AUTHOR AND EDITOR INFORMATION

Section 1 of 8  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• References

INTRODUCTION

Section 2 of 8  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• References

Proximal femoral focal deficiency (PFFD) is an uncommon but complex problem. PFFD was commonly grouped with other disorders, such as coxa vara and short bowed femurs, which led to confusion and misunderstanding.¹

Problem

In general, in individuals with PFFD, the proximal femur is partially absent, and the entire limb is overall shortened. A few main biomechanical abnormalities are present in children with PFFD, as well as in adults with limb deficiencies. These include limb length discrepancies, malrotation, proximal joint instability, and inadequacy of the proximal musculature.


See also the following related topic in Medscape:
Clinical Quiz - Limb Discrepancies at Birth

Frequency

The incidence of the deficiency ranges from 1 case per 50,000 population to 1 case per 200,000 population.²

Etiology

The etiology of PFFD is not known exactly, but certain theories have been proposed and agents implicated. Sclerotome subtraction is one such theory that has been offered to explain several different limb deficiencies. Specifically, this theory states that injury to the neural crest cells that form the precursors to the peripheral sensory nerves of L4 and L5 results in PFFD.³

A second theory, advanced by Boden et al, states that PFFD may be the result of a defect in proliferation and maturation of chondrocytes in the proximal growth plate.⁴ Agents implicated in causing such injuries include anoxia, ischemia, irradiation, bacterial and viral infections and toxins, hormones, mechanical energy, and thermal injury.^{3, 5} Thalidomide, when taken by the mother between the fourth and sixth weeks of gestation, has been demonstrated to be a definite cause of PFFD in humans.⁵ Currently, no evidence indicates a genetic etiology.^{2, 6}

Clinical

The appearance of PFFD is not subtle, so it is easily recognized. The femur is shortened, flexed, abducted, and externally rotated.^{3, 5, 7} Gillespie noted that, in his patients, the hips were never normal and the knees were dysfunctional.^{1, 8} Flexion contractures of the hip and knee are also present. The bulbous proximal thigh quickly tapers to the knee. Because of the short femur and bulbous thigh, examination of the hip can be difficult. As a result of hip instability, pistoning may be present. The knee is uniformly unstable in an anteroposterior plane secondary to absent cruciate ligaments. Additionally, generalized knee hypoplasia has been reported.¹

A high incidence of fibular deficiency and valgus feet is associated with PFFD.⁵ Fibular deficiencies are found in as many as 70-80% of persons with PFFD. Approximately 50% of patients with PFFD have other limb anomalies.⁹  However, Aitken reported almost a 70% incidence of other anomalies.¹⁰ Cleft palate, clubfoot, congenital heart defects, and spinal anomalies, although rare, occur as well. PFFD is bilateral in 15% of the cases.⁶

Classification

Several classification systems describe congenital anomalies of the femur, but most have been based on radiographic appearances alone. The Amstutz and Pappas classifications provide detailed radiologic descriptions of the various forms of PFFD that these researchers encountered.^{11, 12} Hamanishi described a progressive reduction of the femur, ranging from simple shortening to total absence.¹³ Fixsen and Lloyd-Roberts divided their patients into stable and unstable categories.¹⁴

Gillespie and Torode reviewed their patients from both a radiographic and, more importantly, a clinical viewpoint and found that most could be divided into 2 groups. The first group included persons with congenital short femurs, and the second group was composed of individuals with true PFFD. These 2 groups not only differed with respect to clinical and radiographic appearances but also were functionally unique and had different surgical and prosthetic requirements.¹

The Aitken classification, which is the most widely used classification, divides PFFD into 4 categories based on the radiographic appearance.¹⁰ Remember that late ossification may occur, whereby the bone may be present but not visualized radiographically. Occasionally, push-pull comparison radiographs, as well as abduction-adduction views, are necessary to distinguish between class A and class B. Arthrography also can be helpful.^{3, 5}

In individuals with Aitken class A, a shortened femur is present proximally, 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. Additionally, there is a subtrochanteric defect, which eventually ossifies and thereby establishes bony continuity. After ossification, there is usually a residual subtrochanteric varus deformity.

Persons with class B have a more severe defect or absence of the proximal femur. This defect does not heal spontaneously. At skeletal maturity, there is no connection between the femoral head and proximal femur; the end of the proximal femur is above the acetabulum. The femoral head, although present, may have delayed ossification, and there is often a bony tuft on the proximal end of the shaft.

An individual with Aitken class C has an absent femoral head that does not ossify and a markedly dysplastic acetabulum. The class C femoral shaft is shorter than in a person with class B, in whom the entire proximal femur, including the trochanters, does not develop.

In a person with class D, the most severe form, there is a severely shortened shaft, which often has only an irregularly ossified tuft of bone proximal to the distal femoral epiphysis. No acetabulum is present because the lateral pelvic wall is flat.

In a symposium, Gillespie proposed a more functional classification system in which he divided his patients into 3 treatment groups from a surgical and prosthetic viewpoint.⁸ His first patient set, group A, consisted of possible candidates for limb lengthening. This group included individuals who had congenitally short femurs but clinically stable hips, had no significant knee flexion contractures, and had the ipsilateral foot at or below the level of the middle of the contralateral tibia. Gillespie's group B consisted of patients classified by Aitken as classes A, B, and C and who required prosthetic treatment. Therefore, any surgical procedure is designed to maximize prosthetic function. Gillespie's group C represented the same patients as Aitken's class D in that they had subtotal absence of the femur. Gillespie also recommended prosthetic treatment for his group C patients; however, these patients did not require knee fusions prior to prosthetic fitting.

A study of the efficacy of MRI in classifying PFFD also compared MRI findings to radiographic classification. The study, which used the Amstutz classification system, found that radiographic evaluation tends to overestimate the degree of deficiency and that, therefore, MRI is the better modality.¹⁵

INDICATIONS

Section 3 of 8  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• References

Indications for lengthening include a limb with a predicted discrepancy at maturity not exceeding 20 cm, a hip that is or can be made stable, and a relatively good knee, ankle, and foot. For other indications related to specific procedures, see Surgical therapy.

RELEVANT ANATOMY

Section 4 of 8  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• References

In PFFD, the proximal femur is partially absent, and the entire limb is overall shortened.

CONTRAINDICATIONS

Section 5 of 8  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• References

If the predicted discrepancy is greater than 20 cm, or if for any other reason the child is not suitable for limb lengthening, prostheses should be considered. For contraindications to specific surgical procedures, see Surgical therapy.

WORKUP

Section 6 of 8  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• References

Imaging Studies

• The Aitken classification, which is the most widely used classification, classifies PFFD into 4 categories based on the radiographic appearance.¹⁰ Remember that late ossification may occur, whereby the bone may be present but not visualized radiographically. Occasionally, push-pull comparison radiographs, as well as abduction-adduction views, are necessary to distinguish between class A and class B. Arthrography also can be helpful.^{3, 5, 15, 16}

TREATMENT

Section 7 of 8  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• References

Medical therapy

The management of PFFD requires a multidisciplinary team, which includes the pediatric orthopedic surgeon, prosthetists, and physical therapists. The goals of treatment of PFFD are to compensate for the functional deficits. No single treatment approach applies to all cases. Each person with PFFD must be assessed individually. Cosmesis is much less of an issue.

Several functional deficits need to be understood and addressed. First, the shortened limb is the most apparent functional deficit. Less obvious is the difficulty with hip function and stability. Because of the flexed and externally rotated position of the femur, the knee remains flexed, and the leg and foot are anterior to the body axis. A generalized deficiency of the hip musculature is present, even in patients with stable hips. This results in a significant lurch to shift the center of gravity in the single-leg stance.⁵ The knee often has varying degrees of instability. Foot function generally depends on the severity of any associated leg deficiency, such as fibular hemimelia.

Multiple options and variations exist in the treatment of PFFD, probably more than in any other congenital limb deficiency. Most of the treatments should be delayed until the child is older than 3 years because it is difficult to determine the best option before this age. However, around this age, several important decisions need to be made. The first is whether limb lengthening is appropriate for the child. Indications for lengthening include a limb with a predicted discrepancy at maturity not exceeding 20 cm, a hip that is or can be made stable, and a relatively good knee, ankle, and foot. In such an individual, multiple staged lengthenings can be planned that generally do not begin prior to the child's third birthday and optimally are completed by high school age. The timing and staging of these procedures depends on physician choice. Griffith et al studied 11 children (12 limbs) who underwent limb lengthenings of the same bone twice. ¹⁷

If the predicted discrepancy is greater than 20 cm, or if for any reason the child's condition is not suitable for lengthening, a decision must be made about the best approach to fitting a prosthetic device. The patient with PFFD always requires a prosthesis for ambulation; therefore, any procedure that is attempted must be with the intent of improving function or fit of a prosthesis.¹

Another consideration is the type of prosthesis a patient will wear. Most procedures result in the use of an above-knee prosthesis with a mechanical knee. For example, the combination of a Syme amputation, knee fusion, and possibly an epiphysiodesis at the knee results in an above-knee stump. Rotationplasty procedures (see Van Nes rotationplasty) allow the use of a below-knee prosthesis with a biologic knee.^{3, 18, 19}

The initial treatment of the child with unilateral PFFD should parallel normal development. This same principle applies to other congenital deficiencies as well. Therefore, regardless of planned future treatments, when the child is ready to stand, the child is fitted with a prosthesis to equalize leg lengths and allow for standing and walking.³ This prosthesis, often termed a nonconventional or extension prosthesis, is designed to fit the limb without any surgical correction.⁵ The femoral deformity (short, flexed, abducted, and externally rotated) is accommodated in the hip's funnel proximal socket. Knee joints are often absent in these initial prostheses because the length of the limb is often too long to fit a prosthetic foot that also has a knee joint. However, if sufficient room exists for both, it is preferable. This allows the young child to have knee flexion during all developmental phases, so the child can one-half kneel, squat, pull to stand, and climb on toys and furniture.

The nonconventional prosthesis is effective in permitting ambulation for the young child.^{6, 20} However, as the child grows, this prosthesis poses limitations. Specifically, the continued flexion, abduction, and external rotation of the femoral segment, the anterior limb alignment, the unstable hip, and the flexed knee create a poor lever arm with which to move the prosthesis. Additionally, the foot often lies at the level of the mid calf of the contralateral leg, making placement of the knee joint less than optimal. Therefore, surgical correction of these problems is designed to make the limb a more efficient lever arm to move the prosthesis. The surgical options include knee arthrodeses, foot amputation, limb rotationplasty, hip reconstruction, limb lengthening, and iliofemoral arthrodesis (see Surgical therapy).

The treatment of children with bilateral PFFD is different from the treatment of children with unilateral disease.¹ Some have argued against operative treatment because most of these defects are Aitken class D defects, so these children walk on their natural feet.¹⁰ The main difficulties with these children are limb-length discrepancies and foot deformities. Surgical releases and orthotic use generally can provide for a useful foot. Therefore, in persons with bilateral disease, the feet should be preserved.^{5, 10} Because these children will walk without the use of prostheses for most of their lives, knee fusions are not indicated. Additionally, Van Nes osteotomies (see Van Nes rotationplasty) should not be performed in patients with bilateral disease.^{21, 22, 23}

When present, significant limb length inequalities pose a difficult dilemma. This is because of the problem of shortening the child more versus the difficulty of lengthening these limbs. Interestingly, in one study of 91 patients with PFFD, 29 had bilateral involvement, and of these, males were affected nearly twice as often as females.⁶

Surgical therapy

Knee arthrodesis

Knee arthrodesis is performed commonly in children with PFFD. It allows for a longer and more efficient lever arm, as well as a limb that is more easily contained within the prosthesis.¹ The knee should be fused in neutral or slight extension.²⁰ An additional advantage of knee fusions is that the muscles can act more efficiently across the hip joint.⁵ Generally, within 6 months of knee fusion and prosthetic fitting, the flexion and abduction deformity at the hip joint will correct, thereby aligning the extremity under the body axis.^{1, 3} Depending on the femoral length, as well as that of the entire extremity, it is often beneficial to excise one or both of the physes about the knee at the time of fusion. These fusions are performed commonly in children aged 2-3 years.

In their series, Gillespie and Torode noted that most of their patients benefited from knee fusions.¹ The exceptions were those individuals who already had congenital knee fusions and those persons who had extremely short femoral segments (ie, the knee joints were so close to the pelvis that instability and flexion contractures were of little consequence). Traction injuries of the sciatic nerve have been reported after knee fusion due to sudden knee extension.¹

Foot amputation

Amputation, which often is best performed at the time of knee fusion, acts to shorten the newly created lever arm. This is often desirable because the new lever arm, which is composed of the fused femur and tibia, needs to be shortened to accommodate a mechanical knee when the child is older. Additionally, with growth, the foot becomes more difficult to accommodate in a cosmetically acceptable prosthesis.¹ The Syme amputation has been widely performed and provides a superior end-bearing stump for immediate prosthetic fitting.⁵ The Boyd amputation, which saves the entire calcaneus, is another option. The calcaneus is fused to the distal tibia, thereby creating a bulbous heel pad that facilitates prosthetic suspension. When only a portion of the calcaneus is retained and fused to the distal tibia, the heel pad remains centered, resisting the tendency for migration.³

Van Nes rotationplasty

In 1930, Borggreve initially described the Van Nes tibial rotationplasty, and Van Nes later popularized the procedure.^{24, 25} In the rotationplasty, the limb is rotated 180º; this is accomplished through the knee arthrodesis, the tibia, or both. The ultimate goal at maturity is to have the ankle of the short limb at the level of the contralateral knee, with the foot now acting like the residual tibia in a below-knee amputation. Active control of the prosthetic knee is the most obvious advantage of rotationplasty. The function obtained after a Van Nes procedure is significantly greater than that of an above-knee prosthesis after knee fusion and Syme amputation.²¹ Furthermore, the metabolic energy expenditure and oxygen consumption are lower than they are in patients who have undergone Syme amputation combined with knee arthrodesis.^{21, 26}

Reasonable preoperative ankle and foot function are required for the ankle to serve as a knee.^{22, 23} This is not always the case, because up to 70% of children with PFFD have an ipsilateral fibular deficiency.¹⁰ Some valgus alignment of the foot and ankle can be accommodated in the prosthesis. However, severe valgus and equinus deformities with a deficient foot are a contraindication to the rotationplasty. Preoperative toe and ankle strengthening is helpful because these structures power the new knee joint. Equinus position places the foot in a position of mechanical advantage and is, therefore, emphasized. Although hip instability and coxa vara are not contraindications to the Van Nes procedure, a stable hip allows for a more cosmetically acceptable prosthetic gait that is also less fatiguing.²³

The 2 problems encountered with the Van Nes rotationplasty are failure to achieve sufficient rotation at surgery or subsequent derotation with continued growth.²² For this reason, some clinicians have advocated waiting until the child is aged 12 years before performing this procedure.²³. The incidence of derotation can be decreased if a sufficient amount of bone is removed at the time of rotationplasty.¹ An additional disadvantage is the unattractive appearance of a leg in which the foot has been reversed. In an attempt to improve the appearance, the toes often are removed; however, this removal often leads to a loss in sense of position as well as a loss in power. In contrast, there are reports of good patient acceptance with acceptable cosmesis by patients, parents, prosthetists, and surgeons.^{21, 22, 23} Remember that a Syme amputation serves as the salvage procedure for a failed Van Nes procedure.

Hip stabilization

Some controversy exists about the value of surgical procedures to stabilize the hip. Deficiencies in both the osseous anatomy, as well as the hip musculature, result in hip instability in most patients with PFFD. Aitken class A and B deficiencies have a femoral head within the acetabulum; therefore, some clinicians support surgical correction of the varus deformity and pseudoarthrosis. The bony stability of the femoral-pelvic articulation requires consideration. In those patients in whom lengthening is planned, achievement of good femoral head containment is necessary; this often requires acetabular procedures. In patients with class C or class D involvement, attempts at reconstruction are futile.³

Iliofemoral arthrodesis

Two different kinds of arthrodesis have been described in an attempt to address the hip instability. The fusion is performed to establish a stable union between the femur and pelvis, thereby eliminating pistoning. Additionally, prosthetic fitting is simplified and the gait is steadier. It is indicated in persons in whom a femoral deficiency with an unstable acetabulum is present, as in Aitken class C and class D deficiencies.

Steel described fusing the distal femoral segment to the pelvis; the femur is flexed 90º, making it perpendicular to the body axis and parallel to the floor. As a result, when these patients extend their anatomic knees, they are effecting hip flexion. Conversely, knee flexion functions as hip extension.^{27, 28} In a study of 22 patients at a minimum 10-year follow-up, all had solid bony fusions and none had the fusions taken down or revised to an arthroplasty at skeletal maturity.²⁸

Brown described a second procedure in which a rotationplasty is performed in conjunction with an iliofemoral arthrodesis.²⁹ In this case, the distal femur is rotated 180º prior to fusion, with its axis parallel with that of the body. Similar to the van Nes rotationplasty, the knee functions as the hip joint and the ankle serves as the knee, thereby enabling these patients to function as below-knee amputees.

Lengthening procedures

These operations most commonly are performed in patients with congenital femoral deficiencies who do not have focal defects. The appropriate candidate has a congenital hypoplastic femur in which the hip and knee can be made functional. In a review of the experience at the Hospital for Sick Children in Toronto, successful femoral lengthening of up to 20% was possible with few complications. Beyond this, posterior knee subluxation and hip dislocation occurred.^{1, 30}

REFERENCES

Section 8 of 8

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• References

1. Gillespie R, Torode IP. Classification and management of congenital abnormalities of the femur. J Bone Joint Surg Br. Nov 1983;65(5):557-68. [Medline].
2. Oppenheim WL, Setoguchi Y, Fowler E. Overview and comparison of Syme's amputation and knee fusion with the van Nes rotationplasty procedure in proximal femoral focal deficiency. In: Herring JA, Birch J, eds. The Child With a Limb Deficiency. Chicago, Ill:. American Academy of Orthopaedic Surgeons;1998.
3. Epps CH. Proximal femoral focal deficiency. J Bone Joint Surg Am. Jul 1983;65(6):867-70. [Medline].
4. Boden SD, Fallon MD, Davidson R. Proximal femoral focal deficiency. Evidence for a defect in proliferation and maturation of chondrocytes. J Bone Joint Surg Am. Sep 1989;71(8):1119-29. [Medline].
5. Panting AL, Williams PF. Proximal femoral focal deficiency. J Bone Joint Surg Br. Feb 1978;60(1):46-52. [Medline].
6. Koman LA, Meyer LC, Warren FH. Proximal femoral focal deficiency: a 50-year experience. Dev Med Child Neurol. Jun 1982;24(3):344-55. [Medline].
7. Aitken GT. Amputation as a treatment for certain lower-extremity congenital abnormalities. J Bone Joint Surg Am. Oct 1959;41-A:1267-85. [Medline].
8. Gillespie R. Classification of congenital abnormalities of the femur. In: Herring JA, Birch J, eds. The Child With a Limb Deficiency. Chicago, Ill:. American Academy of Orthopaedic Surgeons;1998.
9. Grogan DP, Holt GR, Ogden JA. Talocalcaneal coalition in patients who have fibular hemimelia or proximal femoral focal deficiency. A comparison of the radiographic and pathological findings. J Bone Joint Surg Am. Sep 1994;76(9):1363-70. [Medline].
10. Aitken GT. Proximal femoral focal deficiency-Definition, classification, and management. In: Aitken GT, ed. Proximal Femoral Focal Deficiency. A Congenital Anomaly. Washington, DC:. National Academy of Sciences;1969.
11. Amstutz HC. The morphology, natural history and treatment of proximal femoral focal deficiencies. In: Aitken GT, ed. Proximal Femoral Focal Deficiency. A Congenital Anomaly. Washington, DC:. National Academy of Sciences;1969.
12. Pappas AM. Congenital abnormalities of the femur and related lower extremity malformations: classification and treatment. J Pediatr Orthop. Feb 1983;3(1):45-60. [Medline].
13. Hamanishi C. Congenital short femur. Clinical, genetic and epidemiological comparison of the naturally occurring condition with that caused by thalidomide. J Bone Joint Surg Br. Aug 1980;62(3):307-20. [Medline].
14. Fixsen JA, Lloyd-Roberts GC. The natural history and early treatment of proximal femoral dysplasia. J Bone Joint Surg Br. Feb 1974;56(1):86-95. [Medline].
15. Maldjian C, Patel TY, Klein RM, Smith RC. Efficacy of MRI in classifying proximal focal femoral deficiency. Skeletal Radiol. Mar 2007;36(3):215-20. [Medline].
16. Bernaerts A, Pouillon M, De Ridder K, Vanhoenacker F. Value of magnetic resonance imaging in early assessment of proximal femoral focal deficiency (PFFD). JBR-BTR. Nov-Dec 2006;89(6):325-7. [Medline].
17. Griffith SI, McCarthy JJ, Davidson RS. Comparison of the complication rates between first and second (repeated) lengthening in the same limb segment. J Pediatr Orthop. Jul-Aug 2006;26(4):534-6. [Medline].
18. Wick JM, Alexander KM. Rotationplasty--a unique surgical procedure with a functional outcome. AORN J. Aug 2006;84(2):190-214; quiz 215-8. [Medline].
19. Fuchs B, Sim FH. Rotationplasty about the knee: surgical technique and anatomical considerations. Clin Anat. May 2004;17(4):345-53. [Medline].
20. Koman LA, Meyer LC, Warren FH. Proximal femoral focal deficiency: natural history and treatment. Clin Orthop. Jan-Feb 1982;(162):135-43. [Medline].
21. Alman BA, Krajbich JI, Hubbard S. Proximal femoral focal deficiency: results of rotationplasty and Syme amputation. J Bone Joint Surg Am. Dec 1995;77(12):1876-82. [Medline].
22. Friscia DA, Moseley CF, Oppenheim WL. Rotational osteotomy for proximal femoral focal deficiency. J Bone Joint Surg Am. Oct 1989;71(9):1386-92. [Medline].
23. Kostuik JP, Gillespie R, Hall JE, Hubbard S. Van Nes rotational osteotomy for treatment of proximal femoral focal deficiency and congenital short femur. J Bone Joint Surg Am. Dec 1975;57(8):1039-46. [Medline].
24. Borggreve J. Kniegelenksersatz durch das in der Beinlangsachse um 180 degree gedrehte fussgelenk. Arch Orthop. 1930;28:175-178.
25. Van Nes CP. Rotation-plasty for congenital defects of the femur. Making use of the shortened limb to control the knee joint of a prosthesis. J Bone Joint Surg. 1950;32B:12-16.
26. Fowler E, Zernicke R, Setoguchi Y, Oppenheim W. Energy expenditure during walking by children who have proximal femoral focal deficiency. J Bone Joint Surg Am. Dec 1996;78(12):1857-62. [Medline].
27. Steel HH, Lin PS, Betz RR, et al. Iliofemoral fusion for proximal femoral focal deficiency. J Bone Joint Surg Am. Jul 1987;69(6):837-43. [Medline].
28. Steel HH. Iliofemoral fusion for proximal femoral focal deficiency. In: Herring, JA, Birch J, eds. The Child With a Limb Deficiency. Chicago, Ill:. American Academy of Orthopaedic Surgeons;1998.
29. Brown KLB. Rotationplasty with hip stabilization in congenital femoral deficiency. In: Herring JA, Birch J, eds. The Child With a Limb Deficiency. Chicago, Ill:. American Academy of Orthopaedic Surgeons;1998.
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Article Last Updated: Jan 10, 2008