To effectively care for patients with congenital lower limb malformations, clinicians must be able to identify and appropriately refer patients with lower limb malformations. Treatment requires an understanding of the balance between psychosocial considerations and nonoperative and operative treatment options at different points in childhood. This optimization of care can lead to significant improvements in quality of life, especially considering recent advances in the development and availability of prostheses.After completing this article, readers should be able to: Identify the difference between malformation, deformation, disruption, and dysplasia.Describe the embryologic development and pathogenesis of lower limb malformations.List the steps in diagnosing lower limb malformations and associated anomalies, including the indications for subspecialty referral.Explain the psychosocial implications of lower limb malformations in the developing adolescent.Discuss nonsurgical and surgical treatment options for the child with a limb malformation.Lower extremity malformations are rare, occurring in 2.1 to 5.6 of 10,000 births. They are encountered in the hospital and office-based pediatric setting during prenatal and newborn screenings, primary care, and subspecialty evaluations. Parents and families are often overwhelmed by the diagnosis of a major limb malformation and the implications for the child’s quality of life and function as the child matures. Prompt identification is essential in this population because a limb malformation may be the most obvious presenting sign of a genetic syndrome associated with other abnormalities of organogenesis. Appropriate early subspecialty referral and treatment can help mitigate some of those fears and optimize patient function and psychosocial development through a combination of nonoperative and operative modalities. The aim of this review is to provide an orthopedic perspective on the initial evaluation, diagnosis, and management of major lower extremity malformations (excluding the foot and toes) as it pertains to the pediatric population.An understanding of lower extremity malformations requires knowledge of the nomenclature and of the various pathogenic mechanisms that can result in a pediatric limb deformity. In general, the term deformity is used as an umbrella term to describe any deviation from normal development and lower extremity alignment. In describing limb abnormalities, Hennekam et al (1) discuss 4 terms that can be used to describe lower extremity disorders: malformation, deformation, disruption, and dysplasia. These terms are helpful to consider because they convey information regarding both pathogenesis and morphology. A malformation is a nonprogressive abnormality of a single organ or body part due to an alteration of development that typically occurs during the sensitive phase of limb bud development (eg, tibial hemimelia), and is the focus of this review. In contrast, a deformation is an alteration in structure due to abnormal mechanical forces in otherwise normal development. This can occur either prenatally at any phase of fetal development (eg, metatarsus adductus) or postnatally (eg, adolescent tibia vara) and can either resolve or persist. A disruption is a nonprogressive abnormality of a body part that had interrupted, but otherwise normal, development (eg, amniotic band syndrome). Last, a dysplasia is an anomaly with ongoing altered development due to underlying cellular abnormalities (eg, achondroplasia). The term deficiency may be used to describe a limb that is missing a significant portion of its normal structure due to malformation, disruption, trauma, or another etiology. Any of these developmental processes has the potential to lead to lower extremity deformity.Several classification systems have been described for categorizing limb deficiencies. (2)(3) In clinical practice, descriptive language is the most helpful to understand. Deficiencies may be either transverse (all distal structures missing) or paraxial (one side of a limb is involved). Paraxial deficiencies may develop on either the preaxial or postaxial sides, the terminology of which is derived from the limb bud development. In the lower extremity, preaxial refers to the tibial side of the leg and postaxial refers to the fibular side.Limb reduction defects as a whole have been reported in national population surveillance data at a rate of 2.1 to 5.6 per 10,000 births. (4)(5)(6) In this heterogeneous group, isolated upper extremity malformations typically account for the majority (60%–65%), and combined upper and lower extremity involvement (8%–10%) and isolated lower extremity involvement (20%–25%) are less frequent. (4)(5)The pathogenesis of limb malformations is multifactorial owing to the complex and highly regulated nature of limb bud development in utero. A general understanding of this process is helpful to conceptualize abnormalities. Limb bud development begins at the end of week 4 after fertilization, with a bud of tissue expanding outward from the mesoderm, reaching completion by the end of week 8. (7) Recent research suggests that the limb development is driven, in part, by signaling gradients that lead progenitor cells to develop specification regarding their final structure (eg, anterior/posterior and proximal/distal structure specification). (8)(9)(10)(11) This remains an active area of research and is beyond the scope of this review.Because limb bud development is a highly coordinated and sensitive process, interference with normal gradient signaling during this phase has the potential to result in limb malformation. Although the association of thalidomide with limb deficiencies is now universally understood, malformations may result from a variety of causes, including genetic or cytogenetic defects, vascular dysgenesis, fetal exposure to certain medications (such as phenytoin or valproic acid), teratogens, smoking, viral infection during pregnancy, maternal diabetes, or a combination of these causes, among others. (5)(12)(13)(14) In some cases, a precipitating etiologic trigger may not be identified. Because the timing of limb development is consistent, prenatal diagnosis is possible even very early on, with major lower limb malformations evident radiographically by day 31 and more distal deficiencies by day 37. (10)Major limb malformations may be detected during first-trimester prenatal ultrasonography, although sensitivity varies among centers. (12)(15)(16)(17) At the end of the second trimester, three-dimensional ultrasonography or low-dose fetal computed tomography can be used to make a detailed diagnosis, when necessary. (18) Monitoring intrauterine long bone growth has been facilitated by the availability of standardized charts depicting growth between 12 and 42 weeks of gestation, which has facilitated recognition of malformations. (19) Although prenatal diagnosis is not always possible, when given the option, a prenatal diagnosis was preferred by 63% of mothers in 1 study, (17) in part because of the benefits of maternal counseling and postnatal care coordination.After birth, the general pediatrician plays an important role in the initial evaluation of the patient, which includes seeking to confirm the diagnosis, screening for additional anomalies, and facilitating coordination of care with various subspecialists. Nearly half of patients with lower limb deficiencies have other major anomalies involving the axial skeleton, internal organs, or nervous system. (6) Consideration should be given to early cardiopulmonary and urogenital screening because the incidence of anomalies has been reported to be 12% and 15% of this population, respectively. (6) Although a significant cardiac abnormality would often be identified clinically, renal anomalies could be occult and renal ultrasonography should, therefore, be considered in higher-risk patients. In general, for the purposes of referral and additional testing, patients with bilateral findings, preaxial deficiencies, and features suggestive of other organ involvement or VACTERL syndrome (vertebral anomalies, anal atresia, cardiac defects, tracheoesophageal fistula, esophageal atresia, renal and radial abnormalities, other limb abnormalities) warrant further screening. (14)From a musculoskeletal perspective, confirmatory diagnosis can occasionally be made without imaging, but typically radiographs are required, with some role for ultrasonography and/or magnetic resonance imaging to help assess cartilage and soft tissue involvement. (18) It is the opinion of the author that all, even seemingly minor, lower extremity malformations warrant orthopedic referral for establishment of care, counseling of the possible orthopedic sequelae associated with the specific condition, and radiographic monitoring until skeletal maturity.A detailed discussion of specific malformations is beyond the scope of this review, but an overview of lower extremity malformations is summarized in Table 1. Depending on the type and severity, lower extremity disorders have the potential to cause LLDs, angular deformity, and joint instability. On occasion, a malformation can be so mild as to go unnoticed, but in other cases the affected extremity can be nearly absent, so a highly individualized approach to evaluation and treatment is required.Lower extremity growth is dependent on several factors, and, as a result, leg length discrepancy (LLD) may develop for a variety of reasons, including trauma, infection, inflammatory arthritis, irradiation, genetic syndromes, or congenital differences. Depending on the etiology of the discrepancy, predictions can be made regarding the projected discrepancy at adulthood. Although occasionally some lower extremity discrepancies initially worsen before stabilizing, most increase steadily with time at a proportionate growth rate to the contralateral extremity. (20) By understanding this, the orthopedic surgeon is often able to counsel patients beginning at very young ages about their projected LLD. This early counseling facilitates the early initiation of long-term treatment planning, particularly for those who may be considering amputation versus limb reconstruction.Clinically, children adapt very well to even moderate LLDs. Small discrepancies rarely cause major issues and may not even be noticed depending on the age of the child. As such, a discrepancy of less than 2 cm is typically treated conservatively with a shoe lift or observation alone. Patients with more moderate discrepancies may walk or stand with 1 side of the pelvis tilted down, or may walk with toe-walking or knee flexion to help achieve a neutral trunk position. Patients with marked discrepancies (>7 cm) typically require a combination of compensation strategies to effectively ambulate. (21) As children age into adulthood, LLDs that may have been well-tolerated in childhood have the potential to cause symptoms such as pain, joint contractures, gait abnormalities, and concerns with appearance. The relationship of scoliosis to LLD is complicated. An LLD of greater than 2 cm has the potential to cause a functional (ie, nonprogressive scoliosis in a structurally normal spine) scoliosis that may disappear with correction of the discrepancy. (22)(23) However, LLD can also develop as an adaptive change due to idiopathic scoliosis, and as such a cause-and-effect relationship is difficult to ascertain. (24)Traditional teaching is that LLDs in children are managed based on the projected discrepancy by skeletal maturity. Classically, discrepancies projected to be less than 2 cm at maturity are best treated with a shoe lift, discrepancies between 2 and 5 cm at maturity are best treated with a growth-slowing procedure such as epiphysiodesis, and discrepancies between 5 and 20 cm or more can be treated with some combination of limb lengthening, epiphysiodesis, and/or amputation. Therapy is discussed in further detail in the General Treatment Principles section of this article.Normal lower extremity alignment has been well described by Paley, (25) and any deviation from normal has the potential to cause problems due to alteration in articular contact pressures (26)(27) or gait dynamics, (28)(29) in addition to concerns with appearance. Angular deformity may occur due to the loss of an osseous structure or the presence of a joint contracture resulting in a static deformity, for example, in patients with absent fibulae or hypoplastic femoral condyle. If angular deformity is significant, gait dynamics can be altered, and feelings of instability may occur while the affected patient participates in activities of daily living or athletics.Lower extremity malformations are not limited to the skeleton, and thus consideration must be given to the surrounding soft tissue envelope, especially regarding contracture and incompetent ligaments. A general rule of thumb is that the joints adjacent to the primary zone of malformation are potentially involved as well. For example, patients with femoral deficiency often have acetabular dysplasia and may have anterior cruciate ligament insufficiency, which can contribute to hip or knee subluxation during a lengthening procedure if adjacent bone and soft tissue restraints are not addressed. Similarly, patients with fibular hemimelia may have anterior cruciate ligament laxity and ankle instability, which also can result in subluxation and contracture during lengthening. Failure to consider these dynamic and static joint stabilizers can result in major, and often avoidable, complications during surgical treatment. In some cases, soft tissue involvement is the primary determinant in making the decision for amputation. (30)Treatment of lower extremity malformations is individualized owing to the variability of clinical features and patient and family preferences. Although some authors have found that children with lower extremity differences have similar psychological functioning as the general population, (31) more recently the health-related quality of life measures have been shown to be lower in children with congenital differences. (32) Specifically, children often feel limited in their ability to participate in physical activities, feel isolated from peers after missing countless days of school for treatment, and feel a great deal of anxiety surrounding the appearance of their leg, be it the leg itself, an external fixator used for treatment, or the resulting gait challenges. (32) Reducing the visit burden and determining the specific treatment modality are of utmost importance and should be coordinated between practitioners involved in a child’s care. Furthermore, educating patients and their families on support groups and services that exist should be a priority. Most major health systems have websites with a comprehensive list of resources and in-patient support networks available to patients and their families regarding lower limb defects, and there are multiple national support and advocacy groups as well (Table 2).Treatment can improve health-related quality of life and psychosocial functioning, even in the face of objective motor function differences. (32)(33)(34)(35) A holistic approach to limb reconstruction is, therefore, warranted considering that physical appearance, physical and psychological health, effects on school life, and social well-being are all important determinants of quality of life for children and their families. (32) For older children and adolescents, additional consideration of their perceptions of treatment, the role of the hospital experience, the patient (not parent)-physician relationship, peer interactions, and parental relationships becomes important. (33)In patients in whom amputation must be considered, authors have reported that early education of both the patient and their parents regarding rehabilitation and the importance of physical activity have extremely positive effects. (36) Specifically, involvement in sports has a strong positive influence on self-esteem, perceived body image, and locus of control. Although many sports and activities exist for patients who cannot afford prostheses or find them intolerable, highly developed and individualized prostheses are being made increasingly available and should be discussed before surgical intervention. (37) Significant strides have been made in the surgical techniques used to facilitate optimal stump formation, as well as the science of lower extremity prostheses so that now prostheses more closely simulate native joint function. Ultimately, children with amputations require close monitoring of their prosthesis as they grow and of their psychosocial well-being as they mature.Although it is tempting, and in many ways ideal, to offer a comprehensive treatment plan to families at the initial evaluation, this is not always possible or helpful. Typically, we counsel patients that the mainstays of treatment include routine follow-up visits, radiographic surveillance when warranted, and the offer of nonoperative and/or operative interventions as necessary depending on the individual situation and phase of life. In particular, when discussing treatment options for LLD and angular deformity, we ensure that families understand that some treatments, such as hemiepiphysiodesis and epiphysiodesis (described later herein), are available only during the growing years, after which more complex surgery may be required.Mild malformations that are well-tolerated and unlikely to result in long-term symptoms may be treated with observation and clinical follow-up alone. In symptomatic patients who may not be ready or indicated for surgery, orthoses play an important role, for either temporary or definitive management. In contrast to a prosthesis, which is an artificial substitute for a missing structure, an orthosis is meant to provide support to a native body part to optimize function. A wide range of orthoses are available, and specific orthosis selection depends on the functional goal and the needs of the patient (Fig 3). Shoe lifts, supramalleolar orthoses, and ankle-foot orthoses are frequently used to balance leg lengths and help provide joint stability, relieve pain, and improve function. These orthoses can be customized as necessary. In cases of amputation, a variety of prostheses may be used depending on age, activity level, and function. Occasionally, a combined prosthesis-orthosis may be the best option for a patient with a significant discrepancy who is otherwise unable to use a traditional prosthesis or orthosis (Fig 3E). Physical and other therapies are indicated throughout development, especially during periods of rapid growth and after operative intervention.Skeletally immature children with moderate LLDs and/or angular deformities may be candidates for growth modulation (Fig 4). Each physis in the lower extremity grows at a specific rate that allows the calculation of a child’s projected discrepancy at maturity. The concept of growth modulation relies on the principle that extraphysiologic axial forces across a physis alter the standard growth rate. As such, growth can be slowed over time by tethering either all or part of a growth plate. When growth on the longer leg is slowed across an entire physis (epiphysiodesis), the shorter leg is then able to catch up and LLD is reduced. In contrast, when growth is slowed on only half of the growth plate (hemiepiphysiodesis), the untethered side of that physis continues to grow and angular deformity is reduced. (38)(39) Historically, epiphysiodesis has been performed for projected discrepancies between 2 and 5 cm at maturity, although this threshold may be changing as limb lengthening is now being performed successfully in patients with discrepancies in this range. (40) Both epiphysiodesis and hemiepiphysiodesis remain important elements in the management of this patient population, either in isolation or as an element of a more comprehensive surgical approach.Ultimately, many patients are faced with the complex decision of whether a limb should be reconstructed or amputated. This is an area of ongoing debate in the orthopedic community.Limb lengthening and reconstruction has traditionally been indicated in patients projected to have discrepancies of 5 to 20 cm at maturity (Fig 5). Historically, this has involved the use of an external fixator, in which pins and wires are placed percutaneously into the bone and the limb is gradually lengthened by small adjustments of the frame over weeks to months. Although external fixation is still frequently used, the more recent development of internal lengthening nails has been widely adopted by pediatric orthopedic surgeons and has led to fewer complications and improved patient outcomes compared with external fixators. (41)(42) In brief, the standard method of using an internal lengthening nail is by performing an osteotomy of the bone undergoing lengthening, placing a motorized telescoping nail into the bone’s intramedullary canal, and securing it proximally and distally. Then, when the internal mechanism is activated, it causes the nail to lengthen, which in turn lengthens the bone. The patient and family have a substantial responsibility in this treatment, as they ultimately have to perform the lengthening routine several times daily until the goal is achieved. Other techniques have been developed to perform intramedullary, (43)(44) extramedullary, (45)(46) and deformity correction with the nails. (47) However, limb lengthening is limited by soft tissue contracture, joint instability, and amount of length desired.Ultimately, for many patients with significant congenital limb differences, multiple procedures throughout childhood are required. This can include as many as 2 or 3 limb lengthening procedures, preparatory surgery to address hip dysplasia or joint instabilities, secondary operations for implant removal or contracture releases, and unexpected operations to address any obstacles that arise during treatment. Each episode of care often requires prolonged recovery, time out of school, and the need for extensive physical therapy, which can be a burden to the patient and family and cause a significant disruption to childhood. In addition, the effects of prolonged and repeated episodes of general anesthesia in developing children should be considered by the surgeon and family before embarking on a reconstructive pathway. (48)(49)(50)Because of this, some authors propose amputation as the best option for patients with significant limb malformations at presentation. A recent meta-analysis of patients with fibular hemimelia demonstrated better patient satisfaction, fewer surgical procedures, and fewer complications with amputation compared with reconstruction. (51) Amputation may also be a primary consideration in tibial hemimelia, (30) proximal focal femoral deficiency, (52)(53) and congenital pseudarthrosis of the tibia. (54) Although amputation clearly has a role, it is a very difficult decision for parents to make on behalf of their children. Shared decision-making and ongoing, open dialogue are essential for management of these children. Ultimately, regardless of whether limb reconstruction or amputation is chosen, most patients and families are satisfied 2 years after surgery and report similar overall functioning in mid-childhood. (55)Lower extremity malformations and limb deficiencies can result in a wide spectrum of clinical findings with the potential need for lifelong orthopedic treatment. It is important to recognize malformations early in life so that patients can receive appropriate systemic evaluation, early therapy, prosthesis and orthosis fitting, and surgical management when appropriate. Early orthopedic and subspecialty referral is warranted in this population so that children with limb differences can maximize their developmental potential. The pediatrician plays a key role in orchestrating the multidisciplinary team necessary to provide complete care to the children with these rare but impactful diagnoses.Patients with a limb deficiency and their families are burdened by the need to attend multiple, frequent appointments, including to a variety of subspecialists, therapists, and orthotists. As a result, children and caregivers may accumulate repeated absences from school and work. To optimize the care of these patients, a multidisciplinary limb deficiency clinic could offer efficient and coordinated care by maximizing the time spent at appointments and lowering health-care costs. Such a clinic may include orthopedic surgeons, geneticists, pediatric psychologists, physical/occupational therapists, and orthotists/prosthetists. This would allow the providers to address the patient and their family as a team to answer questions and concerns more comprehensively and minimize miscommunications regarding the treatment plan or goals of care. This would also decrease the number of days dedicated to appointments and decrease the stress on families faced with a complicated diagnosis. A survey could be conducted to evaluate the time spent, opportunity cost, and economic burden that patients report in the typical care model compared with the multidisciplinary clinic model.We acknowledge Gregory Armstrong, BSPO, CPO/L, FAAOP, who provided images for commonly used prostheses and orthoses.
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Apr 10, 2024
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