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 does flexor stabilization dynamic deformity lead to toe deformity?
- Flexibile pes valgus deformity with excessive STJ pronation
- Causes an unlocked/hypermobile MTJ: forefoot hypermobility
•Flexors fire earlier and longer to try to stabilize osseous structures (overpower the interosseous m)
•Ineffective at controlling the forefoot structures
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)
flexor stabilization etiology and peripheral neuropathy
–> loss of intrinsic power
describe flexor substitution dynamic etiology toe deformity
- Supinated foot
- Late stance phase of gait
- Flexors have gained advantage over the interossei
- Straight contracture of all lesser toes
- Due to weak triceps surae
- Deep posterior + lateral leg muscles try to substitute
- Least common type
how does the deep posterior muscle group contribute to flexor substitution dynamic etiology?
- Tibialis posterior: primary decelerator of pronation & supinator of the rearfoot
- Peroneus longus: plantarflexes 1st ray and causes STJ supination
- FHL & FDL also have axis of supination around the STJ
- Due to a weak tricep surae
- These muscles fire earlier and longer
- The deep flexors attempt to substitute for the weak triceps surae will not create heel lift
- Flexors overpower the interossei and cause hammertoe deformities
- High arched, late stance supinated foot with contracture of the toes results
describe extensor substitution dynamic etiology toe deformity
- EDL gained advantage over the lumbricals
- Severe dorsal contracture at the lesser MTPJ is straight usually greater than 20 – 40 degrees
- Severe dorsal contraction seen during propulsion, swing and heel contact
- Excessive contracture at the MTPJ is also seen: Bowstringing
bowstringing
excessive contracture at MTPJ
seen with extensor substitution etiology
why have extensor substitution?
- Anterior pes cavus
- Ankle equinus
- Weakness of the lumbricals
- Biomechanical
- Neurologic
- Combination
which etiology includes the hallux?
extensor substitution
development timeline extensor substitution
- Usually begins as a flexible deformity
- Which may reduce completely during weightbearing
- Deformity become more rigid as contractures develop
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
how would ankle equinus contribute to hammertoes?
- TA, EDL, EHL fire earlier and longer to attempt dorsiflexion at the ankle to clear the foot
- Ineffective
- EDL then gains advantage over lumbricals
what is the role of the EDL in extensor substitution etiology hammertoes?
- In order to dorsiflex the ankle: must move the MTPJ’s to their EROM before able to maximumly effect the ankle.
- Loss of the lumbricals in neuromuscular conditions-excessive dorsiflexion will occur.
- Severe digital deformity and subluxation.
- Hammered hallux.
hammer vs. claw vs. mallet toe
what is a mallet toe?
- Sagittal plane deformity
- Distal phalanx is flexed on the middle
- PIPJ and MTPJ not usually involved
- Associated with a long digit
- Presents as a flexion contracture at the DIPJ
- Callus at distal tip
- Limited extension at DIPJ
- May or may not be reducible
- Often seen with a long digit
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
