1572. Factors Associated with Achieving a Clinically Significant Improvement in Patients Undergoing Minimally Invasive Lumbar Decompression Surgery

Authors: Avani Vaishnav; Catherine Gang, MPH; Sravisht Iyer, MD; Steven McAnany, MD; Todd Albert, MD; Sheeraz Qureshi, MD, MBA (New York, NY)

Background: 
Surgical decompression is an effective procedure for patients with lumbar spinal stenosis who fail conservative management. While this procedure has demonstrated benefit at the population level, improvement at the individual level remains highly variable. 

Purpose: 
To determine demographic factors, surgical variables and pre-operative patient-reported outcome(PROs) associated with achieving an improvement >Minimum Clinically Important Difference(MCID) by 3 months post-operatively in patients undergoing minimally invasive lumbar decompression surgery.

Methods: 
Patient demographics, operative details and PROs [Oswestry Disability Index(ODI), Visual Analog Scale(VAS)-back and leg pain, Short Form-12 Physical and Mental Health Scores(SF-12 PHS and MHS) and PROMIS Physical Function Scores] collected pre-operatively and at each follow-up were analyzed.

MCID of 12.8 for ODI was used to assess whether patients had a clinically significant improvement. Individual logistic regressions were conducted for each predictive variable; variables with p<0.1 were included in a multiple logistic regression, with step-wise elimination, to identify factors associated with improvement >MCID by 3 months.

Results:
A total of 93 patients, with a mean age of 55 years were included. 53.3% of patients experienced an improvement >MCID by 2 weeks, 56.5% by 6 weeks and 64.5% by 3 months.

Individual regressions showed age(p<0.001), pre-operative VAS leg pain(p=0.007), pre-operative ODI(p=0.001) and pre-operative SF-12 MHS(p=0.027) to be significant predictors of improvement >MCID by 3 months. In the multiple regression(p<0.0001), younger age[OR:0.943,p<0.001) and higher pre-operative ODI[OR:1.046,p=0.008) were the only significant predictors. The model explained 40.8%(Nagelkerke R2) of the variance in whether patients had a clinically significant improvement and correctly classified 80.6% of cases.

Conclusion: 
These results show that age and pre-operative ODI are associated with patients experiencing a clinically significant improvement. These findings can be used to pre-operatively identify patients who may experience a longer recovery and counsel them appropriately. Larger studies are warranted to identify additional factors associated with patient recovery.