Overriding fifth (5th) toe

Congenital overlapping or underlapping toes:

• study evidence reveals (1)
  • most common abnormal toes were the fifth underlapping toes (79%), with a roughly equal distribution of left and right feet
  • second most common toe abnormality was that of multiple toes (all fourth under-lapping and fifth overlapping) at 16%
  • other toe abnormality recognized was that of overlapping toes (4%, all fifth toes)
  • abnormalities of the fourth toe were uncommon (3%) and all were underlapping

The fifth toe lies transversely across the fourth toe.

• overlapping fifth toe is a common congenital deformity in children
  • thought to be a congenital deformity characterized by the proximal phalanx dorsally subluxating and adducting on the fifth metatarsophalangeal joint
    • overlapping fifth toes - not infrequently this deformity may be painful and disabling in both the pediatric and adult population. Paediatric overlapping fifth toe often corrects with normal ambulation and physicians only need to intervene if symptomatic deformity persists
  • both sides are affected in about 25% of patients and familial aggregation is common, although the cause of this condition remains unknown. Additional forefoot deformities or neurological abnormalities are often present and should be sought routinely (3)
  • the initial abnormality responsible for the deformity involves the soft tissues
    • tightness of the dorso-medial capsule and ligaments, together with brevity of the extensor tendon of the fifth toe, results in irreducible dorso-medial subluxation of the fifth metatarso-phalangeal (MTP) joint
    • more superficially, the skin at the base of the fourth web space is abnormally tight
    • fifth toe is fixed in hyperextension, varus, and external rotation and consequently overlaps the fourth toe
  • some patients also have bone deformities, such as valgus of the fifth metatarsal producing a lateral bump that rubs against the shoe
    • minor abnormalities are found in some cases (e.g., nail dystrophy or toe hypoplasia)
  • 25% of these toes would correct and be considered cured without intervention (1)

This deformity makes shoes difficult to wear.

Management:

• nonoperative optimization with strapping, splinting, and shoe modification would be reasonable first-line treatments
  • a technique for taping applied in the newborn resulted in improvement or cure in 94% of children with common congenital toe abnormalities (1)
• surgical intervention including osteoclysis, percutaneous tenotomy, capsulotomy, syndacilization, tissue rearrangements, tendon transfers, phalangectomy, and toe amputation are indicated only after optimization of less invasive measures

Notes:

• underlapping fifth toe (or "curly" toe) deformity is also felt to be congenital
  • in most cases, underlapping fifth toes are noticed by parents and family members early in infancy
  • the proximal phalanx in underlapping toes is typically in varus at the metatarsophalangeal joint with flexion
  • not uncommon for a rotational malalignment to be present (supination/pronation) as judged by the nailbeds.
  • similar to overlapping toes, paediatric underlappers commonly correct with reassurance and benign neglect up to age 6 years
    • intervention is warranted in the setting of persistent pain and footwear difficulty. Accommodative shoes, absorbing cushions, and functional modification are the mainstays of nonoperative management
    • operative intervention may consist of osteoclysis, percutaneous flexor tenotomy, capsulotomy, tissue rearrangements, tendon transfers, removal of symptomatic spurs, osteotomies, and amputation.

Reference:

• Smith WG et al. Prospective study of a noninvasive treatment for two common congenital toe abnormalities (curly/varus/underlapping toes and overlapping toes). Paediatr Child Health. 2007 Nov;12(9):755-9.
• Talusan PG et al. Fifth toe deformities: overlapping and underlapping toe. Foot Ankle Spec. 2013 Apr;6(2):145-9.
• Murgier J et al. Percutaneous correction of congenital overlapping fifth toe in paediatric patients. Orthop Traumatol Surg Res. 2013 Oct;99(6):737-740.