Proximal femur alloprosthesis in a pediatric patient with Ewing sarcoma: Case report

Abstract

Introduction and importance

Ewing sarcoma is a primary malignant tumor of bone and, to a lesser extent, soft tissues.

Within oncological management, surgery with extensive local control and reconstruction is the most accepted option, however, the size, extension of the tumor, the age of the patient and distant involvement can make this option difficult.

Case presentation

We present a clinical case of a 3-year-old infant with Ewing sarcoma in the proximal femur, who was managed with wide resection of the tumor plus proximal humerus allograft, which acted as a proximal femur for 2 years and then presented joint failure due to what was done was the application of a cemented stem over the remnant of the allograft to save the hip.

Clinical discussion

In the presented case, similar to the report by Zoccali a malignant tumor in the proximal femur of a pediatric patient is documented. In these cases, where the distal femoral growth plate is disease-free, a reconstruction technique preserving the growth plate is proposed.

Conclusion

The technique of proximal femoral allograft with a proximal humeral graft is an acceptable reconstructive treatment alternative for young patients with Ewing sarcoma, especially when conventional treatment options are limited. This approach helps avoid limb-threatening surgeries such as amputation or rotationplasty, providing a viable and functional solution for limb salvage in these cases.

Highlights

• •Ewing's sarcoma is a primary malignant tumor of the bone and to a lesser extent of soft tissues.
• •The most common location is in the diaphysis or meta-diaphyseal segments of long bones
• •From a pathophysiological perspective, a high percentage of cases exhibit a chromosomal change in the genetic locus of cellular DNA.
• •Diagnosis is based on the analysis of clinical findings, with the presence of a painful mass being the most common symptom.
• •Within oncological management, wide local control surgery and reconstruction is the most accepted option, however, the size, tumor extension, the patient's age and remote involvement can make this option difficult.

1. Introduction

Ewing sarcoma is the second most common primary malignant bone tumor in the pediatric population, following osteosarcoma [1,2].

Eighty percent of cases occur in individuals under 20 years of age, with rare instances in those under 5 years and over 30 years. The tumor is more prevalent between ages 11–12 in girls and 15–16 in boys, with a male-to-female ratio of 1:6, and it is exceptionally rare in the black population [3].

The approximate annual incidence is 3 cases per million individuals of white race under 21 years, with a prevalence of 1–5 cases per 1,000,000 inhabitants [3].

The most common location is in the diaphysis or meta-diaphyseal segments of long bones, with the femur being the most frequent site (20–27 %), followed by the tibia, fibula, and humerus [4].

Eighty percent involve bone tissue, and up to 20 % are extraosseous sarcomas, affecting soft tissues without bone involvement but exhibiting the same histopathological findings [5].

From a pathophysiological perspective, a high percentage of cases exhibit a chromosomal change in the genetic locus of cellular DNA. This mentioned cytogenetic anomaly is a chromosomal disorder associated with a translocation of chromosome 22 t (11:22) (q24: q12) [6].

Diagnosis is based on the analysis of clinical findings, with the presence of a painful mass being the most common symptom. Up to one-fifth of cases also present systemic symptoms such as fever, asthenia, anorexia, and weight loss due to the release of catecholamines [7]. Diagnostic imaging, such as X-rays, reveals an osteolytic lesion with a moth-eaten or permeative pattern, onion-skin periosteal reaction, and a large non-mineralized soft tissue mass [8]. Magnetic resonance imaging allows for the assessment of lesion extent and involvement of neurovascular structures, which is crucial for defining treatment options [9].

The final diagnosis is confirmed through biopsy, histologically showing elements of both mesodermal and ectodermal origin [10].

Microscopic morphology reveals the presence of small, round cells with hyperchromatic nuclei, well-defined borders, and an absence of intercellular material; there is abundant cytoplasmic glycogen [9,11].

The treatment of Ewing sarcoma is multidisciplinary, with chemotherapy forming the basis and surgical resection being the fundamental pillar for local control [9,2].

In the oncological management, wide local control surgery and reconstruction are the most accepted option. However, factors such as tumor size, extent, patient age, and distant involvement may complicate this option.

2. Case description

A 7-month-old male presenting with a progressive, painful mass in the left thigh. Diagnostic images reveal an expansive tumor lesion in the proximal femur with periosteal reaction, permeative pattern, and involvement of soft tissues (Image 1).

Fig. 1.

a. X-ray of the femur with a tumor-like lesion in the left proximal femur. b. Pathology with small round cells with hyperchromatic nuclei, CD99 positivity.

A percutaneous biopsy reporting a malignant tumor of small cells with strong reactivity for CD56 and FLI-1, consistent with Ewing sarcoma. The patient underwent neoadjuvant chemotherapy for 8 cycles and subsequently surgery. In October 2019, a wide resection of the proximal femur was performed, followed by reconstruction using a proximal humeral osteoarticular graft (Image 2).

Fig. 2.

a. Proximal humerus allograft.

b. Postoperative control wide tumor resection plus reconstruction with proximal humerus allograft.

The patient completed the 14th cycle of chemotherapy without evidence of tumor recurrence and was placed under strict follow-up and rehabilitation. In October 2021, imaging studies documented joint failure of the allograft (Image 3).

Fig. 3.

Allograft joint failure 2 years after surgery.

The proposal is to proceed with salvage surgery by applying a cemented femoral stem over the remaining allograft to restore hip joint function.

During a follow-up consultation, there is evidence of a risk of femoral stem fracture over the medial cortical bone of the femur. Therefore, a decision is made to enhance it with biological osteosynthesis (Image 4).

Fig. 4.

Post-operative control alloprosthetic hip reconstruction plus bone augmentation with biological osteosynthesis.

The patient has shown satisfactory postoperative progress, being able to walk, without pain and without any recurrence or tumor progression (Image 5).

Fig. 5.

Clinical follow-up 4 years after allograft reconstruction and 2 years after alloprosthetic reconstruction. The triradiate cartilage persists and the acetabulum is molding to the prosthesis without ostecartilaginous resorption.

3. Discussion

Osteo muscular tumors significantly impact the quality of life, especially when they occur at an early age, as in the reported case. In such cases, management options are limited, making adequate reconstruction challenging and raising concerns about morbidity and mortality. Some authors still consider limb salvage surgery relatively contraindicated in patients with a very young skeletal age (under 8 years) [12].

In the presented case, similar to the report by Zoccali and colleagues [13] a malignant tumor in the proximal femur of a pediatric patient is documented. In these cases, where the distal femoral growth plate is disease-free, a reconstruction technique preserving the growth plate is proposed.

Similar to Zoccali [13] we encountered technical challenges in the surgical management, necessitating the exploration of an unconventional treatment alternative. Among these challenges, it's worth mentioning that there was no availability of a modular prosthesis in such a small size. Additionally, concerns arose regarding two potential complications: intramedullary stem perforation could compromise the distal femoral growth plate, and due to the rapid growth of infants, rapid widening of the femoral canal was expected, potentially leading to prosthesis loosening.

The size of an adult femur is not suitable for reconstructing a child's femur, as both the diaphyseal diameter and femoral head are too wide. However, a skeletally mature humerus has an appropriate size to replace segments of a child's femur or tibia, making it the preferred choice in this case.

Initially, the reconstruction was performed using a proximal humeral allograft fixed with a plate and screws, showing a positive response over a 2-year period during which no disease progression was documented.

At the two-year mark, a fracture of the allograft with joint failure occurred, prompting a revision surgery. This involved the application of a non-cemented femoral stem and a 32-diameter head. Due to the identified risk of stem tip fracture, biological osteosynthesis was added to the medial femoral cortex. At the 4-year follow-up, the patient exhibited proper mobility, enabling walking and age-appropriate developmental milestones.

The presence of a congruent alloprosthetic joint allows the triradiate acetabular cartilage to continue growing and also receive the correct mechanical stress from a spherical femoral head.

Muscolo and colleagues [12] published their experience with allografts in 22 patients under 10 years old with lower limb sarcomas (17 osteosarcomas and 5 Ewing sarcomas). Thirteen reconstructions used an intercalary allograft, and nine used an osteoarticular allograft. Physeal involvement was absent in 5 patients and present in 17. Out of 18 patients with follow-up, the average functional score was 27 points with an average radiographic score of 94 %. Eight complications required a second surgery, with allograft removal in 4 cases and preservation in the other 4. The authors consider biological reconstruction with allografts after sarcoma resection a suitable reconstructive procedure in young children.

Similar results are reported in the study by Aponte-Tinao and colleagues [14] which conducted a long-term follow-up (10 years) on patients under 10 years old diagnosed with lower limb sarcomas (14 osteosarcomas and 2 Ewing sarcomas). A total of 10 reconstructions used an intercalary allograft, and 6 used an osteoarticular allograft. Limb length discrepancy and subsequent corrective procedures were common in this series, as were complications resulting from surgical procedures. However, the majority of allografts remained intact during the long-term follow-up.

The work has been reported in accordance with the SCARE criteria [15].

4. Conclusion

The technique of proximal femoral allograft with a proximal humeral graft is an acceptable reconstructive treatment alternative for young patients with Ewing sarcoma, especially when conventional treatment options are limited. This approach helps avoid limb-threatening surgeries such as amputation or rotationplasty, providing a viable and functional solution for limb salvage in these cases.

Consent

Written informed consent was obtained from the patient's parents/legal guardian for publication and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Ethical approval

Ethical approval for this study was granted on December 11, 2023 through document number 85, 657-23 by the Ethics Committee of the Fundación Hospital Pediatrico la Misericordia located in Santafe de Bogota-Colombia on road 17#217.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author contribution

All authors participated significantly in the development of this work. Camilo Soto Montoya and Andrea Franco Betancur conceived the study idea. David Coronado Pantoja, Esteffany Trilleras and Sergio Arroyave coordinated the data collection. David Coronado Pantoja and Sergio Arroyave drafted and edited the manuscript. All authors read and approved the final manuscript.

Guarantor

David Alejandro Coronado Pantoja.

Conflict of interest statement

The authors have no conflict of interest to declare.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.