Proximal femoral focal deficiency is a congenital disorder where the proximal femur is partially absent, and the entire limb is shortened. It is a rare disorder and affects 1-4 person per 50,000. It is also known as the congenital femoral deficiency.
Image Credit: Orthobullets
Cause and Pathophysiology
The exact cause of proximal femoral deficiency is not known but the injury to the neural crest cells that form the precursors to the peripheral sensory nerves of L4 and L5 results in PFFD has been suggested as a factor.
A defect in proliferation and maturation of chondrocytes in the proximal growth plate has also been suggested. A drug like thalidomide, when taken between the fourth and sixth weeks of gestation, has been shown to cause of the proximal femoral focal deficiency.
Patients with proximal femoral focal deficiency also have limb-length inequalities, malrotation, joint instability, and deficient proximal musculature.
Vessels and ligaments are also known to be hypoplastic.
The spectrum of disease includes
- absent hip
- femoral neck pseudoarthrosis
- absent femur
- shortened femur
Proximal femoral focal deficiency is bilateral in about 15% cases.
A rare autosomal dominant form associated with sonic hedge-hog gene but the condition mostly is sporadic.
Associated conditions
- Fibular hemimelia (50%)
- ACL deficiency
- Coxa Vara
- Knee contractures
- Dysmorphic facies in rare autosomal dominant type
- Cleft palate
- Clubfoot
- Congenital heart defects
- Spinal anomalies
Clinical Presentation
There is a severe shortening of one or both legs. The proportion of the shortening remains constant with growth. The thigh appears short and bulky [bulbous] which tapers into the knee. The limb is flexed, abducted, and externally rotated.
Feet are usually normal.
The knee is unstable on examination due to absent cruciate ligaments. The hypoplastic knee has been reported.
Classification of Proximal Femoral Focal Deficiency
Aitken classification
Class A
- Shortened proximal, ending at or slightly above the level of the acetabulum
- The femoral head is often absent but later ossifies; femoral head presence is indicated by a well-developed acetabulum
- A subtrochanteric defect is present, which eventually ossifies and thereby establishes bony continuity but leaves a residual subtrochanteric varus deformity
Class B
- More severe defect or absence of the proximal femur that does not heal spontaneously
- End of the proximal femur is above the acetabulum
- The femoral head is present but may have delayed ossification is mildly dysplastic
- A bony tuft on the proximal end of the shaft is present
Class C
- Absent femoral head that does not ossify
- Severley dysplastic acetabulum
- Femoral shaft is shorter than in a person with class B
Class D
- Most severe form
- Severely shortened shaft
- Often has only an irregularly ossified tuft of bone proximal to the distal femoral epiphysis
- Acetabulum is absent
Gillespie’s functional classification
Group A
- Possible candidates for limb-lengthening
- Congenitally short femurs but clinically stable hips
- No significant knee flexion contractures
- Ipsilateral foot at or below the level of the middle of the contralateral tibia
Group B
- Aitken as classes A, B, and C who require prosthetic treatment.
- Surgical procedure is designed to maximize prosthetic function
Group C
- Aitken class D. These patients do not require knee fusions before prosthetic fitting
Imaging
X-ray is the basic investigation and Aitken classification is based on radiographic appearance.
It is held that radiographic evaluation tends to overestimate the degree of deficiency and that MRI is the better modality.
Treatment of Proximal Femoral Focal Deficiency
Treatment of proximal femoral focal deficiency must be individualized from patient to patient.
The following factors help in devising the treatment plan
- Ultimate leg length discrepancy at skeletal maturity
- Presence and severity of foot deformities
- Adequacy of the musculature of lower limbs
- Joint instability of proximal joints
Most of the patients with unilateral deficiency require surgical treatment. Observation is indicated often in children with a bilateral deficiency
Some selected patients with unilateral disease may be offered prosthesis but prosthesis acceptance is less because of cumbersomeness and large size of prosthesis.
Surgical treatment
Goal – Ambulation without prosthesis
Procedure – limb lengthening with or without contralateral epiphysiodesis
This option is indicated if there is
- Predicted limb length discrepancy of <20 cm at maturity
- stable hip and functional foot
- Affected femur has femoral length >50% of opposite side
- Femoral head present (Aiken classifications A & B)
The procedure is contraindicated in uncorrected coxa vara, proximal femoral neck pseudoarthrosis, or acetabular dysplasia
Goal – Ambulation with a prosthesis
Knee Arthrodesis with Foot Amputation
This procedure is done in cases where the ipsilateral foot is proximal to the level of the contralateral knee so that prosthetic knee will not be below the level of the contralateral knee at maturity
Femoral Pelvic Fusion
It is also called Brown’s procedure and is indicated in patients in whom femoral head is absent (Aitken classifications C & D)
Van Ness rotationplasty
This procedure is done in cases where the ipsilateral foot is at the level of opposite knee and ankle as more than two-thirds of its motion and the femoral head is absent [Aitken classifications C & D]
The procedure involves rotating the limb through femur through 180 degrees, so that ankle which is in the position of knee serves the function of the knee. The ankle dorsiflexion becomes knee flexion.
This allows the use of below-knee prosthesis to improve gait and efficiency
Amputation
Limb amputation is indicated when femoral length <50% of opposite side. As much as possible length should be preserved.
