MRI of Pediatric Ankle and Foot. Mahesh Thapa, MD Associate Professor Seattle Children s University of Washington School of Medicine

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1 MRI of Pediatric Ankle and Foot Mahesh Thapa, MD Associate Professor Seattle Children s University of Washington School of Medicine

2 Disclosures Under contract with Lippincott Williams and Wilkins (LWW) for Pediatric Radiology A Teaching File Textbook

3 Acknowledgement I want to thank my coauthors for contributing to this talk and to the Pediatric Radiology manuscript Ramesh Iyer, MD Felix Chew, MD

4 MR Technique Ankle: Reference plane is the table surface Foot: Reference plane is long axis of metatarsals Supine with 20 plantar flexion Ankle surface coil; other small coils (head or extremity)

5 MR Technique T1W, T2W (or STIR) in all planes 3D GRE for cartilage cm FOV 320 x 256 matirx 1-2 signals 3-4mm T1W and STIR; 1.2 mm on 3D GRE +/- Gad; +/- MRA

6 Indications Tumor Infection Arthritis Ligamentous Injury Stress fractures Osteochondral lesions Osteonecrosis

7 Marrow Signal Best assessed with T1W and T2W/STIR Scattered T2W/STIR foci normal

8 Tarsal Coalition Osseous, cartilaginous or fibrous Most are calcaneonavicular or talocalcaneal 50% bilateral

9 Osteochondral Lesion of the Talus OCL = Osteochondritis dissecans, osteochondral defects, transchondral fractures? Cause.? Trauma, ischemia, genetics Usu medial or lateral margins of talar dome

10 Osteochondral Lesion of the Talus

11 Osteonecrosis Chronically ill kids on long-term steroid therapy Talar neck fracture Common sites: talar dome, navicular, 2 nd /3 rd metatarsal heads

$fracture while jumping on$ trampoline.

12 Talar dome osteonecrosis 19-year-old who sustained nondisplaced talar fracture while jumping on trampoline. Tehranzadeh J et al. AJR 2003;181:

13 Talus Blood Supply Tehranzadeh J et al. AJR 2003;181:

14 Hawkins Classification Type I: 0 15% AVN Type II: 20 50% AVN Pearce D H et al. Radiographics 2005;25:

Hawkins Classification Type III: 69 100% AVN Type IV:

15 Hawkins Classification Type III: % AVN Type IV: 100% AVN Pearce D H et al. Radiographics 2005;25:

16 Osteochondrosis of Navicular AKA Kohler disease Typically unilateral Boys > Girls Usually self-limiting with excellent prognosis

17 Stress Fracture Partial or Complete Fatigue vs Insufficiency Stress response (periosteal elevation and marrow edema) Stress Fracture Hindfoot, metatarsals, cuboid Capitate, lunate, scaphoid

18 Stress Fracture

19 Stress Fracture

20 Osteomyelitis

21 Osteomyelitis: Contrast? Controversial What I do: If noncontrast is stone-cold normal, no contrast Non-confluent STIR signal abnormality, no contrast Confluent STIR signal abnormality, or suggestion of fluid, give contrast to exclude abscess Any bony edema give contrast

22 Inflammatory Arthritis JIA Group of arthritides Younger than 16 yrs Symptoms longer than 6 weeks Oligoarticular: < 5 joints Polyartiular 5 joints

23 Inflammatory Arthritis: MR Findings Synovial maximum thickness greater than 3 mm (100% sensitive, 77% specific) with irregularity and enhancement Joint effusion Multifocal marrow edema w/ or w/o enhancement Cartilaginous high T2W signal, erosion, joint space narrowing, soft tissue edema

24 Inflammatory Arthritis: Newer MR Techniques MR spectroscopy (MRS) Diffusion-weighted imaging (DWI) Dynamic contrast-enhancement MRI, T2W cartilage mapping

25 JIA

26 Soft Tissue Neoplasms Uncommon about foot and ankle Benign much more common than malignant Contrast helps to differentiate mass from cyst and lesion extent

along plantar aponeurosis Usu medial aspect of

27 Plantar Fibromatosis Benign soft tissue growth Fibroplastic proliferation of one or more nodules along plantar aponeurosis Usu medial aspect of plantar fascia Strong male predeliction and 10-25% bilateral

(15%) > Abdomen (14%) > Head/Neck (11%) 90% before 3

28 Lipoblastoma & Lipoblastomatosis Occur almost exclusively in infants and young children Extremities (61%) > Trunk (15%) > Abdomen (14%) > Head/Neck (11%) 90% before 3 years of age; virtually all reported cases within first decade

tumors often have nonaggressive appearance, often cyst-like on precontrast imaging There may be

29 Synovial Sarcoma STIR STIR Most common soft tissue malignancy of foot and ankle in children Named for histologic similarity to synovium and not its derivation Non specific appearance Smaller tumors often have nonaggressive appearance, often cyst-like on precontrast imaging There may be indolent growth Synovial sarcoma is prime diagnostic consideration in a nonspecific foot mass in children

$fracture Extend to both medial and lateral cortices$ on coronal plane Involve > 30% of AP calcaneal length

30 Calcaneal Bone Cyst Critical cysts are at risk for fracture Extend to both medial and lateral cortices on coronal plane Involve > 30% of AP calcaneal length Treat with curretage and bone grafting (w/ or w/o symptoms)

31 Chondroblastoma 10% found in hands and feet the talus and calcaneus most common If in talus, all reported cases in the body May be associated with ABC Treat with curettage

32 Osteoid Osteoma In the distal lower extremity, most common in the hindfoot, usually the talus In tarsals, frequently juxta-articular and subperiosteal MR appearance may be confusing

lymphatic malignancies Ewing sarcoma most common

33 Leukemia Mets to foot and ankle are rare but may include multifocal osteosarcoma, or hematologic or lymphatic malignancies Ewing sarcoma most common primary of foot and ankle, usually arising in the calcaneus or metatarsals

Evaluation of Pediatric Foot Pain

May 2006 Evaluation of Pediatric Foot Pain John Flibotte, Harvard Medical School Year III Our Patient AP is a 10 year old boy with chronic R foot pain 2 Anatomy of the Foot Manusov EG, et al. (1996), Part