MRI of the Ankle and Foot

Transcription

1 Acta Radiológica Portuguesa, Vol.XX, nº 79, pág , Jul.-Set., 2008 MRI of the Ankle and Foot Mark Anderson University of Virginia Health Sciences Center, Charlottesville, Virginia discuss the basic MR techniques for obtaining high resolution images of the ankle and foot, including the role of intravenous contrast. describe the appearance of normal anatomic structures of the ankle and foot on MR images. Educational Objectives At the end of both presentations, each participant should be able to: Surface Coil One extremity only Technique: General Position supine prone decreased magic angle Mengiardi, Eur Radiol 2006 list the most common types of pathology affecting the ankle and foot and the MR appearance of each. Disclosure of Commercial Interest Neither I nor my immediate family members have a financial relationship with a commercial organization that may have a direct or indirect interest in the content. Technique: Pulse sequences T1, T2 (fat saturation) Proton density or GRE Gd? Mass -- cystic vs. solid Infection Synovitis screening Arthrography? MR CT Cerezal, Radiol Clin North Am 2005 Schmid, Skeletal Radiol 2003 Outline Technique: Imaging Planes Technique Bones Ligaments Tendons Nerves Masses Diabetic foot Ankle Axial Coronal Sagittal Foot Long Axis Short Axis Sagittal ARP!55

2 Technique: Protocols Ankle/Hindfoot Forefoot Infection Sag T1, STIR Axial T1, Fat Sat T2 Coronal Fat Sat T2 Sag T1, STIR Short Axis T1, STIR Long Axis T1 (to MTs) Post Gd Fat Sat T1 Short Axis Forefoot plus Sag Post Gd Fat Sat T1 Bones: Chronic Trauma Stress Fracture Fatigue vs. insufficiency 57% Tarsals Calcaneus, talus, navicular 36% Metatarsals Niva, Am J Sports Med, 2007 Calcaneal Insufficiency Avulsion (CIA) Fracture Bones: Marrow Normal increased signal? Activity related Altered wgt-bearing Schweitzer, Radiology 1996 Age-related (pediatric) 60% of patients < 16 yrs old disappears after age of 15 yrs Shabshin Ped Radiol 2006 Osteopenia / disuse Subchondral, entheses Elias, Foot Ankle Int 2007 Terminology Osteochondral Lesion Osteochondritis Dissecans (OCD) Osteochondral fracture Osteochondral injury Ankle Acute trauma Talar dome Mid 1/3 lateral (inversion, dorsiflexion, LCL) Posteromedial (inversion, plantarflexion) Bones: Marrow Osteochondral Lesion Differential Diagnosis: edema Activity related Contusion / occult fracture Stress reaction / fracture Transient bone marrow edema Osteomyelitis Osteonecrosis Arthritis-related osteoarthritis inflammatory septic Staging 0 Normal cartilage 1 Abnl SI but intact 2 Fissuring not to bone 3 Flap or exposed bone 4 Loose fragment 5 Displaced fragment Mintz, Arthroscopy 2003 Weishaupt, Eur Radiol 2002 Bones: Acute Trauma Bones: Os Trigonum Contusion, bone bruise Marrow edema Hemorrhage Trabecular fx Fracture Marrow edema Fracture line Ununited tubercle Os Trigonum Syndrome Posterior pain plantar flexion (ballet) MRI marrow edema FHL tenosynovitis (stenosing) 56! ARP

3 Bones: Access. Navicular Tarsal Coalition Type I - distal PT tendon Type II - close proximity to bone Cornuate navicular Pain syndrome Type II and Cornuate MRI: marrow edema 2nd - 3rd Decade Vague hindfoot pain Cartilaginous, Fibrous, Osseous Calcaneonavicular Talocalcaneal middle facet 2 o signs talar beak, C sign Osteonecrosis Bones: Hallux Sesamoids Systemic factors steroids hemoglobinopathy, etc. geographic low SI border heterogeneous (with fat) Flexor hallucis brevis tendons Pain syndrome Stress reaction/fracture (medial) Osteonecrosis (lateral) DJD (subchondral changes) Transient Bone Marrow Edema Ligaments First described in hip Acute onset pain Self-limited usually 3-12 months without sequelae Reversible phase of AVN? core decompression? Radke, Clin Rheumatol 2004 Syndesmotic Lateral Medial Spring Lis Franc Sinus Tarsi Plantar Fascia Transient Bone Marrow Edema Ligaments: Syndesmotic Fernandez-Canton, Skeletal Radiol, pts, severe foot/ankle pain Bone marrow edema pattern Avg 5 bones involved Tarsals, metatarsals 1 year followup complete resolution 72% partial resolution 20% no improvement 8% developed in other foot 24% Interosseous ligament Anterior tibiofibular 2-3 bands Posterior tibiofibular transverse tibiofibular Bartonicek, Surg Radiol Anat 2003 Talus = rectangular ARP!57

4 Ligaments: Lateral Ligaments: Chronic Injury Anterior talofibular taut in plantar flexion most commonly injured Calcaneofibular taut in dorsiflexion Posterior talofibular Anterolateral Impingement Syndrome ATAF ligament injury Persistent pain Scar tissue in lat gutter MRI Intermediate SI tissue T1 and T2WI Duncan, J Foot Ankle Surg 2006 Talus = elongated Arthrography? Robinson, Radiology 2001 Ligaments: Medial Impingement Syndromes Deltoid ligament Deep (tibiotalar) Superficial tibionavicular tibiospring tibiocalcaneal Mengiardi, Radiology 2007 Anterior osteophytes Anteromedial meniscoid lesion deep deltoid anterior talofibular Posterior - os trigonum Posterolateral - post lig Posteromedial deep deltoid Cerezal, AJR 2003 Ligaments: Spring / Lis Franc Sinus Tarsi Spring ligament plantar calcaneonavicular medial and plantar bands Mengiardi, Radiology 2005 Toye, AJR Lisfranc ligament medial cuneiform base of 2 nd metatarsal Cone-shaped space Fat, nerves, vessels, ligs inferior extensor retinaculum cervical ligament talocalcaneal interosseous lig Wide lat - tarsal canal med Ligaments: Injuries Sinus Tarsi Syndrome Interruption Laxity Thickening/irregularity Non-visualization Edema (acute) Oae, Radiology 2003 Gehrmann, Am J Orthop 2005 Lateral pain Sense of hindfoot instability 70% - Prior trauma 30% - Inflammatory arthritis PTT tear / dysfunction Findings Replacement of normal fat SI T1 or SI T2 58! ARP

5 Calcaneus Two bands Medial Lateral Fasciitis Plantar Fascia toes Mechanical (pes cavus, etc.) Degenerative (age related) Systemic disease DDx: Calcaneal stress fx Tendinitis Heel pad inflammation Tendons: Magic Angle Artifact Highly ordered collagen tendons, ligaments Oriented near 55 0 to B 0 Increased signal Short TE sequences T1, PD, GRE Disappears on long T2 Plantar Fasciitis Tendon Pathology Thickened fascia > 4 mm Abnormal signal intensity fascia and perifascial tissues calcaneus Theodorou, AJR 2001 Normal Tenosynovitis Partial Complete TEAR Plantar Fibromatosis Achilles Tendon Fibrous proliferation Fibroblasts and collagen Solitary or multiple T1 - SI T2 - low to intermediate SI Variable enhancement Gastrocnemius/Soleus No tendon sheath (paratenon) Bursae Retrocalcaneal Retro-Achilles (acquired) Flat/concave ventral margin Tendons Achilles Tendon: Pathology Change orientation Pulleys osseous or soft tissue Magic angle artifact Insertional Tendinosis Hagland s Syndrome Bursitis Thickened tendon Pump bump ARP!59

6 Achilles Tendon: Pathology PTT Pathology: MRI Non-Insertional Overuse Tenosynovitis Partial Tear Complete Tear y.o. - weekend warrior Systemic disease RA, SLE Local/systemic steroids Paratenonitis Chronic Tendinopathy Partial Tear Complete Tear Medial Tendons PTT: Pathology Subluxation Partial Tear (split) Post Tibial "Tom Flex Digitorum Dick Arery, vein, nerve and Flex Hallucis Harry T D H Posterior Tibial Tendon PTT Pathology: MRI Oval - 2X size of FDL Flexor retinaculum Insertion sites Medial navicular Cuneiforms Bases of Metatarsals 1-4 Secondary Signs Pes planus Spur/edema post med malleolus Also look for: Morrison, AJR 2001 Spring ligament (92%) Sinus tarsi (72%) Plantar fascia (32%) (Deltoid ligament) Balen, AJR 2001 PTT: Pathology Lateral Tendons Tenosynovitis, Tears Factors Degenerative Middle aged women RA Abnormal stresses Loss of arch 2 0 supports spring ligament deep fibers - deltoid Peroneus Longus and Brevis posterior to lateral malleolus retromalleolar groove Peroneus Brevis anterior or medial thin, moustache Peroneus quartus (17%) distal fibula retrotrochlear eminence (varies) medial and posterior to tendons Saupe, Radiology ! ARP

7 Peroneus Tendons Tarsal Tunnel Syndrome Lateral Malleolus Brevis ant / med may appear c-shaped Longus post / lat Peroneal Tubercle Brevis superior Longus inferior Peroneus Brevis Peroneus Longus Sup Peroneal Retinaculum (calc-fibular ligament) Inferior Peroneal Retinaculum retrotrochlear eminence Lateral base 5 th MT Cuboid tunnel long plantar ligament 1 st MT, medial cuneiform Fibro-osseous tunnel PT, FDL, FHL tendons Tibial nerve, artery, vein Syndrome Pain, paresthesias - sole of foot Etiologies: Tumor, ganglion cyst, dilated veins, post-traumatic fibrosis Delfaut, Radiographics 2003 Peroneus Tendons Tenosynovitis Partial / Complete Tear Subluxation/Dislocation Lateral margin of fibula Retinacular injury or small avulsion fx Entrapment (calcaneal fx) Forefoot Pain: Differential Stress fracture metatarsal hallux sesamoid Morton s neuroma Intermetatarsal bursitis Tenosynovitis Wang, Radiographics 2005 Peroneus Brevis Split Syndrome Forefoot Pain: Bursitis Longitudinal tear (lat malleolus) Predisposing Factors torn sup retinaculum flat or convex lat mall low lying per brev muscle recurrent dislocation May be asymptomatic Intermetatarsal spaces Superior bursa Deep trvs metatarsa ligament Inferior neurovascular bundles Theumann, Radiology 2001 Intermetatarsal bursae Four bursae Between interosseous tendons V III II Major, Foot Ankle Intl 2000 Lamm, J Foot Ankle Surg 2004 Normal fluid I III (<3mm diam) Zanetti, Radiology 1997 Peroneus Brevis Split Syndrome Morton s Neuroma C-shaped Two tendons Adjacent fluid/edema Longus tear in up to 1/3 of cases L Plantar digital nerve Perineural fibrosis 3rd (2nd) web space SI T1 SI T2 Variable enhancement May be asymptomatic Bencardino, AJR 2000 ARP!61

8 Soft Tissue Masses Neuropathic Arthropathy Benign tumors Lipoma Hemangioma GCT tendon sheath Ganglion cyst Plantar fibroma Pressure lesion Midfoot Multiple D s density, disorganization, debris, dislocation bone marrow edema Soft Tissue Masses Marrow Edema: Osteomyelitis? Synovial Sarcoma Most common malignant tumor Young adults Ca++ 50% Non-specific MRI appearance Can appear relatively benign Periosteal Reaction Marrow Edema Marrow Enhancement Neuropathic Osteomyelitis Reactive Masses: Accessory Muscle Infection vs. Neuropathic Isointense to Muscle on MRI Accessory Soleus Ventral to Achilles tendon Peroneus Quartus Adjacent to Peroneus Brevis Fatty marrow - no osteomyelitis + STIR / Normal T1 - reactive + STIR and T1 - Osteo? Neuropathic arthropathy Ischemia Infection Cellulitis Abscess Osteomyelitis The Diabetic Foot The Diabetic Foot: osteomyelitis Primary signs marrow edema STIR and T1 cortical destruction Secondary signs overlying ulcer sinus tract adjacent abscess Location pressure point (osteo) midfoot (neuropathic) 62! ARP

9 Image Analysis Bones Ligaments Sinus tarsi Plantar fascia Tendons Tarsal tunnel Morton s neuroma Plantar fibroma marrow edema - differential syndesmotic rectangular talus lat / med collateral elongated talus normal fat on T1W images thickened, increased signal magic angle; PTT 2 0 signs; P. brevis split space occupying mass low SI T2W images give Gd Image Analysis Diabetic foot primary signs - marrow edema - cortical destruction secondary signs - ulcer - sinus tract - adjacent abscess location - pressure point - midfoot... bx? ARP!63