Establishing Minimal Clinically Important Difference of Spinal Cord Stimulation Therapy in Post-Laminectomy Syndrome.

Abstract

The concept of minimum clinically important difference (MCID) has been shown to be effective in spine surgery to differentiate between clinically insignificant and significant improvements as determined by the patient. The MCID for spinal cord stimulation (SCS) to date has not been established. We sought to determine the MCID for SCS therapy for failed laminectomy syndromes. Preoperative and 6-mo outcomes were assessed prospectively, including the Oswestry Disability Index (ODI), Beck Depression Inventory (BDI), and McGill and Visual Analog Survey questionnaires. Patients were asked: (1) are you satisfied with SCS therapy and (2) would you have the surgery again. Four methods of calculating the MCID were utilized. Forty-eight patients who underwent placement of an SCS between 2012 and 2014 were reviewed. The 4 calculation methods yielded a range of outcome scores (ODI 8.2-13.3, BDI 3.2-7, McGill 0.3-1.3, and Visual Analog Scale [VAS] 1.2-3.7). The maximum area under the curve was observed for the ODI, BDI, and VAS (0.73, 0.81, and 0.89, respectively), which signifies acceptable accuracy in distinguishing responders from nonresponders with the receiver operating characteristic method and suggests that VAS may be the most sensitive in determining meaningful change for the patient. The MCID for SCS placement was calculated using 4 different methods. The results are similar to calculations for the MCID for many lumbar and cervical procedures done for pain. Our results suggest that an improvement of 1.2 to 3.7 points on the VAS scale and 8.2 to 13.3 points on the ODI is clinically meaningful to the patient. Further defining the MCID for SCS therapy will remain of utmost importance in order to justify the cost of the procedure.