Validation and Analysis of a Multi-site MIS Prospective Registry Through Sub-analysis of an MIS TLIF Subgroup

STUDY DESIGN: Retrospective analysis of multi-site, prospectively collected database. OBJECTIVE: To assess the validity and utility of a prospective spine registry by sub-analysis of patients treated with MIS TLIF. BACKGROUND: The MIS registry is a large-scale, multi-center series of prospectively collected clinical information on outcomes, complications, and adverse events for minimally invasive spine procedures for the treatment of degenerative lumbar conditions. METHODS: Analysis was performed on the MIS Prospective Registry database. A subgroup of patients treated by MIS TLIF technique was identified. Statistical analyses were performed on pre and post-operative data collected using validated health related quality of life outcome tools. Missing 1-year patient follow-up data was obtained through progressive correspondence modalities. RESULTS: Data analysis was performed on 98 MIS TLIF patients (56 female, 42 male) with a median age of 64.5 years (range 25-91 years) which were extracted from a total registry population of 478 patients. The one year follow-up rate was 87%. A total of 64 single-level, 23 two-level, 3 three-level, and 3 combined TLIFs staged with an MIS lateral procedure were included. The primary surgical indications were spondylolisthesis (27%), central stenosis (25%), foraminal stenosis (14%), post-laminectomy syndrome (14%) and degenerative scoliosis (6%). The peri-operative blood transfusion rate was 3%. Complications included intraoperative dural tear (n = 3), deep wound infection (n = 2), superficial dehiscence/cellulitis (n = 2). There was a 4% re-operation rate at the 1 year post-operative time point. Half of patients were discharged within 2 days (range 1-11 days, mean 2.97 days, median 2 days). All patients that were discharged on the first post-operative day (n = 14) underwent a single-level MIS TLIF procedure and had significantly lower pre-op disability index score than those discharged on POD 3-5 (43.7 ± 15.5 vs. 56.0 ± 18.3, p = 0.04). Average ODI scores in the subgroup of patients that had reached the one year postoperative time point were 46.5 pre-op (n = 46), and 26.2 at 1 year post-op (n = 40, p = 0.0001). There was significant improvement in VAS scores: pre-operative (back = 6.7, leg = 5.4, n = 46), and 1 year post-operative (back = 3.2, leg = 1.7, n = 40, p = 0.0001). Patients with pre-operative ODI scores greater than 50 demonstrated significant improvement starting at the 6 week post-operative time point (24 point improvement, n = 46, p < 0.001). A pre-operative ODI between 35-50 showed significant improvement starting at 3 months (15.5 point improvement, n = 29, p = 0.05). Patients with a pre-operative ODI score less than 35 had an initial period of increased disability with a trend towards significant improvement by 3 months post-op (n = 20). CONCLUSIONS: Initial findings of the MIS Prospective Registry show patients can be enrolled in a relatively short time period and patient based questionnaires can successfully be obtained through a combination of clinic follow-up appointments and remote correspondence. Outcomes of the MIS Registry MIS TLIF subgroup were consistent with previously published MIS TLIF studies. Sub-analysis of data collected through level-specific patient diagnosis and treatment modalities permits outcome analysis of a wide breadth of spinal conditions and interventions.