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#4 Surg > 54 - Biomechanics of Hallux Limitus > Flashcards

54 - Biomechanics of Hallux Limitus Flashcards

1
Q

Definition of hallux limitus

A
  • Deformity of the 1st MPJ in which base of proximal phalanx of hallux is subluxed plantarly upon the 1st metatarsal head
  • Hallux cannot dorsiflex 65° during propulsive phase of gait a,.nd this limitation of motion is called hallux limitus
  • When all motion ceases, it is called hallux rigidus
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2
Q

Hallux limitus vs rigidus

A
  • Some consider hallux limitus to be the pathology that leads to the deformity of hallux rigidus
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3
Q

Patient presentation in hallux limitus/rigidus

A
  • Marked by patient’s complaint of pain
  • Grinding and limited motion at the 1st MTPJ
  • Dorsal bump on the 1st metatarsal head
  • Combined with radiographic findings
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4
Q

Osseous compression

A
  • Osseous compression occurs on dorsal aspect of 1st MPJ
  • Dorsal aspect of proximal phalanx jams into upper 1/3
    of articular surface of metatarsal head which results in DJD
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5
Q

Bony prominence

A
  • Could be secondary to the position of the metatarsal head

- Could also be secondary to an osteophyte located here

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6
Q

Etiologies: Hypermobility

A
  • Hypermobility of 1st ray, in association with eversion of the foot caused by abnormal STJ pronation in a rectus foot type
  • Hypermobility caused by inadequate plantar stabilization by peroneus longus
  • Hypermobility with eversion needed so that medial force will dorsiflex 1st metatarsal
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7
Q

Increased forefoot pressures

A

Foot types that increase medial forefoot force will lead to hallux limitus
o Everted calcaneus
o Everted forefoot: plantarflexed 1st ray or flexible FF valgus (both load the 1st ray sooner with greater force)

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8
Q

What is necessary for normal 1st MPJ motion?

A
  • 1st Ray plantarflexion
  • 2nd Metatarsal longer than the 1st (normal parabola or arc)
  • Normal intrinsic and extrinsic muscle function
  • Normal sesamoid function (arthritis or damage to the sesamoids can prevent the metatarsal from sliding over the sesamoids smoothly)
  • Intact base of the proximal phalanx
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9
Q

1st MPJ function in gait – from midstance to toe-off

A
  • Hinge motion for the first 20 ° of motion in the joint
  • Arthroidal motion is the sliding motion with plantarflexion of 1st ray with heel lift, STJ supination, and normal sesamoid function – includes dorsiflexion to end ROM during propulsion with 35 ° knee flexion and 20 ° ankle plantarflexion
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10
Q

Hinge motion

A
  • Hinge motion encompasses the 1st 20 degrees MPJ motion
  • Arthrodial motion occurs at 20 degrees
  • Diagram
    o I = Rolling motion
    o II & III = Tangential represent sliding
    o IV = Compression from velocity
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11
Q

Cam-shaped metatarsal head

A
  • Here is an example of the cam-shaped metatarsal head (cam shaped means not quite round – somewhat off-centered and somewhat oval shaped)
  • Design of the head is the shape of a cam, rolling, sliding and compression occur
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12
Q

ROM of MPJ

A
  • Average ROM is 55-85, (amount of dorsiflexion needed 65-75) for gait
  • Propulsive phase of gait
    o Hip extension
    o Knee flexion
    o Ankle plantarflexion
  • As the 1st ray plantarflexes, it slides proximally
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13
Q

Etiologies

A
  • Hypermobility (already discussed)
  • Pronating (everted) foot type
  • Immobilization of the 1st ray
  • Excessively long metatarsal
  • Metatarsus primus elevatus
  • High heels
  • Trauma
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14
Q

Etiology: Pronating (everted) foot type **

A
  • Peroneus longus is responsible for plantaflexion of the 1st ray with stabilization of the lesser tarsus during gait
  • In a normal foot, the peroneus longus travels along the cuboid on its way to the navicular and proximal portion of the first metatarsal – running parallel to the WB surface of the foot
  • If an individual is a pronator, there is widening present in the midtarsal region (“splaying”)
  • The everted position of the calcaneus causes the widening, but also causes the peroneus longus tendon to be closer to the ground during WB
  • This prevents the peroneus longus from achieving a mechanical advantage along the midtarsal joints and leads to instability (peroneus longus is not able to tighten up the midtarsal joint during gait for stability)
  • Over time, the attachment of the peroneus longus on the navicular shifts to become more laterally located and less plantarly, further decreasing the mechanical advantage of the peroneus longus and the peroneus longus is no longer effective at plantarflexion
  • THIS CONCEPT IS IMPORTANT
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15
Q

Etiology: Immobilization of the 1st ray

A
  • Arthritis at the 1st metatarsal-cuneiform joint
  • Acquired in long standing cases of abnormal STJ pronation due to subluxation at 1st met-cuneiform joint
  • Calcaneal-navicular synostosis (prevents mobilization of the 1st ray)
  • Will not be able to achieve the plantarflexion necessary to get the metatarsal to line up correctly
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16
Q

Etiology: Excessively long metatarsal

A
  • There will be an abnormal parabola or arc present
  • It is simulating an elevatus because the 1st ray is excessively long
  • Weight-bearing forces during propulsion concentrated for excessive period at distal 1st metahead which prevents plantarflexion of 1st ray and leads to delay in proximal migration of transverse joint axis to allow dorsal migration of phalanx on the 1st metahead
17
Q

Etiology: Metatarsus primus elevatus

A
  • Congenital form = 1st ray has full range of motion, but lacks adequate plantarlexion to allow normal hallux dorsiflexion
  • Acquired form = less than normal 1st ray motion, and 1st ray fixed in elevated position
18
Q

Etiology: High heels

A
  • Increasing heel height reduces 1st MPJ dorsiflexion
  • 1” heel automatically dorsiflexes 1st MPJ by 20°; each additional inch further reduces it by 14°
  • If we need 65° for normal function, a 2” heel allows only 31° of dorsiflexion (or the joint needs to dorsiflex around 100°)
19
Q

Etiology: Trauma

A
  • Blunt trauma

- Turf toe

20
Q

Pathomechanics

A
  • Restricted 1st ray plantarflexion prevents proximal gliding of metatarsal over sesamoids and subsequent positioning of the 1st metatarsal below the transverse plane of the lesser metatarsal heads
21
Q

Windlass mechanism (tightening of the arch and supination of the foot)

A
  • Heel lift w/ankle plantarflexion will dorsiflex the MPJ
  • Tightening of the plantar fascia, to raise the arch and shorten the foot
  • Raising the arch will resist elongation of the foot, and assist in resupinating the subtalar joint
  • Windlass function is blocked by any force that drives the 1st ray up (1st ray is prevented from plantarflexing, hallux can’t dorsiflex, plantar fascia tension increases, and 1st MPJ compression increases)
  • The windlass mechanism and the peroneus longus have a similar function
  • When the windlass mechanism is not functioning, there will be a similar result as when the peroneus longus is not functioning in a pronated foot… There will be a lack of plantarflexion of the 1st metatarsal, preventing normal motion of the MPJ
22
Q

Radiographic findings

A

Functional adaptation of bone
o Occurs in young patients by resorption of dorsal bone at 1st metahead and allows increased range of hallux dorsiflexion
o In adults, this same intermittent compression leads to osseous proliferation on the dorsal surface of the 1st metahead and produces a spur or “dorsal flag” sign

Degenerative changes at 1st MPJ
o Subchondral sclerosis, asymmetrical joint narrowing, subchondral cysts, and osteophytes will develop with broadening of the base of the proximal phalanx, and metatarsal head
o The arthritis seen in degeneration is very different than gouty arthritis or rheumatoid arthritis

23
Q

Sequelae

A
  • 1st MTPJ Pain, limited motion
  • IPJ arthritis
  • Nail trauma
  • Shoe pressure on dorsal bump leading to pain or cystic changes in EHL or adventitious bursa over bone
  • Lesser metatarsalgia
24
Q

Classification (Oloff & Jacobs) radiographic

A
  • Grade 1
  • Grade 2
  • Grade 3
  • Grade 4
25
Q

Classification (Oloff & Jacobs) radiographic grade 1

A 
o	Minimal adaptive changes
o	Metatarsus primus elevatus (noted)
o	Plantar subluxation of phalanx on metahead
o	Rearfoot pronation 
o	Pain on end ROM
26
Q

Classification (Oloff & Jacobs) radiographic grade 2

A

o Flattening of 1st metahead, with possible osteochondral defect
o Small dorsal exostosis
o Pain on end ROM
o Passive ROM limited with forefoot loading

27
Q

Classification (Oloff & Jacobs) radiographic grade 3

A

o More severe flattening of 1st metahead
o Osteophytes, especially dorsally on both metahead and phalanx
o Asymmetrical joint narrowing
o Subchondral eburnation with possible cysts
o Pain on full r.o.m. with crepitus
o Degeneration of articular cartilage
o Broadening of 1st MPJ

28
Q

Classification (Oloff & Jacobs) radiographic grade 4

A

o Ankylosing with no joint space
o Total obliteration of joint space
o Loose bodies
o

29
Q

Two types of hallux limitus

A

Functional vs structural hallux limitus

30
Q

Structrual hallux limitus

A

o Osseous adaptation has occurred and no motion is present
o Hallux dorsiflexion decreased when first ray is loaded (passive dorsiflexion of great toe in RCSP) and unloaded (passive dorsiflexion of great toe in NCSP)***
o Limited dorsiflexion loaded and unloaded

31
Q

Functional hallux limitus

A

o Hallux dorsiflexion decreased ONLY when the first ray is loaded***
o Can also get a good idea with patient sitting: with functional hallux limitus you will have decreased motion when dorsiflexion attempted with STJ not in neutral position vs. normal movement when STJ in neutral
o Functional hallux limitus may develop into structural
o Functional does not have the arthritic changes restricting hallux dorsiflexion
o Functional is due to hypermobile dorsally displaced 1st ray that possibly can be controlled with orthotics that prevent abnormal pronation and allow for 1st ray plantarflexion

32
Q

STUDY – Pronation in hallux limitus (SKIPPED)

A
  • Severity of pronation and classification of first metatarsophalangeal joint dorsiflexion increases the validity of the Hubscher Maneuver for the diagnosis of functional hallux limitus
  • 30 adults clinically diagnosed with functional hallux Limitus (dorsiflexion
33
Q

Orthotic casting for FUNCTIONAL hallux limitus

A
  • *****Cast in STJ neutral, MTJ fully pronated or locked and 1st ray plantarflexed (or hallux dorsiflexed) – To plantarflex 1st ray, push down over 1st met-cuneiform joint
  • If you don’t plantarflex the 1st ray, you will capture excess varus in the cast and orthotic which will lead to 1st ray dorsiflexion
  • The end result of this casting technique is to try and increase the ROM of the 1st MPJ
  • Done with a reverse Morton’s extension, for early stage I (allows 1st ray to plantarflex, but only works if the patient has a hypermobility or has an elongated 1st metatarsal)
  • NOTE: some people will have less pain with less motion, so use a Morton’s extension to limit 1st MPJ motion by preventing proximal phalanx dorsiflexion (thin carbon filler instead of orthotic)
  • Deep heel cup/UCB to prevent eversion, Kirby medial heel skive to increase supinatory torque
34
Q

Surgical intervention in later stages

A
  • Structural hallux limitus generally requires surgery
  • Surgical decision making depends on stage, patient’s age, bone stock, and activity level
  • First you need to exhaust the conservative treatment modalities (orthotics, NSAIDs, shoe gear modification)
  • If the pain and disability is affecting their lifestyle, they may be a good surgical candidate regardless of the stage they are in (doesn’t necessarily need to be a late stage)
35
Q

CASE STUDY

A
  • 64 year old male w/painful hallux limitus b/l (right > left)
  • PMH: HTN, Hypercholesterolemia
  • Objective findings
    o Vasc: DP and PT +2/4 b/l
    o Neuro: epicritic sensation intact
    o Musc: +5/5 extrinsic muscles, 1st MPJ ROM (15° left, 5° right)
  • Diagnosis: Hallux limitus with significant arthritis present in 1st MPJ (stage 3) with jamming
  • Treatment: Carbon fiber insert with a Morton’s extension and NSAIDs for 6 months (moderate relief of symptoms), 1st MPJ fusion with compression screw and plate (full symptom relief)

#4 Surg (14 decks)

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