Advancing the Field of Minimally Invasive Spine Surgery through Research

overhead surgical lighting, lampsI was recently honored with the 2015 Best Paper Award at the Society for Minimally Invasive Spine Surgery (SMISS) Global Forum. The forum is a gathering of spine surgeons from around the world who come together to further our knowledge of the best ways to treat spinal deformity with a minimally invasive approach. Ours is a field that is relatively young compared to other well-studied fields of medicine (heart surgery, for example). We are only recently (in the last few years) able to produce long-term data results on the outcomes for people who have undergone minimally invasive spine surgery. The data is invaluable and incredibly promising.

The paper I presented and the one for which the Best Paper award was bestowed was titled: “Analysis of the 10 best and 10 worst functional outcomes of Circumferential Minimally Invasive Surgical (CMIS) correction of Adult Spinal Deformity (ASD).” It’s a mouthful, I know. But as a surgeon who also has a responsibility to educate the public about the latest advances in spine surgery, I feel it important to share these results with you.

The brief abstract from the study itself is loaded with medical and scientific acronyms. They are important, but virtually meaningless to a layperson if they’re not unpacked with at least some explanation of what they actually mean. Below, I have included a description of two of the measurements used in assessing the outcomes that were referenced in the study. I encourage you to read through them in order to understand the impact of the study results and the promise it holds for spine surgeons and for future patients.

ODI - Oswestry Disability Index:  The ODI is a widely-used questionnaire by clinicians and researchers to quantify disability for low back pain in the condition-specific management of patients with spinal disorders. It is considered the “gold standard” for measuring the degree of disability and estimating quality of life in a person with low back pain. The ODI questionnaire is completed by the patient and contains topics concerning the intensity of pain, lifting, ability to care for oneself, ability to walk, ability to sit, sexual function, ability to stand, social life, sleep quality and ability to travel. Each of these topics is followed by six statements and the patient checks the box corresponding to the statement that most closely resembles the situation they think they are in. The index is then scored on a scale from 0 to 100, with zero being no disability and 100 being the maximum possible disability.

VAS – Visual Analog Scale: This is a psychometric response scale used in questionnaires of patients experiencing pain, both before and after surgery. It is an instrument of measurement for subjective characteristics or attitudes that cannot otherwise be directly measured.  That is a very scientific definition for something you have probably seen before – a pain scale. Pain is a difficult thing for clinicians to measure because it’s personal and presents itself uniquely for each patient. This visual scale helps “quantify” the severity of pain with 0 representing no pain at all, 5 representing moderate pain and 10 representing unbearable pain or the worst pain you’ve ever felt.

If you’re still with me after that medical school session, the results of this award-winning study are much simpler to understand.

As I mentioned previously, predictors of outcome following CMIS spinal surgery for ASD have not historically been well-studied. What I and my study co-authors endeavored to do was to identify both clinical and radiological predictors of the most favorable and unfavorable ASD surgical outcomes. Our objective in doing this was simple, if we can identify who will likely do well with surgery and who won’t, we are better able to help people suffering from spinal deformity with their treatment decisions – based on research.

This was a single-center study and only patients with a documented 2-year ODI were included in it. 44 patients were identified. Here is what we discovered:

  • The 10 best patients had 0 cases of pseudoarthrosis (failure of the bone to fuse or mend together) and the 10 worst patients had 4 cases.
  • The 10 best patients as compared to the 10 worst had significantly lower ODI before surgery, lower VAS after surgery, less surgical complications and lower incidence of postoperative pseudoarthrosis.
  • 90% of the patients in the “worst outcome” group were operated on before 2011.
  • Patient factors (age, sex, depression, diabetes, BMI and smoking) and baseline deformity (COBB angle, AT, Coronal Balance, SVA, PI-LL mismatch) were not statistically significant in our series.

The study’s conclusion suggests that a patient’s ODI and VAS before surgery is a significant factor in their final outcome with CMIS techniques. This means that very careful selection of patients for surgery is crucial for spine surgeons. Our study also demonstrates that the least favorable outcomes are directly associated with postoperative complications, namely pseudoarthrosis. One revealing finding was that 90% of the poor cases occurred before 2011 which probably suggests that as our experience increased, our outcomes were better. This is also a testament to the improvements in CMIS techniques over the past decade. The bottom line here is that the future is very bright for our patients and our field.