Results.-Where intervertebral disk tissue was present (23 of 27 cases), the morphologic changes included vascularization (with or without granulation tissue), myxoid degeneration, and necrosis. Chronic osteomyelitis was prese nt in all 27 specimens and was associated with acute osteomyelitis in 7 cas es (25%). Twenty-one of 27 cases had positive culture results (mostly pyoge nic bacteria), but special stains revealed microorganisms in sections of th e disk in only 4 cases (3 cases with gram-positive cocci and 1 with yeast c onsistent with Blastomyces). Florid acute inflammation was present in all t he 4 cases. Conclusion.-Histopathologic features of acute spondylodiskitis include vasc ular proliferation, myxoid degeneration, and necrosis of the disk tissue wi th adjacent chronic osteomyelitis. Acute inflammation is variable and when florid is usually associated with identifiable organisms on histologic exam ination. At biopsy, tissue should be submitted for culture, since culture h as a high sensitivity and specificity for detecting the etiologic organism.