The spinal column is the most common site for skeletal metastasis, with treatment options including analgesics, radiotherapy, chemotherapy, hormonal therapy, and surgery^15,22). Decompression and surgical stabilization with instrumentation is a well-established method for managing spinal metastasis⁸⁾. Various surgical strategies have been proposed, including decompression with stabilization, with or without the removal or reconstruction of the entire tumor²⁶⁾.

The primary benefits of surgery include rapid decompression of spinal neural structures, the possibility of reconstructing and stabilizing the bony spine, and maintaining patient mobility, thereby improving the quality of life^11,23).

While fusion's benefits are well-known in degenerative conditions, its necessity and feasibility in spinal metastatic disease are less certain. A major concern is the limited survival time in this population, which is potentially insufficient for fusion to occur. Although advancements in systemic therapies have extended survival in select cancers such as non-small cell lung cancer and renal cell carcinoma, large studies continue to show a median survival of 12 months or less^{6,9,12,16,27)}.

Our estimate of a median survival of 11 months aligns with this literature. Furthermore, fusion may be hindered by factors such as poor nutritional status, radiotherapy, and chemotherapy²⁹⁾.

Thus, this study aims to analyze acute complications in patients who underwent instrumented spinal surgery for spinal metastatic disease.

We conducted a retrospective analysis of spinal surgeries performed on patients with spinal metastasis by two spinal neurosurgeons at a single tertiary academic medical center between April 2021 and October 2024. A total of 35 consecutive patients (26 males, 9 females) with a mean age of 66.5 ± 10.2 years (range, 44-85) were included. In this study, patients who underwent only simple decompression were excluded, and data analysis was limited to patients who had fusion surgery.

Patients were followed up for at least six months post-surgery. Assessments involved standing upright flexion/extension radiographs, computed tomography, and magnetic resonance imaging scans. Clinical symptoms were correlated with radiologic findings to determine the need for surgery.

Surgical candidates presented with neurological deficits due to tumor compression of the spinal canal, supported by physical and radiologic evaluations. All patients experienced significant pain or disability, including radiculopathy, lower extremity weakness, or axial pain from spinal tumor metastasis.

Tumor origins were categorized by affected organ (e.g., lung, prostate, liver, kidney, colorectum, stomach, breast, ureter, and bladder).

The immediate postoperative period was defined as the first 30 days after surgery, and complications within this timeframe were analyzed. Lower extremity motor function was assessed using manual muscle testing (MMT) and neurologic examinations documented in the database.

The demographic characteristics of the study population are shown in Table 1. The average patient age was 66.5 ± 10.2 years (range, 44-85), with 26 males. The mean number of operated levels was 4.1 ± 2.0 (range, 1-10). The thoracic spine was the most commonly treated region (60%), followed by the thoracolumbar spine (17.1%).

Motor function improved post-surgery, with MMT increasing from 2.6 ± 1.3 to 3.5 ± 1.3, representing an average improvement of 0.8 ± 0.8 (p < 0.05). Surgery was performed due to lower extremity weakness in all cases, with 59% showing motor improvement, and 23% regaining the ability to walk.

Lung cancer (34%) and prostate cancer (17%) were the most frequent primary cancers, followed by liver, colon, and others (Table 2). The overall complication rate was 37%, consisting of 14% surgery-related complications and 23% general complications (Table 3).

One patient experienced an acute mechanical complication after undergoing a corpectomy for a C6 tumor metastasis, resulting in mechanical failure and cage subsidence 14 days post-surgery (Fig. 1).

Other surgery-related complications included cerebrospinal fluid leak, surgical site infection, and hematoma. The most common general complication was pneumonia, followed by bowel obstruction, pleural effusion, and electrolyte imbalance.

While fusion is well-established for degenerative conditions, its necessity in spinal metastatic disease is less certain due to the limited survival of these patients. Implant failure rates following surgery for spinal metastases range from 2% to 8%, and not all cases require revision surgery. Fusion may also be compromised by factors like poor nutritional status, radiotherapy, and chemotherapy^{1,4,7,14,18,20)}.

Pedreira et al.²⁰⁾ reported that 1.9% of patients who underwent resection of metastatic spinal lesions experienced implant failure requiring revision surgery, particularly those who received prior radiotherapy. However, Wong et al.²⁸⁾ found no association between radiotherapy and implant failure.

Patchell et al.¹⁹⁾ demonstrated that direct decompressive surgery combined with radiotherapy allows patients with metastatic spinal cord compression to retain or regain mobility more effectively than radiotherapy alone. Surgery enables many patients to remain ambulatory for the remainder of their lives, while radiation-only patients often become paraplegic.

General complications, rather than mechanical complications, are also significant challenges. Although spinal surgeons strictly examine the indication of surgery and surgical methods for spinal metastases, considering the expected prognosis, age, and comorbidity of patients, the operative morbidity and the 30-day mortality have been reported to be 26% to 34% and 3% to 9%, respectively^2,10,21), which are much higher than what is observed after general spinal surgery. Accordingly, knowing the risk factors of short-term perioperative mortality as well as long-term life expectancy is important.

Factors for predicting survival after surgical treatment or surgical complications have been reported in several studies^5,17) It is generally known that the type of primary tumor and the presence of visceral metastases and performance status are significant predictors of survival after surgery.

There are also several scoring systems designed to predict the life expectancy of patients with bone metastasis and select the type of surgery. However, these studies were performed with relatively small sample sizes and focused on long-term survival. Factors affecting short-term perioperative mortality after surgery for spinal metastasis have not been well described^3,13,24,25).

In our study, the overall complication rate was 37%, with 23% being general complications. This is relatively high compared to other reported 30-day mortality data. In our study, the most frequent primary cancer was lung cancer (34%), and this likely contributed to the higher rate of pneumonia, which accounted for a significant portion of the general complications.

The limitations of this study include a relatively small sample size and its retrospective nature, which may introduce selection bias. Additionally, the lack of long-term follow-up limits the understanding of delayed complications and overall outcomes. The study also does not account for variations in treatment protocols, tumor types, or preoperative general conditions (e.g., Karnofsky Performance Scale), which could influence complication rates and outcomes. Lastly, the focus on a single institution may reduce the generalizability of the findings to other settings or populations.

Surgery for spinal metastasis is often necessary for tumor removal, neural decompression, and stabilization of the spine. In cases where symptoms such as paralysis occur, emergency surgery may also be required. Although there is a risk of acute complications, the procedure shows significant benefits, including improvement in weakness and recovery of walking ability. Thus, a more comprehensive approach with the use of suitable surgical techniques is recommended.