Neck-Shaft Angle and Its Importance in Hip Development

The neck-shaft angle primarily refers to the inward angle formed between the femoral neck axis and the femoral shaft axis. In healthy individuals, this angle typically ranges from 120° to 140° for adults and 135° to 145° for children. Deviations from these normal values can be indicative of hip joint abnormalities in children.

1. Normal Range of Neck-Shaft Angle

The femoral neck axis and femoral shaft axis normally form an inward angle, known as the neck-shaft angle or neck angle. The standard range for this angle is 110-140 degrees. An angle greater than the normal range indicates coxa valga (hip valgus), while an angle smaller than the normal range suggests coxa vara (hip varus), also known as developmental coxa vara, a deformity caused by a gradual decrease in the femoral neck-shaft angle during childhood.

2. What is the Neck-Shaft Angle?

The neck-shaft angle refers to the angle formed by the intersection of the longitudinal axis of the femoral shaft and the axis of the femoral neck, also known as the inclination angle. This angle plays a crucial role in enhancing the range of motion in the lower extremities and allowing for effective transfer of force from the trunk to a wider base. Abnormalities in the neck-shaft angle can alter the biomechanical relationships around the hip joint.

In cases of coxa vara, the femoral neck experiences reduced compressive forces, leading to an increase in tensile trabeculae and a decrease in compressive trabeculae. Conversely, in coxa valga, the opposite phenomenon occurs.

3. Management of Hip Abnormalities in Infants

If hip abnormalities are detected in infants, several management strategies can be employed:

• Minor abnormalities may be corrected with the use of braces. Moderate to severe cases may require surgical intervention, as untreated hip abnormalities can lead to disabilities.
• When holding the infant, it is recommended to separate the legs in a frog-like position to avoid long-term twisting of the bones, which can predispose to hip dislocation and incomplete hip development. Encouraging the infant to lie flat and kick their legs can also be beneficial.
• Regular observation of the infant's leg and buttock creases is important to detect any asymmetries or differences in leg length. Additionally, during diaper changes, note any limited range of motion or asymmetry in hip flexion. If any of these signs are observed, prompt evaluation with an ultrasound scan and medical intervention is recommended.