Lordosis Distribution Research Articles

Do Age-Related Variations Of Sagittal Alignment Rely On SpinoPelvic Organization? An Observational Study Of 1540 Subjects.

Descriptive radiographic analysis of a prospective multi-center database. This study aims to provide normative values of spinopelvic parameters and their correlations according to age and pelvic incidence (PI) of subjects without spinal deformity. After Institutional Review Board (IRB) approval, 1540 full spine radiographs were analyzed. Subjects were divided into 3 groups of PI: low PI < 45°, intermediate PI 45-60°, high PI > 60°, and then stratified by age (20-34, 35-49, 50-64, > 65 Y.O). Pelvic and spinal parameters were measured. Statistical analysis between parameters was performed using Bayesian inference and correlation. Mean age was 53.5years (845 females, 695 males, range 20-93years).In low PI group, lumbar lordosis (LL) decrease was mainly observed in the 2 younger age groups.In medium and high PI groups, loss of lordosis was linear during aging and occurred mainly on the distal arch of lordosis. Moderate PI group had a stable lordosis apex and thoracolumbar inflection point. High PI group had a stable thoracolumbar inflection point and a more distal lordosis apex in elderly subjects.For all subjects, kyphosis and pelvic tilt (PT) increased with age.There was a constant chain of correlation between PI and age groups. Proximal lumbar lordosis (PLL) was correlated with kyphosis and sagittal vertical axis (SVA C7), while the distal lumbar lordosis (DLL) was correlated with PI and PT. This study provides a detailed repository of sagittal spinopelvic parameters normative values with detailed analysis of segmental kyphosis and lordosis distribution according to gender, age, and PI.

Correlation between lordosis distribution index, lordosis tilt, and occurrence of proximal junctional kyphosis following surgery for adult degenerative scoliosis.

This study aimed to evaluate the effect of postoperative reciprocal progression of Lordosis tilt (LT), Lordosis distribution index (LDI) and occurrence of Proximal junctional kyphosis (PJK) following surgery for Degenerative lumbar scoliosis (DLS). A total of 122 consecutive patients with ADS were treated with correction of deformity and followed up for a minimum of 2years. Spinopelvic parameters were measured preoperatively, postoperatively, and at the latest follow-up. The Japanese Orthopaedic Association score, Oswestry Disability Index, and visual analog scale scores were measured at the latest follow-up. Associations between LT, LDI, and PJK were analyzed using receiver operating characteristic analyses. The prevalence of PJK in the present study was 24.6%. The outcomes of patients with PJK were significantly worse than those of patients without PJK. Postoperative reciprocal progression in LT and LDI with lumbar lordosis restorative surgery was observed. Preoperative risk factors for PJK were older age, larger LT, and larger Cobb angle of the curves. Postoperative risk factors for PJK included postoperative LT and postoperative Cobb angle of the curves, which were smaller than those preoperatively. We found a strong correlation between postoperative LT and Cobb angle of the curves resulting in PJK. Patients with LT < -8° were at a higher risk of PJK. LT can be used to predict the occurrence of PJK in patients undergoing surgery for DLS. Appropriate postoperative LT is crucial for preventing the progression of PJK.

The changes of the distribution of lumbar lordosis after total hip arthroplasty

The changes of the distribution of lumbar lordosis after total hip arthroplasty

Lordosis Distribution Index in Short-Segment Lumbar Spine Fusion - Can Ideal Lordosis Reduce Revision Surgery and Iatrogenic Deformity?

ObjectiveThe demand for spinal fusion is increasing, with concurrent reports of iatrogenic adult spinal deformity (flatback deformity) possibly due to inappropriate lordosis distribution. This distribution is assessed using the lordosis distribution index (LDI) which describes the upper and lower arc lordosis ratio. Maldistributed LDI has been associated to adjacent segment disease following interbody fusion, although correlation to later-stage deformity is yet to be assessed. We therefore aimed to investigate if hypolordotic lordosis maldistribution was associated to radiographic deformity-surrogates or revision surgery following instrumented lumbar fusion. MethodsAll patients undergoing fusion surgery (≤ 4 vertebra) for degenerative lumbar diseases were retrospectively included at a single center. Patients were categorized according to their postoperative LDI as: “normal” (LDI 50–80), “hypolordotic” (LDI<50), or “hyperlordotic” (LDI>80). ResultsWe included 149 patients who were followed for 21±14 months. Most attained a normally distributed lordosis (62%). The hypolordotic group had increased postoperative pelvic tilt (PT) (p<0.001), pelvic incidence minus lumbar lordosis (PI–LL) mismatch (p<0.001) and decreased global lordosis (p=0.007) compared to the normal group. Survival analyses revealed a significant difference in revision surgery (p=0.03), and subsequent multivariable logistic regression showed increased odds of 1-year revision in the hypolordotic group (p=0.04). There was also a negative, linear correlation between preoperative pelvic incidence (PI) and postoperative LDI (p<0.001). ConclusionIn patients undergoing instrumented lumbar fusion surgery, hypolordotic lordosis maldistribution (LDI<50) was associated to increased risk of revision surgery, increased postoperative PT and PI–LL mismatch. Lordosis distribution should be considered prior to spinal fusion, especially in high PI patients.

187. Lumbar lordosis is primarily lost in the upper lumbar spine in ASD patients with sagittal deformities

<h3>BACKGROUND CONTEXT</h3> In asymptomatic individuals, two-thirds of the lordosis comes from the L4-S1 level. It is commonly believed that the majority of loss of lordosis in adult spinal deformity (ASD) is attributable to the distal (L4-S1) levels. <h3>PURPOSE</h3> This study aims to investigate the location of loss of lordosis in a cohort of ASD patients prior to surgical intervention. <h3>STUDY DESIGN/SETTING</h3> Retrospective review of prospective databases. <h3>PATIENT SAMPLE</h3> This study included 119 symptomatic adult volunteer and 357 adult spinal deformity patients. <h3>OUTCOME MEASURES</h3> Regional and focal alignment. Lordosis distribution. <h3>METHODS</h3> A registry of asymptomatic volunteers was used to build age and pelvic incidence (PI) adjusted normative models of PI-LL, L1-L4 lordosis, L4-S1 lordosis, TL kyphosis (T10-L2), and thoracic kyphosis (T1-T12). Our study cohort was a registry of surgical primary ASD patients without coronal malalignment (SRS-Schwab Type=N). The formulas developed in the asymptomatic population were applied to the ASD group to calculate normative values for each patient. The ASD population was divided into four groups based on quartiles of PI-LL: no, mild, moderate, and severe PI-LL mismatch. Within each group, paired t-tests were performed to compare actual and calculated normative sagittal alignment; actual alignment was also expressed in percentage of normative values. The level of significance was p<0.05. <h3>RESULTS</h3> The asymptomatic cohort used included 119 asymptomatic volunteers (50.7yo±17, PI: 52°±11.4) with the following regional alignment: L4-S1=34°, L1-L4=23°, TKL=3°, and TK=49°. The study cohort included 357 ASD patients (64.6yo, 58.5%F). The PI-LL of the 4 quartiles were -10°, 10°, 20°, and 40°. There were no significant differences in PI or in any of the coronal Cobb angles. Comparing each ASD group to the calculated normative values; the "no mismatch" group had a greater L4-S1 (+8°), a greater T10-L2 kyphosis (+14°) and T1-T12 kyphosis (+8°), but no difference in L1-L4. The "mild mismatch" group had a smaller L1-L4 (-12°), greater TLK (+5°), smaller TK (-7°) and no difference in L4-S1. The "moderate mismatch" had a smaller L4-S1 (-7°), L1-L4 (-15°), TK (-15°) but no difference in TLK. Finally, the "severe mismatch" group had a smaller L4-S1 (-15°), L1-L4 (-26°), and TK (-27°) but no difference in TKL (all with p<0.001). The analysis by percentage of actual alignment vs the calculated age and PI matched normative values permitted to identify the driver(s) of the sagittal malalignment. The "no mismatch" had an excess of TLK (+510%) compensated by an excess in L4-S1 (+27%). The "mild mismatch" had a loss of L1-L4 (-48%) with a normal L4-S1, while the "moderate mismatch" had mainly a deficit in L1-L4 (-66%) associated to a 22% loss on L4-S1. Finally, "severe-mismatch" presented a kyphotic L1-L4 (-115% vs norm) with a 46% deficit in L4-S1 <h3>CONCLUSIONS</h3> In this cohort of ASD patients with limited coronal deformity, the majority of the loss of lordosis is attributable to the proximal segment. As the deformity worsened, the loss of lordosis also involved the distal lumbar segments. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

52. Upper vs lower lumbar lordosis corrections in relation to pelvic tilt: An essential element in surgical planning for sagittal plane deformity

<h3>BACKGROUND CONTEXT</h3> The distribution of lumbar lordosis (LL) between L1-4 and L4-S1 is known to vary based on pelvic incidence (PI). However, the extent to which regional changes effect pelvic tilt (PT) is not clearly elucidated. This information can be useful for adult spinal deformity (ASD) surgical planning. <h3>PURPOSE</h3> To investigate the change in pelvic tilt (PT) imparted by regional changes in LL at 2-year minimum follow-up. <h3>STUDY DESIGN/SETTING</h3> Retrospective study of a multicenter ASD database. <h3>PATIENT SAMPLE</h3> A total of 103 ASD patients. <h3>OUTCOME MEASURES</h3> Radiographic parameters. <h3>METHODS</h3> Operative patients from a multicenter ASD database were included with LIV S1/Ilium, >5 levels of fusion, PJK angle <20 and >5° of change from L4-S1 and L1-4. Patients with PJK angles >20 were excluded due to the compensatory effect this has on PT. Radiographic analysis was performed evaluating thoracic kyphosis (TK), T10-L2 (TL), L1-S1 (LL), L4-S1, L1-4, SVA and PI-LL from pre- to postoperative and change at 2-year follow-up. Paired t-tests were utilized to analyze the change in parameters and HRQOLs at 2-year follow up. Stepwise regression analysis was performed in order to determine the relationship between PT and the above radiographic parameters. HRQOLs (ODI, PCS, MCS, SRS-22r) were also compared between pre- and postoperative timepoints at 2 years. <h3>RESULTS</h3> A total 103 patients met inclusion for the study. Paired t-tests demonstrated improvements in all the radiographic parameters (TK 30.1 vs 49.8, SVA 122 vs 28, LL 19.4 vs 51.9, PI-LL 35.2 vs 3.2, p<0.01) and HRQOLs at 2 year follow up respectively (ODI 47.9 vs 28.1, PCS 28.0 vs 39.9, MCS 45.9 vs 51.5, SRS-22r 2.6 vs 3.7, p<0.01). TL was not significantly different at 2 years (11.2 vs 8.6, p=0.14). Stepwise regression model showed an inverse relationship between PT and LL change (r=0.71, p<0.01). Regionally, an increase in 10° from L4-S1 correlated with a 2.4° decrease in PT (p<0.01), while an increase in 10° from L1-4 resulted in a 1.6° decrease in PT (p<0.01). <h3>CONCLUSIONS</h3> In the surgical planning for ASD, our data demonstrated significant correlational difference between corrections in the upper (L1-4) and lower (L4-S1) lumbar spine and PT changes. These calculations can be useful in planning sagittal plane corrections for ASD and are analogous to prior literature on alignment changes after 3CO in the lumbar spine. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

P91. How does gravity influence the distribution of lordosis in sagittal malalignment?

<h3>BACKGROUND CONTEXT</h3> Supine imaging reveals the contour of the spine without gravity, a key consideration in surgical planning. Comparing supine to standing radiographs may reveal differences in regional flexibility in adult spinal deformity (ASD). <h3>PURPOSE</h3> To determine differences in regional flexibility of the lumbar spine in patients with ASD. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study. <h3>PATIENT SAMPLE</h3> Fifty-six patients with sagittal ASD (SRS-Schwab Type N, no previous fusion) and 119 asymptomatic volunteers. <h3>OUTCOME MEASURES</h3> PI-LL, L1-L4, and L4-S1 alignment. <h3>METHODS</h3> Asymptomatic volunteers underwent full length standing radiographs, ASD patients had standing and supine radiographs taken for preoperative planning. The standing alignment of the asymptomatic volunteers (50.7±17 years, PI 52±11.4°) was analyzed using linear regression in order to calculate PI-based formulas for normative, age-adjusted standing PI-LL, L4-S1, and L1-L4. These formulas were applied to the ASD cohort and compared to their standing and supine alignment. Given the potential for confounding by ASD patients with stiff lumbar spines, analyses were repeated in a cohort of 25 patients with at least 5° of flexibility (defined as the difference between supine and standing lordosis) and 5 degrees of offset from regional alignment norms. <h3>RESULTS</h3> Linear regression in the asymptomatic cohort resulted in the following PI based formulas: PI-LL= -38.3 +0.41*PI +0.21*Age, L4-S1= 45.3 -0.18*Age, L1-L4= -3 + 0.48*PI). The ASD cohort had a mean age of 65±14 years, BMI 29±7 kg/m2, standing PI-LL 14±22°, T1PA 22±11°). Eighty-seven percent of patients had a lordotic apex between the L3-L4 inferior endplates. PI-LL improved with supine positioning (mean 8.9±18.7°, p<0.001), though not enough to correct to age-matched norms (mean offset 12.2±16.9°). Compared to mean normative alignment at L1-L4 (22.1±6.2°), L1-L4 was flatter on standing (7.2±17.0°, p<0.001) and supine imaging (8.5±15.0°, p<0.001) while L4-S1 was comparable (norm 33.6±2.6 vs standing 30.9±12.9, p=0.325; vs supine 34.5±10.3, p=1.000). Subgroup analysis of subjects with L1-S1 flexibility >5° demonstrated a more dramatic effect—the standing loss of lordosis (32.6±1.7° norm vs 25.5±12.7° standing, p=0.031) at L4-S1 corrected on supine imaging (33.9±11.1°, p=1.000), while L1-L4 alignment did not (23.0±6.2° norm vs 2.2±14.4° standing, p<0.001; vs 7.3±12.9° supine, p<0.001). <h3>CONCLUSIONS</h3> When the effect of gravity is removed, the distal portion of the lumbar spine (i.e., below the apex of lordosis) corrects, suggesting that deformity is contained in the proximal lumbar region. These findings illuminate the etiology of lumbar hypolordosis and may influence selection of fusion levels. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

P107. Impact of upper instrumented vertebra and lordosis morphology on acute proximal junctional fracture following adult spinal deformity surgery

<h3>BACKGROUND CONTEXT</h3> Acute proximal junctional Fracture (PJF) is a challenging complication of adult spinal deformity (ASD) surgery. Upper instrumented vertebra (UIV) orientation has been proposed as a risk factor of acute PJF. Adjust UIV orientation by lordosis morphology during ASD surgery could reduce the occurrence of acute PJF. <h3>PURPOSE</h3> The purpose of this study is to analysis the effect of UIV orientation on acute PJF. And we tried to find out the relationship between UIV orientation and lordosis morphology. This strategy is thought to reduce acute PJF by adjusting lordosis morphology during surgery. <h3>STUDY DESIGN/SETTING</h3> A retrospective study. <h3>PATIENT SAMPLE</h3> A total of 187 patients (mean age 71.7 years) ASD patients underwent long-segment fusion from thoracolumbar vertebra to pelvis and followed up for more than 1 year. <h3>OUTCOME MEASURES</h3> Description and analysis of X-ray changes. <h3>METHODS</h3> Comparative analysis was performed on spinopelvic parameters including UIV parameters (UIV slope angle and horizontal distance from UIV center to C7 plumb line[C7PL]) between PJF and non-PJF group. And correlation analysis between UIV parameters and lordosis morphologic parameters (postoperative lumbar lordosis, lordosis correction degree, lordosis apical vertebra level and lordosis distribution index [LDI]) were performed. <h3>RESULTS</h3> Acute PJF incidence was 17.2% (32/187). PJF group had more UIV slope (20.6° vs 18.6°, p=0.045) and PJF group's UIV was located more posteriorly (-5.6mm vs +11.4mm, p<0.001). In condition that UIV slope was above 18.6° and UIV was located behind C7PL, acute PJF incidence was 75.0% (15/20). In condition that UIV slope was less than 18.6° and UIV was located in front of C7PL, acute PJF incidence was 1.9% (1/54). In correlation analysis, UIV slope had significant correlation with postoperative lumbar lordosis (r=0.422, p<0.01) and lordosis correction degree (r=0.239, p<0.05). And UIV-C7PL distance had significant negative correlation with apical vertebra level (r=-0.243, p<0.01) and LDI (r=-0.260, p<0.01). <h3>CONCLUSIONS</h3> UIV with large slope and located behind C7PL increases the risk of acute PJF occurrence. To avoid this situation while preserving sufficient lordosis correction, proper proximal rod contouring is needed to reduce UIV slope. And proper apical vertebra positioning and LDI lowering is needed to place UIV anteriorly. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

P87. Global alignment and proportion (GAP) score with modified RSA parameter: GAP-R score

P87. Global alignment and proportion (GAP) score with modified RSA parameter: GAP-R score

Comparison of degenerative lumbar scoliosis correction and risk for mechanical failure using posterior 2-rod instrumentation versus 4-rod instrumentation and interbody fusion.

Four-rod instrumentation and interbody fusion may reduce mechanical complications in degenerative scoliosis surgery compared to 2-rod instrumentation. The purpose was to compare clinical results, sagittal alignment and mechanical complications with both techniques. Full spine radiographs were analysed in 97 patients instrumented to the pelvis: 58 2-rod constructs (2R) and 39 4-rod constructs (4R). Clinical scores (VAS, ODI, SRS-22, EQ-5D-3L) were assessed preoperatively, at 3 months, 1 year and last follow-up (average 4.2 years). Radiographic measurements were: thoracic kyphosis, lumbar lordosis, spinopelvic parameters, segmental lordosis distribution. The incidence of non-union and PJK were investigated. All clinical scores improved significantly in both groups between preoperative and last follow-up. In the 2R-group, lumbar lordosis increased to 52.8° postoperatively and decreased to 47.0° at follow-up (p = 0.008). In the 4R-group, lumbar lordosis increased from 46.4 to 52.5° postoperatively and remained at 53.4° at follow-up. There were 8 (13.8%) PJK in the 2R-group versus 6 (15.4%) in the 4R-group, with a mismatch between lumbar apex and theoretic lumbar shape according to pelvic incidence. Non-union requiring revision surgery occurred on average at 26.9 months in 28 patients (48.3%) of the 2R-group. No rod fracture was diagnosed in the 4R-group. Multi-level interbody fusion combined with 4-rod instrumentation decreased risk for non-union and revision surgery compared to select interbody fusion and 2-rod instrumentation. The role of additional rods on load sharing still needs to be determined when multiple cages are used. Despite revision surgery in the 2R group, final clinical outcomes were similar in both groups. III.

Optimal Correction of Adult Spinal Deformities Requires Restoration of Distal Lumbar Lordosis.

Purpose The aim of this study is to analyze results according to postoperative pelvic incidence-lumbar lordosis (PI-LL) mismatch in the management of adult spine deformity (ASD) patients. Recently, it has been reported that in addition to lumbar lordosis amount, lordosis repartition between its proximal and distal parts was crucial. Methods We enrolled 77 consecutive ASD patients who underwent posterior spinal fusion and deformity correction between 2015 and 2018. On preoperative and 1-year follow-up radiographs, we analyzed different parameters such as L1-S1 lumbar lordosis, L1-L4 proximal lordosis (PLL), L4-S1 distal lordosis (DLL), pelvic tilt (PT), sagittal vertical axis (SVA), and PI-LL mismatch. Comparisons were performed according to postoperative PI-LL mismatch (defined as “aligned” when PI-LL was <10°). The relationship between lordosis distribution and postoperative alignment status was investigated. Results On the whole series, average lumbar lordosis, SVA, and PI-LL improved (28.2° vs.43.5°, 82 vs. 51 mm, and 26°vs. 14°, all p < 0.001, respectively). On the other hand, PT remained unchanged (30° vs. 28°, p > 0.05). 35 patients were classified as “aligned” and 42 as “not aligned.” Patients from the “aligned” group had a significantly lower PI than patients from the “not aligned” group (52° vs. 61°, p=0.009). Postoperative PLL was not different between groups (18° vs. 16° p > 0.05), whereas DLL was significantly higher in the “aligned” group (31° vs. 22°, p=0.003). PI-LL was significantly correlated to DLL (rho = 0.407, p < 0.001) but not with PLL (rho = 0.110, p=0.342). Conclusions Our results revealed that in ASD patients, postoperative malalignment was associated with a lack of DLL restoration. “Not aligned” patients had also a significantly higher pelvic incidence. Specific attention must be paid to restore optimal distal lumbar lordosis in order to set the amount and the distribution of optimal postoperative lumbar lordosis.

Thoracic Kyphosis and Lumbar Lordosis Distribution After Idiopathic Scoliosis Correction Using Posterior Hybrid Versus Screw Instrumentation.

This was a retrospective observational study. The aim of this study was to evaluate kyphosis and lordosis distribution, inflexion points, and the relationship with proximal junctional kyphosis (PJK) comparing hybrid instrumentation (in situ contouring, derotation) versus screw instrumentation (thoracic cantilever reduction, lumbar in situ contouring, and derotation). The combination of reduction techniques aims at restoring the levels of lumbar apex and thoracolumbar inflexion point according to Roussouly alignment types. This approach could minimize the PJK risk after adolescent idiopathic scoliosis (AIS) surgery. The study assessed coronal curve correction, thoracolumbar and spinopelvic sagittal parameters in 86 skeletally mature adolescents and young adults 2.2 years after AIS correction, comparing a hybrid group (HG, n=34) to a screw group (SG, n=52). Segmental kyphosis and lordosis distribution, number of vertebrae included in curves, thoracic and lumbar apex, thoracolumbar inflexion point and Roussouly types were modeled using KEOPS software. Global coronal and sagittal correction were similar in both groups. In the SG, lumbar lordosis (LL) decreased from 61.1 to 53.9 degrees (P<0.0001) and matched with pelvic incidence (r=0.69), whereas LL did not change in the HG. Postoperatively, the thoracolumbar inflexion point migrated cranially, resulting in a longer LL in both groups. Postoperative thoracolumbar inflexion point (P<0.0001) and the lumbar apex (P=0.0274) were more caudal in the SG compared with the HG. The PJK rate was 14.7% in the HG and 7.7% in the SG. In patients with PJK, lumbar apex and thoracolumbar inflexion point shifted cranially and were too high according to the Roussouly type. Hybrid and screw instrumentation led to similar global AIS correction, but the use of cantilever reduction in the SG allowed setting the thoracolumbar inflexion point and the lumbar apex lower than in the HG. Cranial migration of these points was identified as PJK risk factor. Level III.

Static and dynamic sagittal lumbar apex: a new concept for the assessment of lumbar lordosis distribution in spinal deformity.

Sagittal lumbar apex has been demonstrated to be a key parameter in sagittal plane morphology. Our aim was to understand its behavior with postural changes, analyzing two different concepts of lumbar apex. Prospective observational study with a cohort of patients presenting sagittal malalignment identified from a monocenter database of adult spinal deformities (ASD). Inclusion criteria were age > 30years, SVA > 40mm, and/or PT > 20. All patients had full-spine EOS radiographs in 2 different positions: (P1: natural position) and position 2 (P2: compensated position). Sagittal alignment, spinopelvic values, and two different methods of assessing lordosis apex location were analyzed in both P1 and P2 positions. Changes between P1 and P2 were compared using a paired t test with a significance level at p < 0.05. Twenty-five patients were recruited (21 women and 4 men). The mean age was 64.8years (range 21-79). The patient's main compensation was based on an increase in the femoral shaft angle, and pelvic retroversion, with a subsequent decrease in sacral slope, and therefore of the lower lumbar arc. When the lumbar apex was calculated as the most anterior point touching the vertical line in a lateral radiograph, postural compensation changes modified its location usually shifting it to a more caudal position. When the lumbar apex was assessed as the most distant point of the global lumbar lordosis, its position remained stable regardless of compensation. Postural changes can modify the location of the lumbar apex when understanding its location as the cornerstone of sagittal plane harmonic distribution. This concept can be useful as an additional sign to assess compensation. However, if the lumbar apex was calculated as the angular point of the global lordosis, its position remained stable regardless of postural changes. This concept can help to mold lumbar lordosis in ASD surgery. Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Static and dynamic sagittal lumbar apex: A new concept for the assessment of lumbar lordosis distribution in spinal deformity

Static and dynamic sagittal lumbar apex: A new concept for the assessment of lumbar lordosis distribution in spinal deformity

Radius of Curvature in Patient-Specific Short Rod Constructs Versus Standard Pre-Bent Rods.

Recent studies support the need for sagittal alignment restoration when performing lumbar degenerative spinal fusions. The development of patient-specific spine rods (PSSRs) may help maintain or improve sagittal alignment in these surgeries. A retrospective review was conducted for patients who underwent posterior spinal surgeries involving 4 or less levels. The preplanned PSSR radii of curvature (ROC) was compared with standard prebent rods with a ROC of 125 mm. All surgeries were performed at a single institution by 3 surgeons from September 2016 through October 2018. Data were then compared using a 2-tailed paired t test. PSSR had either 1 or 2 definitive ROCs. For rods with 2 ROCs, the "cranial" curve was measured between the upper instrumented level and L4 or L5. The "caudal" curve was measured between L4 or L5 and the lower instrumented level. The PSSR with 1 ROC and the caudal portion of the rods with 2 ROCs were significantly smaller than the industry standard ROC. PSSR demonstrate more acute ROC than industry standard rods. In PSRs, the most lordosis occurs between L4-S1 and flattens out at the thoracolumbar junction, mimicking the normal distribution of lumbar lordosis. PSSRs could help achieve or maintain sagittal alignment and prevent the sequela of flat back syndrome.

129. GAP score with modified relative pelvic version (RPV) parameter: GAP-V score

BACKGROUND CONTEXT The global alignment and proportion (GAP) score was thus developed to predict such mechanical complications following spinal correction surgery. The GAP score is a pelvic-incidence based method of analyzing the sagittal plane. GAP scores of 0∼2 are classified as proportioned, 3∼6 as moderately proportioned, and >=7 as severely disproportioned. GAP parameters include relative pelvic version (RPV), relative lumbar lordosis, lordosis distribution index, age factor of 60, and relative spinopelvic alignment. RPV categories include: 5° receiving a score of 1. PURPOSE The aim of the study was to adjust the RPV parameter in calculation of GAP scores among US adult volunteers with no prior spinal pathology, in order to compensate for high GAP scores in otherwise healthy individuals. STUDY DESIGN/SETTING Retrospective review of prospectively collected data. PATIENT SAMPLE This study included 87 healthy volunteers were included in the study. Mean age was 54.9±15.1 (20-84) years. Exclusion criteria included any major spinal pathology or surgery, terminal illness, morbid obesity, or any significant comorbid condition. OUTCOME MEASURES GAP scores with RPV parameter removed and GAP-V scores. METHODS Preliminary GAP scores with the RPV parameter removed were assessed in 87 healthy volunteers that met inclusion criteria. The preliminary GAP scores were grouped based on the original GAP system's RPV parameters, and these scores were analyzed to search for discrepancies from the baseline trend. Original GAP scores were calculated for the same 87 healthy volunteers. GAP-V scores were calculated with the same parameters as the GAP score, with the exception of the RPV factor. In GAP-V scores, the number of points were subtracted from each RPV group in the same amount that showed discrepancies in the preliminary GAP score trend. The percentages of Proportioned, Moderately Disproportioned, and Severely Disproportioned volunteers were then compared between the two scoring systems. RESULTS Preliminary GAP scores show a 1-point and 5-point discrepancy point in the -15°∼ -7.1° and CONCLUSIONS Our study examined the RPV parameter in calculation of GAP scores in a healthy US population. In this study, we analyzed how the GAP score system may be attributing a high score to otherwise healthy individuals. We found the percentage of proportioned volunteers increases in the original GAP score by subtractions at RPV groups -15°∼ -7.1° and FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

291. Adjustment of the global alignment and proportion scores accounting for frailty in adult spinal deformity surgical patients

BACKGROUND CONTEXT Frailty is a baseline measure of disability that transcends age alone and has been determined a strong predictor of outcomes following adult spinal deformity (ASD) surgery. This postop impact calls for investigation of unique adjustment of Global Alignment and Proportion (GAP) scores accounting for frailty. This adjustment in spinal proportion may help surgical planning for individualized, optimal postop outcomes. PURPOSE Modify the GAP score with frailty to optimize outcomes in surgical ASD patients. STUDY DESIGN/SETTING Retrospective review of a single-surgeon comprehensive ASD database PATIENT SAMPLE A total of 140 ASD patients OUTCOME MEASURES Frailty-adjusted GAP scores; Health Related Quality of Life scores (HRQLs): ODI, SRS-22 METHODS Surgical ASD patients (SVA≥5cm, PT≥25°, or TK ≥60°, >3 levels fused) ≥18 years old with available baseline (BL) radiographic data were isolated in the single-center Comprehensive Spine Quality Database (Quality). Patients were dichotomized by the ASD frailty index, F (Not Frail, Frail). Linear regression analysis established radiographic equations for frailty-adjusted GAP Scores at baseline and 2-years involving relative pelvic version, relative lumbar lordosis, lordosis distribution index, relative spinopelvic alignment, and an age factor to formulate a sagittal plane score. Patients were restratified into frailty-adjusted proportionality groups: Proportional ( 7). Frailty-adjusted GAP proportionality at 2-years were compared to adjusted-BL to determine whether patients improved, deteriorated or remained the same in their spine proportion. RESULTS A total of 140 patients were included (55.5±16.4 yrs, 77.5% female, 25.2±4.7 kg/m2). BL frailty: 32.8% not frail, 67.2% frail. Primary analyses demonstrated correlation between BL frailty score and BL and 2-year GAP scores(P 33.5%) compared to Proportional (12.8%), p=0.015. SD 2-year patients developed increased PJK at the 1-year mark (40%, Proportional: 13.9%, MD:7.1%, p=0.003), as well as had worse 2-year ODI and SRS-22 satisfaction scores(p CONCLUSIONS Significant associations exist between frailty and spinal proportion. By adjusting the GAP proportionality groups accounting for baseline frailty contributed to improved outcomes and minimized reoperations. The adjusted GAP groups appeal for less rigorous spine proportion goals in severely frail patients. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

P93. The global alignment and proportion (GAP) score needs a modified LDI parameter: creating the GAP-D score

BACKGROUND CONTEXT Proximal Junctional Kyphosis has been a well-known complication following adult spinal deformity correction surgery. The Global Alignment and Proportion (GAP) score was thus developed to predict such mechanical complications following spinal correction surgery. The GAP score is a pelvic-incidence based method of analyzing the sagittal plane. GAP scores of 0∼2 are classified as proportioned, 3∼6 as moderately proportioned, and >=7 as severely disproportioned. GAP parameters include relative pelvic version, relative lumbar lordosis, lordosis distribution index (LDI), age factor of 60, and relative spinopelvic alignment. LDI categories include: 80% receiving a score of 3. PURPOSE The aim of the study was to adjust the LDI parameter in calculation of GAP scores among US adult volunteers with no prior spinal pathology, in order to compensate for high GAP scores in otherwise healthy individuals. STUDY DESIGN/SETTING Retrospective review of prospectively collected data. PATIENT SAMPLE A total of 87 healthy volunteers were included in the study. Mean age was 54.9±15.1 (20-84) years. Exclusion criteria included any major spinal pathology or surgery, terminal illness, morbid obesity, or any significant comorbid condition. OUTCOME MEASURES GAP scores with LDI parameter removed and GAP-D scores. METHODS Preliminary GAP scores with the LDI parameter removed were assessed in 87 healthy volunteers that met inclusion criteria. The preliminary GAP scores were grouped based on the original GAP system's LDI parameters, and these scores were analyzed to search for discrepancies from the baseline trend. Original GAP scores were calculated for the same 87 healthy volunteers. GAP-D scores were calculated with the same parameters as the GAP score, with the exception of the LDI factor. In GAP-D scores, the number of points were subtracted from each LDI group in the same amount that showed discrepancies in the Preliminary GAP score trend. The percentages of Proportioned, Moderately Disproportioned, and Severely Disproportioned volunteers were then compared between the two scoring systems. RESULTS Preliminary GAP scores shows a 1-point and 4-point discrepancy point in the 40∼49% and CONCLUSIONS Our study examined the LDI parameter in calculation of GAP scores in a healthy US population. In this study, we analyzed how the GAP score system may be attributing a high score to otherwise healthy individuals. We found the percentage of proportioned volunteers increases in the Original GAP score by subtractions at the LDI groups 40∼49% and FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

292. Global Alignment and Proportion (GAP) score with modified age factor: GAP-A score

BACKGROUND CONTEXT The Global Alignment and Proportion (GAP) score is a PI-based method of analyzing the sagittal plane, developed to predict the risk of mechanical complications following spinal correction surgery. Our study examined the age factor of 60 as a parameter for GAP score calculation in a healthy US population. Modifying the age factor with score substractions at the cut-offs of age 65 and 70 creates the Global Alignment and Proportion with Modified Age Factor (GAP-A) Score, which better compensates for the sagittal imbalance that occurs naturally with increasing age and affects the healthy elderly population. The GAP score was developed to predict mechanical complications following spinal correction surgery. It is a pelvic-incidence based method of analyzing the sagittal plane. The GAP parameters include relative pelvic version, relative lumbar lordosis, lordosis distribution index, relative spinopelvic alignment (RSA), and an age factor of 60. An age >= 60 years old receives a score of 1, while age PURPOSE The aim of the study was to adjust the age factor in calculation of GAP scores among healthy United States adult volunteers with no prior spinal pathology, in order to compensate for the natural age-related sagittal imbalance among the elderly population. STUDY DESIGN/SETTING Retrospective review of prospectively collected data PATIENT SAMPLE A total of 87 healthy volunteers were included in the study. Mean age was 54.9±15.1 (20-84) years. Exclusion criteria included any major spinal pathology or surgery, terminal illness, morbid obesity or any significant comorbid condition. OUTCOME MEASURES GAP scores with the age factor removed and GAP-A scores. METHODS Preliminary GAP scores with the age factor removed were assessed in 87 healthy volunteers that met inclusion criteria. The preliminary GAP scores were grouped based on age groups in increments of 5 or 10 years, and these scores were analyzed to search for discrepancies from the baseline trend. Original GAP scores were calculated for the same 87 healthy volunteers. GAP-A scores were calculated with the same parameters as the original GAP scores, with the exception of the age factor. In GAP-A scores, in addition to the age factor of adding 1 point if age>60, the number of points were subtracted from each age group in the same amount that showed discrepancies in the Preliminary GAP score trend. The percentages of Proportioned, Moderately Disproportioned, and Severely Disproportioned volunteers were then compared between GAP scores and GAP-A scores. RESULTS Preliminary GAP scores show a 2- and 4-point discrepancy after age 65 and age 70 respectively. After adjustment those two age groups by subtraction of 2 and 4 points from original GAP scores, the percentages of Proportioned and Moderately Disproportioned increased in GAP-A scoring systems. Conversely, Severely Disproportioned groups decreased in GAP-A scoring system. Proportioned volunteers changed from 47.1% to 52.9%, Moderately Disproportioned volunteers changed from 39.1% to 37.9%, and Severely Disproportioned volunteers changed from 13.8% to 9.2% CONCLUSIONS Our study examined the age factor parameter in calculation of GAP scores in a healthy U.S. population. We found proportioned percentage from Original GAP scores increases by subtractions at age cut-offs of 65 and 70, which was the discrepancies found from Preliminary GAP scores. We called this system the Global Alignment and Proportion with Modified Age Factor (GAP-A) scoring system. This system can be proposed as a better alternative in compensating for the natural sagittal imbalance affecting the healthy elderly population. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

P94. Global alignment and proportion (GAP) score with modified RLL parameter: GAP-L score

BACKGROUND CONTEXT The Global Alignment and Proportion (GAP) score was thus developed to predict such mechanical complications following spinal correction surgery. The GAP score is a pelvic-incidence based method of analyzing the sagittal plane. GAP scores of 0∼2 are classified as proportioned, 3∼6 as moderately proportioned, and >=7 as severely disproportioned. GAP parameters include relative pelvic version, relative lumbar lordosis (RLL), lordosis distribution index, age factor of 60, and relative spinopelvic alignment. RLL categories include: 11° receiving a score of 3. PURPOSE The aim of the study was to adjust the RLL parameter in calculation of GAP scores among US adult volunteers with no prior spinal pathology, in order to compensate for high GAP scores in otherwise healthy individuals. STUDY DESIGN/SETTING Retrospective review of prospectively collected data. PATIENT SAMPLE A total of 87 healthy volunteers were included in the study. Mean age was 54.9±15.1 (20-84) years. Exclusion criteria included any major spinal pathology or surgery, terminal illness, morbid obesity, or any significant comorbid condition. OUTCOME MEASURES GAP scores with RSA parameter removed and GAP-L scores. METHODS Preliminary GAP scores with the RLL parameter removed were assessed in 87 healthy volunteers that met inclusion criteria. The preliminary GAP scores were grouped based on the original GAP system's RLL parameters, and these scores were analyzed to search for discrepancies from the baseline trend. Original GAP scores were calculated for the same 87 healthy volunteers. GAP-L scores were calculated with the same parameters as the GAP score, with the exception of the RLL factor. In GAP-L scores, the number of points were subtracted from each RLL group in the same amount that showed discrepancies in the Preliminary GAP score trend. The percentages of Proportioned, Moderately Disproportioned, and Severely Disproportioned volunteers were then compared between the two scoring systems. RESULTS Preliminary GAP scores shows a 3-point discrepancy point in the CONCLUSIONS Our study examined the RLL parameter in calculation of GAP scores in a healthy US population. In this study, we analyzed how the GAP score system may be attributing a high score to otherwise healthy individuals. We found the percentage of proportioned volunteers increases in the Original GAP score by subtractions at RLL group FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.