Osteomyelitis/septic arthritis foot - diabetic

Case contributed by Dr Patsy Robertson

Presentation

Type 2 diabetic with swollen, painful ankle and left leg cellulitis.

Patient Data

Age: 52
Gender: Male

X-RAY LEFT FOOT

The bones are normal in appearance and alignment with no evidence of Charcot's or septic arthritis. There is soft tissue swelling over the dorsum of the forefoot.

 

 

Bone scan foot

RADIOPHARMACEUTICAL - 99mTc MDP: 871 MBq

CLINICAL INDICATION

TECHNICAL PROCEDURE AND RESULTS

A triple phase bone scan of the feet was performed.

Dynamic flow and blood pool images (not available) show marked focal hyperaemia of the left midfoot.

Delayed static images and low dose SPECT/CT show markedly increased osteoblastic activity in the left medial cuneiform, and the left tarsometatarsal joints, particularly laterally.

OVERALL IMPRESSION

The scintigraphic appearances favour osteomyelitis of the left medial cuneiform with septic arthritis in the left tarsometatarsal joints.

No bone abnormality is seen in the tibia or fibula on the left.

 

MRI LEFT FOOT

Extensive tarsal abnormality centered in the intermediate cuneiform, demonstrating bony destruction of the cuneiform as well as base and body of the second metatarsal, consistent with septic arthritis and osteomyelitis. Marrow signal changes in the adjacent medial and lateral cuneiforms as well as the 3rd metatarsal base are present, potentially reactive or early osteomyelitis.

There is a 2cm collection at the plantar aspect of the 2nd tarsometatarsal, which appears extending from the joint space with further peripherally enhancing multiloculated foci at the dorsolateral aspect of midfoot, with surrounding enhancing soft tissue, which also could represent a second collection in continuity with the infected joint.

Ankle joint and hindfoot is normal.

Conclusion:

Intermediate cuneiform and second metatarsal septic/ arthritis and established osteomyelitis with either reactive or early osteomyelitic changes in surrounding bones.

Associated soft tissue abscesses.

 

Indium labelled white cell scan

RADIOPHARMACEUTICAL:  99mTc WBC, 600 MBq

CLINICAL INDICATION
52 year old male with ongoing sepsis sepsis secondary to ? septic arthritis
despite antibiotics for assessment.  Bone scan on 6/8/14 suggests
osteomyelitis in the left medial cuneiform and septic arthritis in the left
tarsometatarsal joints.  

TECHNICAL PROCEDURE AND RESULTS

Planar and SPECT/CT images were performed 4 hours after intravenous
administration of 600 MBq 99mTc labelled WBC.  

Moderately increased tracer uptake is noted in the left midfoot.
Correlation with SPECT/CT demonstrates increased tracer uptake in the left
medial cuneiform and 3-5th tarsometatarsal joints, similar to that seen on
the bone scan of last week.

More significant tracer uptake is now seen in the intermediate cuneiform-2nd
metatarsal joint and the base and shaft of the left 2nd metatarsal. 

Physiological uptake is noted in the liver, spleen, and bone marrow.  No
other abnormalities detected 

OVERALL IMPRESSION

The scintigraphic appearances are consistent with osteomyelitis of the left
medial cuneiform and left 2nd metatarsal shaft with septic arthritis in the
left 2nd-5th tarsometatarsal joints.  

Microbiology report for this patient

Specimen Type : Bone
Description   : left midfoot

Total specimen volume/size: 2x1cm

CULTURE

 Staphylococcus aureus                              ISOLATED

Case Discussion

MRI is the preferred method of evaluation for osteomyelitis in the diabetic foot. 1,2,3

In the diabetic foot, osteomyelitis commonly occurs deep to ulcers, hence in the calcaneum, or at the 1st or 5th metatarsophalangeal joints.3 The tarsal bones are a more common site for Charcot's arthropathy than for infection except where there is a rocker bottom foot with ulcer formation secondary to a Charcot arthropathy. An early Charcot arthropathy and osteomyleitis can look very similar. 3

However this patient had clinical infection with repeated blood cultures positive for Staphylococcus aureus, an elevated CRP (194 mg/l) and an elevated white cell count (17.5 x 109/l)  with a neutrophilia. In this case specific MRI findings for osteomyelitis and septic arthritis are present, namely cortical hone destruction, bone marrow oedema that is markedly low signal on T1 weighted imaging and adjacent rim enhancing fluid collections.

 

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Case information

rID: 30675
Case created: 28th Aug 2014
Last edited: 24th Dec 2016
Inclusion in quiz mode: Included

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