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CONGENITAL ABNORMALITIES OF THE FEMURBY

P. A. RINGFrom the Royal College of Surgeons

(RECEIVED FOR PUBLICATION NOVEMBER 25, 1960)

Congenital defects of the femur vary from simplehypoplasia of the bone to complete absence.Classification of these defects has been suggestedby Nilsonne (1928) and by Mouchet and Ibos (1928),but neither has met with general acceptance. Inmore recent years Golding (1939, 1948) has demon-strated the close association of the short femur withcongenital coxa vara, and has emphasized thatthese are variations of the same underlying abnor-mality. The clinical distinction between the varioustypes of femoral defect is important as a guide tothe prognosis of limb development.From an examination of patients with congenital

abnormalities of the femur the following classifica-tion is suggested:

1. Simple femoral hypoplasia.2. Congenital coxa vara.3. Femoral hypoplasia with coxa vara.4. Pseudarthrosis of the femur.5. Hypoplasia of the lower femoral epiphysis.6. Complete absence of the femur.Although these patients commonly have other

skeletal defects, the major congenital abnormalitiesaffecting the nervous system, or in the chest andabdomen, appear to be rare. Their span of lifeis thus rarely affected, and detailed autopsy orpathological examination of the limb is rarelypossible. From the clinical examination of thesepatients, however, and from serial radiographs,much information can be obtained about the clinicalcourse of the limb abnormality, and the nature ofthe underlying disturbance of growth.

Clinical MaterialThe records of the Royal National Orthopaedic

Hospital and The Hospital for Sick Children forthe past 10 years have been examined, and patientswith this diagnosis have recently been reviewed.With the addition of one case from Guy's Hospital,38 examples of this defect have been collected, 19 ofthese have been reported in detail elsewhere (Ring,1959) under the title of simple femoral hypoplasia,and will only be considered briefly. A true indica-

tion of its incidence is difficult to obtain, but itappears to be the commonest congenital defectcausing major abnormalities of limb growth.

Clinical Features

There is no evidence that this is a familial disorder,and careful inquiry of the parents has revealed noevidence of other congenital disorders within theimmediate family. The history of the pregnancyand delivery has failed to indicate any significantinfection or abnormality at this time. In mostpatients the abnormality is apparent at birth, butwhere the inequality of leg length is slight, thediagnosis may not be made until the child begins towalk. To ordinary clinical testing the abnormalityis confined to the skeleton; there is no evidence ofan associated muscular or nervous abnormality,although in the presence of gross defects muscleattachments may be bizarre. Occasionally thereis also a partial or complete absence of the fibula,usually with an associated foot defect. In thepresent series this has always involved the sameside as the femoral defect.

Simple Femoral Hypoplasia (19 cases). Theaffected thigh is shorter than its fellow, but mayappear more bulky. It is often bowed laterally, andthe patella is high and small. The leg is held inexternal rotation, and the hip cannot be rotatedinternally beyond the neutral position. Radio-graphs of the femur show no abnormality apartfrom the shortening, but there is usually somethickening of the cortex of the femur at the centre,and a small beak on its outer side. The radiographsoften resemble those of a healed birth fracture, andmany of these cases were initially regarded in thislight. The distinction is an important one since thecongenital short femur always grows less rapidlythan its fellow, and the inequality of leg lengththerefore tends to progress. In this group thedefinitive shortening does not usually exceed threeinches and may well be less.

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CONGENITAL ABNORMALITIES OF THE FEMUR

iIG. 1.-Congenital coxa vara showing deformity of the head andneck and elevation of greater trochanter.

These cases have already been considered in detailelsewhere (Ring, 1959).

Congenital Coxa Varm (three cases). Abnor-malities in the hips of these patients are rarelydetected before they start to walk, although limita-tion of abduction, and a very slight shortening of

the limb, if the lesion is unilateral, are apparent atbirth. Where both hips are affected there is awaddling gait, and a pronounced lumbar lordosis.Both abduction and internal rotation of the hipare limited, but the head of the femur can usuallybe felt in the acetabulum.

In the early radiographs ossification of the headof the femur is usually delayed. The varus defor-mity of the femoral neck may be apparent soon afterbirth, but more commonly develops during thesecond year of life. Ossification defects in the lowerpart of the femoral neck are common, but notinvariable. In this small group mineralization of thehead and neck has proceeded relatively normally(Fig. 1). The length of the femur is probablyaffected mainly by the deformity of the upper end,and the shortening of the limb rarely exceeds one inch(Table). Indeed, true growth in length of the femur,from trochanter to femoral condyles, often appearsunaffected.

Femoral Hypoplasia with Coxa Vara (five cases).This type of defect combines the features of the firsttwo groups. The shortening of the limb is usuallynoticed at birth, or during the early months of life.There is an asymmetry of the thigh creases, and theleg is held in external rotation (Fig. 2). Internalrotation of the hip is absent, and abduction limited.The greater trochanter is elevated, but there is no

iBLE

Case No. Age Shortening Treatment Associated Defects(years) (in.)

Congenital short femur:*1 2* 1 None2t 7 None Bilateral osteotomy3 15 1i None

Femoral hypoplasia with coxa vara:4 10 4 Stapled None5 5 4 (femur) Extension prosthesis Absent fibula

2 (tibia)6 7 2 None Scoliosis with congenital abnormalities7 16 Unknown Amputation through knee Premature fusion head of femur8 12 5 Extension prosthesis None

Pseudarthrosis of the femur:9 20 71 Patten None10 4 71 Symes' amputation Partial absence of fibula11 6 Unknown Arthrodesis of knee; Symes' amputation None12 2 5 None None13 6 Unknown None None14 * 3 Bone grafting None

Hypoplasia of the lower femoral epiphysis:15 4 2 None Genu valgum

Complete absence of femur:16t 5 None Bilateral prosthesis Talipes; absent fibula; congenital

amputation of arms

Bilateral short femur:17t 3 Unknown Prosthesis Absent fibula18t 10 5 High boot Fixed flexion hip and knee19t 7 2j Caliper Genu valgum

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* Excluding simple femoral hypoplasia. t Bilateral.




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ARCHIVES OF DISEASE IN CHILDHOOD

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FIo. 3.-Coxa vara and short femur. The secondary centre

for the head of the femur has not yet appeared.

FIG. 2.-Congenital short femur and coxa vara. There is external FIG. 4.-Gross shortening of the right thigh associated with congenitalrotation of the limb, the thigh is short and bowed. pseudarthrosis of the femur.

evidence of hip instability and the head of the femurcan usually be palpated within the acetabulum.

Radiographs of the legs show that the affectedfemur is short, and bowed laterally, within an areaof cortical sclerosis on the outer side. The upperend is expanded, the metaphysis is broad, and theepiphyseal centre for the head is late in appearing(Fig. 3). The acetabulum is often shallow. Carefulexamination of the relationship of the upper endof the femur to the acetabulum permits the diagnosisof coxa vara and short femur to be made before theupper bony epiphysis has appeared. The presenceof this centre makes the diagnosis more certain, andreveals the definitive shape of the femur. Defectsof this type may be associated with congenitalabnormalities of the other femur, of a greater orlesser extent.

In this type of deformity growth of the limb isprofoundly depressed, and shortening varies betweenthree inches and six inches at maturity. Even in theabsence of gross congenital abnormalities of the tibiaor fibula, the growth of the leg below the knee isusually depressed. An indication of this can often

be obtained from the early radiographs which showdelay in the appearance of the upper epiphysealcentre of the tibia.

Congenital Pseudarthrosis of the Femur (six cases).This term has been used to describe the grosser typeof femoral shaft defect. The child presents atbirth with a very short thigh, although the develop-ment of muscle is often apparently normal (Fig. 4).There is usually a flexion deformity of the hip, andabduction is limited or absent. There is commonlyan associated congenital defect of the leg or foot.The early radiographs show a short and narrow

femoral shaft, with delay in appearance of the upperand lower femoral epiphyses. In this conditionthe centre for the lower end usually develops duringthe first year, although it may show abnormalities ofshape, usually associated with a genu valgum.As the child grows the femur increases in length,but its upper end attains a level above the aceta-bulum, indicating a progressive coxa vara. Thecentre for the head of the femur is almost alwayspresent, and remains within the acetabulum (Fig. 5).

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CONGENITAL ABNORMALITIES OF THE FEMUR 413

u;. 5. 0;.

FIG. 5 Radiograph of congenital pseudarthrosis of the femur. Theshaft of the femur is displaced upwards, but the head remains in the

acetabulum.

FIG. 6-Congenital pseudarthrosis of the femur before explorationshowing the shaft of the femur opposite the acetabulum. EIs .. 6.

FIG. 7.,The lower part of the figure contains the end of the marrow cavity and 'metaphysis'.) There is a suggestion ofcolumnar arrangement above the cartilage cells and this appears to be a slowly ossifying area.




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FiG. 8.-Radiographs takenthree months after the opera-tion showing the child inFig. 6. The fibular graft canbe seen extending into thehead of the femur which hasnow ossified. There is alarge bar ofnew bone forma-tion between the upper endof the femur and the side

wall of the pelvis.

Thus, although the shaft of the femur appears to bedislocated in relation to the hip joint, there is notrue instability, and the head of the femur and theshaft remain in continuity, but not by bone. Theupper end of the shaft of the femur is often cappedin the older child by a small plate of bone, whichprobably represents the centre of ossification forthe greater trochanter.

Shortening in these patients is due to a combina-tion of coxa vara and a growth defect. By con-trolling the varus deformity it might be possibleto diminish the progress of limb inequality. Onechild was subjected to operative exploration (Fig. 6).The upper end of the femur was found to be com-plete in its cartilaginous form, and no true pseud-arthrosis was present. The upper part of the meta-physis ended by splaying into the cartilage of thefemoral neck, and sections of this region showedthe normal process of endochondral ossification(Fig. 7). The cartilage of the upper femur wasdivided and a wedge removed to abduct the shaftof the femur, and a fibular graft driven across fromthe upper part of the femur into the cartilaginoushead. After this operation the head of the femurrapidly ossified, although para-articular ossificationstill limited hip movement (Fig. 8).

Hypoplasia of the Lower Femoral Epiphysis (onecase). Most congenital defects of the femur affectthe upper end either predominantly or completely,although the delay in the appearance of the secon-dary centre for the lower end indicates that thedisturbance of growth may affect the whole bone.In association with defects of the upper part ofthe femur abnormalities in shape of the lowerfemoral epiphysis may also appear, and may con-tribute to the development of a genu valgum(Fig. 9). Complete absence of the lower femoralepiphysis has been seen in one patient. The con-dition affected both legs, but there was none of theother stigmata of the congenital short femur. It ismore likely that this type of abnormality is relatedto the multiple congenital abnormalities of theepiphyses, rather than the short femur.

Complete Absence of the Femur (one case). Thistype of defect is usually detected at birth and iscommonly bilateral. The thigh is short, and thefemur cannot be palpated. The buttocks arebroad, and the musculature of the gluteal region iswell developed. There are usually associated defor-mities of the limb below the knee, and deformitiesof the upper limb may also be present (Fig. 10).

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CONGENITAL ABNORMALITIES OF THE FEMUR

FIG. 10.-Congenital absence of both femora and of the right forearmwith talipes.

FiG. 9.-The lower femoral epiphysis which is malformed, with agenu varum deformity. The femur is also bowed and short.

Although walking may be a little delayed, evenin the presence of a bilateral defect, mobility isquite good, although instability is marked. Theradiographs of the limb show that the femur iscompletely absent, but the tibia fails to articulatewith the pelvis by some distance. As the childgrows a small ossicle representing the lower endof the femur may appear in the radiographs,emphasizing how resistant the lower end of thebone is to this deformity.

Bilateral Defects (three added cases). There arefive patients in this series with a deformity of bothfemurs. In two of them, one with coxa vara, andone with complete absence of the femur, the defectwas symmetrical. In the other three patients therewas a profound inequality of limb length. Theassociation of two different types of femoral defectin the same patient confirms the view that thesedefects are all variants of a common abnormality(Fig. 11).

FiG. 11.-Bilateral short femur. On the right is a gross coxa vara,on the left a pseudarthrosis. The head of the femur on the left is

just visible in the acetabulum.

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DiscussionAetiology. Careful inquiry into the family

history of these patients, into the history of thepregnancy and that of the birth has failed to findany evidence of a familial factor in this disorder.There is clearly a close association between othercongenital defects of the skeleton, and particularlywith congenital absence of the fibula. Occasionallyboth femora are affected. In the simple coxa vara,however, the defects are usually symmetrical, butin the other type of disturbance the femora tend to beunequally affected. The significance of this obser-vation may not be great, since symmetrical dis-turbance of femoral growth might well pass un-noticed.

In all congenital defects of the femur there is atendency for the upper metaphysis to be the mostseverely affected part of the bone. From the studyof the serial radiographs in these children it appearsthat the primary defect lies in the cartilaginousprimordium of the femur. It is suggested that theabnormality of structure of this tissue is such that inthe minor aberrations it is resistant only to theprocess of endochondral ossification. Such aresistance accounts for the delay in the appearanceof secondary centres of ossification and also for thebroad area of weakness in the upper end of thebone. Under the stress of weight-bearing, orpossibly of simple muscle activity, the relationshipbetween the head of the femur and the neck becomesdisturbed. The development of coxa vara is thusdependent upon a change in the resistance of thecartilage to stress, whilst the failure of growth liesin a resistance to the normal process ofendochondralossification. In the simple coxa vara resistanceto ossification is minimal, and shortening is slight,but in the more severe types of deformity changesin the upper end of the femur, and shortening areclosely allied.The association of the congenital short femur

with other types of congenital abnormalities of theskeleton is more in favour of a primary disturbanceof the cartilaginous framework than a vasculardefect, or an intrauterine fracture. It must beconceded, however, that there is no reason whythe upper metaphysis of the femur is so commonlyinvolved in this type of abnormality.

Prognosis. The disability in congenital defectsof the femur is largely related to the extent of theinequality of limb length. Fixed flexion in theregion of the hip joint, although it increases theapparent shortening of the limb, rarely occasionsany other disturbance. The externally rotatedposition of the limb does not give rise to any func-

tional disability, and there is no evidence that itencourages degenerative changes in the hip.

In the individual child, the outlook dependsprimarily upon the extent of the femoral defect.The shortening of the limb may be predicted withfair accuracy at any age by relating the length of thetwo femora. Thus in a child with a femur onlyhalf as long as the normal one, the shortening asan adult will be somewhere between seven and nineinches. In the presence of coxa vara without otherevidence of the congenital short femur shortening isusually insignificant, and in a simple femoral hypo-plasia will probably not exceed three inches. Wherethe two defects are combined the inequality may be asmuch as six inches and this will be exceeded in thepresence of congenital pseudarthrosis of the femur.

Treatment. The presence of fixed deformity ofthe hip requires treatment in patients with minorfemoral defects to permit a normal gait. In thepresence of severe defects it may occasionally benecessary to permit a prosthesis to be fitted. Coxavara without shortening may require subtrochantericfemoral osteotomy, and the results of this operationare usually good (Le Mesurier, 1948).

Relatively few of the children in this series havebeen subjected to treatment for the limb inequality.Many of them, of course, have not yet reached theage at which definitive treatment is possible. Wherethe shortening amounts to three inches or less, it isclearly amenable to treatment by stapling the knee epi-physes of the longer limb, or by femoral shortening.The number of patients treated in this way is toofew to indicate the value of each of theseprocedures.The more severe disturbances of growth have been

treated by the provision of suitable appliances.In the presence of a well-developed muscular system,these patients manage to carry a high boot or a shoewith a patten with ease. The function of childrenin the extension prosthesis is excellent, but the foottends to be forced into an uncorrectable equinus,thus prejudicing any later attempt to reduce limbinequality. This appliance is also unsightly inthe older patient, and some of these children havebeen treated by Syme's amputation at an earlystage, thus permitting a less obtrusive limb to beworn. The advantages of this procedure must beweighed against the reluctance of the patient and theparents to sacrifice a normal foot.

In the fitting of an artificial limb in the olderpatient a knee flexion piece is rarely possible. Forthis type of patient van Nes (1950) has describeda rotation-plasty which may well be of value. Byfusing the knee and rotating the leg through 180°

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CONGENITAL ABNORMALITIES OF THE FEMUR 417

the ankle is available to activate the knee-flexionpart of the prosthesis.

Summary

A classification of congenital defects of the femurhas been presented, and eight examples of thisdefect have been grouped.The clinical and radiological picture in these

patients, and the growth of the short limb has beendescribed.The nature of the growth disturbance in these

patients has been discussed.

I am most grateful to Mr. J. S. Batchelor, Sir DenisBrowne, Professor J. I. P. James, Mr. G. C. Lloyd-Roberts, Mr. K. I. Nissen and Mr. David Trevor whohave permitted me to examine and report upon patientsunder their care.

REFERENCESGolding, F. C. (1939). Congenital coxa vara and the short femur.

Proc. roy. Soc. Med., 32, 641.(1948). Congenital coxa vara. J. Bone Jt Surg., 30B, 161.

Le Mesurier, A. B. (1948). Developmental coxa vara. Ibid., 30B,595.

Mouchet, A. and Ibos, P. (1928). Considerations sur l'absencecongenitale du f6mur. Rev. Orthoped., 15, 117.

van Nes, C. P. (1950). Rotation-plasty for congenital defects of thefemur. J. Bone Jt Surg., 32B, 12.

Nilsonne, H. (1928). tYber den kongenitalen Femurdefekt. Archiv.orthop. UnfaIl-Chir., 26, 138.

Ring, P. A. (1959). Congenital short femur. Simple femoralhypoplasia. J. Bone Jt Surg., 41B, 73.




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