Proximal femoral focal deficiency (PFFD), also known as Congenital Femoral Deficiency (CFD), is a rare, non-hereditary

birth defect A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities ca ...

that affects the pelvis, particularly the hip bone, and the proximal

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...

. The disorder may affect one side or both, with the hip being deformed and the

leg A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element ca ...

shortened. It is commonly linked with the absence or shortening of a leg bone (

fibular hemimelia Fibular hemimelia or longitudinal fibular deficiency is "the congenital absence of the fibula and it is the most common congenital absence of long bone of the extremities." It is the shortening of the fibula at birth, or the complete lack thereof ...

) and the absence of a

kneecap The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as m ...

. Other linked birth defects include the dislocation or instability of the joint between the femur and the kneecap, a shortened

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity i ...

, and foot deformities.

Causes

The cause of PFFD is uncertain. Two hypotheses have been advanced. The theory of sclerotome subtraction posits injury to neural crest cells that are the precursors to sensory nerves at the level of L4 and L5. Histologic studies of a fetus with unilateral PFFD have prompted an alternative hypothesis that PFFD is caused by a defect in maturation of chondrocytes (cartilage cells) at the growth plate. In either hypothesis, the agent causing the injury is usually not known.

Thalidomide Thalidomide, sold under the brand names Contergan and Thalomid among others, is a medication used to treat a number of cancers (including multiple myeloma), graft-versus-host disease, and a number of skin conditions including complications o ...

is known to cause PFFD when the mother is exposed to it in the fifth or sixth week of pregnancy, and it is speculated that exposure to other

toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849 ...

s during pregnancy may also be a cause. Other etiologies that have been suggested, but not proven, include anoxia, ischemia, radiation,

infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dis ...

hormone A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are require ...

s, and mechanical force. PFFD occurs sporadically, and does not appear to be hereditary.

Diagnosis

Classifications

There are typically four classes (or ''types'') of PFFD, ranging from class A to class D, as detailed by Aitken. Types of PFFD Type A — The femur bone is slightly shorter on the proximal end (near the hip), and the femoral head (the ball of the thigh bone that goes into the hip socket) may not be solid enough to be seen on X-rays at birth, but later hardens (ossifies). This deformity is sometimes called congenital short femur, because the child’s anatomy from hip to knee is contiguous and similar to their peers except for the one shortened bone. In some cases, children with type A deformities will also have an externally rotated femur, which could lead to bowing of the legs (genu varum). Type B — The femur bone is shorter on the proximal end (near the hip) and the defect affects both the femoral head (the ball) and the femoral shaft (the long part of the bone). This defect is more severe than type A deformities because it will not heal spontaneously and, at skeletal maturity, the proximal femur (lower part near the knee) will not connect with the femoral head. Type C — The entire top half of the femur bone is absent, including the trochanters (the part of the bone in which muscles are attached to the upper thigh), and the femoral head. In type C deformities, the proximal femur is not connected to the hip in any way. In fact, many children with type C deformities also have acetabular dysplasia, a condition in which the acetabulum (hip socket) is shallow, abnormally shaped, and oriented outward. Type D — This is the most severe form of proximal femoral focal deficiency, in which most of the femur bone is absent and only a small irregular piece of bone above the distal femoral epiphysis (the end of the femur bone at the knee) is present. In the pelvis, no acetabulum (hip socket) is present; instead the pelvic wall is flat on the affected side.

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, extension prosthesis, or custom shoe lifts. Amputation usually requires the use of prosthesis. Another alternative is a

rotationplasty Rotationplasty, commonly known as a Van Nes rotation or Borggreve rotation, is a type of autograft wherein a portion of a limb is removed, while the remaining limb below the involved portion is rotated and reattached. This procedure is used when a ...

procedure, also known as Van Ness surgery. In this situation the foot and ankle are surgically removed, then attached to the femur. This creates a functional "knee joint". This allows the patient to be fit with a below knee prosthesis vs a traditional above knee prosthesis. In less severe cases, the use of an

Ilizarov apparatus In medicine, the Ilizarov apparatus is a type of external fixation apparatus used in orthopedic surgery to lengthen or to reshape the damaged bones of an arm or a leg; used as a limb-sparing technique for treating complex fractures and open bone ...

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. In some cases the patient may not request treatment and instead elect to use a wheelchair or other aids to assist mobility.

References

External links

{{Medical resources , ICD10 = {{ICD10, Q72.4 Congenital disorders of musculoskeletal system