| May 2005 Case of the Month |
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Compiled By: William Passodelis, D.O.
History: 12 year old male with ongoing ankle pain and swelling, concern for osteomyelitis versus septic arthritis.
Study: MRI Left ankle, Coronal and Sagittal T1 and T2 sequence images included here.
Findings:
Diffuse heterogeneous marrow signal involving the entirety of the imaged tibia. Central extension to involve the epiphysis is noted. Periosteal thickening is also present.
Minimal tibiotalar joint fluid. The tendons and ligaments are intact.
Diagnosis: Chronic Osteomyelitis of the Tibia.
Discussion: Diffuse and patchy ill-defined increased signal in T2 and STIR images, involving the medullary bone indicates marrow involvement. A peripheral rim of low signal intensity, as present in this case, represents reactive bone and demarcates the foci of involvement. This is consistent with a long standing process. Alteration of signal intensity is seen at sites of cortical transgression or periosteal reaction. Due to involvement with osteomyelitis, in children, premature growth plate closure may occur.
Early in the process, a stellate pattern of signal abnormality may occur, especially with staphylococcal osteomyelitis. This may simulate a stress fracture. Infectious soft tissue and osseous involvement can be successfully identified using a combination of T1, T2, Proton Density, and STIR imaging sequences. Fat suppressed, contrast enhanced MR is more sensitive than scintigraphy and more specific than non-enhanced MR for the diagnosis. Early on, inflammation or cellulitis and bone edema will represent osteomyelitis until proven otherwise.
Hematogenous osteomyelitis often involves areas adjacent to cartilage and areas bordering physeal plates and STIR as well as fat suppressed T2 FSE images increase sensitivity for identifying these areas.
Differential diagnosis in this case, given the appropriate setting and history, would include eosinophilic granuloma . Earlier in the process, differential would also include septic arthritis, bone contusion, stress fracture and changes related to sickle cell disease.
In this case it would be necessary to further image the tibia to elucidate the full extent of involvement, as all of the portion of the tibia included is involved.
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References:
Stephen J. Pomeranz, MD Gamuts and Pearls in MRI and Orthopedics. MRI-EFI Publications, Cincinnati, OH 1997 David W. Stoller, MD, FACR Magnetic Resonance Imaging in Orthopedics and Sports Medicine.
Lippincott Williams and Wilkins Co. Philadelphia, PA 1997
Narvaez, MD, Jose A., Narvaez, MD, Javier, Ortega, MD, Raul, et al, Painful Heel: MR Imaging Findings, Radiographics. 2000:20:333-352.
David W. Stoller, MD, FACR, Phillip J. Turman, MD, Miriam A. Bredella, MD, Diagnostic Imaging ORTHOPAEDICS, Amirsys Inc. Salt Lake City, UT 2004 | |
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