Reconstruction at our institution is performed when the SI joint has been disrupted, based on the Mayo Spino-Sacral-Pelvic Tumor Classification (Fig. 23.2), following either a total sacrectomy (Mayo Type IA), partial sacrectomy above the S1 foramen (Mayo Type IB), unilateral hemisacrectomy (Mayo Type II), amputative partial sacrectomy plus hemipelvectomy (Mayo Type III), or total sacrectomy and hemipelvectomy (Mayo Type IV). Reconstruction is not necessary for a lower sacrectomy which does not disrupt the SI joints (Mayo Type IC).

Staging of a total sacrectomy (Mayo Type 1A) has been shown to reduce patient morbidity and is currently our preferred technique [13]. We perform this procedure in three stages on three different surgical days. The anterior procedure, which we perform on day 1, includes the harvesting of a vertical rectus abdominis vascularized myocutaneous (VRAM) flap; the pelvic viscera mobilization; the sacral, spinal, and pelvic osteotomies as needed for a specific patient; the vascular mobilization; the nerve root sectioning as needed for a specific patient’s tumor geometry; and the positioning of the VRAM flap in the pelvis over a Silastic sheet that identifies the plane of pelvic dissection. The second stage is the posterior approach and dissection, completion of osteotomies, tumor delivery and removal from the surgical field, and provisional VRAM flap inset followed by wound closure. The patient gets a spinopelvic CT scan on the way to the intensive care unit, which is used in the planning for the reconstruction which occurs as stage 3. The stage 3 reconstruction consists of bilateral bicortical pedicle screws in the two or three most distal remaining vertebrae and one or two iliac screws on each side. Docking sites for the two fibulae which constitute the anterior column sacral reconstruction are then created with a burr in the most caudal portion of the lowest remaining vertebra and in the ilia. The iliac docking sites may be prepared in the supra-acetabular region, in the ischial ramus, or in the ischial tuberosity area, depending on the locations that remain after specimen removal, as seen on the post-resection CT scan. The pelvic docking sites may be prepared during the anterior stage 1 operation, the posterior stage 2 tumor removal operation, or the stage 3 reconstruction operation, depending on the particular patient’s tumor anatomy and which of the three operations present the optimum opportunity to prepare the docking sites. The ideal position of the docking sites in the ilium is at the intersection of the iliopectineal line and a straight line which intersects the center of the hip joint and the most caudal remaining vertebra (Fig. 23.3a). The position of these docking sites ultimately depends on the location and extent of the tumor removal in each patient and the bone areas that remain and are available for fibular strut graft docking.

Fibular allografts or autografts are fashioned in order to be inserted into the docking sites, creating a “cathedral” appearance (Fig. 23.3b). We currently advocate the use of vascularized free fibulas instead of allografts in the setting of previous sacropelvic radiation. In such patients, healing of an allograft may likely be compromised. Following the docking of the fibulae to the most distal remaining vertebra, a bilateral four-rod posterior instrumentation reconstruction with cross-links is performed, and the instrumentation construct is compressed across the docking site (Fig. 23.3c).