Proximal Femoral Focal Deficiency

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.

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.

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)

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

The shortened, abnormally positioned thigh of PFFD overlaps with several other causes of a congenitally short femur or limb-length discrepancy. The discriminator is the state of the proximal femur, hip and the rest of the limb.

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

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

Functional Outcomes:

Type A/B (Reconstruction):

• Reproducible radiographic correction of coxa vara/acetabular dysplasia (neck-shaft angle commonly restored toward normal; Violante 2024)
• Usually requires multiple staged procedures (hip reconstruction then lengthening)
• Final residual LLD often managed with limited lengthening plus shoe raise
• Hip stability achievable in most reconstructable hips
• Complication rates higher in children under 5 years

Type C/D (Rotationplasty/Amputation):

• Rotationplasty: durable pain-free outdoor ambulation; high appearance acceptance in selected patients (Kowalczyk 2018)
• Contemporary comparison shows no measurable gait/energy/PRO advantage over amputation (Floccari 2021)
• Both pathways need lifelong prosthetic care with revisions as the child grows
• Shared decision-making and family counselling are central

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

PFFD management is one of the more genuinely contested areas in paediatric limb reconstruction. Examiners reward candidates who can hold the uncertainty rather than reciting dogma.

• Rotationplasty versus amputation. The long-held belief that rotationplasty is functionally superior has been challenged. The JBJS 2021 gait-analysis comparison found no advantage in oxygen cost, gait deviation index or patient-reported outcomes over Syme amputation with a prosthetic knee, despite more operations. The counterpoint is that rotationplasty preserves an active joint with good long-term acceptance (Kowalczyk 2018) and durable, energy-efficient gait at very long follow-up in rotationplasty cohorts overall (Krebbekx 2026). The honest position: individualised, family-centred decision-making.

• Reconstruction/lengthening versus prosthetic management. With modern hip reconstruction and serial lengthening (SUPERhip-type strategies, motorized implants), some severe deficiencies once destined for amputation are now reconstructed. Critics note the burden of multiple operations, complications and uncertain long-term durability. There is no level-1 evidence comparing a full reconstructive pathway against early prosthetic conversion.

• Classification: Aitken versus Paley. Aitken is descriptive and widely known but does not directly guide reconstruction feasibility. The Paley classification is function- and reconstruction-oriented and increasingly used in lengthening centres. Candidates should know both and why the field is shifting.

• Implant choice in the young child. Intramedullary lengthening nails carry a femoral-head AVN risk in skeletally immature children, so external fixation or motorized expandable plates are used instead - but the plate evidence is early (small case series; Georgiadis 2022).

• Terminology. "Fibular hemimelia" is increasingly regarded as inaccurate; some authors prefer "postaxial/fibular longitudinal deficiency" and group PFFD with associated fibular and midline metatarsal deficiencies as a single dysvascular spectrum.

Global Epidemiology:

• PFFD/congenital femoral deficiency is rare, with frequently quoted incidence around 1 in 50,000 to 1 in 200,000 live births
• Mostly sporadic and unilateral; bilateral involvement in roughly 10-15% (more often bilateral when associated with broader limb-deficiency syndromes)
• Strong association with ipsilateral fibular (postaxial) longitudinal deficiency in around half of cases
• Population registry data are scarce: a Finnish national malformation/care registry captured all 185 lower-limb-deficiency live births over 1993-2008, confirming the heavy hospital and surgical burden of long-bone deficiencies relative to the general paediatric population (Syvanen 2018)

Side-by-Side Practice (no single global guideline exists):

Registries & Evidence Gaps:

• No implant-survival registry applies directly to PFFD (it is a reconstruction/prosthetic, not arthroplasty, problem)
• Outcome data come from single-centre series and gait laboratories; there is no level-1 trial comparing reconstruction, rotationplasty and amputation
• Limb Lengthening and Reconstruction Society outcome indices (e.g. the angular-deformity/infection/motion score) are used to standardise lengthening complications

High- vs Limited-Resource Practice Variation:

• High-resource settings: MRI for unossified head, motorized internal lengthening implants, formal gait analysis, multidisciplinary limb-deficiency clinics
• Limited-resource settings: reliance on plain radiographs and clinical prediction, external fixation (lower implant cost but higher pin-site burden), earlier prosthetic conversion where staged reconstruction is impractical; prosthetic availability and follow-up for growth-related revisions are the rate-limiting factors

Multidisciplinary Team (universal): paediatric orthopaedic/limb-reconstruction surgeon, physiotherapist (critical during lengthening), occupational therapist, prosthetist/orthotist, and psychological/social support for child and family. Informed consent must cover the multi-operation, long-term commitment and realistic, evidence-honest expectations.