Classification of Amstutz for Congenital Proximal Femoral Focal Deficiency (PFFD)

Description

Amstutz developed a classification scheme for patients with congenital proximal femoral focal deficiency (PFFD). This can help predict the clinical course and determine the optimum type and timing for intervention.

Parameters:

(1) appearance of the femur

(2) ossification in the femur and capital femoral epiphysis

(3) acetabulum and pelvis

(4) deformity

NOTE: Since the scheme defines deficiencies in the proximal femur, some part of the femur is present, which distinguishes it from congenital absence of the femur.

Parameter	Type I	Type II	Type III
appearance of the femur	short with considerable bowing; sclerosis of the medial femoral cortex; often a laterally positioned beak	subtrochanteric pseudoarthrosis with persisting defect	early X-rays show proximal bulbous ossification to femoral shaft
ossification of proximal femur and capital femoral epiphysis	ossification of the capital femoral epiphysis may be delayed; lesser trochanter may fail to ossify	delayed and irregular; ossification of capital femoral epiphysis shows marked delay	ossification of capital femoral epiphysis markedly delayed; see subtypes below
acetabulum and pelvis	present; femoral head is well centered	present	present
deformity	stable with nonprogressive coxa varus	progressive varus	varus may or may not progress

Subtypes for Type I:

(1) Type 1B: progressive hip dysplasia with early onset arthritis

(2) Type 1A: absence of progressive hip dysplasia

Subtypes of Type III:

(1) Type 3A: complete ossification without varus deformity

(2) Type 3B: delayed ossification with varus progression

(3) Type 3C: spotty ossification with wide neck defect

(4) Type 3D: absent ossification with wide cervical pseudoarthrosis

	Type IV	Type V
femur	early X-rays show proximal end of femoral shaft tapers sharply to a point; capital femoral epiphysis present but appears separate; persisting pseudoarthrosis	distal parts only
ossification of proximal femur and capital femoral epiphysis	delayed ossification of the capital femoral epiphysis	delayed ossification of bony parts present; capital femoral epiphysis absent
acetabulum and pelvis	present but dysplastic	acetabulum absent; pelvis abnormal
deformity	contractures with proximal migration of distal elements	unstable hip; positive Trendelenberg; severe stunting

where:

• "capital" refers to the head of the femur

• The hallmarks of the Type V include an iliac projection just above the usual acetabular anatomical site and a spherical obturator foramen. If bilateral the pelvis is square or box-like.

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Description

Specialty

ICD-10