Concepts Of Proximal Femoral Focal Deficiencies

Richard E. King, M. D.

The concepts developed in this article should be regarded as tentative since we have had only 17 patient X-ray? to review. From these findings, however, certain thoughts regarding Proximal Femoral Focal Deficiencies begin to crystalize. We hope to continue our observations and to either strengthen or refute the preliminary conclusions we are presenting here.

Although my thoughts pertaining to Proximal Femoral Focal Deficiencies are seemingly at variance with those of Dr. George T. Aitken, I wish to acknowledge the stimulus of his work at this time.

I propose to place infantile and congenital coxa vara in the same group and include proximal femoral focal deficiencies. The latter, in some patients, appears to be merely a variation of the early stage of the same condition. Prior to developing this concept, however, we must make several general statements and attempt to understand part of the basic embryological background. First, we should be aware that congenital defects of the femur are rare. Our conclusions are based upon 13 cases that we have collected from various sources.

Congenital Defects

Before the development of this deficiency can be comprehended, a long-term follow-up by X-ray would be necessary as we feel that the final developmental end product represents a variant of congenital coxa vara. Without a long-term follow-up, one can easily misconstrue X-rays seen on very young patients and attempt to segregate them into various categories. Despite the possible erroneous conclusion that might be attained without serial films, the rational basis of treatment will still be on a mechanical re-alignment of the segments of the femur, in the hopes of attaining a better weight-bearing line.

These defects, viewed with justifiable dread by every expectant mother, are recognized by physicians in all branches of medicine and treated with some success by surgeons, but still are not prevented. They occur with a frequency which has not abated and which may be increasing. Hope of preventing the tremendous loss and crippling caused by these defects rests upon an understanding of their cause sufficiently sound as to permit effective preventative measures. Search for the knowledge of causes has occupied countless imaginative persons through the ages. More recently, experimental techniques have been applied to this problem and a degree of progress has been made. (More will be said of this later.)

Congenital anomalies are those structural abnormalities present at birth which can be expected to interfere with the normal functioning of an individual. Since congenital anomalies by definition are present at birth, they must be present before birth either in a developing or full developed form. The cause of most congenital anomalies in man is still unknown at this time.

Neel suggests that about 10% of human malfunctions can be explained on the basis of a penetrant single genetic factor. In another 10% of cases, a condition such as diabetes, exposure to X-rays or atomic radiations, an acute febrile illness of the mother, malnutrition or other abnormal maternal conditions can be demonstrated. In the remaining 80%, the cause is still unknown but a number of possible explanations exist.

This article will not discuss the experimental and clinical causes of congenital developmental anomalies which include infections, physical injuries, hormones, nutritional deficiencies, respiratory defects and embryonic defects involving abnormalities of ovum, semen and possibly antigen antibody reaction. The work of Duraiswami and Warkany will be cited regarding possible factors in the etiology of congenital malformation.

It should be realized that the ossification center of the femur appears on the 42nd day and grows gradually, being 1 1/2 mm. long on the 55th day. On the 58th day of its development, it is 4 mm. long; on the 75th day 8 mm., and on. the 85th day 14 mm. long. Photographs taken from the work of Bardine and Lewis (see Figure A ) show an embryo at 4 1/2 weeks. At the center of the base of the limb bud, the femur and hip bone are beginning to be differentiated by the formation of a dense mass in the mesenchyme. Figure B is a lateral view depicting the skeletal rudiment of the femur and hip bone. Figure C shows the skeleton consisting of hip bone, femur, tibia and fibula, which are composed of embryonic fetal cartilage covered by dense mesenchyme and a dense mass of tissue which is the anlage of the ankle and foot.

Warkany's Views

A review of the current concepts in proximal femoral focal deficiencies indicates that there is arrest of the developing limb at a particular moment. Warkany states "that a continuous chain of chemical reactions regulates the development of the unborn child from the first cell, zygo to complex multicellular organism of the newborn. Any interruption of these reactions resuits in damage to the embryo fetus, me of injury is of great importance since defects are determined to a certain extent by the developmental state of the effected organism. In general, damage is more serious the earlier the embryo is injured. All the organs and organ systems are essentially determined and recognizable by the third month. In this first period, the embryo is extremely vulnerable and injuries result in severe deformities."

Warkany observed that a shortening of the lower jaw, shortening or absence of the tibia, fibula, radius and ulna, fusion of ribs and syndactyly occurred in about one-third of the offspring of female rats fed a diet deficient in riboflavin. He makes no mention of proximal femoral focal deficiencies.

Duraiswami's Work

The work of Duraiswami is extremely gnificant and essential to the develop-'nt of our present understanding. The table of insulin induced skeletal abnormalities in rats showed that the date of injection of the embryo definitely determined the point of the body primarily effected. If insulin was introduced the first and second days, the vertebral column was effected; the third day, the feet were effected; the fourth and fifth days, the limbs and beak of the chicken embryos were effected; and the sixth day, the hip area was involved.

Duraiswami concluded: "It is reasonable to attribute the defective ossification of the cartilaginous skeleton of the insulin treated embryos to an abnormal carbohydrate metabolism; thus, insulin induced hypoglycemia may deprive the mesenchyme, precartilage and cartilage of glycogen and mucopolysaccharides depending on the time of the injection and its dose and thus give rise not only to a variety of single and multiple deformities of the cartilaginous skeleton but also to defective endochondral sification which may result in a generalized developmental disturbance of bone resembling osteogenesis imperfecta in man."

One of the slides in Duraiswami's paper shows a definite dissolution of the proximal aspects of the femur suggesting proximal femoral focal deficiencies. He believes, however, that dissolution is more common at the distal end of the femur.

Early Recorded Evidence

An attempt was made to discover the earliest recorded evidence of proximal femoral focal deficiencies. The remains of 6,000 bodies found in the Mile Valley before the flooding of the valley during the construction of the Aswan Dam were examined. Five cases of proximal femoral focal deficiencies were discovered and Wood Jones, who reviewed the bodies, attributed the condition to a separation of the capital femoral epiphysis. (Figure D and Figure E depict some of the characteristics of the deformity as we know it and typify what I consider a suggestion of a proximal femoral focal deficiency.)

The five bodies probably did represent cases of proximal femoral focal deficiencies since no other incidence of separation of any of the epiphyses of the body had occurred. There were other interesting factors; all five of the cases were women and all were found in one small district of the valley, three in the same cemetery and two in adjacent graves. Jones stated that this situation was "one of the strange coincidences that happen in the examination of large quantities of material," i.e., that three women, in graves situated close together, showed this rare form of injury, and yet only two other cases were found in the remainder of the 6,000 bodies.

All of these women were of the Christian period and belonged to the Foreign Christian Colony which settled around the Temple of Fhilae. Jones declared that "the noteworthy point was the entire absence of the neck of the femur and It would appear that it was lost subsequent to the injury." The injury must have occurred after the fourth year if the head of the bone was separated as an anatomical entity. Previous to that, the whole of the upper extremity of the fetus, including head, neck and greater trochanter, forms one undivided mass of cartilage and violence would result in separation of the entire mass.

After the fourth year, the head becomes separable but by that time the neck of the bone is well defined. Hence, the condition of the absence of the neck observed in these examples must be a secondary one. Jones goes on to describe what probably represents the X-ray appearance of a calcified thin fibrous line existing between the shaft of the femur and the head. (We proposed to show that this occurs in almost all of these cases provided sufficient time elapses.) Jones stated, "It is most probable in the altered condition of the joint that the small neck becomes worn away and flattened until it is finally represented by only the flat surface which stretches between the two trochanters and forms the upper extremity of the bone."

Golding's Views

In developing the concept stated at the beginning of this article, I propose to draw freely from the work of Campbell Golding. In his report, both infantile and congenital coxa vara were grouped and included "micromelia due to short femur" (proximal femoral focal deficiency). Golding believed that this condition existed merely as a variation of, and in some patients, the early stage of the same condition. It is his impression that radiographic features of coxa vara were:

  1. Oblique vertical defect in the neck

  2. Short neck

  3. Fragmented neck

  4. Incomplete ossification in part of the neck

  5. Beaking of the great trochanter

  6. A facet formed by the trochanter on the ilium

  7. Secondary deformity of the acetabulum due to a malposed head

Not all of the features listed above were necessarily present in each patient. Various stages of development may also be shown by a series of X-rays with different patients, commencing with minimal deformity and working backwards to gross maldevelopment in the femoral neck. Minimal deformity necessary to establish a diagnosis consists of an oblique or vertical epiphyseal line. These are patients who presumably began with perfectly ossified necks which ultimately developed normally (Figure 1 and Figure 2 ).

The next stage in this condition is due to defective ossification in the neck. This may be attained as (a) a very short neck (Figure 3 ), and (b) complete ossification, especially towards the femoral head (Figure 2and Figure 3 ). Fragmentation of the neck either in the form of a small bony fragment lying in cartilage or a "V" shaped fragment which may be present at the upper or lower border of the neck (Figure 4 ). The latter is probably the most frequent type of coxa vara.

The next stage of the deformity consists of a varying degree of aplasia of the upper half of the shaft of the femur. The upper half of the femur is short and thin; in the area of the lesser trochanter there is often a second varoid deformity. The cortex at this level may be increased in width or replaced to some extent by a translucent zone resembling a fracture. The translucent zone may extend completely across the shaft with marked varus at the site. In other words, the neck is not the only site where ossification may be incomplete. This may also "cur below the trochanter, forming, a second translucent zone.

The peculiar features at the upper translucent zone in the neck disappear much earlier than the normal epiphyseal lines (Figure 5 , Figure 6 , Figure 7 , and Figure 8 ). In Golding's description, the stages or process have been described in reverse order. Golding tells of three patients who had been observed for many years. He illustrates the imperfecta progress of the deformity commencing with-only the lower half of the femur, formed in bone to development of the malformed shaft and neck. One of these patients formed a comparatively good shaft, but the ossification at the upper end was incomplete and resulted in congenital coxa vara. These segments taken from Golding's work are shown in Figure 9 , Figure 10 , Figure 11 , and Figure 12 .

Importance of Ossification

Fairbanks stated that varus increased with age unless ossification took place. This is probably the single most important point in the disease from a prognostic and also from a treatment standpoint. For this reason an attempt could be made by osteotomy or by mechanical re-alignment to allow ossification to take place so that varus deformity does not increase. Later stages, depicted in Figure 13 and Figure 14 , result when a neck is imperfectly ossified. The upper part is usually more complete than the lower.

We have attempted to establish that Proximal Femoral Focal Deficiencies are perhaps a variant of coxa vara. It is hoped that further long-term study will reveal this to be true.

Richard King is Clinic Chief, Amputee Clinic Atlanta Orthopedic Clinic Atlanta, Georgia