The specific cause of PFFD is unknown. It is believed that an anomaly occurs during the 2nd -7th week of pregnancy, and it is considered nonhereditary. Viral and bacterial infections, irradiation, ischemia, hormones, chemicals and mechanical injuries have been included as possible causes.
PFFD involves a short femur in one or both legs, with varying levels of deficiency in the corresponding hip joint. There are several classifications for PFFD, the most common was developed by Dr. George T. Aitken in the early 1960's. Dr. Aitken developed a four class (Class A,B,C,D) classification system based on X-ray results.
- class A
- this is the least severe type where the femoral head is present and attached to the shaft by the femoral neck.
- the femur is shortened (as in all types), and a coxa vara deformity is present
- a cartilaginous neck is not seen on early radiognaphs but later ossifies.
- occasionally, the cartilaginous connection between the neck and the shaft forms a sub trochantenic pseudarthrosis.
- class B
- in this type, the acetabulum is “adequate” or moderately dysplastic and contains the femoral head.
- at maturity, no osseous connection is seen between the femoral head and the shaft.
- the femoral segment is short and usually has a bulbous bony tuft.
- class C
- the acetabulum is severely dysplastic in this form.
- the femoral head is absent or is very small and not attached to the femoral shaft.
- the shortened femoral segment has a tapered proximal end.
- class D
- this is the most severe form, with absence of the acetabulum and proximal femur.
- no proximal tuft is present.
There are common corresponding conditions. Fibular Hemimelia (FH) is present in about one half of all PFFD cases. Often there are foot deformities. People with bilateral PFFD have a greater chance of having additional congenital defects in the upper limbs. Rarely there are also heart defects or cleft palate.
Treatment options for PFFD depend on whether it is bilateral, unilateral, the classification, and the affect on the connected knee and ankle joint.
Non-surgical options include a shoe lift or prosthesis, depending on length discrepancy.
Surgical options include limb lengthening or a Symes or Boyd foot amputation, which may require Super Hip, Super Knee, or possibly Ankle surgery. The most severe cases may consider rotationplasty. Both amputation and rotationplasty will still require a prosthesis post surgery.
References:
1. Kelley, Rachel. Management of Proximal Femoral Focal Deficiency. O&P Business News, April 15, 2007. Available at: http://www.healio.com/orthotics-prosthetics/diseases-conditions/news/print/o-and-p-business-news/%7B384ed75a-2dc7-4a66-9e90-897bdd85bc4d%7D/management-of-proximal-femoral-focal-deficiency. Accessed April 20, 2014.
2. Pediatric Orthopaedic Society of North America. Proximal Focal Femoral Deficiency. Available at: http://www.posna.org/education/StudyGuide/proximalFocalFemoralDeficiency.asp. Accessed April 20, 2014.
3. PFFD VSG2. Pffd - A Guide for Parents and Others. Available at: http://www.pffd.org/a_guide_to_pffd. Accessed April 20, 2014.
4. Skalski, Dr. Matt and Dr Frank Gaillard et al. Classification of Proximal Focal Femoral Deficiency. Radiopaedia. Available at: http://radiopaedia.org/articles/classification-of-proximal-focal-femoral-deficiency. Accessed April 20, 2014.
