PFFD - Medical Explanation

PFFD stands for Proximal Femoral Focal Deficiency. It sounds very complex, but when you look at each word individually it is actually a very good description of the condition.

* Proximal - nearest the point of attachment or center of the body
* Femoral - pertaining to the thigh bone or femur
* Focal - pertaining to a focus or starting point
* Deficiency - a lack; less than the normal amount

In other words, the end of the thigh bone closest to the hip is too short or not completely developed.

Etiology (What causes it?)

As a fetus develops the location of each cell and its surroundings determine how
the cells and tissues develop. The process is called morphogenesis. If something goes wrong in morphogenesis, the time at which it occurs influences the occurance and type of effect. If something occurs at a primary stage it is called a "malformation." (As opposed to a "deformation" which is usually at a later stage and arises from mechanical factors. )

Limb buds on the fetus develop at about 28-32 days into pregnancy and at 33-36 days the foot plate is visible. If something affects the growth of the fetus around this critical limb-formation time (4 - 6 weeks) it can lead to PFFD. A teratogen" is the term given to the agent that causes a malformation in an embryo or fetus.

The teratogen for PFFD is unknown. PFFD is not genetic. Some have proposed that it is caused by anoxia (oxygen deficiency), ischemia (temporary blood supply deficiency), chemicals, hypothermia, radiation, bacterial toxins, viral infections, enzyme and hormone changes.

Embryology (How does it happen?)

 

Limb development occurs during the first 2-7 weeks of fetal life. The limb buds start to develop by 32 days. The most proximal (toward center) parts of the limbs develop first, followed by the hands and feet, which are fully formed by the seventh week. The acetabulum (hip socket) and the femoral head and neck develop from a common block of cartilage, with subsequent cleft (opening) to create a hip joint cavity

The cleft gradually separates until a definite joint cavity is formed. This point is critical for proper diagnosis. The presence of an adequate acetabulum on early (1st year) X-rays always means that the femoral head is also present - even though the femoral head's development may be delayed and the femoral head itself may not be visible on the X-ray. Similarly, if no acetabulum can be seen, no femoral head will develop.

Whatever affects the developing limb bud during the first 2-7 weeks can also affect muscle development in the thigh, knee joint, and sometimes in the lower leg.

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