Epiphyseal Photopenia Associated with Metaphyseal Osteomyelitis and Subperiosteal Abscess

Patrice K. Rehm and John Delahay Division ofNuclear Medicine, Departments ofRadiology and Orthopedic Surgery, Georgetown University Hospital, Washington, DC

fevers and knee pain necessitating surgical exploration. An abscess We present a case of metaphysealosteomyelitis in a child where was present, with a small amount of purulence within the bone, as bone scintigraphy demonstrated photopenia of the distal femoral well as copious purulent material beneaththe metaphysealperios epiphysis in the absence of infection of the epiphysis or the joint space. A subsequent bone scan demonstrated evolution of the teum medially, neither being under pressure. No effusion or vascular compromise of the epiphysis due to the metaphyseal purulence was found within the joint or the epiphysis. Copious osteomyelitis complicated by subperiosteal abscess. We discuss irrigation was performed and drains were left in place. Antibiotic the mechanisms and implications of photopenia in the setting of therapy was changed to intravenous penicillin. Gram stain and acute bone and joint infection. cultures of the purulent sitessubsequentlywere positive for Group Key Words epiphyseal photopenia; metaphyseal osteomyelitis; A strep and the epiphysis andjoint sites were negative. subperiostealabscess; bone scintigraphy Becauseof spikingfeversandcontinuedkneepain, the patient J Nuci Med 1998 391084-1086 underwent a second surgical exploration and debridement on the fifth hospital day. Purulent material was found within the knee joint and within the metaphysis, neither being under pressure. Photopeniaonbonescintigraphyintheclinicalsettingofacute The child defervesced and completed a 6-wk course of intrave bone and joint infection is well recognized. It may occur by a nous ceftriaxone. A three-phase bone scan 1 mo after onset variety of mechanisms, all related to alterations in blood flow revealed increased activity of the distal femoral epiphysis in and delivery ofthe radiotracer secondary to infection. We report addition to the metaphysis(Fig. 2). The patient subsequentlydid a case of a previously healthy child whose metaphyseal osteo well and had no joint or growth disturbance. myelitis ofthe distal femur resulted in epiphyseal photopenia on bone scintigraphy in the absence of infection ofthe epiphysis or knee joint. DISCUSSION While findings on the three-phase bone scan were indicative The normal circulation to a growing tubular bone such as the of osteomyelitis of the distal femoral metaphysis, there was the knee includes distinct epiphyseal and metaphyseal arteries. The unusual associated finding of decreased uptake in the distal growth plate lacks vascular connections between 1yr ofage and femoral epiphysis. The complicated clinical course, including puberty (Fig. 3). In children, vascular anatomy predisposes the surgical interventions, subsequent development of septic arthri metaphysis to infection. While up to 30% of cases of acute tis and follow-up bone scan are described. The mechanisms and osteomyelitis in children occur at sites other than the metaph implications of photopenia on bone scintigraphy in the setting ysis, these metaphyseal-equivalent regions occur adjacent to of acute bone and joint infection are discussed. cartilage and demonstrate similar vascular anatomy. Metaphy seal-equivalent sites include those adjacent to apophyseal growth plates, articular cartilage or fibrocartilage (1). As in this CASE REPORT patient, the epiphysis typically is not involved by primary A previously healthy 4-yr-old boy was admitted for a 6-day infection or by extension from the metaphysis (2). The effec history of vagueright distal femoral pain and low-grade fever, and tiveness of the physis as a barrier to the spread of infection is a 2-day history of refusal to bear weight. The patient had a confirmed by the rarity of contiguous extension to the epiphy leukocytosis with left shift, elevatederythrocyte sedimentationrate sis, destruction of the growth plate or growth disturbances. The and swelling and erythema of the right leg from the knee to the infection spreads from its metaphyseal origin by way of the ankle. Radiographofthe kneewas unrevealing(Fig. lA). The right Haversian system to the metaphyseal subperiosteal space. The knee was aspirated of serosanguinousnonpurulent fluid. Gram periosteum may be elevated, and it may rupture. When the stain and cultures were negative for an infectious agent. After metaphysis is intra-articular, as in the shoulder, hip, knee and blood cultures were obtained, intravenous nafcillin was started for ankle, suppurative arthritis results. presumed osteomyelitis. Within 24 hr of admission, a three-phase While most frequently demonstrated as increased radiotracer 99mTcdiphosphonate bone scan was performed. uptake, acute bone and joint infection may appear normal or The bone scan demonstrated findings indicative of osteomyelitis photopenic on bone scintigraphy. The spectrum of bone scan of the distal metaphysis. In addition, the soft-tissue phase and findings in osteomyelitis reflects the pathophysiologic pro delayed images demonstrated photopenia of the distal epiphysis cesses. Early in osteomyelitis, edema and increased local (Fig. lB—D).Blood cultures subsequently grew Group A strepto pressure may decrease the blood flow and tracer uptake. cocci. Subsequent local hyperemia causes increased radiotracer up On the third hospital day, the patient continued to have spiking take, with an intervening normal scan appearance. The less common, but well-recognized, pattern of photopenia Received Jan. 27, 1997; revision accepted Aug. 14, 1997. in infection may occur by a variety of mechanisms, all related For correspondence or reprints contact: Patrice K Rehm, MD, Nuclear Med@ine, German 2005, Georgetown University Hospital, 3800 Reservoir Road, NW, Washing to alterations in blood flow and radiotracer delivery. Edema, ton, DC 20007-2113. subperiosteal pus and intraosseus pus can elevate intraosseous

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FiGURE 1. (A) Normal anterior radio graph of right knee. (B) Angkgraphk@ phasedemonstrateshyperemiaof right thigh,morepronouncedindistalmetaph yse@region(arrows).(C)Blood-poolim age demonstratesincreasedactivityin rightdistalmetaphysisand physis.There isrelativephotopeniaofrightdistalepiph ysiscomparedto the left,mostevident laterally(arrowhead).(D)Delayedimage demonstrates photopeniaofdetal epaph ysis (arrowhead)more pronouncedin central portion.There is normaluptake in distal metaphysis. 4* pressure. Infection spreading throughout the cortex may com flow to the epiphysis may be compromised by metaphyseal promise or thrombose the nutrient artery as well as lead to infection without joint effusion by edema of the overlying subperiosteal abscess formation. At a later stage, prolonged synovium compressing vessels that supply the head. A subpe ischemia may produce photopenia representing infarction. riosteal abscessbulging into the joint can stretch and compress True photopenia must be distinguished from apparent pho the epiphyseal arteries and veins within the synovium. Because topenia that may result from juxtaposition of bones of differing of potential compromise ofthe epiphyseal blood flow by any of osteoblastic activity such as an epiphysis compared to the these mechanisms, surgical drainage of the proximal metaphy adjacent physis. Comparison to the contraleral side as well as to sis of the humerus or femur as well as the joint has been the proximal tibial epiphyses confirms the presence of true recommended (8). Diagnostic maneuvers such as saline wash photopenia of the distal epiphysis in this patient. ings or arthrography during arthrocentesis can produce transient Case reports and seriesreporting photopenic osteomyelitis in photopenia by increasing pressure in the joint if radiotracer children describe involvement of long bones, the head of the injection follows thejoint procedure within 1.5 hr (9). However, femur or humerus, as well as small and flat bones (3). Previous a similar pattern of vascular compromise and associated pho authors have noted an association between photopenia and topenia has not been reported for the distal femur. subperiosteal or intraosseous abscess(4), which can necessitate Abnormalities on the early phases of the bone scan can prompt drainage to decrease morbidity (5). In patients with indicate osteomyelitis when the delayed images are normal (10) photopenic osteomyelitis, CT and MRI have been suggestedfor as demonstrated in the metaphysis of this patient. The osteo identifying coexisting abscess requiring drainage (6). Some authors have suggested an association between photopenic myelitis originated in the distal femoral metaphysis, as mdi osteomyelitis and a poor outcome. The impairment of blood cated by the findings on the three-phase bone scan and flow and decreased antibiotic delivery may increase the mor confirmed by subsequent surgery. Epiphyseal osteomyelitis bidity and risk for sequestrum formation. Photopenia may extending from the metaphysis could be postulated as an signal the need for aggressive surgical management ( 7). explanation for the photopenia on the initial scan, although this Photopenia of the intracapsular bone, such as in the shoulder occurs rarely. However, cultures obtained at surgery before and hip, can occur in acute infection and has been attributed to antibiotic administration indicated that infection had not spread several mechanisms other than epiphyseal osteomyelitis. Sterile to the epiphysis or the joint. The bystander photopenia of the or purulent joint fluid can result in reduced blood flow and epiphysis indicated vascular compromise by subperiosteal and tracer uptake of the proximal femoral and humeral epiphyses intraosseous abscessof the adjacent metaphysis. The evolution (6). Reductions in intracapsular pressure through aspiration or from bone ischemia and infarction to healing is depicted by the drainage can restore blood flow and tracer uptake (7). Blood findings in the epiphysis on sequential bone scans.

EPIPHYSEAL PHOTOPENIA ASSOCIATED WITH METAPHYSEAL OSTEOMYELITIS •Rehm and Delahay 1085 A

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metaphyseal subperiosteal abscess may lead to appropriate CONCLUSION surgical management and decreased morbidity (7, 11). It is important to recognize photopenia as a manifestation of osteomyelitis and to alert clinicians to vascular compromise and ACKNOWLEDGMENTS to the frequent coexistence of intraosseous or subperiosteal We thank Boris A. Karaman, MD, for his editorial suggestions. abscess.Appreciation of bystander photopenia as a presentation REFERENCES of vascular compromise of the distal femoral epiphysis due to 1. Nixon GW. Hematogenousosteomyclitis of metaphyseal-equivalentlocation. Am J Roentgenol1978;130:123—l29. 2. Rosenbaum DM, Blumbagen ID. Acute epiphyseal osteomyelitis in children. Radio! ogy l985;15:89—92. 3. Rehm pic Aaron AD. Extensive photopenic osteomyelitis.JNuc! Med 1996;37:1676— 1678. 4. Allwright SJ, Miller UH, Gilsanz V. Subperiosteal abscess in children: scintigraphic appearance. Radiology l99l;l79:725—729. 5. HamdanI, Asha M, Malloub A, Usta H, Talab Y, Ahmad M. Technetiumbone scintigraphy in the diagnosis of osteomyelitis in children. Pediatr Infect f)is J 1987;6:529—532. 6. MurrayIP.Photopeniain skeletalscintigraphyof suspectedboneandjoint infection. Clin Nuc! Med 1982;7:l3—20. 7. Kloiber R, Paviosky W, Portner 0, Gartke K. Bone scintigraphy of hip joint effusions FiGURE3. Diagramof arterialsup in children. Am J Roenigenol 1983;140:995—998. ply to knee of child. C = circulus 8. Mortensson W, Nybonde T. lschemia of the childhood femoral and humeral head articulivasculosus(Huntervascular epiphyses after osteomyelitis. A hypothesis on its cause. Ada Radio! Diagn (Stockh) circle);E = epphyseal arteries;P = 1984;25:269—272. physis; M = metaph@ arter@ 9. Mandell GA, Harcke HI, Bowen JR. Sharkey CA. Transient photopenia ofthe femoral head after arthrography. Clin Nucl Med 1989;14:397—404. N = branchesof nutrientartery. 10. Gilday DL. Problems in the scintigraphic detection of osteomyelitis. Radiology Reprinted with permlasion from l980;l35:79l. Rosenbaum DM, Blumhagen JD. I 1. Howie DW, Savage JP, Wilson 1G. Paterson D. The technetium phosphate bone scan Acute epiphyseal osteomyelitis in in the diagnosis of osteomyelitis in childhood. J Bone Joint Surg Am 1983;65:43l— children.Radiology1985;15:89-92. 437.

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