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22b - Answer: 59-year-old male presents with right foot infection

Pomeranz, Stephen
Stephen J Pomeranz, MD
Chief Medical Officer, ProScan Imaging. Founder, MRI Online
Includes DICOM files

HISTORY: 

This 59-year-old male presents with right foot infection.

(QUIZ ANSWER) NOT A FINDING IN THIS CASE: 

Forefoot intermetatarsal bursal cyst.

Using the diagnostic web viewer, we have provided images that assist in telling our clinical story. Areas of significance are indicated below.

FINDINGS:

SKELETAL: Status post resection of the fifth ray. See accompanying x-ray. Bony resorptive change base of the fourth metatarsal at the head, active inflammation involves the cuboid/fourth MT articulation with osseous edema throughout the cuboid, proximal half of the third metatarsal, head of the 2nd metatarsals as well as lateral and intermediate cuneiforms sparing the navicular first cuneiform and first metatarsal bones of the foot. Remnant dysplastic myositis ossificans or periosteal thickening following resection of the fifth metatarsal is nearly invisible on MRI. 

LISFRANC JOINT: Intact. Surrounding edema. Dorsal fibers from the base of the third MT to the medial cuneiform are well demonstrated and intact. Edema between the base of the first and second MT without subluxation. 

MUSCULATURE: Intrinsic muscles of the foot are intact without hemorrhagic tear or strain. Diffuse myoedema and fatty infiltration of forefoot musculature. 

JOINT SPACES and PLANTAR ARCH: Active enhancing tissue at the cuboid/4th MT articulation. In short-axis (labeled coronal plane) and especially evident on the T1 postcontrast sequences, enhancing and nonenhancing foci of complex fluid demonstrated dorsal to the cuboid 15mm in transverse diameter with smaller 5mm fluid collection encircling and medial to the tendinopathic peroneus longus tendon. Complex nonenhancing fluid collection at the joint space well shown series 15 image 5. Horizontal T2 fluid signal region dorsal to the flexor digiti minimi and abductor digiti minimi muscles is seen at the edge of the film.

Innumerable complex fluid collections in the plantar space of the midfoot.

Moderate degenerative arthrosis with subchondral sclerosis and cystic remodeling first MTP articulation. 

PLANTAR SOFT TISSUE/SUBCUTANEOUS FAT: Pressure-related soft tissue thickening/fibrosis deep to the head of the 5th metatarsal. No forefoot intermetatarsal bursal cyst; no perineural fibrosis or discrete Morton's neuroma.

Diffuse swelling within the dorsum of the foot extends to the ankle with soft tissue swelling along the dorsolateral aspect of the foot greater than along the medial ankle. Additional chronic tear and edema of the oblique head adductor hallucis with edema extending into the second intermetatarsal space and medial dorsum of the foot at the level of the junction mid and proximal metatarsals. Signal abnormality in the mid arch of the foot extends longitudinally 26mm with short-axis diameter 16 x 13mm. 

PLANTAR PLATES: No sesamoiditis or AVN. First MTP articulation, to include the medial and lateral collateral ligaments and intersesamoid ligament intact. Sclerosis and eburnation with bony remodeling of the tibial and lateral sesamoids. Intact plantar plates without chronic or acute tear. 

Active peritendinosis follows the course of the peroneus longus tendon especially distal to the cubital tunnel in addition to extensive peritendinitis and extensive tenosynovitis along the posterior tibialis and anterior tibialis muscle groups of the hindfoot. 

CONCLUSION

1. Charcot foot with findings of bony resorptive change plantar base of the fourth metatarsal and regional edema throughout the cuboid worrisome and most consistent with joint space infection and active osteomyelitis. Innumerable complex fluid collections in the plantar space most likely micro-abscesses. Bony resorptive change at the site of the cuboid fixation anchor well shown on plain x-ray. Case and findings discussed with the ordering radiologist and Oregon (BW).

2. Small plantar surface ulceration immediately deep to the mid arch without communication to the hemorrhagic and tendinopathic adductor hallucis brevis oblique head.

3. Hemorrhagic midfoot myotendinous tear oblique head of the adductor hallucis. Note intermetatarsal edema extends from the disrupted, chronically torn adductor muscle dorsally into the second intermetatarsal space and continues medially deep to the extensor digitorum tendon group. 

4. Diffuse diabetic myopathy. Peritendinitis and tenosynovitis peroneus longus and posterior tibialis tendons below the ankle.

5. Status post resection of the fifth ray. See accompanying x-ray. 

Case discussed with the ordering physician (radiologist in Newport, Oregon BW).

LESSON 2, TOPIC 66

Case Challenge: Foot & Ankle MRI Cases

Case Challenge

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Content reviewed: August 31, 2021

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