Slipped capital femoral epiphysis

Slipped capital femoral epiphysis, is a common hip disorder in adolescence, in which the growth plate fractures.

The result is a slippage between the neck of the femur and the overlying head of femur also called the capital or epiphysis.

Normally, a growing femur has 4 main parts.

There’s the diaphysis, which is the long and hard part also called the shaft of the bone, and it extends to the metaphysis, at the level of the femoral neck.

Above the femoral neck, lies the cartilaginous growth plate also called the physis.

The cartilaginous growth plate has cells which divide and enable the bone to grow in length.

These cells are very active in adolescence and they enable a growth spurt.

During this period, the growth plate is relatively weak and vulnerable to shearing forces.

Eventually, the cartilaginous growth plate ossifies and fuses with the epiphysis. This happens around the age of 16 in females, and 19 in males.

Now, before the growth plate ossifies, it’s supported by the perichondrial ring, which is dense connective tissue that extends from the metaphysis to the epiphysis.

The perichondrial ring helps resist shearing forces so that the femoral head and the femoral neck don’t slip away from one another.

You see - the ball-shaped head of the femur comes and sits within the cup-shaped socket called the acetabulum.

This makes a ball and socket type of joint, which is kept stable by tough fibrous joint capsule, and a rope-like ligament known as the ligamentum teres.

The ligamentum teres arises from the base of the acetabulum known as the acetabular fossa, and it attaches to the fovea capitis, the depression found on the tip of the femoral head.

Around the femoral neck there are epiphyseal blood vessels that supply the cells of the femoral head with nourishment.

In slipped capital femoral epiphysis, the perichondrial ring becomes too weak to resist the shearing forces between the femoral head and the femoral neck, causing the two to gradually slip away from each other.

Actually, it’s not the epiphysis that slips away as the name of the disease suggests. Because the epiphysis is well held in the acetabulum by the joint capsule and the ligamentum teres femoris, it’s actually the neck that displaces anterolaterally and superiorly.

That makes it look like it is the epiphysis that has slipped down and backward.

If the displacement is severe it can tear the epiphyseal blood vessels, interrupting the blood supply to the femoral head.