Sonic estimation of elasticity via resonance (SEER) sonorheometry is a novel technology that uses acoustic deformation of the developing clot to measure its viscoelastic properties and extract functional measures of coagulation. Multilevel spine surgery is associated with significant perioperative blood loss, and coagulopathy occurs frequently. The aim of this study was to correlate SEER sonorheometry results with those of equivalent rotation thromboelastometry (ROTEM) and laboratory parameters obtained during deformity correction spine surgery. Four independent SEER sonorheometry hemostatic indices (clot time, clot stiffness, fibrinogen, and platelet contribution) were measured. SEER sonorheometry clot time, using kaolin as an activator, was correlated with ROTEM intrinsic temogram clotting time and the activated partial thromboplastin time. For clot stiffness, thromboplastin was the primary activator, and this was correlated against ROTEM external temogram amplitude at 10 minutes (A10). The assay for the fibrinogen contribution was similar to clot stiffness, but abciximab was added to inhibit platelet function. The fibrinogen contribution assay was correlated with the ROTEM fibrinogen temogram A10. Finally, the SEER sonorheometry platelet contribution was calculated by subtracting the fibrinogen contribution from the clot stiffness. This variable was correlated with both absolute platelet counts, and ROTEM determined clot elasticity attributable to platelets. Fifty-one patients were enrolled in this prospective observational study. SEER sonorheometry clot stiffness, fibrinogen, and platelet contribution had a very strong correlation with ROTEM external temogram A10 (rs = .92; 99% confidence interval, .85-.96), fibrinogen temogram A10 (rs = .90; 99% confidence interval, .83-.93), and ROTEM-determined clot elasticity attributable to platelets (rs = .89; 99% confidence interval, .80-.95). SEER sonorheometry clot time exhibited moderate correlation with ROTEM intrinsic temogram clotting time (rs = .62; 99% confidence interval, .44-.77) and very weak correlation with activated partial thromboplastin time (rs = .33; 99% confidence interval, .10-.51). SEER sonorheometry demonstrates very strong correlation with ROTEM for determining clot stiffness and assessing fibrinogen and platelet contribution to clot strength in major spine surgery. An advantage of SEER sonorheometry is direct measurement of clot elasticity with no need to transform amplitude oscillation to elasticity.