COXA VARA DUE TO CONGENITAL DEFECT OF THE NECK OF THE FEMUR By H. A. T. FAIRBANK, D.S.O., M.S., ETC. THE condition of the femur described in this paper is usually called cervical or infantile coxa vara. Coxa vara is said to exist when the angle of inclination of the femur is below normal limits, say, below 1250. The particular type of coxa vara dealt with here is associated with characteristic anatomical peculi- arities. Before describing the anatomy it would be well, perhaps, to refer briefly to the chief clinical features of this type of case. The onset is usually insidious and the history somewhat vague, but in many the limp, which always accompanies the deformity, is said to date from the time the child began to walk. Both sexes are affected without any great preponderance in either. In at least a third of the cases the condition is bilateral. Occasionally this type is seen on one side and a simple coxa vara on the other. There is a marked limp and in the bilateral cases a waddling gait not unlike that so commonly seen in congenital dislocation of the hip joints. The children complain of stiffness after rest, and pain after walking, in fact many, more particularly those with bi- lateral deformity, are severely crippled. Some of the cases are well below the average in height. On examination the chief features seen are raising of the trochanter, with, of course, shortening of the limb, marked limitation of abduction, and to some extent of rotation. The hip is usually flexed, extension being limited or obliterated, and there is marked increase of the normal lumbar spinal curve, i.e. lordosis. The age at which the cases commonly come before the surgeon is 6 to 8 years, but, as already stated, symptoms commonly date from much earlier. As can be readily understood from the radiographic ap- pearances, there is a strong tendency to increase of the deformity, but this does not invariably occur. The worst cases of coxa vara met with in adult life, apart from fractures, are the result of this affection. Our knowledge of the anatomy of these cases is almost entirely gleaned from the study of the radiographic appearances, which vary considerably with the age of the patient and the degree of the deformity. The fundamental ana- tomical abnormalities are best seen in the younger children with deformity of moderate degree. All the essential features are seen in fig. 1, which shows the hips of a boy aged 6j years with bilateral coxa vara. Briefly the following are the changes seen in both hips: 1. The angle of inclination is reduced to something below a right angle. 2. The head of the femur is unusually translucent, is situated rather low in the acetabulum, and seems to be abnormally thick or deep, as if the ossific Coxa Vara due to Congenital Defect of Neck of Femur 233

Fig. 1. Bilateral infantile or cervical coxa vara, showing triangular portion of neck ossifying by separate centre. (Boy aged 6j years.)

Fig. 2. Unilateral infantile coxa vara showing triangular fragment partially fused to neck. (Aged 10 years.) 234 H. A. T. Fairbank centre were extending into the neck and displacing outwards the epiphyseal line. This is more obvious above than below. 3. There is a fragment of bone, roughly triangular in shape, occupying the lower part of the neck. This fragment, the density of which approximates to that of the rest of the bone rather than to that of the head, is bounded by two clear bands traversing the neck, and forming together an inverted V. The inner of the two limbs of this V is undoubtedly the epiphyseal line, while the outer is quite abnormal, and its presence constitutes, with the triangular fragment, the characteristic feature of this type of coxa vara.

Fig. 3. Infantile coxa vara, later stage, Fig. 4. Infantile coxa vara, later stage, showing showing greatly depressed head and neck fairly well formed but greatly depressed. short neck. Now what is the fate of this fragment of bone? If the deformity pro- gresses the fragment retains its relation to the head and descends with the latter. In older children it is more difficult, and it may be impossible, to dis- tinguish this piece of bone. It has been recognised in one hip as late as 8 years, and in both femora at 10 years. It may fuse with the neck and then appears as a lip projecting nearly vertically downwards (fig. 2). The neck seems to be striving to retain some connection with the grossly depressed head. On the other hand the abnormal clear band in the neck may remain, in which case presumably the fragment fuses with the head. The later stages of the de- formity reveal two distinct conditions. In one the neck is poorly formed and seems almost non-existent, while the head lies so low that it is opposite the shaft rather than the trochanteric region of the bone (fig. 3). In the other Coxa Vara due to Congenital Defect of Neck of Femur 235 there is a neck of good length, but this is inclined downwards to reach the head, and forms an acute angle with the line of the shaft (fig. 4). The patho- logical evidence of the nature of the condition is very meagre, Elmslie only being able to find four specimens, all obtained from adults with gross deformity. There was a narrow fibrous intersection present in the neck of the femur. In children the abnormal clear line in the neck is presumably occupied by unossi- fied cartilage, or possibly by fibrous tissue. What is the explanation of this curious condition? How are we to explain the presence of the triangular piece of bone? It is on this point that the anatomists can. I think, help the surgeons. The factors, according to Elmslie, that have to be considered as possibly playing a part in the causation of the condition are trauma, either at birth or later, and rickets. The latter can be dismissed at once: this deformity has no connection whatsoever except by accident with rickets. The deformity can apparently arise as a result of injury, since Elmslie mentions a case of Joachimstal in which the history of trauma was very definite, but it is inconceivable that trauma could produce identical lesions in both femoral necks, either during the birth of a child or later. To my mind the close symmetry seen in the bilateral cases puts trauma entirely out of court. That a condition closely resembling this may be seen after injury only goes to prove that similar abnormal appearances may result from diffe- rent causes. I venture to suggest that this condition is really a congenital developmental error, the coxa vara deformity being secondary to this. It amounts to this, that the diaphyseal spur, as Prof. Walmsley calls it, which plays such an important part in supporting the femoral head, is ossified from a separate centre and not by direct extension from the shaft. It is possible that more than one nucleus of ossification may contribute to the formation of this separate fragment in some cases, since some of the radiograms seem to suggest this. My reasons for suggesting developmental error to explain the deformity are these: 1. Some error in gait is often noticed when the child begins to walk. In 4 of my 18 cases there is a definite history of something being wrong about the end of the first year, the history in several others being very vague and indefinite, and certainly not against this theory. 2. The deformity is extraordinarily symmetrical in bilateral cases. The abnormal clear line running through the neck is seen in precisely the same situation in both femora. 3. It is sometimes met with in association with other developmental errors, e.g. it has been seen in that curious condition called cranio-cleido- dysostosis. In this condition the skull is ossified late or imperfectly, and the clavicles are each represented by one or two separate pieces, or these bones may be entirely absent. This radiogram (fig. 5) is taken from a case of dysostosis aged 6 years, kindly transferred to me for treatment by my colleague Mr Barrington-Ward, and shows the condition discussed here. Besides the triangular fragment and 236 H. A. T. Fairbank the coxa vara, it shows the femoral heads are lying low in the acetabula, and the ossific centres for the heads are encroaching on the necks above, while in addition the pubes show no sign of ossification whatsoever. On examination of the patient the symphysis pubis seemed to be well formed, so presumably the pubes are cartilaginous. This case shows other abnormalities ofthe skeleton, to which attention was directed by Mr Barrington-Ward when he showed another case before the British Orthopaedic Association in 1924. The errors in that case, aged 38 years, were: (a) No ossification of the parietal bones. (b) Double centres for the epiphyses of metacarpals and phalanges. (c) No ossification in pubic bones. (d) Two small centres for the clavicles-ununited. (e) Delayed fusion of the mandible and neural arches. In that case there was no coxa vara.

Mig. 5. Bilateral infantile coxa vara with absence of ossification in pubes. (Case of cranio-cleido-dysostosis; girl aged 6 years.)

However, Mr Irwin of Belfast sent me radiograms of a third case of dysostosis which showed typical cervical coxa vara in addition to the other abnormalities, so that in two of the three cases coxa vara of the type under con- sideration was found. Unfortunatelythere is no certain evidence, so far as I know, of cervical coxa vara being present at birth. When the condition of the upper end of the femur in the early months of life is remembered, it is not surprising that no radio- graphic evidence of this congenital abnormality in young infants is forth- coming. The youngest case I have met with was aged 21 years, while another Coxa Vara due to Congenital Defect of Neck of Femur 237 was 3 years old. So far as I know abnormal ossification of this type in the neck of the femur is not mentioned in the text books on Anatomy. The only con- dition I am familiar with which in the least resembles it occurs at the lower end of the femoral diaphysis where occasionally one sees a corner, adjacent to the lower epiphyseal line, separated from the rest of the metaphysis. If my suggestion is correct, and this is a developmental error, it seems to me possible, even probable, that the ossification of the diaphyseal spur by a separate centre is normal in one or more species of the lower animals. Supposing this buttress of bone were ossified separately but later fused with the rest of the neck and with the head of the femur, the unusual method of ossification might easily be overlooked even by those familiar with the skeleton of the particular species concerned. The difficulty experienced in obtaining information on this point has in- duced me to follow the suggestion of one of your members and bring the sub- ject before you to-day. Note. The author would be very grateful to any anatomist who can throw light on the nature of this condition, if he would be kind enough to communi- cate with him.

Anatomy LXUII 16