Congenital fibular hemimelia (CFH) is a common congenital limb deficiency but still classified as a rare disease, with an incidence of approximately 1:135,000 to 1:5,000 in live births. Clinically, it manifests as partial or complete absence of the fibula, accompanied by shortening and bowing of the tibia, ball-and-socket or dish-shaped ankle joint, and tarsal anomalies (1). During growth and development, patients often exhibit progressive valgus deformity of the foot and lower limb length discrepancy, which severely impacts their quality of life (2). The main treatment goals for CFH patients are limb length equalization, correction of foot and ankle deformities, and gait improvement.

The pathological basis of the series of deformities caused by CFH is the replacement of the fibula by a fibrous cartilaginous band. Due to the tethering effect of this band, tibial development is delayed, leading to anteromedial bowing of the tibia. The absence of the lateral malleolus and the contracture and tethering of the peroneal muscles and Achilles tendon result in valgus deformity of the foot (1, 3). Therefore, early surgical removal of the fibular fibrous band and release of contracted Achilles tendon and peroneal tendons can effectively prevent further aggravation of tibial and foot and ankle deformities in CFH patients. Achieving ankle joint stability through foot and ankle reconstructive surgery is often the first step in the surgical treatment of CFH.

Despite continuous advancements in surgical techniques for CFH (4, 5), patients who originally required amputation or prosthesis can now avoid amputation and achieve better function. However, these surgical methods inevitably require initial soft tissue release or ankle joint reconstruction to obtain a stable ankle joint (6). Consequently, some CFH patients need to undergo multiple surgeries, imposing significant pain and burden on the patients and their families.

Herein, we report an 8-year-old girl with CFH characterized by complete absence of the fibula. Who achieved a stable ankle after early corrective treatment, allowing the patient to undergo only limb length discrepancy correction without soft tissue release or reconstructive surgery for ankle. This approach not only significantly reduced the complexity of the surgery but also minimized the trauma and burden on the patient. To our knowledge, this is the first reported case of CFH in which a stable ankle was achieved through early conservative treatment, thereby avoiding ankle reconstruction surgery. We believe that the early intervention combined with surgical treatment in this case will provide new insights into CFH treatment strategies.

The 8-year-and-6-month-old child, born in the economically underdeveloped southwestern region of China, is of Han ethnicity and has no family history of genetic disorders. After birth, the parents found that the child's right foot was obviously valgus, so the parents used a splint to fix the child's right ankle joint in a functional position at home for 3 months. Subsequently, the splint was removed during the day to mobilize the ankle joint, and the splint was used to fix the ankle joint at night. After 6 months of this treatment, the right foot of the patient exhibited a normal appearance. By the age of 18 months, the child demonstrated normal ambulation without observable gait abnormalities. However, as the child grew and developed, the leg length discrepancy became increasingly apparent, resulting in a limping gait, and the patient was subsequently admitted via outpatient consultation.

CFH is the most common congenital longitudinal deficiency of the lower limb, predominantly unilateral, with a higher incidence in males than in females (10). The exact etiology of CFH remains unclear. The widely accepted theory is embryonic vascular dysplasia: during early embryonic development (5–7 weeks of gestation), the limb vasculature begins to develop progressively. The absence of the anterior tibial artery and fibular artery leads to abnormal development of the fibular side of the limb (11). In addition to partial or complete congenital absence of the fibula, CFH often presents with five major deformities (12–14): (1)

Tibial Deformity: Due to congenital tibial dysplasia, the affected tibia usually bows anteromedially during ambulation because of uneven load distribution between the lower limbs.

In the past, the treatment of CFH was mainly amputation and postoperative artificial limb. However, with the development of pediatric orthopedic surgery, the emergence of surgical techniques such as tibial centralization, soft tissue release, and limb lengthening has provided great help for the treatment of CFH. Considering the patient's history of congenital talipes equinovalgus, her condition aligns with Paley type IIIB. According to Paley's reconstructive methods, type III patients should first correct foot and ankle deformities to achieve ankle joint stability before performing tibial osteotomy and lengthening.

Paley's method involves using subtalar joint osteotomy and tibial osteotomy for the correction of ankle deformities in children. Other methods to achieve ankle joint stability include: I. H. Thomas (22) applied the Gruca procedure in children with distal fibular aplasia, performing reconstructive osteotomy of the ankle to maintain balance and prevent secondary valgus deformity during development. Wiltze (23) utilized osteotomy to correct ankle valgus deformity without causing abnormal medial malleolar prominence or limb shortening, recommending osteotomy be performed after skeletal maturity. Catagni et al. (24) reported 18 cases of complete fibular aplasia, with 2 cases ultimately undergoing ankle arthrodesis, showing favorable long-term follow-up outcomes. Additionally, Bishay et al. combined fibular band resection, soft tissue release, and Ilizarov technique to stabilize the ankle joint (25). In this case, the family found that the child's right foot was obviously valgus since birth. The parents applied homemade splints to immobilize the right ankle in a functional position for 6 consecutive months. After 6 months of treatment, the external appearance of the right foot normalized. The patient achieved independent ambulation at 18 months of age. As the patient grew up, the bilateral lower limb length discrepancy progressively worsened, prompting the current consultation. Although the fibula was completely absent, the patient presented with functional ambulation capacity (FAC 5) at the time of admission, with a 40 cm step length, a negative anterior drawer test, and a normal one-leg standing test. Therefore, the affected ankle joint was considered to be in a stable state and no ankle reconstruction surgery was needed. Therefore, we chose to achieve limb equilength by tibial osteotomy and lengthening using Ilizarov technique. Latest follow-up results indicate satisfactory lengthening of the right tibia in the patient.

Although classification systems and surgical techniques vary, the ultimate objective is to achieve stable ankle and knee joints, as well as well-aligned and equal-length lower limbs in patients. Normal ambulation is the ultimate goal of CFH treatment and management. To the best of our knowledge, this is the first reported case of CFH with complete absence of fibula in which ankle stability can be maintained after prior conservative treatment. This also suggests that early detection and early conservative treatment for ankle dysplasia may be able to reduce the pain associated with multiple surgeries experienced by the patients. However, as this is a single-case report with inherent limitations, outcomes may vary among CFH patients. The efficacy and feasibility of early conservative management require validation through multicenter, large-sample, prospective clinical randomized controlled trials. We believe this report not only emphasizes the importance of early screening and conservative management for CFH but also provides novel therapeutic insights for CFH treatment.