Intoeing

Etiology

The 3 major causes of pediatric in-toeing are metatarsus adductus, internal tibial torsion, and increased femoral anteversion. Each has unique findings and a typical age of presentation. Other differential diagnoses will be discussed below.[1][2]

Epidemiology

The most common condition in children younger than 1 year is metatarsus adductus. The incidence is 0.1% to 1% of births, with a historical predominance among girls. Results from recent studies suggested a shift to predominance among boys.[4] Metatarsus adductus is also the most common congenital foot deformity. From ages 1 to 4, the most common cause of intoeing is internal tibial torsion; no sex predilection or correlated cause has been identified. Increased femoral anteversion is the third most common cause of intoeing in children. Increased femoral anteversion can appear during infancy but is more noticeable after 3 years of age. Diagnosis typically occurs between 3 and 6 years of age. Increased femoral anteversion is twice as common in girls than boys.

Pathophysiology

Metatarsus adductus is associated with intrauterine position and is defined as angulation of the metatarsals toward the midline, resulting in a C-shaped appearance when viewed from the dorsal or plantar surfaces. Flexible deformities begin to correct spontaneously within the first 3 months. Flexible cases show improvement by 6 months, with most resolving by 12 months.

Age 12 months is the key decision point for treatment. The tibia is normally internally rotated at birth, although wide variations exist. Tibial rotation transitions to external rotation, which increases during the first 4 years of life and plateaus at about 10 years of age.

Femoral anteversion is influenced by increased intrauterine pressures and, postnatally, primarily by mechanical forces from everyday movements. In these cases, the neck of the femur is rotated inward, which rotates the greater trochanter posteriorly. Intoeing tends to become less noticeable with age due to a decrease in femoral anteversion during young child development.[3][5]

History and Physical

Physical examination should include inspection of the entire lower extremity with only undergarments in place, with particular attention to the hip and femur, knee and tibia, and feet. The patient's gait should be assessed while weight bearing, walking, and, if possible, running. Metatarsus adductus is defined as adduction of the forefoot relative to the midfoot and rearfoot in the transverse plane, measured from the midline of the foot bisector.

Classifications of metatarsus adductus are based on the degree of foot flexibility. Based on flexibility, metatarsus adductus is classified as flexible, semiflexible, or rigid.[6] Clinicians should differentiate metatarsus adductus from talipes equinovarus (clubfoot). Metatarsus adductus, by definition, is purely a forefoot, midfoot, and rearfoot deformity, and the foot and ankle are not in equinus.

If the forefoot can be passively overcorrected to reach abduction, the deformity is classified as flexible. If the forefoot can be brought only to neutral, the deformity is classified as semiflexible. If the forefoot cannot be brought to neutral, the deformity is classified as rigid. Clubfoot is a complex, rigid deformity of the entire foot and ankle and does not resolve spontaneously.

In patients with increased internal tibial torsion, the tibia is internally rotated (the shin is medially rotated) in the transverse plane from the knee joint bisector. Internal tibial torsion is most frequently bilateral and may present concomitantly with metatarsus adductus, increased femoral anteversion, or genu varum. Pertinent clinical examination findings include a forward- or outward-facing patella or, in a seated position, internal rotation of the medial malleolus compared with the lateral malleolus.

The last notable clinical examination finding is the thigh-foot angle (TFA). With the patient in a prone position and the knees flexed to 90°, the TFA can be assessed by the degree of angulation of the foot toward or away from the midline of the thigh when viewed from above. If the foot is internally rotated 10° to 15° or more relative to the midline of the thigh, this finding supports the diagnosis of intoeing due to increased tibial torsion.

Another method for evaluating tibial torsion is to quantify the angle between the knee axis and the transmalleolar axis (TMA), an imaginary line connecting the medial and lateral malleoli. With the patient prone and the knee flexed to 90°, the examiner palpates the medial and lateral malleoli and draws the TMA to indicate the direction of the distal tibia. Internal tibial torsion is present when this axis is rotated more medially than normal compared with the thigh or knee alignment, indicating that the tibia is twisted inward.

The greater the medial deviation of the TMA, the greater the degree of internal torsion. The most repeatable way to use these axes is to have the child sit with the knee bent to 90° and place lined paper under the foot. This paper is aligned with the knee axis. The transmalleolar axis is measured in relation to the lines on the paper. The angle between the transmalleolar axis and the knee axis is then measured with a goniometer.[7]

Children with femoral anteversion may prefer the W position, with the legs splayed to the sides while seated flat on the floor, knees forward, and feet facing posteriorly. Sitting cross-legged on the floor may be difficult. The discomfort and dislike these patients have for lateral rotation improve over time, as shown by their increased comfort with sitting cross-legged.

On examination, femoral anteversion is evident with the patella in the midline when walking or standing, although it points inward when running. The characteristic appearance during running is described as a windmill or eggbeater pattern, in which the patient's lower leg pushes off and swings laterally as it leaves the ground. The 2 main tests are performed in the prone position, with the knee bent at 90°.[8]

The Trochanteric Prominence Angle Test (Craig test) is the most commonly used. The greater trochanter is palpated, and the leg is rotated until it projects parallel to the table. The angle created between the examination table and the tibia is used to determine the degree of anteversion. A higher angle indicates greater femoral anteversion and a larger degree of intoeing. Another test is performed in the same position, with the child's hip internally rotated and the leg moved outward. Children with increased femoral anteversion have increased internal rotation, typically greater than 60°, and reduced external rotation compared with children with typical femoral version.[9]

Evaluation

Diagnosis is made clinically, with limited need for imaging in cases considered likely to improve with age. Radiography is indicated only for potential surgical procedures in severe cases of metatarsus adductus or when tibial or femoral conditions are suspected and need confirmation. Radiologic studies are used to exclude pathologic conditions.

Treatment / Management

Most cases are treated with observation, emphasizing parental reassurance. Myths should be dispelled, including claims that sleeping prone with hips and knees flexed or sitting in the W position leads to worsening deformities. Treatments such as special shoes, orthotics, braces, and physical therapy are reserved for recalcitrant cases.[10](B3)

Flexible metatarsus adductus is expected to resolve by 2 years of age, and persistence is typically asymptomatic. Rigid and severe metatarsus adductus with no flexibility should be referred for serial casting.[11] Guidance to parents is reinforced with serial clinical measurements and reassurance. Referral should be made when any of the following are present: measurements more than 2 standard deviations from the reference range, pain, or abnormal function.[9][12] 

Patients with tibial torsion should be reassured that increased internal angles are normal during development. Physiologic position progresses toward the midline after the second decade, with most of the correction expected by 5 years of age. Similar to metatarsus adductus, chronic issues are uncommon with persistent internal tibial torsion. Rare cases of cosmetic or functional deformity may be surgically corrected with distal tibial derotational osteotomy. With tibial torsion, the thigh-foot angle increases with age, progressing from negative to positive (external rotation) values (Table 1). Most children achieve neutral to external rotation by 4 years of age.[13] 

Table 1. Thigh-Foot Angle With Tibial Torsion by Age

Similar to other common physiologic conditions mentioned above, the natural course of femoral anteversion is spontaneous resolution over time. Femoral anteversion has the longest course, resolving around age 11. Persistence may also be seen in a small number of patients, with rare development of symptoms or complications.

The mainstays of treatment are observation and reassurance to parents about the natural course of decreasing anteversion. No recommended nonoperative treatments exist, and the only notably effective surgical treatment is femoral derotational osteotomy. Because of the high likelihood of complications from the surgical procedure, femoral derotational osteotomy is only considered for patients older than 11 years with severe functional sequelae or cosmetic deformity. Normal ranges for femoral anteversion within 2 standard deviations of the mean by age are described in Table 2 and decrease with age.[13] 

Table 2. Normal Ranges of Femoral Anteversion by Age

Differential Diagnosis

The bulk of intoeing cases resolve over time. Clinicians should elicit symptoms and assess signs during the history and physical examination to rule out less common conditions that may present similarly. Developmental dysplasia of the hip (DDH) should be considered in the differential diagnosis, particularly in infants with risk factors, including family history, breech presentation, and female sex.

The key differentiating factor is that DDH affects hip congruence and stability, whereas the femoral causes of intoeing involve only rotational alignment and do not compromise stability.[14] DDH can be associated with metatarsus adductus but may also present as an isolated finding. Careful monitoring and timely imaging when suspected can differentiate physiologic hip laxity and normal hip development from 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 characterized by multiple foot and ankle findings, including plantarflexion (cavus), metatarsus adductus with forefoot valgus, rearfoot varus, and foot and ankle equinus, represented by the mnemonic CAVE. Secondary causes due to underlying conditions can include skew foot, hyperactive abductor hallucis, coalition, stroke, cerebral palsy, and neuromuscular diseases.

Prognosis

The overall prognosis of the 3 pathologies is good, with condition-specific time frames for resolution. Metatarsus adductus resolves earliest, with about 90% of cases correcting by 1 year of age. Internal tibial torsion typically resolves between 4 and 7 years of age. Femoral anteversion takes the longest to resolve, gradually decreasing from about 30° at birth to adult values of approximately 10° to 15° by 8 to 10 years of age, at which point any remaining deformity becomes fixed.

Complications

Direct complications are uncommon, but the interplay among the conditions should be considered. Metatarsus adductus is attributed to intrauterine positioning, and clinicians should be aware that other comorbidities associated with intrauterine positioning include torticollis and developmental dysplasia of the hip, which is commonly bilateral.