Orthopedics - Oleksa A.P. 2006

Congenital and acquired deformities of the lower limb
Congenital and acquired deformities of the hip
Femoral hypoplasia

Femoral hypoplasia is characterized by bone mass defects resulting in limb length discrepancy. They are divided into two main categories:

— complete or partial bone hypoplasia;

— femoral hypoplasia.

A significant number of proposed classifications (Aitken G., Gillespie; Kalamchi; Pappas et al.) were essential and played a major role in understanding this pathology.

Pappas (Pappas A.M., 1983) described 9 types of congenital anomalies (Fig. 129), including distal femoral abnormalities (Class VI), which are frequently excluded from other classifications. This Classification encompasses all types of hypoplasia, ranging from local abnormalities to hypoplasia of the entire Femur, as illustrated in the figure (Classes V–IX).

The limb bud in a 5 mm embryo appears during the 4th week (Felts W.J., 1954, Gardiner E., Gray D.J., 1950). The Development of the pelvis, acetabulum, and femur is interrelated. The first signs of acetabular development are observed at the 5th week. At the same time, mesenchymal Condensation appears at the proximal end of the femur (Lange D.R., Schoenecker P.L., Baker C., 1978).

If a teratogenic factor acts at this stage, pathological changes may occur, manifesting as the absence of the acetabulum and femur.

Between the 5th and 6th weeks of embryonic development, the pelvis and femur form two separate cellular structures, but the femoral HEAD develops from the pelvic Structure (Pappas A.M., 1983).

Between the 6th and 8th weeks, the model of the femoral diaphysis is already complete, after which it begins to undergo chondrification. Joint cavities also appear between the 6th and 7th weeks. Ossification of the femur occurs both proximally and distally toward the metaphyses around the 12th week of intrauterine development. Vascularization and ossification spread into the region of the femoral neck and head between the 15th and 40th weeks. Disruption of normal chondrification or endochondral ossification processes leads to various manifestations of Congenital Malformations, depending on the timing and Variability of the harmful factor's impact (Hillmann J.S. et al., 1987).

Clinical Manifestations. At birth, the affected limb is shorter and exhibits a characteristic posture, though the exact Water/144.html">Origin of the congenital defect requires further elucidation. A common feature of all these malformations is the flexion posture of the limb at the Hip and knee joints. This may be combined with Malformations of the distal limb segments.

Fig. 129. Anomalies and malformations of the femur according to Pappas A.M. (1983): I — absence of the femur and Fibula; II — absence of the femoral head; III — Separation of the femoral Head and Neck; IV — irregular ossification of the fibrocartilaginous matrix of the neck; V — abnormal femur due to hypoplasia and insufficient ossification; VI — abnormality of the distal femur due to process hypoplasia and absence of one of the paired BONES OF THE leg; VII — Varus deformity of the proximal femur due to hypoplasia and underdevelopment of the greater trochanter, resulting in valgus; VIII — valgus deformity with femoral hypoplasia, underdevelopment of the greater trochanter, and valgus deviation of the distal femur; IX — hypoplasia of the entire femur.

An accurate Diagnosis established during the neonatal period is crucial for Treatment planning (Gillespie R., Torode I.P., 1983). Gillespie and Torode point out that from a clinical examination standpoint, it is essential to distinguish two different patient groups. The first group has a shortened femur but a stable hip joint. They possess a cartilaginous head, neck, and greater trochanter, which may remain invisible until they become radiopaque.

In the second group, clinical manifestations are entirely different and consist of a true localized proximal focal femoral deficiency. In these cases, the authors note that the femoral segment of the limb is markedly shortened with abduction and external rotation. Flexion contractures at the hip and knee joints are permanently fixed at various angles and do not respond to conservative correction Methods, which distinguishes these patients from children in the first group.

According to Pappas' classification, the first group of patients corresponds to Classes V–IX, while the second group corresponds to Classes I–IV.

Radiographically, it is necessary to differentiate between patients whose condition tends to develop favorably and those with a pronounced true proximal focal femoral deficiency (Pappas Classes I–IV), which is considered valuable for prognosis.

Fixsen and Lloyd-Roberts (Fixsen J.A., Lloyd-Roberts G.C., 1974) observed A number of important features on early radiographs. In all cases, the proximal end of the femur was not visible. They noted that when the acetabulum appears, the femoral head is already present, but its ossification may be delayed. This has also been confirmed by other authors (Amstutz H.S., 1969; King R.E., 1969; Sanpera I.Jr., Sparks L.T., 1994; Goddard N.Y., Hashemi-Nejad A., Fixsen J.A., 1995). It was also noted that if the Base of the proximal femur initially has a bulbous shape, subsequent development proceeds due to joint stability. These same authors point out that pseudarthrosis may occur in this case, but in the subtrochanteric region. It is emphasized that if in a child under one year of age the apex of the ossification center appears detached from the proximal end of the diaphysis (which has a blunted configuration) and this appears on the radiograph as a radiolucent area, the joint will likely be unstable in the future. The authors classified this variant of the defect as Type 2. In reality, whether joint stability will be achieved is determined by the contour shape of the ossified proximal end of the diaphysis. If it is blunted, with irregular contours and notches, instability may occur, which is radiographically classified as Type 3.

Additionally, it is indicated that the appearance of ossifying Changes in the femoral diaphysis can serve as a basis for identifying the malformation. In stable cases (when a cartilaginous model for The formation of the head and trochanteric region is present), ossification appears in the femoral diaphysis closer to its middle third.

In unstable cases (Types 2 and 3), ossification is traced in more proximal Regions of the femur, located distally to the pseudarthrosis or angular deformity, and typically has the shape of an inverted letter V (Fixsen J.A. et al., 1974). Therefore, unstable Types 2 and 3 can be attributed to Classes II–IV according to Pappas' classification.

Radiological interpretation is necessary to prevent the development of pseudarthrosis while the structure is still cartilaginous and slowly ossifying (Hillmann J.S. et al., 1987). The critical timeframe for reliable diagnosis is considered to be 15 months of age, when reliable radiographic evaluation becomes possible (Goddard N.J., Hashemi-Nejad A., Fixsen J.A. et al., 1995).

Magnetic Resonance imaging was performed by Pirani and Hillmann. This technique enables early diagnosis while structures are still cartilaginous, allowing better visualization of the femoral head prior to ossification.