(P 104) 3D PRINTED CUTTING GUIDES FOR LONG BONE SARCOMA RESECTION AND INTERCALARY ALLOGRAFT RECONSTRUCTION: A CASE SERIES

Objective: Metaphyseal Sarcomas are common. Historically, if limb preservation is possible, intra-articular resection sacrificing the joint with complex arthroplasty was performed. With the use of 3D printed cutting guides and intercalary allograft reconstruction, the joint can potentially be preserved with better functional outcomes. Two questions remain with this technique, allograft union and margins + local recurrence?. Historically, an unacceptably high rate of allograft non-union and positive margins have been reported. Computed digital images are sent to the engineer to prepare a plan for both the resection guide and allograft preparation. A 3D model is produced that helps place the guide on the bone in the appropriate position to achieve the planned outcome. Next the resection is performed with a 3D printed guide and the specimen removed and compared to the model. Once negative margins are achieved, the allograft is prepared on the back table using the guide to create an identical bone replacement. At the same time, internal fixation can be planned. An intercalary graft is placed in the patient with metal for rigid internal fixation and precise osteosynthesis using compression principles.

Methods: We performed a retrospective review of the first 9 patients treated at our institution with 3D printed technology with significant follow up. Histopathological and clinical data were reviewed with a focus on allograft union, margins, and local recurrence.

Results: All nine patients achieved negative margins with no local recurrences. Allograft union; 16/18 (89%) junctions. 7/9 (78%) grafts remain at most recent follow-up. One patient was revised to a modular oncology devise due to non-union after irradiation for Ewing's sarcoma, a second osteosarcoma revised to modular oncology.

Conclusion: The use of 3D printed technology is very useful to preserve the joint around metaphyseal sarcoma. It not only helps achieve negative margins but a precise reconstruction with a high union rate.