Sunday, September 14, 2008

Heart Surgeons, Abscesses, and Lytic Lesions

Michael DeBakey M.D. died at the age of in July 2008. He was best known as a pioneering heart surgeon, operating on celebrities and commoners alike, saving thousands of lives.

Debakey was a creative surgeon even early in his career. With his mentor Alton Ochsner, he devised a new way to drain subphrenic abscesses, through a transthoracic approach. An abscess is a collection of pus (infected fluid), and is typically found within the soft tissues. In some cases, however, abscesses can also occur within the bone.

In 1832 the surgeon B.C. Brodie described three cases of a chronic abscess within the tibia:

The patients were young adults, and each presented with chronic tibial pain and swelling. Brodie was a good writer, and his description is compelling:

"The lower extremity of the left tibia was considerably enlarged; the skin covering it was tense, and adhered closely to the parts below. The patient complained of a constant aching pain, which he referred to the enlarged bone. Once in two or three weeks there was an attack of pain more severe than usual, during which his sufferings were excruciating, lasting several hours, and sometimes one or two days, and rendering him altogether incapable of following his usual occupations. The pain was described as shooting or throbbing, worse during the night, and attended with such exquisite tenderness of the parts in the neighborhood of the ankle that the slightest touch was intolerable."

Recently, I saw a case of a 12 year-old girl with a lytic lesion in the tibia. Of course, the clinical history on the prescription was a little less eloquent than the description above: "Pain, MRI ankle".

Sagittal T1-weighted and STIR images depict an oval lesion (red arrows) in the distal tibial metaphysis. The lesion crosses the physis (yellow arrow), to involve the epiphysis as well. There is a great deal of marrow edema surrounding the lesion. A close-up of the lesion reveals that the lesion is heterogeneous, with a rind of T2 hyperintensity representing granulation tissue (red arrow) surrounding a relatively hypointense core (blue arrow):

The appearance is highly suggestive of a chronic bone abscess (Brodie's abscess), which was confirmed at surgery. In some cases, the lesion can be difficult to distinguish from a tumor, such as osteoid osteoma. Conventional radiographs and CT are often helpful, and depict a lytic lesion with surrounding sclerosis. This sclerotic response typically has a sharp interface with the lesion, but merges gradually with the surrounding bone (Musculoskeletal Imaging: A Teaching File. Felix S. Chew, Catherine C. Roberts; Lippincott Williams & Wilkins, 2005)

A Brodie's abscess develops when osteomyelitis is contained by the host immune response, but is not cured. The infection is walled off, but remains active. The lesion usually is within the metaphysis, but can occur anywhere. When it occurs in the epiphysis, it can be mistaken for a chondroblastoma.

Nearly 200 years have flashed by since Brodie's original description, but chronic bone abscess remains an important medical diagnosis. These lesions are eminently treatable, once the diagnosis is established.

Vic David MD

1 comment:

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