PROXIMAL FEMORAL FOCAL DEFICIENCY
Congenital Femoral Deficiency | Aitken Classification | Limb Length Discrepancy | Reconstruction vs Rotationplasty
AITKEN CLASSIFICATION
Critical Must-Knows
- Aitken classification determines treatment: Type A/B = reconstruction, Type C/D = rotationplasty/amputation
- Limb length discrepancy is the main problem - predict final LLD using multiplier method or Paley method
- Reconstruction options: Pelvic-femoral stabilization, femoral lengthening, hip reconstruction with osteotomy
- Rotationplasty (Van Nes) converts ankle to knee - preserves proprioception, allows prosthetic fitting
- Associated anomalies: Fibular hemimelia (50%), cruciate ligament deficiency, foot anomalies
Examiner's Pearls
- "Aitken classification is high-yield - know all 4 types and treatment implications
- "Type A/B have femoral head = reconstruction possible. Type C/D lack femoral head = rotationplasty/amputation
- "Rotationplasty preserves proprioception and allows better prosthetic function than amputation
- "Limb length discrepancy prediction is critical - use multiplier method or Paley method
Critical PFFD Exam Points
Aitken Classification Determines Treatment
Type A/B have femoral head = reconstruction possible (pelvic-femoral stabilization, lengthening). Type C/D lack femoral head = rotationplasty or amputation. Classification based on presence of femoral head and acetabulum.
Limb Length Discrepancy is Main Problem
LLD increases with growth - predict final discrepancy using multiplier method or Paley method. Severe cases (over 15cm) may need rotationplasty. Reconstruction aims to minimize LLD while maintaining function.
Rotationplasty Preserves Proprioception
Van Nes rotationplasty converts ankle to knee joint - preserves proprioception, allows better prosthetic fitting than amputation. Indicated for Type C/D or severe LLD (over 15-20cm predicted).
Associated Anomalies Common
50% have fibular hemimelia, cruciate ligament deficiency, foot anomalies. Always assess entire limb. May affect treatment choice (e.g., fibular hemimelia may favor rotationplasty).
PFFD Treatment by Aitken Type - Quick Reference
| Aitken Type | Femoral Head | Acetabulum | Treatment Options |
|---|---|---|---|
| Type A | Present | Present | Reconstruction: pelvic-femoral stabilization, lengthening |
| Type B | Present | Present | Reconstruction: osteotomy + stabilization, lengthening |
| Type C | Absent | Present | Rotationplasty or amputation |
| Type D | Absent | Absent | Rotationplasty or amputation |
FACTSPFFD Associated Anomalies
Memory Hook:FACTS about PFFD: Fibular hemimelia, ACL deficiency, Coxa vara, Tarsal anomalies, and Short femur are all associated findings!
CARSRotationplasty Indications
Memory Hook:CARS drive rotationplasty: C/D type, Ankle function, Residual LLD over 15cm, and Stable knee are key indications!
ROADPFFD Treatment Options
Memory Hook:ROAD to treatment: Reconstruction for A/B, Osteotomy for B, Amputation for C/D, and Distraction for lengthening!
Overview and Epidemiology
Proximal femoral focal deficiency (PFFD) is a rare congenital condition characterized by partial or complete absence of the proximal femur. It represents a spectrum of femoral deficiency ranging from mild shortening with coxa vara to complete absence of the proximal femur and acetabulum.
Epidemiology:
- Incidence: 1 in 50,000 live births
- Male to female ratio: 1:1
- Bilateral involvement: 15% of cases
- Left side more commonly affected than right
- No clear genetic inheritance pattern (sporadic)
Pathophysiology: PFFD results from failure of normal development of the proximal femur during embryogenesis (4-8 weeks gestation). The exact cause is unknown but may involve:
- Vascular insult during development
- Teratogenic exposure
- Genetic factors (rare familial cases reported)
- Failure of mesenchymal condensation
The condition represents a spectrum, with Aitken classification describing the severity based on presence of femoral head and acetabulum.
Pathophysiology and Mechanisms
Normal Development: The proximal femur develops from mesenchymal condensation at 4-6 weeks gestation. The femoral head, neck, and greater trochanter develop from separate ossification centers that fuse during childhood.
PFFD Pathology: In PFFD, there is failure of normal development of the proximal femur, resulting in:
- Shortened or absent proximal femur
- Coxa vara deformity (Type A)
- Pseudarthrosis at neck (Type B)
- Absent femoral head (Type C/D)
- Dysplastic or absent acetabulum (Type D)
- Associated soft tissue deficiencies (muscles, ligaments)
Associated Musculoskeletal Findings:
- Fibular hemimelia (50% of cases)
- Cruciate ligament deficiency (common)
- Foot anomalies (tarsal coalition, equinovarus)
- Patellar anomalies
- Tibial shortening (less common than fibular)
Understanding the anatomy helps determine reconstruction feasibility and treatment planning.
Classification Systems
Aitken Classification (1969)
The Aitken classification is the most widely used system, based on radiographic appearance of the femoral head and acetabulum:
Aitken Classification Summary
| Type | Femoral Head | Femoral Neck | Acetabulum | Treatment |
|---|---|---|---|---|
| Type A | Present | Short, coxa vara | Normal | Reconstruction |
| Type B | Present | Absent, pseudarthrosis | Normal | Reconstruction with osteotomy |
| Type C | Absent | Absent | Present but dysplastic | Rotationplasty/amputation |
| Type D | Absent | Absent | Absent | Rotationplasty/amputation |
Type A: Best prognosis. Femoral head present but delayed ossification. Short neck with coxa vara. Acetabulum normal. Reconstruction possible with pelvic-femoral stabilization and lengthening.
Type B: Femoral head present but no neck continuity (pseudarthrosis). Acetabulum present. Reconstruction requires osteotomy to establish continuity, then lengthening.
Type C: No femoral head. Acetabulum present but dysplastic. Reconstruction not feasible. Rotationplasty or amputation indicated.
Type D: Most severe. No femoral head, no acetabulum. Rotationplasty or amputation only options.
The classification determines treatment options and prognosis.
Clinical Assessment
History:
- Shortened lower limb noted at birth or early infancy
- Delayed walking (if unilateral, may walk with limp)
- Difficulty with activities requiring equal leg length
- Family history (rare but may be present)
Physical Examination:
Inspection:
- Shortened thigh (proximal deficiency)
- Flexed, abducted, externally rotated hip (pseudarthrosis position)
- Knee may be flexed (compensation)
- Foot position (assess for associated anomalies)
- Compare to contralateral side
Palpation:
- Proximal femur may be absent or very short
- Greater trochanter may be palpable (Type A/B) or absent (Type C/D)
- Assess hip stability
- Knee stability (cruciate deficiency common)
Range of Motion:
- Hip: Limited flexion, abduction
- Knee: May have hyperextension or flexion contracture
- Ankle: Assess for equinus or other deformities
Limb Length Measurement:
- True leg length: ASIS to medial malleolus
- Apparent leg length: umbilicus to medial malleolus
- Thigh length: greater trochanter to lateral joint line
- Predict final LLD using multiplier method or Paley method
Neurovascular:
- Usually normal
- Assess femoral nerve function (may be affected in severe cases)
Investigations
Radiographs:
AP Pelvis and Hip:
- Assess presence of femoral head (may be delayed ossification in Type A)
- Evaluate acetabulum (present, dysplastic, or absent)
- Measure coxa vara angle (Type A)
- Identify pseudarthrosis (Type B)
Full-Length Standing Radiographs:
- Measure limb length discrepancy
- Assess alignment
- Evaluate for associated anomalies (fibular hemimelia, tibial shortening)
MRI (if indicated):
- Assess unossified femoral head (Type A - may appear absent on X-ray but present on MRI)
- Evaluate acetabular cartilage
- Assess soft tissue structures (muscles, ligaments)
Ultrasound (infants):
- May identify unossified femoral head
- Assess hip stability
Limb Length Prediction:
- Multiplier method: Current LLD × multiplier for age/sex = predicted final LLD
- Paley method: More complex, accounts for growth remaining
Genetic Evaluation:
- Usually not indicated (sporadic)
- Consider if bilateral or family history present
Management Algorithm
Treatment Philosophy
Treatment goals:
- Maximize function and independence
- Minimize limb length discrepancy
- Maintain hip stability
- Optimize prosthetic fitting (if needed)
Treatment options:
- Reconstruction: Pelvic-femoral stabilization, lengthening (Type A/B)
- Rotationplasty: Van Nes procedure (Type C/D or severe LLD)
- Amputation: Knee disarticulation or above-knee (Type C/D, failed reconstruction)
- Prosthetic fitting: For any option with significant LLD
Choice depends on Aitken type, predicted LLD, associated anomalies, and family preference.
Surgical Techniques
Pelvic-Femoral Stabilization
Indication: Type A/B with unstable hip or need for reconstruction.
Technique:
- Approach: Anterior iliofemoral or extended Smith-Peterson
- Exposure: Proximal femur and acetabulum
- Preparation:
- Acetabulum: Ream to create socket if needed
- Femur: Prepare proximal end
- Stabilization:
- Create continuity between femur and pelvis
- May use bone graft
- Internal fixation (plates, screws)
- Position: Hip in functional position (flexion, slight abduction)
Postoperative: Spica cast 6-12 weeks, then protected weight-bearing.
Complications
Reconstruction Complications:
Early:
- Infection (5-10%)
- Wound healing problems
- Neurovascular injury (rare but devastating)
- Fixation failure
Late:
- Hip instability (recurrent subluxation/dislocation)
- Stiffness (hip, knee)
- Contractures (flexion, abduction)
- Limb length discrepancy recurrence (growth asymmetry)
- Delayed union/nonunion (osteotomy sites)
- Hardware problems (loosening, breakage)
Lengthening Complications:
- Pin site infection (common, usually minor)
- Stiffness (knee most common)
- Contractures (flexion, equinus)
- Delayed union (prolonged consolidation)
- Premature consolidation (stops lengthening)
- Nerve injury (peroneal most common)
- Vascular compromise (rare)
- Refracture after fixator removal
Rotationplasty Complications:
- Wound healing problems
- Neurovascular injury
- Malrotation (incorrect rotation angle)
- Nonunion
- Prosthetic fitting problems
Prevention:
- Careful preoperative planning
- Appropriate patient selection
- Meticulous surgical technique
- Aggressive physical therapy
- Close monitoring during lengthening
Postoperative Care
Immediate Postoperative:
- Pain management
- Neurovascular monitoring
- Wound care
- Immobilization (cast, splint, external fixator)
Reconstruction:
- Spica cast 6-12 weeks
- Protected weight-bearing 3-6 months
- Physical therapy for range of motion
- Gradual return to activities
Lengthening:
- Pin site care (daily cleaning)
- Distraction protocol (1mm/day)
- Physical therapy (critical for preventing stiffness)
- Regular radiographs (weekly during distraction, monthly during consolidation)
- Monitor for complications
Rotationplasty:
- Cast 6-8 weeks
- Wound monitoring
- Prosthetic fitting after healing
- Gait training
Long-term Follow-up:
- Annual assessment until skeletal maturity
- Monitor LLD progression
- Assess function and quality of life
- Address complications as they arise
Outcomes and Prognosis
Functional Outcomes:
Type A/B (Reconstruction):
- Good to excellent function in 60-70%
- May require multiple procedures
- Final LLD typically 2-5cm (manageable with shoe lift)
- Hip stability achieved in most cases
- Patient satisfaction generally good
Type C/D (Rotationplasty/Amputation):
- Rotationplasty: Better function than amputation
- Proprioception preserved
- Good prosthetic function
- Patient satisfaction variable (cosmetic concerns)
Quality of Life:
- Most patients adapt well
- Sports participation possible (with modifications)
- Vocational outcomes generally good
- Psychosocial support important
Predictors of Poor Outcome:
- Severe associated anomalies (fibular hemimelia, foot problems)
- Bilateral involvement
- Multiple complications
- Poor compliance with rehabilitation
Long-term:
- Most patients function independently
- May develop hip or knee arthritis (reconstruction)
- Prosthetic needs may change with growth
Evidence Base
Aitken Classification and Treatment Outcomes
- Original description of Aitken classification (Types A-D)
- Type A/B have better outcomes with reconstruction
- Type C/D require rotationplasty or amputation
- Classification remains gold standard for treatment planning
Rotationplasty vs Amputation in PFFD
- Rotationplasty preserves proprioception
- Better prosthetic function than amputation
- Patient satisfaction higher with rotationplasty
- Cosmetic concerns may affect acceptance
Femoral Lengthening in Congenital Deficiencies
- Multiple lengthenings may be needed for severe LLD
- Complication rate increases with amount of lengthening
- Knee stiffness is most common complication
- Careful patient selection critical for success
Limb Length Prediction in PFFD
- Multiplier method accurate for LLD prediction
- Paley method accounts for growth remaining
- Prediction critical for treatment planning
- Severe LLD (over 15cm) favors rotationplasty
Outcomes of PFFD Reconstruction
- Type A/B reconstruction: 60-70% good outcomes
- Multiple procedures often required
- Final LLD typically 2-5cm (manageable)
- Hip stability achieved in most cases
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Initial Assessment
"A 2-year-old child presents with a shortened right lower limb noted since birth. Parents report the child walks with a limp. On examination, the right thigh is significantly shorter than the left, and the hip is held in flexion and abduction. Radiographs show a short proximal femur with coxa vara, but the femoral head is present. How would you assess and manage this child?"
Scenario 2: Type C PFFD Management
"A 5-year-old child with known PFFD presents for treatment planning. Radiographs show absence of the femoral head with a dysplastic but present acetabulum (Aitken Type C). The predicted limb length discrepancy at maturity is 18cm. The ankle is functional. What are the treatment options and how would you counsel the family?"
Scenario 3: Lengthening Complications
"A 10-year-old child with Type A PFFD underwent femoral lengthening with an external fixator. During the distraction phase, the parents report the child has developed increasing knee stiffness and is unable to fully extend the knee. On examination, there is a 30-degree flexion contracture. The distraction is at 4cm of the planned 6cm. How would you manage this?"
MCQ Practice Points
Aitken Classification Question
Q: Which Aitken type of PFFD has a femoral head present but no femoral neck continuity (pseudarthrosis)? A: Type B - Type B has a femoral head present with a pseudarthrosis at the neck level. Type A has a short neck with coxa vara. Type C and D lack the femoral head entirely.
Treatment Indication Question
Q: What is the main indication for rotationplasty in PFFD? A: Aitken Type C or D (no femoral head) or severe predicted limb length discrepancy (over 15-20cm). Rotationplasty converts the ankle to a knee joint, preserving proprioception and allowing better prosthetic function than amputation.
Associated Anomaly Question
Q: What is the most common associated anomaly in PFFD? A: Fibular hemimelia - present in 50% of PFFD cases. Other associated findings include cruciate ligament deficiency, foot anomalies, and patellar anomalies.
Lengthening Complication Question
Q: What is the most common complication during femoral lengthening for PFFD? A: Knee stiffness and flexion contracture - this is the most common complication and requires aggressive physical therapy from the start of lengthening. Other complications include pin site infection, delayed union, and nerve injury.
Reconstruction Feasibility Question
Q: Which Aitken types are candidates for reconstruction rather than rotationplasty or amputation? A: Type A and Type B - both have a femoral head present, making reconstruction feasible. Type A requires pelvic-femoral stabilization and lengthening. Type B requires osteotomy to establish neck continuity, then stabilization and lengthening. Type C and D lack the femoral head and require rotationplasty or amputation.
Australian Context and Medicolegal Considerations
Healthcare System:
- PFFD management typically involves pediatric orthopedic centers
- Public hospital system provides comprehensive care
- Private options available for some procedures
- Prosthetic services available through public and private providers
Multidisciplinary Care:
- Pediatric orthopedic surgeon (primary)
- Physiotherapist (critical for lengthening and rehabilitation)
- Occupational therapist (prosthetic training, activities of daily living)
- Prosthetist (for rotationplasty and amputation cases)
- Psychologist (support for child and family)
- Social worker (financial and social support)
Medicolegal Considerations:
- Informed consent critical - multiple procedures, long-term commitment
- Realistic expectations about outcomes and complications
- Documentation of predicted LLD and treatment rationale
- Family counseling about cosmetic appearance (rotationplasty)
- Long-term follow-up until skeletal maturity
Prosthetic Services:
- Available through public and private providers
- Regular adjustments needed as child grows
- Functional prostheses for activities and sports
- Cosmetic prostheses for social situations (some patients)
Research and Outcomes:
- Australian centers contribute to international research
- Registry data helps track long-term outcomes
- Quality of life studies important for treatment decisions
PROXIMAL FEMORAL FOCAL DEFICIENCY
High-Yield Exam Summary
Key Facts
- •Incidence: 1 in 50,000 live births
- •Aitken classification: Type A-D based on femoral head and acetabulum
- •50% have associated fibular hemimelia
- •Limb length discrepancy is main problem
Aitken Classification
- •Type A: Femoral head present, short neck, coxa vara = Reconstruction
- •Type B: Femoral head present, no neck, pseudarthrosis = Reconstruction with osteotomy
- •Type C: No femoral head, acetabulum present = Rotationplasty/amputation
- •Type D: No femoral head, no acetabulum = Rotationplasty/amputation
Treatment Algorithm
- •Type A/B: Reconstruction (pelvic-femoral stabilization, lengthening)
- •Type C/D: Rotationplasty or amputation
- •Severe LLD (over 15cm): Consider rotationplasty even in Type A/B
- •Predict final LLD using multiplier or Paley method
Surgical Pearls
- •Rotationplasty preserves proprioception - better than amputation
- •Femoral lengthening: 1mm/day distraction, aggressive PT critical
- •Knee stiffness is most common lengthening complication
- •Multiple lengthenings may be needed for severe LLD
Complications
- •Lengthening: Knee stiffness (most common), pin site infection, delayed union
- •Reconstruction: Hip instability, contractures, hardware problems
- •Rotationplasty: Wound healing, malrotation, prosthetic fitting issues
- •Prevention: Aggressive PT, careful patient selection, close monitoring