Reconstruction with customized, 3D-printed prosthesis after resection of periacetabular Ewing's sarcoma in children using "triradiate cartilage-based" surgical strategy:a technical note

Abstract

Background: Surgery for Ewing sarcoma involving acetabulum in children is challenging. Considering the intrinsic structure of immature pelvis, trans-acetabular osteotomy through triradiate cartilage might be applied. The study was to describe the surgical technique and function outcomes of trans-acetabular osteotomy through triradiate cartilage and reconstruction with customized, 3D-printed prosthesis.

Methods: Two children with periacetabular ES were admitted to our hospital. The pre-operative imaging showed the triradiate cartilage was not penetrated or wholly affected by tumor. After neoadjuvant chemotherapy, the tumor was excised by trans-acetabular osteotomy basing on "triradiate cartilage strategy" and the acetabulum was reconstructed with the customized, 3D-printed prosthesis. The prosthesis was designed in Mimics software basing on the images from CT, optimized by topology technique, and examined in FE model. After implantation, the oncological and functional outcomes were evaluated with radiography, CT, and MSTS score.

Results: The operation time and intra-operative blood loss in these two children were 3.5h, 2.5h and 300 ml, 600 ml, respectively. The postoperative specimen showed the tumor was en bloc removed with safe margin. In the latest follow-up (48 months and 24 months), both patients were free of disease and had satisfactory function according to MSTS score. The radiography indicated the prosthesis fit the defect well without loosening.

Conclusion: The customized, 3D-printed prosthesis could provide optimal reconstruction of pelvic ring and satisfactory hip function after trans-acetabular osteotomy in children.

The translational potential of this article: This study provides promising results of implantation of customized 3D printing prosthesis in children's pelvic sarcoma, which may bring a new design method for orthopaedic implants.

Keywords: 3D printing; Acetabulum; Ewing sarcoma; Pelvis; Prosthesis.

Fig. 1

The tumor was located in the ilium and infiltrated the acetabulum close to the triradiate cartilage (TRC). And the osteotomy could be performed through TRC to maximally preserve the un-affected acetabular component.

Fig. 2

(A) Pelvic radiograph showed a large osteolytic lesion in the right ilium. (B) Axial CT images showed a large destructive lesion in the right iliac wing with soft tissue mass. (C) The 3D reconstructed CT images showed the expandable osteolytic lesion with soft-tissue invasion. (D) The coronal and sagittal CT images showed that the tumor did not penetrate the triradiate cartilage. (indicated by white arrow).

Fig. 3

(A, D) The A-P and lateral view of the prosthesis that was designed to mimic pelvic anatomical structure basing on CT data by Mimics software. (B, E) The A-P and lateral view of the prosthesis with reduced volume after topology optimization. (C) The loading on prosthesis was examined in finite element (FE) model to determine the proper design. (F) The prosthesis was simulated to install on pelvic model.

Fig. 4

(A) Gross photography of 3D-printed prostheses (B) Preoperative simulated reconstruction was performed in pelvic model to verify the matching between prosthesis and residual bone. (C) The comparison image of excised tumor and the prosthesis. (D) The 3D-printed prosthesis was implanted after tumor excision.

Fig. 5

(A) Pelvic radiograph at 48 months postoperatively; (B) CT indicated that the bone was tightly bound to the prosthesis at the interface 48 months postoperatively; (C) Radiograph of the full length of both lower limbs at 48 months postoperatively.

Fig. 6

(A) Weight-bearing position of the patient. (B) Flexion position of the patient. (C) External position of the patient. (D) Internal position of the patient. (E) Abduction position of the patient.

Fig. 7

(A, B) The X-ray and MRI of pelvis indicated the lesion of left ilium and upper acetabular component with soft tissue mass. (C, D) The coronal and sagittal CT images showed the tumor did not penetrate the triradiate cartilage (indicated by white arrow).

Fig. 8

(A, D) The A-P and lateral view of the prosthesis that was designed to mimic pelvic anatomical structure basing on CT data by Mimics software. (B, E) The A-P and lateral view of the prosthesis with reduced volume after topology optimization. (C) The prosthesis was examined in finite element (FE) model. (F) The prosthesis was simulated to install on pelvic model.

Fig. 9

(A) Pre-operative CT reconstruction showed the lesion located in left ilium and upper acetabular component; (B) The prosthesis was simulated to be implanted in pelvic model to verify the matching; (C) The comparison photograph of pelvic model and excised tumor; (D) The intra-operative image showed the prosthesis was implanted to fill the defect.

Fig. 10

(A) Pelvic radiograph immediately after operation; (B) CT scans at 24 months postoperatively; (C, D) 3D reconstruction of CT image showed the prosthesis was in appropriate position and femoral head had adequate coverage.