Efficacy and Clinical Outcomes of Minimally Invasive Direct Thoracic Interbody Fusion: A Retrospective Analysis

Introduction: A unique surgical approach - the minimally invasive direct interbody fusion (MIS-DTIF) - was previously introduced in our proof-of-concept study, which included four patients who underwent thoracic interbody fusion below the scapula at the T6/7 vertebral level. However, due to the novelty of this method, a report of associated operative parameters such as pain, function, and clinical outcomes from an expanded patient cohort was needed to assess the validity of our results. Materials and Methods: Following IRB approval, data were analyzed retrospectively from electronic health records between 2014 and 2021. Inclusion criteria were patients ≥18 years old who underwent minimally invasive thoracic interbody fusion using the MIS-DTIF technique for at least one vertebral level. The primary outcomes included demographic/radiographic features (e.g., age). Secondary outcomes included perioperative clinical features (e.g., preoperative and ≥1-year final follow-up (FFU)). Tertiary outcomes included perioperative complications. Both preoperative and FFU patient-reported pain and functional outcomes (ODI scores) were analyzed using t-tests to establish significance. Results: A total of 13 patients who underwent MIS-DTIF surgery were observed, with eight male patients and five female patients. The average age was 49.2 years, with an average BMI of 30.5 kg/m(2). Of the surgeries included, the majority (69.23%) were 1-level thoracic vertebrae fusions - with 2-level fusions and ≥ 3-level fusions accounting for 15.38% and 15.38% of cases, respectively. The mean operative time was 58.9 ± 19.9 minutes, with an average fluoroscopy time of 285.7 ± 126.8 seconds and an average actual blood loss volume of 109.0 ± 79.0 mL. The average hospital length of stay was 1.1 (±1.7) days, and no clinically significant perioperative complications were observed in this patient cohort. The average follow-up period was 12.1 ± 9.6 months, with preoperative and FFU back pain visual analog scale (VAS) scores showing highly significant improvement (p<0.001). In addition to pain reduction, quality of life improvements was noted, with significant differences in some of the ODI domains between preoperative and FFU scores (p<0.05), as well as the overall total score between preoperative and FFU ODI assessment (p<0.001) - both of which reflect increased patient function and decreased disability. Conclusion: This study provides further evidence for the safety and efficacy of the MIS-DTIF approach for surgical management of symptomatically refractory patients with thoracic disc herniation or stenosis owing to degenerative disc disease or compression fractures. Additionally, the data gathered suggests that this minimally invasive procedure offers many clinical benefits, including less tissue damage, decreased intraoperative blood loss, shortened surgery time, and shortened hospital length of stay. Finally, in addition to significant pain intensity improvement, this study showed that treated patients highly benefited from ‘sleeping’ and ‘return-to-work’ domains and other ODI functional domains in activities of daily living (ADLs). More clinical studies are recommended in larger patient cohorts to ascertain the findings reported in this study.