Comparison of Lumbosacral Fusion Grade in Patients after Transforaminal and Anterior Lumbar Interbody Fusion with Minimum 2‐Year Follow‐Up

Abstract

ObjectiveGenerally, anterior lumbar interbody fusion (ALIF) was believed superior to transforaminal lumbar interbody fusion (TLIF) in induction of fusion. However, many studies have reported comparable results in lumbosacral fusion rate between the two approaches. This study aimed to evaluate the realistic lumbosacral arthrodesis rates following ALIF and TLIF in patients with degenerative spondylolisthesis as measured by CT and radiology.MethodsNinety‐six patients who underwent single‐level L5‐S1 fusion through ALIF (n = 48) or TLIF (n = 48) for degenerative spondylolisthesis at the Spine Center, University of California San Francisco, between October 2014 and December 2017 were retrospectively evaluated. Fusion was independently evaluated and categorized as solid fusion, indeterminate fusion, or pseudarthroses by two radiologists using the modified Brantigan–Steffee–Fraser (mBSF) grade. Clinical data on sex, age, body mass index, Meyerding grade, smoking status, follow‐up times, complications, and radiological parameters including disc height, disc angle, segmental lordosis, and overall lumbar lordosis were collected. The fusion results and clinical and radiographic data were statistically compared between the ALIF and TLIF groups by using t‐test or chi‐square test.ResultsThe mean follow‐up period was 37.5 (ranging from 24 to 51) months. Clear, solid radiographic fusions were higher in the ALIF group compared with the TLIF group at the last follow‐up (75% vs 47.9%, p = 0.006). Indeterminate fusion occurred in 20.8% (10/48) of ALIF cases and in 43.8% (21/48) of TLIF cases (p = 0.028). Radiographic pseudarthrosis was not significantly different between the TLIF and ALIF groups (16.7% vs 8.3%; p = 0.677). In subgroup analysis of the patients without bone morphogenetic protein (BMP), the solid radiographic fusion rate was significantly higher in the ALIF group than that in the TLIF group (78.6% vs 45.5%; p = 0.037). There were no differences in sex, age, body mass index, Meyerding grade, smoking status, or follow‐up time between the two groups (p > 0.05). The ALIF group had more improvement in disc height (7.8 mm vs 4.7 mm), disc angle (5.2° vs 1.5°), segmental lordosis (7.0° vs 2.5°), and overall lumbar lordosis (4.7° vs 0.7°) compared with the TLIF group (p < 0.05). Overall complication rates were similar between the TLIF and ALIF groups (10.4% vs 8.33%; p > 0.999).ConclusionsWith a minimum 2‐year radiographic analysis of arthrodesis at lumbosacral level by radiologists, the rate of solid radiographic fusions was higher in the ALIF group compared with the TLIF group, whereas the TLIF group had a higher rate of indeterminate fusion. Radiographic pseudarthrosis did not differ significantly between the TLIF and ALIF groups.

Fusion Assessment of Oblique Lumbar Interbody Fusion Using Demineralized Bone Matrix: A 2-Year Prospective Study

“…The concept of fusion rate after lumbar interbody fusion is subject to interpretation in various studies; different studies have used nonidentical and heterogeneous criteria to assess bone fusion [ 11 , 16 , 21 , 26 - 28 ]. Many studies regarded patients without clear pseudoarthrosis as having successful fusion.…”

“…Many studies regarded patients without clear pseudoarthrosis as having successful fusion. Thus, this could lead to a misunderstanding regarding the real fusion rates and may result in artificially increasing fusion results upon performing different lumbar interbody fusion procedures [ 11 , 29 ]. Therefore, understanding the realistic fusion grade of each method remains crucial for both patients and surgeons when making informed decisions.…”

“…Therefore, understanding the realistic fusion grade of each method remains crucial for both patients and surgeons when making informed decisions. Additionally, pseudoarthrosis is associated with poor outcomes and may require revision surgery [ 11 , 12 , 30 ].…”

“…Radiographic assessment of fusion was performed independently by an experienced neurosurgeon (PK) and a spine fellow (SWL) in a blinded manner based on dynamic radiographs and CT scans at 12, 18, and 24 months postoperatively; the modified Brantigan-Steffee-Fraser (mBSF) scale was used for the assessments. Findings were categorized as grades I (radiographic pseudoarthrosis), II (indeterminate fusion), and III (solid radiographic fusion) [ 4 , 11 , 21 ]. Implant breakage, screw pullout, segmental movement on dynamic radiography > 2°, radiolucency (> 1 mm) around the screws, or clear absence of bridging bone on CT were categorized as pseudoarthrosis (grade I).…”

“…In recent years, TLIF can be performed via a minimally invasive surgical (MIS) approach, which can reduce the denervation of multifidus muscle as well as reduce the incidence of intramuscular degeneration and necrosis [ 4 , 6 - 8 ]. However, patients undergoing MIS-TLIF often suffer from chronic back pain after surgery, owing to the resection of paravertebral muscles and facet joints [ 6 , 9 - 11 ].…”