Proximal Femoral Focal Deficiencies

Richard E. King, M.D.


"Whenever a large sample of chaotic elements is taken in hand and marshalled in order of their magnitude, an unsuspected and most beautiful form of regularity proves to have been latent all along."

Galton, "Natural Inheritance"
1889

The definition of proximal femoral focal deficiencies has presented considerable difficulty. Initially, I had felt that all proximally deficient femora were variants of coxa vara. However, review of X-rays on approximately fifty cases of proximal femoral focal deficiency have resulted in formulation and maturation of a concept that seems to be corroborated by study of the early development of the hip joint. I now believe that coxa vara is a separate entity remote from proximal femoral focal deficiency. The former is probably related to a mechanical disturbance in the proximal femur; whereas the latter is most likely due to an early developmental disturbance of the proximal femur, resulting in its deficiency.

I have taken the liberty of presenting a sketch of the four types of deficient femora as proposed by Dr. George T. Aitken (Fig. 1 ). Two of these four types I would consider as representing coxa vara, rather than proximal femoral focal deficiency. That is, I suggest that Types A and B, which have elements of the proximal femur present, are severe forms of the coxa vara. Types C and D, which have no acetabulum and consequently no head or neck, I would agree in calling proximal femoral focal deficiencies.

Embryological Contributions

To substantiate the above positions, assistance and support has been forthcoming from the embryological contributions. (The following is quoted freely from various sources and has been combined to develop the above concept.)

Fig. 2 A represents a 17 mm. embryo and shows the approximate size of the limb bud, together with the actual histological development of the hip joint at this stage (Fig. 2 B and C). The ilium, ischium and pubis still consist of precartilage and the acetabulum shows little increase in its concavity. By this time the head of the femur is slightly rounded, and while the acetabulum is not much more concave than in younger specimens, there is nevertheless a slight depression more marked medially which contains loose tissue and Indicates a primitive acetabular fossa.

At 22 mm. (Fig. 3 A, B and C), the acetabulum deepens medially. Both trochanters are now well defined, but the neck of the femur is short. Note the beginning of cavitation at the periphery of the interzone where dissolution is occurring to form the acetabular cleft. As chondrification proceeds in the blastemal anlagen, the portion of the blastema between femur and acetabulum remains unchondri-fied to form a disc or interzone. However, at 20 mm. its middle portion becomes lighter in staining density and a three layered arrangement is evident.

At 30 mm. (Fig. 4 A, B, C and D), the acetabular cavity is well developed, but obliterated at the center (L.T., ligament teres. T.L., transverse acetabular ligament). Fig. 5 A, B, C, D and K trace the embryologlca1 development of the life in fetuses from 73 to 270 mm. At 73 mm., Fig. 5 A shows the acetabular fossa, fovea capitis femoris and early vascularization at the femoral neck and near the glenoid lip. C.C., cartilage canals. In Fig. 5 B, at 106 mm., vascularization is considerably advanced and ligaments well defined. O.N., obturator nerve; S.N., sciatic nerve; Z.O., zona orbicularis. Fig. 5 C at 180 mm., shows increased ossification and vascularization. Fig. 5 D at 250 mm., depicts the proximal extent of diaphyseal ossification. At 270 mm., the fovea capitis filled with vascular tissue sharply demarcated from cartilage is shown in Fig. 5 B.

A composite of fetuses from 44 mm. to 126 mm. is shown in Fig. 6 to indicate the relative external appearance of the lower extremity. After eight or nine weeks of development, the general form of the hip joint resembles that of the adult.

The study of the hip joint in the embryo indicates that this joint develops from a common anlagen for the head of the femur and the ilium; that an area of dissolution occurs in this anlage at an interzone to develop a cleft and the subsequent Joint cavity.

Conclusions

Therefore, can we not infer that if an acetabulum exists (Fig. 1 , Types A and B), then elements of the proximal femur will always be present? If this be so, and an acetabulum exists, eventually elements of the proximal femur will present themselves as the patient grows older. This conclusion appears o be substantiated by a review of X-rays of fifty cases from various sources. This condition then would represent a severe coxa vara. Conversely, if an acetabulum does not exist and never develops can we not infer that no elements of proximal femur will develop and we have a proximal femoral focal deficiency (Fig. 1 , Types C and D)?

Richard King is Clinic Chief, Georgia Juvenile Amputee Clinic, Crippled Children's Service, Georgia Department of Public Health, Atlanta, Georgia

References:
Aitken, G. T.: Personal Communication, Meeting of Clinic Chiefs, January 25, 1964, Chicago, Illinois. 
Gardner, E. and Gray, D. J.: "Prenatal Development of the Human Hip Joint," Amer. Journ. Anat., 87: 163-211. 1950. 
Hamilton, W. J., Boyd, J. D., and Mossman, H. W. : "Human Embryology," Baltimore: Williams and Wilkins Company, 1952. 
Harrison, T. J.: "The Influence of the Femoral Head on Pelvic Growth and Acetabular Form in the Rat," J. Anat., 95: 12-24, 1961. 
Lawrenson, R. D.: "Bilateral Anomalous Development of the Hip Joint," J. Bone and Joint Surg., 46-A: 283-292, March, 1964. 
Sevastikoglow, John A.: "Insulin Induced Micromelia in Chickens," Acta Orthopaedica Scandinavica, Vol. XXXIII, fasc 4, pp. 271-290, 1963. 
Tschumi, P. A.: "Growth of Hind Limb Bud of Xenopus Laevis and Its Dependence upon the Epidermis," J. Anat., 91: 149-173, 1957.