Etiology: Proximal femoral focal deficiency (PFFD) refers to abnormalities that range from mild shortening and hypoplasia of the femur to severe deficiency of the bone and dysplasia of the acetabulum. The defect is thought to be a result of altered proliferation and maturation of the chondrocytes of the proximal femoral physis in utero, which in turn results in underdevelopment of the ipsilateral acetabulum. A child with PFFD usually presents in infancy with a short extremity and an unstable hip.³ A well-formed acetabulum implies the presence of a femoral head, which might be cartilaginous and therefore is not apparent radiographically early in life. Most cases are sporadic; however, the combination of bilateral femoral deficiencies and abnormal facies, known as the femoral hypoplasia–unusual facies syndrome, is thought to be an autosomal-dominant disorder.

PFFD should be distinguished from developmental dysplasia of the hip, infantile coxa vara, and congenitally short femur. In the setting of developmental dysplasia of the hip, proximal femoral neck and head hypoplasia may be present. The subtrochanteric region of the femur is normal and distal congenital anomalies are absent, and the deformities at the level of the acetabulum are more severe than the deformities at the level of the femoral head and neck. Persons with infantile coxa vara have a normal subtrochanteric region and distal bones, and the femur is normal length, accounting for bowing. Unlike PFFD, infantile coxa vara is discovered after weight bearing occurs.⁴ A congenitally short femur may be unilateral or bilateral and often is associated with reduction defects elsewhere in the same limb. Most cases are sporadic, but several external factors have been implicated in more complex deformities. Known causes include drugs (such as thalidomide), trauma, irradiation, infection, and focal ischemia.⁵ Unlike patients with PFFD, patients with a congenitally short femur have a stable hip.

Imaging: The most commonly used classification for PFFD was proposed by Aitken (Fig. 132-2).⁶ The least severe type is class A, which refers to an adequate or only mildly dysplastic proximal femur and acetabulum. The femoral head is present but is separated from the shortened distal femoral segment. With age, a fibrous connection between the head and the distal femoral segment ossifies—usually, not completely. A subtrochanteric varus deformity invariably is present. Class C deformities have a residual acetabulum present (Fig. 132-3). In the most severe form, class D, most of the femur and the ipsilateral acetabulum are absent.

PFFD is associated with other ipsilateral deformities, including fibular hemimelia (in more than 50% of affected children), shortening of the tibia, equinovalgus deformity of the foot (more often than equinovarus deformity), and deficiency of the lateral rays of the foot. PFFD is bilateral in 15% of affected children.⁷

Sonography can be used to delineate radiographically inapparent structures at an early age. If a cartilaginous femoral head and its connection to the femoral shaft can be shown, the stability of the hip joint is likely greater than is implied from radiographs. Similar to sonography, magnetic resonance imaging (MRI) is useful for defining the anatomy of the hip joint and associated deformities of the limb,⁸ allowing for appropriate early classification of deformity. Although the acetabulum might appear developed, even the least severe forms of PFFD are associated with acetabular deficiency. In contrast to the predominantly anterior deficiency of developmental acetabular dysplasia, the acetabulum in PFFD usually has an insufficient posterior wall. Most of the muscles about the affected hip are hypoplastic when compared with the contralateral normal side, with the exception of the sartorius muscle, which often is hypertrophied. This situation results in the characteristic flexion deformity of the hip and knee. MRI also defines the anatomy of soft tissues that can guide surgical exposure and preparation of the limb stump for fitting of a prosthesis.

Treatment and Follow-up: Therapy for children with PFFD is based on the severity of the deficiency and projection of growth and final limb length discrepancy at maturity. Objectives for treatment are to maximize the length of the extremity, to promote stability of the hip, knee, and ankle, and to optimize anatomic alignment. Mild deformities may not require surgery. Stabilization of the upper femoral defect is controversial and usually is indicated if a deformity is progressive. Children with severe deformities benefit from amputation of the foot and fusion of the knee. Rotationplasty of the tibia, in which the foot is rotated 180 degrees (so that the toes face posteriorly and the ankle now serves as a knee joint), allows the ankle and foot to control a distal prosthesis.⁹ Intact sensory feedback from the foot provides proprioceptive control of the knee. Thus it is imperative to assess the morphology of the proximal femur and acetabulum, the cartilaginous epiphyses of the knee, and the supporting soft tissue structures. For example, instability of the knee can result from absence of the anterior cruciate ligament. In the rare case of bilateral PFFD, amputation is contraindicated and therapy is based on extension prostheses that enhance the child’s height.

Etiology: Fibular hemimelia is the most common hemimelia and the most common congenital anomaly of the fibula. It also is referred to as congenital short tibia with absent fibula syndrome. Unilateral absence is more frequent than bilateral deformity. A band of strong connective tissue may replace all or most of the fibula.¹⁰ Fibular hemimelia is associated with a short, bowed tibia, absence of lateral rays of the foot, tarsal abnormalities (particularly coalitions), and femoral shortening or deficiency in 15% of patients. Caskey and Lester¹¹ reported a clubfoot deformity in 16% of patients with fibular hemimelia. Other associations include small, subluxed, or dislocated patellae, hypoplastic femoral condyles, and ligamentous deficiencies of the knee.

Imaging: Fibular hemimelia ranges from mild deficiency of the proximal end of the bone to complete absence accompanied by multiple malformations of neighboring structures (Fig. 132-4). MRI can document associated abnormalities, particularly if surgery is contemplated, including associated ligamentous deficiencies of the knee.

Treatment and Follow-up: The talipes equinovalgus deformity of the foot and severe shortening of the limb associated with fibular hemimelia result in poor function of the limb. Children with extensive abnormalities involving the fibula, ipsilateral tibia, femur, and foot benefit the most from early amputation of the foot and often the more proximal structures.¹² If the deformity is less severe, lengthening of the affected side, realignment of the tibiotalar articulation, and epiphysiodesis of the contralateral limb often are undertaken. Attempts at lengthening a severely dysplastic limb often are unsatisfactory.

Etiology: Most cases of tibial hemimelia are sporadic, although reported forms (particularly bilateral deformities) display an autosomal-dominant inheritance pattern. Jones et al.¹³ classified the spectrum of tibial dysplasia into four groups. In type I, which is the most severe form, the tibia is not recognized radiographically at birth. Lack of ossification of the distal femoral epiphysis implies that no proximal tibia is present. The least severe form, type IV, includes congenital tibial diastasis. In children with this form, the tibia is short and diverges from the fibula at the ankle. The talus is displaced proximally. No normal distal tibial articulation surface is present.

Imaging: Radiography of tibial hemimelia (Fig. 132-5) ranges from absence of a portion of the distal tibia to complete absence with multiple malformations of neighboring structures. MRI can document associated abnormalities, including associated muscular and ligamentous deficiencies, which is important if surgery is contemplated. MRI may identify a cartilaginous tibial remnant that may not be identified readily on radiography.

Treatment and Follow-up: Treatment of tibial hemimelia varies with the severity of the deformity. A knee disarticulation is recommended for complete tibial absence. Brown pioneered centralization of the fibula with a Syme amputation of the foot in children with complete tibial hemimelia.¹⁴ This approach produces adequate results in the rare cases in which the quadriceps muscles are well developed. When the quadriceps mechanism is abnormal, the patella often is absent. MRI can be used to assess deficiencies preoperatively, allowing the clinician to discern who will function better with primary knee disarticulation (most patients) rather than knee reconstruction.

Etiology: Conditions associated with radial deficiency are listed in Box 132-1.¹⁵ Usually the entire limb is involved to some degree, which often results in joint dysfunction of the shoulder, elbow, wrist, carpus, and small joints of the hand. Associated muscular deficiencies also are proportionate to the degree of skeletal abnormality. Neurovascular abnormalities include an absent radial artery and superficial radial nerve.

Whether radial deficiency is isolated or is associated with a syndrome, the primary malformation is likely the result of a vascular abnormality in the embryo that occurred before differentiation of mesenchyme into muscle and bone.¹⁶ Most cases are sporadic, but some autosomal-dominant and autosomal-recessive inheritance patterns are reported. Other cases are likely the result of various environmental insults from viruses, chemicals, radiation, and drugs during limb bud development.

Imaging: Congenital radial deficiency ranges from hypoplasia of the thumb to various degrees of radial hypoplasia. Complete absence is the most common longitudinal deficiency. This deformity usually is accompanied by radial and volar deviation of the hand, which results in part from unopposed pull by the flexor carpi radialis and brachioradialis muscles.

In most cases of radial aplasia, the forearm is bowed to the radial side and the distal ulna is prominent (Fig. 132-6). The forearm is short (usually approximately two thirds the length of the normal contralateral side) and remains proportionately so throughout growth. Often, only the capitate, hamate, and triquetral bones and the metacarpals and phalanges of the four ulnar rays are present and normal. The trapezium, scaphoid, and first ray often are deformed or absent. If a remnant of the radius is present proximally, it usually is fused to the ulna, which is curved, shortened, and thickened. Bilateral deficiency occurs in approximately 50% of affected children.¹⁵ The degree of deformity of the hand is related to the severity of deficiency of the forearm.

Treatment and Follow-up: Treatment of a longitudinal radial deficiency begins with serial casting and splinting intended to improve radial deviation by stretching the soft tissues. This treatment often is followed by surgical centralization of the hand over the ulna to improve function and appearance.¹⁷ Thumb reconstruction and pollicization of the index finger often are indicated.

Etiology: Deficiency that occurs along the ulnar or postaxial border of the upper extremity is known as ulnar deficiency or ulnar clubhand. It is a relatively uncommon disorder that occurs much less frequently than radial deficiency (radial clubhand). Approximately 48% of cases have anomalies of the contralateral limb.¹⁸ Most cases are sporadic, but associations with many other syndromes have been reported, most commonly Brachmann-de Lange syndrome.

Imaging: In persons with ulnar deficiency, coexisting abnormalities almost always are present in the carpal, metacarpal, and phalangeal rays (e-Fig. 132-7). The pisiform is always absent, and the hamate frequently is not detected. Syndactyly, carpal fusion, and radiohumeral fusion are frequent. The forearm is shortened and bowed, with a concavity to the ulnar side. The hand is deviated in an ulnar direction, and elbow abnormalities are common. Hypoplasia of the shoulder girdle and the upper arm can coexist with ulnar deficiencies. Anomalies of the contralateral upper limb and the lower limbs (such as PFFD) have been reported.

Treatment and Follow-up: Treatment for ulnar deficiency includes early correction of ulnar deviation of the hand, which is achieved with serial casting. Surgical treatment is reserved for cases with significant limitation of function.¹⁹ Forearm instability and associated hand deformities must be addressed.

Etiology: Constriction bands are thought to result from intrauterine rupture of the amnion and subsequent mechanical constriction of fetal limbs.²⁰ Various body parts become entangled in the amnion as it separates from the chorion. In some instances, adjacent structures are pulled together by the bands and ultimately become fused, producing a soft tissue syndactyly. Bony syndactyly is very rare. The earlier the amnion ruptures, the more severe are the malformations. Limb abnormalities range from slight soft tissue grooves to transverse intrauterine amputations. Acrosyndactyly, craniofacial and visceral anomalies, and fetal death are part of the spectrum of congenital constriction band syndrome. Sporadic congenital constriction band syndrome is estimated to occur at an incidence of 1 : 1200 to 1 : 15,000 births.

An alternative explanation is the intrinsic theory, which suggests that an inherent defect leads to bands during limb embryogenesis.²⁰

Imaging: Radiography may underestimate the degree of soft tissue compromise, and associated anomalous vascular anatomy may not be recognized. Typical conventional radiographic findings include a tethered appearance of fingers with a characteristic tight distal waist with soft tissue syndactyly (Fig. 132-8). MRI can be used to evaluate the depth of the constriction band, the degree of resultant lymphedema, and the integrity of the involved musculature.

Treatment and Follow-up: Surgical treatment usually is cosmetic, although it may be needed to relieve massive edema distal to a constriction band or to improve neurovascular function. Intervention for patients with acrosyndactyly may result in partial correction of the deformity and improved longitudinal growth.

Etiology: Arthrogryposis is a descriptive term used loosely to refer to conditions that result in congenital contractures involving two or more joints, such as those that limit intrauterine movement.²¹ The earlier in gestation that movement is limited and the longer the restriction lasts, the more severe will be the contractures at birth. Normal in utero motion is necessary for normal development of joints.

Arthrogryposis may result from abnormal muscles (such as myopathies), abnormal nerve function or innervation, abnormal connective tissues, or mechanical limitation of movement (such as oligohydramnios or multiple fetuses). Other possible causes include genetic defects, mutagenic agents, mitotic abnormalities, and toxic chemicals or drugs (Box 132-2).

Imaging: Contractures that are present at birth often are symmetric and most commonly affect distal parts of limbs. Clubfoot deformities often are present. The lower extremities are usually involved, but more than half of patients have upper limb abnormalities as well. Rigid joints and hypotonia contribute to frequent perinatal fractures. Soft tissue dimples may be seen over the affected joints, and muscle mass is decreased in affected limbs (e-Fig. 132-9). Affected muscles are partially or completely replaced by fatty or fibrous tissue. In many children, a scoliosis eventually develops. MRI can be used to assess joint integrity when surgery to maximize joint function is planned.

Treatment and Follow-up: The long-term prognosis for most children with arthrogryposis is good. However, children with associated central nervous system abnormalities usually have a limited life span. A neuromuscular workup is recommended for all children with arthrogryposis. Early therapy, including manipulation to increase range of motion, as well as surgery, is advocated for best results.²²

Etiology: Tarsal coalition is a congenital failure of segmentation of the primitive mesenchyme that results in the union of two or more tarsal bones. A preadolescent or adolescent child with pain in the midfoot and hindfoot that is associated with lack of motion in the subtalar region should be suspected of having a tarsal coalition. Prevalence in the U.S. population is approximately 1% or less. At least 50% of patients with coalitions have bilateral findings.²³ An autosomal-dominant inheritance pattern with a high level of penetrance is reported, although the coalition need not involve the same joint. Although it typically presents during the second decade of life, tarsal coalition may not manifest until adulthood.

Tarsal coalition is defined on the basis of anatomic location and completeness of ossification. A complete ossific bar forms a synostosis, a cartilaginous bar forms a synchondrosis, and a fibrous union is termed a syndesmosis. The most common fusions are talocalcaneal and calcaneonavicular. The middle facet is the most common location for a talocalcaneal coalition. Talocalcaneal coalitions often may extend posteriorly, with involvement of the junction of the middle and posterior facet. Talonavicular (e-Fig. 132-10) and calcaneocuboid coalitions are much less common. Synostoses can occur between other bones of the foot but frequently are associated with other limb abnormalities, such as fibular hemimelia or short femur, or disorders such as Apert syndrome.

Symptoms from a tarsal coalition present with advancing ossification. Pain with activity usually is the presenting symptom. The child may have a peroneal spastic flatfoot, which involves pain and rigid valgus deformity of the hindfoot and forefoot, along with peroneal muscle spasm. This condition is not a true spasticity but reflects peroneal shortening to adjust for heel valgus and to maintain a less painful position for the subtalar joint.

Imaging: A 45-degree lateral oblique radiograph of the foot directly shows a calcaneonavicular coalition. The secondary radiographic features of calcaneonavicular coalitions visible on a lateral radiograph include pes planus, anteater sign (Fig. 132-11), and talar beak sign (e-Fig. 132-12). A reverse anteater sign is seen on the anteroposterior (AP) view of the foot and is defined as diminished AP height of the lateral portion of the navicular (compared with the medial navicular), with the navicular extending far lateral with respect to the talar head.

Radiographic features of talocalcaneal coalitions include the C sign (Fig. 132-13, A), talar beak, an ovoid, enlarged sustentaculum tali (see Fig. 132-13, A), and broadened lateral process of the talus.

The talar beak associated with tarsal coalitions is a dorsal extension of the talar head (see e-Fig. 132-12). A talar beak should not be confused with a talar ridge. The talar ridge represents bony proliferation related to the insertion of the anterior tibiotalar capsule and is located along the more proximal dorsal talar neck rather than at the distal talar head.²⁴

A ball-and-socket articulation of the distal tibia and talus is an uncommon association with tarsal coalition. However, this configuration at the ankle joint is nonspecific and may be associated with congenital long bone deficiencies, as well as tarsal coalitions.²⁵

Computed tomography (CT) and MRI help to define the nature and cross-sectional area of a fusion. CT is more cost-effective if the clinical suspicion for coalition is high (Fig. 132-13, B). If other causes of pain and limited hindfoot mobility are considered, then MRI may be indicated. MRI may directly show bony, cartilaginous, and fibrous unions. Bone marrow edema often is noted adjacent to the fused articulation (Fig. 132-14).

Treatment and Follow-up: Casting and nonsteroidal antiinflammatory medications often are the initial treatment for symptomatic children. Steroid injections and physical therapy also may be used. If symptoms are not relieved and no degenerative changes have occurred, then surgical resection of the abnormal tarsal bridging often is attempted.²³ Regrowth of a calcaneonavicular coalition can be halted by interposition of the extensor digitorum brevis tendon. Fat frequently is interposed after resection of a subtalar coalition. Subtalar fusion or triple arthrodesis may be indicated in refractory cases.

Etiology: Congenital radioulnar synostosis anomaly is due to failure of longitudinal segmentation between the radius and the ulna.²⁹ In utero, cartilaginous anlagen of the humerus, radius, and ulna are connected. Normal separation progresses from the distal end of the forearm to the proximal end. An insult to segmentation during early in utero development can lead to bony or fibrous synostosis. Radioulnar synostosis is associated with disorders such as Apert and Carpenter syndromes, as well as with other upper extremity abnormalities such as polydactyly, syndactyly, and carpal coalition.

On clinical examination, the child often may have a fixed degree of pronation and a mild degree of flexion at the elbow. Pain usually occurs during the teen years, when progressive and symptomatic radial head subluxation may be seen.

Imaging: Osseous coalition is best seen on AP radiographs (Fig. 132-18). Radioulnar synostosis may lead to secondary radial head dysplasia (see Fig. 132-18, B) because of the lack of articulation between the radial head and capitellum needed for normal development. Posterior dislocation of the radial head also may be seen (e-Fig. 132-19).

Treatment and Follow-up: Surgical treatment usually is reserved for patients with a severe pronation deformity or symptomatic radial head subluxation, particularly when it involves the dominant hand. A both bone extraarticular derotational osteotomy through the forearm to improve supination may be performed.³⁰ Resection of the proximal synostosis is complex and may not lead to improved forearm and hand function.

Etiology: Longitudinal epiphyseal bracket is a congenital deformity that affects the short tubular bones that normally develop a proximal epiphyseal ossification center (e.g., phalanges, first metacarpal, and first metatarsal). The deformity may be sporadic or may occur in association with conditions such as Rubinstein-Taybi syndrome and fibrodysplasia ossificans progressiva. The cause is likely incomplete development of the primary ossification center of the bone during early fetal growth. The growth disturbance relates to the longitudinally oriented cartilaginous bracket, which causes growth to follow a “C-shaped” curve.³²

Imaging: The involved bone is trapezoid or triangular in shape (Fig. 132-24). The diaphyseal–metaphyseal osseous unit is bracketed along the longitudinal side by a physis and an epiphysis. The physis is arclike (see Fig. 132-24, B), extending from the medial proximal surface along the longitudinal margin of the bone to the distal medial surface, and is similar in configuration to a bracket. The thumb usually is affected. Other anomalies of the digits frequently are associated with the longitudinal epiphyseal bracket.

Treatment and Follow-up: Corrective splinting in infancy is not effective. Early surgical intervention, often a wedge osteotomy, is recommended to allow for remodeling and to facilitate longitudinal growth of the bone.³³

Etiology: Split hand-foot malformation (SHFM) refers to the congenital splitting of the hands or feet into two halves. SHFM is attributed to hypoplasia or aplasia of the phalanges, metacarpals, or metatarsals of one or more fingers or toes. The deformity also is referred to as ectrodactyly, cleft hand or cleft foot, or lobster or crab claw deformity.

SHFM may be isolated or associated with congenital constriction band syndrome, or, most commonly, it may occur as a component of the ectrodactyly–ectodermal dysplasia–cleft lip/palate syndrome.³⁴ More than 75 syndromes have been associated with SHFM. Ectrodactyly–ectodermal dysplasia–cleft lip/palate syndrome usually has an autosomal-dominant inheritance pattern with incomplete penetrance and variable expression, although autosomal-recessive forms have been described. SHFM has been detected on prenatal ultrasonography, which can guide counseling and reconstructive efforts.

Imaging: SHFM is highly variable in presentation. It can range from mild digital changes to the most severe monodactyly with only the fifth digit remaining. Two distinctive clinical forms have been described—typical and atypical forms. The typical form has an autosomal-dominant inheritance pattern and involves the lack of phalanges and metacarpals, resulting in a deep V-shaped cleft with the two halves resembling a lobster claw (Fig. 132-25). The much less frequent atypical form is sporadic and results in a much wider cleft, which forms a U-shaped central defect. The atypical form rarely involves the feet. Vascular disruption has been implicated as the cause. In most forms the digits frequently curve in toward the cleft, and a reduction in the number of digits may occur. Syndactyly or synostosis often is present.

Treatment and Follow-up: Patients affected by SHFM usually have good functional use of their extremities and therefore surgical intervention usually is not indicated.

Etiology: Congenital radial head dislocation is the most commonly identified congenital abnormality of the elbow. More than half of cases are associated with other conditions, such as anomalies of the lower extremities, scoliosis, and various syndromes (e.g., Klippel-Feil).³⁵ Whether it is an isolated abnormality or is associated with other conditions, congenital radial head dislocation is believed to have an autosomal-dominant inheritance pattern. The deformity can be unilateral or bilateral.

Imaging: Congenital radial head dislocation is associated with a small, underdeveloped forearm, a flattened and hypoplastic capitellum, and a short ulna. The proximal ulnar diaphysis often may have a posterior apex bowing (Fig. 132-26, B). The radial head is dysplastic with an elongated, thinned, and convex articular surface instead of the normal concave shape. The radial head is most commonly dislocated posteriorly (see Fig. 132-26). The degree of radial head dysplasia is correlated with the severity of dislocation. Radiographs should be carefully evaluated for concomitant radioulnar synostosis.

Treatment and Follow-up: Asymptomatic dislocations are not treated. If the child has pain, the radial head can be excised. However, excision of the radial head frequently is accompanied by pain from abnormal mechanics at the wrist. Recent work suggests that open reduction of the proximal radius at an early age may be beneficial.

Etiology: Posteromedial congenital bowing affects the tibia, fibula, and soft tissues of the lower extremity. The origin and pathogenesis remain uncertain and may be related to abnormal early embryologic development rather than to abnormal fetal positioning or intrauterine fracture. Fetal vascular insufficiency also may play a role. After examination of a fetus with congenital bowing, De Maio and associates suggested that compressive events associated with amnion rupture may be responsible.³⁶ As the child grows, tibial bowing and shortening often partially resolve.

Posteromedial congenital bowing should be differentiated from congenital tibial dysplasia (CTD). Other terms for CTD include anterolateral tibia bowing or congenital pseudoarthrosis of the tibia. It is a rare anomaly but does occur in a small number of patients with neurofibromatosis type 1 (NF1). Approximately 20% to 50% of patients with CTD do not have NF1.³⁷

CTD presents as anterolateral bowing or fracture of the tibia, often before other manifestations of NF1 present. Lack of involvement of the fibula suggests that the bowing will resolve spontaneously. Pathologic studies show abnormal, highly cellular fibrovascular tissue with variable amounts of fibrocartilage and hyaline cartilage within the tibia. Bone growth and repair are abnormal. The pattern of abnormal fibrous tissue results in the dysplastic or cystic changes characteristic of the disorder.

Imaging: With posteromedial congenital bowing, the tibia and the fibula show marked posteromedial bowing at the middle or distal one third of the shaft (Fig. 132-27). Rarely is the bowing lateral. At birth, the foot is held in a calcaneovalgus (dorsiflexed) position.

Radiographic changes seen with CTD are variable and include anterolateral bowing of the tibia, fracture, pseudarthrosis, hourglasslike constriction of the midshaft of the tibia, cystic changes usually at the junction of the upper and middle thirds of the tibia, sclerosis that narrows the medullary canal, and, infrequently, involvement of the fibula alone (Fig. 132-28).

Treatment and Follow-up: Treatment for posteromedial congenital bowing of the tibia is conservative; for example, corrective casts or splints may be used to hold the foot and support the leg during growth and remodeling. If a severe persistent deformity continues beyond toddler age, a leg length discrepancy, usually on the order of 3 to 7 cm, may result that requires osteotomies and lengthening procedures. Occasionally, epiphysiodesis of the contralateral side may be needed.

In persons who have anterolateral bowing associated with NF1, fracture and refracture rates are very high. Limb length inequality is frequent and results from disuse atrophy and abnormal growth at the distal tibial physis. Often a valgus deformity is noted at the ankle. Surgical management can be frustrating because nonunion or pseudarthrosis after osteotomy is frequent.