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Dorsoplantar view. Findings include increased soft tissue density and volume affecting the second and third toes (these findings alone are not specific for soft tissue infection, however, and could represent any acute inflammatory process) and periostitis. Most bone infections seen in the foot are a result of direct extension from adjacent soft tissues (in contrast to hematogenous spread). Therefore, the first structure encountered along the bone surface is the periosteum. Pus accumulates under the thin periosteal tissue, lifts it up, and stimulates periosteal new bone formation. Arrows identify the subtle periosteal reaction along the lateral aspect of the third toe proximal phalanx shaft. Again, this finding alone is not specific for infection (periosteal reactions may be seen with healing fractures and tumors, for example); however, in the proper clinical setting, infection should be highly suspected. |
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Dorsoplantar view. This patient recently had excision of the second toe proximal phalanx head and entire middle phalanx. Radiographic findings in this case include increased soft tissue density and volume, and a periosteal reaction along the proximal phalanx shaft adjacent to the head resection site. Again, the periosteal reaction alone does not specify infection, but, clinically, pus was draining from the surgical incision site. |
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Medial oblique view. After penetrating the periosteum, infection then can cause erosion of the underlying cortex. The arrow identifies a subtle erosion along the lateral aspect of the fifth toe distal one-half diaphysis (medial oblique view). Radiographically, there is no gross evidence of osteomyelitis (involvement of cortical and medullary bone), but, since there is lag time before some radiographic features may be identified, osteomyelitis may be present clinically. Periostitis is not seen, which is the case in more aggressive infectious processes. Incidental finding includes synostosis of the fifth toe distal interphalangeal joint. |
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Medial oblique view. Note the abnormal form and fragmentation of the fourth toe proximal phalanx. This finding is called osteolysis, and is characteristic of osteomyelitis in the proper clinical setting. The bone fragments are known as sequestra (dead/necrotic bone fragments floating in pus). Incidental findings include diffuse vessel calcification. |
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Dorsoplantar view. Significant osteolysis with accompanying increased soft tissue density and volume involve the second toe. No surgery has yet been performed; all loss of bone is a result of an extremely active bone infection. All that remains is the proximal half of the proximal phalanx; identify the rarefaction (loss of bone density) in the remaining proximal phalanx. The bone fragments represent sequestrum. (The third and fourth toe distal phalanges cannot be identified due to severe contractures of the toes and subsequent superimposition.) |
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Dorsoplantar view of fifth ray. Findings include severe osteolysis of all phalanges and the fifth metatarsal head; periostitis along the medial aspect of the metatarsal diaphysis; a soft tissue defect (ulcer) lateral to where the fifth MTPJ would normally be found. |
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| Dorsoplantar views. This patient initially presented with bunion pain clinically. Before radiographs were ordered, the patient was diagnosed and treated for bursitis. The radiographs were performed prior to discharging the patient and were not reviewed. In the left radiograph, note the well-defined air-like density in the soft tissues adjacent to the first metatarsal head (arrow). If this were identified initially, appropriate treatment could have been rendered. However, it was not identified at that visit, and the patient returned two months later for her follow-up appointment. Compare this radiograph to the one on the right; the air-like density has disappeared, but there is an increased soft tissue density and volume adjacent to the first metatarsal head, and an ill-defined erosion with rarefaction can be identified in the head. Fortunately, this infection was not very aggressive; the pus was aspirated from the area, and the patient was placed on appropriate antibiotic therapy. |
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| Dorsoplantar and lateral views. Note the air (gas) in the soft tissues, best seen in the lateral view (arrows). The geographic decreased densities seen in the hallux proximal phalanx (dorsoplantar view) are superimposed pockets of gas in the soft tissue. Causes of air-like densities in soft tissue includes gas-forming bacteria, injection of air into the soft tissues, and failure to remove (or, "milk") air out of the operative site prior to closure. |
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| Medial oblique and lateral views. Note the diffuse air-like densities throughout the entire foot, especially along the sole of the foot in the lateral view. |
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| Medial oblique (A) and lateral oblique (B) views. Osteomyelitis first involved the hallux proximal phalanx head which was previously removed surgically. However, the infection spread to the adjacent distal phalanx, and has involved the proximal phalanx diaphysis. Findings include increased soft tissue density and volume (also note the soft tissue defect –ulcer– along the plantar-lateral aspect of the hallux interphalangeal joint in the lateral oblique view, sequestra, rarefaction and osteolysis of the distal phalanx, and periostitis (subtle) of the proximal phalanx diaphysis in the medial oblique view. |
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Dorsoplantar view. A geographic, lucent lesion is seen in the fifth metatarsal distal one-third diaphysis, surrounded by diffuse sclerosis. Remodeled periosteal bone apposition is seen along the adjacent medial diaphysis. Bone abscess is frequently secondary to hematogenous spread from another site elsewhere in the body. |
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AP view, distal tibia. This patient has had chronic osteomyelitis of the distal tibia for many years (it is rarely seen in the foot). The shape of the distal tibial is deformed due to chronic osseous remodeling about the infection; the outer remodeled "collar" of the tibia is known as involucrum (new bone surrounding a chronic abscess). Also identify the somewhat geographic linear lucency in the mid-tibia (arrow); this is a cloaca, an opening in the involucrum where pus drains out of the bone. |
© Copyright 1998, Robert A. Christman, D.P.M.
These articles and figures may not be published, reposted, or redistributed without permission from Dr. Christman.
This page was updated May 5, 1998.
