Strategy for obtaining solid fusion at L5–S1 in adult spinal deformity: risk factor analysis for nonunion at L5–S1

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>Maintaining lumbosacral (LS) arthrodesis and global sagittal balance after long fusion to the sacrum remains an important issue in the surgical treatment for adult spinal deformity (ASD). The importance and usefulness of LS fixation have been documented, but the optimal surgical long fusion to the sacrum remains a matter for debate. Therefore, the authors performed a retrospective study to evaluate fusion on CT scans and the risk factors for LS pseudarthrosis (nonunion) after long fusion to the sacrum in ASD.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>The authors performed a retrospective study of 59 patients with lumbar degenerative kyphosis (mean age 69.6 years) who underwent surgical correction, including an interbody fusion of the L5–S1, with a minimum 2-year follow-up. Achievement of LS fusion was evaluated by analyzing 3D-CT scans at 3 months, 6 months, 9 months, 1 year, and 2 years after surgery. Patients were classified into a union group (n = 36) and nonunion group (n = 23). Risk factors for nonunion were analyzed, including patient and surgical factors.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>The overall fusion rate was 61% (36/59). Regarding radiological factors, optimal sagittal balance at the final follow-up significantly differed between two groups. There were no significant differences in terms of patient factors, and no significant differences with respect to the use of pedicle subtraction osteotomy, the number of fused segments, the proportion of anterior versus posterior interbody fusion, S2 alar iliac fixation versus conventional iliac fixation, or loosening of sacral or iliac screws. However, the proportion of metal cages to polyetheretherketone cages and the proportion of sacropelvic fixation were significantly higher in the union group (p = 0.022 and p &lt; 0.05, respectively).</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>LS junction fusion is crucial for global sagittal balance, and the use of iliac screws in addition to LS interbody fusion using a metal cage improves the outcomes of long fusion surgery for ASD patients.</jats:p></jats:sec>

Metal failure and nonunion at L5-S1 after long instrumented fusion distal to pelvis for adult spinal deformity: Anterior versus transforaminal interbody fusion

“…Nemoto et al 35 studied CT data from 50 patients who underwent one-level TLIF, using local bone graft materials, and reported that the titanium cage group showed a higher fusion rate than the PEEK cage group. According to a study by Lee et al, 25 based on CT scans, fusion rates after L5-S1 interbody fusion were higher in patients in whom a titanium-made ALIF cage had been used than in those patients with PEEK-made ALIF cages. Third, the disc height after interbody fusion surgery was greater and significantly more increased in the ALIF group than in the TLIF group; the DH at 2 years was 17.9 mm for the ALIF group and 13.2 mm for the TLIF group (Table 3).…”

“…We excluded these from the analysis because these failures are known not to be related to lumbosacral pseudoarthrosis, but the mobility of the sacroiliac joint, and are considered to be minor failures that do not deteriorate the clinical outcomes. 24,25 Because the follow-up duration was significantly longer in the TLIF group, we had to consider the time to calculate the metal failure rate. Thus, in this study, we performed Kaplan-Meier survivorship analysis with the log-rank test to calculate and compare the metal failure-free probability between the ALIF and TLIF groups.…”

Analysis of Rod Fracture at the Lumbosacral Junction Following Surgery for Adult Spinal Deformity

“…We considered this a limitation of this retrospective study. Several studies have reported that interbody fusion was an important factor in RFs and pseudarthrosis [ 5 , 11 , 19 ], and that the cage material made a difference [ 11 ]. We agree with these opinions and mainly performed interbody fusion at the lumbosacral junction following ASD surgery.…”

Biomechanical evaluation of multiple pelvic screws and multirod construct for the augmentation of lumbosacral junction in long spinal fusion surgery

“…Anterior column support using fusion cages could enhance the fusion rate and prevent implant failure at LSJ ( Jung et al, 2019 ; Lee et al, 2020 ). However, osteoporosis is a risk factor for cage subsidence, with a high prevalence of 32.8% in ASD patients undergoing long spinal fusion ( Gupta et al, 2021 ; Yang et al, 2021 ).…”