Is the use of minimally invasive fusion technologies associated with improved outcomes after elective interbody lumbar fusion? Analysis of a nationwide prospective patient-reported outcomes registry.

BACKGROUND CONTEXT: Over the last decade, clinical investigators and biomedical industry groups have used significant resources to develop advanced technologies that enable less invasive spine fusions. These minimally invasive surgery (MIS) technologies often require increased expenditures by hospitals and payers. Although several small single center studies have suggested MIS technologies decrease surgical morbidity and reduce hospital stay, evidence documenting benefit from a patient perspective remains limited. Furthermore, MIS outcomes have yet to be evaluated from the perspective of multiple practice types representing the broad spectrum of US spine surgery.

PURPOSE: This study aimed to examine a population of patients who underwent one- or two-level interbody lumbar fusion diagnosed with lumbar stenosis or Grade 1 spondylolisthesis in an observational, prospective national registry for the purposes of determining how MIS and traditional open technologies affect postsurgical and patient-reported outcomes (PROs).

STUDY DESIGN/SETTING: This study used observational analysis of prospectively collected data.

PATIENT SAMPLE: The sample consisted of cases from the National Neurosurgery Quality and Outcomes Database (N2 QOD).

OUTCOME MEASURES: Numeric rating scale for back and leg pain, Oswestry Disability Index, EuroQol-5D, return to work, and perioperative morbidity were the outcome measures.

METHODS: The N2 QOD is a prospective PROs registry enrolling patients undergoing elective spine surgery from 60 hospitals in 27 US states via representative sampling. We analyzed the N2 QOD aggregate dataset (2010-2014) to identify one- and two-level lumbar interbody fusion procedures performed for lumbar stenosis or Grade 1 spondylolisthesis with 12 months' follow-up where surgical instrumentation and implant types were clearly identified. Perioperative and 1-year outcomes were compared between cases performed with MIS enabling technologies versus traditional open technologies before and after propensity matching.

RESULTS: There were 467 (24%) patients who underwent elective interbody lumbar fusion using MIS enabling technologies whereas 1,480 (76%) underwent the procedure using traditional open technologies. The MIS patients were slightly healthier (American Society of Anesthesiologists grade), had private insurance more frequently, and underwent two-level fusion less frequently. Unmatched, the MIS cohort was associated with reduced blood loss, a 0.7-day reduction in mean length of hospital stay, and 5% reduced need for post-discharge inpatient rehabilitation, but equivalent 90-day safety measures. After propensity matching, the MIS cohort remained associated with reduced blood loss and a shorter length of stay for one-level fusion (p<.05) but had equivalent length of stay for two-level fusion. Outcomes in all other 90-day safety measures were similar. In both unadjusted and propensity-matched comparison, MIS versus open technologies were associated with equivalent return to work, patient-reported pain, physical disability, and quality of life at 3 and 12 months' follow-up.

CONCLUSIONS: In a representative sampling registry of elective interbody lumbar spine fusion procedures spanning 27 US states, nearly a quarter of procedures performed from 2010 to 2014 used minimally invasive enabling technologies. Regardless of approach, interbody lumbar fusion was associated with significant and sustained improvements in all measured health domains. When used in everyday care by a wide spectrum of spine surgeons in non-research settings, the use of MIS technologies was associated with reduced intraoperative blood loss but only a half-day reduction in mean length of hospital stay for one-level fusions. Minimally invasive surgery was not associated with any improved perioperative safety measures or 12-month outcomes. Although MIS enabling technologies may increase some in-hospital care efficiencies, MIS clinical outcomes are similar to open surgery for patients undergoing one- and two-level interbody lumbar fusions.