Modified spinopelvic fixation with a novel three-dimensional-printed element following total sacrectomy for patients...

Total sacrectomy is now a standard curative procedure for primary malignant sacral tumours. Reconstruction, however, remains demanding because of the complex regional anatomy and unique biomechanical environment. Several spinopelvic reconstruction techniques have been reported, all yielding satisfactory functional outcomes. This study aims to evaluate both the clinical outcomes and the biomechanical behavior of a modified spinopelvic fixation construct, which incorporates a novel three-dimensional-printed component following total sacrectomy.

We conducted a retrospective cohort study of 12 consecutive patients (4 men, 8 women; mean age 38 years, range 17-61 years) treated between 2021 and 2024. Eleven patients with primary malignant sacral tumours underwent total en-bloc sacrectomy, and one patient with a giant-cell tumour (GCT) underwent piecemeal resection. All patients received modified spinopelvic reconstruction. Tumour extent was L5-S5 in two patients with recurrent malignant peripheral nerve sheath tumour (MPNST), S1-S5 in eight patients with primary malignancies, S1-S5 in the patient with GCT, and S1-S5 with extension into pelvic zones I/IV in one patient with osteosarcoma. Operative time, oncological outcomes, functional outcomes, complications, and implant status were all reviewed. A finite-element analysis was performed to evaluate the biomechanical behaviour of the novel construct and to compare it with previously described reconstruction models.

All 12 patients had a confirmed histological diagnosis before surgery. Three osteosarcoma and four malignant peripheral nerve sheath tumour (MPNST) patients received neoadjuvant and postoperative chemotherapy; one giant-cell tumour (GCT) patient was treated with denosumab. Mean operative time was 11.5 h (range 7.5-15 h) and mean intra-operative blood loss was 2,616 ml (range 1,200-4,000 ml). During follow-up, local recurrence was detected in two chordoma cases. Functionally, S1-S5 root transection caused sphincter disturbance in 11 patients; two of these also sacrificed a unilateral L5 root, yet none required colostomy or chronic catheterisation. Nine patients lost dorsiflexion strength. At the latest follow-up, 10 patients could walk independently, and 2 required assistive devices. No major perioperative complications were observed; three patients experienced wound healing complications, which were successfully managed with simple debridement, suturing, and negative pressure wound therapy. Only one overweight patient experienced unilateral iliac screw failure without further revision; the remaining 11 patients had no mechanical complications. Finite-element analysis suggested that the current reconstruction may have favorable load-bearing capacity and stability characteristics compared with previously described models.

The modified spinopelvic fixation with the fifth rod and 3D-printing element represents a potential option for anterior column reconstruction after total sacrectomy, with preliminary evidence of satisfactory clinical outcomes in non-overweight patients. Finite-element analysis suggests that the construct may possess adequate stiffness and stability characteristics that could contribute to preventing pelvic-spinal collapse, though these biomechanical findings require further clinical validation. Stress values from the finite-element model indicate a theoretically low risk of implant fracture under static loading or fatigue conditions, but long-term follow-up is necessary to confirm implant durability and exclude late complications such as loosening or breakage.