L1-S1 Lordosis Research Articles

Impact of Segmental Lordosis Restoration During Degenerative Spinal Fusion on Two-Year Adjacent Segment Disease and Revision Rates.

Retrospective cohort study. Assess the impact of inadequate correction of L4-S1 lordosis during transforaminal lumber interbody fusion (TLIF) on adjacent segment disease and revision rates. Restoring alignment is an important consideration in spinal fusions. Failure to correct to level-specific alignment goals could promote the development of adjacent segment disease. As such, it is crucial to investigate the role of sagittal segmental alignment on clinical outcomes following short segment lumbar fusion. Patients who underwent 1- to 3-level transforaminal lumbar interbody fusion (TLIF) and had two-year outcomes data were included in this retrospective cohort study. Segmental lumbar lordosis was assessed in all patients with L3-L4, L4-L5, and L5-S1 constructs. Demographics, radiographic spinopelvic alignment, and complications were compared in a sub-group of patients fused at L4-S1 with adequate (i.e., within 35-45°) and inadequate (i.e., <35°) L4-S1 lordosis. Among the 168 included patients, mean age was 61.7 years, 56.0% were female, and mean follow-up was 32.3 months. Segmental lumbar lordosis did not change significantly after TLIF of L3-L4, L4-L5, or L5-S1 (P>0.05). Two-year postoperatively, 32.7% developed adjacent segment disease and 19.6% underwent revisions. After stratification by adequate (N=15) or inadequate (N=54) restoration of L4-S1 lordosis following initial TLIF surgery, adequately-restored patients had higher preoperative L4-S1 lordosis (Adequately-Restored=39.3° vs Inadequately-Restored=29.5°, P<0.001) and lower two-year postoperative adjacent segment disease (6.7% vs. 33.3%, P=0.032) and revision (5.7% vs. 25.9%, P=0.l33) rates. Adjacent segment disease patients had higher implant-related complications (Adjacent Segment Disease=36.8% vs No Adjacent Segment Disease=8.0%, P=0.008) and subsequent revisions (61.1% vs. 8.7%, P<0.001). Adjacent segment disease and revisions after degenerative lumbar spinal fusion are common. In this cohort, suboptimal restoration of L4-S1 lordosis was associated with higher rates of adjacent segment disease and subsequent revisions, thus highlighting the importance of restoring sagittal alignment in degenerative spine surgery. III.

Expandable versus static transforaminal lumbar interbody fusion (TLIF) cages: comparing radiographic outcomes and complication profiles

Background ContextExpandable transforaminal lumbar interbody fusion (TLIF) cages have become popular in recent years due to anticipated advantages of increased disc height, improved segmental lordosis, and ease of implantation. Such benefits have not been conclusively demonstrated in the literature. PurposeTo determine whether expandable cages increase disc height and segmental lordosis in a durable way following surgery and compare complication profiles between cage types. Study Design/SettingRetrospective cohort study conducted within a large academic health system involving 31 different spine surgeons. Patient SampleAdults undergoing single-level TLIF for an indication other than infection, tumor, trauma, or revision instrumentation from 2021 to 2023. Outcome MeasuresOur primary outcomes were changes in segmental disc height, segmental lordosis, and L4-S1 lordosis at 2 weeks, 6 months, and 1 year following surgery relative to baseline. Our secondary outcomes were frequencies of incidental durotomies, surgical site infections, readmissions, death, subsidence, and unplanned return to the operating room. MethodsRadiographic variables were collected from our institutional imaging registry. Demographics and surgical characteristics were abstracted from chart review. Generalized linear modeling was used for each primary outcome, with cage type (expandable vs. static) as our primary predictor and age, biologic sex, race, CCI, year of surgery, duration of surgery, invasiveness of surgery, surgeon specialty (Orthopedics vs. Neurosurgery), and level of surgery as covariates. ResultsOur cohort consisted of 417 patients with a mean age of 62. Static cages were used in 306 patients and expandable cages in 111. Expandable cages were associated with increased changes in disc height relative to static cages at 2 weeks (1.1 mm [0.2–1.9]; p=.01) and 6 months (1.2 mm [0.2–2.3]; p=.02) following surgery, but differences were no longer significant at 1 year (0.4 mm [−0.9–1.8]; p=.4). Expandable cages were found to subside more commonly than static cages (14.1% vs. 6.6%; p=.04). No significant differences between cage types were identified in lordotic parameters at any timepoint (p=0.25 to p=0.97). ConclusionsExpandable cages were associated with an initial increase in disc height relative to static cages, but this difference diminished with the first year of surgery, likely due to a higher rate of subsidence within the expandable cohort.

Incidence and Risk Factors of Sacral Fracture Following Lumbosacral Fusion for Degenerative Spinal Stenosis with a Minimum Follow-Up of 2 Years: A Case–Control Study

This study aimed to investigate the incidence and risk factors for sacral fractures following lumbosacral fusion. We conducted a retrospective review of patients who underwent lumbosacral fusion for degenerative spinal stenosis with a minimum follow-up of 2years. Patients who developed and those who did not develop a sacral fracture were categorized into the "sacral fracture" and "nonfracture" groups. The demographic and radiological data were compared between the 2 groups. A total of 65 patients were included in this study. Among them, 7 patients were categorized into the sacral fracture and 58 patients into the nonfracture groups, respectively. The incidence of sacral fracture was 10.8%. In the sacral fracture group, age and fusion levels were significantly higher (P<0.05), while bone mineral density (BMD) T-score was significantly lower (P<0.05) than nonfracture group. Pelvic incidence, preoperative pelvic tilt, postoperative sacral slope, and postoperative lumbar lordosis were significantly higher (P<0.05) in the sacral fracture than the nonfracture group. Multivariable logistic regression analysis showed that BMD T-score (odds ratio [OR] 0.25, 95% confidence interval [CI] 0.08-0.79, P=0.019), postoperative sacral slope (OR 1.14, 95% CI 1.00-1.29, P= 0.047), and changes in L4-S1 lordosis (OR 1.11, 95% CI 1.00-1.23, P= 0.049) were significant factors. The overall incidence of sacral fracture was 10.8%. In our study, advanced age, low BMD, long fusion levels, and preoperative compensatory pelvic retroversion and excessive correction of it were risk factors for sacral fractures.

Sequential correction of sagittal vertical alignment and lumbar lordosis in adult flatback deformity

BackgroundFlatback deformity, or lumbar hypolordosis, can cause sagittal imbalance, causing back pain, fatigue, and functional limitation. Surgical correction through osteotomies and interbody fusion techniques can restore sagittal balance and relieve pain. This study investigated sagittal vertical alignment (SVA) and lumbar lordosis correction achieved through sequential procedures on human spine specimens. MethodsHuman T10-sacrum specimens were stratified into 2 groups: degenerative flatback specimens had smaller L1-S1 lordosis compared to the iatrogenic group (26.1°±15.0° vs. 47.8°±19.3°, p<.05). Specimens were mounted in the apparatus in simulated standing posture with a nominal sacral slope of 45 degrees and subjected to a 400N compressive follower preload. Sequential correction of degenerative lumbar flatback deformity involved: anterior lumbar interbody fusion (ALIF) at L5-S1, ALIF at L4-5, lateral lumbar interbody fusion (LLIF) at L2-3 and L3-4, and posterior column osteotomy (PCO) at L2-3 and L3-4. In iatrogenic specimens, flatback deformity was created by performing a posterior in-situ immobilization using pedicle screw instrumentation at L4-L5-S1 followed by distraction across the pedicle screws. We then performed LLIF at L2-3 and L3-4, followed by PCO at L2-3 and L3-4. ResultsStatistically significant incremental corrections were noted in SVAs and lordosis after L5-S1 ALIF, L4-5 ALIF, and PCO in degenerative flatback specimens. For the iatrogenic group, statistically significant worsening was noted in measures of standing alignment after L4-L5-S1 hypolordotic fusion. Subsequent LLIF at L2-3 and L3-4 did not significantly improve sagittal alignment. However, after PCO at L2-3 and L3-4, final alignment parameters were not significantly different than preoperative baseline values prior to hypolordotic fusion. ConclusionsALIF cages in the lower lumbar segments significantly improved sagittal alignment in degenerative flatback specimens. In the upper lumbar segments, LLIF cages alone were ineffective at enhancing lumbar lordosis. LLIF cages in conjunction with PCO improved alignment parameters in degenerative and iatrogenic flatback deformities.

Unilateral versus bilateral pedicle screw fixation with anterior lumbar interbody fusion: a comparison of postoperative outcomes.

To determine of the impact of ALIF with minimally invasive unilateral pedicle screw fixation (UPSF) versus bilateral pedicle screw fixation (BPSF) on perioperative outcomes, radiographic outcomes, and the rates of fusion, subsidence, and adjacent segment stenosis. All adult patients who underwent one-level ALIF with UPSF or BPSF at an academic institution between 2015 and 2022 were retrospectively identified. Postoperative outcomes including length of hospital stay (LOS), wound complications, readmissions, and revisions were determined. The rates of fusion, screw loosening, adjacent segment stenosis, and subsidence were assessed on one-year postoperative CT. Lumbar alignment including lumbar lordosis, L4-S1 lordosis, regional lordosis, pelvic tilt, pelvic incidence, and sacral slope were assessed on standing x-rays at preoperative, immediate postoperative, and final postoperative follow-up. Univariate and multivariate analysis compared outcomes across posterior fixation groups. A total of 60 patients were included (27 UPSF, 33 BPSF). Patients with UPSF were significantly younger (p = 0.011). Operative time was significantly greater in the BPSF group in univariate (p < 0.001) and multivariate analysis (ß=104.1, p < 0.001). Intraoperative blood loss, LOS, lordosis, pelvic parameters, fusion rate, subsidence, screw loosening, adjacent segment stenosis, and revision rate did not differ significantly between fixation groups. Though sacral slope (p = 0.037) was significantly greater in the BPSF group, fixation type was not a significant predictor on regression. ALIF with UPSF relative to BPSF predicted decreased operative time but was not a significant predictor of postoperative outcomes. ALIF with UPSF can be considered to increase operative efficiency without compromising construct stability.

Restoring L4-S1 Lordosis Shape in Severe Sagittal Deformity: Impact of Correction Techniques on Alignment and Complication Profile

Severe sagittal plane deformity with loss of L4-S1 lordosis is disabling and can be improved through various surgical techniques. However, data is limited on the differing ability of anterior lumbar interbody fusion (ALIF), pedicle subtraction osteotomy (PSO), and transforaminal lumbar interbody fusion (TLIF) to achieve alignment goals in severely malaligned patients. To examine surgical techniques aimed at restoring L4-S1 lordosis in severe adult spinal deformity (ASD). Retrospective review of prospectively collected data. A total of 96 patients who underwent ALIF, PSO, and TLIF were included in this study. The following data were observed for all cases: patient demographics, spinopelvic parameters, complications, and PROMs. Severe ASD patients with preoperative PI-LL >20°, L4-S1 lordosis <30°, and full body radiographs and patient-reported outcome measures (PROMs) at baseline and six-week postoperative visit were included. Patients were grouped into ALIF (1-2 level ALIF at L4-S1), PSO (L4/L5 PSO), and TLIF (1-2 level TLIF at L4-S1). Comparative analyses were performed on demographics, radiographic spinopelvic parameters, complications, and PROMs. Among the 96 included patients, 40 underwent ALIF, 27 underwent PSO, and 29 underwent TLIF. At baseline, cohorts had comparable age, sex, race, Edmonton frailty scores and radiographic spinopelvic parameters (p>0.05). However, PSO was performed more often in revision cases (p<0.001). Following surgery, L4-S1 lordosis correction (p=0.001) was comparable among ALIF and PSO patients and caudal lordotic apex migration (p=0.044) was highest among ALIF patients. PSO patients had higher intraoperative estimated blood loss (p<0.001) and motor deficits (p=0.049), and in-hospital ICU admission (p=0.022) and blood products given (p=0.004) but were otherwise comparable in terms of length of stay, blood transfusion given, and postoperative admission to rehab. Likewise, 90-day postoperative complication profiles and six-week PROMs were comparable as well. ALIF can restore L4-S1 sagittal alignment as powerfully as PSO, with fewer intra-operative and in-hospital complications. When feasible, ALIF is a suitable alternative to PSO and likely superior to TLIF for correcting L4-S1 lordosis among patients with severe sagittal malalignment.

Importance of the lumbar paraspinal muscles on the maintenance of global sagittal alignment after lumbar pedicle subtraction osteotomy.

There are limited data about the influence of the lumbar paraspinal muscles on the maintenance of sagittal alignment after pedicle subtraction osteotomy (PSO) and the risk factors for sagittal realignment failure. The authors aimed to investigate the influence of preoperative lumbar paraspinal muscle quality on the postoperative maintenance of sagittal alignment after lumbar PSO. Patients who underwent lumbar PSO with preoperative lumbar MRI and pre- and postoperative whole-spine radiography in the standing position were included. Spinopelvic measurements included pelvic incidence, sacral slope, pelvic tilt, L1-S1 lordosis, T4-12 thoracic kyphosis, spinosacral angle, C7-S1 sagittal vertical axis (SVA), T1 pelvic angle, and mismatch between pelvic incidence and L1-S1 lordosis. Validated custom software was used to calculate the percent fat infiltration (FI) of the psoas major, as well as the erector spinae and multifidus (MF). A multivariable linear mixed model was applied to further examine the association between MF FI and the postoperative progression of SVA over time, accounting for repeated measures over time that were adjusted for age, sex, BMI, and length of follow-up. Seventy-seven patients were recruited. The authors' results demonstrated significant correlations between MF FI and the maintenance of corrected sagittal alignment after PSO. After adjustment for the aforementioned parameters, the model showed that the MF FI was significantly associated with the postoperative progression of positive SVA over time. A 1% increase from the preoperatively assessed total MF FI was correlated with an increase of 0.92 mm in SVA postoperatively (95% CI 0.42-1.41, p < 0.0001). This study included a large patient cohort with midterm follow-up after PSO and emphasized the importance of the lumbar paraspinal muscles in the maintenance of sagittal alignment correction. Surgeons should assess the quality of the MF preoperatively in patients undergoing PSO to identify patients with severe FI, as they may be at higher risk for sagittal decompensation.

Association patterns between lumbar paraspinal muscles and sagittal malalignment in preoperative patients undergoing lumbar three-column osteotomy.

We aim to investigate the associations between lumbar paraspinal muscles and sagittal malalignment in patients undergoing lumbar three-column osteotomy. Patients undergoing three-column osteotomy between 2016 and 2021 with preoperative lumbar magnetic resonance imaging (MRI) and whole spine radiographs in the standing position were included. Muscle measurements were obtained using a validated custom software for segmentation and muscle evaluation to calculate the functional cross-sectional area (fCSA) and percent fat infiltration (FI) of the m. psoas major (PM) as well as the m. erector spinae (ES) and m. multifidus (MM). Spinopelvic measurements included pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), L1-S1 lordosis (LL), T4-12 thoracic kyphosis (TK), spino-sacral angle (SSA), C7-S1 sagittal vertical axis (SVA), T1 pelvic angle (TPA) and PI-LL mismatch (PI-LL). Statistics were performed using multivariable linear regressions adjusted for age, sex, and body mass index (BMI). A total of 77 patients (n = 40 female, median age 64years, median BMI 27.9kg/m2) were analyzed. After adjusting for age, sex and BMI, regression analyses demonstrated that a greater fCSA of the ES was significantly associated with greater SS and SSA. Moreover, our results showed a significant correlation between a greater FI of the ES and a greater kyphosis of TK. This study included a large patient cohort with sagittal alignment undergoing three-column osteotomy and is the first to demonstrate significant associations between the lumbar paraspinal muscle parameters and global sagittal alignment. Our findings emphasize the importance of the lumbar paraspinal muscles in sagittal malalignment.

Impact of obesity on adult spinal deformity (ASD) long-segment spinal fusion radiographic and clinical outcomes

Study designRetrospective chart review of patients receiving long-segment fusion during a five-year period. ObjectiveTo determine whether obese patients receive comparable benefits when receiving long-segment fusion compared to non-obese patients and to identify factors that may predict hardware failure and post-surgical complications among obese patients. MethodsDemographic, spinopelvic radiographic, patient-reported outcome measures (PROMs), and complications data was retrospectively collected from 120 patients who underwent long-segment fusion during a five-year period at one tertiary care medical center. Radiographic measurements were pelvic incidence, pelvic tilt (PT), lumbar lordosis, L4-S1 lordosis, thoracic kyphosis, sagittal vertical axis, PI-LL mismatch, and proximal junction cobb angle at upper instrumented vertebrae + 2 (UIV+2). PROMs were Oswestry disability index, numeric rating scale (NRS) Back Pain, NRS Leg Pain, RAND SF-36 pain, and RAND SF-36 physical functioning. Included patients were adults and had at least 2-years of postoperative follow-up. Descriptive and multivariate statistical analysis was performed with α = 0.05. ResultsPatients with a BMI ≥ 30 (n=63) and patients with a BMI < 30 (n=57) demonstrated comparable improvements (P>0.05) for all spinopelvic radiographic measurements and PROMs. Each cohort demonstrated significant improvements from pre-assessment to post-assessment on nearly all spinopelvic radiographic measurements and PROMs (P<0.05), except PT and L4-S1 lordosis where neither group improved (p=0.95 and 0.58 for PT and P=0.23 and 0.11 for L4-S1 lordosis fornon-obese and obese cohorts respectively) and SF-36 physical functioning where the non-obese cohort not statistically improve (P=0.08). Patients with a BMI ≥ 30 demonstrated an increased incidence of cardiovascular complications (P=0.0293), acute kidney injury (P=0.0241), rod fractures (P=0.0293), and reoperations (P=0.0241) when compared to patients with a BMI < 30. ConclusionThis study adds to a growing body of evidence linking demographic factors with risks of hardware failure. Further, this data challenges the assumption that obese patients may not receive sufficient benefit to be long-segment surgical candidates. However, given their elevated risk for post-operative and delayed hardware complications, obese patients should be appropriately counseling before undergoing surgery.

Combined Anterior–Posterior vs. Posterior-Only Approach in Adult Spinal Deformity Surgery: Which Strategy Is Superior?

Introduction: Whether a combined anterior–posterior (AP) approach offers additional benefits over the posterior-only (P) approach in adult spinal deformity (ASD) surgery remains unknown. In a cohort of patients undergoing ASD surgery, we compared the combined AP vs. the P-only approach in: (1) preoperative/perioperative variables, (2) radiographic measurements, and (3) postoperative outcomes. Methods: A single-institution, retrospective cohort study was performed for patients undergoing ASD surgery from 2009 to 2021. Inclusion criteria were ≥5-level fusion, sagittal/coronal deformity, and 2-year follow-up. The primary exposure was the operative approach: a combined AP approach or P alone. Postoperative outcomes included mechanical complications, reoperation, and minimal clinically important difference (MCID), defined as 30% of patient-reported outcome measures (PROMs). Multivariable linear regression was controlled for age, BMI, and previous fusion. Results: Among 238 patients undergoing ASD surgery, 34 (14.3%) patients underwent the AP approach and 204 (85.7%) underwent the P-only approach. The AP group consisted mostly of anterior lumbar interbody fusion (ALIF) at L5/S1 (73.5%) and/or L4/L5 (38.0%). Preoperatively, the AP group had more previous fusions (64.7% vs. 28.9%, p &lt; 0.001), higher pelvic tilt (PT) (29.6 ± 11.6° vs. 24.6 ± 11.4°, p = 0.037), higher T1 pelvic angle (T1PA) (31.8 ± 12.7° vs. 24.0 ± 13.9°, p = 0.003), less L1-S1 lordosis (−14.7 ± 28.4° vs. −24.3 ± 33.4°, p &lt; 0.039), less L4-S1 lordosis (−25.4 ± 14.7° vs. 31.6 ± 15.5°, p = 0.042), and higher sagittal vertical axis (SVA) (102.6 ± 51.9 vs. 66.4 ± 71.2 mm, p = 0.005). Perioperatively, the AP approach had longer operative time (553.9 ± 177.4 vs. 397.4 ± 129.0 min, p &lt; 0.001), more interbodies placed (100% vs. 17.6%, p &lt; 0.001), and longer length of stay (8.4 ± 10.7 vs. 7.0 ± 9.6 days, p = 0.026). Radiographically, the AP group had more improvement in T1PA (13.4 ± 8.7° vs. 9.5 ± 8.6°, p = 0.005), L1-S1 lordosis (−14.3 ± 25.6° vs. −3.2 ± 20.2°, p &lt; 0.001), L4-S1 lordosis (−4.7 ± 16.4° vs. 3.2 ± 13.7°, p = 0.008), and SVA (65.3 ± 44.8 vs. 44.8 ± 47.7 mm, p = 0.007). These outcomes remained statistically significant in the multivariable analysis controlling for age, BMI, and previous fusion. Postoperatively, no significant differences were found in mechanical complications, reoperations, or MCID of PROMs. Conclusions: Preoperatively, patients undergoing the combined anterior–posterior approach had higher PT, T1PA, and SVA and lower L1-S1 and L4-S1 lordosis than the posterior-only approach. Despite increased operative time and length of stay, the anterior–posterior approach provided greater sagittal correction without any difference in mechanical complications or PROMs.

Transforaminal lumbar interbody fusion with a tantalum cage: lumbar lordosis redistribution and sacral slope restoration with a modified posterior technique

BackgroundTransforaminal lumbar interbody fusion (TLIF), a commonly used procedure in spine surgery, has the advantage of a lower incidence of nerve lesions compared to the posterior lumbar interbody fusion (PLIF) technique. The intersomatic arthrodesis has always been carried out with a single tantalum cage normally used for PLIF. Tantalum is a metal that is particularly used in orthopedic surgery. It has a modulus of elasticity similar to marrow and leads to high primary stability of the implant.Materials and methodsOur study was a retrospective monocentric observational study evaluating clinical and radiological outcomes of tantalum cages in a modified TLIF technique with posterior instrumentation and autologous and/or homologous posterolateral bone grafting. The aim of the study was to evaluate clinical outcomes and the increase in or redistribution of lumbar lordosis. The intersomatic arthrodesis was always carried out with a single tantalum cage normally used for PLIF to reduce the neurological risk. We retrospectively studied 105 patients who were treated with a modified unilateral TLIF approach by two surgeons between 2013 and 2018. We evaluated the Oswestry Disability Index (ODI), Visual Analogue Scale (VAS) for back pain, global lumbar lordosis, lordosis of L4–sacrum, segmental lordosis of functional motion units that underwent arthrodesis, pelvic tilt, pelvic incidence, and the sacral slope in 77 patients. All patients were suffering from grade III or IV Pfirrmann, instability, or foraminal post-laminectomy stenosis and/or grade I–II degenerative spondylolisthesis or low-grade isthmic spondylolisthesis. They had no significant sagittal imbalance, with a sagittal vertical axis (SVA) of < 5 mm. The average follow-up duration was 30 months.ResultsWe achieved excellent clinical results, with only four cases of failure (5.2%). Moreover, we noticed a statistically significant redistribution of lumbar lordosis, with an average percentage increase in L4–S1 lordosis equal to 19.9% (P < 0.001), an average increase in the L4–S1/Lumbar lordosis (LL) ratio from 0.53 to 0.63 (P < 0.001), and a mean percentage increase in sacral slope equal to 7.6% (P < 0.001).Conclusion Thanks to the properties of tantalum, our modified single-portal TLIF technique is a valid surgical solution to obtain a solid arthrodesis and restore the correct lumbar lordosis distribution while reducing neurological complications and the number of failures.Level of evidence: 4Trial registration statement: retrospective observational study, no trial registration.

Risk Factors for Distal Junctional Problems Following Long Instrumented Fusion for Degenerative Lumbar Scoliosis: Are they Related to the Paraspinal Muscles.

Although the incidence of distal junctional problems (DJPs) following long construct-based treatment for degenerative lumbar scoliosis (DLS) is lower, affected patients are more likely to require revision surgery when they occur. So the aim of this study is to identify risk factors associated with DJPs to avoid its occurrence by at least 1-year follow-up. A total of 182 DLS patients undergoing long instrumented fusion surgery (≥4 levels) between February 2011 and March 2022 were retrospectively analyzed. Patients were placed into the DJP group if a DJP occurred at the final follow-up; patients without mechanical complications were matched 1:2 according to age, sex and BMI as the control group. Patient characteristics, surgical variables, radiographic parameters, lumbar muscularity and fatty degeneration were analyzed statistically. The statistical differences in the results between the two groups (p values <0.05) and other variables selected by experts were entered into a multivariate logistic regression model, and the forwards likelihood ratio method was used to analyze the independent risk factors for DJPs. Twenty-four (13.2%) patients suffered a DJP in the postoperative period and the reoperation rate was 8.8%. On univariate analysis, the lowest instrumented vertebra (LIV) CT value (p = 0.042); instrumented levels (p = 0.030); preoperative coronal vertical axis (CVA) (p = 0.046), thoracolumbar kyphosis (TLK) (p = 0.006), L4-S1 lordosis (p = 0.013), sacral slop (SS) (p = 0.030), pelvic tilt (PT) classification (p = 0.004), and sagittal vertical axis (SVA) (p = 0.021); TLK correction (p = 0.049); post-operative CVA (p = 0.029); Overall, There was no significant difference in the paraspinal muscle parameters between the two groups. On multivariate analysis, instrumented levels (OR = 1.595; p = 0.035), preoperative SVA (OR = 1.016; p = 0.022) and preoperative PT (OR = 0.873; p = 0.001) were identified as significant independent risk factors for DJP. Longer instrumented levels, a greater preoperative SVA and a smaller PT were found to be strongly associated with the presence of DJPs in patients treated for DLS. The degeneration of the paraspinal muscles may not be related to the occurrence of DJPs. For DLS patients, the occurrence of DJP can be reduced by selecting reasonable fusion segments and evaluating the patient's sagittal balance and spino-pelvic parameters before operation.

Single position L5-S1 lateral ALIF with simultaneous robotic posterior fixation is safe and improves regional alignment and lordosis distribution index

PurposeMinimally invasive single position lateral ALIF at L5-S1 with simultaneous robot-assisted posterior fixation has technical and anatomic considerations that need further description.MethodsThis is a retrospective case series of single position lateral ALIF at L5-S1 with robotic assisted fixation. End points included radiographic parameters, lordosis distribution index (LDI), complications, pedicle screw accuracy, and inpatient metrics.ResultsThere were 17 patients with mean age of 60.5 years. Eight patients underwent interbody fusion at L5-S1, five patients at L4-S1, two patients at L3-S1, and one patient at L2-S1 in single lateral position. Operative times for 1-level and 2-level cases were 193 min and 278 min, respectively. Mean EBL was 71 cc. Mean improvements in L5-S1 segmental lordosis were 11.7 ± 4.0°, L1-S1 lordosis of 4.8 ± 6.4°, sagittal vertical axis of − 0.1 ± 1.7 cm°, pelvic tilt of − 3.1 ± 5.9°, and pelvic incidence lumbar–lordosis mismatch of − 4.6 ± 6.4°. Six patients corrected into a normal LDI (50–80%) and no patients became imbalanced over a mean follow-up period of 14.4 months. Of 100 screws placed in lateral position with robotic assistance, there were three total breaches (two lateral grade 3, one medial grade 2) for a screw accuracy of 97.0%. There were no neurologic, vascular, bowel, or ureteral injuries, and no implant failure or reoperation.ConclusionSingle position lateral ALIF at L5-S1 with simultaneous robotic placement of pedicle screws by a second surgeon is a safe and effective technique that improves global alignment and lordosis distribution index.

Rod angulation does not reflect sagittal curvature in adult spinal deformity surgery: comparison of lumbar lordosis and rod contouring.

A retrospective study. Relationship between rod and spinal shape in the sagittal plane in adult spinal deformity (ASD) surgery. Corrective surgery for adult spinal deformity (ASD) involves the use of contoured rods to correct and modify the spinal curvatures. Adequate rod bending is crucial for achieving optimal correction. The correlation between rods and spinal shape in long constructs has not been reported previously. We conducted a retrospective analysis of a prospective, multicenter database of patients who underwent surgery for ASD. The inclusion criteria were patients who underwent pelvic fixation and had an upper instrumented vertebra at or above T12. Pre- and post-operative standing radiographs were used to assess lumbar lordosis at the L4S1 and L1S1 levels. The angle between the tangents to the rod at the L1, L4, and S1 pedicles was calculated to determine the L4S1 and L1S1 rod lordosis. The difference between the lumbar lordosis (LL) and the rod lordosis (RL) was calculated as ΔL = LL-RL. The correlation between this difference (ΔL) and various characteristics was analyzed using descriptive and statistical methods. Eighty-three patients were included in the study, resulting in 166 analyzed differences (ΔL) between the rod and spinal lordosis. The values for rod lordosis were found to be both greater and lesser than those of the spine but were mostly lower. The range for total ΔL was -24°-30.9°, with a mean absolute ΔL of 7.8° for L1S1 (standard deviation (SD) = 6.0) and 9.1° for L4S1 (SD = 6.8). In 46% of patients, both rods had a ΔL of over 5°, and over 60% had at least one rod with a ΔL difference of over 5°. Factors found to be related to a higher ΔL included postoperative higher lumbar lordosis, presence of osteotomies, higher corrected degrees, older age, and thinner rods. Multivariate analysis correlated only higher postoperative L1S1 lordosis with higher ΔL. No correlation was found between a higher ΔL and sagittal imbalance. Variations between spinal and rod curvatures were observed despite the linear regression correlation. The shape of the rod does not seem to be predictive of the shape of the spine in the sagittal plane in ASD long-construct surgeries. Several factors, other than rod contouring, are involved in explaining the postoperative shape of the spine. The observed variation calls into question the fundamentals of the ideal rod concept.

Psychopathological profile and sagittal alignment in low-back pain

IntroductionLow-back pain requires comprehensive care using a biopsychosocial model. The psychologic dimension plays an important role, but the link between sagittal alignment and a given psychopathological profile is little studied. The aim of this study was to analyze the psychopathological profiles and sagittal parameters of a population with low-back pain and to assess the link. Material and methods205 patients, with a mean age of 49.6 years (range, 18–70 years), presenting chronic common low-back pain without radicular involvement, were included prospectively. Mood scores comprised: the self-administered “Hospital Anxiety and Depression Scale” (HAD), Hamilton Anxiety Scale (HAM-A), Hamilton Depression Scale (HAM-D) and Young Mania Rating Scale (YMRS). Radiological parameters, measured on lateral full-spine radiographs, included: L1-S1 lordosis, T1-T12 kyphosis, pelvic incidence, pelvic tilt, sacral slope, sagittal vertical axis (SVA), T1 slope, and Roussouly type. ResultsMean HAM-A score was 16.1; 54% of patients had scores ≥14, indicating anxiety disorder. Mean HAM-D score was 10.8; 55% of patients had scores ≥10, indicating depressive disorder. Mean YMRS score was 2.6; only 1 patient had a score ≥20, indicating manic disorder. The 112 patients with HAM-A score >14 showed mean 51.6° L1-S1 lordosis (p=0.356), 48.3° T1-T12 kyphosis (p=0.590), –4.3mm C7 SVA (p=0.900), and 29.3° T1 slope (p=0.451). In case of HAM-A <14, there were no significant differences. The 113 patients with HAM-D score >10 showed significant differences in T1-T12 kyphosis (mean 49.0°; p<0.05) and T1 slope (30.2°; p<0.05); mean L1-S1 lordosis was 50.5° (p=0.861) and C7 SVA 1.6mm (p=0.462). In case of HAM-D <10, T1-T12 kyphosis was 45.5° (p<0.05) and T1 slope 26.2° (p<0.05); mean lordosis was 50.9° (p=0.861) and mean C7 SVA –7.1mm (p=0.259). Multivariate analysis found no significant link between Roussouly type and psychiatric scores: HAD (p=0.715), HAM-A (p=0.652), and HAM-D (p=0.902). ConclusionMore than 50% of patients with common low-back pain presented a mood disorder. Depressive disorder was associated with greater T1-T12 kyphosis and T1 slope. There was no relationship between psychiatric scores and overall sagittal alignment. Level of evidenceII.

Crossing the Bridge From Degeneration to Deformity: When Does Sagittal Correction Impact Outcomes in Adult Spinal Deformity Surgery?

Patients with less severe adult spinal deformity (ASD) undergo surgical correction and often achieve good clinical outcomes. However, it is not well understood how much clinical improvement is due to sagittal correction rather than treatment of the spondylotic process. Determine baseline thresholds in radiographic parameters that, when exceeded, may result in substantive clinical improvement from surgical correction. Retrospective. ASD patients with BL and two-year data were included. Parameters assessed: sagittal vertical axis, pelvic incidence-lumbar lordosis mismatch, pelvic tilt, T1 pelvic angle, L1 pelvic angle, L4-S1 lordosis, C2-C7 sagittal vertical axis, C2-T3, C2 slope. Outcomes: Good Outcome (GO) at two years: [meeting either: (1) Substantial Clinical Benefit for Oswestry Disability Index (change >18.8), or (2) Oswestry Disability Index <15 and Scoliosis Research Society Total>4.5]. Binary logistic regression assessed each parameter to determine if correction was more likely needed to achieve GO. Conditional inference tree run machine learning analysis generated baseline thresholds for each parameter, above which, correction was necessary to achieve GO. We included 431 ASD patients. There were 223 (50%) that achieved a GO by two years. Binary logistic regression analysis demonstrated, with increasing baseline severity in deformity, sagittal correction was more often seen in those achieving GO for each parameter(all P <0.001). Of patients with baseline T1 pelvic angle above the threshold, 95% required correction to meet GO (95% vs. 54%, P <0.001). A baseline pelvic incidence-lumbar lordosis >10° (74% of patients meeting GO) needed correction to achieve GO (odds ratio: 2.6, 95% confidence interval: 1.4-4.8). A baseline C2 slope >15° also necessitated correction to obtain clinical success (odds ratio: 7.7, 95% confidence interval: 3.7-15.7). Our study highlighted point may be present at which sagittal correction has an outsized influence on clinical improvement, reflecting the line where deformity becomes a significant contributor to disability. These new thresholds give us insight into which patients may be more suitable for sagittal correction, as opposed to intervention for the spondylotic process only, leading to a more efficient utility of surgical intervention for ASD.

142. Loss of sagittal correction >3 years after adult spinal deformity surgery

<h3>BACKGROUND CONTEXT</h3> The durability of adult spinal deformity (ASD) surgery is key for cost-effective treatment. Malalignment is one of the main reasons for revision surgery. <h3>PURPOSE</h3> To investigate risk factors for loss of correction within the instrumented lumbar spine following ASD surgery. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study of a prospective database. <h3>PATIENT SAMPLE</h3> This study included 321 ASD patients with minimum 3 -year follow-up. <h3>OUTCOME MEASURES</h3> L1-S1, L4-S1 and L1-L4 lumbar lordosis. <h3>METHODS</h3> A total of 321 patients who underwent fusion of the lumbar spine (=5 levels, LIV S1/ilium) with a revision-free follow-up =3 years were identified. Patients were stratified by the change in PI-LL from 6 weeks to 3 years postop as Maintained vs Loss > 5°. Those with a loss due to instrumentation failure (broken rod, screw pullout, etc.) were excluded before comparisons. Changes in regional and focal lordosis over time were investigated with repeated measures ANOVA and factor comparison. <h3>RESULTS</h3> Mean age 64 yrs, BMI 28 kg/m², 80% female. The baseline alignment (PI-LL=21±19°, T1PA=26±12°) was corrected to PI-LL=3±13°, and T1PA=18±10° at 3 yrs (mean 3Y follow-up: 45±11m, with 44±11 mo between early and late follow-up). Eighty-two patients (25.5%) lost >5° of PI-LL correction (mean loss 10±5°). After exclusion of patients with instrumentation failure, 52 patients (Loss) with a mean loss of correction of 8.6±2.9 were compared to 222 controls with maintained LL correction. Demographics were similar between groups (age: 63 vs 61 p=0.15; Sex: 78.4% F vs 88.5% p=0.10). There were no significant differences in use of osteotomy, 3CO, and IBF between Loss and Maintained LL (all p >0.1). There was no significant difference in number of levels fused (11 vs 12 p=0.39), rod material (CoCr 59.4% vs 58.8% p=0.34), and BMP use (88.7% vs 84.6% p=0.41) but Loss had less supplemental rod use (5.8% vs 23.4% p=0.004). Comparison between Maintained and Loss revealed a similar PI-LL mismatch at pre-op (16.7±18.7 vs 20.9±18.3 p=0.14) and final postop (1.8±12.5 vs 5.1±14.5 p=0.11) but a significantly smaller PI-LL for Loss at early postop (0.6±12.8 vs -3.5±13.7 p=0.41). Distally, Maintained had a significant improvement in L4-S1 lordosis from preop to early postop (p=0.013), with no significant difference from early to final follow-up. In contrast, patients in the Loss group had no difference in L4-S1 from preop to early postop (p=0.14), but showed a significant loss of correction at 3 years (p <0.001). Proximally, significant increase between pre and early postop in L1-L4 (all p <0.001), with Loss and Maintained reaching similar early postop value (p=0.34). However, from early postop to final follow up, Loss showed a significant decrease in proximal lordosis (p <0.001) while Maintained did not (p=0.08), corresponding with a smaller absolute L1-L4 in the Loss cohort at 3 yrs (p=0.002). Screw orientation showed a significant decrease from early to late follow-up between the L1 and S1 screws for Loss (1.3±4.1 p=0.031), without any changes across the L4-S1 segment (-0.1±2.9 p=0.97). <h3>CONCLUSIONS</h3> Approximately a quarter of patients lose an average of 10° of their 6-week correction by 3 years. Lordosis is lost proximally through the instrumentation (ie, tulip/shank angle shifts and/or rod bending), but lost distally through bone "settling" through the instrumentation itself. The use of supplemental rods and avoiding sagittal overcorrection may help mitigate this loss. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

131. Sagittal profile modifications in vertebral body tethering (VBT) versus posterior spinal fusion (PSF) in adolescent idiopathic scoliosis (AIS)

<h3>BACKGROUND CONTEXT</h3> Sagittal alignment is integral to a patient's quality of life. Posterior spinal fusion (PSF) is currently the standard for correcting adolescent idiopathic scoliosis (AIS). Vertebral body tethering (VBT) is a fusionless growth modulating surgical technique used to treat AIS. It relies on the Hueter-Volkmann Law. Indications for this procedure include patients who have coronal curves up to 50°, growth remaining, and no excessive thoracic kyphosis. VBT has been shown to have good coronal plane deformity correction. There have been fewer examinations of the sagittal effects of VBT. <h3>PURPOSE</h3> To determine if VBT is a non-inferior treatment for correction of AIS with regard to sagittal alignment compared to PSF. <h3>STUDY DESIGN/SETTING</h3> Multicenter retrospective cohort study. <h3>PATIENT SAMPLE</h3> Patients with AIS who underwent correction surgeries with LIV in the lumbar spine from 2013 to 2021 with pre- and minimum two-year postoperative standing full spine plain films. <h3>OUTCOME MEASURES</h3> Sagittal vertical axis (SVA), cervical SVA (cSVA), pelvic tilt (PT), thoracic kyphosis (TK), cervical lordosis (CL), L4-S1 lordosis (L4L), T1 pelvic angle (TPA) and pelvic incidence lumbar lordosis mismatch (PI-LL). <h3>METHODS</h3> Radiographic analyses was completed with independent samples t-test with significance set to p <0.05. <h3>RESULTS</h3> A total of 99 patients were included, 49 VBT and 50 PSF. There were no differences in age or levels instrumented between groups. The VBT cohort Lenke class breakdown is 23% 1A, 13% 1C, 31% 3C. 18% 5C, and 15% 6C, while the PSF cohort consisted of 42% 1A, 6% 1B, 2% 2C, 2% 3B, 12% 3C, 2% 5B, 24% 5C, and 10% 6C. At Baseline, the VBT cohort had lower SVA (-0.7mm±3.7 vs 2.2mm±5.0, p=0.001), CL (-0.9°±18.2 vs 11.6°±12.8, p=0.001), L4-S1 Lordosis (20.7°±16.0 vs 41.6°±10.2, p=0.001), and higher cSVA (3.3mm±1.6 vs -0.95mm±3.1, p=0.001) than those who were fused. Postoperatively, VBT patients have an overall higher L4-S1 Lordosis (36.0°±10.1vs 18.3°±12.5, p=0.001), cSVA (3.4mm±1.4 vs -3.7mm±2.1, p=0.001), and lower CL (-4.3°±18.4 vs 7.0°±12.2, p=0.001). The PSF cohort had a larger change in cSVA (2.8mm±4.0 vs 0mm±1.6, p=0.001) from baseline to 2-year follow-up compared to VBT. No differences in the change of L4-S1 Lordosis (VBT 1.5°±12.3 vs 4.1°±10.9, p=0.3), TPA (VBT -1.6°±6.8 vs -1.4°±8.5, p=0.89), PT (VBT -0.5°±7.8 vs -1.9°±8.5, p=0.42), or PI-LL (0.2°±12.0 vs -0.5°±14.0, p=0.81) were observed. <h3>CONCLUSIONS</h3> VBT and PSF for AIS result in statistically similar changes in sagittal alignment parameters. The fact that we showed similar results comparing sagittal alignment in fusion and VBT groups indicates that VBT is non-inferior from a sagittal perspective. It is important to maintain sagittal alignment when correcting AIS. Future work can examine the long-term effect of VBT on sagittal alignment. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

P104. Crossing the bridge from degeneration to deformity: when good outcomes necessitate sagittal correction in adult spinal deformity surgery

BACKGROUND CONTEXT Patients with less severe adult spinal deformity undergo surgical correction and often achieve good clinical outcomes. However, it is not well understood how much clinical improvement is due to sagittal correction. PURPOSE Derive baseline thresholds in radiographic parameters that, when exceeded, result in dramatic clinical improvement from surgical correction. STUDY DESIGN/SETTING Retrospective. PATIENT SAMPLE A total of 689 ASD patients. OUTCOME MEASURES Radiographic alignment, clinical outcomes (ODI SCB). METHODS ASD patients with BL and 2-year (2Y) data included. Parameters assessed: SVA, PI-LL, PT, T1PA, L4-S1 Lordosis, C2-C7 SVA (cSVA), C2-T3 and C2 Slope (C2S). Outcomes: Good Outcome (GO): [Meeting either: 1) SCB for ODI by 2Y (change greater than 18.8), or 2) ODI 4.5 by 2Y. Binary logistic regression assessed each parameter to determine if correction was more likely needed to achieve GO. Conditional inference tree (CIT) run machine learning analysis generated baseline thresholds for each parameter, above which, correction was necessary to achieve GO. RESULTS Included: 447 ASD patients. There were 223 (50%) patients achieving GO by 2 years. Binary logistic regression analysis demonstrated correction of all 5 thoracolumbar parameters (SVA, T1PA, PI-LL, PT, L4-S1) were more often needed to achieve GO (all p.001). Of patients with baseline T1PA above 20°, 95% required correction to meet Good Outcome (95% vs 54%, p.001). CIT-generated thresholds were significant for each parameter, with a baseline C2 slope above 15° necessitating correction more often to obtain clinical success (OR: 8.1, [4.1-16.2]; p.001). CONCLUSIONS Our study highlights there is a tipping-point beyond which sagittal correction has an exponential influence on clinical improvement, reflecting the line where deformity becomes a significant contributor to disability. These new thresholds delineate patients suitable for sagittal correction, as opposed to conventional treatment of degenerative disc processes. Adherence to these benchmarks may improve the utility gained from surgical intervention for degenerative conditions and deformity. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. Patients with less severe adult spinal deformity undergo surgical correction and often achieve good clinical outcomes. However, it is not well understood how much clinical improvement is due to sagittal correction. Derive baseline thresholds in radiographic parameters that, when exceeded, result in dramatic clinical improvement from surgical correction. Retrospective. A total of 689 ASD patients. Radiographic alignment, clinical outcomes (ODI SCB). ASD patients with BL and 2-year (2Y) data included. Parameters assessed: SVA, PI-LL, PT, T1PA, L4-S1 Lordosis, C2-C7 SVA (cSVA), C2-T3 and C2 Slope (C2S). Outcomes: Good Outcome (GO): [Meeting either: 1) SCB for ODI by 2Y (change greater than 18.8), or 2) ODI 4.5 by 2Y. Binary logistic regression assessed each parameter to determine if correction was more likely needed to achieve GO. Conditional inference tree (CIT) run machine learning analysis generated baseline thresholds for each parameter, above which, correction was necessary to achieve GO. Included: 447 ASD patients. There were 223 (50%) patients achieving GO by 2 years. Binary logistic regression analysis demonstrated correction of all 5 thoracolumbar parameters (SVA, T1PA, PI-LL, PT, L4-S1) were more often needed to achieve GO (all p.001). Of patients with baseline T1PA above 20°, 95% required correction to meet Good Outcome (95% vs 54%, p.001). CIT-generated thresholds were significant for each parameter, with a baseline C2 slope above 15° necessitating correction more often to obtain clinical success (OR: 8.1, [4.1-16.2]; p.001). Our study highlights there is a tipping-point beyond which sagittal correction has an exponential influence on clinical improvement, reflecting the line where deformity becomes a significant contributor to disability. These new thresholds delineate patients suitable for sagittal correction, as opposed to conventional treatment of degenerative disc processes. Adherence to these benchmarks may improve the utility gained from surgical intervention for degenerative conditions and deformity.

Impact of Patient-specific Factors and Spinopelvic Alignment on the Development of Adjacent Segment Degeneration After Short-segment Lumbar Fusion.

Prospective cross-sectional cohort study. The main purpose of this study was to evaluate the association between demographical, surgery-related and morphologic parameters, and the development or progress of adjacent segment degeneration (ASD) after short-segment lumbar fusions. ASD is a major long-term complication after lumbar fusions. Possible risk factors are related to the patients' demographics, spinopelvic anatomy, or preoperative lumbar intervertebral disk conditions, but the role of these parameters is still not clear. A prospective cross-sectional study of 100 patients who underwent 1- or 2-level open lumbar transforaminal interbody fusions due to a lumbar degenerative pathology was conducted. Demographical, radiologic findings, and magnetic resonance imaging features were analyzed to identify factors associated with ASD in 5-year follow-up. ASD patients showed higher level of pain ( P =0.004) and disability ( P =0.020) at follow-up. In univariate analysis, older age ( P =0.007), upper-level lumbar fusion ( P =0.007), lower L4-S1 lordosis ( P =0.039), pelvic incidence-lumbar lordosis mismatch ( P =0.021), Pfirrmann grade III or higher disk degeneration ( P =0.002), and the presence of disk bulge/protrusion ( P =0.007) were associated with ASD. In multivariate analysis, the presence of major degenerative sign (disk degeneration and/or disk bulge) was the significant predictor for developing ASD (odds ratio: 3.85, P =0.006). By examining the role of different patient- and procedure-specific factors, we found that preoperative major degenerative signs at the adjacent segment increase the risk of ASD causing significantly worse outcome after short-segment lumbar fusion. On the basis of our results, adjacent disk conditions should be considered carefully during surgical planning.