Is there a correlation between the spinal instability neoplastic score and mechanical pain in patients with metastatic spinal cord compression? A prospective cohort study.

INTRODUCTION: The decision for selecting patients for surgical treatment of metastatic spinal cord compression (MSCC) is challenging even for experienced surgeons. Recently, the spinal instability neoplastic score (SINS) has been proposed to help surgeons in the evaluation of spinal stability in the setting of spinal metastases. This study aimed to evaluate the correlation between SINS and preoperative visual analog scale (VAS), as well as the pre- and post-operative association of the VAS and neurological function.

METHODS: A prospective cohort study was conducted in a tertiary referral cancer center. Seventy-nine patients with MSCC were surgically treated from June 2012 to March 2015. Pain status before and after surgery was assessed using VAS score, and neurological status was evaluated using the American Spine Injury Association Impairment Scale (AIS) before and after surgery. Pain was classified as VAS (0-4) none or mild pain; VAS (5-8) moderate pain; and VAS (9-10) as severe pain. Neurological function was scored as AIS A: Complete deficits, AIS B-D: Incomplete deficits, AIS E: Neurologically intact. SINS degrees were classified as 0-6-stable; 7-12 potentially unstable, and 13-18-unstable. Spearman's correlation coefficient test was utilized for correlation between pain and SINS; Chi-square association test was utilized for evaluating pre- and post-operative pain and AIS, as well as the association between SINS and tumor types.

RESULTS: A higher SINS correlates with severe mechanical pain preoperatively (ρ = 0.38, P = 0.001); surgical procedure improved neurological function ( P = 0.0001), and decrease pain ( P = 0.84). Finally, a higher SINS was also associated with osteolytic tumors ( P = 0.03).

CONCLUSIONS: The SINS correlates with mechanical pain. Surgery provides a significant improvement in pain and neurological status, especially in patients who presented higher SINS scores and some degree of preoperative neurological function.