Pelvic Incidence Group Research Articles

Relationship between sagittal radiographic parameters and disability in patients with spinal disease using 3D standing analysis

PurposeTo clarify the relationship between whole body sagittal radiographic parameters and health related quality of life (HRQOL) in patients with spinal disease, and further analyse such relationship based on the pelvic incidence (PI) value. Methods100 patients (mean age: 64.4 years, M/F=50/50) with lumbar degenerative disease or spinal deformity were prospectively investigated. Following oswestry disability index (ODI) and scoliosis research society score 22 (SRS-22) questionnaire, whole body sagittal x-ray parameters were measured using a slot-scanning 3D x-ray imager (EOS). Correlations between such radiographic parameters and ODI/SRS-22 scores were analysed. Then, patients were divided into three groups based on the PI value (PI≤45°, 45<PI≤60°, and 60<PI), and correlations between the significantly correlated parameters and ODI/SRS-22 scores were analysed for each PI group. ResultsC2-7 lordosis, pelvic tilt (PT), pelvic incidence (PI), PI minus lumbar lordosis (PI-LL), sagittal vertical axis (SVA), full balance integrated index (FBI), and knee flexion angle (KneeFlex) had a significant correlation with ODI or SRS-22 scores. Among those parameters, PI and FBI showed a significant correlation with both ODI and SRS-22 scores. High PI (>60°) group showed a strong correlation (R>0.4) with both ODI and SRS-22 scores for PI-LL parameter. ConclusionsPI and FBI showed a significant correlation with both ODI and SRS-22 scores. PI-LL mismatch was strongly correlated with disability in high PI patients. Our study results may indicate that it is important to pay attention to the PI value in addition to the spinopelvic relationship. Level of evidenceII, prospective study.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters

BACKGROUND CONTEXT Current preoperative planning for surgical adult spinal deformity (ASD) patients takes into account patient age when establishing postoperative alignment targets for sagittal vertical axis (SVA), pelvic tilt (PT) and spino-pelvic-mismatch (PI-LL). Patient height and pelvic incidence (PI), however, have yet to be evaluated for their individual effects on achieving age-adjusted alignment targets. PURPOSE This study assesses the individual effects of patient height and PI on age-adjusted alignment outcomes of surgical ASD patients. STUDY DESIGN/SETTING Single center retrospective review. PATIENT SAMPLE A total of 205 operative ASD patients. OUTCOME MEASURES Postoperative alignment parameters (PT, SVA, PI-LL, and SS); health-related quality of life (HRQL) scores. METHODS Surgical ASD patients >18 years with full-body stereographic x-ray imaging at baseline (BL) and early postoperative follow-up ( 75th) for both BL height and PI. Correction groups were generated at postoperative follow-up for actual alignment compared to age-adjusted ideal values for PT, PI-LL, and SVA, and PI-adjusted ideal alignment values for SS, as derived from clinically relevant formulas. Chi-squared tests assessed differences in rates of matching age-adjusted alignment ideal (±10years threshold for age-adjusted targets; −7° to 5° measured minus ideal for SS target) across height and PI groups. Subanalysis of patients matching age-adjusted alignment ideal used ANOVA to compare clinical outcomes across height and PI groups. RESULTS Included: 205 ASD patients (59±16 year, 64% F, 27±6 kg/m2). Following surgery, patients showed significant improvement in PT, PI-LL and SVA (all p .05). Height groups also did not differ in age or BMI (all p>.05), although female patients comprised a greater proportion of the low (96% F vs. 4% M) and normative (75% F vs. 25% M) height groups (p 0.05). Although there were no differences across PI groups in rates of achieving ideal alignment for PI-LL, SVA or SS (all p>.05), patients with high PI reached age-adjusted ideal alignment for PT at a significantly lower rate (15%) than patients with normative (36%) or low PI (33%, p=.031). Of the 58% of patients that matched any adjusted alignment target in early follow-up, there were no significant differences in postoperative HRQL outcomes across patient height or PI groups (all p>.05). CONCLUSIONS Patients with high pelvic incidence reached ideal postoperative age-adjusted PT alignment at a significantly lower rate than patients with normative and low pelvic incidence. In contrast, patient height had no impact on postoperative age-adjusted alignment outcomes. These results suggest that current postoperative ideal alignment targets may warrant adjustment to account for the morphological factor of pelvic incidence.

The Amount of Proximal Lumbar Lordosis Is Related to Pelvic Incidence.

Given that the pelvis is the pedestal on which the spine lies, its morphology has been observed to be associated with specific sagittal spinal shapes and should therefore be taken into account when dealing with pathologic conditions of the spine. However, the exact relationship between the pelvic morphology and lumbar lordosis still remains poorly defined. We hypothesized that the shape of the lumbar lordosis and its relationship with the pelvis could be described using anatomic parameters, independently of posture. (1) What is the variation of lumbar segmental lordosis in an asymptomatic adult population? (2) Is there an association between increasing magnitude of pelvic incidence (PI) and segmental lordosis? (3) How does the position of the apex of lordosis change with increasing magnitude of PI value? This retrospective study used data drawn from a longitudinally maintained database; between March 2014 and January 2015, 119 asymptomatic volunteers between 18 and 79 years old were enrolled in the study. Mean age was 51 years; there were 81 women and 38 men. Both segmental and cumulative lordosis were measured and used to describe the shape of the lumbar spine. We defined cumulative lordosis as the angle between L1 and S1, proximal lordosis as the angle between L1 and the superior endplate of L4, and distal lordosis as the angle between the superior endplates of L4 and S1. PI is defined as the angle between the line passing through the center of the femoral head and the center of the sacral endplate and a line perpendicular to the sacral endplate. Pearson's correlation was performed to analyze the relationship among PI, proximal and distal lordosis. Stratification by PI was performed (low, < 45°; average, 45°-60°; and high, > 60°) and the proportions of distal and proximal lordosis were then compared using an analysis of variance test. In the whole cohort, proximal lordosis accounted for 38% of total lordosis, whereas distal lordosis accounted for 62%. PI revealed a positive correlation with proximal lordosis (r = 0.546; p < 0.001). However, there was no correlation with distal lordosis (r = 0.087; p = 0.346). Stratification by PI showed that proximal lordosis increased across PI groups (16.6° [± 10] versus 21.6° [± 9] versus 30.1° [± 9]; p < 0.001), whereas distal lordosis remained relatively constant (34.8° [± 8] versus 36.7° [± 7] versus 35.9° [± 10]; p = 0.581). Apex position was overall more proximal as PI increased (r = -0.199; p = 0.034). Our study demonstrated that PI influences only the proximal part of the lordosis, but not the distal part in an asymptomatic adult population. The proximal part of the lumbar spine had the most variability across individuals and appeared to accommodate to pelvic morphology (incidence). Further studies using a larger cohort size are encouraged not only to refine this relationship, but also to investigate the effect of restoration of normal lordotic shape of the lumbar spine on the functional outcomes after spinal fusion. Our findings may be useful for surgical planning in an era of patient-specific care. The findings suggest that surgeons should aim for a patient-specific lumbar shape rather than simple global lordosis matched to the PI.

Analysis of Spino-pelvic Sagittal Alignment in Young Chinese Patients with Lumbar Disc Herniation.

Few studies have concentrated on the sagittal alignment of lumbar disc herniation (LDH), especially the parameters of the pelvis, and controversy exists about whether pelvic morphology is involved in the pathogenesis of LDH. The present study analyzed the characteristics of the sagittal alignment in young Chinese LDH patients and explored the impact of pelvic morphology on the pathogenesis of LDH. A retrospective analysis was conducted on 100 young patients with LDH (69 men and 31 women, aged 18-35 years), and the clinical and imaging findings met the criteria for the diagnosis of LDH. The control group included 100 asymptomatic volunteers with matching age and gender. Coronal and sagittal parameters were measured on the anteroposterior and lateral radiographs of the whole spine, including lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), thoracic kyphosis (TK), and sagittal balance (SVA). The cases were classified into four types by the apex position of lumbar lordosis (type I, L5 or the L4-5 intervertebral space; type II, bottom or middle of L4 ; type III, upper part of L4 or the intervertebral space between L3 and L4 ; type IV, L3 or more high level), and divided into three groups by PI; namely, a low PI group (PI < 40°), a medium PI group (40° ≤ PI < 50°), and a high PI group (PI ≥ 50°). The sagittal parameters, especially PI, were compared between the LDH group and the control group. Correlations between the parameters in the LDH group were analyzed. The PI value of the LDH group was not different from that of the control group (46.1° ± 10.0° vs 47.2° ± 8.8°, P > 0.05). The LDH group showed lower average LL, SS, and TK (P < 0.01), as well as higher PT and SVA compared with the control group (P < 0.01). The LL (34.4° ± 15.3° vs 50.8° ± 10.2°) and SVA (21.6 ± 53.6 mm vs - 18.4 ± 32.8 mm) showed a significant difference (P < 0.01); LL was correlated with PI, SS, PT, TK and SVA (P < 0.01); and SVA was also correlated with the parameters above (P < 0.01) except PI (P > 0.05), and the lordosis apex tended to be higher. The distributions of PI groups between the LDH group and the control group were not different. Pairwise correlations were found among LL, PI, SS, and PT. In addition, TK and SVA were correlated with LL, SS, and PT. There is no difference in PI between young Chinese patients with lumbar disc herniation and the normal population. Young LDH patients may present flat lumbar and thoracic curves, as well as lower sacral slope. The anteversion sagittal imbalance is regulated by both the spine and the pelvis.

Restoration of Lumbar Lordosis in Flat Back Deformity: Optimal Degree of Correction.

Study DesignA retrospective comparative study.PurposeTo provide an ideal correction angle of lumbar lordosis (LL) in degenerative flat back deformity.Overview of LiteratureThe degree of correction in degenerative flat back in relation to pelvic incidence (PI) remains controversial.MethodsForty-nine patients with flat back deformity who underwent corrective surgery were enrolled. Posterior-anterior-posterior sequential operation was performed. Mean age and mean follow-up period was 65.6 years and 24.2 months, respectively. We divided the patients into two groups based on immediate postoperative radiographs-optimal correction (OC) group (PI-9°≤LL<PI+9°) and under-correction (UC) group (LL<PI-9°). We also classified the patients according to the PI of each patient-low PI group (PI<55°) and high PI group (PI≥55°). Radiological and clinical results were analyzed.ResultsPatients in OC group had significantly less correction loss and maintained normal sagittal alignment (sagittal vertical axis<5 cm), as compared to patients in UC group (p<0.05). LL of low PI group significantly maintained within 9° better than high PI group (p<0.05). Oswestry disability index (ODI) significantly decreased at last follow-up, as compared to preoperative state. However, there was no significant difference in last follow-up ODI between the groups.ConclusionsIn flat back deformity, correction of LL to within 9° of PI will result in better sagittal balance. Thus, we recommend sufficient LL to prevent correction loss, especially in patients with high PI.

Radiological analysis of lumbar degenerative kyphosis in relation to pelvic incidence

Lumbar degenerative kyphosis (LDK) is characterized by sagittal imbalance resulting from a loss of lumbar lordosis (LL). The pelvic incidence (PI) regulates the sagittal alignment of the spine and pelvis. The purpose of this study is to evaluate the spinopelvic parameters in patients with LDK and to compare them with those of a normal population. A cross-sectional study. The selected patients showed characteristic clinical features of LDK. As control group, asymptomatic volunteers without spinal pathology were recruited. Full-length radiographs of the spine in the anteroposterior and lateral planes were taken, extending from the base of the skull to the proximal femur. Pelvic incidence, sacral slope (SS), pelvic tilt (PT), main thoracic kyphosis (TK), thoracolumbar junction (TLJ), LL, and sagittal vertical axis (SVA) were evaluated. In terms of PI, the patient and control groups were divided into three groups: low (PI≤45°), middle (45°<PI≤60°), and high PI groups (PI>60°). All the spinopelvic parameters were compared between each group and between the patient and control groups in each group. The correlations between each of the parameters were analyzed. We evaluated 172 patients with symptomatic LDK and 39 healthy volunteers. The number of LDK patients with low, middle, and high PI groups were 44 (25.6%), 72 (44.8%), and 51 (29.6%), respectively. In the control group, the number of low, average, and high PI patients were 18 (46.2%), 15 (38.5%), and 6 (15.4%), respectively. In the control group, PI determined all spinopelvic parameters except SVA. In the LDK group, PI also determined spinopelvic parameters except for TK and SVA. Lumbar degenerative kyphosis with low PI was associated with pronounced kyphosis in LL and TLJ; LDK with a high PI was associated with relatively preserved lordosis in LL with a flat or lordotic TLJ. In terms of pelvic parameters, low PI showed flattened SS and low PT, whereas high PI showed steep SS and high PT. The results of this study suggest the importance of the key anatomical parameter, PI, in the determination of sagittal contour in symptomatic LDK patients and normal population. Spinopelvic parameters and pelvic compensatory mechanisms in LDK patients differ according to PI. Identifying the spinopelvic parameters is useful when correcting deformities.