Radiology of the Foot Mark Wahba X-Ray rounds July 24th, 2003.

Radiology of the Foot

Mark Wahba

X-Ray rounds

July 24th, 2003

Goals

• Approach to radiography of the foot

• Become familiar with a Lisfranc injury

• Become familiar with a Jones fracture

Outline

• Bones

• Views

• Important Points

• Lisfranc Joint

• Jones fracture

• Films

The foot

• 28 bones

• 57 articulations

3 anatomic and functional regions

• Hindfoot: talus, calcaneus

• Midfoot: navicular, cuboid, cuneiforms

• Forefoot: metatarsals, phalanges, sesamoids

Bones

Bones

Accessory Ossification Centres

• Normal

• 30% of population

• Smooth corticated surfaces

Adequate views

• Anterior-Posterior

• Oblique

• Lateral

AP

AP view

• Medial margin of the base of the 2nd metatarsal is in line with the medial margin of the middle cuneiform

• Base of the 3rd metatarsal is obscured

• View 1st and 2nd MT, medial and middle cuneiform

AP alignment

Oblique

Oblique view

• Medial margin of the base of the 3rd metatarsal should be in line with the medial margin of the lateral cuneiform

• Base of the 2nd metatarsal is obscured

• View 3,4,5 MT, lateral cunieform, navicular, cuboid

Oblique alignment

Lateral

Lateral

• Hindfoot

• Soft tissues

• View articulations: CalCub, TN, NCun

Bohler’s Angle

• Draw a line from the posterior aspect of the calcaneum to its highest midpoint

• Draw a line from the anterior aspect of the calcaneum to its highest midpoint

• Measured angle is from 20-40 degrees

Bohler’s Angle

Jacques Lisfranc

Lisfranc Joint

• named for Jacques Lisfranc (1790-1847), a field surgeon in Napoleon's army

• “described an amputation performed through this joint because of gangrene that developed after an injury incurred when a soldier fell off a horse with his foot caught in the stirrup”

• refers to the articulation involving the first and second metatarsals with the medial and middle cuneiforms

• Any injury to this area, whether dislocation or fracture-dislocation, is termed a Lisfranc injury

• Initially missed 20% of the time

• high risk of chronic pain and functional disability if they go unrecognized

Presentation

• Hx of Direct trauma• Hx of Indirect trauma: “force is transmitted

to the stationary foot so that the weight of the body becomes a deforming force by torque, rotation or compression”

• Pain in midfoot• Inability to weight bear, especially on toes• Lisfranc Injury of the Foot: A Commonly Missed Diagnosis, BURROUGHS et al., American Family

Physician, July 1998, 58 no. 1 ,p.118

Why?

• “While transverse ligaments connect the bases of the lateral four metatarsals, no ligament exists between the first and second metatarsal bases.  The joint capsule and dorsal ligaments form the only minimal support about the Lisfranc joint, creating a "weak link" that is prone to injury.”

• http://emedhome.com/case-archivedata.cfm?ID=case120701

• Almost invariably involve metatarsal fractures

• Usually the 2nd metatarsal

• # cuboid, cuneiform, navicular occur in 39%

• Weight bearing views are useful

Signs of a Lisfranc injury

• The medial shaft of the 2nd metatarsal should be aligned with the medial aspect of the middle cuneiform on the AP view.

• The medial shaft of the 3rd metatarsal should be aligned with the medial aspect of the lateral cuneiform on the oblique view.

• The first metatarsal cuneiform articulation should have no incongruency.

• The presence of small avulsed fragments ("fleck sign")should be sought in the medial cuneiform-second metatarsal space.

• The naviculocuneiform articulation should be evaluated for subluxation.

• Should be no "step-off" as each metatarsal shaft should never be more dorsal than its respective tarsal bone

• http://emedhome.com/case-archivedata.cfm?ID=case120701

AP

AP

Oblique view

Oblique view

lateral

lateral

Jones Fracture

Jones Fracture

• “Sir Robert Jones described his own fracture of the fifth metatarsal in 1902, when he injured himself while dancing around a Maypole at a military garden party”

• # at base of 5th metatarsal at metaphyseal-diaphyseal junction

• w/in 1.5 cm distal to tuberosity of 5th metatarsal

• Should not be confused w/ more common avulsion # of 5th metatarsal tuberosity

• An oblique radiograph is essential to accurately assess this fracture

• trauma site corresponds to the area between the insertion of the peroneus brevis and tertius tendons

• peroneus tertius originates on anterior aspect of fibula

• injury occurs when the ankle is plantar flexed and a strong adduction force is applied to the forefoot

Jones fracture

• Ortho follow up

• NWB cast 6-8 weeks

• Notorious for nonunion and needing ORIF b/c of low vascularization and high stresses at this site

5th metatarsal avulsion #

• aka Dancer’s Fracture• Conservative

treatment 4-6 wks• Cast, brace, crutches,

wooden soled shoe

• Thought to occur due to stress on the plantar aponeurosis causing an avulsion

• Fractures of the Fifth Metatarsal Yu W. D. et al, THE PHYSICIAN AND SPORTSMEDICINE - VOL 26 - NO. 2 - FEBRUARY 98

Apophysis of 5th metatarsal

• “bony outgrowth that has never been entirely separated from the bone of which it forms a part”

• Found in the skeletally immature

Stress fracture

• a stress phenomenon at the metaphyseal-diaphyseal junction

• “severe intramedullary sclerosis, profound thickening of both the medial and lateral cortices, lucency in the lateral cortex”

• Treat conservatively or operatively depending on activity level

Films

Lisfranc fracture/dislocation

Calcaneal fractures

• Most commonly fractured tarsal bone

• 25% have other lower extremity injury

• thoracolumbar fractures occur in 10% of patients with calcaneal fractures

1st metatarsal #

• Lisfranc injury

Subtalar Dislocation

• Disruption of talocalcaneal and talonavicular joints

• No disruption of the tibiotalar joint

• Closed reduction, ortho consult

Fracture Talus

• 2nd most common tarsal fracture

• Mechanism: plantar or dorsi flexion plus inversion

• High incidence of complications: AVN

Talus fractures

• talar neck

• excessive dorsiflexion of the ankle

• stepping on brakes in MVA, snowboarders

• AVN, subchondral collapse, degenerative arthritis

• Need ortho consult in ED

Fracture of Navicular and Cuboid

• Navicular # high risk of AVN (similar to scaphoid)

• Most can have ortho F/U but if intra-articular should be seen in ED

Lisfranc dislocation

Jones fracture

Lisfranc fracture/dislocation

Fracture calcaneus

Lisfranc injury

Summary

• Know what to look at on each view

• Know what to look for in Lisfranc Injuries

• Know what to look for in a Jones fracture

end

References

• Accident & Emergency Radiology A Survival Guide, Raby et al, 2001 Harcourt Publishers ltd Toronto Chapter 13

• Pitfalls in Radiographic Interpretation, Part 2, Michelle Lin, MD, http://emedhome.com/archives-data.cfm?ID=news042803&Type=news

• Clinical Cases, Emedhom.com, http://emedhome.com/case-archivedata.cfm?ID=case120701

• Lisfranc Injury of the Foot: A Commonly Missed Diagnosis, BURROUGHS et al., American Family Physician, July 1998, 58 no. 1 ,p.118

• Rosen’s Emergency Medicine Concepts and Clinical Practice 5th ed., Marx et al. Mosby, Toronto, 2002 chapter 51

• Wheeless' Textbook of Orthopaedics, http://www.ortho-u.net/Welcome.html

• Fractures of the Proximal Fifth Metatarsal, STRAYER et al. American Family Physician, May 1999, 59 no.9 p.2516

• Lisfranc Fracture Dislocation, Early J. S. http://www.emedicine.com/orthoped/topic511.htm

• Fractures of the Fifth Metatarsal Yu W. D. et al, THE PHYSICIAN AND SPORTSMEDICINE - VOL 26 - NO. 2 - FEBRUARY 98

• Pitfalls in the Radiologic Evaluation of Extremity Trauma:Part II. The Lower Extremity, SHEARMAN C. S. et al, American Family Physician March 1998