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Lower extremity positional deformations

Lower extremity positional deformations
Literature review current through: Jan 2024.
This topic last updated: Apr 10, 2023.

INTRODUCTION — Positional deformations are abnormalities that are mechanically produced by alterations of the normal fetal environment, which restrict fetal movement and/or cause significant fetal compression [1]. Deformations of the extremities occur frequently because fetal movement is required for normal musculoskeletal development.

Birth deformations can be divided into the following presentations:

Craniofacial abnormalities include scaphocephaly, plagiocephaly, mandibular asymmetry, flattened facies, deviated nasal septum, ear abnormalities, and craniosynostosis. (See "Overview of craniosynostosis", section on 'Categorization of cranial deformities'.)

Congenital torticollis. (See "Congenital muscular torticollis: Clinical features and diagnosis".)

Congenital scoliosis.

Lower extremity abnormalities including metatarsus adductus, positional calcaneovalgus feet (talipes calcaneovalgus), positional clubfoot (talipes equinovarus), internal and external tibial torsion, and physiologic genu varum.

The majority of deformations are foot and leg abnormalities, which are reviewed here. Developmental dysplasia of the hips (DDH), which is also associated with factors that restrict fetal movement, is discussed in greater detail separately. (See "Developmental dysplasia of the hip: Epidemiology and pathogenesis" and "Developmental dysplasia of the hip: Clinical features and diagnosis" and "Developmental dysplasia of the hip: Treatment and outcome".)

ETIOLOGY — Deformations are caused by problems that are intrinsic and extrinsic to the fetus. Infants with deformations caused by extrinsic causes are generally otherwise healthy. Those with deformations due to intrinsic factors are at increased risk for other fetal abnormalities (eg, renal disease or central nervous system disorder).

Intrinsic fetal causes include primary neuromuscular disorders resulting in decreased fetal movement, and renal disease resulting in decreased production of amniotic fluid and oligohydramnios, which increases the risk of fetal compression from outside forces.

Extrinsic causes are primarily due to factors that lead to fetal crowding and restricted fetal movement.

Oligohydramnios from leakage of amniotic fluid.

Breech position, in which movement of the fetal legs are restricted due to entrapment between the body of the fetus and the uterine wall. Breech position increases the risk of deformations 10-fold.

Abnormalities of the amniotic cavity such as the presence of uterine tumors or deformities (eg, uterine myomas, and bicornuate or septated uterus).

Multiple fetuses or very large fetus.

Compression of the amniotic cavity affecting its size and shape due to a small maternal pelvis and the size of neighboring maternal organs.

During the last trimester, the impact of external factors increases as the fetus grows and the amniotic fluid decreases. As a result, positional deformities are more common in term infants than preterm infants. This was illustrated in one study that reported no rotational deformities (eg, medial tibial torsion) in preterm infants with gestational ages ≤30 weeks [2].

The assessment of deformities in the newborn must include a thorough physical examination to detect any neurologic or other musculoskeletal abnormality that may have been an intrinsic cause of the deformity.

FOOT DEFORMITIES — Common positional deformities of the feet include metatarsus adductus, positional calcaneovalgus feet, and clubfoot (talipes equinovarus). In a study of 2401 consecutive newborns, the incidence of foot deformities was 4.2 percent [3]. Seventy-six percent of cases were due to metatarsus adductus, and 18 percent were due to calcaneovalgus feet. Almost all of the patients had normal feet at follow-up at five or six years of age. Deformations of the foot have been associated with an increased risk of DDH, with talipes calcaneovalgus conveying the highest risk (6.1%) in a 2020 cohort study of 494 children with DDH [4].

Metatarsus adductus — Metatarsus adductus is the most common congenital foot deformity [3,5]. It is characterized by medial deviation (adduction) of the forefoot while the hindfoot remains in a normal position, thus forming a "C" shape, or concavity of the medial aspect of the foot (picture 1). Metatarsus adductus is often bilateral; when unilateral, it occurs more often on the left than on the right (for unknown reasons) [6]. It is the most common cause of in-toeing gait in the infant [7].

The true incidence of metatarsus adductus is difficult to determine because mild variations generally are not reported. It is estimated to occur in up to 3 percent of term newborns [8,9]. It is more frequent in girls than boys and appears to run in families [6,9,10]. Metatarsus adductus appears to occur more commonly in first-born children due to the increased molding effect from the primigravida uterus and abdominal wall; second born children of an affected sibling have an approximate 1 in 20 risk of this deformity [11]. The incidence is higher in twin compared with singleton births, but the frequency of metatarsus adductus appears to be similar in preterm and term infants [10].

The clinical assessment based on a focused examination of the lower extremity and the management of metatarsus adductus are discussed separately. (See "Approach to the child with in-toeing", section on 'Focused examination of the lower extremities' and "Approach to the child with in-toeing", section on 'Metatarsus adductus'.)

The outcome for patients without intervention or with nonsurgical treatment for metatarsus adductus is excellent. This was illustrated in a case series of 31 patients (45 feet) with metatarsus adductus who were followed for a mean of 32.5 years [12]. At initial presentation, 12 patients (16 feet) with mild deformity received no treatment, 20 patients (29 feet) with moderate and severe deformity were treated with serial manipulation and casting, and 1 patient had bilateral involvement with no treatment on one foot and intervention on the other. No patient was treated with surgical correction. Excellent results were seen in all patients with mild deformity without treatment and in 90 percent of the more severely affected feet.

Positional calcaneovalgus feet — Positional calcaneovalgus feet, also referred to as talipes calcaneovalgus, is a common foot deformity [3]. It is characterized by hyperdorsiflexion of the foot with the abduction of the forefoot, which often results in the forefoot resting on the anterior surface of the lower leg (picture 2 and picture 3). External tibial torsion is a common associated finding.

It is a deformity that is thought to be more common in first-born children due to the increased molding effects of the primigravida uterus.

Calcaneovalgus feet generally resolves spontaneously. However, it should be differentiated from the following more severe conditions [13].

Congenital vertical talus, also referred to as "rocker-bottom foot", is a rare condition that is frequently associated with neuromuscular and genetic disorders (eg, trisomy 13 and 18) (picture 4). Congenital vertical talus has a fixed dislocation of the navicular dorsolaterally on the head of the talus. The ability to correct (or partially correct) the deformity with gentle pressure usually distinguishes the more flexible calcaneovalgus feet from the rigid congenital vertical talus [14]. In cases where the examination is inconclusive, a radiograph can differentiate between the two conditions.

Paralytic calcaneus foot deformity is seen in infants with a neuromuscular disorder (eg, myelodysplasia or polio), which results in the absence or paralysis of the gastrocsoleus muscle. The physical examination should differentiate between paralytic and positional calcaneovalgus feet by detecting a motor deficit in the former condition. (See "Myelomeningocele (spina bifida): Orthopedic issues".)

Posteromedial bow of the tibia is a condition that includes both a calcaneovalgus foot and a bowed, shortened tibia. Examination will detect a leg-length discrepancy. Bowing of the tibia can also be seen by radiography.

Most cases of positional calcaneovalgus feet will spontaneously resolve [3,14]. If the foot cannot be plantar-flexed below neutral, casting is indicated. Surgical treatment is not required [13].

Clubfoot — Clubfoot, also referred to as talipes equinovarus, is a complex condition that involves both the foot and lower extremity. It is characterized by the foot being excessively plantar flexed, with the forefoot swung medially and the sole facing inward (picture 5).

Club feet can be classified based on etiology as follows (table 1):

Positional clubfoot is due to intrauterine crowding or breech position. It is not a true club foot. It is a normal foot that has been held in a deformed position in utero. The positional clubfoot easily corrects to a normal position with manipulation.

Congenital clubfoot is the most common type. It is usually an isolated anomaly without a well-delineated etiology. Current management is based upon manipulation that includes casting and bracing (referred to as the Ponseti method) [15-17].

Syndromic clubfoot is associated with other clinical manifestations that comprise the underlying syndrome, which may be due to a genetic disorder, such as trisomy 18. (See "Prenatal diagnosis of talipes equinovarus (clubfoot)", section on 'Pathogenesis of clubfoot'.)

The prenatal diagnosis of clubfoot is discussed in greater detail separately. (See "Prenatal diagnosis of talipes equinovarus (clubfoot)".)

ROTATIONAL DEFORMITIES OF THE LEGS — Rotational variations of the foot position relative to the leg often occur in younger children due to intrauterine positioning. In utero, the fetus's hips are typically flexed, abducted, and externally rotated while the lower legs are internally rotated and the knees flexed. With intrauterine crowding and mechanical restriction, this position predisposes the fetus to rotational deformities that include internal and external tibial torsion and external rotation of the hips, which may result in physiologic genu varum.

Internal tibial torsion — Internal tibial torsion is a normal rotational variant and is a result of intrauterine positioning. It is the most common cause of in-toeing in toddlers as they begin to walk. It may also be associated with metatarsus adductus and genu varum. Internal tibial torsion is bilateral in approximately two-thirds of cases; in unilateral cases the left side is more commonly involved for unknown reasons [18-20].

On examination, the infant with internal tibial torsion will have a medially deviated foot when the patella is facing directly forward. The degree of torsion or rotation can be measured by the thigh-foot angle, the angular difference between the axis of the foot and the axis of the thigh when the patient is in the prone position with the knees flexed 90 degrees and the foot and ankle in neutral position (figure 1) [7]. (See "Approach to the child with in-toeing", section on 'Focused neurologic examination'.)

Spontaneous resolution of internal tibial torsion occurs with ambulation and normal growth, so no intervention is generally required. Surgical treatment is rarely indicated and is reserved for the older child with marked functional or cosmetic deformity. (See "Approach to the child with in-toeing", section on 'Internal tibial torsion'.)

External tibial torsion — External tibial torsion is a normal rotational variant due to intrauterine positioning. It is the most common cause of out-toeing in infants and young children and is usually identified when the child begins to walk. It is often accompanied by positional calcaneovalgus.

On physical examination, the thigh-foot angle is abnormally positive with values between +30 to +50 degrees (figure 1).

This condition typically follows a similar course of internal tibial torsion, with spontaneous resolution over time. However, disability (eg, knee pain patellofemoral instability) is more common in children with persistent external tibial torsion than in those with internal tibial torsion [21]. Increased external tibial torsion is also associated with neuromuscular disorders including myelodysplasia and polio [19]. As a result, a careful neurologic examination should be performed in patients with this finding.

As with other positional deformities, intervention is usually not required as the majority of affected children will have spontaneous resolution. Significant improvement does not occur until the child has achieved independent ambulation. External tibial torsion is more likely to persist through adolescence than internal tibial torsion [22].

Surgical treatment is rarely indicated and is reserved for the older child with marked functional or cosmetic deformity (ie, thigh-foot values greater than +40 degrees) [23].

Physiologic genu varum — Physiologic genu varum, also referred to as "bowlegs," is a common deformity due to intrauterine positioning. The deformity is caused by a combination of external rotation at the hip due to the tight posterior hip capsule and internal tibial torsion. It is typically identified in the older infant or toddler shortly after the start of ambulation. Physiologic genu varum generally resolves spontaneously and must be differentiated from pathologic causes such as Blount's disease or rickets, which may require intervention. (See "Approach to the child with bow-legs", section on 'Physiologic varus'.)

SUMMARY AND RECOMMENDATIONS

Definition and etiology – Positional deformations are abnormalities that are mechanically produced by alterations of the normal fetal environment that restrict fetal movement and/or cause significant fetal compression. Deformations of the lower extremities occur frequently because fetal movement is required for normal musculoskeletal development. They include foot deformities and rotational deformities of the legs. (See 'Etiology' above.)

Foot deformities

Metatarsus adductus is the most common foot deformity with an estimated incidence of 3 percent. It is characterized by medial deviation of the forefoot while the hindfoot remains neutral (picture 1). In the vast majority of cases (90 percent), metatarsus adductus resolves spontaneously over time. However, a small minority of patients with a severe or rigid deformity may require further intervention (casting and surgery). (See "Approach to the child with in-toeing", section on 'Metatarsus adductus'.)

Positional calcaneovalgus feet (hyperdorsiflexion of the foot with the abduction of the forefoot) typically resolve spontaneously without intervention (picture 2 and picture 3). In some persistent cases, casting may be indicated. (See 'Positional calcaneovalgus feet' above.)

Positional clubfoot is a normal foot that has been held in a deformed position in utero. As opposed to a true clubfoot, the positional clubfoot easily corrects to a normal position with manipulation and will resolve spontaneously over time. (See 'Clubfoot' above and "Prenatal diagnosis of talipes equinovarus (clubfoot)".)

Leg deformities

Internal and external tibial torsion are rotational deformities that typically present as in-toeing (internal tibial torsion) and out-toeing (external tibial torsion) when the child begins to ambulate. With normal growth and development, both conditions generally resolve spontaneously without intervention. Surgical treatment is rarely indicated and is reserved for the older child with marked functional or cosmetic deformity. (See 'Internal tibial torsion' above and 'External tibial torsion' above.)

Physiologic genu varum (also referred to as physiologic bowing) is a positional deformity that is characterized by external rotational at the hip and internal tibial torsion. It is typically detected in the older infant and toddler shortly after ambulation begins. Physiologic genu varum generally resolves spontaneously and must be differentiated from pathologic causes, such as Blount's disease or rickets, which may require intervention. (See "Approach to the child with bow-legs".)

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