Metatarsus Adductus (Metatarsus Varus)
- Describe the pathological anatomy of metatarsus adductus.
- Describe the presenting features including age, flexibility, symptoms, and physical findings associated with metatarsus adductus.
- Differentiate between metatarsus adductus and skewfoot.
- Discuss the natural history of metatarsus adductus.
- Describe treatment strategies for flexible and rigid metatarsus adductus.
- Describe advanced treatment strategies for older children with metatarsus adductus.
- Define any conditions that can be associated with metatarsus adductus.
Metatarsus adductus is a relatively common foot deformity of infancy or childhood where there is inward deviation of the forefoot relative to the hindfoot. Other names for metatarsus adductus in the literature include metatarsus varus, bean-shaped foot and hooked-foot. The incidence of metatarsus adductus is reported to be between 0.1 and 1 percent of live births. It is controversial whether hip dysplasia or torticollis is associated in higher frequency with metatarsus adductus.
The true cause of metatarsus adductus is not known. A “packaging problem” due to intrauterine compression is postulated but not proven. Fetal studies suggest an abnormally-shaped, trapezoidal medial cuneiform without joint subluxations. Other studies suggest subluxation of the tarso-metatarsal joints in addition to the abnormal shape of the medial cuneiform.
An infant or child presents with a fixed forefoot adductus relative to the hindfoot. The lateral border of the foot is convex and the medial border of the foot is concave. The fifth metatarsal head is prominent and the forefoot is slightly supinated. In more severe cases there is a prominent medial crease of the forefoot. The hindfoot is in slight valgus. The heelcord is not contracted.
Flexibility of the deformity needs to be assessed. In a mild deformity, stroking of the lateral border of the foot leads to active correction of the forefoot adductus. In moderate deformity, the forefoot is passively correctible by the examiner. Rigid deformities have a deep medial forefoot crease and are not passively correctible to neutral.
Families often notice intoeing during ambulation in an older child. Both internal tibial torsion and increased femoral anteversion can be seen in association with metatarsus adductus.
Radiographs of the foot show the trapezoidal shape of the medial cuneiform. Younger children show medial deviation of the metatarsals at the level of the tarso-metatarsal joint. Older children may have medial deviation of all the metatarsal shafts.
Skewfoot radiographs, on the other hand, demonstrate increased hindfoot valgus with fixed forefoot adductus and lateral subluxation of the navicular relative to the talus.
The natural history for flexible metatarsus adductus is spontaneous correction with further growth. Although passive stretching is often suggested, no studies document its effectiveness. Inappropriately aggressive treatment could lead to valgus hindfoot deformity and skewfoot.
Stretching with reverse-last shoes is typically tried in moderate or severe metatarsus adductus prior to the age of 6 months. Corrective serial casting can be useful for rigid or incompletely flexible metatarsus adductus. The typical age group for casting is 6 to 12 months. It is suggested to slightly plantarflex the foot in short leg casts to minimize the risk of producing a skewfoot. Splinting in reverse-last shoes is suggested after casting to maintain correction.
Surgery for metatarsus adductus should be rare prior to age 5. Spontaneous correction of minor forefoot adductus is likely before age 5. Persistent mild forefoot adductus into adulthood does not lead to disability. If a severe case in a young child failed earlier casting, release of the abductor hallucis with or without medial naviculo-cuneiform and cuneiform-1st metatarsal capsulotomy has been successful. Pain or shoe wear problems are the typical indications for such a procedure.
Heyman and Herndon described medial capsulotomy of the forefoot tarso-metatarsal joints with intermetatarsal ligament release. Long term follow-up studies showed a high rate of failure and complications. Multiple metatarsal osteotomies have been tried as an alternative, but injury to the first metatarsal growth plate is a known risk of the procedure.
A double tarsal osteotomy that includes a closing-wedge cuboid osteotomy and an opening-wedge medial cuneiform osteotomy has been described for the older child with symptomatic metatarsus adductus. Often the piece of cuboid bone is too small or too soft to use for the opening wedge medial cuneiform osteotomy, so allograft should be available. In particularly severe deformities, the medial cuneiform and cuboid osteotomies could be combined with multiple osteotomies of the metatarsal bases.
As with any foot surgery, painful scars can occur. Branches of the sural nerve are especially at risk during exposure of the cuboid. Damage to the growth plate of the first metatarsal can lead to brachymetatarsia or angular deformity. Release of the medial capsules of the tarso-metatarsal joints has fallen out of favor due to high rate of recurrence. Hallux valgus can occur after release of the abductor hallucis. Overzealous casting or splinting of mild metatarsus adductus can lead to increased hindfoot valgus and skewfoot deformity.
- Metatarsus adductus is common and often will spontaneously correct.
- Casting for 6 to 12 month olds with more severe forms of metatarsus adductus is helpful.
- Surgery is rarely performed prior to age 4 or 5 years old.
- Release of an overactive abductor hallucis may be beneficial.
- An opening-wedge medial cuneiform osteotomy combined with a closing wedge cuboid osteotomy is beneficial in an older child with significant metatarsus adductus.
More in Depth Knowledge of Metatarsus Adductus for the Expert
Management of metatarsus adductus associated with previous clubfoot treatment.
- Management of a skewfoot that developed from metatarsus adductus.
- Management of complications associated with surgical treatment of metatarsus adductus.
- Any role for Ilizarov method in rigid forms of metatarsus adductus or skewfoot.
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Figure 1A. Previous osteotomies of all five metatarsals for metatarsus adductus. Patient complains of severe pain over left hallux valgus deformity.
Figure 1B: Successful first metatarsal-phalangeal joint arthrodesis with resolution of symptoms.
Figure 2A: 7 year old with previous clubfoot surgery on left foot with symptomatic metatarsus adductus.
Figure 2B: Successful left opening wedge medial cuneiform osteotomy and closing wedge cuboid osteotomy.