Overpowering Posterior Instrumentation and Fusion using a Modified Anterior Lumbar Interbody Fusion Technique, An Experience of 11 Cases

Abstract

IntroductionRestoration of sagittal balance is paramount in any type of spinal reconstructive surgery. Recent work has demonstrated that the failure to maintain lumbar lordosis following fusion not only accelerated adjacent degeneration (Umehara S. et al., Spine. 2000; Rothenfluh D.A. et al., Euro Spine. 2015), but also has a strong correlation to patient's clinical symptomatology, quality of life, and overall function (Glassman S.D. et al., Spine 2005; Schwab F. et al., Spine. 2010). As such, postoperative hypolordosis in the presence of posterior instrumentation and fusion has become a growing problem and presents the operative surgeon with a difficult challenge. In this study we describe our early clinical experience with using a modified anterior lumbar interbody fusion (ALIF) technique for the purposes of increasing lumbar lordosis and improving sagittal imbalance in revision adult spinal deformity patients. Material and MethodsWe present a retrospective case series of 11 patients that developed pain and disability following previous instrumented posterior lateral spinal fusion. All patients were diagnosed with either a posterior pseudoarthrosis and/or a lumbar segment fused with non-anatomic segmental lordosis. All patients underwent ALIF with either anterior wedge allograft or hyperlordotic cages and posterior instrumentation and fusion. Distraction of the disc space and obtainment of the desired lordosis was achieved by using the jackknife capability of the OR table (the patients lumbosacral junction was positioned at the level of the hinge of the table and during the discectomy the table was “jackknifed” into further lordosis). This provided a gradual, and controlled generation of a more anatomic lordosis. Digital standard upright lateral radiographs were used to measure spinopelvic parameters on all patients both pre-, and post-operatively. Two independent observers reviewed each radiograph. ResultsFrom 2014 to 2015, 11 patients underwent revision surgery utilizing this modified ALIF approach with hyperlordotic graft insertion and revision posterior fusion for the treatment of symptomatic sagittal imbalance. Mean patient age was 50.1 years (range 30 – 62). All patients had 30-degree hyperlordotic cages placed while three had an additional standard 20-degree cage placed at an additional lumbar level (average 1.3 per patient). Although preliminary, early postoperative radiographic assessment has shown average increase in L5/S1 segmental and global lumbar lordosis exceeding 20 and 7 degrees, respectively. Additionally, pelvic incidence was found to be increase by an average of 5 degrees. ConclusionThe ability to overpower the posterior instrumentation and to generate added lordosis while fusing the anterior spine is an appealing prospect. In our small series, no loosening of the pedicle screws, or fracture of the pedicles/posterior fusion was observed. We hypothesize that the correction occurs due to flexibility of the titanium bars. Although this is a small series and caution should be exercised before widespread uptake, it does illustrate the potential use of this technique to further address this challenging patient population.