CASE 4

By: Dr. M. Salman and Dr. Shankar Raja

HISTORY: 33-year-old male with history of osteomyelitis of right distal femur treated in outside facility was referred for further management. Following prolonged antibiotic therapy. Follow-up CT was obtained.

What are the findings on baseline and follow up CT?

Baseline CT showed cortical sequestrum; follow-up CT demonstrated progression with sinus formation and soft tissue collection beside persistent heterogeneous marrow.

Subsequently ultrasound guided aspiration of soft tissue collection was performed.

Despite, continued therapy and non-responsiveness, hence an MRI and PET-CT was obtained for further evaluation.

What are your findings on MRI?

What is the differential diagnosis?

FINDINGS:

MRI showed sinus tract communicating the intraosseous collection and large soft tissue collection in an active chronic suppurative osteomyelitis.

PET-CT images demonstrating multiple sinus tract corresponding to findings on multiparametric MRI, in addition to tubular tracking along the medial aspect of femoral shaft.

3D- Rendered CT demonstrates sinus tract opening in cortex of mid third right femoral shaft (red arrow).

MIP-PET shows origin of sinus (red arrow) and in addition multiple soft tissue sinus tracts (blue arrow).

DIFFERENTIAL DIAGNOSIS:

The prototype conditions that may present with a bony sequestrum are osteomyelitis and skeletal tuberculosis.

Other conditions such as radiation necrosis, eosinophilic granuloma, metastatic carcinoma, primary lymphoma of bone, aggressive fibrous tumors may also manifest as osteolytic lesions containing a sequestrum.

DIAGNOSIS:

Chronic suppurative osteomyelitis.

PEARLS AND DISCUSSION:

PET is excellent in showing tortuous sinus tracts   uncommonly occult on CT and fistula.

PET is excellent tool for evaluating early response to therapy.

PET is also helpful for confirmatory targeted biopsies in equivocal cases.

FURTHER READING:

1. Carek PJ, Dickerson LM, Sack JL. Diagnosis and management of osteomyelitis. Am Fam Physician. 2001 Jun 15. 63(12):2413-20.

2. Kruskal JB. Can USPIO-enhanced spinal MR imaging help distinguish acute infectious osteomyelitis from chronic infectious and inflammatory processes? Radiology. 2008 Jul. 248(1):1-3.