The carrying angle of the elbow is the clinical measurement of the varus-valgus angulation of the arm with the elbow fully extended and the forearm fully supinated. With the arms extended at the sides and the palms facing forward, the forearm and hands are normally slightly away from the body.
The intersection of the axis of the upper arm and axis of the forearm defines the carrying angle. The carrying angle is greater in shorter persons compared to taller persons. The shorter the forearm bone length is, the greater the carrying angle will be. The normal carrying angle of the elbow is between 5-15°. The carrying angle is greater in women and in throwing athletes. It is difficult to assess if there is a flexion contracture of the elbow. This angle permits the forearms to clear the hips in swinging movements during walking, and is important when carrying objects.
Cubitus varus is the opposite of cubitus valgus, causing the elbow to have inward angulation towards the midline of the body. Cubitus valgus is a deformity which causes the forearm when it is fully extended to be angled away from the body in a greater degree than normal. Supracondylar fractures usually occur in children.
If the fracture is malaligned and if it heals in a malaligned position, the fracture may develop into a severe varus deformity of the elbow which decreases the carrying angle of the elbow. This decrease of the carrying angle causes the elbow to have more of an inward angulation towards the midline of the body. This creates what is called a “gunstock deformity”. The deformity is caused by fracture malunion. This is usually a cosmetic deformity with little functional limitation.
A fracture of the lateral condyle of the humerus can lead to:
- Cubitus Valgus
- Stretching of the ulnar nerve
If the fracture did not heal or the fracture is malaligned, the medial part of the humerus will grow and the lateral part will not grow. The forearm will drift into valgus malalignment. The carrying angle will increase (cubitus valgus) and the ulnar nerve will be stretched and may need transposition. The nonunion of the lateral condyle of the humerus may need fixation in order to stop progression of the valgus deformity. 30° of varus or valgus angulation is tolerated in fractures of the humerus without any clinical functional significance.