Q.

What is the most likely diagnosis, how do you classify and what are the treatment options?

A.

The image demonstrates a plain ap radiograph of the femur and hemipelvis of a child. The triradiate and distal femoral physes are open. The proximal portion of the femur is missing. The acetabulum is very dyspastic. There seems to be a large soft tissue mass shadow in the thigh.
These findings are consistent with the diagnosis of proximal femoral focal deficiency or PFFD.
There is no history of previous infection or surgery and the childs leg was short, flexed, abducted and externally rotated from birth.

For those unfamiliar with this disorder here are a few answers and questions.

What causes PFFD? Unknown!
Something interfers with proximal femoral development and probably occurs in the first 2 to 7 weeks of gestation. The same process may interfer with other parts of the limb.
If the femoral head forms but there is discontinuity between it and the shaft then the acetabulum will develope to some degree around the head. If the head is also absent the acetabulum has no mould and remains dysplastic. Muscle development is also deficient in the area but the telescoping effect of the limb creates the soft tissue bulge in the thigh seen clinically and on radiographs. The ACL is frequently deficient. There may be some degree of fibular hypoplasia in up to 70%. The foot may be involved. Other limb deficiencies may be seen in up to 50% of cases. 15% may be bilateral.
There are other unrelated conditions occasionally seen in newborns, such as an isolated deficiency of the quadricepts muscle ( and thus a knee flexion contracture) which some believe to result from embryonic vascular disruption or embolisation. In theory a similar event may create a PFFD.

Do all PFFDs look the same?
No. There is a sectrum of proximal deficiency. There are several classifications. The simplist to remember is that of Aitken who described 4 classes (A to D).
Aitken Class A is the mild end of the spectrum. There is a radiographic defect between the femoral head and shaft but this eventually ossifies. The result is a coxa vara and short femur. A valgus osteotomy may be necessary.
Aitken Class B is similar but the defect never ossifies and a pseudoarthrosis persists. However there is a femoral head and reconstruction is possible.
Aitken Class C is more severe with more shortening and little or no head and therefore a dysplastic acetabulum.
Aitken Class D is the severe end of the spectrum with no acetabulum nor proximal femur and a very short femoral stump. The knee is adjacent to the ilium. The femoral fragment may not be initially visible but ossifies later.

What is the treatment of Bilateral PFFD?
The goal, as always, is to improve function first and then consider cosmesis.
Treatment decisions in PFFD are weighted by bilaterality, severity (Aitken class A and B versus C and D) and the quality of the foot/ankle complex.

Bilateral PFFD patients are very functional, often Aitken D's and symmetrical. They may have other limb deficiencies and may use their feet as hands. As infants they mobilize remarkably well. As children they benefit from non-conventional extension prostheses which hold their feet in equinus and give them height. At home they often discard the prostheses, especially if there are hand or arm deficits. The vast majority of Bilateral PFFD patients are therefore treated without surgery.

What are the treatment options in unilateral PFFD's, or Aitkens Classes A and B and Classes C and D?
As an infant such a child will mobilize very well and accomadate for the short leg by flexing the normal one. The parents are councelled and introduced to similar children and their families.
An important principle in this disorder ( and other congenital limb deficiencies) is that the percentage lenght discrepancy is constant throughout growth. Therefore a 10% LLD at birth ( measuring perhaps 1cm) will be a 10% LLD at maturity ( measuring perhaps 4 cm ;as determined from the Green Anderson charts on femoral length). Therefore one can advise the parents as to the predicted discrepancy and therefore the possibility for lengthening.
It has been suggested that those with a predicted overall LLD at maturity of 15 cms or less may be amenable to hip stabilization and lengthening with contralateral epiphysiodeses whereas those with more than 20 cms LLD at maturity are better suited by amputation and prosthetics. Between 15 and 20 cm there is some disagreement.

At the proximal end of the limb there is a short femur and an unstable or varus hip joint in the milder cases. There will be a flexion contracture at the hip and knee.
In Aitken Classes A and B it may be possible to stabilize the hip joint surgically using a valgus osteotomy and bone grafting of the resected pseudoarthrosis. Despite bony correction the hypoplastic proximal muscles will usually result in limited functional success. Most continue to have a Trendelenburg gait.
If the femur is too short to lengthen and the knee is unstable and very proximal, a knee arthrodesis improves the mechanical status of the upper limb for prosthesis wear.

Regarding the foot there are several options. The first is to leave it but this makes prosthesis wear difficult. In the very mildest cases itis possible to leave the foot , stabilize the hip and lengthen the femur. Most are too severe for this option.
The second is to improve prosthesis wear by performing a Syme's amputation around the age of walking.
The third is to retain the foreshortened foot/ ankle complex but to rotate the leg through 180 degrees to allow the ankle to act like a knee joint. This Van Ness rotationplasty gives the child a below knee rather than an above kee prosthesis and has energy saving advantages, particularly later in life.

Some have attempted to stabilize the hip in Aitken Classes C and D but with limited success. It is difficult to achieve pelvi-femoral fusion in this situation. I have been involved in another variation in an Atkin class C PFFD. We attempted to maintain knee motion but in reverse by performing a Van Ness rotationplasty proximally ( rather than through the knee or tibia) and simultaneously fusing the femoral remnant to the ilium. The knee now functions as a hip and the ankle as a knee. The excessive soft tissues in the thigh make this a technically difficult procedure in a younger child. The functional outcome is unpredictable.