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.

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The condition represents a spectrum, with Aitken classification describing the severity based on presence of femoral head and acetabulum.

Understanding the anatomy helps determine reconstruction feasibility and treatment planning.

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.

Several parts of this topic assume the deficient hip can be "reconstructed" before lengthening, and the Global Practice table names "SUPERhip-type" strategies - but the operation itself is worth defining, because it is the workhorse that makes reconstruction of a Paley type 1b hip possible.

SUPERhip stands for the Systematic Utilitarian Procedure for Extremity Reconstruction of the hip, developed by Paley in 1997 for congenital femoral deficiency with a mobile hip but a severely deformed proximal femur (Paley type 1b: coxa vara with a very low neck-shaft angle, delayed ossification of the femoral neck/subtrochanteric region, and extra-articular hip contractures). It is a single-stage operation performed before any femoral lengthening, and it systematically addresses every component of the deformity:

• Release of the extra-articular contractures (the flexion-abduction-external-rotation posture) to mobilise the hip
• Subtrochanteric valgus and derotation osteotomy to correct the coxa vara and restore the neck-shaft angle toward normal (the Violante 2024 series improved the mean neck-shaft angle from about 72 to 133 degrees)
• Abductor rebalancing / greater-trochanteric advancement to restore the abductor lever arm and reduce a Trendelenburg gait
• Correction of associated acetabular dysplasia where present, to create a stable, congruent hip

The dominant late problems are recurrent coxa vara and persistent delayed ossification of the femoral neck. Paley's series of 72 type 1b hips required revision in nearly half of the early cases; recurrence fell significantly only when a fixed-angle internal-fixation device was used to hold the correction, combined with BMP-2 placed in the un-ossified neck cartilage to induce ossification (a non-fixed rush-rod repeatedly lost correction). Only once a stable, ossified, well-aligned hip is achieved does staged femoral lengthening proceed - reconstruction of the hip is the foundation, not a substitute, for equalising limb length.

The management options above - reconstruction, rotationplasty and amputation - are all surgical, yet the landmark gait study underpinning this topic (Floccari 2021) included a distinct non-operative group treated with an equinus prosthesis, an option that is easy to forget in the exam.

In a child whose deficiency is milder, or whose family declines surgery, the intact foot is left in place and held in maximal equinus (plantarflexion) inside a custom extension prosthesis. The plantarflexed foot then behaves like a short, end-bearing Syme-level residual limb: it delivers distal weight-bearing and length, while a prosthetic knee mechanism is built into the socket below the foot. No bone is cut and no growth plate is sacrificed, so it is fully reversible and keeps all reconstructive and ablative options open as the child grows.

The trade-offs are honest ones for a viva:

• The prosthesis is bulky and cosmetically longer than the sound side, and the retained foot sits high, so it cannot drive a slim below-knee-style limb
• A fixed equinus foot is prone to skin/pressure problems, and the socket needs frequent revision with growth
• Crucially, it is not functionally inferior: in Floccari's series the equinus-prosthesis group actually walked the fastest (about 97 percent of normal cadence for age) and had PODCI pain, function and happiness scores no different from the rotationplasty and Syme-amputation groups, while undergoing the fewest operations (mean 0.7 procedures)

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):

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.