Does approach matter? a comparative radiographic analysis of spinopelvic parameters in single level lumbar fusion.

Publication date: Available online 6 April 2018
Source:The Spine Journal
Author(s): Seth Ahlquist, Howard Y. Park, Jonathan Gatto, Ayra N. Shamie, Don Y. Park
Background ContextLumbar fusion is a popular and effective surgical option to provide stability and restore anatomy. Particular attention has recently been focused on sagittal alignment and radiographic spinopelvic parameters that apply to lumbar fusion as well as spinal deformity cases. Current literature has demonstrated the effectiveness of various techniques of lumbar fusion, however comparative data of these techniques is limited.PurposeTo directly compare the impact of various lumbar fusion techniques (ALIF, LLIF, TLIF, PLF) based on radiographic parameters.Study Design/SettingA single-center retrospective study examining pre-operative and post-operative radiographs.Patient SampleA consecutive list of lumbar fusion surgeries performed by multiple spine surgeons at a single institution from 2013-2016 were identified.Outcome MeasuresRadiographic measurements utilized included segmental lordosis (SL), lumbar lordosis (LL), pelvic incidence (PI), pelvic incidence-lumbar lordosis mismatch (PI-LL), anterior and posterior disk height (DH-A, DH-P respectively), and foraminal height (FH).MethodsRadiographic measurements were performed on pre-operative and post-operative lateral lumbar radiographs on all single-level lumbar fusion cases. Demographic data was collected including age, gender, approach, diagnosis, surgical level, and implant lordosis. Paired sample t-test, one-way ANOVA, McNemar Test, and independent sample t-test were used to establish significant differences in the outcome measures. Multiple linear regression was performed to determine a predictive model for lordosis from implant lordosis, fusion technique, and surgical level.ResultsThere were 164 patients (78 males, 86 females) with a mean age of 60.1 years and average radiographic follow up time of 9.3 months. These included 34 ALIF, 23 LLIF, 63 TLIF, and 44 PLF surgeries. ALIF and LLIF significantly improved SL (7.9° & 4.4°), LL (5.5° & 7.7°), DH-A (8.8 mm & 5.8 mm), DH-P (3.4 mm & 2.3 mm), and FH (2.8 mm & 2.5 mm), respectively (p ≤ .003). TLIF significantly improved these parameters, albeit to a lesser extent: SL (1.7°), LL (2.7°), DH-A (1.1 mm), DH-P (0.8 mm), and FH (1.1 mm), p ≤ .02. PLF did not significantly alter any of these parameters while significantly reducing FH (-1.3 mm, p = .01). One-way ANOVA showed no significant differences between ALIF and LLIF other than ALIF with greater ΔDH-A (3.0 mm, p = .02). Both ALIF and LLIF significantly outperformed PLF in pre-operative to post-operative change in all parameters p ≤ .001. Additionally, ALIF significantly outperformed TLIF in the change in SL (6.2°, p < .001) and LLIF significantly outperformed TLIF in the change in LL (5.0°, p = .02). Both outperformed TLIF in ΔDH-A (7.7 mm & 4.7 mm) and ΔDH-P (2.6 mm & 1.5 mm), respectively (p ≤ .02). ALIF was the only fusion technique that significantly improved the proportion of patients with a PI-LL < 10° (0.41 to 0.66, p = .02). Lordotic cages had superior improvement of all parameters as compared to non-lordotic cages (p <.001). Implant lordosis (m = 1.1), fusion technique (m = 6.8), and surgical level (m = 6.9) significantly predicted post-operative SL (p < .001, R2 = .56).ConclusionsThis study demonstrated that these four lumbar fusion techniques yield divergent radiographic results. ALIF and LLIF produced greater improvements in radiographic measurements post-operatively as compared to TLIF and PLF. ALIF was the most successful in improving PI-LL mismatch, an important parameter relating to sagittal alignment. Lordotic implants provided better sagittal correction and surgeons should be cognizant of the impact that these differing implants and techniques produce after surgery. Surgical technique is an important determinant of post-operative alignment and has ramifications upon sagittal alignment in lumbar fusion surgery.



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