Assessment of growth remaining in the long bones of children and adolescents is of great importance in understanding the longitudinal and angular growth of the extremity. As the femur is the longest bone in the axial skeleton, normal or aberrant growth of the femur, particularly involving the distal femoral growth plate adjacent to the knee, greatly affects the overall length and/or angular alignment of the limb.

The growth plates about the knee remain open, and provide longitudinal growth, until the late teenage years. The distal femoral growth plate closes completely at an average age of 18 to 19 years in males and 17 years in females, although there is often little significant growth from this physis after 14 years of age in females and 16 years in males. The proximal tibial physis closes similarly in males at 18 to 19 years and 16 to 17 years of age in females. Typically, the proximal tibial physis closes prior to the distal femoral in most patients. Each of these is susceptible to accidental and iatrogenic injury during a very physically active part of life. Trauma (accidental or iatrogenic), infection, or vascular insufficiency are some of the primary causes of damage to the physis and thereby may cause significant limb length discrepancy and/or angular deformity that may require further surgical intervention or reconstruction (Fig. 38.1).

The growth plate of the distal femur provides more to the longitudinal growth of the lower limb than any other growth plate, and the physis of the proximal tibia is the next most important. The specifics of the histology and microscopic anatomy of the physis, both similarities and differences, are beyond the scope of this chapter. However, the orthopedic surgeon involved in the care of skeletally immature patients with knee injuries, and particularly those performing surgery about the knee, should be well aware of some basic facts regarding the anatomy of, development of, and risk of injury to these growth areas.

Distal femoral physeal injuries comprise approximately 2% of all physeal fractures.¹,²,³ The most common complication of distal femoral physeal fracture is growth disturbance with resultant angular growth abnormality or leg length discrepancy.²,⁴,⁵,⁶ The distal femoral physis possesses less stability against traumatic displacement and injury than the physis of the proximal tibia, which has a rate of traumatic injury approximately half that of the distal femur.²,⁷ The shape of the proximal tibial physis, with the anterior and distal projection of the tibial tubercle as well as the spanning collateral ligaments, and the buttress provided by the proximal fibula are thought to be protective against potentially injuring forces.²,⁷

Angular deformity or shortening have been reported in 39% to 50% of all patients sustaining a distal femoral physeal fracture.²,⁸,⁹,¹⁰ Patients from ages 2 to 12 years appear to be at highest risk of these complications.² The specific mechanism of injury, the type of fracture by Salter classification, as well as the amount of potential growth remaining each play a role in this risk. In addition, there is a change in the anatomy of the distal femoral physis with increasing patient age that may contribute to this increasing rate. The gross anatomy of the distal femoral physis has been shown to be essentially “flat” up until approximately 2 years of age. After that time, the growth plate develops a more undulating course that puts more of the germinal zone of the physis at risk of injury, even in the face of a seemingly radiographically benign fracture pattern.

Management of orthopedic conditions in the face of a constantly changing skeleton is one of the fundamental issues facing the pediatric orthopedic surgeon as well as any physician involved with the care of musculoskeletal problems in children. As such, it is important to be familiar with the methods of assessing current and potential amounts of growth, as well as general development, in children. Many of these require the use of the skeletal (bone) age of the patient rather than the
chronologic age. There are multiple methods available to generate this value.¹¹

The Greulich and Pyle¹² Atlas of Skeletal Development was published originally in 1950 and was based on Todd’s works that were published in 1937. Todd obtained multiple extremity images of 1,000 patients at 3-month intervals during the first year of life, every 6 months from 1 to 5 years of age, and then annually until skeletal maturity. Greulich and Pyle used these radiographs in their atlas to generate a standard for skeletal development of children based on radiographic changes that occur over time in the bones of the hand and wrist, as seen on a left hand and wrist anteroposterior (AP) radiographs (Fig. 38.2). A set of radiographs is provided for males and females due to the differences in skeletal development based on gender. The standard film that most closely resembles that of the patient in question is reported as the skeletal, or bone, age. Concerns exist regarding the validity of assumptions based on radiographic images obtained from patients with health and diet significantly different than found in modern pediatric patients. However, it is difficult to imagine a similar longitudinal radiographic study being generated at this time. Overall, the Greulich and Pyle atlas method is used most commonly at this time to determine skeletal age in pediatric orthopedic surgery.