Tuberculous osteomyelitis of the tibia

Case contributed by Dr Seamus O'Flaherty

Presentation

Low-grade fever and pain in right leg for several weeks. The patient is an immigrant from the subcontinent. CRP 57.

Patient Data

Age: 35 years
Gender: Male

Multiple overlapping radiolucent medullary lesions in the proximal right tibia meta-diaphyseal region.

Some edges of the complex lesion are well-demarcated, however, others are poorly defined. There is endosteal scalloping and periosteal thickening toward the distal end of the lesion, as well as density in the adjacent medial leg soft tissues, which are indications of an aggressive process. 

No pathological fracture. 

Bone Scan

Nuclear medicine

Abnormal intense Tc99m radiotracer uptake in the right proximal tibia over an 11cm segment. No abnormal tracer uptake elsewhere in the body. 

An 11 x 3 x 2 cm right proximal tibial lesion is identified in the metadiaphyseal region. It is centered in the medullary cavity and demonstrates thick rim enhancement on T1 contrast sequences and central low T1/high T2 signal. The margins of the lesion are irregular and lobulated, with foci of endosteal scalloping. There is a breach in the anterior tibial cortex best appreciated on the sagittal T2 reconstructions, which communicates with a similar appearing rim enhancing lesion in the anteromedial leg soft tissues, measuring 4.6x1x7.5cm. Extensive overlying subcutaneous edema.

The muscles in the leg appear unremarkable and intact. Unremarkable appearances of the neurovascular bundle. Normal appearances of the fibula and distal tibia.

CONCLUSION: Appearances are consistent with osteomyelitis of the proximal tibia. A cloaca in the anterior tibial cortex drains into a soft tissue collection in the anteromedial leg.

Case Discussion

This male patient was born in India and presented with indolent right leg pain. Initially, he stated the pain had been for several weeks. Upon further questioning, it was revealed he had intermittent leg pain for several months prior to presentation. 

The imaging findings are characteristic of osteomyelitis. This patient underwent an ultrasound-guided aspirate of the soft tissue collection, which grew mycobacterium tuberculosis. 

The clues are in the history and demographics. The patient's name and presentation raise suspicion of tuberculosis, which is endemic in India. 

The radiographic findings demonstrate an aggressive lesion in the typical location of osteomyelitis; however, other aggressive processes such as cancer need to be excluded by bone scan.

The bone scan confirms there is a solitary lesion in the right proximal tibia, which can only be a focal infective process or primary osseous malignancy. 

The MRI confirms osteomyelitis. There is pus within the bone, which has escaped into the soft tissues via a cloaca in the anterior tibial cortex. 

Notice the extent of the infection in the tibia. If this were pyogenic osteomyelitis the patient would be more systemically unwell and with more severe pain. Often, tuberculosis osteomyelitis is a more indolent process with only mild pain and/or systemic symptoms despite extensive disease.

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