VIDEO: 6-year-old remarkable recovery living with Proximal Femoral Focal Disorder * 2023
VIDEO: 6-year-old remarkable recovery living with Proximal Femoral Focal Disorder * 2023

PFFD – Proximal Femoral Focal Deficiency

Proximal femoral focal deficiency is a complex birth defect in which the upper part of the femur bone (in the thigh) is either malformed or missing, causing one leg to be shorter than the other. This difference causes functional problems with a child’s ability to walk and can stress other bones and joints in the body in an effort to compensate.

PFFD stands for Proximal Focal Femoral Deficiency. It sounds very complicated, 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 centre of the body
Femoral – the thigh-bone or femur
Focal – a focus or starting point
Deficiency – shorter or 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. In most cases, the hip joint is also not well-developed. Proximal femoral focal deficiency (PFFD) is an uncommon condition that affects about 1 in every 200,000 children, and can vary in severity from child to child. Often children with PFFD have other bone and muscle disorders — such as malrotation, limb-length discrepancies, fibular hemimelia, joint instability and muscle weakness — that also must be addressed.

The typical appearance is an unusually short thigh-bone that is pulled upwards and turned toward the outside. The foot of the affected leg is often at the level of the opposite knee. The knee often has varying degrees of instability as well. How well the foot works generally depends on the severity of any associated leg deficiency, such as Fibular Hemimelia. The condition may be one leg (unilateral) or both legs (bilateral).

There are several treatment strategies and alternatives for children with PFFD, however there is not a “one size fits all” solution. For this reason, an experienced multidisciplinary team is needed to develop a customized treatment plan to address the child’s specific needs. Pediatric orthopaedic surgeons, nurses, prosthetic experts and physical therapists must collaborate to determine whether surgery, leg-lengthening procedures, prosthetics — or a combination of these treatments — will offer the child the best chance to increase functionality.

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


Diagnosis and causes

The thigh-bone is measured as part of pregnancy scans. Diagnosis at this stage will depend on the amount of shortening of the bone. In milder cases, diagnosis will only be made at birth or later as the legs start to grow and the difference in length between the two legs becomes more noticeable. Steps have produced a downloadable publication, Leg Length Difference, for parents who have been told of a possible problem with their baby’s legs.

The causes of PFFD are unknown, but it is known that it does not run in families (not genetic). It is likely that a shoe raise (pictured right) will be used as the child grows and learns to walk prior to any surgical intervention. This will be dependent on the severity of the condition and any other problems associated with the hip or knee.

The causes of proximal femoral focal deficiency remain largely unknown, and the disorder does not appear to be genetically linked. In most cases, researchers suspect PFFD is caused by a disruption during early prenatal development, which can be caused randomly or as a result of an outside force such as an infection or trauma.

Researchers have proven that the drug thalidomide, when taken by the pregnant mother, can cause PFFD and other limb deficiencies to unborn children. Pregnant mothers taking this medication for another condition should talk to their doctor immediately about the risk of PFFD and other possible birth defects linked to this medication.

The goal of evaluation is to better understand your child’s anatomy, the severity of their condition, and their functional abilities. In many cases, doctors will order imaging tests such as:

X-rays: Which produce images of bones.

EOS imaging:  Which creates 3-dimensional models from two flat images. EOS images are taken while the child is in an upright or standing position, enabling improved diagnosis due to weight-bearing positioning.

Computed tomography (CT) scan: Which uses a combination of X-rays and computer technology to examine bones and produces cross-sectional images (“slices”) of the body.

Magnetic resonance imaging (MRI: Which uses a combination of large magnets, radiofrequencies and a computer to produce detailed images of organs, soft tissues, muscles, ligaments and other structures within the body. Your child is exposed to no radiation during an MRI.

Hip arthrography: Which uses X-rays and dye injected into the joint to show the soft tissues (ligaments, tendons, cartilage and muscles) of the joint.

Ultrasound: Which uses sound waves to produce images of organs and soft tissues inside the body.
Imaging tests can identify what type of proximal femoral focal deficiency your child has — information that is critical to determining which treatment options will produce the best results for your child.

Types of PFFD

Several classification systems exist detailing different types of congenital anomalies of the femur. Most are based on imaging tests alone, but some also consider clinical presentation. The most widely used classification system divides proximal femoral focal deficiency into four types that include:

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 for proximal femoral focal deficiency

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 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 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.

Children with severe PFFD may require a prosthetic to walk. Because of this, treatment is geared toward improving how your child’s body works with the prosthetic. The goal is to improve your child’s overall function, so they can move and develop at a pace similar to their peers. While the timing of treatment varies from child to child, in most cases it begins when your child turns 3 years old — allowing time for early bone to harden — and is completed by the end of high school, when most children have finished growing.


The first important treatment decision that must be made is whether your child could benefit from limb-lengthening procedures. The most likely candidates to benefit are children with a congenital short femur (Type A PFFD). To be eligible for limb lengthening, a child must have:

  • A femur with a predicted discrepancy at skeletal maturity of usually less than 40 percent of the contralateral femur
  • A stable hip, or one that can be made stable
  • Good function and stability in the knee, ankle, and foot
  • Limb lengthening typically includes surgery to cut the bone, and placement of an internal rod or external fixator to slowly stretch the limb as new bone forms. While traditional treatment includes external fixators, orthopedic surgeons at CHOP are using a new internal technique for limb lengthening that eliminates the need for pins and bulky external fixation frames. Depending on how fast your child’s bone grows; this limb-lengthening procedure can take months and may need to be repeated.


If limb lengthening is not appropriate for your child — either because their leg-length discrepancy is too great or because they will not tolerate the procedures — prostheses should be considered. While most children with proximal femoral focal deficiency will need an above-the-knee prosthesis with a mechanical knee, others with a stable biologic knee may only need a below-the-knee prosthesis. Determining which type of prosthetic device is best for your child’s condition — as well as the best approach to properly fit the device — is the next important decision in your child’s treatment plan.

Initial treatment for children with PFFD should mirror normal development and begin when a toddler is ready to stand. The child is fitted with a custom-molded prosthesis that equalizes leg lengths but does not require surgical correction. In most cases, these prostheses are not large enough to accommodate flexing at both the knee and foot, so developmental growth can be slower. However, a custom-molded prosthesis that accommodates the child’s lower extremity is effective at allowing young children to move around and explore their space.

Additional surgical procedures

As your child grows, the importance of having both a functional knee and foot becomes more important. At this time, decisions must be made about which prosthetic type is most appropriate and which surgical approach will allow the prosthetic to fit optimally.

Additional surgical options include:

Knee arthrodesis:

In which the knee joint is fused to adjacent bones (femur and tibia) allowing for a longer and more stable leg that can be more easily contained within the prosthesis. Foot amputation, in which the leg is shortened to accommodate a mechanical knee and the end of the leg, can be more easily contained within a prosthesis.


In which the ankle assumes the function of a knee. To accomplish this, the limb is surgically cut, rotated 180 degrees and reattached. This allows for improved function due to the use of a biologic knee instead of a mechanical one, and the need for a below-the-knee prosthetic.

Hip stabilization:

In which the hip socket (acetabulum) and femoral head are surgically corrected to address varus deformity (outwardly turned legs) and bone fractures that won’t mend without intervention (pseudoarthrosis). This procedure is only appropriate for children with Type A or B deficiencies. Iliofemoral arthrodesis, in which the knee assumes the function of the hip. In this procedure, the femur is fused to the pelvis so when the child extends their anatomic knee, they are effectively moving their hip. This procedure, which is most often used for children with Type C and D PFFD, is often performed as part of a staged reconstruction with rotationplasty or foot amputation to allow for improved prosthesis fit and enhanced function.

Hip/pelvic osteotomy:

In which a shallow hip socket is reshaped to create better coverage of the ball of the thigh-bone. This procedure is often used to treat acetabular dysplasia. During surgery, the surgeon cuts the bones in the hip joint, reorients them, and secures them in a new position.

Safety in surgery

Surgery can dramatically improve the long-term outcomes for your child with proximal femoral focal deficiency, but it can also be a stressful experience for you and your child. At CHOP, we offer a wealth of resources that can help you and your child prepare for surgery. Additionally, we follow many best practices before, during and after surgery to decrease the risk of infection and increase positive outcomes. Our safety protocols have been so successful that many other institutions have adopted them.

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