Surgical Decision-Making in Lower Extremity Deformity and Reconstruction

James R. Kasser

Lower extremity deformity as a concept encompasses a variety of issues including limb length differences, angular deformities, abnormal joint position and function, and atypical girth of the limb or digits. There is a dizzying array of conditions that can lead to these problems, and it is helpful to have a conceptual approach that can be applied broadly and takes into account a patient’s stage in development and expected function short and long term. Often with complex deformity, treatment will span an entire childhood, and developing a “life plan” with a family to ensure appropriate timing of interventions and the extent of nonoperative and operative treatments is critical. What follows is an introduction to the principles of assessment and management of lower extremity deformity in children, with special mention of some of the conditions that will be discussed further in later chapters of this book.

General Approach

The determinants of lower extremity deformity are as follows:

Joint abnormalities including instability, contracture, or malalignment
Muscle dysfunction including weakness, hypertrophy, or spasticity
Connective tissue disorders including laxity or stiffness
Bone deformity including malangulation, malrotation, undergrowth, or overgrowth

The combination of any of these disorders in the multiple segments of the extremity may result in abnormal gait, pain, and/or disability. In evaluating a patient with lower extremity deformity, strength, motion, stability, and angular/length deformity all must be assessed. This is done through a combination of physical examination and imaging in order to make an accurate diagnosis and construct a therapeutic regimen for resolution or improvement of the problem. A common example of this is evident in management of a young child with bowlegs. Clinical factors (age, severity of deformity, symmetry, gait abnormality, among others) suggest whether the deformity is physiologic and dictate whether imaging of the legs is necessary. The radiographic appearance of the legs on long-leg films aids in treatment decision-making, which in some cases may include bracing or surgical intervention. Lower extremity deformity problems in children generally present with a combination of joint abnormality, restricted or excessive motion, angular deformity, weakness, length asymmetry, and dysfunction. Rarely is the problem isolated to bone deformity alone. The problem is not resolved until neutral limb axes are achieved with appropriate joint alignment and stability, normal gait without leg length discrepancy, and restored function without pain.

Etiology

In considering etiology of a lower extremity abnormality, you should consider 2 major categories: congenital and acquired.

Congenital abnormalities or in utero acquired conditions
- Joint dislocations—dislocated hip, knee, or patella
- Malformations—congenital short femur, proximal femoral focal deficiency (PFFD), fibular hemimelia, tibial hemimelia tarsal coalition, club foot, and vertical talus
- Connective tissue abnormalities—arthrogryposis, Ehlers-Danlos syndrome, Marfan syndrome, and osteogenesis imperfecta
- Muscle abnormalities—muscular dystrophies, spinal muscular atrophy, peripheral neuropathies such as Charcot-Marie-Tooth disease, and spasticity resulting from spinal or upper motor neuron lesion
- Under- or overgrowth abnormalities—hemihypertrophy, Beckwith-Wiedermann syndrome, vascular anomalies as examples

For many “congenital” causes of limb deformity, the issues are not limited to a single joint, limb, or body segment. Often multiple organ systems are involved, and you must consider the child as a whole when treating the musculoskeletal manifestations of their disease. Even when considering just their lower limb, an angular deformity or length difference may be the most obvious manifestation; however, there commonly will be joint abnormality with a variable degree of stiffness and/or muscle weakness that must be concurrently addressed.

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