Surgical Guides (Patient-Specific Instruments) for Pediatric Tibial Bone Sarcoma Resection and Allograft Reconstruction

To achieve local control of malignant pediatric bone tumors and to provide satisfactory oncological results, adequate resection margins are mandatory. The local recurrence rate is directly related to inappropriate excision margins. The present study describes a method for decreasing the resection margin width and ensuring that the margins are adequate. This method was developed in the tibia, which is a common site for the most frequent primary bone sarcomas in children. Magnetic resonance imaging (MRI) and computerized tomography (CT) were used for preoperative planning to define the cutting planes for the tumors: each tumor was segmented on MRI, and the volume of the tumor was coregistered with CT. After preoperative planning, a surgical guide (patient-specific instrument) that was fitted to a unique position on the tibia was manufactured by rapid prototyping. A second instrument was manufactured to adjust the bone allograft to fit the resection gap accurately. Pathologic evaluation of the resected specimens showed tumor-free resection margins in all four cases. The technologies described in this paper may improve the surgical accuracy and patient safety in surgical oncology. In addition, these techniques may decrease operating time and allow for reconstruction with a well-matched allograft to obtain stable osteosynthesis. 1. Introduction The tibia is a common site for the most frequent malignant primary bone tumors in children, osteosarcoma (tibia is affected in 27% of cases), and Ewing’s sarcoma (8% of cases) [1, 2]. Improvements in diagnosis and therapeutic techniques have increased interest in limb-salvage surgery. However, several studies have suggested that limb-salvage surgery may increase local recurrence in the case of inappropriate excision margins [3]. To achieve local control of disease and to improve oncological results, wide resection margins are mandatory. However, a wide surgical excision results in a large residual bone defect that requires restoration [4]. We propose a new technique to decrease the width of the excision margins with patient-specific instruments (PSIs). In this method, the resection is carefully planned prior to surgery, based on magnetic resonance imaging (MRI) and computed tomography (CT), which are used to define the trajectories of the resection and create PSIs. The function of the reconstructed limb is of major interest, especially in young and physically active patients who place high demands on their limbs. The limb reconstruction must also be durable because life expectancy for many of these patients is several