Leg Disorders

Ryan D. Muchow

Vishwas R. Talwalkar

• Introduction to Leg Deformities

Children present with abnormal appearing lower extremities due to a variety of etiologies (Table 13.1) and at varied time points. Embryology and the uniqueness of the growth plate in children play significant roles in the development and management of pediatric lower leg deformity. Broad categories of limb deformity include congenital, metabolic/skeletal dysplasias, developmental, and acquired help group diagnoses based on etiology, timing of onset, and problem source, which allows for selection of the proper treatment. Congenital indicates an embryologic problem that results in aberrant anatomy present at birth; metabolic disorders can affect the bones and alter mineralization and ossification at different time points depending on the onset of the disorder; skeletal dysplasias represent mostly genetic issues that affect the growth plate; developmental refers to a problem of the growth plate or bone that is not initially present in a child’s life and the deformity develops later, and acquired infers normal anatomy and alignment that becomes distorted secondary to an outside influence (eg, trauma or infection) on the growth plate.

• Congenital Deformities of the Leg

Fibular Deficiency

Introduction

Fibular deficiency (or fibular hemimelia) is a lower extremity deformity marked most distinctly by the congenital absence of all or part of the fibula. This condition may be isolated or be a component of a family of congenital lower limb deficiency, which includes a spectrum of deformity that may encompass the femur, knee, tibia, ankle, and foot of the involved extremity. There is no known cause of fibular deficiency and there are no known genetic predispositions.

Table 13.1 The Causes of Lower Extremity Deformity Divided Into Four Broad Groups

CONGENITAL	METABOLIC/SKELETAL DYSPLASIA	DEVELOPMENTAL	ACQUIRED
Fibular deficiency	Rickets	Blount disease	Cozen phenomenon
Tibial deficiency	Skeletal dysplasia Achondroplasia Diastrophic dysplasia Morquio syndrome Sanfilippo syndrome	Congenital pseudarthrosis tibia/anterolateral bowing	Partial growth arrest
Posteromedial bowing

Clinical Significance

The presentation and clinical impact of fibular deficiency is highly varied and dependent upon the degree of involvement of the leg and the presence and degree of other lower limb deformities at each anatomic site. The spectrum of anatomic involvement in addition to the fibula includes femoral shortening, tibial shortening, knee valgus, anterior cruciate ligament deficiency, tarsal coalition, and lateral foot ray absence. Based upon the Birch classification, there are two factors that most predict the functional outcome for patients with fibular deficiency: a preservable foot and limb length inequality.¹

Physical Examination

Fibular hemimelia can typically be noted in an infant or small child given the associated congenital deformities. After gaining a general sense of the activity and age-appropriate function of the child, a focused physical examination of the lower extremities may reveal:²

Skin dimpling—Nonspecific and seen in various congenital deformities. Typically present over the tibia at the site of the bowing and/or knee in fibular deficiency (Figure 13.1).

Femoral shortening—In the supine position, the congenitally deficient femur will appear shorter when the hips and knees are flexed 90°. This is termed a positive Galeazzi sign (Figure 13.2). This can also be seen in patients with a congenitally dislocated hip. In the later instance, the femur is not shorter, the hip is dislocated posteriorly, and the femur appears shortened with this maneuver.

Limb-length discrepancy (LLD)—Because the bulk of children with fibular hemimelia have concurrent tibial shortening and some have femoral shortening, patients have reduced overall length of the involved limb (Figure 13.3).

Knee valgus, patella subluxation, and cruciate instability—Children with fibular hemimelia can have abnormalities at the knee. These include genu valgum (knock-knee deformity) as a result of lateral femoral condyle hypoplasia and the patella may subluxate laterally (Figure 13.4). Anterior and posterior knee instability is typically seen in older children as a result of cruciate deficiency (Figure 13.5).

Anterior bowing—Patients with fibular hemimelia will often have shortening of the tibia with angulation apex of deformity, which is predominately pointed anteriorly (Figure 13.6).

Ankle/hindfoot motion—In addition to the presence of hindfoot coalitions, patients can develop a “ball-and-socket” ankle. Therefore, inversion/eversion plus dorsiflexion/plantarflexion occurs through the ankle. Patients may display hypermobility or even instability at the ankle and have limited mobility of the midfoot.

Reduced lateral rays—In addition to bowing and shortening, the absence of rays from the lateral aspect of the foot is a hallmark of fibular deficiency (Figure 13.7).

FIGURE 13.1 Skin dimpling can often be seen in congenital limb deformities such as in this patient with fibular hemimelia.

FIGURE 13.2 This child with congenital short femur has a positive Galeazzi sign with shortening of the right femur. This can also be seen in patients with a dislocated hip.

FIGURE 13.3 This child with fibular hemimelia has concurrent shortening of the femur, genu valgum, shortening of the tibia, and absent foot rays.

FIGURE 13.4 This child with congenital limb deficiency has multiple abnormalities of the left knee. This includes lateral femoral condyle hypoplasia (white arrow), patella (red circle) subluxation (not centered in the knee compared to normal patella [yellow circle]), as well as likely absence of the cruciate ligaments as hallmarked by the lack of tibial spine development.

FIGURE 13.5 This child with congenital short femur has anterior instability of the knee joint due to congenital absence of the cruciate ligaments.

FIGURE 13.6 This child with fibular hemimelia has shortening of the tibia and an anterior and lateral bow of the tibia with an associate dimple at the apex of deformity.

FIGURE 13.7 This child with severe fibular hemimelia also has absence of the rays of his foot.

Pitfalls in Diagnosis

In the milder forms of fibular deficiency, patients may evade early diagnosis. Having all five rays, minimal deformity, high functionality, and bilateralism could be factors that would result in a patient being diagnosed later in life. A progressive genu valgum or limb length inequality (in a mild, unilateral patient) revealing itself during the school-age years may be the first presenting sign (Figure 13.8).

Differential Diagnosis

Congenital short femur and limb deficiency syndrome
Tibial hemimelia
Congenital foot deficiency
Pes planovalgus (flatfoot)

Diagnostic Tests or Advanced Imaging

An anteroposterior (AP) radiograph of the lower extremities will provide ample information to confirm the diagnosis and aid in determining treatment based on the degree of involvement of the rest of the leg. One can compare femoral lengths, assess tibial deformity, and reveal the lateral ray deletions (Figure 13.9). Hindfoot coalition and the ball-and-socket ankle may be more easily detected on radiographs in the older child (Figure 13.10).

Treatment and When to Refer

This diagnosis is best treated by a pediatric orthopedic surgeon with specialty in limb deformities. The initial decision with a patient with fibular deficiency is dictated by the functionality of the foot—a nonfunctional, nonplantigrade foot typically requires amputation. Additional intervention is dictated by LLD, angular deformity, and knee stability.

Tibial Deficiency

Introduction

Tibial deficiency, or tibial hemimelia, is a lower extremity deformity that is defined by the partial or complete congenital absence of the tibia. It is much more uncommon than fibular hemimelia and while most cases are sporadic in cause, some forms of the disorder present in an autosomal dominant fashion. In contradistinction to fibular deficiency, most patients with tibial deficiency will have abnormalities of the upper extremity, hip, or spine.

Clinical Significance

The lower extremity deformity associated with tibial deficiency is significant, will affect the child’s function, and typically requires surgical intervention. The key functional and treatment variable is the presence of an intact knee extensor mechanism to the tibia. If the proximal tibia is absent, there is no good attachment of the patella tendon to the lower limb.

FIGURE 13.8 This child has bilateral fibular hemimelia. There is asymmetric genu valgum of the left knee; however, limb lengths are fairly symmetric.

FIGURE 13.9 This child with congenital limb deficiency has a shortened right femur in comparison with the left, a shortened and bowed tibia consistent with fibular hemimelia, and an absence of toes of the affected foot.

Physical Examination

Given the involvement of other musculoskeletal systems in tibial deficiency, for example, upper extremity, spine, and hip, a thorough physical examination of the child is prudent. A focused lower extremity examination may reveal multiple lower limb anomalies (Figure 13.11)³:

Skin dimpling—Dimpling typically occurs at knee, ankle, or site of tibial involvement (Figure 13.12). In some cases, the dimpling may be the only sign of a shortened tibia.

Absence or duplication of medial (tibial) rays—Tibial deficiency often has severe polydactyly (Figure 13.11) with the more extensive duplication usually seen on the medial aspect of the foot (Figure 13.13).

FIGURE 13.10 This child with left fibular hemimelia also has a ball-and-socket ankle as demonstrated by the spherical red line.

FIGURE 13.11 This child with multiple congenital deficiencies of the limbs demonstrates bilateral tibial hemimelia. There is multiple polydactyly and syndactylization of the feet in addition to clubfoot deformities. The left tibia is shortened in comparison to the fibula, consistent with tibia hemimelia.

Equinovarus foot—In patients with tibial hemimelia, the feet typically have an equinovarus position (Figure 13.11) or resemble clubfeet (Figure 13.14) (

Video 13.1).

Extensor mechanism—The ability to bear weight and/or perform knee extension is an important functional distinction (

Video 13.2).

In general, the proximal knee articulation may not be fully represented by the radiographs. In

Video 13.3, we see that there is a much more articular stability during arthrography examination, which is represented in the radiographs in Figure 13.13 (

Video 13.3).

Pitfalls in Diagnosis

Tibial deficiency is associated with involvement of the upper extremity, spine, and hip and with numerous inherited syndromes making the entire history and physical pertinent to the diagnosis. Further, assessing the function of the knee and the ability of the child to actively extend will aid the clinician in assigning a classification and guide treatment.

Differential Diagnosis

Congenital short femur
Fibular deficiency
Clubfoot
Polydactyly

FIGURE 13.12 Similar to patients with fibular hemimelia, patients with congenital tibial abnormalities can also have skin dimpling at the site of deformity, such as this child with tibial hemimelia.

FIGURE 13.13 This child with tibial hemimelia has shortening of the tibia in comparison with the contralateral side, but also has extra digits along the medial aspect of his foot.

FIGURE 13.14 This child with tibial hemimelia has shortening of the tibia with comparison to the contralateral side. This side also has a clubfoot deformity, which has been partially corrected with casting. Please note the skin dimple on the pretibial surface of the affected side.

Diagnostic Tests or Advanced Imaging

AP lower extremity radiograph and two views of the tibia will allow thorough evaluation of bony structures of the patient’s lower extremities to characterize any other deformities and properly classify the tibial deficiency. There are some reports of using MRI or ultrasound to determine the presence of a tibial anlage and the complete anatomy of the distal femur to gain an appreciation of the true function of the extensor mechanism when deciding between amputation types (Figure 13.15).

Treatment and When to Refer

Tibial deficiency is best treated by a pediatric orthopedic surgeon with access to prosthetic services given the vast majority of these patients require amputation of some variety. The child in Figure 13.11 eventually underwent bilateral amputations and prosthetic fitting (Figure 13.16;