Etiology of the bifid (double) femoral head, with prior history of developmental dysplasia of the hip

doi:10.4236/crcm.2013.25085

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Vol.2, No.5, 318-321 (2013) Case Reports in Clinical Medicine

http://dx.doi.org/10.4236/crcm.2013.25085

Etiology of the bifid (double) femoral head, with prior

history of developmental dysplasia of the hip

Leonard P. Seimon*, Christine Kohler-Ekstrand, Howard D. Dorfman

Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, USA;

*Corresponding Author: [email protected]

Received 23 April 2013; revised 26 May 2013; accepted 3 June 2013

cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

Our patient presented with a double femoral

head, that is, two separate heads with individual

epiphyses, but a single contiguous metaphysis.

Two similar cases had been described in the

literature. The only common feature in these three

cases is that they had open reduction for De-

velopmental Dysplasia of the Hip (DDH) through

an anterior approach. No other pathology was

detected in these patients. A rabbit model was

created in which the cartilaginous anlage of the

rabbit femoral head was surgically split. After 2 -

4 weeks a bifid femoral head developed, mim-

icking that described in the literature. We sug-

gest that inadvertent damage to the femoral

head during surgery for DDH may in fact lead to

the development of a bifid femoral head. Prior

history of DDH should be considered when the

isolated bifid femoral head is identified.

Keywords: Bifid; Femoral Head; Etiology; Rabbit

Study

1. INTRODUCTION

Bifid femoral heads are an unusual and puzzling de-

formity. While the etiology of the deformity is unknown,

Ferguson [1], Rossman [2] and Salter [3] proposed that

since increased pressure or forced positions contribute to

the development of avascular necrosis of the hip, a tight

iliopsoas tendon, or focal necrosis through forced posi-

tions, may be responsible for the development of a bifid

femoral head. However, if a tight iliopsoas muscle is the

major factor in producing a bifid femoral head then the

condition should be common in the cerebral palsy popu-

lation. Yet it has never been described in those patients.

Variants of bifid femoral heads are described in the liter-

arure, such as seen in Perthe’s Disease and Meyer Dys-

plasia, and in a recent article by Osuji, et al. [4].

Two patients with bifid femoral heads, with prior his-

tory of surgical treatment for D.D.H. have been de-

scribed in the literature [1,2]. Ours is the third similar

case to be reported.

2. CASE REPORT

An 8-year-old girl presented for evaluation of left hip

pain. She felt this at times when walking, and also on

turning over in bed. Open reduction though an anterior

approach was performed for D.D.H. as an infant. She

walked with a mild limp, with the limb in neutral align-

ment, but ran rapidly with her limb internally rotated.

Radiographs revealed a split femoral head with a larger

anterior segment and a smaller posteromedial segment

(Figures 1 and 2). The smaller femoral head was con-

tained in the acetabulum with the hip in neutral align-

ment, and the larger head with the hip internally rotated.

This explained why she felt pain when walking, as the

smaller head was in the acetabulum. She internally ro-

tated her limb when running and had no pain, as the lar-

ger head was in the acetabulum. Intraoperatively the ili-

opsoas tendon was not significantly tight, and the labrum

was not deformed. The smaller head was excised. The

larger head was reduced by internal rotation into its most

optimal position in the acetabulum, and a derotational

osteotomy was performed with internal fixation (Figure

3). She made excellent progress. She had mild residual

shortening of the limb. She participated in sporting ac-

tivities and at 8-year follow-up, she was a cheerleader.

3. OBJECTIVE

The common thread in our patient, and the two prior

cases, is surgery at a very young age for developmental

dysplasia of the hip. We propose that the deformity may

be related to damage to the ossific nucleus of the femoral

head during surgery for DDH. We therefore devised an

L. P. Seimon et al. / Case Reports in Clinical Medici ne 2 (2013) 318-321 319

Figure 1. A-p view. Smaller head articulates in acetabulum.

Figure 2. Frog-lateral view.

Figure 3. Immediate post-excision of the smaller head, reduc-

tion of larger head and rotation osteotomy.

animal model to determine the effect of splitting the os-

sific nucleus, with a simple incision, on development of

the femoral head.

4. METHODS

Approval for the following study was received from

IRB.

Eight New Zealand White (NZW) rabbits underwent

bisection of the right femoral ossific nucleus at 13 or 15

days of age. At this ag e, the 5 mm rabbit femoral head is

visible and surgical technique is thus reproducible [5].

Through a medial approach the right cartilaginous femo-

ral head was exposed and bisected under direct visualize-

tion, and the joint capsu le and wound closed. Th e left hip

was used as the control. Radiographs of both hips were

obtained at 2 - 4 weeks intervals until the rabbits were

euthanized at maturity, around 4 months. Both femoral

heads and both respective acetabulae were resected and

inspecte d grossly and histolog i c ally.

5. RESULTS

Two anesthetic deaths reduced the sample number to

six rabbits. One had to be sacrificed before maturity be-

cause of illness. In three of the rabbits radiographs dem-

onstrated double femoral heads, and in all three the sec-

ondary femoral head articulated with a pseudo-aceta-

bulum (Figure 4). In the remaining three rabbits the op-

erated-on femoral head was normal in one, demonstrated

an elongated neck in the second and had an SCFE-like

pattern in the third. The femoral heads with their respec-

tive acetabulae were dissected. A thick joint capsule was

present around the bifid femoral heads, with a flexion

contracture in the double-headed femurs, but no tight

structures were visible.

Gross sections of each specimen revealed two truly bi-

fid femoral heads (Figure 5), with each head lined with

cartilage and separate epiphyses (Figure 6). The third

double head, suspected by radiographic evidence, was

determined to be only a spicule of bone without any car-

tilaginous surface.

Figure 4. Two separate femoral heads with respective acetabuli

in rabbit specimen.

L. P. Seimon et al. / Case Reports in Clinical Medici ne 2 (2013) 318-321

320

Figure 5. Gross specimen of double femoral heads and aceta-

buli.

Figure 6. Gross section: two femoral heads with articular car-

tilage, single physis.

Histology showed all controls to have hemispherical

heads. Two bifid femoral heads were present (Figure 7).

One of these specimens showed a couple of dead bone

spicules at the cleft site, however this was due to remod-

eling and not consistent with osteonecrosis. Another spe-

cimen showed one head with a second head-like struc-

ture, which was actually composed of compact bone with-

out a physis. The fourth specimen demonstracted an

elongated epiphysis without any scar tissue. The fifth

specimen had a widened acetabulum and the last speci-

men had irregularities in the piriformis fossa and femoral

neck with abundant scar tissue.

6. DISCUSSION

Bifurcation of the femoral head is a rare entity, with

few reports in the literature [1,2,4]. Our patient is the

third to be reported who had prior surgery for DDH. In

order to evaluate the hypothesis that surgical trauma

during surgery for DDH may be related to the develop-

Figure 7. Histology of two separate femoral heads, single phy-

sis.

ment of a bifid femoral head, an animal model was cre-

ated. A bifid femoral head was demonstrated in 2 of 6

rabbits who underwent surgical bisection of the femoral

head. Another specimen was similar on radiographic

findings, howeve r the histology revealed only on e femo-

ral head with a compact bone spicule similar to an exo-

stosis.

The question remains: why did not all of the femoral

heads become bifid post-surgery? The specimens without

pathology in the femoral head may have been caused by

surgical error. Additionally, the ossific nucleus may not

have formed in 13 - 15 days since it has been shown by

Heikel [6] that the rabbit ossific nucleus presents in only

43 of 57 animals at 6 - 10 days. Alternatively, the surgi-

cal insult may have healed and remodeled.

7. CONCLUSIONS

Bifid femoral heads can be induced by splitting the

ossific nucleus in immature rabbits. This should be kept

in mind when performing surgery around the ossific nu-

cleus in immature patients. Focal necrosis and tight sur-

rounding structures are not the etiology of the true bifid

femoral head.

In children in whom a bifid femoral head is id entified,

a history of surgery at a young age, for DDH, should be

sought.

REFERENCES

[1] Ferguson, A. (1981) Orthopaedic surgery in infancy and

childhood. 5th Edition, Williams and Wilkins, Baltimore,

292-294.

[2] Rossman, M. and Jequier, S. (1982) The double-headed

femur. Clinical Orthopaedics and Related Research, 162,

170-172.

[3] Salter, R., Kostuik, J. and Dallas, S. (1969) Avascular

L. P. Seimon et al. / Case Reports in Clinical Medici ne 2 (2013) 318-321

321

necrosis of the femoral head as a complication of the dis-

location of the hip in young children. A clinical and ex-

perimental investigation. Canadian Journal of Surgery,

12, 44.

[4] Rudicel, S., Lee, K. and Pelker, R. (1985) Dimensions of

the rabbit femur during growth. American Journal of Vet-

erinary Research, 46, 289-299.

[5] Heikel, H. (1960) On ossification and growth of certain

bones of the rabbit; with a comparison of the skeletal age

in the rabbit and in man. Acta Orthopaedica Scandi-

navica, 39, 171-185.

[6] Osuji, C.K., Chafik, D. and Moseley, C.F. (2009) Unilat-

eral proximal bifurcation of the femur. Journal of Pediat-

ric Orthopaedics, 29, 695-697.

doi:10.1097/BPO.0b013e3181b76985