Deformities and angular variations of the lower extremities are one of the most common reasons for referral to pediatric orthopedics, with in-toeing seen mostly in infants and young children. Also known as “pigeon-toeing,” this is caused by a rotational variation anywhere in the lower extremity that causes the foot to point inward.
In coming to understand variational pathologies of the lower limb, it is important to be familiar with the normal growth and development of children’s lower extremities. Neonates are born with about 40 degrees of femoral anteversion or forward rotation of the femoral neck. This increased internal rotation of the hip decreases over time. By about 10 years old, the degree of anteversion decreases by about half. Any deviation from the expected course of limb development and rotation should be recognized and differentiated from the persistence of early angulation, to pathologies preventing normal rotation.
The 3 major causes of pediatric in-toeing are metatarsus adductus, internal tibial torsion, and femoral anteversion. Each has unique typical findings and age of presentation. Other causes to keep in mind as differentials will be discussed below.
The most common condition in children younger than one year of age is metatarsus adductus. It is seen between 0.1% to 1% of births, and more frequent in girls compared to boys.
Between the ages of 1 and 4 years, the most common condition causing in-toeing is internal tibial torsion. There is no gender predilection or attributable cause.
Increased femoral anteversion is the third common cause of in-toeing in children. This can present during infancy but typically is notably after the age of 3, with an average age of diagnosis between 3 and 6 years of age. This condition is twice as common in females.
Metatarsus adductus is attributed to intrauterine positioning, and defined as angulation of the metatarsals toward the midline, giving the appearance of a "C" shaped foot.
The tibia is normally internally rotated at birth, but there are wide variations in the amount of angulation.
Femoral anteversion is also brought about by increased intrauterine pressures, causing undue pressure in areas of growth. In these cases, the neck of the femur is rotated inwards, which rotates the greater trochanter posteriorly. The resulting in-toeing becomes more evident with age, as there is a physiologic external rotation of the hip during toddler development.
Physical examination should include inspecting the entire lower extremity, with particular attention to the hip/femur, the knee/tibia, and the feet. The patient's gait should be assessed while walking and while running, as age and developmentally appropriate.
Metatarsus adductus is the adduction of the forefoot, with varying degrees of flexibility. Classifications of metatarsus adductus are based on the degree of foot flexibility. Mild is the most flexible, with the patient self-correcting after stimulation of the foot. Moderate requires passive flexion by the examiner, and severe cases are unable to be corrected either actively or passively. If a line were drawn from the heel going toward the toes (heel bisector line), normal alignment of the foot would go down the second toe. Patients with metatarsus adductus will have the line bisect the more lateral toes, with the higher severities crossing with increasingly lateral.
In patients with tibial torsion, the tibia is found to be internally rotated (medial rotation of the shin). Internal tibial torsion is most frequently bilateral, and may at times present with metatarsus adductus, femoral anteversion, or physiologic bow legging. Pertinent clinical findings on examination include a forward or outward-facing patella, or in a seated position, there may be a posterior rotation of the medial malleolus (in comparison to the lateral malleolus). The last notable clinical finding on examination is the thigh-foot angle (TFA). With the patient in prone position and the knees flexed, the TFA can be assessed by the degree of angulation of the foot towards or away from the midline. Expected variation is an angle between 10 to 15 degrees.
On the physical examination of femoral anteversion, the patella is midline when walking or standing but point inward when running. The characteristic appearance during running is described as a “windmill” or “egg-beater” pattern, in which the patient’s lower leg pushes off and swings laterally when coming off the ground. While seated, the patient tends to prefer sitting in the “W” position, appearing to mount the floor with knees forward, and feet facing posteriorly. The discomfort and distaste these patients have for lateral rotation improve with time, evident by them showing improved comfort in being able to sit cross-legged.
Diagnosis is made clinically with no need for imaging. The only indication for radiography would be for potential surgery with severe cases of metatarsus adductus. Outside of this, the utility in radiologic studies would be in excluding pathologic conditions.
A majority of cases are managed primarily by observation with emphasis placed on parental reassurance. Metatarsus adductus is expected to resolve by 2 years of age, and any persistence is not associated to have any symptomatology. Rigid and severe metatarsus adductus with no flexibility should be referred for possible serial casting.
Those with tibial torsion should be reassured that it is normal for developing children to have increased internal angles as they grow in age. Physiologic progression slowly returns somewhat towards the midline after the second decade. Again, parental reassurance is emphasized, as the patient is observed for spontaneous resolution by 5 years of age. Like metatarsus adductus, it is uncommon to have chronic issues with any persistence of internal tibial torsion. Rare cases that cause cosmetic or functional deformities may be considered for surgical correction by a distal tibial derotational osteotomy.
Akin to the other common physiologic conditions mentioned above, the natural course for femoral anteversion is also spontaneous resolution over time. Femoral anteversion has the longest course, resolving around 11 years of age. Persistence may also be seen in a small number of patients, with the rare likelihood of developing symptoms or complications. The mainstays of management are observation and to reassure parents of the natural course of decreasing anteversion. There are no recommended non-operative treatments, and the only notably effective surgical management is femoral derotational osteotomy. Becuase of the high likelihood of complications from surgery, it is only considered for those older than 11 years old, with severe functional sequelae or cosmetic deformities.
The bulk of causes of in-toeing are most often secondary to physiologic conditions that resolve over time. It is important to elicit pathologies in the history and physical examination to rule out the less common conditions that may present similarly. As mentioned above, developmental dysplasia of the hip can be associated with metatarsus adductus but can present as an isolated finding as well. Careful follow-up and timely imaging can differentiate between the physiologic laxity of the hip and normal hip development, versus hip dysplasia. Deformities of the lower leg can be distinguished from the common physiologic causes through a detailed physical examination. Clubfoot is a foot deformity that is associated with multiple foot findings, including plantarflexion (cavus), adductus, varus, and equinus, made memorable by using the mnemonic CAVE. Secondary causes due to underlying conditions can include cerebral palsy or other neuromuscular diseases. These conditions should be considered when the physical exam is notable for other findings outside of the lower extremities.
As mentioned above, the overall prognosis of the three pathologies is good, with their respective time frames for resolution.
Direct complications are uncommon, but the interplay between possible associations between the conditions should be considered. Metatarsus adductus is attributed to intrauterine positioning, and the clinician should be aware that other comorbidities associated with intrauterine positioning include torticollis and developmental dysplasia of the hip, which is commonly bilateral.
Although one study found that 86% of children referred to orthopedic surgery by their primary physician were discharged after the initial visit, a referral may be indicated for particular circumstances, such as limitation in activity, cosmetic concerns, or courses of in-toeing that do not progress as expected.
The mainstay of management is regular follow-up with the primary care physician for observation and family reassurance. Family members may be familiar with previous modalities used for in-toeing, ranging from bracing, orthotics, shoe modifications, and splinting at night. Families should be reassured of the natural course of lower limb development with the above interventions not recommended for these conditions.
In assessing patients with in-toeing, it is important to remember the age of the patient and the natural course of the lower leg development. The physiologic conditions causing in-toeing will have a spontaneous resolution, requiring good follow up, and parental reassurance. Rare causes will persist past the age of normal correction, but patients do not typically develop sequelae or symptoms. Detailed examination of the feet, ankles, knees, and hips will allow the examiner to differentiate between in-toeing of the possible areas that may be affected.