Pelvic Sarcoma Resection and Reconstruction

Gavin L. Mills, MD

Samuel E. Broida, MD

Matthew T. Houdek, MD, FAAOS

Dr. Houdek or an immediate family member serves as a paid consultant to or is an employee of Link Orthopaedics and serves as a board member, owner, officer, or committee member of Mid-America Orthopaedic Association and Musculoskeletal Tumor Society. Neither of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter: Dr. Mills and Dr. Broida.

ABSTRACT

Pelvic tumor resections are thought to be some of the most technically challenging surgeries in orthopaedics. Although the pelvis is a common location for the development of sarcomas, the complex three-dimensional anatomy (and the proximity to critical neurovascular and visceral structures) has historically made it difficult to achieve a negative margin resection, elevating the risk of local tumor recurrence. Along with an elevated risk of local recurrence, pelvic sarcomas are known to be associated with a higher risk of metastatic disease and subsequent death compared with extremity sarcomas. Biomechanically, the sacroiliac joint is the only mechanical connection between the axial spine and lower extremities, and often after resection a discontinuity is created. There have been advances in the development of intraoperative navigation techniques as well as the use of custom implants to reconstruct the pelvis following an oncologic resection. However, reconstruction of this continuity is often not necessary and is associated with a substantially elevated risk of postoperative complications; therefore, the utility of these newer implant systems remains to be elucidated.

INTRODUCTION

With the advances in surgical techniques and use of chemotherapy and radiation therapy for the management of pelvic bone sarcomas, limb salvage surgery has become the cornerstone of treatment for patients with localized tumors. In addition to seeing these sarcomas in the extremities, orthopaedic oncologists often encounter chondrosarcomas, Ewing sarcomas, and osteosarcomas. Patients with pelvic sarcomas are known to have worse outcomes than patients with extremity bone sarcomas. Although survival is worse, the only hope for cure in patients with a bone sarcoma of the pelvis is a multidisciplinary team approach.

ANATOMIC CONSIDERATIONS

The pelvis is a common location for the development of bone sarcomas; the incidence of pelvic bone sarcomas has been increasing since the 1970s.¹ The pelvis is also a common area for radiation-associated bone sarcomas.²^,³ Patients with pelvic tumors often present with vague symptoms ranging from pain, bowel or bladder changes, weight loss, fatigue, and lower extremity swelling. This is largely secondary to the ability of the tumor to grow and push the surrounding visceral and neurovascular structures until it is large enough to cause substantial symptoms such as a pathologic fracture, or these tumors are found incidentally during imaging when the patient is being evaluated for hip or back pain, which can often lead to a delay in diagnosis.⁴ Because of this delay, these tumors are often large when they are discovered, which portends a worse prognosis as reflected in the recent changes to the American Joint Committee on Cancer staging system.⁵ As discussed in a 2020 study, a multidisciplinary team approach is required; treatment should include surgical resection with a negative margin.⁶

To classify resections of the pelvis, the Enneking and Dunham system (Figure 1) has been used since 1978.⁷ This system has allowed for orthopaedic oncologists to discuss the resection in addition to making recommendations for the potential role of a reconstruction. Tumors are categorized based on their anatomic location: iliac wing (type I), periacetabular (type II), ischiopubic (type III), and sacral (type IV).⁷ For sacral tumors, this classification often does not describe the extent of resection necessary, because often the tumors will extend into the lower lumbar spine, and resection of tumors involving the sacrum frequently leads to immediate and permanent loss of neurologic function. To account for these differences, classification systems for sacral resections have been proposed.⁶^,⁸ Unlike other sacropelvic tumor classifications,⁸^,⁹ the Mayo Clinic Classification for these resections takes into account pelvic resections, including amputative sacrectomies.⁶

FIGURE 1 Drawing showing the Enneking and Dunham classification system for pelvic tumor resection.

These tumors commonly involve multiple pelvic segments, with different anatomic and biomechanical considerations for each area of resection; therefore, it is important to carefully review preoperative images to develop a surgical plan and assemble the appropriate multidisciplinary team for the resection. Often in the setting of a type I resection where the sciatic notch can be maintained or in the setting of a type III resection, no bony reconstruction is thought to be necessary secondary to maintenance of the posterior pelvic ring (spinofemoral continuity); however, soft-tissue reconstruction is often necessary to prevent hernia formation.⁷^,¹⁰ When there is disruption of the continuity between the lower extremities and the spine (type II or I/IV), bony reconstruction has been advocated for; however, comparison studies have shown that this may not always be necessary. Therefore, this topic remains a subject of contentious debate.¹⁰^,¹¹

RECENT ADVANCES

The complex bony anatomy of the pelvis can make it difficult to achieve an adequate surgical bony margin, even for experienced surgeons.¹² In the pelvis, having anything other than a wide margin has been shown to increase the risk of local recurrence, which also affects patient survival.⁴ Similar to other areas of orthopaedics, there have been recent advances in the use of three-dimensional (3D) models, patient-specific instrumentation (PSI) and cutting guides, custom implants, and intraoperative navigation to improve the precision of a resection and to facilitate reconstruction.

3D Models and PSI

3D printing has been used since the 1980s, but recent advances in technology and imaging have allowed for the rapid expansion and adoption of anatomic models to be used for surgical training, surgical planning between a multidisciplinary team, and patient education.¹³ The anatomic models can also be used to print PSI guides to accommodate a resection margin based on the fusion of preoperative imaging (Figure 2). This allows the surgeon to place the guides intraoperatively based on a selected location; however, the contact surfaces often need to be cleared of overlying soft tissue to allow the guide to sit directly on the bone. PSI guides have been used in the pelvis and have been found to allow for a less invasive procedure, with improvements in the accuracy of resection.¹⁴^,¹⁵

FIGURE 2 A, Coronal oblique magnetic resonance image with contrast showing a small cartilaginous tumor that was incidentally discovered in the posterior ilium. B, Coronal oblique magnetic resonance image with contrast showing that the tumor grew over a 5-year period and was thought to represent a chondrosarcoma, which was confirmed on preoperative biopsy. C, Preoperative imaging was used to create a template for resection based on adding a 2-cm bony margin (orange) and planned planes of resection (blue lines) to preserve the underlying nerve roots. D, A three-dimensional model was fabricated along with cutting guides to assist with the resection of the tumor. E, Intraoperative photograph shows the posterior portion of the utilitarian pelvic incision was used, and the guides were placed on the pelvis and sacrum (arrows). Intraoperative photographs show that the tumor was resected en bloc using the guides (F), which allowed the preservation of the gluteal vessels and nerve as they exited the sciatic notch (G). H, Photograph of the resected specimen showed clear margins.

Computer-Assisted Navigation

Similar to 3D-printed PSI guides, computer navigation fuses the preoperative imaging to allow the surgeon to determine the planes of resection based on the tumor location and planned margins. As discussed in a 2021 study, intraoperatively referenced trackers are placed away from the tumor and margin, on either the iliac crest or posterior superior iliac spine, allowing for paired-point and surface-point matching, with a registration error of less than 1 mm.¹⁶ This has been shown to improve the ability of the surgical team to achieve a wide bony margin and reduce the risk of local recurrence.¹⁶^,¹⁷ Navigation can also be used to improve the accuracy of the reconstruction by allowing custom implants or allografts to replicate the specimen that was resected.¹⁶^,¹⁸ Although navigation allows for improvement in obtaining a wide bone margin, it has not been shown to improve the soft-tissue margin necessary to reduce the risk of a soft-tissue recurrence in the pelvis.¹⁹

Intraoperative Assessment of Soft-Tissue Margins

Currently, both PSI and navigation lack the ability to assess the soft-tissue margin intraoperatively, leading to recurrences in the soft-tissue. Intraoperative evaluation of surgical margins with indocyanine green dye fluorescence may allow for the assessment of soft tissue in patients with a pelvic bone sarcoma, because this method has been found to be useful in both soft-tissue sarcomas and bone sarcomas to reduce the risk of an unexpected
positive margin. However, future studies are still needed to determine if the results from smaller recent series are replicated in larger patient groups.²⁰^,²¹

Pelvic Reconstruction

Bony reconstruction of the pelvis is a debated topic, especially for patients with an iliosacral resection (type I/IV) or those whose resection includes the acetabulum (type II). This is because patients who have no formal bony reconstruction have been found to have a lower rate of postoperative complications, with functional outcomes similar to those of patients undergoing reconstruction of the pelvis. Because of the high rate of complications and often poor patient survival, systematic reviews have advocated for patients to not have a formal bony reconstruction.²² Therefore, the decision to perform a reconstruction is individualized and based on surgical factors and patient expectations and function.

Iliosacral Resection

The sacrum is the only mechanical connection between the spine, pelvis, and lower extremities. The sacroiliac joint is a wedge-shaped, interlocking joint, which is highly constrained and has to resist compression and also rotation, allowing for 2^° of motion and translation of only 0.7 mm.²³^,²⁴ Because of these complex biomechanics, reconstruction of the sacroiliac joint following iliosacral resections is a technically demanding procedure.

In patients undergoing a type I/IV resection, the decision needs to be made regarding whether reconstruction of the pelvic ring should be undertaken (Figure 3). Resections without a formal bony reconstruction result in medialization of the hip joint, improving the biomechanics of weight bearing by centralizing the weight-bearing force. The residual pelvis rotates through the pubic symphysis and forms a pseudarthrosis between the remaining pelvis and sacrum. These patients often require the use of a shoe lift; however, comparative studies have found a reduction in the use of gait aids and postoperative complications, with similar functional outcomes, in comparison with patients undergoing a bony reconstruction.¹¹^,²⁵

FIGURE 3 Reconstructive options for patients undergoing an iliosacral resection are shown. A, AP radiograph from a patient with no formal bony reconstruction of the sacroiliac joint, with the remaining pelvis rotating through the symphysis and medialization of the hip joint. B, AP radiograph from a patient undergoing lumbosacral fusion with the placement of a vascularized fibula flap to support the anterior column fixation.

Spinopelvic instrumentation provides stability to the pelvic ring through iliolumbar fusion and is often accomplished with pedicle screw fixation in the remaining spine and pelvis, which is often augmented with either vascularized flaps or nonvascularized bone grafts.²⁶^,²⁷^,²⁸ Compared with the use of pedicle screw and rod fixation alone, the addition of a bone graft improves the anterior column support of the reconstruction, increasing the load to failure.²⁹ In centers that use bony augmentation with the fibula, union rates have been found to be improved with the use of a vascularized flap compared with an allograft fibula, with subsequent improved function in patients with
a vascularized flap.²⁶ Although vascularized flaps increase the length of time needed to complete the procedure, their use is advocated to reduce the risk of construct failure, especially in the setting of previous radiation therapy.

Restoration of the pelvic ring has been associated with improvements in patient function in several series, yet is associated with increased surgical times and postoperative complications, including mechanical failure of the construct and wound complications.¹¹^,²⁷^,³⁰^,³¹ Reconstruction lateralizes the joint center, and if the resection includes the abductors and/or the gluteal nerves, patients will often have a Trendelenburg gait following surgery, necessitating the use of a cane. 3D-printed implants have recently been developed to restore pelvic ring stability.⁸^,³²^,³³ Comparative studies between patients who have not had a formal reconstruction and a 3D-printed implant have yet to be performed; in addition, long-term follow-up for these new implant systems is lacking. Therefore, the use of these implants for all patients cannot be recommended at this time.

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