Biology and technology in the surgical treatment of malignant bone tumours in children and adolescents, with a special note on the very young.

Purpose: The main challenge in reconstruction after malignant bone tumour resection in young children remains how and when growth-plates can be preserved and which options remain if impossible.

Methods: We describe different strategies to assure best possible long-term function for young children undergoing resection of malignant bone tumours.

Results: Different resources are available to treat children with malignant bones tumours: a) preoperative planning simulates scenarios for tumour resection and limb reconstruction, facilitating decision-making for surgical and reconstructive techniques in individual patients; b) allograft reconstruction offers bone-stock preservation for future needs. Most allografts are intact at long-term follow-up, but limb-length inequalities and corrective/revision surgery are common in young patients; c) free vascularized fibula can be used as stand-alone reconstruction, vascularized augmentation of structural allograft or devitalized autograft. Longitudinal growth and joint remodelling potential can be preserved, if transferred with vascularized proximal physis; d) epiphysiolysis before resection with continuous physeal distraction provides safe resection margins and maintains growth-plate and epiphysis; e) 3D printing may facilitate joint salvage by reconstruction with patient-specific instruments. Very short stems can be created for fixation in (epi-)metaphysis, preserving native joints; f) growing endoprosthesis can provide for remaining growth after resection of epi-metaphyseal tumours. At ten-year follow-up, limb survival was 89%, but multiple surgeries are often required; g) rotationplasty and amputation should be considered if limb salvage is impossible and/or would result in decreased function and quality of life.

Conclusion: Several biological and technological reconstruction options must be merged and used to yield best outcomes when treating young children with malignant bone tumours.

Level Of Evidence: Level V Expert opinion.