Risk Factors for MCID Drop-Off in Patients Undergoing Anterior Cervical Discectomy and Fusion

Abstract

Background Some patients may achieve a minimum clinically important difference (MCID) at an early postoperative time point, but these are not always retained long-term. We aim to characterize risk factors for regressing below a level of meaningful improvement in patients who had previously achieved an MCID following anterior cervical discectomy and fusion (ACDF). Methods A prospectively maintained surgical database was retrospectively reviewed for ACDF procedures. PROMs including visual analogue scale (VAS), Neck Disability Index (NDI), 12-Item Short Form Physical Component Summary (SF-12 PCS), Patient-Reported Outcomes Measurement Information System physical function (PROMIS PF), and Patient Health Questionnaire-9 (PHQ-9) were administered at preoperative and postoperative time points. MCID achievement was assessed by comparing postoperative improvements in PROM scores from preoperative baseline to the previously established threshold values. Results A total of 351 ACDF patients were included: 204 patients underwent single level procedures and 147 underwent multi-level ACDF. The greatest proportions of patients achieved MCID for VAS neck at 6-months (56.3%), VAS arm at 6-months (38.5%), NDI at 6-months (68.1%), SF-12 PCS at 6-months (45.1%), and PROMIS-PF at 1-year (69.0%) Significant predictors for MCID drop-off were: Preoperative PHQ-9 (RR 1.1, p=0.011) , smoker status (RR 2.2, p=0.038) and preoperative VAS arm (RR 1.2, p=0.001) for VAS arm , none for NDI, and BMI (RR 1.1, p=0.006) for PROMIS PF. Conclusion Highest rates of MCID achievement were 6-months following ACDF. Higher BMI, greater preoperative arm pain, smoking, and depression identified as significant risk factors for MCID drop-off for various PROMs. Male sex and anterior cervical plating were factors against regression of previously attained MCID for SF-12 PCS and VAS neck, respectively. Understanding the relationship between preoperative risk-inducing and protective variables for MCID drop-off may allow for earlier management of modifiable risk factors to maintain long-term clinical benefits following ACDF. Discussing factors influencing MCID drop-off with patients may allow for better matching of expectations among provider and patient and ultimately lead to improved satisfaction.