Background/objectives:

Minimally invasive lateral lumbar interbody fusion (MIS LLIF) has been employed to treat degenerative disc disease, with reduced complication profiles in comparison to other open anterior and posterior techniques. The technique permits the use of larger, coronal-spanning interbody spacers to restore height and alignment. However, large static spacers have historically been associated with iatrogenic complications during trialing and insertion. Developments in expandable technology have the potential for incrementally larger increases in both height and lordosis in a controlled expansion in situ, minimizing endplate violation. However, further clinical and radiographic data are needed to investigate the effect of expansion technology.

Methods:

A retrospective, single-surgeon chart review was performed on 103 consecutive patients, all of whom underwent MIS LLIF surgery at 1-2 contiguous level(s) with expandable spacers [66/103 patients were implanted with lordotically actuated (adjustable lordosis) spacers, and 37/103 with non-adjustable lordosis spacers]. Clinical and radiographic functional outcomes were collected and compared at both preoperative and postoperative time points up to 12-month follow-up. Parametric and nonparametric tests were utilized when they were appropriate, with a P value < 0.05 being significant.

Results:

One-hundred twenty-five levels were instrumented on 103 consecutive cases. Average age was 58.2 ± 12.1 years; 42.1% (45/107) were female; 78.6% (81/103) were 1-level cases; 21.4% (22/103) were 2-level cases; 44.8% (56/125) were performed at L4-L5 and 34.4% (43/125) at L3-4. Average estimated blood loss was 24.6 ± 12.3cc. Mean operative time was 61.0 ± 19.1 min, and mean fluoroscopic time was 28.2 ± 14.6 s. Visual Analog Scale (VAS) back and leg pain scores decreased significantly by an average of 6.5 ± 1.3 points at 12 months (P < 0.001). Oswestry Disability Index (ODI) scores significantly decreased at final follow-up by a mean of 62.0 ± 12.4 points (P < 0.001). Lumbar lordosis significantly improved by a mean of 3.1 ± 8.8°, while segmental lordosis significantly improved by 3.9 ± 3.1° at 12 months (P < 0.001). Anterior, middle, and posterior disc heights all experienced significant increases at 12 months by averages of 5.1 ± 3.1, 4.5 ± 2.9, and 2.4 ± 2.2 mm, respectively (P < 0.001). Neuroforaminal height significantly increased at 12 months by a mean of 3.7 ± 3.7 mm (P < 0.001). There was 99% fusion at all levels, with no findings of radiolucency and 1% pseudarthrosis observed. Only 1 (1/125, 0.8%) case of subsidence and 7 (7/125, 5.6%) cases of suspected, asymptomatic radiographic adjacent segment degeneration were reported, with no secondary revision surgeries through 12-month follow-up.

Conclusion:

Significant improvement of disc height, neuroforaminal height, segmental lordosis, and indirect decompression was achieved and maintained up to 1-year follow-up from baseline. Clinical outcomes were significantly improved based on appreciable decreases in VAS pain and ODI scores at final follow-up. Minimal complications were reported, with significant radiographic and patient reported outcomes observed. The use of expandable spacers, with and without adjustable lordosis, was shown to improve outcomes for the studied patient population.