Background:There are a limited but increasing number of case reports and series describing the use of 3D-printed prostheses in bone tumor surgery.Methods:We describe a new approach to performing nerve-preserving hemisacrectomy in patients with sacral giant cell tumors with reconstruction using a novel 3D-printed patient-specific modular prosthesis. The series included four female and two male patients with a mean age of 34 years (range, 28–42 years). Surgical data, imaging assessments, tumor and functional status, implant status, and complications were retrospectively analyzed in six consecutive patients.Results:In all cases, the tumor was removed by sagittal hemisacrectomy, and the prosthesis was successfully implanted. The mean follow-up time was 25 months (range, 15–32 months). All patients in this report achieved successful surgical outcomes and symptomatic relief without significant complications. Clinical and radiological follow-up showed good results in all cases. The mean MSTS score was 27.2 (range, 26–28). The average VAS was 1 (range, 0–2). No structural failures or deep infections were detected in this study at the time of follow-up. All patients had good neurological function. Two cases had superficial wound complications. Bone fusion was good with a mean fusion time of 3.5 months (range, 3–5 months).Conclusion:These cases describe the successful use of custom 3D-printed prostheses for reconstruction after sagittal nerve-sparing hemisacrectomy with excellent clinical outcomes, osseointegration, and durability.