Elevated Patient Body Mass Index Does Not Negatively Affect Self-reported Outcomes Of Thoracolumbar Surgery: Results Of A Comparative Observational Study With Minimal 1-year Follow Up

Presented at SMISS Annual Forum 2014
By Neil A. Manson MD, FRCSC
With Alana J. Green BAH, Edward P. Abraham MD, FRCSC,

Disclosures: Neil Manson MD, FRCSC A; Unrestricted Research Grant, $85,000/annum, Medtronic Canada. B; Education Fees, Medtronic Canada. Alana Green BAH None, Edward Abraham MD, FRCSC A; Unrestricted Research Grant, $85,000/annum, Medtronic Canada. B; Education Fees, Medtronic Canada.,

Introduction:
As rates of obesity in North America continue to escalate, the demand for surgical care for these patients is increasing. Obesity may present a major burden to the prevalence of spinal pathologies, the challenges of spinal surgery and the potential for surgical success. Understanding the relationship between elevated body mass index (BMI) and surgical success is imperative to informing patients, surgeons and payers.

Aims/Objectives:
To evaluate the influence of elevated patient BMI on patient-reported outcomes following elective thoracolumbar spine surgery.

Methods:
This was a single-center ambispective cohort study. We identified 500 consecutive patients 18 years of age or older receiving lumbar spine surgery to treat degenerative pathologies. Minimum follow up was set at 1-year (average: 21-months). Primary measures consisted of pre-vs post-operative Numerical Rating Scale for Back and Leg Pain (NRS-B; NRS-L), Oswestry Disability Index (ODI), Short Form 36 Physical and Mental Component Summaries (SF-36 PCS; SF-36 MCS) and Satisfaction Scores. Secondary measures included adverse events, post-operative emergency department use, re-admission and re-operation. Patients were grouped based on BMI: morbidly obese (BMI ≥35,n=100), obese (BMI 30-34.99,n=113), overweight (BMI 25-29.99,n=180) and normal weight (≤24.99,n=107). Group differences in primary outcome measures were analyzed while controlling for multiple demographic and surgical variables, including surgical approach (MISS vs. Open). Patient demographics, peri-operative data and secondary outcome measures were also analyzed in relation to BMI group.

Results:
Mean BMI measured 29.67kg/m2, reflecting a significant level of obesity. All groups demonstrated statistically significant improvement in all outcome measures from before surgery to final follow up (Mean(SD) - SF-36 PCS:10.48(10.37); SF-36 MCS:6.47(12.86); ODI:-22.35(20.28); NRS-B:-3.68(2.88); NRS-L:-4.15(3.27); satisfaction:74.9% satisfied, 16.5% neutral, 8.6% dissatisfied). However, contrary to our hypothesis, BMI was not associated with the degree of change for any measure. Morbidly obese patients presented to the ER for pain-related complaints significantly more frequently. Otherwise, no between group differences were identified in the secondary measures.

Conclusions:
Patient-reported outcomes were significantly improved following thoracolumbar spine surgery regardless of BMI. Positive outcomes occurred with minimal effect on complications in both Open and MISS approaches. Based on these findings, BMI alone may not be an appropriate discriminator in surgical decision-making for spine care. Future research should address the influence of BMI on surgeon decision-making, surgical techniques/surgical team volumes best suited to patients with elevated BMI and the correlation between BMI and presentation for post-operative emergency care. Creation of a risk-benefit-BMI algorithm for spine surgery would aid in the informed consent process.