Sacral Reconstruction with a 3D-Printed Implant after Hemisacrectomy in a Patient with Sacral Osteosarcoma: 1-Year Follow-Up Result

Abstract

Pelvic reconstruction after sacral resection is challenging in terms of anatomical complexity, excessive loadbearing, and wide defects. Nevertheless, the technological development of 3D-printed implants enables us to overcome these difficulties. Here, we present a case of sacral osteosarcoma surgically treated with hemisacrectomy and sacral reconstruction using a 3D-printed implant. The implant was printed as a customized titanium prosthesis from a 3D real-sized reconstruction of a patient's CT images. It consisted mostly of a porous mesh and incorporated a dense strut. After 3-months of neoadjuvant chemotherapy, the patient underwent hemisacretomy with preservation of contralateral sacral nerves. The implant was anatomically installed on the defect and fixed with a screw-rod system up to the level of L3. Postoperative pain was significantly low and the patient recovered sufficiently to walk as early as 2 weeks postoperatively. The patient showed left-side foot drop only, without loss of sphincter function. In 1-year follow-up CT, excellent bony fusion was noticed. To our knowledge, this is the first report of a case of hemisacral reconstruction using a custom-made 3D-printed implant. We believe that this technique can be applied to spinal reconstructions after a partial or complete spondylectomy in a wide variety of spinal diseases.

Keywords: 3D-printing; instrumentation; sacrum; spinal fusion.

Fig. 1. (A) Preoperative Gd-enhanced T1-weighted pelvic MRI showing a mass with peripheral enhancement at the left side of the sacrum (arrowheads) with soft tissue invasion (asterisk). (B) After three cycles of neoadjuvant chemotherapy for 3 months, the volume of tumor mass (arrowheads) and the extent of extraosseous invasion (asterisk) decreased significantly.

Fig. 2. Illustration of 3D-implant design process. A customized implant was designed using 3D software (Mimics, 3-matic, Magics). The design process (dotted box) was performed during neoadjuvant chemotherapy. The design was interactively corrected reflecting the final pelvic MRI and RP models before final printing. RP, rapid prototype.

Fig. 3. (A) Custom-made 3D-printed hemisacral construct with a specific porous titanium structure. The screw hole and contact surfaces were made with high-density structure. (B) The left sacrum was excised with en bloc resection. The shape and size of the implant were the same as the resected mass.

Fig. 4. (A) Rigid reconstruction achieved with the 3D implant and screw-rod system. (B) Lateral X-ray at postoperative 1 week demonstrates a complete lumbosacral construct. (C) AP X-ray at postoperative 1 week demonstrates a complete lumbosacral construct. AP, anterior-posterior.

Fig. 5. Axial CT 1 year postoperatively shows excellent bone ingrowth into the midline strut (asterisk) and porous surface (arrowheads).