MCQs – Foot/Ankle 3

MCQs-Foot/Ankle 3
nonunion of talar neck fractures is uncommon; they tend to heal in varus.

– so for undisplaced talar neck – guess about 10% AVN
– for the displaced talar neck with subtalar displacement – guess about 40%
– for the displaced talar neck with ankle displacement – guess about 90%

– the Canale IV is where the talar head dislocates from the navicular

– in tib post insufficiency – there is an avascular region behind the medial malleolus.

– in tib post insufficiency – it is most common in middle aged females; the Choparts joint is in valgus, and the lateral x-ray is often abnormal, showing the sagging of the midfoot with loss of longitudinal arch – don’t count on the x-rays being normal!!

– the ankle injuries with fibular fractures above the syndesmosis are often pronation external rotation injuries (Weber C). The supination external rotation injuries often lead to fibular fractures at the level of the joint (Weber B).
– for the hemiplegic man with dynamic equinovarus, use an AFO to counter the equinus, and a lateral T strap to pull his forefoot out of varus.

– in a longstanding hemiplegic with claw-toes – treat with flexor tendon release or Girdlestone-Taylor flexor to extensor transfer. You can treat conservatively I suppose, but this will not get better because it has a neurologic origin. The conservative treatment would be a deep toe-box shoe with a metatarsal bar.

– in the Chevron – do not do an adductor hallucis release – going laterally endangers the blood supply. You do remove the medial eminence and shift the distal fragment laterally and plicate the medial capsule.

– in LisFranc injuries, the 2nd MT is the keystone. Some say that the severity of injury is in fact the most important factor in the final outcome; others argue that achieving anatomic reduction and fixing it there is more important. There certainly are a lot of different types (divergent, homolateral, isolated).
– the most common cause of acute acquired flatfoot is tib post rupture

– in rheumatoids, you’d be crazy to try soft tissue reconstruction of tib post – they need bony procedures, starting with subtalar arthrodesis if possible; if there is more severe deformity, they need a triple.

– for the major crush injury across the foot – try for a trans-met amputation; if not, Symes.

– for medial subtalar dislocations (acute acquired clubfoot): they are usually easier to reduce closed than the lateral dislocations. The obstructions include: impaction fracture of the talar head, the extensor tendons (the talar head bursts through them dorsally), capsule. They are about twice as common as lateral dislocations.

– for lateral subtalar dislocations (acute acquired vertical talus): these are more often impossible to get back in than the medial dislocations. Obstructions include: tibialis posterior (flips over the medial malleolus), impaction fracture of the talar head, and sometimes the flexor digitorum longus tendon.

– both medial and lateral subtalar dislocations can be approached medially.

– for the highly unusual anterior subtalar dislocation, it probably pulls the peroneals with it and these need to be approached anterolaterally.

– it would be inappropriate to use a Swanson arthroplasty in Frieberg’s infraction – if they need salvage – fuse it!

– for talar neck fractures: Many of the minimally displaced fractures assume a varus deformity at the fracture site that cannot be appreciated on standard x-ray projections. Canale and Kelly described the best x-ray technique to demonstrate the entire talar neck in the AP direction. With the ankle in maximal equinus, the foot is placed on a cassette and pronated 15o; the x-ray tube is directed upwards at a 75o angle from horizontal.

Canale and Kelly View
– maximal plantarflexion
– pronation or eversion of 15 degrees
– aim x-ray cephalad 75 degrees from horizontal