Proximal femoral focal deficiency

Proximal femoral focal deficiency (PFFD) is a rare, non-hereditary birth defect that affects the pelvis, particularly the hip bone, and the proximal femur. The disorder may affect one side or both, with the hip being deformed and the leg shortened.

It is commonly linked with the absence or shortening of a thigh bone (fibular hemimelia) and the absence of a kneecap. Other linked birth defects include the dislocation or instability of the joint between the femur and the kneecap, a shortened tibia or fibula, and foot deformations.

Classifications
There are typically four classes (or types) of PFFD, ranging from class A to class D, as detailed by Aitken.

Causes
PFFD is caused by toxins present in the body during pregnancy, with thalidomide being the only confirmed drug to cause the disorder. Other suspected causes include an over-exposure to radiation, and bacterial/viral infections.

Treatment
Depending on the severity of the deformities, the treatment may include the amputation of the foot or part of the leg, lengthening of the femur, or custom shoe lifts. Amputation usually requires the use of prosthesis.

In less severe cases, the use of an Ilizarov apparatus can be successful in conjunction with hip and knee surgeries (depending on the status of the femoral head/kneecap) to extend the femur length to normal ranges. This method of treatment can be problematic in that the Ilizarov might need to be applied both during early childhood (to keep the femur from being extremely short at the onset of growth) and after puberty (to match leg lengths after growth has ended). The clear benefit of this approach, however, is that no prosthetics are needed and at the conclusion of surgical procedures the patient will not be biologically or anatomically different from a person born without PFFD.