PFFD stands for proximal femoral focal deficiency. This is a congenital malformation and includes a wide variety of defects in the area of the thigh. In most cases, the hip joint is underdeveloped as well. In the English-speaking world, it is also called CSF (congenital short femur).


Although many hypotheses have proposed causes for PFFD to date, the etiology of the disorder is not yet clear. PFFD is not hereditary. In mild degrees of severity, there is just a slight underdevelopment of the thigh, whereas in severe forms, the thigh is nearly completely missing. In approximately 15% of cases, both legs are affected.


The most commonly used classification of PFFD was suggested by Aitken. On the basis of radiological imaging, it distinguishes 4 types:

Type A
Type B
Type C
Type D

Type A

In type A, acetabulum and femoral head are developed normally. The thigh is shortened. On the first radiographs, the femoral head may not yet be visible. The cartilaginous femoral neck ossifies later, frequently with a pseudarthrosis (an abnormal connection of fibrous connective tissue between the bony parts) as a sign of the ossification impairment. However, this ossification impairment may heal completely, with the radiograph fequently showing a severe malposition with clear shortening of the thigh.

Type B

While the femoral head is present in type B, there is a substantial malposition of the femoral neck. This consists of connective tissue, and the thigh is significantly shortened. Here, the connection of femoral head and femoral neck is always a pseudarthrosis.

Type C

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

Type D

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

Clinical picture

Children with PFFD have, depending on the severity of the disorder, a shortened thigh of the affected limb. In most cases, the hip is spontaneously flexed, abducted and rotated outward. In approximately 60-80% of cases, there is a simultaneous 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, it may alsobe located particularly high 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 rays, fusion of tarsal bones, clubfoot or  rocker bottom foot
  • Deformities of the upper or lower extremity of the opposite side

Otherwise, the afflicted are in good physical and mental health.