Epidemiology:
Approximately 50% cases of osteomyelitis occur in the first 5 years of life1,
with boys more commonly affected than girls1,3.
The incidence of osteomyelitis varies between 1 and 13 per 1000004.
Septic arthritis and osteomyelitis are the most common infections.
Pathology:
Infection mostly occurs by bacterial haematogenous spread with the metaphysis being the most usual site2.
Other modes of spread of infection are direct trauma and secondary to vascular insufficiency.
Staphaphylococcus Aureus is the most common organism,
accounting for 70-90% of infections1.
Osteomyelitis and septic arthritis can co-exist.
These can result in growth plate and epiphyseal damage.
Clinical Presentation:
The symptoms include:
- Fever
- Joint/bone pain,
- Unable to move limb/weight bear/walk
- Hot,
swollen joint
Imaging:
Radiographs:
Plain radiographs in early infection may be normal or just show soft tissue swelling.
Periosteal reaction,
lucent changes are seen later1,
approximately 10-21 days after onset of symptoms.
Radionuclide study:
Technetium labelled methylene diphosphate isotope scans can become positive with 72 hours after symptom onset1.
They can be useful in multifocal osteomyelitis or when exact location is not obvious.
Ultrasound:
Ultrasound is the usual primary imaging modality to assess for soft tissue collection or joint effusions.
Magnetic Resonance Imaging (MRI):
MRI provides excellent spatial resolution for both bone and soft tissues.
They are useful is assessing for marrow oedema and cortical destruction,
subperiosteal fluid and soft tissue collections.
Post gadolinium contrast allows assessment of abscess formation.
MRI is the imaging modality of choice with high sensitivity and specificity4.
Limitations include availability,
and need for sedation in young children.
Diagnosis and Treatment:
- Diagnosis is usually made based on clinical symptoms,
blood parameters which include raised white cell count (WCC),
erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP),
and imaging.
- Aspiration of fluid aids in identifying microbiological organism.
- Prompt joint washout,
decompression and treatment with appropriate antibiotics remain the mainstay in managing septic arthritis and abscess.
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We present a case series from our institute below:
Case 1: 17 year old with calcaneal pain and limp
Imaging:
Fig. 1: Baseline radiograph is normal
Fig. 2: Day 8 radiograph shows a lucent area in the posterior aspect of calcaneum (white arrow)
Fig. 3: (A) Sagital T1w (B) Axial T2w Fat saturated (FS) (C) Post gadolinium axial T1w Fat saturated images shows low T1 area (black arrow) which is bright on T2wFS (blue arrow) and shows peripheral enhancement (white arrow) post contrast. There is marrow and surrounding soft tissue oedema
Diagnosis: Osteomyelitis of the right calcaneum with a small intra-osseous abscess
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Case 2: 8 year old,
type 1 diabetic with pain,
and unable to weight bear.
No trauma.
Raised inflammatory markers.
Imaging:
Fig. 4: (A) Normal right knee (B)There is widening of right sacroiliac joint. Both hip joints are normal.
Fig. 5: Normal ultrasound right hip joint with no effusion seen
Fig. 6: (A) Coronal T2w FS image shows fluid in the right sacroiliac joint (SIJ) with widening of the joint (blue arrow). There is marrow oedema and soft tissue oedema (orange arrow). (B) Coronal T1w FS post gadolinium images shows an enhancing right SIJ effusion (white arrow)in keeping with septic arthritis
Fig. 7: 1 month post treatment there is mild periosteal reaction and sclerosis of the right ilium
Diagnosis: Right sacroiliac joint septic arthritis with osteomyelitis in the ilium
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Case 3: 3 month history of swollen finger and unable to strech elbow
Imaging:
Fig. 8: There is a permeative process in the middle phalanx with associated soft tissue swelling
Fig. 9: (A) Coronal T2w FS, (B) Coronal T1w show soft tissue swelling bright on T2w (blue arrow) and isointense on T1w (white arrow) with underlying bone destruction. (C) Right elbow Sagital T2w FS image in the same patient shows a large joint effusion (yellow arrow).
Fig. 10: 1 year post treatment X-ray shows bony remodeling of the middle phalangeal base with partial dorsal subluxation
Diagnosis: Tuberculous dactylitis and right elbow septic arthritis
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Case 4: 11 Year old with pain left knee and raised inflammatory markers
Imaging:
Fig. 11: (A) Initial radiograph is normal,(B) Day 1 post operative radiograph shows multiple bony fenestration's and subcutaneous drain, (C)6 week post treatment radiograph shows periosteal reaction in the distal femur
Fig. 12: (A) Cor T2w FS and (B) Cor T1w FS post gadolinium images show marrow oedema (blue star), pyomyositis and collections (white arrow) which shows peripheral enhancement (red arrow)
Diagnosis: Left distal femur osteomyelitis,
surrounding pyomyositis and abscess
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Case 5: 14 year old with swollen right ankle ,
tender medial malleolus
Imaging:
Fig. 13: Normal right distal tibia
Fig. 14: (A) Axial T2w FS image shows marrow oedema in distal tibia (white arrow) and subperiosteal fluid (red arrow). (B) Sagital T1w image shows patchy marrow signal abnormality
Fig. 15: (A) Bone scan shows increased tracer uptake in the right distal tibia (blue arrow), and (B) White cell HMPAO scan shows inflammatory change and increased tracer uptake in distal tibia (red arrow). No other site of pathological tracer uptake is seen
Diagnosis: Right distal tibial osteomyelitis
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Case 6: 11 year old with cerebral palsy,
chronic non healing ulcer
Imaging:
Fig. 16: No evidence of bony destruction or periosteal reaction
Fig. 17: (A) T1w image shows cutaneous ulcer overlying base of 5th metatarsal with underlying low marrow signal in the 5th metatarsal (white arrow), (B) T2w FS images shows marrow oedema and subperiosteal fluid (orange arrow), (C) Radiograph 5 month post treatment shows thickenned periosteum with healing (yellow arrow)
Diagnosis: Left 5th metatarsal osteomyelitis with cutaneous ulcer
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Case 7: 3 month Old,
right elbow swelling,
systemically unwell,
raised inflammatory markers
Imaging:
Fig. 18: Florid periosteal reaction in the distal humerus (white arrow)
Fig. 19: Image on left: T2w sagital image shows large elbow joint effusion (red arrow), with fluid tracking into the physis (white arrow). Image on right: Post contrast T1wFS sagital image shows enhancing joint effusion with sub-periosteal fluid (blue arrow)
Diagnosis: Right elbow septic arthritis with distal humeral osteomyelitis
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Case 8: 10 year old,
1 year history of ankle pain and soft tissue swelling
Imaging:
Fig. 20: (A) Plain radiograph shows a left distal tibial lucent lesion extending into the physis (black arrow). (B) Cor T2w FS image shows an intra-osseous abscess extending into the growth plate and epiphysis (red arrow). There is marked marrow oedema in the distal tibia (blue asterisk). (C) Post drainage of abscess lateral ankle radiograph shows cortical defect (white arrow). (D) 10 month post treatment lateral ankle radiograph shows healing
Diagnosis: Left distal tibia brodie's abscess
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Case 9: 18 month old with left hip pain,
reduced range of movements,
non weight bearing and fever
Imaging:
Fig. 21: (A) Frog leg pelvic radiograph - there is a lucent area in proximal left femoral metaphysis with extension into the growth plate (black arrow). (B) Hip ultrasound - large left hip joint effusion with synovial thickening (blue asterisk). (C) Cor T1wFS post gadolinium images shows enhancing abscess in proximal left femoral metaphysis with extension into the growth plate (white arrow). There is surrounding marrow oedema, hip joint effusion and surrounding muscle oedema
Diagnosis: Left proximal femoral metaphyseal brodie's abscess
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Case 10: 11 month old with right shoulder pain and fever
Imaging:
Fig. 22: (A)Ultrasound - Glenohumeral joint (white asterisk) with joint effusion (blue asterisk). (B) Sag T2wFS image with joint effusion, marked marrow oedema in the proximal humeral diametaphysis (black asterisk) and subperiosteal fluid (black arrow). (C) Post contrast axial T1wFS image with enhancing joint effusion (white arrow)
Diagnosis: Right glenohumeral joint septic arthritis with proximal humeral osteomyelitis
Summary:
We have shown:
- the early and established radiological appearances of musculoskeletal infection in the paediatric population.
- a spectrum of cases that illustrate the importance of a multimodality approach to imaging in this patient cohort.