Computer-Assisted Navigation During an Anterior-Posterior En Bloc Resection of a Sacral Tumor

Surgical and Oncologic Outcome following Sacrectomy for Primary Malignant Bone Tumors and Locally Recurrent Rectal Cancer

INTRODUCTION

Bone sarcoma or direct pelvic carcinoma invasion of the sacrum represent indications for partial or total sacrectomy. The aim was to describe the oncosurgical management and complication profile and to analyze our own outcome results following sacrectomy.

METHODS

In a retrospective analysis, 27 patients (n = 8/10/9 sarcoma/chordoma/locally recurrent rectal cancer (LRRC)) were included. There was total sacrectomy in 9 (incl. combined L5 en bloc spondylectomy in 2), partial in 10 and hemisacrectomy in 8 patients. In 12 patients, resection was navigation-assisted. For reconstruction, an omentoplasty, VRAM-flap or spinopelvic fixation was performed in 20, 10 and 13 patients, respectively.

RESULTS

With a median follow-up (FU) of 15 months, the FU rate was 93%. R0-resection was seen in 81.5% (no significant difference using navigation), and 81.5% of patients suffered from one or more minor-to-moderate complications (especially wound-healing disorders/infection). The median overall survival was 70 months. Local recurrence occurred in 20%, while 44% developed metastases and five patients died of disease.

CONCLUSIONS

Resection of sacral tumors is challenging and associated with a high complication profile. Interdisciplinary cooperation with visceral/vascular and plastic surgery is essential. In chordoma patients, systemic tumor control is favorable compared to LRRC and sarcomas. Navigation offers gain in intraoperative orientation, even if there currently seems to be no oncological benefit. Complete surgical resection offers long-term survival to patients undergoing sacrectomy for a variety of complex diseases.

Primary Tumors of the Sacrum: Imaging Findings

The diagnosis of sacral neoplasms is often delayed because they tend to remain clinically silent for a long time. Imaging is useful at all stages of managing sacral bone tumors: from the detection of the neoplasm to the long-term follow-up. Radiographs are recommended as the modality of choice to begin the imaging workup of a patient with known or suspected sacral pathology. More sensitive examinations such as computerized tomography (CT), magnetic resonance (MRI), or scintigraphy are often necessary. The morphological features of the lesions on CT and MRI help to orientate the diagnosis. Although some imaging characteristics are helpful to limit the differential diagnosis, an imaging-guided biopsy is often ultimately required to establish a specific diagnosis. Imaging is of paramount importance even in the long-term follow-up in order to assess any residual tumor when surgical resection is incomplete, to assess the efficacy of adjuvant chemotherapy and radiotherapy, and to detect recurrence.

Image guidance in spine tumor surgery

Beginning with basic stereotactic operative methods in neurosurgery, intraoperative navigation and image guidance systems have since become the norm in that field. Following the introduction of image guidance into spinal surgery, there has been a dramatic increase in its utilization across disciplines and pathologies. Spine tumor surgery encompasses a wide range of complex surgical techniques and treatment strategies. Similarly to deformity correction and trauma surgery, spine navigation holds potential to improve outcomes and optimize surgical technique for spinal tumors. Recent data demonstrate the applicability of neuro-navigation in the field of spinal oncology, particularly for spinal stabilization, maximizing extent of resection and integration of minimally invasive therapies. The rapid introduction of new, less invasive, and ablative surgical techniques in spine oncology coupled with the rising incidence of spinal metastatic disease make it imperative for spine surgeons to be familiar with the indications for and limitations of imaging guidance. Herein, we provide a practical, current concepts narrative review on the use of spinal navigation in three areas of spinal oncology: (a) extent of tumor resection, (b) spinal column stabilization, and (c) focal ablation techniques.

Systematic review on the utility of magnetic resonance imaging for operative management and follow-up for primary sarcoma-lessons from extremity sarcomas

Primary sarcomas of the vertebral column affect roughly 5 in every million persons annually, of which half to one-third are malignant. Treatment of these lesions requires multimodal management, often employing attempts at en bloc resection of the lesion with negative margins. This may be facilitated using magnetic resonance imaging for preoperative margin planning, but current literature is lacking regarding the use of such imaging to accurately predict planned surgical margins. Here we review prior studies describing the use of magnetic resonance imaging for en bloc resection of sarcomas of the extremities to identify learning points for application to the treatment of spinal neoplasms. We conducted a systematic review of the PubMed and EMBASE literature. Included studies described the accuracy of MRI for preoperative evaluation of tumor margins, intraoperative guidance for en bloc resection, or post-operative evaluation of residual or recurrent disease. All included studies described patients treated for osseous or soft tissue sarcoma of the limbs. We found 1,705 unique references of which 27 met criteria for inclusion. Seven studies reported MR had an overall diagnostic accuracy of 93.6-96% for preoperative margin evaluation with non-contrast T1 most accurately reflecting true margins. In the nine articles reporting results of MR-guided resection, negative margins were achieved in 88.8-100% of cases with a closest margin of 2-4 mm. Eleven articles combined reported the accuracy of MR for residual disease or local recurrence, with a mean sensitivity and specificity of 71.7% and 79.3%, respectively for residual disease and 87.9% and 85.9%, respectively for local recurrence. The current literature for appendicular musculoskeletal sarcoma suggests that MR is highly accurate for defining tumor margins preoperatively, guiding osteotomy cuts intraoperatively, and documenting recurrence or residual disease. Further evidence is necessary to evaluate the degree to which it can accurately guide osteotomy planning for en bloc resection of vertebral primaries.

Use of image-guided bone scalpel for resection of spine tumors: technical note

In the literature, the use of navigation for spine tumor surgery has largely centered on implant placement. We describe the cases of two patients with spinal tumors on whom we utilized our resection technique of registering an ultrasonic bone scalpel (UBS) to a navigation system. In both cases, we achieved a satisfactory tumor resection with negative margins and excellent neurologic outcomes. We feel that using the navigation-registered UBS is a valuable tool to increase the operator's ability to achieve desired resections while minimizing the neurologic deficits and operative morbidity associated with these challenging surgical cases.

The value of computer-assisted navigation for bone reconstruction after tumor resection

This study was designed to evaluate the use of computer-assisted navigation with computed tomography (CT) images for bone reconstruction after resection in malignant bone tumor treatment. Forty-five patients with malignant bone tumors were recruited for this study. CT scan images in a computer-assisted navigation system were used to assist during the osteotomy, the pairing with allografts, and the monitoring of the allograft and joint lines to perform joint reconstruction. Our results show that osteotomy and allograft pairing were successful in all patients. The average duration of the osteotomy procedures was 46.8±12.3 min; and the average pairing time was 32.5±9.8 min. The anatomical registration points and the three-dimensional virtual CT images were successfully matched. The average error of registration was 0.36±0.09 mm. Also, the range of tumor resection and allograft osteotomy were successfully paired, with an average error of 0.11±0.03 mm. No complications such as unequal limbs length or joint deformities occurred after reconstruction. The average follow-up time was 11.6±3.9 months. The tumor recurrence rate was 11.1% (5/45) and the survival rate 95.6% (43/45). The average healing time for the allograft and host bone was 5.5±1.2 months and no unexpected internal fixations, fractures or joint collapses occurred. The average knee joint functionality MSTS score was 25.5±6.6 points. No significant differences were found in the length of tumor resection, rate of negative incision margin, duration of osteotomy or of pairing, registration error or allogeneic bone and defect matching error averages between those patients with tumor recurrence and those without it (p>0.05). Based on our results, the computer-assisted navigation system for bone reconstruction after malignant tumor resection allows for high precision during osteotomy, delivers a high success rate of pairing, results in great limb function and low complication rates, and is thus a highly successful and safe approach benefiting bone cancer patients.