Total
The medical records of 19 patients who underwent TES (9 for primary tumors and 10 for metastatic tumors) were retrospectively reviewed. Previously reported surgical techniques were used, and the surgical extent was 1 level in 16 patients and 2 levels in 3 patients. A titanium-based mesh-type interbody spacer filled with autologous and cadaveric bone was used for anterior support, and a pedicle screw/rod system was used for posterior support. Radiotherapy was performed in 11 patients (pre-TES, 5; post-TES, 6). They were followed up for 59 ± 38 months (range, 11–133 months).
During follow-up, 8 of 9 primary tumor patients (89%) and 5 of 10 metastatic tumor patients (50%) survived (mean survival time, 124 ± 8 months vs. 51 ± 13 months; p=0.11). Mechanical failure occurred in 3 patients (33%) with primary tumors and 2 patients (20%) with metastatic tumors (p=0.63). The mechanical failure-free time was 94.4 ± 14 months (primary tumors, 95 ± 18 months; metastatic tumors, 68 ± 16 months; p=0.90). Revision surgery was performed in 4 of 5 patients, and bilateral broken rods were replaced with dual cobalt-chromium alloy rods. Repeated rod fractures occurred in 1 of 4 patients 2 years later, and the third operation (with multiple cobalt-chromium alloy rods) was successful for over 6 years.
Considering the difficulty of reoperation and patients’ suffering, preemptive use of a multiple-rod system may be advisable.
Total
Initially, mechanical failure was reported in approximately 5% of patients after TES, but it rarely occurred after the introduction of titanium-based mesh-type vertebral spacers [
Mechanical failure was not an uncommon complication, but it was not sufficiently addressed. The objective of this study was to present the incidence and case of mechanical failure and to suggest strategies for salvage surgery. Although the present study was based on experiences at a single institution, we intended to highlight the issue and share the experience of mechanical failure after TES.
Nineteen consecutive patients (9 with primary tumors, 10 with metastatic tumors) who underwent TES for primary or metastatic tumors from July 2011 to April 2018 were retrospectively reviewed. TES was indicated for intracompartmental primary tumors or solitary intracompartmental metastatic tumors. Two patients underwent TES for a recurrent primary tumor, and the other patients underwent TES for their first surgical procedure. Two patients with recurrent tumors underwent intralesional resection and radiotherapy 1 year and 6 months before, respectively, and they were referred for recurrent primary tumors (giant cell tumor [GCT] and chondroblastoma). The primary tumors were 6 GCTs, 2 chondroblastomas, and 1 osteosarcoma. Among the patients with metastatic tumors, the primary organs were the kidney in 3 patients, the cervix in 2, the liver in 2, the lung in 2, and the thyroid in 1 (
The surgical principles and techniques of TES were the same as those reported [
Patients were scheduled to visit the clinic at postoperative months 1, 3, 6, and 12 and yearly thereafter. At each visit, patients were asked to undergo a plain x-ray to check for mechanical failure, and a computed tomography (CT) scan was performed at 6 months to confirm bony fusion. If solid bony fusion was not visible, the CT scan was planned to be repeated 6 months later and yearly thereafter. For patients with metastatic tumors, the abovementioned schedule was not followed when the chest or abdominal CT scans taken by medical/radiation oncologists were available, and reconstructed coronal or sagittal scans were referenced to evaluate bony fusion. Bony bridging across the spondylectomy site was considered fusion. Asymptomatic mechanical failure was closely observed every 3 months with x-rays, while cases of symptomatic failure underwent reoperation.
Continuous variables are presented as the mean ± standard deviation, and noncontinuous values are presented as numbers and proportions. Categorical data were compared using the chi-square test, and quantitative data were compared using the Mann-Whitney U-test. The survival time, mechanical failure-free time, and time to bony fusion were compared between primary and metastatic tumors using Kaplan-Meier survival analysis and the log-rank test. All statistical analyses were performed using IBM SPSS Statistics ver. 23.0 (IBM Co., Armonk, NY, USA), and a p-value less than 0.05 was considered to indicate statistical significance.
All surgeries were finished without neurological complications. Two patients developed chylothorax, which was controlled with a chest tube and lipid-free diet for 1 week. Any other complications, such as surgical site infection, hematoma collection, or deep vein thrombosis, did not occur. The preoperative treatment was radiotherapy in 5 patients (2 with primary tumors and 3 with metastatic tumors) and conventional chemotherapy in 2 patients with metastatic tumors. Postoperative radiotherapy was performed for 6 patients (1 with a primary tumor and 5 with metastatic tumors) 3 weeks after TES because the tumor involved the bilateral pedicles (n=1) or there was a concern regarding microscopic tumor contamination despite the use of a thread saw to cut the lamina and pedicle (n=5). Two patients with metastatic cancer showed tumor recurrence at postoperative 6 months. One patient with a GCT experienced a malignant transformation of the GCT at postoperative months 69. During the follow-up period, 8 of 9 patients (88.9%) with primary tumors and 5 of 10 patients (50%) with metastatic tumors survived, with mean survival times of 124±8 months and 51±13 months, respectively (p=0.11). Solid bony fusion was achieved in 56% (5 of 9) of primary tumors at a mean of 43±9 months and 6 of 10 (60%) of metastatic tumors at a mean of 20±5 months. Time to fusion was not different between primary and metastatic tumors (p=0.19). A mechanical failure occurred in 3 patients (33%) with primary spinal tumors and 2 patients (20%) with metastatic spinal tumors (p=0.63) during the follow-up period. Fracture of the rod occurred in 3 patients with primary tumors and 1 patient with metastatic tumors. Subsidence of MESH cage occurred in 1 patient with metastatic tumor. A mechanical failure occurred in 27% (3 of 11) of patients with the bony union and 25% (2 of 8) of patients without bony union (p=0.91) (
The risk factors for mechanical failure were analyzed. A mechanical failure occurred more frequently in patients who received radiotherapy (4 of 11, 36%) than in patients who did not receive radiotherapy (1 of 7, 13%), but the difference was not statistically significant (p=0.24). Other factors, including fusion status and sex, did not show statistical significance.
A 23-year-old man presented with back pain and was diagnosed with GCT at T6 and T7 (
Because of the proximity of the spinal cord, wide or marginal resection of spinal tumors is a challenging surgical option. Due to this issue, Weinstein, Boriani, and Biagini (the WBB system) and Tomita et al. suggested staging systems for the proper application of TES [
One of the major issues after TES is the reconstruction of the spinal column. Solid bony fusion has been established as the most important factor to prevent mechanical failure when the 3 spinal columns are destabilized [
Nonetheless, several recent reports have presented results on mechanical failure after TES, such as screw loosening, screw back-out, cage breakage, screw fracture, and rod fracture; these studies identified rod fracture as the most common type of failure, and it often led to reoperation [
The causes of rod fracture varied, and radiotherapy and surgery at the lumbar spine were common causes [
When mechanical failure occurs, the surgical strategy may vary. Although adding strong anterior support with an anterior approach could be a solution, it has a high risk of approach-related complications. Instead, previous studies have suggested posterior revision surgery using multiple rods and an additional bone graft as an option [
Although this study underscored the possibility of mechanical complications after challenging TES, it has several limitations. First, this study included only a small number of patients treated in a single institution and may have been affected by selection bias, type I error, and type II error. Most importantly, the number of patients in this study was too small to draw any strong suggestions. Although the surgical procedures were in accordance with previous studies, the large difference in the rate of mechanical failure among several papers merits further attention. Second, although we recommended using a multiplerod system for patients expecting a long survival period, especially in revision surgery, this suggestion is not based on strong evidence [
The occurrence of mechanical failure after TES was a major cause of revision surgery. It could occur even after following a standard surgical technique: the use of anterior support and a pedicle screw/rod system. Considering the difficulty of reoperation and patients’ suffering, the preemptive use of a multiple-rod system may be advisable, especially for patients expecting a long survival duration. Further studies are required for the efficient use of limited resources.
The authors have nothing to disclose.
This work was supported by the New Faculty Startup Fund from Seoul National University. This study was supported by grant from Seoul National University Hospital research fund (grant No. no. 04-2021-0540).
Conceptualization: CKC, SBP, SHY, CHL, JR, KK, CHK; Data curation: SWK, YI, WTY, CHK; Formal analysis: CHK; Funding acquisition: CHK; Methodology: CHK; Project administration: CHK; Visualization: CHK; Writing - original draft: SWK, CHK; Writing - review & editing: CKC, YI Won, WTY, SBP, SHY, CHL, JR, KK, CHK.
Reconstruction of 3 columns after total
Event-free time for survival and mechanical failure. The survival curves represent the survival time and mechanical failure-free time for both primary and metastatic tumors. Although statistical significance was not reached, the survival time (124 ± 8 months) was longer than the mechanical failure-free time (95 ± 18 months) in primary tumors.
Total
Characteristics of patients
Characteristic | Primary (n = 9) | Metastasis (n = 10) | Total (n = 19) |
---|---|---|---|
Age (yr) | 29 ± 10 | 58 ± 6 | 44 ± 17 |
Female sex | 5 | 3 | |
Pathology | |||
Giant cell tumor | 6 | - | |
Chondroblastoma | 2 | - | |
Osteosarcoma | 1 | - | |
Kidney |
- | 3 | |
Cervix |
- | 2 | |
Liver |
- | 2 | |
Lung |
- | 2 | |
Thyroid |
- | 1 | |
Surgical level | |||
Thoracic spine | 5 | 10 | 15 |
Lumbar spine | 4 | - | 4 |
Surgical extent | |||
1 Level | 7 | 9 | 16 |
2 Levels | 2 | 1 | 3 |
Revision number | |||
0 | 6 | 9 | 15 |
1 | 2 | 1 | 3 |
2 | 1 | 0 | 1 |
Overall radiotherapy | 3 | 8 | 11 |
Preoperative radiotherapy | 2 | 3 | 5 |
Postoperative radiotherapy | 1 | 5 | 6 |
Primary site of metastatic tumor.
Treatment outcome
Primary (n = 9) | Metastasis (n = 10) | Bony union (n = 11) | Nonunion (n = 8) | |
---|---|---|---|---|
Bony union | 5 (56) | 4 (40) | - | - |
Mechanical failure | 3 (33) | 2 (20) | 3 (27) | 2 (25) |
Perioperative RT | - | - | 8 (73) | 3 (38) |
Values are presented as number (%).
RT, radiation therapy.