Hallux Limitus

See: Hallux rigidus/functional hallux limitus

An osseous or functional deformity of the first MPJ in the sagittal plane, in which there is an inability of the proximal phalanx to dorsiflex on the head of the first metatarsal, leading to limited MPJ dorsiflexion during propulsion.

Terminology is often vague and often used interchangeably in the literature, but should be:
Types:
1) Structural hallux limitus - insufficient MPJ dorsiflexion for normal function
2) Hallux rigidus - no MPJ dorsiflexion is available (often used synonymously for osteoarthritis in the first MPJ)
3) Functional hallux limitus – normal ROM when nonweightbearing, but a functional; limitation when walking.

For normal function, 600-650 dorsiflexion is considered the normal requirement during propulsion in the sagittal plane. This motion requires first ray plantarflexion. Without this plantarflexion, the hallux may only be able to dorsiflex up to 25 degrees. The plantarflexion of the first ray changes the location of the transverse axis of motion of the first MPJ from near the centre of the metatarsal head to a more proximal and dorsal position. This allows the base of the proximal phalanx to move dorsally on the first metatarsal head. The normal range of motion at the first MPJ is also needed in gait to establish a ‘stable’ foot via the windlass mechanism.

Aetiology:
Many disease states will cause the range of motion to be restricted at the first MPJ, as well as any functional or structural problem that restricted first ray plantarflexion.

• Footwear/orthoses/padding – rigid soles, high heels, excessive medial forefoot posting or padding (all prevent first ray plantarflexion or MPJ dorsiflexion)
• Metatarsus primus elevatus (prevents first ray plantarflexion)
• Long first metatarsal (prevents first ray plantarflexion)
• Hypermobile first ray (secondary to excessive subtalar joint pronation)
• Immobile first ray (prevents first ray plantarflexion)
• Degenerative joint disease (eg osteoarthritis) (common cause of hallux rigidus)
• Trauma – most common cause of structural hallux limitus and hallux rigidus
• More common in those who are obese
• First metatarsal head shape
• tight medial band of plantar fascia
• Idiopathic (a large number of functional hallux limitus cases have an unknown aetiology)

Pathomechanics:
Root et al (1977):
Subtalar joint pronation leads to dorsiflexion and inversion of the first ray, however normal MPJ dorsiflexion requires first ray plantarflexion during propulsion. Excessive or prolonged subtalar joint pronation increase the dorsal joint compression force at the first MPJ resulting dorsal exostosis formation on the first metatarsal head with a subsequent restriction in the range of motion.

Root et al (1977) also state that the amount of forefoot adductus with hypermobility of the first ray will determine if people develop a hallux limitus or a hallux abducto valgus. Those with a lessor amount of forefoot adductus are more likely to develop hallux limitus, whereas those with a higher amount of forefoot adductus are more likely to develop HAV.

Dananberg (1986):
Functional hallux limitus causes compensatory motions and is not the result of excessive pronation. A structural or functional hallux limitus will cause compensatory pronatory motion at the subtalar and midtarsal joint during propulsion.

Clinical Features:
A structural hallux limitus will often progress to a hallux rigidus, depending on the aetiology.
Predominant symptoms at the joint are progressive stiffness and pain at the first MPJ – may be worse in morning and after activity. Pain is usually present in both shod and unshod conditions. The pain may only be on palpation of the dorso-lateral aspect of the joint. Eventually develop a dorsal exostosis.
There may be no symptoms at the first MPJ, but significant symptoms from the compensations in the gait pattern for a structural or functional hallux limitus.

Shoe wear pattern typically show excessive wear in central region of forefoot and under the hallux (less wear under first metatarsal head).

Range of motion:
1) Hallux rigidus – none
2) Structural hallux limitus – restricted
3) Functional hallux limitus – normal range of motion of weightbearing, but generally have a restricted range of motion if the first ray is prevented from plantarflexing (normally should get 5 – 10 degrees when he first ray is immobilised)

The dorsal exostosis can cause shoe fitting problems, hyperkeratosis, ulceration or a dorsal digital nerve entrapment. The shoe will tend to be more worn on lateral forefoot and distal hallux. The interphalangeal joint usually becomes hyperextended, resulting in hyperkeratosis plantar to the IPJ and a subungual haematoma of the hallux nail. Hyperkeratosis is usually found on the plantar to the lessor metatarsal heads and on the medial plantar aspect of the hallux IPJ.

Gait analysis:
The compensatory motions can be seen (eg midtarsal joint pronation during heel off)

Radiographic changes:
Flattening of the first metatarsal head; wider first metatarsal head; decreased joint space; subchondral cysts; sesamoid hypertrophy; loose bodies in joints

Compensation pattern for Hallux Limitus:
When there is a block in motion in the sagittal plane at the first MPJ, a number of compensations can be observed:
• Heel lift is delayed, due to compensatory pronation at the midtarsal joint
• Eventually the propulsive phase is avoided and the foot is just lifted of the ground
• During gait the centre of pressure lines tends to move laterally, causing a lateral increase in plantar pressures
• To get around the limitation in the first MPJ, the gait may be abducted or adducted
• A flexion compensation of the knee and spine is noted during the propulsive phase.

Classification of Hallux Limitus:
Vanore et al (1989):
Grade 1- Stage of Functional Limitus
• Plantar subluxation of the proximal phalanx
• Metatarsus primus elevatus
• Pronatory architecture
• Joint dorsiflexion may be normal with nonweightbearing but ground reactive forces elevate the first metatarsal and yield limitation
• no osteoarthritis
• interphalangeal joint is hyperextended
• may be painful at end range of motion

Grade 2 – Stage of Joint Adaptation (the development of proliferative and destructive joint changes)
• Flattening of the first metatarsal head
• Osteochondral defect/cartilage erosion
• Pain on end range of motion
• Passive range of motion limited
• Small dorsal exostosis
• Subchondral eburnation
• Periarticular lipping of both the proximal phalanx and first metatarsal head

Grade 3 Stage of Joint Deterioration/Arthritis (or established Arthrosis)
• Severe flattening of the first metatarsal head
• Osteophytosis, particularly dorsally
• Nonuniform narrowing of the joint space. Degeneration of articular cartilage
• Crepitus
• Subchondral cysts
• Pain on full range of motion
• Associated inflammatory arthritis

Grade 4 – Stage of Ankylosis
• Obliteration of joint space
• Loose bodies within joint space or capsule
• Less than 10 degrees range of motion
• Deformity and/or malalignment
• May see total ankylosis

Management:
Conservative:
• Lesion reduction, pressure relief
• Physical therapy, pain relief
• Mobilisation and manipulation
• Rigid full length insole to prevent dorsiflexion of MPJ
• Shoe modification (external rockers for structural – BUT these will prevent restrict first MPJ dorsiflexion in a structural hallux limitus)
• Orthoses – control STJ pronation and assist in first ray plantarflexion  not indicated for a structural functional hallux limitus

Surgical:
• First MPJ fusion
• Cheilectomy (removal of hypertrophic bone)
• Shortening of the first metatarsal
• Release of medial band of plantar fascia
• Plantarflexion osteotomy
• Implant arthroplasty

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