Purpose. Curative treatment of malignancies in the sacrum and lumbar spine frequently requires en-bloc spinopelvic resection. There is no standard classification of these procedures. We present a classification of these resections based on analysis of 45 consecutive cases of oncologic spinopelvic resections. This classification implies a surgical approach, staging algorithm, bony and soft tissue reconstruction, and functional outcomes following surgery. Method. We reviewed oncologic staging, surgical resections, and reconstructions of 45 consecutive patients undergoing spinopelvic resection with curative intent. Mean follow-up of surviving patients was 38 months. Common themes in these cases were identified to formulate the surgical classification. Results. Tumors included chondrosarcoma (n=11), other sarcomas (n=11), osteosarcoma (n=9), chordoma (n=6), locally invasive carcinoma (n=5), and others (n=3). Resections could be divided into 5 types based on the exent of the lumbosacral resection and the need for an associated external hemipelvectomy. Type 1 resections included a total sacrectomy +/− lumbar spine resection. Type 2 resections included hemisacrectomy +/− partial lumbar excision, and iliac wing resection. Type 3 resections encompassed external hemipelvectomy with hemisacrectomy +/− partial lumbar excision. Type 4 resections encompassed external hemipelvectomy with total sacrectomy +/− lumbar excision. Type 5 excisions involved hemicorporectomy type procedures. For each type of resection we have developed guidelines for trans- vs retroperitoneal surgical approaches, staging of the resections, bony and soft tissue reconstructive procedures to re-establish spinopelvic continuity, and predicted functional outcomes for patients. At mean 38 month follow-up on surviving patients, 28 are living and 17 are deceased. Twenty-two of 28 surviving patients are disease free. Nineteen of 26 surviving patients are independent in their activities of daily living. Conclusion. En bloc spinopelvic resections may be classified into five types based on the extent of lumbosacral excision and the need for concurrent hemipelvectomy. Using this classification system, we have formulated treatment strategies to guide surgical approach, procedural staging, bony and soft tissue reconstructive procedures, and expected functional outcomes. Long term survival and independent function can be achieved in this challenging patient population

Ten to 15% of the pelvic girdle tumors are primary malignant bone tumors, while about 80% are osseous metastases. Due to improved function, enhanced quality of life, and acceptable local recurrence rates, limb salvage surgery has replaced external hemipelvectomies in many cases of primary malignancies. However, large segmental bony defects and poor bone quality due to the disease process itself and subsequent treatment (i.e. chemotherapy and radiation) can make stable implant fixation difficult when performing a total hip arthroplasty (THA) for oncologic periacetabular lesions with concurrent fractures. Various methods are available to reconstruct the hemipelvis, and include large structural allografts, allograft-prosthetic composites (APCs), custom-made endoprostheses, modular saddle prostheses, and modular hemipelvis endoprostheses. However, short- and mid-term results from our institution indicate that tantalum reconstructions with adjuvant screw fixation and supplemental reinforcement cages provide reasonable improvement in clinical outcomes and stable fixation in situations with massive bone loss and compromised bone quality. On the femoral side, cemented fixation remains a viable option (including proximal femoral replacements), but uncemented distal fixation with extensively-porous coated cylindrical stems or modular fluted tapered stems can be considered if the disease process (or subsequent treatment) primarily affects the proximal femur. In addition to long-term fixation, post-operative dislocations remain a significant concern given the often compromised abductor mechanism