Risk Factors Associated With Failure to Reach Minimal Clinically Important Difference in Patient-Reported Outcomes Following Anterior Cervical Discectomy and Fusion Ankur S. Narain, Fady Y. Hijji, Benjamin Khechen, Brittany E. Haws, Dil V. Patel, Daniel D. Bohl, Kelly H. Yom, Krishna T. Kudaravalli and Kern Singh Int J Spine Surg published online 8 July 2019 http://ijssurgery.com/content/early/2019/07/08/6035 This information is current as of September 27, 2021. Email Alerts Receive free email-alerts when new articles cite this article. Sign up at: http://ijssurgery.com/alerts The International Journal of Spine Surgery 2397 Waterbury Circle, Suite 1, Aurora, IL 60504, Phone: +1-630-375-1432 © 2019 ISASS. All RightsDownloaded Reserved. from http://ijssurgery.com/ by guest on September 27, 2021 International Journal of Spine Surgery Publish Ahead of Print, published on July 8, 2019 as doi:10.14444/6035 International Journal of Spine Surgery, Vol. 00, No. 00, 0000, pp. 000–000 https://doi.org/10.14444/6035 ÓInternational Society for the Advancement of Spine Surgery Risk Factors Associated With Failure to Reach Minimal Clinically Important Difference in Patient-Reported Outcomes Following Anterior Cervical Discectomy and Fusion ANKUR S. NARAIN, BA, FADY Y. HIJJI, MD, BENJAMIN KHECHEN, BA, BRITTANY E. HAWS, BS, DIL V. PATEL, BS, DANIEL D. BOHL, MD, MPH, KELLY H. YOM, BA, KRISHNA T. KUDARAVALLI, BS, KERN SINGH, MD Department of Orthopaedic Surgery, Rush University Medical Center, 1611 West Harrison Street, Suite #300, Chicago, IL 60612 ABSTRACT Background: The minimum clinically importance difference (MCID) represents a threshold for improvements in patient-reported outcomes (PROs) that patients deem important. No previous study has comprehensively examined risk factors for failure to achieve MCID after anterior cervical discectomy and fusion (ACDF) procedures for radiculopathic symptomatology. The purpose of this study is to determine risk factors for failure to reach MCID for Neck Disability Index (NDI), Visual Analog Scale (VAS) neck pain, and VAS arm pain in patients undergoing 1- or 2-level ACDF procedures. Methods: A surgical registry of patients who underwent primary, 1- or 2-level ACDF from 2014 to 2016 was reviewed. Rates of MCID achievement for NDI, VAS neck pain, and VAS arm pain at final follow-up were calculated based on published MCID values. Patients were then categorized into demographic and procedural categories. Bivariate regression was used to test for association of demographic and procedural characteristics with failure to reach MCID for each PRO. The final multivariate model including all demographic and procedural categories as controls was created using backward stepwise regression. Results: Eighty-three, 84, and 77 patients were included in the analysis for VAS neck, VAS arm, and NDI, respectively. Rates of MCID achievement for VAS neck, VAS arm, and NDI were 55.4%, 36.9%, and 76.6%, respectively. On bivariate analysis, patients with Charlson Comorbidity Index (CCI) 2 were less likely to achieve MCID for NDI than patients with CCI , 2(P ¼ .025). On multivariate analysis, CCI 2(P ¼ .025) was further associated with failure to reach MCID for NDI. Conclusions: The results of this study suggest that the majority of patients do not reach MCID for arm pain. Additionally, higher comorbidity burden as evidenced by higher CCI scores is a negative predictive factor for the achievement of MCID in neck disability following ACDF. Level of Evidence: 3 Cervical Spine Keywords: anterior cervical discectomy and fusion, minimal clinically important difference, Visual Analog Scale, neck pain, arm pain, Neck Disability Index, Charlson Comorbidity Index INTRODUCTION tive changes in disability and pain after spinal surgery are measured using patient reported out- Cervical radiculopathy is a common symptom of comes (PROs). Neck disability index (NDI), visual cervical disc degeneration. For patients experienc- analog scale (VAS) neck pain, and VAS arm pain ing symptoms that are unresponsive to conserva- are common PROs used in determining the effec- tive therapy, anterior cervical discectomy and tiveness of cervical spine surgery.7 The minimum fusion (ACDF) is a reliable surgical management clinically important difference (MCID) is a com- 1–3 option. monly used threshold value for PRO changes that ACDF has demonstrated a high success rate in represents changes that patients and clinicians are relieving neck and arm pain, with patient-reported likely to consider clinically meaningful.8 The most satisfaction rates approaching 96%.4–6 Postopera- widely accepted method of calculating MCID is the Downloaded from http://ijssurgery.com/ by guest on September 27, 2021 Copyright 2019 by International Society for the Advancement of Spine Surgery. ACDF MCID Risks anchor-based approach, in which patient-perceived be tested as independent variables in subsequent improvements are compared to PROs following analyses. surgery, allowing for the establishment of clinically important scoring benchmarks.9 PRO Analysis Previous studies have identified risk factors for PRO questionnaires were completed preopera- decreased PRO improvement after ACDF based on tively and at 6-week, 12-week, 6-month, and 1-year 10–13 absolute PRO score differences. However, few postoperative time points. PROs measured included studies have assessed risk factors associated with NDI, VAS neck pain, and VAS arm pain scores. failure to reach MCID for PROs after ACDF. The NDI is comprised of 10 questions, each scored from purpose of this study is to evaluate risk factors for 0 to 5 points, and measures functional disability failure to reach MCID for NDI, VAS neck pain, associated with neck pain and is reported as a and VAS arm pain in patients undergoing 1- or 2- percentage of the total possible score (50 points).15 level ACDF procedures for radiculopathic pathol- Higher NDI scores are associated with greater ogy. disability. VAS neck and VAS arm assess pain in their specific anatomic region on a scale of 0 (no MATERIALS AND METHODS pain) to 10 (maximum pain).16 Rates of MCID achievement for NDI, VAS neck, Patient Population and VAS arm were calculated at 6-month or 1-year A prospectively maintained surgical database of postoperative follow-up. MCID values were adapt- patients who underwent primary, 1- or 2-level ed from a study by Parker et al9 in which anchor- ACDF for degenerative pathology between 2014 based approaches were utilized. The authors used a and 2016 was reviewed following institutional North American Spine Society patient satisfaction review board approval (ORA#14051301). All pa- questionnaire as the anchor. The choices provided tients presented with radiculopathy including motor were (1) ‘‘The treatment met my expectations,’’ (2) weakness or sensory loss. A single surgeon per- ‘‘I did not improve as much as I had hoped, but I formed all procedures at an academic institution. would undergo the same treatment for the same Patients were excluded from the analysis if preop- outcome,’’ (3) ‘‘I did not improve as much as I had erative PRO survey data were incomplete or if they hoped, and I would not undergo the same treatment did not have minimum 6-month clinical follow-up. for the same outcome,’’ and (4) ‘‘I am the same or worse than before treatment.’’ Patients answering Surgical Technique choice 1 were categorized as responders, while those answering the other choices were considered nonre- Patients underwent routine ACDF utilizing the 14 sponders. The authors used a minimum detectable Smith-Robinson approach. An interbody cage change approach for calculating MCID, which was prepared with local autograft and bone graft defines MCID as the smallest change that is above substitute for insertion into the intervertebral space. the measurement error with a given confidence level. This method provided a threshold above the 95% Patient Demographics confidence interval of the unimproved patients while Patients were categorized based on demographic also being closest to the mean change score reported and procedural characteristics. Demographic cate- by the improved patients. Thus, MCID values were gories included age (18–50, .50 years), sex (female established for NDI, VAS neck, and VAS arm at 9 or male), body mass index (BMI) (,30, 30 kg/m2), À17.3%, À2.6, and À4.1, respectively. insurance status (workers’ compensation, other), smoking status (current smoker, nonsmoker), and Statistical Analysis and Determination of Charlson comorbidity index (CCI) (,2, 2). Risk Factors Operative characteristics included operative dura- Statistical analysis was performed using Stata/ tion (50, .50 minutes), number of operative levels MP 13.1 for Mac (StataCorp LP, College Station, (1 level, 2 levels), and the incidence of intraoperative Texas). To determine if risk factors for failure to or postoperative medical or surgical complications. achieve MCID were present, bivariate and multi- Of note, a modified CCI was utilized with the age variate Poisson regression with robust error vari- component excluded such that age and CCI could ance was used to test for an association between Downloaded from http://ijssurgery.com/ by guest on September 27, 2021 International Journal of Spine Surgery, Vol. 00, No. 00 0 Narain et al. Table 1. Patient-reported outcomes. tions occurred within the investigated patient cohort Parameter Mean 6 SD up to 6 months postoperatively. As such, the VAS neck (N ¼ 83) incidence of perioperative or postoperative compli- Preoperative 6.0 6 2.4 cations was not included in any subsequent bivariate Final follow-up 3.2 6 2.6 D at final follow-up À2.9 6 3.0 or multivariate analyses. VAS arm (N ¼ 84) A total of 55.4% (46/83) of patients achieved Preoperative 5.7 6 2.6 Final follow-up 2.8 6 2.7 MCID for neck pain VAS at final postoperative D at final follow-up À3.0 6 3.3 follow-up (Table 2). No demographic or procedural NDI score (N ¼ 77) Preoperative 40.3 6 18.5 factors were associated with failure to reach MCID Final follow-up 22.9 6 19.1 on bivariate analysis.