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Disorders of the lesser toes

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The position of the proximal phalanx in the metatarsal-phalangeal joint is determined by the balance between the extensor digitorum longus and the intrinsic muscles. The position of the middle and distal phalanges at the interphalangeal joints is determined by the pull of the flexor digitorum longus and brevis and opposed by intrinsic muscles (Figure 1).

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Figure 1: Bony structures of the foot (from www.infovisual.info Volume 3, Human Body)

The degree of hyperextension and flexion of the MTP, PIP, and DIP joints can help distinguish between claw toe, hammer toe, and mallet toe (Figure 2). 

Table 1: Common Toe Deformities
ConditionMTP JointPIP JointDIP Joint
Claw toeHyperextendedFlexedFlexed
Hammer toeMay or may not be hyperextendedFlexedHyperextended
Mallet toeExtendedExtendedFlexed


 

Figure 2: Common deformities of the lesser toes (from Myerson et al. PMID: 2913002)

Claw toes are primarily due to an inherent muscle imbalance where the extrinsic foot muscles (originating from the lower leg) overpower the intrinsic muscles in the foot, causing flexion at the PIP (proximal interphalangeal) joint and extension at the MTP (metatarsal phalangeal) joint. The flexed PIP joints are constantly irritated by shoes, leading to painful calluses on the top dorsal aspect of the toes (Figure 3).

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Figure 3: Claw toes. The second toe is usually the most pronounced deformity, but all four lesser toes demonstrate clawing. 

Acquired causes of claw/hammer/mallet toes most commonly involve ill-fitting or restrictive shoes that gradually bend the toes into a fixed position when worn for long periods of times. These toe Toe deformities can also occur post-traumatically, due to injury of one of the tendons or from compartment syndrome of the small muscles of the foot. 

Claw toes can be a permanent deformity and can be symptoms of a more serious disease of the nervous system.Typically, when only one toe is affected (typically the second toe), external pressure (from the shoe), trauma, or arthritis should be considered. If all the toes are involved, an underlying neuromuscular cause should be considered. 

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On physical exam, each joint should be assessed as to whether they can return to its normal position (checking to see whether the toes toe deformities are flexible or fixed affects the treatment options). This is done by the push up test: with the ankle in a neutral position, put fingers beneath the metatarsal head and push dorsally to see if the deformity corrects. Additionally, if the deformity is worse during the swing phase of a patient’s gait, it may indicate weak ankle dorsiflexors and overcompensating toe extensors; if the deformity is worse during stance phase, it may indicate weak triceps surae and overcompensating long toe flexors.

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Differential diagnosis

Underlying etiologies or associated conditions include:

  1. diabetes, or other peripheral neuropathy (check fasting glucose to exclude)
  2. rheumatoid arthritis, or psoriasis (check RF)
  3. neuromuscular imbalance (poliomyelitis, peroneal muscle atrophy, Freidrich's ataxia, idiopathic pas cavus, myelopathy, radicular neuropathy, multiple sclerosis)
  4. Charcot Marie Tooth Disease (review family history, conduct nerve conduction studies if suspected)
  5. synovitis, osteomyelitis
  6. bunions, flat feet, or pes cavus deformity (highly arched feet)
  7. peripheral vascular disease

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Non-operative
Most deformities can be treated non-operatively , including:

  • applying pads to the areas of prominence

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  • using a shoe with a wide-toe box to accommodate the deformity and alleviate pain

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  • using a soft, pre-fabricated orthotic to create cushioning over the toe region

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  • trimming painful calluses.

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  • exercises to increase intrinsic muscle strength (such as picking up tissues with the toes) has been proposed to lessen the progression of the deformity.

Operative

Surgery is considered in deformities that cannot be corrected non-operatively. 

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  • Flexor to extensor tendon transfertransfer to extensor hood at proximal phalanx
  • Capsular release, EDB tenotomy plus EDL lengthening

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Hammer Toes

Flexible deformity:

  • Split FDL transfer  Flexor to extensor tendon transfer to extensor hood at proximal phalanx
  • FDL  tendon will now plantar flex MTP joint and extend IP joints

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As with any surgery, there is a risk of wound healing problems, infections, local nerve injury that affects sensation, DVT (deep vein thrombosis) and subsequent pulmonary embolism–though these last two are very rare. Specific to toe correction surgeries, complications include: 

  • Malunion: It is common for the toe to heal in a position that may not be perfectly straight. Minor degrees of deformity will be mostly a cosmetic concern, which is why almost all surgeons discourage patients from having toe surgery if the concerns are mostly cosmetic. In severe cases, the toe may be significantly malpositioned even to the point where further surgery is required.
  • Recurrence of the Deformity: Other complications include failure Failure to fully correct the claw toe deformity or the potential for recurrence of the deformity over time is another potential complication.
  • Loss of blood supply to the tip of the toe. : The blood supply to the tip of the toe can be tenuous. There are two small arteries (one on either side of the toe) which supply blood to the tip of the toe. It is not uncommon for one of these vessels to be absent. If the blood supply to the tip of the toe is lost the tissue will die and it may be necessary to amputate part, or all of the toe.

Key terms

claw toe, hammer toe, mallet toe, Metatarsalgia, callusescorns, push up test, muscular imbalance

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