Femoral neck-shaft angle

Last revised by Dr Joachim Feger on 28 Aug 2021

The femoral neck-shaft angle (NSA) or caput-collum-diaphyseal (CCD) angle is one of the most frequently applied measurements to assess hip morphology, in particular, the relation of the femoral shaft to the femoral head-neck axis.

The femoral head-neck-shaft angle is used in the diagnosis and therapeutic or rather surgical planning of several pathological conditions including the following 1:

The femoral head-neck-shaft angle (NSA) angle is influenced by femoral rotation, which might lead to measurement errors if not considered 1,2.

The angle between the longitudinal femoral shaft axis and the femoral head-neck axis is measured. The axis of the femoral neck is defined by a line bisecting the femoral neck through the center of the femoral head. The longitudinal femoral shaft axis is determined by two bisections of the femoral shaft at different locations 1.

Due to the susceptibility of angle measurements to rotation and to account for the usual femoral anteversion an internal rotation of the feet of 15°-20° is recommended for the standardized acquisition of the pelvis (AP view) 1.

A known normal range of the caput-collum-diaphyseal (CCD) angle is generally considered 125°-135° 3, with a global mean of 126.4° and standard deviations are approximately 5.6° measured with a 360° goniometer in anatomical studies 4. But global median values apparently vary in respect to climate and population being about 125° in the Americas up to 130° in Asians 4.

Widely considered cut-off values are the following 3:

Potential measurement errors radiographically caused by external rotation of the femur can cause a change of >10° in the apparent femoral neck-shaft angle with as little as 7° of external rotation of the femur 2.

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