Hammer Toe

Hammer Toe

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A sagittal plane deformity of the toe where the proximal interphalangeal joint (PIPJ) is flexed, the distal interphalangeal joint (DIPJ) is in a neutral or extended position and the metatarsophalangeal joint (MPJ) is neutral or dorsiflexed.

Aetiology:
Inappropriate footwear - (narrow toe box, inadequate depth of toe box, too short, too small)
Associated with hallux abducto valgus
Familial predisposition/inherited factors
Neuromuscular disorders
Short hallux
Instability of the foot during propulsion  flexor stabilisation (could be most common cause)
Short or plantarflexed metatarsal
Imbalance between medial and lateral interossei

Pathomechanics
Short metatarsal:
A short metatarsal will have to plantarflex to reach the ground. This will result in an associated dorsiflexion of the proximal phalanx when the flexors contract  hammer toe

Short hallux:
A short hallux will expose the second toe to the footwear to a greater extent creating a backward pressure on the digit. This will result in dorsiflexion of the proximal phalanx and plantarflexion of the metatarsal.

Hallux abducto valgus:
The abductory force from the hallux results in a muscle imbalance and hammering of the toe.

Muscle malfunction:
If the lumbricals are weak the toe will hammer

Plantarflexed ray:
If the metatarsal is plantarflexed the proximal phalanx will be forced to dorsiflex.

Imbalance between medial and lateral interossei:
These muscles normally exert equal and opposite forces on the digits to stabilise them in the transverse plane. If there is an imbalance, the digit will be less stable and hammer when the toe flexors contract.

Clinical Features:
Important to classify the deformity as flexible or rigid – due to the consequences of a restricted range of motion.
Many are asymptomatic.
Pressure from footwear may cause bursal development over the PIPJ. Associated with the bursa may be a fistula and sinus.
May be hyperkeratotic lesions associated with the pressure on PIPJ and apex of joint. Plantar lesions may develop due to the retrograde force.
May be pain secondary to arthritic changes

Management:
Treat inflammatory states and reduce hyperatotic lesions.
Protective padding if fixed.
Corrective padding or splints if flexible
Orthodigital devices.
Footwear advice – deeper toe box

Surgical:
• Fusion of the IPJ in a slightly flexed position
• Dorsiflexion osteotomy of a plantarflexed ray
• Surgical correction of HAV
• Tendon transfers
• Removal of bony segments – resection of proximal interphalangeal joint
• Soft tissue procedures to release contractures
• K-wire insertion/fixation.

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