In-house three dimensional-printed cutting guides improve surgical accuracy in children who underwent resection of malignant bone tumours of lower limb and reconstruction with allograft

Aims: This study evaluated the accuracy of resection of bone tumours and the fit between host bone and massive bone allograft (MBA) in children with malignant bone tumours of lower limb who underwent surgery using in-house 3-dimensional (3D)-printed patient-specific instruments (PSIs) for tumour resection and graft-specific instruments (GSIs) for shaping the MBA. Methods: This retrospective study included seven children (3 males, 4 females; median age 13) with malignant bone tumours of the lower limb who underwent intercalary resection and reconstruction with MBA between September 2023 and March 2025 using in-house designed 3D-printed PSIs and GSIs. Tumours were located in the femur (5 children) and tibia (2 children). We analysed the accuracy of bone resection, complications of reconstruction, and function of patients. Results: All resections achieved R0 margins. The median planned resection length was 16.5 cm versus 16.8 cm actually resected (median difference 0.2 cm). Bone union was achieved in 13 of 14 (92.9%) osteotomy sites. Bone union was faster at metaphyseal junctions (median 5.9 months) than diaphyseal junctions (median 8.4 months) (p = 0.01). One of the osteotomy sites (7.1%) had a delayed union requiring secondary bone grafting. The median Musculoskeletal Tumour Society score was 30 at the last follow-up. Conclusion: 3D-printed PSIs and GSIs appear to enhance the accuracy of bone tumour resection and host bone-MBA fit, thereby reducing the risks of inadequate margins and non-union, respectively.