Fifth toe deformities: overlapping and underlapping toe.

UNLABELLED: Overlapping fifth toe is thought to be a congenital deformity characterized by the proximal phalanx dorsally subluxating and adducting on the fifth metatarsophalangeal joint. Overlapping fifth toes may present as asymptomatic figments of parental concern, but not infrequently this deformity may be painful and disabling in both the pediatric and adult population. Pediatric overlapping fifth toe often corrects with normal ambulation and physicians only need to intervene if symptomatic deformity persists. Nonoperative optimization with strapping, splinting, and shoe modification would be reasonable first-line treatments. 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. 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. It is not uncommon for a rotational malalignment to be present (supination/pronation) as judged by the nailbeds. Similar to overlapping toes, pediatric underlappers commonly correct with reassurance and benign neglect up to age 6. 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. After exhaustive review of the published literature, it is clear that fifth toe deformities (whether overlapping or underlapping) have not been extensively studied. No gold standard approach exists in treatment. Prospective research using larger numbers of patients with detailed outcome metrics are needed. Surgeons should carefully tailor surgical intervention to patient specific pathology.

LEVELS OF EVIDENCE: Expert Opinion, Level V.