“Sickle foot” is the common term for Metatarsus Adductus (MA), one of the most frequently observed congenital foot deformities in newborns. This condition causes the front part of the foot to curve inward, resembling a crescent shape. MA is highly treatable and typically benign, occurring in approximately one to two out of every 1,000 live births. The vast majority of cases resolve spontaneously or with straightforward intervention.
Anatomy and Appearance of Sickle Foot
Metatarsus Adductus is localized to the forefoot, where the metatarsals turn inward toward the midline of the body. The ankle and heel (hindfoot) remain in a normal, straight alignment. This results in a distinct, C-shaped curve along the outer edge of the foot.
Other signs can include a prominent bump on the outer side of the midfoot and a noticeable separation between the great toe and the second toe. The condition is classified based on flexibility when examined. Flexible MA is the most common type and can be manually straightened with gentle pressure, indicating the foot is molded without a fixed structural change. Rigid (non-flexible) MA cannot be easily corrected with passive manipulation.
Root Causes and Diagnosis
The precise cause of Metatarsus Adductus is not definitively known, but the prevailing theory points to positional constraint within the uterus. This “intrauterine packaging” suggests that limited space and pressure, especially during the later stages of pregnancy, molds the developing foot. The condition is observed more often in firstborn children, supporting the constraint theory.
Diagnosis relies on a thorough physical examination immediately after birth; imaging is rarely necessary. The physician performs a passive manipulation test, holding the heel steady while gently trying to straighten the forefoot. The degree to which the forefoot moves past the neutral position determines the severity, often graded from mild to severe (Type I, II, or III). X-rays are generally reserved for non-flexible or severe cases to rule out other structural deformities.
Management and Long-Term Outlook
Management is tailored to the foot’s flexibility and severity. Mild, flexible cases often require only observation, as many correct themselves spontaneously. For moderate, flexible cases, parents are instructed in home stretching exercises. These involve gently manipulating the forefoot to align it with the heel, performed multiple times daily.
If the foot is rigid or does not respond to observation and stretching, the next step is serial casting. This non-surgical approach involves applying a series of casts, changed every one to two weeks, to gradually stretch soft tissues and realign the forefoot bones. This intervention is most effective before the infant is nine months old.
Once alignment is achieved, a specialized brace or straight-last shoe may be used temporarily to maintain the correction. The long-term outlook is positive. The deformity rarely causes lasting disability or pain into adulthood. Success rates for non-operative treatment, including casting, are reported to be over 90 percent.