Spinal-pelvic Parameters Research Articles

Association between back muscle degeneration and spinal-pelvic parameters in patients with degenerative spinal kyphosis

BackgroundThe paraspinal and psoas muscles have been considered to be essentially important for stabilizing the spinal column, and the muscle degeneration was found to exist in degenerative spinal kyphosis (DSK) patients. However, it is still not clear the relationship between muscle degeneration and spinal-pelvic alignment. The purpose of this study was to determine the correlations between the individual muscle degeneration at each lumbar spinal level and spinal-pelvic parameters in DSK patients.MethodsThe imaging data of 32 patients with DSK were retrospectively analyzed. The fat infiltration (FI) and relative cross-sectional area of muscle (RCSA) were quantitatively measured for multifidus (MF), erector spinae (ES) and psoas (PS) at each spinal level from L1/2 to L5/S1. The correlations were analyzed between RCSA and the sagittal vertical axis (SVA), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI).ResultsThe FI of MF and ES at L3/4, L4/5 and L5/S1 were higher than that at L1/2 and L2/3. The FI of PS at L4/5 and L5/S1 were lower than that of L1/2, L2/3 and L3/4. The RCSA of ES and PS from L1/2 to L5/S1 gradually increased, whereas the RCSA of ES from L1/2 to S5/S1 gradually decreased. The RCSA of MF at the L1/2 level was negatively correlated SVA (r = − 0.397,p = 0.024); the RCSA at L3/4, L4/5 and L5/S1 levels were negatively correlated with TK (r = − 0.364, p = 0.04; r = − 0.38, p = 0.032; r = − 0.432, p = 0.014); the RCSA at L4/5 level was positively correlated with LL (r = 0.528, p = 0.002). The RCSA of ES at L3/4 and L4/5 levels were positively correlated with PI (r = 0.377, p = 0.037) and SS (r = 0.420, p = 0.019).ConclusionsFI of MF and ES at lower lumbar level is higher than that at upper level, but FI of PS at upper lumbar level is higher than that at lower level. MF and ES have different roles for maintaining the sagittal spinal-pelvic balance.

Surgical results and sagittal alignment analysis of different fusion levels for degenerative scoliosis

Objective: To retrospectively investigate the effects of long segment fusion and short segment fusion on lumbar sagittal alignment and quality of life in patients with degenerative scoliosis. Methods: From January 2011 to December 2014, 75 patients with degenerative scoliosis were treated with pedicle screw fixation. Total of 56 females and 19 males were included in this study. Fifty-four patients underwent short-segment fusion (≤3 segments) and 21 patients underwent long-segment fusion (>3 segments). The average age of the patients was (63±8) years. The patients were followed-up for a mean time of (2.9±1.3) years. The postoperative follow-up included Cobb angle, pelvic tilt, sacral slope, lumbar lordosis, visual analogue scale of pain on lumbar and lower extremities and Oswestry disability index. Fusion levels, blood loss, surgery length and postoperative hospital stay were recorded. All above parameters were evaluated statistically with Student's t test. Results: The short segment fusion group averaged (1.8±0.7) segments, and the long segment fusion group averaged (5.2±1.6) segments. Coronal Cobb angle changed from (21.3±7.8) degrees preoperatively to (15.3±5.6) degrees at final follow-up in short-segment fusion group (t=2.315, P=0.024) and from (44.5±11.2) degrees preoperatively to (11.4±5.8) degrees at the final follow-up in long-segment fusion group (t=8.214, P<0.01). In the short segment fixation group, the preoperative lumbar lordosis changed from (44.3±9.7) degrees to (48.9±8.2) degrees at final follow-up (t=2.123, P=0.038), and it changed from (25.3±9.5) degrees to (52.1±11.2) degrees in the long segment fusion group (t=5.982, P<0.01). The sacral slope in the short segment fusion group increased from (22.6±6.8) degrees preoperatively to (34.1±7.5) degrees at the final follow-up (t=2.872, P=0.006), and it increased from (12.1±9.5) degrees to (37.8±8.4) degrees in long segment fusion group (t=7.314, P<0.01). The pelvic tilt in the short segment fusion group changed from (23.5±5.5) degrees preoperatively to (19.5±4.7) degrees at final follow-up (t=2.217, P=0.031), and it decreased from (27.1±6.1) degrees to (22.9±4.3) degrees in the long segment fusion group(t=2.131, P=0.045). The visual analogue scale of pain on lumbar and lower extremities and Oswestry disability index were all improved after the operation in both groups. Conclusions: Both short segment fusion and long segment fusion can achieve satisfactory surgical results and improves the spinal-pelvic parameters. Short segment fusion can reduce surgery trauma and shorten hospital stay relative to long segment fixation.

How to restore the proper lumbar lordosis in spine surgery

Sagittal alignment of the spine significantly affects the physical function. In this article, we review the clinical application of several spinal-pelvic parameters, analyze the impact factors of sagittal alignment and provide calculating methods to value the correcting degrees. Spine surgeons should get a deep understanding of the spinal-pelvic parameters, differentiate the functional and structural imbalance. Every patient needs thorough preoperative evaluation to restore the proper alignment during surgery and avoid overcorrection.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P7. Gravity line and sagittal alignment are both risk factors for increased rod stresses in long lumbopelvic fixation: A biomechanics study

BACKGROUND CONTEXT Posterior lumbopelvic fixation with iliac screws is a method that is commonly used for reconstructing the spine. However, clinically significant failure of lumbopelvic fixation (11.9%) and other complications such as pseudoarthrosis (observed in up to 50% of patients with rod failure) are possible, requiring revision surgery. With high rates of implant failure, questions remain regarding mechanical risk factors, or if there is any relationship between implant type, spinopelvic parameters, and failure to achieve fusion. PURPOSE The purpose of this study is to identify if—and to what extent—spinal-pelvic parameters play a role in construct failure using an in silico model. STUDY DESIGN/SETTING Finite element analysis. OUTCOME MEASURES Range of motion, rod stress or strain. METHODS Finite element models (T10-pelvis) were created to match the average spinal-pelvic parameters (pelvic tilt, sacral slope, and lumbar lordosis) of two cohorts of patients reported in the literature, major-failure (defined as pseudoarthrosis or rod fracture above S1) and nonfailure groups. In both groups, vertebral segments were modeled as three-dimensional solid elements. Intervertebral discs were structured as hyperelastic materials. The sacroiliac joint was modeled as articular cartilage contacts surrounded by six types of strong ligaments, depicted as spring elements. Pedicle screws with 5.5 mm diameters were modeled as titanium cylinders (yield strength=795 MPa). A moment load was applied at the T10 superior endplate to simulate gravimetric loading in a standing position. Both nonfailure and major-failure spines had a similar gravity line offset from the heels, as provided by the literature. A model validation was carried out to compare the range of motion of the intact spine unit with the experiments under 10Nm moment in flexion and extension. RESULTS Despite a fixed gravity line position relative to the heels, differences in spinopelvic parameters resulted in a neutral sagittal alignment in the nonfailure spine model, but produced a “sagittal forward” alignment of the major-failure spine model. In order for the latter to maintain sagittal balance, pelvic retroversion was reported and the major-failure spine was translated toward the heel by 10 mm to simulate that. As a result, the bending moment was approximately 17.3 Nm in the nonfailure group and 20.7 Nm in the major-failure group. Differences in loads produced 14 mm translation and 4.9° rotation for the major-failure group—18% and 14% higher, respectively, than in the nonfailure group (11.9 mm translation/4.3° rotation). Rod stresses were highest at L1–L2 and L4–L5. In the major-failure group, maximum stress (138.3 MPa) was observed at the left rod between L4 and L5. In the nonfailure group, maximum stress (115.4 MPa) was at the left rod surface between L1 and L2. High stress (141.0 MPa) was also observed in the right S1 screws in the major-failure group; it was 42% higher than the stress observed in the nonfailure group. CONCLUSIONS Due to compensatory differences in alignment of spinopelvic parameters between normal and failed spines, in the presence of a fixed gravity line, the major failure cohort in this study observed a 20% higher load and 18% greater instability. The higher load and instability further increased loading and mechanical demand on the posterior rods in the lower lumbar spine, further emphasizing the importance of proper sagittal alignment.

The influence of spinal-pelvic parameters on the prevalence of endplate Modic changes in degenerative thoracolumbar/lumbar kyphosis patients.

BackgroundThe typical degeneration of the vertebral endplate shown in MRI imaging is Modic change. The aim of this study was to observe the distribution of the Modic changes of vertebral endplate in degenerative thoracolumbar/lumbar kyphosis (DTK/LK) patients and analyse the correlation between spinal-pelvic parameters and Modic changes.MethodsThe imaging data of 58 patients diagnosed with DTK/LK (coronal Cobb angle<10°with sagittal imbalance) in our hospital from March 2016 to May 2017 were reviewed retrospectively. Observe the prevalence, type and distribution characteristics of Modic changes occurred at the vertebral endplate from T10 to S1;analyse the correlation between Modic changes and disc degeneration, the sagittal vertical axis (SVA), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI).ResultsOf the 928 intervertebral endplates from 58 patients, Modic changes occurred at 90 endplates (9.7%) of 30 patients (51.7%). 5 endplates (0.5%) of 3 patients (5.2%) were classified as type I, 68 endplates (7.3%) of 25 patients (43.1%) as type II, 17 endplates (1.8%) of 9 patients (15.5%) as type III. The location of the degenerative endplates: 2 (2.2%) superior and inferior endplates of L1, 3 (3.3%) inferior endplates of T11and T12, 4 (4.4%) superior endplates of L2, 6 (6.7%) inferior endplates of L2 and L4, 8 (8.9%) superior endplates of S1, 9 (10%) superior endplates of L3, 11 (12.2%) inferior endplates of L3 and L5 and superior endplates of L4, 12 (13.3%) superior endplates of L5. Modic changes were significantly correlated with intervertebral disc degeneration (r = 0.414, p<0.01); the amount of Modic changes were significantly correlated with LL (r = -0.562, p = 0.012), SS (r = -0.46, p = 0.048), PT (r = 0.516, p = 0.024).ConclusionsMost of the Modic changes of vertebral endplates in DTK/LK patients are type II which are prevalently located at L3/4, L4/5 and L5/S1. The Modic changes of vertebral endplates were found to be significantly correlated with disc degeneration, LL, SS, and PT.

SRS-Schwab Grade 4 osteotomy for congenital thoracolumbar kyphosis: a minimum of 2 years follow-up study.

Several osteotomy techniques including pedicle subtraction osteotomy and vertebral column resection have been employed in the correction of congenital kyphosis (CK) and satisfying outcomes have been demonstrated. However, the Scoliosis Research Society (SRS)-Schwab Grade 4 osteotomy, defined as resection of posterior elements, partial vertebral body, and superior adjacent disc, is rarely reported in the treatment of CK. The present study aimed to evaluate the efficiency and safety of SRS-Schwab Grade 4 osteotomy in patients with CK, and to propose its optimal indication. This is a retrospective analysis of clinical and radiographic outcomes of patients with CK undergoing SRS-Schwab Grade 4 osteotomy. Patients with thoracolumbar CK undergoing SRS-Schwab Grade 4 osteotomy from January 2010 to May 2015 followed up for at least 2 years were retrospectively reviewed. The thoracic kyphosis, lumbar lordosis, segmental kyphosis (SK), sagittal vertical axis (SVA), pelvic incidence, pelvic tilt, and sacral slope were measured on lateral spinal x-rays. Patients were required to fulfill the SRS-22 questionnaire at preoperation and the last follow-up. The sagittal spinal-pelvic parameters were assessed at preoperation, postoperation, and last follow-up. The comparison between preoperation and postoperation was performed by paired samples t test. A total of 38 patients with CK (17 male and 21 female) with an average age of 16.5±9.9 years were included. The mean operating time was 242.7±88.1 minutes and blood loss was 634.5±177.8 mL. The mean follow-up was 38.8±20.3 months. The SK was 49.5±11.7° at preoperation, 6.8±7.4° at postoperation (p<.001), and 8.0±8.1° at the last follow-up. No significant correction loss during follow-up was found in SK (p=.125). The SVA was improved from -36.0±18.3 mm at preoperation to 3.7±17.8 mm at postoperation (p<.001), and the correction was well maintained during follow-up (p=.113). Compared with preoperation, the mean postoperative scores of each domains of SRS-22 questionnaire improved at different levels. Intraoperative complications included one case with incidental dural tear and another with transient root injury. Proximal junctional kyphosis occurred in three patients at 6 months after operation and remained stable during the follow-up. At the last follow-up, all patients were identified to have achieved solid bony fusion. The SRS-Schwab Grade 4 osteotomy, if selected appropriately, could provide satisfying correction of congenital kyphosis. The correction could be well maintained during the longitudinal follow-up.

Magnitude, Location, and Factors Related to Regional and Global Correction Loss in Long Adult Deformity Constructs: Report of 183 Patients with 2-Year Follow-Up

Introduction Adult deformity patients (pts) have previously been shown to lose spino-pelvic correction over time especially in the sagittal plane. The goal of this study was to analyze the source of this correction loss and specifically to quantitate the change that occurs in fused verses unfused segments. Variables examined include presence of interbody fusion, rod diameter, rod material, age, and pre-op sagittal alignment. Materials and Methods A retrospective review of a multicenter, prospective ASD database was conducted. Inclusion criteria were age ≥ 18 years, ASD, no revisions between &gt; 6 weeks and &lt; 2 years postop. Spinal pelvic parameters, thoracic kyphosis (TK:T2–T12) and lumbar lordosis (LL:L1–S1) were both measured overall as well as within and outside the instrumented segments. Overall, SVA, PT, Pi-LL change, and TK and LL change between 6 weeks and 2 years post-op was calculated. Of these pts, the amount of TH loss and TL loss within and outside of the instrumented segments was also determined as well as a percentage of the total loss for each region. Results A total of 183 pts met criteria. Between 6 weeks and 2 years post-op 61.7% of pts lost SVA (4.4 ± 4.3 cm), 65.0% lost PT (4.7 ± 4.0 deg), and 40.4% lost PI–LL (16.2 ± 9.3 deg). Overall, 63.9% had TH loss (8.0 ± 8.9 deg) and 56.8% had LL loss (5.8 ± 4.5 deg). Overall, 41.5% lost &gt; 2 cm SVA. Of the pts with &gt; 2 cm SVA loss, 60.5% had LL loss, and of those, 82.6% was within instrumented segments. Of the pts with LL loss, 13.8% had &gt; 10 deg loss. Pts with an interbody fusion have a 2.3 times ( p = 0.0076) likelihood of having any LL loss, but the interbody fusion was protective against &gt; 10 deg change (7.1%). Pts ≥ 65 years' old are 9.4 times ( p &lt; 0.0001) more likely to have LL loss than pts ≤ 45 years' old (4.4%). Pts with pre-op C7 SVA &gt; 5 cm are 2.4 times ( p = 0.0035) more likely to have LL loss. Conclusion Loss of initial regional and global sagittal correction is common in ASD surgery and also occurs inside the instrumented segments between 6 weeks and 2 years postop. Older age and pre-op sagittal deformity are risk factors for overall loss of correction and for loss of correction within the instrumented segments. In our study, interbody fusion was only protective for LL loss &gt; 10 deg.

A Report of 41 Cases of Three-Column Osteotomies of the Upper Thoracic Spine and Cervicothoracic Junction: Complications, Outcomes and Differential Impact on Spinal Pelvic Parameters, Cervical Sagittal Alignment and General Health Status

Vertebral column resection (VCR) and pedicle subtraction osteotomies (PSO) are most commonly performed at or below the mid thoracic apex to lower lumbar spine. Evidence regarding three-column osteotomies of the upper thoracic spine and cervicothoracic junction are limited.