Introduction to PFFD and Congenital Femoral Deficiency

Receiving a diagnosis of Proximal Femoral Focal Deficiency (PFFD), also increasingly known as Congenital Femoral Deficiency (CFD), can feel overwhelming. You may be searching for answers or wondering if something you did caused this. It is important to know right away: this is a rare, random developmental event. It is not your fault, and it is not a “disease” that will spread or worsen over time ^[1][2].

Understanding the Names: PFFD vs. CFD

In the past, doctors primarily used the term PFFD to describe cases where the upper part of the thigh bone (the femur) was significantly malformed or missing ^[3]. Today, many specialists prefer the term Congenital Femoral Deficiency (CFD) ^[4].

• Congenital simply means “present at birth.”
• Femoral Deficiency means the thigh bone did not grow to its full length or shape during pregnancy.

While the terms are often used interchangeably, CFD is now considered a more inclusive “umbrella term” that covers everything from a slightly short thigh bone to a more significant absence of the bone ^[3][5].

Why This Happens: The “Vascular” Theory

The most widely accepted explanation for PFFD/CFD is a theory called vascular dysgenesis ^[6]. Between the 4th and 8th weeks of pregnancy, the tiny blood vessels that feed the developing limb must grow in a very specific pattern. If there is a temporary disruption or a “glitch” in the blood flow to the femur during this critical window, the bone cannot form correctly ^[6][7].

Think of it like a construction project where the materials (blood and nutrients) were briefly delayed during the week the foundation was being poured. The rest of the “house” (the baby) continues to develop normally, but that specific part of the foundation is built differently ^[6].

Three Stabilizing Facts for Parents

1. It is not hereditary. Isolated PFFD/CFD is a sporadic event, meaning it happens by chance ^[2]. It is not caused by your genetics, and there is no evidence of an increased risk for your future children or for your child’s own future children ^[6][2]. (Note: While isolated PFFD is sporadic, doctors may recommend a brief genetic consultation just to completely rule out broader syndromes.)
2. It is extremely rare. This condition occurs in only about 1 to 2 out of every 100,000 births ^[1][8]. Because it is rare, it is essential to find a medical team that specializes specifically in “limb length discrepancies” or “congenital limb differences.”
3. Children are incredibly adaptable. Children with PFFD/CFD typically meet their developmental milestones—sitting up, crawling, and playing—though they may do so in their own unique way. Modern medicine and prosthetics offer a wide range of pathways to ensure your child can be active and mobile ^[9][10].

What to Expect in the First Year

If you are a parent of a newborn, you may be wondering what happens right now. In most cases, the first 1 to 2 years involve observation and planning. Your child will not immediately go into major surgery. They will learn to sit, crawl, and eventually walk—often using a shoe lift or a custom-fitted early prosthesis. This time gives you the space to meet with specialists, gather scans, and carefully build a long-term treatment plan.

What You Might See at Birth

Every case of PFFD/CFD is unique, but the initial physical presentation often follows a specific pattern ^[3]:

• Shortened Thigh: One leg appears significantly shorter than the other.
• External Rotation: The affected leg may naturally turn outward.
• “Frog-Leg” Position: The infant may hold the hip in a flexed (bent) and abducted (spread apart) position ^[3].
• Foot and Knee Involvement: Sometimes the foot or the smaller bone in the lower leg (the fibula) is also affected ^[11].

Moving Forward

In the coming weeks, your doctors will likely use X-rays or an MRI (a detailed scan) to look for the femoral head—the “ball” part of the hip joint ^[12][13]. Knowing whether that ball exists is a key piece of information that will help your team determine the best path forward for your child’s mobility ^[14][15]. While the road ahead involves many decisions, the goal of all modern treatment is the same: a happy, mobile, and active child.