Foot and Ankle Ultrasound Timothy W. Deyer, MD East River Medical Imaging

Imaging Indications Tendon pathology Ligament assessment Soft tissue masses Foreign bodies Dynamic evaluation Direct percutaneous intervention

Normal Foot and Ankle Anatomy

Technique Transducer Patient positioning Linear transducer – 9-15 mHz Hockey stick Patient positioning Evaluate structures in longitudinal and transverse planes Anisotropy

Peroneus Brevis Tendon Probe not Perpindicular to Tendon Probe Perpindicular to Tendon

Ankle Ultrasound Regions evaluated Anterior ankle Posterolateral ankle Posteromedial ankle Posterior ankle

Anterior Ankle Technique Structures evaluated Patient supine Knee flexed 90°, plantar aspect of foot flat on table Structures evaluated Extensor tendons Retinaculum Anterior joint space Anterior ligaments

Extensor Tendons Tibialis Anterior Extensor Hallucis Longus Largest extensor tendon Most medial Only tendon sheath to start above the superior retinaculum Extensor Hallucis Longus ½ the size of TA Extensor Digitorum Longus Muscle belly may extend distal to the ankle joint

Anterior Tendons EDL EHL ATT Talus

Longitudinal Image - EHL Extensor Hallucis Longus Tibia Talus

Retinaculum Thin, hyperechoic band Superior and inferior components

Extensor Retinaculum ATT EHL

Anterior Joint Recess Best studied longitudinally Small, < 3 mm, joint effusion is normal Anterior capsule Hyperechoic Cartilage Hypoechoic

Anterior Capsule Talus Tibia Fat Pad Cartilage Tibia Joint Fluid Talus

Anterior Ligaments Interosseous Anterior tibiofibular Anterior talofibular

Anterior Talofibular Ligament Tibia

Posteromedial Ankle Technique Structures evaluated Patient in frog leg lateral position Structures evaluated Medial long flexor tendons Flexor retinaculum Deltoid ligament

Flexor Tendons Examine supra-malleolar, malleolar, infra-malleolar Examine transverse and longitudinal Posterior Tibial Largest of 3 tendons Tendon sheath may normally contain fluid Anisotropy proximal to navicular insertion due to oblique course Flexor Digitorum Longus Flexor Hallucis Longus Posterior to neurovascular bundle at the malleolus

Tarsal Tunnel Flexor Neurovascular Bundle: Digitorum Posterior Tibial Posterior Tibial Artery, Vein, Nerve Posterior Tibial Flexor Hallucis

Longitudinal Image - PTT Distal Anisotropy Posterior Tibial Tendon

Deltoid Ligament Superficial and deep components Plantar flex for anterior components and dorsiflex for posterior

Deltoid Ligament Deltoid Ligament Tibia Talus Talus

Posterolateral Ankle Technique Structures evaluated Essentially the same as for evaluation of the anterior ankle Inverting the ankle aids in visualization Alternatively can have patient lie obliquely with the medial aspect of the foot on the table Structures evaluated Peroneal tendons Posterior ligaments

Peroneal Tendons Continual adjustment necessary to stay transverse Peroneal longus posterior to brevis at the malleolus Examine transverse and longitudinal Distally the tendons are separated by the peroneal tuberacle Distal to the tubercle the tendons have separate sheaths Can perform dynamic evaluation at the malleolus to look for subluxation

Peroneal Tendons Peroneus Longus Peroneus Brevis Lateral Malleolus

Posterolateral Ligaments Posterior Tibiofibular Often poorly seen with ultrasound Posterior Talofibular Not successfully imaged with ultrasound Calcaneofibular Dorsiflex ankle to optimally image

Calcaneofibular Ligament Calcaneus

Posterior Ankle Technique Structures evaluated Prone Feet hanging off the table Structures evaluated Achilles tendon Retrocalcaneal bursa

Achilles Tendon Achilles Retrocalcaneal Bursa Calcaneus

Foot Ultrasound Structures evaluated Plantar fascia Intermetatarsal space Plantar plate

Plantar Fascia Technique Thickness < 4 mm Patient prone Feet overhang the end of the bed Transverse and longitudinal planes Thickness < 4 mm

Plantar Fascia Plantar Fascia

Webspaces and Plantar Plates Technique Dorsal and plantar Spread metatarsal heads Apply increasing pressure Normal appearance Homogeneous echogenic fat Plantar plate Triangular isoechoic structure at base of proximal phalanx

MTP Joint and Webspace Normal Plantar Plate Phalanx Metatarsal Head

Foot and Ankle Pathology

Imaging Indications Tendon pathology Ligament assessment Soft tissue masses Foreign bodies Dynamic evaluation Direct percutaneous intervention

Common Tendon Pathology Tenosynovitis Abnormal amount of fluid in the tendon sheath Tendinosis Enlarged tendon Increased hypoechogenicity between the echogenic fibrils Tendon tear Partial thickness – disruption of fascicular architecture Full thickness – gap Interstitial – tear parallels long axis

Normal Amounts of Tendon Sheath Fluid Site of Fluid Normal Fluid Measurement Posterior Tibial Tendon <4 mm Common Peroneal Tendon Sheath <3 mm FHL Undefined

EDL Tenosynovitis Extensor Digitorum Tendon Sheath Fluid

Thickened Achilles Tendon Achilles Tendinosis Thickened Achilles Tendon Calcaneus

Full Thickness Tear of the Achilles Tendon Tendon Gap Filled with Fat Proximal Distal

Full Thickness Tear of the EHL Fluid in EHL Tear Calcaneus

Interstitial Tendon Tear of the Peroneus Brevis Tendon Peroneus Longus Peroneus Brevis Peroneus Longus Peroneus Brevis Peroneus Longus Peroneus Brevis

Ligament Sprain Tear Thickened Heterogenous Fluid insinuates into ligament

Thickened Heterogenous ATFL ATFL Sprain Thickened Heterogenous ATFL Fibula Talus

Partial ATFL Tear Intact Fibers Fibula Fluid in the Tear Torn Fibers Talus

Plantar Fasciitis Findings Thickness > 4mm Heel pad edema Partial thickness tears

Thickened Plantar Fascia Plantar Fasciitis Thickened Plantar Fascia 6mm Calcaneus

Partial Tear of the Plantar Fascia Intact Fibers Torn Fibers Calcaneus

Morton’s Neuroma and Intermetatarsal Bursitis Non-compressible Hypoechoic +/- entering/exiting nerve Bursitis Anechoic Compressible

Morton’s Neuroma Compression Neuroma Bursitis No Compression

Plantar Plate Findings Degeneration Tear Irregular contour Heterogenous Tear Partial or full thickness Fluid extends into a tear

Plantar Plate Degeneration

Partial tear of the Plantar Plate Plantar Plate Tear Partial tear of the Plantar Plate Intact Plantar Plate

Foreign Body Complimentary to MRI, CT, X-ray Can be used for real time localization

Foreign Body - Splinter

Soft Tissue Masses Complimentary to MRI, CT, X-ray Use Sometimes diagnostic Ganglion Localize Identify involved tissues

Anechoic Structure “Pointing” Toward Subtalar Joint Ganglion Anechoic Structure “Pointing” Toward Subtalar Joint Fibula Talus

Glomus Tumor Hypoechoic Mass Erosion Feeding Vessel Distal Phalanx

Dynamic Evaluation Unique capability of Ultrasound Real time Utility Tendon Subluxation Impingement

Peroneal Brevis Subluxation Peroneus Longus Anterior Posterior Peroneus Brevis Medial Malleolus

Ultrasound Guided Injections and Aspirations Sites Plantar fascia Neuroma Tendon sheath Ganglion Joint

Plantar Fascia Injection Techique Patient prone, foot over edge of bed Linear transducer 1.5” 25 gauge or 3.5” 22 gauge Posterior heel, superficial to plantar fascia Steroid/anesthetic 0.5 cc 1% lidocaine 0.5 cc 0.25% bupivicaine 1 cc Kenalog (40 mg/ml)

Plantar Fascia Injection Needle Steroid/Anesthetic Mixture Calcaneus

Neuroma Injection Techique Patient supine, knee flexed 90 degrees, foot flat on bed Hockey stick transducer 1.5” 25 gauge Webspace, tip in adjacent to neuroma Steroid/anesthetic – 0.75 cc of: 0.5 cc 1% lidocaine 0.5 cc 0.25% bupivicaine 1 cc Kenalog (40 mg/ml)

Steroid/Anesthetic Mixture Neuroma Injection Neuroma Steroid/Anesthetic Mixture Neuroma Needle

Tendon Sheath Injection Techique Position depends on tendon sheath Hockey stick transducer perpedicular to tendon 1.5” 25 gauge Needle into fluid in tendon sheath, if no fluid create effusion with lidocaine Steroid/anesthetic 0.5 cc 1% lidocaine 0.5 cc 0.25% bupivicaine 1 cc Kenalog (40 mg/ml)

Tendon Sheath Injection Steroid/Anesthetic Mixture Needle Interstitial Tears PTT

Ganglion Aspiration Techique Position depends on location Transducer depends on depth 1.5” 18-22 gauge Attempt aspiration Inject lidocaine and re-attempt aspiration Lavage with steroid/anesthetic

Ganglion Aspiration Needle Lidocaine Injection 5th TMT Ganglion

Joint Injection Techique Position depends on joint Transducer depends on joint Tibiotalar – Linear All others – Hockey stick 1.5” 25 gauge Parallel to transducer for tibiotalar Perpendicular for all other joints Variable amount of steroid/anesthetic mixture depending on joint size

Steroid/Anesthetic Mixture Joint Injection Steroid/Anesthetic Mixture Proximal Phalanx Metatarsal Needle Tip

Summary Rigorous technique very important Must know normal anatomy Diagnostic Use Tendinosis/Tenosynovitis Ligament sprain Soft tissue masses Dynamic evaluation Direct interventional procedures

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