Fibular hemimelia (FH) is a rare congenital limb anomaly defined by the partial or complete absence of the fibulae. The disease exhibits diverse severity, ranging from mild FH, where the fibulae are hypoplastic, to severe FH, where the fibulae are completely absent. Its incidence ranges from 5.5 to 20 cases/1 million live births. FH tends to affect the right side more often, which is unilateral in ¾ of the cases [1].

The condition has a 2:1 predilection for males and is usually present at birth, with limb length discrepancy and joint deformity, and may be associated with toe abnormalities. However, the case may be accidentally discovered antenatally during an obstetrical ultrasound examination (US) of the fetus [2, 3]. Although the exact cause of fibular hemimelia is not yet defined, several etiological factors have been proposed to help understand why it occurs and how to prevent it among high-risk women. Although most cases are sporadically presented, some suggest a genetic predisposition in the affected limb. Teratogen exposure during antenatal development [4], maternal hyperpyrexia, and environmental toxins early in pregnancy (including smoking) have been linked to FH [5-7].

Abnormality in the vascular supply of the limbs can disrupt limb budding and development [8]. Amniotic bands syndrome during intrauterine life may cause direct compression of the limb, interrupting its growth [9, 10]. There are several classifications of FH based on severity and anatomical involvement to help guide therapeutic strategies, particularly in distinguishing cases eligible for limb lengthening from those requiring prosthetic management (Fig. 1).

First, there was the Achterman and Kalamchi classification (1979), which subclassified cases based on the partial or complete absence of the fibula [10]. Second, Stanitski and Stanitski 2003 relied on the shortened bone to determine whether ankle joints were involved. Finally, Paley's classification in 2016 focused on associated femoral, tibial, and foot deformities [11, 12]. Here, we present a case of a 2-year-old baby boy who presented with FH, proximal femoral focal deficiency, discussing presentation, diagnostic test, and management challenges that stem from parental refusal to treatment.

A 2-year-old male child was brought to the outpatient department of Children Central Hospital, Baghdad, Iraq, with a chief complaint of delayed walking and shortened Rt leg. The parents noticed that their child was significantly behind his peers in achieving independent ambulation while other developmental milestones were within normal limits. As the child aged, there was progressive limb length discrepancy, with the right leg appearing shorter than the left, alongside muscle wasting in the affected limb; no pain, swelling, or gait instability was reported.

The child was the third of five children in the family. The pregnancy was naturally conceived and went uneventfully; the mother reported no exposure to teratogenic agents, infections, or substance abuse, including smoking. The child was delivered vaginally at term with no reported complications.

The family lived in a rural area and had no history of similar cases in the family with unremarkable past medical, surgical histories, and hereditary diseases. The parents did not seek medical advice until the child reached the age of two and remained unable to walk independently.

The examination of the child appeared active and alert with age-appropriate growth parameters. The Rt leg appeared shorter by 3 cm from the left, with mild muscle wasting without tenderness; there were no signs of ankle joint deformity or restricted mobility, nor restricted joint motion, and no foot abnormality. Neurological examination and tendon reflexes were normal too.

The differential diagnosis included congenital conditions, such as fibular or tibial hemimelia, amniotic band syndrome, and proximal femoral focal deficiency. Other possible differential diagnoses were acquired conditions, including post-traumatic or post-infectious growth arrest, bone dysplasia, and neuromuscular disorders [1, 3, 6]. Given the progressive nature of limb length discrepancy, congenital causes seem to fit the case.

Imaging study, including X-rays (Figs. 2 and 3) and CT scans, confirmed the FH diagnosis and defined its severity. The case involved fibular hemimelia, characterized by fibular hypoplasia, a bowed tibia, and limb shortening, combined with proximal femoral focal deficiency (PFFD), in which the femur is shortened, angulated, or bowed, but demonstrates normal mineralization. PFFD tends to associate with FH in 50% of the cases [13, 14]. The ankle joint, foot, and tibia bone were unaffected. The diagnosis was consistent with type II FH with PFFD.

The parents were counselled regarding the variable treatment options, including the following:

The long-term implications of untreated FH were discussed with the family, including challenges imposed on functional mobility, gait abnormality, and psychosocial impacts. After discussing the available options, the parents declined surgical intervention, opting for non-intervention at this stage, and signed an informed refusal acknowledging the potential risks and consequences of their decision.

FH is a rare congenital condition; despite its rarity, it is the most frequently reported type of long bone deformity. Table 1 lists some of the cases reported in the last decade.

Diagnosing FH is mainly clinical and confirmed by imaging studies. The clinical picture is provided as follows:

The affected limb can be shortened with a discrepancy in limb length.

Fibular hemimelia is a rare complex anomaly that requires a multidisciplinary approach. Earlier diagnosis and personalized management are key factors to improve FH outcomes as they enable timely intervention. At the same time, a multidisciplinary approach enhances mobility and reduces psychosocial impact. Advancements in surgical techniques and prostheses continue to improve the function of limbs, gait stability, and patients' quality of life. Further research is warranted to refine treatment selection, which can improve the patient’s quality of life and assess the long-term outcome for this rare limb anomaly.