Reconstructive surgery to preserve ankle function in a 5-year-old girl with bilobed distal tibia in an unclassified case of tibial hemimelia: a case report

Abstract

Background

Tibial hemimelia is an uncommon congenital abnormality ranging from a solitary skeletal deformity to associations with other syndromes. Despite Paley et al.’s detailed classification of tibial hemimelia, some unique sporadic cases still do not fit within this system. In 2021, Chong et al. proposed the most recent surgical approach based on the Paley classification, which inspired cases such as ours.

Case presentation

This case study presents a novel case of tibial hemimelia characterized by a bilobed distal tibia, a shortened first ray, and an equinovarus deformity in a 5-year-old Iranian (Lur) girl. She experienced pain, limping, and cosmetic concerns. The surgical procedures performed for preservation are thoroughly described and discussed.

Conclusion

This case has been identified as a new variant of Paley type 2. A staged approach to reconstructive surgery was advocated to ensure the preservation of ankle function and to prevent extreme procedures such as amputation. The most recent follow-up demonstrated promising results.

Highlights

• Tibial hemimelia is an extremely rare congenital abnormality that can result in a wide range of manifestations.

• The Paley classification is considered the most comprehensive system for describing and classifying this spectrum.

• We presented and managed a novel case of unilateral tibial hemimelia characterized by distal tibial bifurcation through reconstructive surgery for the first time.

• We suppose that our case is a new subtype of Paley type 2.

Background

Tibial hemimelia (TH) is a rare congenital malformation affecting approximately 1 in every 1,000,000 live births [1]. This spectrum of abnormalities is primarily characterized by tibial malformations, with approximately two-thirds of cases also presenting with other associated anomalies [2]. The tibia can be underdeveloped or completely missing on one or both sides, whereas the fibula usually remains unaffected. In addition, other skeletal duplications or deficiencies, as well as nonskeletal syndromic manifestations, may be present. A common issue is the deficiency of the first ray in the foot. Ankle malformations, often resulting in varus deformities, are typical, and unilateral cases frequently lead to leg length discrepancies (LLDs) [3,4,5]. TH is associated with various syndromes, including Werner’s syndrome, Langer–Giedion syndrome, Gollop–Wolfgang complex, and CHARGE syndrome [6,7,8,9].

While the Paley classification is widely regarded as the most comprehensive system for categorizing TH, occasional unconventional cases deviating from this classification highlight the limitations of scientific understanding in this area [10, 11]. Management of this condition continues to be debated. Although Chong et al. [4] provided valuable treatment strategies, exceptional cases still require personalized approaches [3].

The present study explores a unique case of TH featuring a bilobed distal tibia, along with a shortened first ray and a discrepancy in leg length. This case might represent a new variant of TH that does not fit into any existing categories. In addition, the study examines the effectiveness of staged reconstructive surgery in maintaining ankle function. This case report has been prepared following the CAse REport (CARE) 2013 guidelines [12].

Case presentation

A 5-year-old Iranian (Lur) girl was admitted with a congenital deformity affecting her right lower limb. Prior to the study, her family provided consent for the publication of the data. She is the third living child of a nonconsanguineous couple (G4 P3 L3 A1). She was delivered via cesarean section at 38 weeks of gestation, weighed 2900 g, and did not require hospitalization during the neonatal period. The mother did not have any reported history of infections, diabetes, using harmful medications, smoking, or alcohol consumption during her pregnancy. However, she did experience a miscarriage during her first pregnancy.

Clinical findings and diagnostic assessment

The child was brought to our clinic by her parents owing to persistent limping and pain that had begun 2 years prior. During the examination, we observed distal leg widening, overt bone prominence in the medial supramalleolar, deformity in the first ray, hindfoot varus, and flatfoot in the right foot (Fig. 1). The ankle joint showed a notable limitation in its range of motion, specifically in dorsiflexion, plantar flexion, inversion, and eversion. The patient’s gait was affected by noticeable limb length discrepancy (LLD). Aside from these findings, the review of systems showed normal results. Laboratory tests, including vitamin D, calcium, and phosphorus serum levels, were all within normal ranges. X-rays revealed a bifurcation in the distal tibia and bowing of the fibula, attributed to tibial shortening (Fig. 2). All data collected pertain to the longitudinal (radial) congenital deformity recognized as TH.

Fig. 1 

Distal leg widening, overt medial bone prominence, a deformity in the first ray, and hindfoot varus in the right foot

Fig. 2 

Preoperative upright X-ray of the distal lower extremity showing bilobed distal tibia on the right side and a long, bowed fibula

Surgical technique

The patient underwent a three-stage surgery under general anesthesia. The first phase was executed with the patient in a supine position, utilizing an anterior approach that necessitated the meticulous exposure and release of the distal tibiofibular joint, including a thorough examination of the medial and lateral physes (Fig. 3A). Throughout the surgical procedure, the assessment of the position and dimensions of the lateral component, in conjunction with the histological evaluation of the physis relative to the medial section of the distal tibia, prompted the decision to preserve the lateral component while excising the medial one. A vertical osteotomy was conducted on the medial physis of the bifurcated tibia and the supramalleolar region, allowing for careful excision of this portion (Fig. 3B). Following the transverse osteotomy, the lateral physis was turned toward the tibial axis (Fig. 3C). Subsequently, the proximal and distal parts of the tibia were fixed using a size three intramedullary pin. Foot centralization was performed under C-arm guidance to address potential angular deformities (Fig. 4). Ultimately, the patient was discharged with a long leg cast.

Fig. 3 

A Surgical procedure demonstrating thorough exposure and release of the distal parts of the tibia and fibula in the right leg through an anterior approach (arrow shows the osteotomy line), (B) excision of the medial physis and the supramalleolar region by vertical osteotomy (straight arrow indicates the vertical osteotomy line, while curved arrow represents the centralization procedure toward the tibial axis), (C) simultaneous transverse osteotomy and centralization through the tibial axis, with fixation of the distal part using an intramedullary pin (blue arrow)

Fig. 4 

X-ray images from a C-arm machine showing a well-placed and fixed distal tibia (A lateral view, B anteroposterior view)

The intramedullary pin was extracted at a follow-up appointment 12 weeks later. However, 1 year subsequent to this, notably, the varus deformity had not been sufficiently addressed, accompanied by an increase in fibular bowing attributed to fibular overgrowth. Consequently, the decision was made to proceed with fibular epiphysiodesis, carried out in a subsequent surgical procedure via a lateral approach under general anesthesia, allowing for exposure of the distal fibula and implementing an eight-plate epiphysiodesis (Fig. 5). However, after 4 months, the eight-plate failed, necessitating a fibular osteotomy and cannulated intramedullary screw epiphysiodesis (Fig. 6).

Fig. 5 

X-ray images (A lateral view, B anteroposterior view) showing eight-plate implantation to correct varus foot deformity caused by fibular overgrowth

Fig. 6 

Postoperative X-ray (A anteroposterior view, B lateral view) showing the replacement of the eight-plate epiphysiodesis with an intramedullary screw. A fibular osteotomy was performed, and the patient was discharged with a short leg cast

Figure 7 shows the last radiographic follow-up two years after the initial ankle reconstruction surgery. The most recent follow-up revealed a reduction in equinovarus deformity and limping, pain alleviation, and a notable increase in ankle range of motion (Fig. 8). The patient will continue to be monitored for potential LLD.

Fig. 7 

Follow-up X-ray image (right: AP, left: Lateral) taken two years after the initial reconstructive surgery, showing fibular bowing due to overgrowth is corrected, tibial plafond and tibiotalar joint is intact, angular deformity is proportionately corrected

Fig. 8 

Photographs displaying the improved functionality of the right ankle two years after the initial surgery (A: standing upright, B: plantar flexion, C: foot dorsiflexion)

Discussion

To the best of our knowledge, there have been no previous reports of a case featuring unilateral bilobed distal tibia with an intact fibula, first-ray shortening, and equinovarus foot deformity without any other skeletal or nonskeletal anomalies. A closely related case to the current study was documented by Shah et al. in 2016 [10] involving bilateral TH. In this case, an 18-month-old boy exhibited splitting of both hands and his left foot, a complete absence of the left tibia, and a hypoplastic tibia on the right side, which had a bifid distal part and a non-ossified end. The fibula was normal on both sides. Similar to the present situation, none of the existing classifications can fully explain this case [4, 5, 13]. In contrast, this case involved unilateral tibial hypoplasia with a bilobed distal portion, and shortened first ray. LLD progressed gradually over time.

The patient was first evaluated and diagnosed at the age of 2 years. At that time, it was decided to adopt a conservative approach by observing and monitoring her condition. During the 3-year follow-up period, staged reconstructive surgery was considered owing to worsening pain, limping, functional limitations, and cosmetic concerns. Regrettably, no validated guidelines for managing this unique case are available in literature. In the most recent update of the Paley classification, Chong et al. suggested various surgical approaches [4]. Despite the absence of an exact classification that aligns with the studied case, examining existing classifications and surgical alternatives motivated us to delve deeper into our situation. This study explored the potential of categorizing it as a new subtype within the type 2 Paley framework.

Surgical options are significantly influenced by the presence of the tibia, quadriceps function, ankle function, varus–valgus deformity, and LLD. For instance, in the absence of the tibia (Paley type 5), amputation or knee disarticulation is prioritized. The choice between acute and gradual correction leads to different options. A circular external fixator is recommended for Paley types 2–5, depending on the mechanism and severity of the deficiencies. In cases of Paley type 1, often presenting bilaterally on the basis of the individual patient’s circumstances, temporary proximal tibial epiphysiodesis may be performed, with or without comprising fibular epiphysiodesis. Since LLD in TH typically remains consistent over time, estimating the predicted length discrepancy provides parents with valuable information to make informed decisions regarding further interventions. On the one hand, ipsilateral leg lengthening is frequently used to correct LLD, but on the other, contralateral tibial and fibular epiphysiodesis may be suitable for other cases [4, 14, 15].

In the present scenario, the choice of which physis to remove was a challenging task. Preoperative magnetic resonance imaging (MRI) revealed that the lateral physis was more suitable, a finding confirmed by intraoperative evidence. Evidently, after 6 months, the varus deformity had not been corrected appropriately due to fibular overgrowth. Consequently, this study proceeded with an eight-plate epiphysiodesis of the distal fibula. Despite the growing use of eight-plates for correcting angular deformities in the knee and ankle [16, 17], often yielding positive results with minimal complications [18], the eight-plate proved ineffective 4 months later in this particular instance. We decided to replace it with an intramedullary screw, which has shown acceptable outcomes. Although fibular overgrowth was managed, we anticipate continued progression of LLD owing to tibial hypoplasia and ipsilateral fibular epiphysiodesis. Thus, it was decided to keep the studied patient under surveillance for a period of at least 5 years.

Limitations

The present study encountered several challenges in defining and categorizing the case under study and developing an appropriate treatment protocol. This case is a unique example of TH, which has not been classified before, even within the Paley system. However, this investigation did not examine the genetic aspects of this case and recommends that future studies explore these components. Regrettably, the child’s medical records did not provide any documented evidence of an ankle deformity at birth. Nevertheless, the parents reported observing an unusual ankle shape when the child was 6 months old. After ruling out other possible causes, including trauma, the researchers categorized it as a congenital deformity. A follow-up study was conducted over 2 years; however, pursuing further follow-ups for a more thorough assessment may be advantageous. While this study gathered follow-up data from 3 years prior to the reconstructive surgeries, preoperative radiographs taken prior to removing the eight-plate are unavailable.

Conclusion

The case under study represents a novel subtype of Paley type 2, characterized by a dysplastic tibia with intact proximal and shaft regions. The distal tibia displays a bilobed (bifurcated) structure, accompanied by a varus deformity of the foot. In this study, we proposed a staged reconstructive surgical approach to preserve ankle functionality and minimize the chances of excessive treatment or the need for amputation. This study resected the excessive physis to maintain ankle functionality and improve range of motion. In addition, ipsilateral fibular epiphysiodesis was performed to decrease varus ankle deformity due to fibular overgrowth. The last follow-up showed promising outcomes.