PFFD

PFFD stands for proximal femoral focal deficiency. This is a congenital malformation and includes a wide variety of defects in the thigh region. In most cases, the hip joint is underdeveloped as well. It is also referred to as CSF (congenital short femur).

Etiology

Although there are many theories on what causes PFFD, the etiology of the disorder is not yet clear. PFFD is not hereditary. In patients with a mild degree of severity, there is just a slight underdevelopment of the femur, whereas in severe forms, the femur is almost completely missing. In approximately 15% of cases, both legs are affected.

Classification

The most commonly used classification of PFFD was suggested by Aitken. Here, using radiological images, PFFD is classified into the following 4 types:

Type A
Type B
Type C
Type D

Type A

In type A, the acetabulum and femoral head are developed normally. The femur is shortened. On the first radiographs, the femoral head may not yet be visible. The cartilaginous femoral neck ossifies later; frequently, a pseudarthrosis (an abnormal connection of fibrous connective tissue between the bony parts) develops as a result of the ossification problems. However, these ossification disturbances may heal up completely; in many cases, the radiograph will show a severe malposition and significant shortening of the femur.

Type B

While the femoral head is present in type B, a substantial malposition of the femoral neck, which consists of connective tissue, and a significant shortening of the femur can be seen. Here, the connection of femoral head and femoral neck is always a pseudarthrosis.

Type C

In type C, the acetabulum is noticeably deformed, but the femoral head does not ossify. The femoral shaft is very short, and the upper shaft end tapers strongly. The hip is unstable.

Type D

In type D, neither the acetabulum nor the femoral head are present, and the femoral shaft is significantly shortened.

Clinical picture

In children with PFFD, the femur in the affected limb is shortened, depending on the severity of the disorder. In most cases, the hip is spontaneously flexed, abducted and rotated outward. In approximately 60–80% of cases, there is a simultaneous congenital fibular defect. In this case, deformities of the lower leg and foot may be present as well.

Malformations associated with PFFD

  • Congenital fibular defect
  • Shortening of the shinbone
  • Small or missing kneecap; may also be positioned higher than usual or to the side
  • Knee flexion contracture with valgus malalignment
  • Knee instability
  • Absence of the anterior and/or posterior cruciate ligament
  • Foot deformities, shortening, missing toes, fusion of tarsal bones, clubfoot or rocker bottom foot
  • Deformities of the upper or lower extremity of the opposite side

Otherwise, the affected patients are in good physical and mental health.