Karl E. Rathjen
Rotational and angular deformities of the lower extremities are among the most common orthopedic complaints to primary care providers. Fortunately, most patients have nothing more than normal physiologic variance, and the majority may be treated with education and observation. However, there are a variety of uncommon, but significant, orthopedic and neuromuscular conditions that may present as rotational or angular deformity. Thus, an understanding of both anatomy as well as potential pathologies is important.
ROTATIONAL ABNORMALITIES
Although the vast majority of parental concerns regarding rotational difference will represent nothing more than developmental norms, it is paramount to remember that rotational differences may be the presenting complaint in patients with mild neuromuscular differences; thus, a careful history and physical exam focusing on neuromuscular development should be incorporated with every patient who presents for evaluation of in- or out-toeing.
INTOEING
Intoeing is perhaps the most common gait deviation that presents for medical assessment. Assessment should begin with observation of the gait to determine the foot progression angle. The foot progression angle is the angle described by the intersection of the axis of the foot with the axis of progression. Although the torsional alignment of the lower extremities changes during skeletal development, most parents are unaware of this and will consider any deviation from the normal adult value of 10 to 20 degrees external as pathologic1 (Fig. 212-1). If an internal foot progression angle is identified, careful examination of the lower extremities can identify the anatomical location responsible for the inward deviation. Fortunately, because of normal physiologic variance, there is usually a strong correlation between the age of the patient and the anatomical location producing the inward deviation.
Metatarsal Adductus
Metatarsal adductus is the most frequent reason for intoeing in the first year of life and is the most common congenital foot deformity, affecting approximately 3% of all births. Metatarsus adductus occurs when there is inward torsion of the mid or forefoot with the hindfoot in normal position or slight valgus. It is bilateral in 60% of children. It is important to distinguish metatarsal adductus for more significant foot pathology—namely, talipes equinovarus (clubfoot). This may be accomplished by assessing the position of the hindfoot or heel. In clubfoot, the heel will be in equinus (plantar flexion), and the foot will not achieve neutral dorsiflexion. The severity of metatarsal adductus is determined by the amount of flexibility to the forefoot. A foot that neutralizes itself spontaneously with tickling of lateral border is termed mild or Grade 1. A moderate, or grade 2, foot is passively correctable but does not actively correct itself to neutral. A severe or grade 3 foot cannot be completely corrected with stretching.2 Because developmental dysplasia of the hip has been identified in up to 10% of the children with metatarsal adductus, a careful hip exam is paramount in these children.
There are no well-defined treatment indications for metatarsal adductus. Infants less than 3 months of age with moderate to severe metatarsus adductus may be treated with serial casting; children between 3 and 12 months can be treated with straight or reverse last shoes. The natural history of metatarsal adductus is usually quite benign. Parents can be assured that this is seldom, if ever, a functional problem, and improvement can be seen into adolescence.3,4
Internal Tibial Torsion
Internal tibial torsion is the most common cause of intoeing in children between the ages of 12 and 36 months. Parents of patients with significant internal tibial torsion may note bowed legs as well as intoeing, as it is often difficult to differentiate between the two in this age group. Internal tibial torsion can be identified by assessing the thigh–foot angle in the prone position (Fig. 212-2). As with all lower extremity rotational parameters, the thigh–foot angle varies with age (Fig. 212-1). Internal tibial torsion usually spontaneously improves throughout skeletal growth, and treatment is seldom required. Historically, special shoes connected to a bar (Denis Browne splint) were a popular treatment for internal tibial torsion; however, there has never been any scientific validation that these splints are efficacious.1,5
Excessive Femoral Anteversion
Excessive femoral anteversion is the most common etiology of intoeing in children over 4 years of age. Parents of these children often report a preference for sitting in the “W” position. (These children sit in this position because it is comfortable for them, and there is no evidence that doing so causes the abnormality.) Femoral ante-version is associated with increased internal rotation of the hip which is best assessed with the patient in the prone position6 (Fig. 212-3). As with other lower extremity rotational characteristics, hip rotation is dynamic and changes throughout growth (Fig. 212-1). Although some authors suggested a correlation between excessive femoral anteversion and osteoarthritis of the hip, the vast majority of literature indicates that the natural history of increased femoral anteversion is completely benign without functional or degenerative impact. Orthotic management of increased femoral anteversion has not been shown to be efficacious.1,6-11
FIGURE 212-1. The normal evolution of hip rotation, knee angle (aka mechanical axis), tibial torsion, angle of gait (aka foot progression angle), and arch development in children between 0 and 14 years of age. (With permission from Engel GM. Clin Orthop Relat Res. 1974:12-7.)
FIGURE 212-2. Determination of the thigh–foot angle in the prone position.
Correction of both internal tibial torsion and excessive femoral anteversion can be accomplished surgically through rotational osteotomy. However, because of the benign natural history of these conditions, it is important to recognize that such treatment is essentially for “aesthetic” rather than functional purposes, and as a result, it should be considered with great trepidation by the pediatric orthopedist. It is important that parents and patients be fully apprised of the risks and benefits before surgical procedures are entertained. We have found it helpful to include a physiological evaluation to access for other body image concerns.6,9
OUT-TOEING
Complaints of out-toeing are less common than those of intoeing, and these patients rarely have more than normal physiological variance. As with intoeing, it is important to remember that patients with out-toeing may have subtle occult neuromuscular pathology; thus, a careful developmental history and neurologic assessment are of paramount importance. Adolescents with slipped capital femoral epiphyses may develop new onset out-toeing which may be asymmetrical.12
ANGULAR DEFORMITIES
Angular deformities of the lower extremities include pure coronal plane deformities (genu varum or bowed legs and genu valgum or knock knees) as well as less common multi-plane deformities, such as anterior lateral and posterior medial bowing of the tibia. As with rotational alignment, the coronal plane alignment of the lower extremities changes during the first 7 years of life (Fig. 212-1). Thus, a pediatric practitioner must understand coronal plane evolution during growth to be able to determine when patients have alignment that falls outside the realm of normal. As demonstrated in Figure 212-1, children are at their maximum varus or bowlegged deformity as infants, and this slowly corrects to a maximal valgus or knocked knee deformity sometime between 2 and 4 years of life. An adult angular profile is usually achieved by 8 years of age.5,13,14
GENU VARUM
Genu varum may present in children of any age. The differential diagnosis includes normal physiologic variance, Blount’s disease, metabolic bone disease, and skeletal dysplasias. Despite the fact that genu varum is at its most severe at birth, it is uncommon for parents to bring it to the attention of providers before walking age. Parents, however, frequently express concern about the “bowleggedness” of their toddlers. As previously mentioned, increased tibial torsion is often responsible for the appearance of genu varum in toddlers with normal physiologic varus (Fig. 212-4). If evaluation of the lower extremities reveals symmetrical alignment with expected internal tibial torsion, patients simply need observation, and the parents should be reassured. However, in older patients (over 2 years of age) with significant deformity or asymmetry in the limbs, or a positive family history of metabolic bone disease, short stature, or risk factors for nutritional rickets, a standing anterior to posterior radiograph of both lower extremities should be obtained.
FIGURE 212-3. Determination of hip rotation (and, subsequently, femoral anteversion) in the prone position.
Blount Disease
Idiopathic genu varum, frequently referred to as Blount disease, can present at any age but most commonly presents in children less than 4 (infantile Blount disease) or over 10 years of age (adolescent Blount disease). Risk factors for infantile Blount disease include early walking age and obesity. The classic radiographic finding is calcification in the medial aspect of the proximal tibial epiphysis. Bracing has been shown to be effective in treating children with infantile Blount disease, particularly those with unilateral disease. If bracing fails to resolve the deformity, patients are usually treated with tibial osteotomy. If the deformity is not corrected before the age of 4, permanent growth disturbance may develop, resulting in progressive deformity and leg length discrepancy.14-17 Adolescent Blount disease most commonly occurs in obese African American males. The hallmark radiographic finding is widening of the medial aspect of the proximal tibial physis. Bracing is not effective in adolescent Blount disease, and patients with significant deformity are treated with growth modulation or tibial osteotomy.18-21
Rickets
Rickets refers to a variety of metabolic conditions that produce a disturbance in calcium homeostasis which leads to abnormalities in areas of rapid calcium turnover, most notably the physis. Nutritional rickets is the result of inadequate vitamin D intake. Although less common in the developed world, nutritional rickets still occurs, particularly in children with dark skin who are breast fed past 12 months of age. Other causes of rickets include hypophosphatemia, renal tubular acidosis, and end-stage renal disease. The radiographic hallmark of rickets is widening of the physis and associated “cupping” of the metaphysis. Angular deformity in patients with rickets may spontaneously correct through normal remodeling after optimization of their metabolic condition. Those with persistent deformity despite optimal medical treatment may require corrective osteotomy.14,22
Skeletal Dysplasias
Genu varum in patients with short stature should raise the suspicion of a skeletal dysplasia. Skeletal dysplasias are a heterogenous group of conditions that are inherited in Mendelian fashion, although spontaneous mutations are common. The diagnosis of skeletal dysplasias usually requires a skeletal survey and consultation with a pediatric musculoskeletal radiologist or geneticist. Because there are no effective nonoperative treatments, children with skeletal dysplasias and symptomatic genu varum require osteotomy.13,23
GENU VALGUM
Genu valgum or “knock knee” is less common than genu varum and is less likely to represent pathology. As discussed previously, coronal plane alignment of the legs evolves during growth, and genu valgum is most noticeable between 4 and 6 years of age (Fig. 212-1). During this stage of development, genu valgum is best treated with observation. Occasionally, adolescents will present with persistent genu valgum. A thorough history should be obtained to assess for the possibility of subtle growth arrest from trauma or infection, particularly if the limbs are asymmetrical. Most commonly, genu valgum in adolescents is predominately a cosmetic complaint, although valgus at the knee may predispose to patella dislocation. There are no effective nonoperative treatments of genu valgum. Surgical treatment of idiopathic genu valgum is occasionally indicated and best accomplished in adolescents with growth modulation techniques.14
FIGURE 212-4. Two-year-old with internal tibial torsion. Note the knee is directly anterior but the foot progression angle is medial. Note how the torsion of the distal tibia produces a “bowed-leg” appearance.
ANTERIOR LATERAL BOWING OF THE TIBIA
Anterior lateral bowing of the tibia is a rare condition that is usually a precursor to congenital pseudarthrosis of the tibia. Congenital pseudarthrosis of the tibia is a poorly understood bone dysplasia that produces angular deformity and fracture of the tibia that can be vexing to treat. Fifty percent of patients with this diagnosis will have neurofibromatosis. Usually, children with anterior lateral bowing of the tibia are managed in a brace until deformity progresses and pain interferes with function, at which time surgical attempts to achieve union of the congenital pseudarthrosis are indicated. Treatment is difficult and frequently complicated by recurrence with growth. Occasionally, patients with severe disease eventually require a below-knee amputation.24
POSTERIOR MEDIAL BOWING OF THE TIBIA
Posterior medial bowing of the tibia is a benign congenital deformity of unknown etiology. It is present at birth and can be quite dramatic, with the dorsum of the foot pressed back onto the anterior aspect of the tibia. The differential diagnosis includes a severe calcaneus valgus foot deformity.
Unlike anterior lateral bowing of the tibia, the natural history of posterior medially bowing is favorable, and the deformity usually spontaneously corrects in the first 2 years of life. However, patients should be followed until skeletal maturity, as they are likely to develop limb length inequalities that may require surgical treatment with epiphysiodesis or lengthening.13,25