Change In Pelvic Incidence Research Articles

P231. Change in pelvic incidence following primary sacroiliac joint fusion

P231. Change in pelvic incidence following primary sacroiliac joint fusion

Response to the Letter to the Editor Regarding: "Can Pelvic Incidence Change After Lumbo-Pelvic Fixation for Adult Spine Deformity and Would the Change be Affected by the Type of Pelvic Fixation?"

Response to the Letter to the Editor Regarding: "Can Pelvic Incidence Change After Lumbo-Pelvic Fixation for Adult Spine Deformity and Would the Change be Affected by the Type of Pelvic Fixation?"

Letter to the Editor Regarding "Can Pelvic Incidence Change After Lumbo-Pelvic Fixation for Adult Spine Deformity and Would the Change be Affected by the Type of Pelvic Fixation?"

Letter to the Editor Regarding "Can Pelvic Incidence Change After Lumbo-Pelvic Fixation for Adult Spine Deformity and Would the Change be Affected by the Type of Pelvic Fixation?"

Can Pelvic Incidence Change After Lumbo-Pelvic Fixation for Adult Spine Deformity and Would the Change Be Affected By the Type of Pelvic Fixation?

Retrospective review. To assess the change in pelvic incidence (PI) after lumbo-pelvic fixation and the differential impact of the type of pelvic fixation: S2-alar-iliac screws(S2AI) versus Iliac screws(IS) on post-operative PI. Recent studies suggest that changes occur to the previously assumed fixed PI after spino-pelvic fixation. Adult spine deformity(ASD) patients who underwent spino-pelvic fixation with≥4 levels fusion were included. Pre-operative and post-operative PI, lumbar lordosis(LL), thoracic kyphosis(TK), pelvic tilt(PT), sacral slope(SS), PI-LL mismatch and the Sagittal Vertical Axis(SVA) were analyzed on EOS imaging. A significant PI change was established at≥6⁰. Patients were categorized based on the type of pelvic fixation (S2AI vs. IS). One-hundred-forty-nine patients were included. Of these, 77(52%) had a>6⁰ change in their PI post-operatively. In patients with high pre-operative PI (>60⁰), 62% had a significant PI change compared to 33% of patients with normal PI (40⁰-60⁰) and 53% in patients with low PI(<40⁰; P=0.01). PI was likely to decrease in patients with high baseline PI (>60⁰) and to increase in patients with low baseline PI (<40⁰). Patients with a significant PI change had a higher PI-LL. Patients in the S2AI group (n=99) and those in the IS group (n=50) were comparable at baseline. In the S2AI group, 50 (51%) patients had>6⁰ change in their PI compared to 27(54%) patients in the IS group(P=0.65). In both groups, patients with high pre-operative PI were more prone to significant post-operative changes (P=0.02 in IS, P=0.01 in S2AI). PI changed significantly in 50% of patients post-operatively, especially in those with high/low pre-operative PI and those with severe baseline sagittal imbalance. This occurs similarly in patients with S2AI and those with IS screws. Surgeons should keep in mind these anticipated changes while planning ideal LL, as this impacts post-operative PI-LL mismatch. IV.

Special type of distal junctional failure exhibits pelvic incidence changes: sacroiliac joint-related pain following lumbar spine surgery

BackgroundCurrently, change in pelvic incidence (PI) in patients after spinal surgery have not been associated with clear clinical symptoms. This study sought to compare changes in the sagittal parameters of different patients before and after thoracolumbar spine surgery, the relationship between PI change and sacroiliac joint pain (SIJP) after surgery was clarified, and the correlation between PI change and sacroiliac joint (SIJ) activity was verified.MethodsThis study retrospectively analyzed the data of patients who underwent thoracolumbar fusion at Sun Yat-sen Memorial Hospital from January 2019 to June 2021. The spinal and pelvic parameters [including pelvic tilt (PT), sacral slope (SS), PI, lumbar lordosis (LL) angle, etc.] of 409 patients with standard standing lateral radiographs before and after surgery were compared and analyzed. Postoperative follow-up of all patients with standardized SIJP assessment. The incidence of postoperative SIJP, and its correlation with sagittal parameters of the spine and pelvis, surgical methods, and the basic characteristics of patients were analyzed. The Chi-square test was used for categorical variables, the independent-sample t-test was used for generally conformed normally distributed continuous variables. Risk factors associated with the development of SIJP were analyzed using logistics regression. Correlations among SS, PI, and the 4 other sagittal parameters were analyzed using the Pearson correlation coefficient (r).ResultsPostoperative PI changes tended to be larger in the lowest instrumented vertebra (LIV) (L4 and above: 1.63°; L5: 2.43°; S1: 3.83°; P<0.05) and longer fixed segment. The risk factors for SIJP included a PI >4° [odds ratio (OR) =13.051; P<0.001], LIV S1 (OR =3.378; P=0.023), and fixed total segment ≥3 (OR =2.632; P=0.038). ∆PI was significantly correlated with ∆SS in patients with non-S1 distal fixation vertebrae (R2=0.388; P<0.01), but no such correlation was found in patients with S1 distal fixation vertebrate.ConclusionsChanges in PI values after thoracolumbar spine surgery can correctly reflect the motion state of the SIJ. Excessive changes in PI (>4°) are similar to the mechanism of distal junctional kyphosis (DJK), while such changes make patients prone to SIJP following lumbar spine surgery.

Sagittal Plane Mobility in Adolsents with Femoroacetabular Impingment

Background:Femoroacetabular impingement (FAI) is a dynamic degradative condition of the hip joint characterized by classic physical exam findings in combination with abnormal radiographs and/or MRI. Although this abnormal morphologic relationship contributes to FAI, the role of physical therapy to mitigate symptoms by improving strength and mobility of the hip remains the first line treatment. Despite this common treatment algorithm, limited knowledge exists on the effects of sagittal balance, lumbopelvic mobility, and its role in the development of treatment for symptomatic FAI.Hypothesis/Purpose:To review lumbopelvic mobility from standing to sitting position in adolescent athletes who present with clinical signs of FAI.Methods:Pelvic radiographic measurements in the sagittal plane were performed on a retrospective series of consecutive patients who presented with clinical diagnosis of FAI at a pediatric sports medicine institution from April 2019-March 2021. Standardized EOS dynamic lateral pelvic images were performed in standing and sitting positions to evaluate the differences in sacral slope, pelvic tilt, and pelvic incidence. Data from bi-positional radiographs were combined with standard measurements for FAI obtained on AP pelvis (lateral center edge angle, acetabular inclination) and 45 degree Dunn views (alpha angle), and patient reported outcomes (PROs) (mHHS, HOOS, UCLA). Differences in sacral slope from pre-treatment radiographs were used to determine comparison groups: those with a change vs. those with limited change between a sitting and standing position.Results:76 adolescent patients (mean age 15.7 years [12-24]; 71.5% females) with sitting/standing lateral pelvis radiographs and a clinical diagnosis of FAI were identified. Between sitting and standing positions, there was no change in pelvic incidence, while significant differences were noted in sacral slopes and pelvic tilt (Table 1). Variability in sacral slope differences between sitting and standing were identified with 10 (13.9%) patients having minimal (<10o) change, while 8 (11.1%) demonstrated changes > 40o (Figure 1). Adolescent patients with FAI who demonstrated more mobility from sitting to standing position had a higher sacral slope in the standing position. No correlations were noted between pelvic incidence or sacral slope and radiographic measures associated with FAI, PROs or differences in those with variable changes in sacral slope from sitting to standing position.Conclusion:Lateral pelvic imaging may be an important tool for understanding dynamic hip impingement. In adolescent patients signs and symptoms with clinical FAI, significant variability exists in lumbopelvic mechanics, regardless of the severity of radiographic values.Table 1.Radiographic measurements performed on a sitting and standing lateral pelvic radiographs using EOS. Values listed are mean (standard deviation; range).Figure 1.Sitting and Standing lateral pelvic images from 2 patients. Top row: Standing lateral pelvis (A) and sitting lateral pelvis (B) with a significant change in sacral angle and pelvic tilt with no changes in pelvic incidence. Not the change in lumbar lordosis in this patient. Bottom row: Standing lateral pelvic (A) and sitting lateral pelvic (B) without significant change in lumbosacral position.

Pelvic incidence change on the operating table.

While a change in the pelvic incidence (PI) after long spine fusion surgery has been reported, no studies have examined the change in the PI on the operating table. The present study examined the PI-change on the operating table and elucidated the patients' background characteristics associated with this phenomenon. This study included patients who underwent lumbar posterior spine surgery and had radiographs taken in a full-standing position preoperatively and a pelvic lateral radiograph in the prone position in the operative room. The patients with PI-change on the operating table (PICOT; PICOT group) and without PICOT (control group) were compared for their background characteristics and preoperative radiographic parameters. There were 128 eligible patients (62 males, 66 females) with a mean age (± standard deviation) of 69.9 ± 11.7 (range: 25-93) years old. Sixteen patients (12.5%) showed a decrease in the PI > 10°, which indicated placement in the PICOT group. The preoperative lumbar lordosis (LL) and PI-LL in the PICOT group were significantly worse than those in the control group (LL: 20.8 ± 16.6 vs. 30.6 ± 16.2, p = 0.0251, PI-LL: 33.9 ± 19.0 vs. 17.3 ± 14.8, p < 0.0001). The PICOT group had a higher proportion of patients who underwent fusion surgery than the control group, but the difference was not significant (62.5% vs. 44.6%, p = 0.1799). A decreased PI was observed in some patients who underwent lumbar posterior surgery on the operating table before surgery. Patients with a PI decrease on the operating table had a significantly worse preoperative global alignment than those without such a decrease. Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

Use of iliac screw associated with more correction of lumbar lordosis than S2-alar-iliac screw for adult spinal deformity

BackgroundTo date, there is a paucity of reports clarifying the change of spinopelvic parameters in patients with adult spinal deformity (ASD) who underwent long segment spinal fusion using iliac screw (IS) and S2-alar-iliac screw (S2AI) fixation.MethodsA retrospective review of consecutive patients who underwent deformity correction surgery for ASD between 2013 and 2017 was performed. Patients were divided into two groups based on whether IS or S2AI fixation was performed. All radiographic parameters were measured preoperatively, immediately postoperatively, and the last follow-up. Demographics, intraoperative and clinical data were analyzed between the two groups. Additionally, the cohort was subdivided according to the postoperative change in pelvic incidence (PI): subgroup (C) was defined as change in PI ≥5° and subgroup (NC) with change < 5°. In subgroup analyses, the 2 different types of postoperative change of PI were directly compared.ResultsA total of 142 patients met inclusion criteria: 111 who received IS and 31 received S2AI fixation. The IS group (65.6 ± 26°, 39.8 ± 13.8°) showed a significantly higher change in lumbar lordosis (LL) and upper lumbar lordosis (ULL) than the S2AI group (54.4 ± 17.9°, 30.3 ± 9.9°) (p < 0.05). In subgroup (C), PI significantly increased from 53° preoperatively to 59° postoperatively at least 50% of IS cohort, with a mean change of 5.8° (p < 0.05). The clinical outcomes at the last follow-up were significantly better in IS group than in S2AI group in terms of VAS scores for back and leg. The occurrence of sacroiliac joint pain and pelvic screw fracture were significantly greater in S2AI group than in IS group (25.8% vs 9%, p < 0.05) and (16.1% vs 3.6%, p < 0.05).ConclusionsCompared with the S2AI technique, the IS technique usable larger cantilever force demonstrated more correction of lumbar lordosis, and possible increase in pelvic incidence. Further study is warranted to clarify the clinical impaction of these results.

Use of rhBMP-2 for adult spinal deformity surgery: patterns of usage and changes over the past decade.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been shown to increase fusion rates; however, cost, limited FDA approval, and possible complications impact its use. Decisions regarding rhBMP-2 use and changes over time have not been well defined. In this study, the authors aimed to assess changes in rhBMP-2 use for adult spinal deformity (ASD) surgery over the past decade. A retrospective review of the International Spine Study Group prospective multicenter database was performed to identify ASD patients treated surgically from 2008 to 2018. For assessment of rhBMP-2 use over time, 3 periods were created: 2008-2011, 2012-2015, and 2016-2018. Of the patients identified, 1180 met inclusion criteria, with a mean age 60 years and 30% of patients requiring revision surgery; rhBMP-2 was used in 73.9% of patients overall. The mean rhBMP-2 dose per patient was 23.6 mg. Patients receiving rhBMP-2 were older (61 vs 58 years, p < 0.001) and had more comorbidities (Charlson Comorbidity Index 1.9 vs 1.4, p < 0.001), a higher rate of the Scoliosis Research Society-Schwab pelvic tilt modifier (> 0; 68% vs 62%, p = 0.026), a greater deformity correction (change in pelvic incidence minus lumbar lordosis 15° vs 12°, p = 0.01), and more levels fused (8.9 vs 7.9, p = 0.003). Over the 3 time periods, the overall rate of rhBMP-2 use increased and then stabilized (62.5% vs 79% vs 77%). Stratified analysis showed that after an overall increase in rhBMP-2 use, only patients who were younger than 50 years, those who were smokers, those who received a three-column osteotomy (3CO), and patients who underwent revision sustained an increased rate of rhBMP-2 use between the later two periods. No similar increases were noted for older patients, nonsmokers, primary surgery patients, and patients without a 3CO. The total rhBMP-2 dose decreased over time (26.6 mg vs 24.8 mg vs 20.7 mg, p < 0.001). After matching patients by preoperative alignment, 215 patients were included, and a significantly lower rate of complications leading to revision surgery was observed within the 2012-2015 period compared with the 2008-2011 (21.4% vs 13.0%, p = 0.029) period, while rhBMP-2 was increasingly used (80.5% vs 66.0%, p = 0.001). There was a trend toward a lower rate of pseudarthrosis for patients in the 2012-2015 period, but this difference did not reach statistical significance (7% vs 4.2%, p = 0.283). The authors found that rhBMP-2 was used in the majority of ASD patients and was more commonly used in those with greater deformity correction. Additionally, over the last 10 years, rhBMP-2 was increasingly used for ASD patients, but the dose has decreased.

Change in pelvic incidence between the supine and standing positions in patients with bilateral sacroiliac joint vacuum signs.

Pelvic incidence (PI) is a commonly utilized spinopelvic parameter in the evaluation and treatment of patients with spinal deformity and is believed to be a fixed parameter. However, a fixed PI assumes that there is no motion across the sacroiliac (SI) joint, which has been disputed in recent literature. The objective of this study was to determine if patients with SI joint vacuum sign have a change in PI between the supine and standing positions. A retrospective chart review identified patients with a standing radiograph, supine radiograph, and CT scan encompassing the SI joints within a 6-month period. Patients were grouped according to their SI joints having either no vacuum sign, unilateral vacuum sign, or bilateral vacuum sign. PI was measured by two independent reviewers. Seventy-three patients were identified with an average age of 66 years and a BMI of 30 kg/m2. Patients with bilateral SI joint vacuum sign (n = 27) had an average absolute change in PI of 7.2° (p < 0.0001) between the standing and supine positions compared to patients with unilateral SI joint vacuum sign (n = 20) who had a change of 5.2° (p = 0.0008), and patients without an SI joint vacuum sign (n = 26) who experienced a change of 4.1° (p = 0.74). ANOVA with post hoc Tukey test showed a statistically significant difference in the change in PI between patients with the bilateral SI joint vacuum sign and those without an SI joint vacuum sign (p = 0.023). The intraclass correlation coefficient between the two reviewers was 0.97 for standing PI and 0.96 for supine PI (p < 0.0001). Patients with bilateral SI joint vacuum signs had a change in PI between the standing and supine positions, suggesting there may be increasing motion across the SI joint with significant joint degeneration.

Movement of the sacroiliac joint: Anatomy, systematic review, and biomechanical considerations.

Several researchers investigated the anatomy and biomechanics of the sacroiliac joint (SIJ) to understand the relationship between lower back pain and the SIJ. Many studies concluded that the SIJ has little movement; however, some studies using spinopelvic parameters mentioned high change in pelvic incidence (PI). In this study, SIJ movement and PI change reported in previous studies were reviewed according to position and posture changes. Literature on SIJ movement was reviewed by searching through the publication databases. In biomechanical studies, the result of the rotational angle in the sagittal plane was mainly investigated to compare with the results of PI change. From the results of SIJ movement studies, the minimum movement of nutation and count-nutation was 0.01°, and maximum movement was 2.27°. From the results of PI change studies with different positions and movements, the highest change was 9°, and the lowest change was 0°. Movement of the SIJ was limited by its anatomical structure; maximum movement of the SIJ was 9° in a previous study. Therefore, SIJ movement should be studied more intensely as biomechanical perspective to understand its movement.

Can pelvic incidence change after spinal deformity correction to the pelvis with S2-alar-iliac screws?

Pelvic incidence (PI) is assumed to be fixed, yet studies have reported PI changes after long fusions to the pelvis. In a cohort of ASD patients undergoing surgery with S2-alar-iliac (S2AI) screws, we sought to: (1) report the magnitude of PI changes, and (2) evaluate subsequent pelvic parameter changes. A retrospective case series of ASD patients undergoing surgical correction with S2AI screw placement and sagittal cantilever correction maneuvers was conducted. Patients were categorized based on preoperative PI: High-PI (H-PI) (PI≥60°); Normal-PI (N-PI) (60°>PI>40°); Low-PI (L-PI) (PI≤40°). PI was measured preoperatively and immediately postoperatively. A significant PI change was established a priori at ≥6.0. PI, pelvic tilt (PT), lumbar lordosis (LL), and PI-LL mismatch were analyzed. In 68 patients (82.3% female, ages 22-75years), the average change in PI was 4.6°±3.1, and 25 (36.8%) had a PI change ≥6.0° with breakdown as follows: H-PI 12 (66.7%) patients, 9 (25.87%) patients, and 4 (33.3%) patients. Of 25 patients with PI changes, 10 (14.7%) had a PI increase and 15 (22.1%) had a PI decrease. Significant improvements were seen in PT, LL, PI-LL mismatch in all patients with a PI change ≥6.0°, in addition to both subgroups with an increase or decrease in PI. PI changes of ≥6.0° occurred in 36.8% of patients, and H-PI patients most commonly experienced PI changes. Despite PI alterations, pelvic parameters significantly improved postoperatively. These results may be explained by sacroiliac joint laxity, S2AI screwplacement, or aggressive sagittal cantilever techniques.

Loss of Pelvic Incidence Correction After Long Fusion Using Iliac Screws for Adult Spinal Deformity: Cause and Effect on Clinical Outcome.

Retrospective observational cohort study. To determine change in pelvic incidence (PI) and loss of correction after long fusion with iliac screws, the effect of iliac screw loosening, and global alignment according to postoperative PI. Posterior long fixation and fusion of the thoracic to the ilium is one of the most common surgical treatments for adult spinal deformity (ASD). Long fusion to the sacrum with iliac screws decreases the PI by 3.9° after surgery. PI decreases once by long fusion with iliac screws. However, if the iliac screw loosens, PI may cause correction loss and return to the preoperative PI. We retrospectively reviewed the cases of 69 consecutive patients with ASD. Their mean age (SD) was 70.5 (7.3) years, 12% were male. PI was evaluated preoperatively, early- and 1-year postoperatively. We compared change in PI with and without loosening of iliac screws, spinopelvic parameters according to 1-year-postoperative PI. PI decreased significantly from 51.8° (9.3°) to 48.1° (9.5°) early postoperatively (P < 0.01). PI increased significantly from 48.1° (9.5°) to 49.6° (9.7°) within a year postoperatively (P < 0.01). Significant loss of PI correction (2.3°, P < 0.01) occurred within a year after surgery in patients with iliac screw loosening and was significantly different from the PI loss in those without screw loosening (53.9°, 48.2°, P = 0.03). Pelvic tilt, sacral slope, C7 sagittal vertical axis, global tilt, and T1 pelvic angle were significantly smaller in the group with PI <50° postoperatively at 1 year compared with the group with PI >50°. Although PI decreases after long fusion surgery with iliac screws, significant correction loss appears within a year. Loosening of iliac screws may exacerbate this loss. Patients with PI <50° postoperatively were able to maintain better global alignment. 3.

Effect of long spinal fusion including the pelvis on activities of daily living related to lumbar spinal function in adults with spinal deformity

BackgroundSpinal sagittal malalignment is managed by long spinal fusion including the pelvis, which reduces lumbar spine range of motion and impairs the activities of daily living. This study aimed to evaluate the changes in activities of daily living after long spinal fusion in adults with spinal deformity, and clarify the improvement or deterioration in the specific activities of daily living postoperatively. MethodsWe retrospectively reviewed 40 adults who underwent long spinal fusion in a single institution between 2014 and 2016 (female/male, 39/1; mean age, 68.5 years; range, 52–79 years). Each patient undertook three self-assessed health-related quality of life measures preoperatively and again at 2-years postoperatively: Oswestry Disability Index (ODI), Scoliosis Research Society (SRS)-22 questionnaire, and Japanese Orthopaedic Association back pain evaluation questionnaire (JOABPEQ). Radiographic outcomes were measured preoperatively and at 2 years postoperatively. ResultsTotal ODI and all SRS-22 domains were improved at 2 years postoperatively. The JOABPEQ scores were also improved in all domains, except lumbar function. The change in pelvic incidence minus lumbar lordosis correlated with improvements in total ODI, SRS-22 function, and self-image scores. At 2 years postoperatively, satisfaction was correlated with total ODI, all SRS-22 domains, and the JOABPEQ pain domain. Subclass analysis of the JOABPEQ lumbar function domain at 2 years postoperatively revealed that 65% of patients had difficulty ‘putting on socks or stockings’, 42% had great difficulty ‘bending forward, kneeling, or stooping’, 32% reported improvement in ‘sit to stand’, and 32% reported deterioration in ‘putting on socks or stockings’ after surgery compared with before surgery. The JOABPEQ lumbar function domain was not correlated with the SRS-22 satisfaction domain. ConclusionsDespite restricting lumbar function, spinopelvic fusion improves health-related quality of life. Surgeons and patients should discuss potential changes and limitations in the activities of daily living after long spinal fusion including the pelvis.

Comparison Between S2-Alar-Iliac Screw Fixation and Iliac Screw Fixation in Adult Deformity Surgery: Reoperation Rates and Spinopelvic Parameters.

Study Design:Retrospective cohort study.Objective:The S2-alar-iliac (S2AI) technique has been described as an alternative method for pelvic fixation in place of iliac screws (ISs) in spinal deformity surgery. The objective of this study was to analyze the impact of S2AI screws on radiographical outcomes, including spinopelvic parameters.Methods:A retrospective review of 17 patients receiving ISs and 46 patients receiving S2AI screws for correction of adult spinal deformity between 2010 and 2015 with minimum 1-year follow-up was conducted. Patient data on postoperative complications, including reoperation rates and proximal junctional kyphosis (PJK), and radiographical parameters was collected and statistically analyzed.Results:With mean follow-up of 21.1 months, the overall reoperation rate was significantly lower in the S2AI group than in the IS group (21.7% vs 58.8%, P = .01), but the incidence of PJK was similar (32.6% vs 35.3%, P > .99). Moreover, the time to reoperation in the IS group was significantly shorter than in the S2AI group (P = .001), and the S2AI group trended toward a longer time to reoperation due to PJK (P = .08). There was a significantly higher change in pelvic incidence (PI) in the S2AI group (−6.0°) compared with the IS group (P = .001).Conclusions:Compared with the IS technique, the S2AI technique demonstrated a lower rate of overall reoperation, a similar rate of PJK, longer time to reoperation, and possible reduction in PI. Future studies may be warranted to clarify the mechanism of these results and how they can be translated into improved patient care.

Global Sagittal Imbalance Due to Change in Pelvic Incidence After Traumatic Spinopelvic Dissociation.

To examine how spinopelvic morphology changes after traumatic spinopelvic dissociation and whether these changes affect the sagittal balance of the spine. Retrospective analysis. Level I trauma center. Thirty-nine consecutive patients who were diagnosed with traumatic spinopelvic dissociation and had a minimum 2-year radiological follow-up were included. Nineteen patients underwent spinopelvic pedicle screw fixation, 11 patients underwent percutaneous iliosacral screw fixation, and 9 patients were treated conservatively. The main outcome measurements are as follows: (1) injury morphology (injury type and kyphotic angulation) at the initial and follow-up visits; (2) sagittal vertical axis (SVA) at the 2-year follow-up; (3) spinopelvic parameters [pelvic incidence (PI), sacral slope, pelvic tilt, lumbar lordosis, and thoracic kyphosis] at the 2-year follow-up; and (4) bodily pain and Oswestry Disability Index at the 2-year follow-up. There were 21 men and 18 women, with a mean age of 28.3 years (15-62 years). At the 2-year follow-up, the mean SVA was 5.4 ± 4.1 cm and the mean PI was 76.9 ± 24.6 degrees. Factors related to SVA after traumatic spinopelvic dissociation were PI (r = 0.441, P = 0.017), pelvic tilt (r = 0.387, P = 0.038), and injury type of complete displacement (r = 0.372, P = 0.047). The bodily pain and Oswestry Disability Index was significantly poorer in patients with SVA modifier "+" than in patients with SVA modifier "0." Lumbosacral kyphosis after traumatic spinopelvic dissociation increases PI, which can affect the sagittal balance of the spine and clinical outcome. Restoration of lumbosacral orientation is important for preventing sagittal imbalance. Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Change in Pelvic Sagittal Parameters with Growth in Children with Adolescent Scoliosis

Introduction Commonly measured spinopelvic parameters (pelvic incidence, sacral slope, and pelvic tilt) have an effect on global sagittal balance of the spine. It was shown previously by cross-sectional studies that pelvic incidence increases with growth in children. But this change was not demonstrated in longitudinal radiological follow-up studies. In this study, we aimed to investigate the changes in spinopelvic parameters with growth in surgically treated AIS patients. Methods Whole body lateral radiographs eligible for spinopelvic measurements with radiological follow-up before and after skeletal maturity of AIS patients treated surgically were evaluated. First evaluations are made on preoperative radiographs of AIS patients (Risser O or 1). Second evaluations were made on postoperative radiographs taken after skeletal maturity (Risser 5). On whole body lateral radiographs pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis between L1 cranial endplate and S1 endplate (LL), and thoracic kyphosis between cranial endplate of T5 and caudal endplate of T12 (TK) were performed using Centricity DICOM software (General Electric). Measurements were made by two observers. Intra- and interobserver reliabilities were also evaluated by repeat measurements. Intra- and interobserver reliabilities for measurements were evaluated by intraclass correlation (ICC). Results A total of 171 surgically treated cases for AIS were reviewed. Of them, 33 cases had radiological follow-up data before and after skeletal maturity with lateral X-rays eligible for spinopelvic parameters measurement. Mean interval between evaluations was 7.49 years. Intra- and interobserver reliabilities for measurements were accepted as “good” with ICC values between 0.951 and 0.989. A significant increase in PI and SS was observed before and after skeletal maturity (46.32 ± 11.61 vs. 52.14 ± 11.69 degrees and 38.14 ± 7.57 vs. 43.19 ± 7.46 degrees, respectively). Increase in LL was also statistically significant and correlated with PI (53.38 ± 9.53 vs. 61.92 ± 10.48 degrees). Changes in TK and PT were not significant. Conclusions Results were concordant with previous cross-sectional and anthropometric studies regarding increase in pelvic incidence by growth. It is also concluded that overall lumbar lordosis is influenced by pelvic incidence both before and after skeletal maturity. As thoracic kyphosis is mainly influenced by instrumentation, no significant difference and relation with spinopelvic parameters were encountered. As reported previously, sagittal profile changes are well tolerated in adolescents, there was no major change in PT. But concerning long fusions, change in pelvic incidence and sacral slope can have a substantial effect on long sagittal profile of surgical candidates.

A New Method for Calculating the Exact Angle Required for Spinal Osteotomy

Prospective study. To assess a new method for determining the exact angle required for spinal osteotomy in patients with ankylosing spondylitis (AS). The ideal method for maintaining sagittal balance is to shift the center of gravity of the trunk over the hip axis when pelvic and lower extremity joints are in the neutral position. For patients with AS, various methods have been explored to calculate the required corrective angle. However, these methods carry some limitations. Twenty patients with AS who underwent spinal osteotomy for correcting kyphotic deformity were studied. Pre- and postoperative full-length freestanding radiographs of the whole spine and pelvis were obtained for all patients. We calculated the ideal postoperative pelvic tilt according to pelvic incidence, and chose the plumbline of the hilus pulmonis rather than C7 as gravity axis of the trunk. Then, the necessary angular correction at the level of osteotomy was calculated. Pre- and postoperative radiological parameters, including Cobb T1-S1, pelvic incidence, pelvic tilt, sacral slope, and sagittal vertical axis were measured. Health related quality of life, including Oswestry Disability Index and Scoliosis Research Society outcomes instrument-22, were administered before surgery and at 6-month follow-up. The preoperative and postoperative Cobb T1-S1 were 52° and 3°, respectively (P < 0.001). All patients demonstrated changes in preoperative to postoperative radiographical parameters including decreased pelvic tilt (from 30° to 11°, P < 0.001) and sagittal vertical axis (from 18 cm to 7 cm), increased sacral slope (from 16° to 35°, P < 0.001), but no significant change in pelvic incidence. Health related quality of life scores at 6-month follow-up had significantly improved compared with those before surgery. This method provides an accurate and reproducible calculation for AS correction. 2.