P120. Risk factors for failure to achieve minimal clinically important difference following cervical disc replacement

Abstract

<h3>BACKGROUND CONTEXT</h3> Patient reported outcome measures (PROMs) and minimal clinically importance difference (MCID) thresholds have emerged as effective, reliable parameters to assess improvement and surgical success. <h3>PURPOSE</h3> To investigate the risk factors associated with failure to achieve MCID following cervical disc replacement (CDR). <h3>STUDY DESIGN/SETTING</h3> Retrospective review of prospectively collected data. <h3>PATIENT SAMPLE</h3> A total of 107 patients who had undergone primary, one-or-two level CDR by three surgeons at a single academic institution. <h3>OUTCOME MEASURES</h3> Patient-reported outcome measures - Rates of MCID achievement in neck disability index (NDI), VAS (visual analogue score) neck, and VAS-arm were calculated with the following threshold values, based on previously published studies: NDI: -15.0, VAS-neck: -2.5, and VAS-arm: -2.5. <h3>METHODS</h3> Risk factors for failure to achieve MCID were identified using multivariate logistic regression models with alternating backward stepwise elimination and forward entry of removed variables (entry: 0.05, removal: 0.10). Receiver operating characteristic (ROC) curves were generated to assess the performance of each model. <h3>RESULTS</h3> A total of 107 patients met inclusion criteria (mean age: 42.99±9. Thirteen years, mean BMI: 26.02±4.01 kg/m2). There were 99 patients who presented for a follow-up visit within three months of their operation, of which 82 (89.1%) had achieved MCID in NDI, VAS-neck, or VAS-arm. Specific to the NDI, BMI≥25 kg/m2 (OR:153.75, p=0.002), depression (OR:50.32, p=0.016), myelopathy (OR:51.44, p=0.022), degenerative disc disease/spondylosis (OR:21.54, p=0.001), and two-level procedures (OR:6.59, p=0.027) were identified as risk factors for failure to achieve MCID within the first three months. Preoperative narcotic use (OR:0.11, p=0.027) was associated with a lower risk for failure to achieve MCID in NDI within the first three months. The area under the ROC curve (AUROC) assessing the logistic regression model's performance was 0.873 (p<0.001), suggesting strong predictive ability. Overall, 103 patients had valid MCID calculations, of which 93 (90.3%) achieved MCID in NDI, VAS-neck, or VAS-arm at any time point (2 weeks, 6 weeks, 3 months, 6 months, or 1 year) following CDR. Depression (OR:18.21, p=0.022), myelopathy (OR:18.81, p=0.037), and two-level procedures were associated with failure to achieve MCID in NDI by the 1-year time point. The AUROC assessing model performance was 0.840 (p<0.001), demonstrating strong predictive ability. No significant risk factors were identified for failure to achieve MCID in VAS-neck and VAS-arm. <h3>CONCLUSIONS</h3> The large majority of patients had achieved MCID in at least one of the three PROMs. Clinical depression, myelopathy and two-level procedures were associated with failure to achieve MCID in NDI by one year and also within the early postoperative period (first three months) following CDR. BMI≥ 25 kg/m2 and spondylosis were also significant factors associated with failure to achieve MCID in NDI within the early postoperative period. Although preoperative narcotic use was associated with achievement of MCID in NDI, these patients likely presented initially with more chronic and severe symptoms, potentiating greater improvements in PROMs. Future studies with larger cohorts may provide additional insight on the true impact of the identified risk factors on outcomes following CDR. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.