56: Digital Deformities - Yoho Flashcards
define hammertoe
A deformity in which the proximal phalanx of one of the smaller toes is bent upward or is dorsiflexed at the metatarsal-phalangeal joint, and the middle and distal phalanges are sharply bent downward, so that they form a more acute angle with the proximal phalanx
most common etiology of digital deformities
biomechanical dysfunction
cavus foot and toe deformity
need to rule out a neuromuscular condition
anatomy review
Stabilization of the lesser toes against the ground at the MTPJ’s provided mainly by …
FDL and FDB
extensor sling vs. extensor wing
- Dorsiflexion at the lesser MTPJ’s is accomplished by the EDL through the extensor sling which supports the proximal aspect of the proximal phalanx.
- Dorsiflexion of the middle and distal phalanges is mediated through the extensor wing controlled primarily by the lumbricals.
what holds the extensor tendons in place
- Held in place by 2 fibrous sheaths: Extensor hood
- Proximal part: Extensor sling: fibers encircle and attach to the plantar plate
- Interosseous muscles contribute to the sling
- Distal part: Extensor wing: Formed by expansions of the lumbricals
long and short flexors are _____ phase muscles
stance
plantarflex and stabilize digits during stance phase of gait
flexors –> Plantarflexory force to the MTPJ (non-weight-bearing), but dorsiflex MTPJ in weight-bearing.
lumbricales are a _____ phase muscle
interossei are a _______ phase muscle
swing
stance
anatomy review
how many interossei are there? what do they do?
seven
4 dorsal, 3 plantar
- Pass above the deep transverse metatarsal ligament but below the transverse axis of the MTPJ and insert into the base of the proximal phalanx.
- Stabilize in the transverse plane and plantarflex the MTPJ.
- Balances the reverse buckling effect of the flexors during stance phase of gait.
how many lumbricals? what do they do?
four muscles arising from FDL tendons
- Course beneath the deep transverse intermetatarsal ligament.
- Insert medially into the base of the proximal phalanx and extensor hood
- Plantarflex and adduct the MTPJs and dorsiflex the IPJs
- Balance the effect of the long extensors and passive pull of the long flexors during swing phase of gait.
static pathologic anatomy assoc with biomechanics
associated with HAV
confining shoegear
3 dynamic pathologic anatomy digital deformities
flexor stabilization
flexor substitution
extensor substitution
describe flexor stabilization etiology
- pronated foot
- late stance phase of gait
- FDL & FDB have gained mechanical advantage over the interossei muscles
- Often a adducto-varus rotation of the 5th digit: due to weakness of the quadratus plantae
- _Most common type*_
how is quadratus plantae weakness associated with flexor stabilization etiology?
- Excessive STJ pronation
- Forefoot abduction
- Changes the lateral vector force of the QP
- More medial pull by the FDL creates a adducto varus rotation of the 5th digit (maybe 4th as well)
bowstringing
excessive contracture at MTPJ
seen with extensor substitution etiology
what is an anterior cavus and how does it develop hammertoes?
- Increase declination of the forefoot
- EDL has longer to travel: tendon does not lengthen but a passive pull is then place on the digits at the joints
- Increased retrograde force placed on the metatarsal heads increasing the anterior cavus deformity: vicious cycle
hammer vs. claw vs. mallet toe
what is a clawtoe?
- Middle & distal phalanges are flexed on a dorsiflexed proximal phalanx
- Associated with cavus foot and neuromuscular disorders
- Dorsal contracture of the MTPJ and plantar contracture of the interphalangeal joints
- Plantar protrusion of the MTPJ is seen
- Mechanical hyperkeratosis
- Metatarsalgia
- Flexible or rigid
