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Minimally invasive surgery for moderate sagittal imbalance improved pain scores
Patients with severe sagittal imbalance had worse outcomes than patients with moderate imbalance.
NEW ORLEANS — Circumferential minimally invasive surgery for patients with minimal to moderate sagittal imbalance was associated with statistically significant improvement in Oswestry Disability Index and VAS scores, as well as health-related quality of life at 2 years’ follow-up. But, patients with severe sagittal imbalance showed little radiographic improvement based on results of a multicenter database study.
Circumferential minimally invasive surgery can successfully stabilize patients who have good sagittal alignment or moderate imbalance, but it often does not provide similar improvements for patients who have severe sagittal imbalance, according to Paul Park, MD, of Ann Arbor, Mich.
“The [minimally invasive surgery] MIS techniques successfully stabilize patients with an SRS-Schwab global alignment modifier of zero and +. These are in the normal sagittal alignment and modest sagittal imbalanced patients. They had significantly improved HRQOL [health-related quality of life] at 2 years. For patients who are highly imbalanced — those greater than 9.5 cm — showed minimal sagittal radiographic improvement. They showed minimal or less clinical improvement,” Park said at the Congress of Neurological Surgeons Annual Meeting.
Three classifications
The retrospective, multicenter study he presented utilized a database of 426 patients who underwent surgery from 2009 to 2012. A total of 86 patients met the inclusion criteria for the study with 2-year follow-up data.
There were no differences in the patients’ baseline HRQOL scores.
Based on their SRS-Schwab global alignment modifier, patients were placed into the Scoli group (non-pathologic sagittal alignment; 51 patients), + group (sagittal balance of 4 cm to 9.5 cm at baseline; 21 patients) or ++ group (sagittal balance greater than 9.5 cm; 14 patients). They were analyzed for demographic, radiographic and HRQOL measures.
Imbalance affected outcomes
Investigators followed these groups for a mean 33.2 months.
“The Scoli group was younger, which makes some sense in terms of having relatively better sagittal balance,” Park said.
Postoperatively, the Scoli group experienced a mean 18.6 point improvement in Oswestry Disability Index (ODI) scores and the + group experienced a mean 21.9 point improvement in ODI scores. Although the ++ group showed ODI scores that improved mean 8.0 points postoperatively, the improvement was not statistically significant, according to Park.
The ++ group did not show statistically significant improvement in VAS back or leg pain, pelvic incidence-lumbar lordosis mismatch, sagittal vertical axis and lumbar lordosis.
MIS and radiographic parameters
“When you look at the results in a slightly different way, of the 51 patients in the Scoli group, a small number (17.6%) degenerated to the + and ++ group at last follow-up. In the + group, the majority stayed put — 61.9% — and a few (14.3%) degraded to the ++ group. Similarly, most [patients] stayed in the ++ group — 64.3% — with the remaining improving to + (21.4%) and Scoli (14.3%),” Park said.
According to Park, the outcomes of patients in this study relate to the theory that sagittal and spinal pelvic parameters correlate directly to surgical outcomes. Most patients with sagittal vertical axis < 9.5 cm showed no significant radiographic improvement and minimal or less clinical improvement after circumferential MIS.
He said the outcomes also suggest surgeons should consider an open procedure over MIS for patients with severe sagittal imbalances. – by Robert Linnehan
- Reference:
- Mundis G, et al. Paper #172. Presented at: Congress of Neurological Surgeons Annual Meeting; Sept. 26-30, 2015; New Orleans.
- For more information:
- Paul Park, MD, can be reached at Department of Neurosurgery, University of Michigan Health System, 1500 E. Medical Center Dr., Ann Arbor, MI 48109; email: ppark@med.umich.edu.
Disclosure: Park reports he has consulting agreements with Zimmer Biomet, Globus and Medtronic, and receives royalties from Globus.
Perspective
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This is an interesting study examining the efficacy of minimally invasive surgery (MIS) techniques in treating the sagittal plane in adult spinal deformity.
Patients were categorized into SRS-Schwab type deformities and evaluated based on their clinical and radiographic outcomes at 2-year follow-up.
The findings of this study suggest MIS techniques can be effective in treating mild deformities, however, for those which are more severe, MIS techniques did not provide clinical or radiographic improvement for these patients.
This study is an invaluable addition to the literature as our techniques in treating patients evolve and indications for utilizing different procedures types change accordingly. Mundis and colleagues give us a glimpse into patients who would benefit most from newer MIS techniques vs. those who may do better with traditional open techniques.
Often, novel techniques in spine surgery receive criticism early on because of the expansile approach they have towards applying these techniques to patients. It may be that certain techniques are best for different patient subtypes instead of an umbrella approach to treatment. Although this adds another level of specialization into the field of spine surgery, incorporating research such as this into practice can ultimately lead to improved patient outcomes.