Laterally placed expandable interbody spacers improve radiographic and clinical outcomes: A 1-year follow-up study

Introduction: A common surgical option for the treatment of degenerative disc disease is minimally invasive lateral lumbar interbody fusion (MIS LLIF). This approach has been shown to minimize blood loss and soft tissue dissection when compared to open posterior lumbar interbody fusion. Expandable lateral interbody spacers are designed to maximize segmental lordosis, which is essential for sagittal balance correction. This study describes the clinical and radiographic outcomes of patients treated with expandable interbody spacers for MIS LLIF. Methods: A retrospective, single surgeon, clinical and radiographic study was performed on 37 consecutive patients who underwent MIS LLIF at 1–2 contiguous level(s) using expandable spacers. Radiographic and clinical functional outcomes were collected and compared at preoperative and postoperative time points up to 12 months. Parametric and nonparametric tests were used when appropriate with p value < 0.05 being significant (SPSS® v20.0.0 software for Windows (IBM Corp., Armonk, New York, USA) software was used to analyze data statistically). Results: Thirty-seven consecutive patients were evaluated with an average age of 60 ± 12.0 years, and 37.8% were female. Mean Visual Analog Scale (VAS) for leg and back pain decreased significantly by a mean of 6.7 ± 1.3 points from preoperative to 12 months (p < 0.001). Oswestry Disability Index (ODI) scores significantly decreased by a mean of 63.2 ± 13.2 points (p < 0.001). Lumbar lordosis improved by a mean of 2.3 ± 8.8° at 12 months postoperative (P = 0.112). There were 46 spinal levels, with 39.1% (18/46) at L4–L5 and 37.0% (17/46) at L3–L4. Anterior, middle, and posterior disc height significantly increased from preoperative to 12 months with a mean of 4.9 ± 3.5 mm, 4.2 ± 3.8 mm, and 2.2 ± 2.4 mm, respectively (p < 0.001). Mean neuroforaminal height increased by 3.4 ± 3.7 mm at 12 months (p < 0.001). Segmental lordosis improved by 3.7 ± 2.9° from preoperative to 12 months. There was 100% fusion at all levels, with no cases of radiolucency and 1 case of subsidence at 12 months. There were no reported implant-related complications, with 0% pseudoarthrosis. Estimated blood loss at both 1-level (1L) and 2-level (2L) was <50 cc. Mean operative time was 57.6 ± 15.3 min for 1 L fusions and 93.6 ± 14.0 min for 2 L fusions. Mean fluoroscopic times were 23.0 ± 10.9 sec for 1 L fusions and 32.4 ± 23.4 sec for 2 L fusions. Length of hospital stay was 3.8 ± 1.6 days for 1 L fusions and 4.2 ± 2.2 days for 2 L fusions. Conclusion: Significant increases in disc height, neuroforaminal height, segmental lordosis, and indirect decompression were achieved and maintained up to 1-year follow-up from baseline. Functional clinical outcomes were significantly improved for patients who underwent MIS LLIF using expandable interbody spacers based on decreased VAS pain scores and ODI scores at 1-year follow-up. The use of expandable spacers was shown to be safe, durable and effective for the studied patients.