MG 105/106: lisfranc dislocation

Question 1

thickness of lisfranc ligament

Answer 1

1.5 cm x 0.5 cm

Question 2

stress test for lisfranc

Answer 2

pronation and abduction of midfoot and forefoot

maintain hindfoot in inversion while performing stress test to eliminate STJ

Question 3

Diastasis of _______ between 1st an 2nd metatarsal indicates lisfranc tear

Answer 3

2-5 mm

Question 4

Medial oblique view for lisfranc injury

Answer 4

malalignment of base of 4th met and medial aspect of cuboid

Question 5

lateral view for lisfranc injury

Answer 5

flattening of longitudinal arch
medial cuneiform more plantar to 5th met
mets dorsally displaced on cuneiforms

Question 6

what may be some reason why a lisfranc dislocation may not be able to be reduced

Answer 6

1. soft tissue/bone impingement such as TIBIALIS anterior
2. Peroneus longus interposition
3. Avulsed fragment from Lisfranc ligament

Question 7

whats the golden time frame for ORIF of lisfranc

Answer 7

within 6 weeks of injury–after 6 weeks may result in poor functional outcome

Question 8

incision placement for lisfranc ORIF for medial/lateral injury

Answer 8

a) 1st - medial dorsal first met-cuneiform
2nd slightly lateral and parallel with the 2nd met shaft starting distal 1/3 metatarsal extending to navicular: provides exposure to TMT 1-3

3rd : over 4th met or between 4th and 5th met

Question 9

which joint should be close reduced reduced first

Answer 9

Try to reduce 2nd metatarsal into cuneiform keystone and others may reduce due to Vassal phenomenon/principle

once medial TMT reduced then lesser TMT will become well placed (vassals principle)

Question 10

which joint is fixated first in ORIF

Answer 10

1st TMT

Question 11

most common bone injured in midfoot

Answer 11

navicular

Question 12

cause for avulsion fracture to the navicula

Answer 12

dorsal tibionavicular ligament

Question 13

vascular supply for navicular

Answer 13

dorsalis pedis dorsally, medial plantar artery plantarly

anastomosis of the arteries to tuberosity medially

creates watershed area in central portion

Question 14

ligamentous attachments to cuboid

Answer 14

calcaneocuboid ligament, bifurcate ligament dorsally, and then long plantar ligament plantarly

Question 15

nutcracker fracture

Answer 15

abduction of forefoot compresses the cuboid between the bases of 4th and 5th met and anterior calcaneus

Question 16

what may prevent a successful close reduction of cuboid

Answer 16

peroneus longus

Question 17

what is a swivel dislocation

Answer 17

malalignment results in medial and plantar dislocation of the TN joint that can be associated with rotation trauma of CCJ

Question 18

for a chopart dislocation, what should be reduced first

Answer 18

TNJ and then CCJ

Question 19

MOI for chopart dislocation

Answer 19

heavily loaded distortion of midfoot in supination-flexion as present with a cavus malalignment

Question 20

what is the minimum skin bridging needed between incisions

Answer 20

2 cm

Question 21

Describe stress test for lisfranc joint

Answer 21

Stabilize hindfoot: apply adductory/supinatory force on the lateral asppect aspect of foot at the level of 5th met base.

then apply abductory/pronatory force near the base of 1st metatarsal

piano key test: stress each metatarsal base in dorsal and plantar direction while grasping respective met heads