Impact of Spinal Instrumentation on Neurological Outcome in Patients with Intermediate Spinal Instability Neoplastic Score (SINS)

Simple Summary Spinal epidural metastases are a common complication of malignancies that can compromise spinal stability and subsequently lead to neurologic deficits in addition to pain and overall reduced quality of life, often requiring spinal instrumentation. The spinal instability neoplastic score is an instrument used to evaluate spinal stability; a stable situation is assumed in cases of a SINS below 7 and instability in cases of a SINS above 12, but there is uncertainty in SINS 7 to 12. Our aim was to evaluate the benefit of spinal instrumentation in these cases in terms of neurological function in order to improve patient treatment. Background: Adequate assessment of spinal instability using the spinal instability neoplastic score (SINS) frequently guides surgical therapy in spinal epidural osseous metastases and subsequently influences neurological outcome. However, how to surgically manage 'impending instability' at SINS 7-12 most appropriately remains uncertain. This study aimed to evaluate the necessity of spinal instrumentation in patients with SINS 7-12 with regards to neurological outcome. Methods: We screened 683 patients with spinal epidural metastases treated at our interdisciplinary spine center. The preoperative SINS was assessed to determine spinal instability and neurological status was defined using the Frankel score. Patients were dichotomized according to being treated by instrumentation surgery and neurological outcomes were compared. Additionally, a subgroup analysis of groups with SINS of 7-9 and 10-12 was performed. Results: Of 331 patients with a SINS of 7-12, 76.1% underwent spinal instrumentation. Neurological outcome did not differ significantly between instrumented and non-instrumented patients (p = 0.612). Spinal instrumentation was performed more frequently in SINS 10-12 than in SINS 7-9 (p < 0.001). The subgroup analysis showed no significant differences in neurological outcome between instrumented and non-instrumented patients in either SINS 7-9 (p = 0.278) or SINS 10-12 (p = 0.577). Complications occurred more frequently in instrumented than in non-instrumented patients (p = 0.016). Conclusions: Our data suggest that a SINS of 7-12 alone might not warrant the increased surgical risks of additional spinal instrumentation.