Case of the Week #602

Petra Turnova (1); Igor Yarchuk (2)
(1) Slovakia; (2) United States

Posting Dates: Mar 31, 2024 - Apr 14, 2024

A 24-year-old primigravida with non-contributory medical history presented at 11 weeks and 4 days of pregnancy. Ultrasound revealed the following findings.

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Answer

We present a case of bilateral femoral deficiency with unilateral fibular hemimelia.

The ultrasound demonstrated an absent femur with fibular hemimelia and clubfoot on the right side, and a hypoplastic femur with normal fibula and tibia on the left side. The parents decided to continue the pregnancy and at 16 weeks, an abnormal facial profile was suspected. Our diagnosis of bilateral femoral deficiency with unilateral fibular hemimelia was confirmed at birth, and the facial profile was considered normal. Our differential diagnosis also included femoral hypoplasia with unusual face. The child is doing well at 6 months of age.

Discussion

Proximal femoral focal deficiency is a rare congenital syndrome that is part of a spectrum of congenital anomalies affecting the femur, and known more broadly as congenital femoral deficiency. Its incidence is about 0.12 per 10,000 births [1]. Most cases are unilateral, and bilateral occurrence is rare [2-4]. Associated abnormalities occur in approximately 60% cases and include fibular hemimelia, spinal deformities, clubfoot, absence of cruciate ligaments, and oligodactyly [3,4].

The exact cause of proximal femoral focal deficiency remains unknown. It is usually sporadic though some cases may have a genetic basis [5]. Others may result from teratogens such as thalidomide, radiation exposure, viral infections, and focal ischemia [2]. Additionally, the incidence of fetal structural defects, including limb deficiencies, due to maternal diabetes is higher than that of non-diabetic pregnancies [6]. Proximal femoral focal deficiency is usually not associated with chromosome abnormalities and patients have normal intelligence [7].

Proximal femoral focal deficiency is thought to occur due to a failure of development of the subtrochanteric portion of the femoral shaft [7]. Embryogenesis of the femur involves a complex interaction of growth factors during development of the subtrochanteric portion of the femoral shaft between 4 to 8 weeks post-fertilization. Mesenchymal cells play a key role in integrating positional information received from various axes during limb bud formation [2].

Prenatal ultrasound can be used to diagnose proximal femoral focal deficiency, though few cases are reported in the literature [8]. In a unilateral case, the ratio of femoral length discrepancy can vary by approximately 50-60% [7,9,10]. The diagnosis is typically made in the second trimester as discrepancies between the femoral measurements in the first trimester may only be a few millimeters. In bilateral cases, this asymmetry may not be present [11] and carefully evaluating the fetal skeleton, face, chest, spine and skull to exclude other conditions is critical [8]. Additionally, it is important to exclude sources of error in measuring the femur, which may include shadowing from another bony fetal segment or obtaining the measurement on an oblique plane. A scan must clearly visualize both ends of the ossified metaphysis with the probe perpendicular to the longest axis of the femur [8,9].

The Differential diagnosis includes femoral hypoplasia with unusual facies syndrome, femur–fibula–ulna syndrome, limb-pelvis hypoplasia/aplasia syndrome, [8] as well as thanatophoric dysplasia, campomelic syndrome, achondroplasia, achondrogenesis, chondroectodermal dysplasia and osteogenesis imperfecta [8,9]. Femoral hypoplasia with unusual facies syndrome often presents with bilateral femoral hypoplasia, and facial dysmorphism characterized by short nose, long philtrum, thin upper lip, small lower jaw, and cleft palate [12]. Bones in fetuses with proximal femoral focal deficiency do not demonstrate demineralization.

Classification of proximal femoral focal deficiency is essential for prognosis and treatment. The Aitken classification system is commonly used, distinguishing between Type A, B, C, and D based on features such as shortening of the femur, the presence of the femoral head, and condition of the acetabulum [9].

Proximal femoral focal deficiency can lead to abnormal gait, impaired growth, psychosocial and cosmetic implications. The treatment is typically directed at improving limb function and options vary depending on the severity of the deficiency and the individual needs of the patient. For patients with a predicted limb length discrepancy of >20cm, options often include surgery to facilitate implantation of a prothesis. In patients with a predicted length discrepancy of <20cm, surgical procedures to lengthen the limb can help improve mobility and function. In some cases, surgical reconstruction of the hip joint or acetabulum may be required to improve hip stability and function [13].

References

[1]   Syvänen J, Helenius I, Koskimies-Virta E, et al. Hospital admissions and surgical treatment of children with lower-limb deficiency in Finland. Scand J Surg. 2019 Dec;108(4):352-360.
[2]   Panting AL, Williams PF. Proximal femoral focal deficiency. J Bone Joint Surg Br. 1978 Feb;60(1):46-52.
[3]   Koman LA, Meyer LC, Warren FH. Proximal femoral focal deficiency: a 50-year experience. Dev Med Child Neurol. 1982 Jun;24(3):344-55.
[4]   Hillmann JS, Mesgarzadeh M, Revesz G, et al. Proximal femoral focal deficiency: radiologic analysis of 49 cases. Radiology. 1987 Dec;165(3):769-73.
[5]   Sen Gupta DK, Gupta SK. Familial bilateral proximal femoral focal deficiency. Report of a kindred. J Bone Joint Surg Am. 1984 Dec;66(9):1470-2.
[6]   Hadi HA, A Wade A. Prenatal diagnosis of unilateral proximal femoral focal deficiency in diabetic pregnancy: a case report. Am J Perinatol. 1993 Jul;10(4):285-7.
[7]   Doğer E, Köpük SY, Cakıroğlu Y, et al. Unilateral isolated proximal femoral focal deficiency. Case Rep Obstet Gynecol. 2013;2013:637904.
[8]   D'Ambrosio V, Pasquali G, Squarcella A, et al. Prenatal diagnosis of proximal focal femoral deficiency: Literature review of prenatal sonographic findings. J Clin Ultrasound. 2016 May;44(4):252-9.
[9]   Jeanty P, Kleinman G. Proximal femoral focal deficiency. J Ultrasound Med. 1989 Nov;8(11):639-42.
[10] Gerscovich EO, Sekhon S, Loehfelm TW, et al. Fetal ultrasound: Early diagnosis and natural evolution of proximal femoral focal deficiency. J Ultrason. 2017 Dec; 17(71): 294–298.
[11] Gonçalves LF, De Luca GR, Vitorello DA, et al. Prenatal diagnosis of bilateral proximal femoral hipoplasia. Ultrasound Obstet Gynecol. 1996 Aug;8(2):127-30.
[12] Paladini D, Maruotti GM, Sglavo G, Penner I, et al. Diagnosis of femoral hypoplasia-unusual facies syndrome in the fetus. Ultrasound Obstet Gynecol. 2007 Sep;30(3):354-8.
[13] Uduma FU, Dim EM, Njeze NR. Proximal femoral focal deficiency – a rare congenital entity: two case reports and a review of the literature. J Med Case Rep. 2020 Feb 5;14(1):27.