Practice Essentials
Since the advent of shoes, the fifth toe has been a source of discomfort for many people. Complaints typically involve poorly fitting shoes that create friction, irritation, and pain with each step. The problem can typically be solved conservatively with shoe modifications or proper foot maintenance; however, structural deformities of the toe often require surgical correction.
Fifth-toe deformities comprise several congenital and developmental problems that affect the fifth digit. [1] Most are associated with contractures at the metatarsophalangeal (MTP) joint (MTPJ) and the proximal interphalangeal (PIP) joint (PIPJ), with or without varus rotation. [2]
Although fifth-toe deformities have long been recognized, correction of these deformities did not become prevalent until the early 20th century, when many authors began describing different aspects of the problem, along with surgical procedures to help correct them (see Treatment).
Medical therapy is commonly considered conservative care. Surgical correction is indicated for chronically painful hard and soft corns in cases where conservative treatment fails. Patients with neuropathy may also choose surgery for prophylaxis against chronic lesions. Surgical correction is also indicated for progressively painful hammertoes or over- or underlapping toes if conservative treatment fails.
Surgical therapy depends on the type and level of the deformity. Angular deformities can be corrected with a combination of bone cuts and derotational skin incisions. Areas with contracted skin or tendons may require lengthening procedures, tenotomy, or both.
For patient education resources, see Corns and Calluses.
Anatomy
Three bones make up the fifth toe: the distal, middle, and proximal phalanges. They articulate together to make the distal interphalangeal (DIP) joint (DIPJ) and the PIPJ. The proximal phalanx then articulates with the fifth metatarsal to make the fifth MTPJ. Medial and lateral condyles are present at the base of each phalanx, and epicondyles are present at the heads of the proximal and middle condyles.
A two-boned (biphalangeal) fifth toe has been reported in 37-76% of the population and involves a union of the distal and middle phalanges. When this occurs, the fifth toe is less flexible and often unable to accommodate pressure from standard shoes. This variant is more susceptible to irritation and may develop into a painful deformity. [3]
In a descriptive prospective study of 2494 feet in 1247 people, Gallart et al reported that a biphalangeal fifth toe was present in 46.3% of the feet and was bilateral in 97.4% of these cases. [4] The percentage of pathologic toes was significantly higher in patients with triphalangeal fifth toes (29.91%) than in those with biphalangeal toes (15.60%). The authors suggested that there may be an association between pathologic deviations and the greater mobility of triphalangeal fifth toes and that the greater rigidity of biphalangeal fifth toes may lead to lesser accommodation inside the shoe, which might result in less painful feet and decreased need for surgery.
In a cross-sectional obervational study, Ucpunar et al compared the incidence of biphalangeal fifth toe in 672 patients with foot deformities with that in 332 control subjects. [5] They found no significant difference in incidence between the two groups (33% in the foot deformity group vs 31.9% in the control group).
The MTPJ has an extensor wing-and-sling mechanism that aids in extension of the digit. A slip of the extensor digitorum longus (EDL) to the fifth toe travels deep to the extensor wing and sling to insert into the dorsal aspect of the distal phalanx. No slip occurs from the extensor digitorum brevis (EDB) to the fifth toe; however, an occasional anomaly takes place in which an offshoot from the peroneus brevis tendon travels distal to insert into the dorsal-lateral aspect of the fifth MTPJ.
The fourth lumbrical muscle inserts into the plantar-medial fibers of the extensor wing to help adduct and plantarflex the proximal phalanx. The intrinsic third plantar interosseous and flexor digiti quinti brevis muscles insert into the plantar-medial and lateral aspects of the proximal phalanx respectively and function to stabilize the MTPJ against the stronger extrinsic flexor digitorum longus (FDL) and EDL. The abductor digiti minimi originates from the calcaneus and inserts into the plantar-lateral aspect of the proximal phalanx to place an abductory force on the toe.
The final two muscles to affect the fifth digit are the FDL and the flexor digitorum brevis (FDB), both of which plantarflex the toe. The FDL is deep to the FDB until the PIPJ, where the FDB splits, allowing the FDL to become superficial and continue distally to insert into the plantar portion of the distal phalanx. The FDB then rejoins to insert into the plantar aspect of the middle phalanx.
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Fifth-toe deformities. Example of hard corn. They commonly occur on dorsal lateral aspect of proximal interphalangeal joint but can also occur in same location over distal interphalangeal joint.
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Fifth-toe deformities. Example of soft corn deep in web space. Intrinsic pressure develops between adjacent condyles of lateral fourth proximal interphalangeal (PIP) joint (PIPJ) abutting medial fifth distal interphalangeal (DIP) joint (DIPJ), or lateral fourth metatarsophalangeal (MTP) joint MTPJ) abutting medial fifth PIPJ. Lesions can develop on skin over lateral fourth PIPJ, medial fifth DIPJ, medial fifth PIPJ, or deep in web space.
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Fifth-toe deformities. This image and image below are examples of kissing corns. They are two calluses that rub against each other on adjacent toes and are usually painful when squeezed together.
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Fifth-toe deformities. Example of kissing corn. These corns are two calluses that rub against each other on adjacent toes and are usually painful when squeezed together.
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Fifth-toe deformities. This image and image below are further examples of kissing corns. Maceration is often noted in web space and may contribute to their development. When they occur, other common problems, such as fungal infections or verruca, must be ruled out. These lesions may develop into ulcerations in neuropathic population if untreated, as is seen in this case.
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Fifth-toe deformities. Example of kissing corns. Maceration is often noted in web space and may contribute to their development. When they occur, other common problems, such as fungal infections or verruca, must be excluded. These lesions may develop into ulcerations in neuropathic population if untreated, as is seen in this case.
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Fifth-toe deformities. Example of hammertoe with dorsiflexion contracture at metatarsophalangeal joint and plantarflexion contracture at proximal interphalangeal joint. Note irritated skin secondary to shoe pressure.
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Fifth-toe deformities. This image and image below represent an overlapping fifth toe. It is dorsally hyperextended at metatarsophalangeal (MTP) joint (MTPJ) with varus rotation and medial deviation onto top of fourth digit. Contractures develop dorsomedially at MTPJ and eventually form in extensor digitorum longus tendon and dorsomedial skin overlying MTPJ.
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Fifth-toe deformities. Overlapping fifth toe is dorsally hyperextended at metatarsophalangeal (MTP) joint (MTPJ) with varus rotation and medial deviation onto top of fourth digit. Contractures develop dorsomedially at MTPJ and eventually form in extensor digitorum longus tendon and dorsomedial skin overlying MTPJ.
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Fifth-toe deformities. This image and image below are examples of underlapping fifth toe, or curly toe. It is plantarflexed at metatarsophalangeal (MTP) joint (MTPJ), rotated into varus position, and positioned under fourth digit. Contracture typically occurs at the plantar-medial MTPJ capsule and flexor digitorum longus tendon.
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Fifth-toe deformities. Underlapping fifth toe, or curly toe. It is plantarflexed at metatarsophalangeal (MTP) joint (MTPJ), rotated into varus position, and positioned under fourth digit. Contracture typically occurs at plantar-medial metataMTPJ capsule and flexor digitorum longus tendon.
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Fifth-toe deformities. This radiograph shows prominent fifth-toe proximal phalanx medial condyle contacting base of proximal phalanx on fourth toe, creating increased pressure and interdigital clavi.
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Fifth-toe deformities. This radiograph shows distal phalanx of varus-rotated fifth toe contacting proximal phalanx on fourth toe, creating another area of increased pressure and interdigital clavi.
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Fifth-toe deformities. This image and following three images demonstrate surgical course for severe fifth digit cock-up deformity. Note dorsal contracture in this preoperative photo.
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Fifth-toe deformities. Planned incision with arms for Z-plasty skin-lengthening flap drawn in. Central arm of Z-plasty is along line of skin contracture.
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Fifth-toe deformities. Exposure showing severely contracted extensor digitorum longus tendon. This is lengthened during procedure.
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Fifth-toe deformities. Postoperative photo showing corrected fifth digit.
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Fifth-toe deformities. This image and following images demonstrate operative technique for painful overlapping fifth-toe deformity.
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Fifth-toe deformities. Painful overlapping fifth-toe deformity.
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Fifth-toe deformities. When toe is derotated and plantarflexed into correct position, dorsal skin "tents up," showing exact location of skin contracture.
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Fifth-toe deformities. In this case, Z-plasty is performed to lengthen contracted skin. Length is achieved along central arm of the "Z" so it is placed along the line of contracture. Adjunctive procedures such as metatarsophalangeal joint release and extensor digitorum longus tendon lengthening should be performed through same incision. Alternative to Z-plasty is V-Y flap.
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Fifth-toe deformities. After rotation of Z flaps and soft-tissue release, toe is reevaluated. Toe is down, and proximal phalanx is in excellent position, but distal portion of toe has varus rotation at proximal interphalangeal (PIP) joint (PIPJ). PIPJ arthroplasty with derotational skin plasty is then performed to address this portion of deformity.
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Fifth-toe deformities. This image and image below were taken 5 days postoperatively with contractures addressed and toe in good position.
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Fifth-toe deformities. Five days after surgery, contracture is addressed and toe is in good position.
