Although the femur is the largest skeletal component in the lower limb, congenital deficiencies of the femur must be considered along with the associated anomalies that frequently coexist in the lower segments of the limb. The degree of femoral involvement/deficiency combined with the deficiency of the skeletal components distal to the knee joint makes each patient’s presentation almost a unique one. Therefore, surgeons must deal with a spectrum of disorders whose management depends not only on solely femoral deficiency but involvement of the whole limb. The functional compromise that can arise from a more distal deficiency may play an important role in the plan for managing a femoral deficiency. Other associated deficiencies particularly of the upper extremities influence the overall management of the child. The relationship between these additional deficiencies is briefly discussed in this chapter as they relate to femoral deficiencies. The diagnosis, management, and treatment of femoral deficiencies from the antenatal period to maturity are also addressed. The terms congenital short femur and proximal femoral focal deficiency (PFFD) and some more commonly used classifications are used because they adequately differentiate the extremes of longitudinal deficiencies, particularly regarding management.

Congenital deficiencies of the femur differ from other typical skeletal anomalies in the extent of the variations and influence of distal extremity involvement on management. Currently, in most cases, the etiology of the condition is unknown. There are a few exceptions. Bilateral femoral involvement is said to be associated with maternal diabetes and with femoral-facial syndrome as is rare Goltz syndrome, which is associated with a gene mutation on the X chromosome^1,2 (Figure 1). Of causative agents, the drug thalidomide is the best known because it caused a number of limb deficiencies in the 1960s when it was briefly used to control early pregnancy nausea in expecting mothers. Thalidomide-induced deficiencies had a more phocomelic-like, intercalary type of involvement. The drug was never approved for use by the FDA in the United States, sparing this country’s many young families of the trauma of having a newborn child with significant skeletal abnormalities.

Based on current knowledge of human embryology and intrauterine development, it is clear that most noxious insults must happen very early in fetal life. The lower limb is in place with all the important elements present by 8 weeks of gestation. It is likely that whatever intrauterine insult has taken place, it could very well be before the mother was even aware of being pregnant.

Congenital deficiencies of the femur have essentially three modes of presentation for orthopaedic management. These modes are a prenatal presentation, which is detected using
ultrasonography, initial detection at the time of birth, and later referral of an older child who had not been evaluated earlier or only partially because of some extenuating circumstance, such as residence in a remote area without access to a surgeon with expertise in managing limb deficiencies or other socioeconomic or religious factors, or possibly a relatively mild involvement whose significance may not have been initially appreciated.

The numerous classification systems for congenital femoral deficiencies suggest that no single system is satisfactory for all patients. The Hamanishi classification system⁴ demonstrates that there are many radiologic appearances and degrees of severity in congenital femoral deficiencies (Figure 4). Gillespie and Torode⁵ categorized congenital longitudinal femoral abnormalities into two major groups. At the moderate end of the severity scale is the congenital short femur, and at the more extreme end is the true PFFD. Later, Gillespie⁶ revised the classification system by adding a third group that consisted of children with a very short femoral residual limb, which is often fused to the tibia. In this group, no intervention around the knee is necessary (Figure 5) unless a rotationplasty procedure is considered. The revised
Gillespie classification system is useful in formulating a management plan and is readily understood by parents. In most instances, the Gillespie classification system helps the surgeon determine if reconstruction or prosthetic assistance would be the most appropriate course of management.⁷ The true PFFD itself has been a subject of a number of classifications by itself. The most widely used is the classification by Aitken⁸ (Figure 6).

The Aitken classification divides PFFDs into four types. Type A includes children with a radiographically abnormal proximal femur, with a pseudarthrosis that will ossify progressively with time and a varus proximal femoral deformity. These femora can be reconstructed. A type B deficiency is more severe, with a persistent defect between the femoral head in the acetabulum and the femoral shaft. These femora may be reconstructible. In type C and D deficiencies, no femoral head is present, and there is no discernible acetabulum. From embryologic studies, it is known that a hip develops from a single cartilage enlage. The cleft that appears in this cartilage block is the nascent hip joint. So, it can be said if there is no acetabulum, there is no femoral head and vice versa. It follows that attempts to reconstruct a hip joint in this situation will likely not be feasible. In Aitken type C deficiency, the femur is of reasonable size with somewhat bulky proximal end In type D deficiencies, the femur is rudimentary and tapered proximally, and no proximal reconstruction should be attempted⁸ (Figure 7).

The classification by Paley and Stannard⁹ is useful for guiding surgical intervention and reconstruction, particularly in patients with more severe proximal femoral and diaphyseal deficiencies. On one end of the severity spectrum, congenital femoral deficiency management involves treatment of a modest limb-length difference, and at the other end is a gross limb discrepancy and the need for prosthetic assistance (Figure 8).

Within this spectrum is a dividing line between patients who can be treated with limb reconstruction and those who are best treated with limb ablation and prosthetic restoration (Figure 9). The additional confounding factor is that many of these children have associated involvement of the distal part(s) of the extremity. For the extremity to be rendered functional by either surgical or prosthetic means (or their combination), several parameters have to be considered. Pelvic femoral articulation has to be at least moderately stable with reasonable range of motion. The same goes for the knee joint and ankle joint to allow for relatively normal biomechanical alignment and function and to potentially withstand a lengthening procedure. To address these issues in a simple treatment guiding algorithm,
Krajbich and Alman proposed a classification based on (1) reconstructability of the hip joint and (2) integrity of the ankle/subtalar joint in patients with PFFD (Tables 1 and 2).

It is also important to recognize that management decisions are influenced by the mores of the society in which the patient resides, the skill and experience of the surgeon, and the wishes of the family.