Navigated multiplanar osteotomies for spinal primary bone tumors

INTRODUCTION

Malignant or benign spinal primary bone tumors (SPBTs) with aggressive local behavior generally require en bloc resection. This entails removing the entire, intact tumor surrounded by a margin of healthy tissue. The challenge is to preserve as much surrounding normal tissue/ structures as possible and avoid damaging contiguous spinal cord/nerves, and other vital structures.[10] Osteotomies that pass through tumor-free tissue are now more readily/safely performed utilizing 3D preoperative planning and intraoperative navigation (i.e., to perform uniplanar cuts of the vertebral body [VB]).[4,6] Here, we report our experience planning and performing navigated multiplanar osteotomies for 14 en bloc resections of SPBT.

MATERIALS AND METHODS

This was a retrospective analysis of 14 patients with SPBT; there were 11 malignant tumors (i.e., six chordomas and five chondrosarcomas) and three locally aggressive benign SPBT (i.e., osteoblastomas). These patients were operated on consecutively at a single center between 2014 and 2019. Eleven tumors (78.5%) were in the sacrum, while the three remaining were in the thoracic spine. The eight males and six females averaged 41.4 years of age [Table 1]. All patients underwent preoperative computed tomography (CT) and magnetic resonance (MR) examinations to determine tumor volume/location. Once images were merged, 3D preoperative planning was performed, and oncological margins were calculated utilizing two-dimensional images.

Table 1:: Patient data: 14 benign (locally aggressive) and malignant SPBT.

RESULTS

Forty en bloc resections in 14 patients were accompanied by osteotomies utilizing preoperative 3D planning and navigation [Figures 1 and 2]. Resection margins were classified by a musculoskeletal pathologist as tumor free; 12 were marginal (<1 cm) resections, while in two patients, margins were wide (>1 cm). Patients were followed for a was average of 31 months (range 12–61) (i.e., quarterly for the first 2 years, semi-annually over the next 3 years, and annually after the 5^th postoperative year). At last, follow-up, 3 patients (21.4%) had experienced local recurrences; all occurred in the sacrum (two chordomas and one chondrosarcoma) and were classified as Enneking Stage 2B [Table 1].[2] Seven (50%) of 14 patients developed nononcological complications; 3 (21.4%) involved postoperative deep infections treated with surgical debridement and intravenous antibiotics [Table 1].

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Figure 1:: (a-c) Sagittal, coronal, and axial computed tomography (CT) of the left-sided T9 vertebral body osteoblastoma. (d) T2-WI magnetic resonance imaging of tumor’s proximity to aorta, lung, and cord. (e) Preoperative multiplanar osteotomy planning. Red cut – first-step transthoracic approach; blue cut – second-step posterior approach to release the tumor en bloc. (f-h) Postoperative CT images demonstrate complete tumor resection. Images i and j show surgical sample of tumor in the left posterolateral T8 vertebral body surrounded by the T7 and T8 rib heads and soft tissue.

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Figure 2:: (a) T2-WI coronal magnetic resonance imaging showing right-sided osteoblastoma and relationship to 4th right sacral foramen. (b and c) Sagittal and coronal computed tomography (CT) images of spinal primary bone tumors. (d) Planned preoperative multiplanar osteotomies through the blue, yellow and red lines, the green area is the tumor reconstruction. (e) Intraoperative navigation/registration. (f) Intraoperative image of the medial osteotomy/correlation with the navigated tracker. (g) En bloc resection of tumor. (h) Postoperative CT total tumor excision with structural graft.

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DISCUSSION

Several authors have reported the advantages of using navigation during uniplanar osteotomies for en bloc resections of SPBT with different imaging and cutting technologies.[1,3-6] Preoperative reconstruction of the SPBT allows surgeons to plan, in detail, en bloc resection with multiplanar osteotomies, and preserve nerve structures, reduce the volume of healthy bone resected, and preserve stability. Total en bloc vertebrectomy is recommended when resecting lesions that have invaded more than half of the VB.[4] Although there is no consensus regarding instrumentation after a partial vertebrectomy, VB resections of <25% are generally not instrumented, those 25–50% are usually reinforced with posterior stabilization [Figure 1], while for resections of >50% circumferential stabilization are typically recommended.[7]

The availability of computer-assisted surgery since 2010 has facilitated 3D planning of en bloc resections of primary bone tumors, particularly in performing accurate osteotomies with safe margins preserving healthy tissues [Figure 3].[8,9] The main disadvantage of this technique, however, is the lack of worldwide availability of this technology. Although we believe that implementing navigated multiplanar osteotomies for en bloc resection of SPBT could shorten surgical times and improve clinical outcomes, further studies must be conducted to confirm these beliefs.

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Figure 3:: Navigated multiplanar osteotomies for en bloc resection of spinal primary bone tumors. (a) Preoperative planning of patient 6, an S1 coccyx chondrosarcoma (G2), 3 cuts (blue, yellow, and red lines) were made. (b) Patient 8, a T8-T9 chondrosarcoma (G1), 4 cuts (pink, blue, purple, and light-blue) were made the yellow part represents the partial osteotomy area. (c) Patient 7, S1 coccyx chordoma, 4 cuts were planned (cyan, light-blue, blue, and red lines). (d) Patient 12, an S1 coccyx chordoma, 3 line-cuts were done (green, red, and blue). (e) Correspond to patient 5, a T2 osteoblastoma, 2 osteotomies were done (light-blue and blue lines), the purple area represent the ipsilateral hemi-laminectomy. (f) Patient 10, an S2 coccyx chordoma were 3 osteotomies were planned.

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CONCLUSION

Navigated multiplanar osteotomies increased the precision and safety of en bloc resections for 14 primary spinal bone tumors SPBT that included 11 malignant and three benign/locally aggressive lesions.